11 Molecutes (8); Obligate Intracellular Bacteria (16); & Spirochetes (14); total of 38 cards

Question 1

Case
A 50-year-old man presents with a 3-week history of diffuse pain, stiffness, and swelling of his right knee. He lives near a wooded area and was bitten by a tick 7 months earlier; he developed a local skin lesion at the site of the tick bite, followed by flu-like symptoms. He recovered without any specific treatment. Radiography of the knee joint shows evidence of effusion. Arthrocentesis yields inflammatory fluid.

What test is recommended for confirming the diagnosis?

1 Microscopy of the synovial fluid
2 Culture of the synovial fluid
3 PCR analysis of the synovial fluid
4 Blood culture
5 Testing for serum antibodies

Answer 1

Testing for serum antibodies

sting for serum antibodies helps to confirm a clinical diagnosis of Lyme disease. Lyme arthritis is one of the common manifestations of Lyme disease, a multi-system disease caused by Borrelia burgdorferi and a few other Borrelia species of spirochetes. In the United States, Lyme disease is the most common vector-borne disease caused by B. burgdorferi. The main vector is Ixodes scapularis, a deer tick. Human infections follow as a result of a bite from adult or nymphal ticks infected with the spirochete. The incidence of Lyme disease is reported to be on the increase in several states in the United States.
Serological testing for B. burgdorferi antibodies is indicated for a diagnosis in patients with a characteristic clinical picture of Lyme disease, except in those with erythema migrans; antibodies may not be at a detectable level. To improve the accuracy of serological testing, two-tier testing is recommended. Detection of IgG antibodies against B. burgdorferi by this method helps to confirm the diagnosis of Lyme arthritis. Serum is tested first by enzyme-linked immunosorbent assay (ELISA); if the result is positive or equivocal, it is tested by a more specific Western blot to corroborate the result of the first test. If the ELISA test is negative, no further testing is indicated.
The detection of B. burgdorferi antibodies in synovial fluid is of diagnostic significance. B. burgdorferi in fluid culture media can be observed as highly motile bacteria by dark-field and phase-contrast microscopy. Preparations stained by silver stains or fluorescent dyes can be visualized using light microscopy, but the utility of microscopic assay for the confirmation of Lyme arthritis is limited (due to the sparseness of the bacteria in clinical samples).
Barbour-Stoenner-Kelly medium (BSK II), a complex liquid medium, is used for culturing B. burgdorferi, although rarely has the bacterium been isolated from synovial fluid. The bacterium is a slow-grower and requires prolonged incubation (up to 12 weeks) before the culture can be considered negative. Culture is mostly done for research studies, and not as a routine diagnostic test in clinical practice.
B. burgdorferi DNA can be detected in the synovial fluid by a polymerase chain reaction (PCR); it has about 90% sensitivity and is more sensitive than a culture. Potential false positivity, due to contamination of the sample, is considered as a drawback for PCR assays. The test is not yet standardized and not recommended for routine diagnostic use.
Blood culture samples are only rarely positive, even in early Lyme disease (erythema migrans) and in patients with systemic symptoms of dissemination. Recent studies have shown better recovery of B. burgdorferi by culturing enough plasma from untreated patients with erythema migrans. Blood culture is not indicated for diagnosing Lyme arthritis.

Question 2

Case
A 45-year-old man presents with a 3-week history of fever, malaise, and cough. The illness began with a low-grade fever, headache, sore throat, and non-productive cough. He tried symptomatic treatment with OTC medicines, no antibiotics. His condition worsened, developing expectoration of non-bloodstained sputum, shortness of breath, and chest soreness. There was no history of exposure to birds or any new environments. Chest auscultation detected scattered rales and expiratory wheezes. Chest X-ray showed bilateral diffuse infiltrates and consolidation of right lower lobe. Gram stain of sputum showed presence of leukocytes and normal flora. Routine culture for bacterial pathogens grew only normal flora. The microbiology laboratory was not equipped for isolation of fastidious organisms. Considering the presumptive clinical diagnosis of atypical pneumonia, a supportive non-specific serological test was done to detect cross-reacting antibodies to human erythrocytes. The test results showed significant titer of the antibodies.

What is likely to be the causative agent in this patient?

1 Chlamydia pneumoniae
2 Legionella pneumoniae
3 Mycoplasma pneumoniae
4 Coxiella burnetii
5 Chlamydia psittaci

Answer 2

Mycoplasma pneumoniae

Mycoplasma pneumoniae is a pathogen most frequently associated with atypical community-acquired pneumonia. Atypical pneumonia caused by M. pneumoniae is more common in school children and young adults. The bacterium usually causes asymptomatic infection or mild respiratory disease. Bronchopneumonia involving 1 or more lobes develops in 3-10% of infected persons.
A non-specific serological test using human O group RBCs can be used for detecting cold agglutinin titers in pneumonia caused by Mycoplasma pneumoniae. High levels are seen in about 50-60% of untreated patients with M. pneumoniae pneumonia. In a patient strongly suspected of having M. pneumoniae infection, the presence of cold agglutinins with a significant titer is reasonably supportive evidence for a diagnosis. Even though non-specific and crude, a positive cold agglutination test is helpful in diagnosing M. pneumoniae pneumonia in adults. A significant level of cold agglutinins is not seen in infections by other microorganisms listed.
Chlamydia pneumoniae is another important agent of community-acquired atypical pneumonia. This is an obligate intracellular organism capable of persistent latent infection. Most cases of pneumonia are mild and the clinical spectrum resembles M. pneumoniae infection. Diagnosis of C. pneumoniae pneumonia is by antigen detection using EIA, direct immunofluorescence, or molecular methods. A cold agglutination test is negative.
Legionella pneumophila is an aerobic, fastidious, Gram-negative bacillus associated with community-acquired pneumonia. Several serotypes have been identified. Outbreaks of infections have been associated with condensers, cooling towers, respiratory therapy equipment, showers, whirlpools, and water faucets. Laboratory diagnosis is by demonstration of the organisms in clinical specimens such as sputum, bronchial lavage, lung biopsy by fluorescent antibody test, isolation of the pathogen by culture on specialized media, by urinary legionella antigen test, and by demonstration of specific antibodies in serum by ELISA or indirect fluorescent assay. Cold agglutinins are not a feature of this infection.
Coxiella burnetii belongs to the Rickettsial group of organisms. It causes Q fever, a zoonotic disease transmitted by ticks among domestic livestock and other animals. Though ticks are important vectors and transmit the infection among animals, they do not seem to be important in the transmission of human infection.
Chlamydia psittaci causes psittacosis, a zoonotic disease acquired from birds. Infection can produce a wide spectrum of diseases ranging from mild influenza-like illness to fatal pneumonia. Inhalation of infected dried bird excreta is the common mode of infection. Human infections are mostly occupational and seen in poultry workers, pet shop owners, and veterinarians.

Question 3

As part of a study on bacterial agents associated with non-gonococcal urethritis (NGU), a sample of urethral discharge collected from an adult male was cultured on A8 selective agar medium. After 48 hours of incubation in the presence of carbon dioxide, tiny brown colored colonies measuring 15-20 microns were detected on the medium using stereomicroscope. This isolate is likely to possess what characteristic?

1 Growth is inhibited by sterol
2 Is susceptible to beta-lactam antibiotics
3 Lipopolysaccharide (LPS) is a virulence factor
4 Is genetically related to bacterial L-forms
5 Produces urease enzyme

Answer 3

Produces urease enzyme

The common bacterial agents associated with NGU are Chlamydia trachomatis, genital Mycoplasmas, and Ureaplasmas. Of these, C.trachomatis is a strict intracellular organism and does not grow on inanimate media.
Ureaplasma and mycoplasma are fastidious organisms. They can be differentiated and identified to genus level by their colony characteristics on A8 selective medium. The isolate from the urethral discharge has the colony characteristics typical of Ureaplasma. Ureaplasma was known as ‘T-strain mycoplasma’ earlier because it produces tiny colonies (T for tiny). The bacterium produces urease enzyme, which hydrolyzes urea and liberates ammonia. Urea is provided in A8 agar and the brown color of ureaplasma colonies is due to the activity of urease enzyme in presence of calcium chloride contained in the medium. Urease is considered as a potential virulence factor of ureaplasma. Urea is an essential growth factor and urea hydrolysis is the predominant means by which the organisms generate ATP.
Mycoplasma colonies are larger measuring 200-300 microns in diameter with typical fried egg appearance.
The isolate being Ureaplasma sp, does not possess the other characteristics listed. Like mycoplasma, it lacks a rigid cell wall and is bounded by a triple-layered cell membrane containing sterols. Sterol is not inhibitory, but essential for the growth of ureaplasma.
Beta-lactam antibiotics act by inhibiting cell wall synthesis. Ureaplasma is not susceptible to beta-lactams as it does not possess a cell wall. LPS is an integral part of the cell wall of Gram-negative bacteria and is not found in ureaplasma.
L-forms of bacteria can revert back to their parental bacterial forms under favorable environment, by synthesizing cell wall peptidoglycan. Ureaplasma does not produce cell wall under any circumstances and are not related to L-forms of bacteria.
The 2 species of genital ureaplasmas, Ureaplasma urealyticum and Ureaplasma parvum,colonize on human mucosal surfaces as commensals. Both species, particularly U.urealyicum, are potentially pathogenic. U.urealyticum is recognized as an important causative agent of NGU and could be associated with persistent and recurrent urethritis. Maternal genital colonization with U.urealyticum can lead to chorioamnionitis and promote preterm delivery. Ureaplasmas are associated with neonatal and perinatal infections like pneumonia and meningitis in premature and low birth weight infants. Respiratory colonization of such infants by the organisms has been reported to increase the risk of developing bronchopulmonary dysplasia (BPD). Ureaplasma sp have also been linked to male infertility and to formation of struvite stones in the urinary tract. Stone formation is considered to be mediated by the urease activity of these bacteria.
Polymerase chain reaction assays targeting different genes (16S rRNA gene, urease gene, and MBA gene) have been developed for detecting ureaplasmas in clinical specimens and for distinguishing the 2 species. The tests are reported to have high specificity and sensitivity.

Question 4

During the first half of 20th century, massive epidemics of an arthropod-borne spirochetal disease with high fatality rates occurred in Eurasia and Africa. The epidemics were favored by overcrowding, lack of hygiene, cold weather, and malnutrition. Now the disease has become very rare and is confined to a few geographical areas like Ethiopia. Diagnosis of this disease is commonly made by detection of the spirochetes in blood smears stained by Giemsa or Wright stain. What is characteristic of this spirochetal agent?

1 Motility is due to presence of a single polar flagellum
2 In stained blood films, is seen intracellularly within the RBCs
3 Trans-ovarial transmission occurs in the arthropod vector
4 Main reservoir hosts are rodents
5 Undergoes antigenic variation in vivo

Answer 4

Undergoes antigenic variation in vivo

Louse-borne relapsing fever (LBRF) is the only arthropod-borne spirochetal disease that fits in with the description of the illness given in question. The disease is caused by Borrelia recurrentis and is transmitted by human body louse (Pediculus humanis corporis).
Borrelia recurrentis readily undergoes antigenic variations in vivo, and this characteristic is responsible for the febrile relapses. The organism does not possess the other features listed.
Borrelia recurrentis possesses 8-10 periplasmic flagella. The internalized flagella are encased in the periplasmic space (endoflagella). In stained blood films, the spirochetes are seen as large (10-30 microns long and 0.3 microns wide) loosely coiled spirals among the RBCs, not within. Tissues of the infected louse are not invaded by the spirochetes, and therefore transovarial transmission to the progeny does not occur. Humans are the only known reservoir hosts for B.recurrentis.
Development of antigenic variants is an immune evasion strategy of both louse-borne and tick-borne relapsing fever spirochetes. Tick-borne relapsing fever is endemic and can be caused by different species of borrelia.
The studies on the antigenic variation of B.recurrentis are limited. Most studies have been done on B.hermsii, which causes tick-borne relapsing fever in Western USA. Antigenic variations occur in the outer surface proteins. The surface proteins involved are known as Variant major proteins (Vmp). Based on their size, Vmps have been divided into variant large proteins (Vlps) encoded by vlp genes and variant small proteins (Vsps) encoded by vsp genes. Silent and expressed vlp and vsp genes are located on plasmids present within the spirochete.
In infected lice, the borreliae are confined to the hemolymph. Human infection by B.recurrentis occurs when lice are crushed and rubbed into abraded skin. After an incubation period of 2-10 days, severe clinical disease sets in due to massive spirochetemia. This period is terminated by the agglutinating and lytic effects of the antibodies and is followed by an afebrile period of 4-10 days. The antibodies developed initially act as a selective factor for the survival of the antigenically distinct variants. The variants multiply in the internal organs and reemerge in the blood stream, giving rise to febrile relapses. Ultimate recovery may occur after 3-10 relapses, with development of immunity to all the antigenic variants. Louse-borne relapsing fever presents a more severe clinical picture than the tick-borne variety and is associated with jaundice, hemorrhages, and high fatality rate.
Tetracyclines, penicillin, and erythromycin are used for treatment of relapsing fever.

Question 5

Which of the following is true about Mycoplasma?

1 Mycoplasma are the smallest free-livings microorganisms known to exist
2 Mycoplasma is the only member of the family Mycoplasmataceae
3 Mycoplasma pneumoniae is the only species of Mycoplasma known to cause disease in humans
4 The large size of the Mycoplasma genome most likely results from the number of genes necessary to code for the complex cell wall possessed by all Mycoplasma species
5 Mycoplasma are universally sensitive to both penicillins and cephalosporins

Answer 5

Mycoplasma are the smallest free-livings microorganisms known to exist

While it is true that Mycoplasma are the smallest free-living organisms recognized, the other possible answers provided above are, in fact, not true. Ureaplasma is also a member of the same family as Mycoplasma (Mycoplasmataceae), and other Mycoplasma species (such as M. hominis) are also known to cause disease in humans. The Mycoplasma genome is relatively small and composed of double-stranded DNA. The small genome likely results due to the lack of genes coding for a complex cell wall. Mycoplasma have no cell wall but instead have a sterol-containing triple-layered membrane. This lack of a cell wall makes penicillins and cephalosporins ineffective against Mycoplasma.

Question 6

Which of the following is true about Ureaplasma infections?

1 Ureaplasma urealyticum is a cause of some genitourinary tract infections
2 Ureaplasma have a cell wall similar to other gram-positive bacteria
3 Paradoxically, the likelihood of colonization by Ureaplasma is inversely related to the number of sexual partners reported by an individual
4 Unlike Ureaplasma urealyticum, U. pneumoniae is primarily associated with respiratory tract infections

Answer 6

Ureaplasma urealyticum is a cause of some genitourinary tract infections

Ureaplasma urealyticum is a cause of some genitourinary infections, and the likelihood of urinary tract colonization is proportional to the number of sexual partners reported by an individual. Ureaplasma (like Mycoplasma) do not have a cell wall, but instead have a triple-layered membrane. To date, no organism known as Ureaplasma pneumoniae has been identified, and Ureaplasma is not known to be a respiratory tract pathogen.

Question 7

Case
A 25-year-old man living in Delaware presents with a rash on his left leg. The rash appeared 1 week ago as a small red area and is getting bigger. The patient is also experiencing muscle pain, joint stiffness, and fatigue; however, he is not sure whether these symptoms are just associated with the increased exercise in which he has been participating. On physical exam, he has a flat circular lesion on his leg that is pale in the center and red at the periphery. The rest of the exam is normal.

What is the most likely causal agent?

1 Bordetella pertussis
2 Borrelia Burgdorferi
3 Brucella
4 Francisella tularensis
5 Rickettsia rickettsii

Answer 7

Borrelia Burgdorferi

Borrelia burgdorferi is a spirochete transmitted to humans by a deer tick (Ixodes scapularis). It causes Lyme disease; there are 3 stages of this disease:
Stage 1 (early localized): Usually the first 10 days after the bite. It is a localized erythematous macule or papule, pale in the center (erythema migrans). It is present at the site of the bite, accompanied by flu-like symptoms.
Stage 2 (early disseminated): A few weeks later. Usually, neurological symptoms such as facial nerve palsy or meningitis develop, and cardiac symptoms such as arrhythmias or pericarditis are seen.
Stage 3 (late chronic disease): Develops even years later with symptoms such as arthritis, dermatitis, and cardiomegaly.
The diagnosis is mainly clinical; a “target” or “bull’s eye” skin lesion and history of exposure to ticks are characteristic. The treatment depends on the severity and the stage of the disease. Doxycycline is used in early stages.
Bordetella pertussis is a Gram-negative coccobacillus. The main symptoms are paroxysmal cough and vomiting. It is transmitted by direct contact with the respiratory discharge of infected persons.
Brucella is a group of bacteria found in animals such as dogs, goats, sheep, cattle, deer, or pigs. Humans become infected (Brucellosis) when they come in contact with the animals or their products (milk). Brucellosis can produce abscesses in many different organs, such as liver and spleen. The treatment depends on the type of presentation.
Francisella tularensis is a Gram-negative rod that causes tularemia (rabbit fever). It is transmitted to humans by ticks (A. americanum, D. variabilis, and D. Anderson) or flies but also by eating uncooked infected meat, contaminated water, or through skin lesions when skinning rabbits that are infected. The ulceroglandular manifestation is most common. Symptoms similar to flu appear 3 to 5 days after the inoculation and, depending on the source of infection, the patient can also show skin ulcers, pneumonia, pericarditis, and regional lymphadenopathy. The diagnosis is done by serology, but a PCR of the ulcer is also available. Although a vaccine has been around for 50 years, its use has not yet been approved. The treatment is streptomycin and gentamicin.
Rickettsia rickettsii is a rickettsia that causes Rocky Mountain spotted fever. It is transmitted to humans by the wood tick (Dermacentor andersoni) and the dog tick (Dermacentor variabilis). Typical symptoms include flu-like illness appearing 5 to 7 days after the inoculation and a rash (pink macules) that begins in palms and soles, disseminating to the rest of the body and disappearing with pressure. Later on, ulceration and ecchymosis can be seen. The neurologic and circulatory systems can also be involved. Treatment is with tetracycline, doxycycline, and chloramphenicol.

Question 8

Case
A 7-year-old boy is brought to the pediatrician with a rash that appeared 3 days ago. It began on the palms and soles and now covers most of his body. He also complains of fever, nausea, vomiting, sore throat, abdominal pain, and headache. On physical exam, the patient has pink macules all over his body, which disappear with pressure. He also has some ulcers and ecchymosis.

What is the most likely cause of this infection?

1 Bordetella pertussis
2 Borrelia Burdorferi
3 Brucella
4 Francisella tularensis
5 Rickettsia rickettsii

Answer 8

Rickettsia rickettsii

Rickettsia rickettsii is a rickettsia that causes Rocky Mountain spotted fever. It is transmitted to humans by the wood tick (Dermacentor andersoni) and the dog tick (Dermacentor variabilis). Typical symptoms include flu-like illness appearing 5 to 7 days after the inoculation and a rash (pink macules) that begins in palms and soles, disseminating to the rest of the body and disappearing with pressure. Later on, ulceration and ecchymosis can be seen. The neurologic and circulatory systems can also be involved. Treatment is with tetracycline, doxycycline, and chloramphenicol.
Bordetella pertussis is a Gram-negative coccobacillus. The main symptoms are paroxysmal cough and vomiting. It is transmitted by direct contact with the respiratory discharge of infected persons.
Borrelia burgdorferi is a spirochete transmitted to humans by a deer tick (Ixodes scapularis). It causes Lyme disease; there are 3 stages of this disease:
Stage 1 (early localized): Usually the first 10 days after the bite. It is a localized erythematous macule or papule, pale in the center (erythema migrans). It is present at the site of the bite, accompanied by flu-like symptoms.
Stage 2 (early disseminated): A few weeks later. Usually, neurological symptoms such as facial nerve palsy or meningitis develop, and cardiac symptoms such as arrhythmias or pericarditis are seen.
Stage 3 (late chronic disease): Develops even years later with symptoms such as arthritis, dermatitis, and cardiomegaly.
The diagnosis is mainly clinical; a “target” or “bull’s eye” skin lesion and history of exposure to ticks are characteristic. The treatment depends on the severity and the stage of the disease. Doxycycline is used in early stages.
Brucella is a group of bacteria found in animals such as dogs, goats, sheep, cattle, deer, or pigs. Humans become infected (Brucellosis) when they come in contact with the animals or their products (milk). Brucellosis can produce abscesses in many different organs, such as liver and spleen. The treatment depends on the type of presentation.
Francisella tularensis is a Gram-negative rod that causes tularemia (rabbit fever). It is transmitted to humans by ticks (A. americanum, D. variabilis, and D. Anderson) or flies but also by eating uncooked infected meat, contaminated water, or through skin lesions when skinning rabbits that are infected. The ulceroglandular manifestation is most common. Symptoms similar to flu appear 3 to 5 days after the inoculation and, depending on the source of infection, the patient can also show skin ulcers, pneumonia, pericarditis, and regional lymphadenopathy. The diagnosis is done by serology, but a PCR of the ulcer is also available. Although a vaccine has been around for 50 years, its use has not yet been approved. The treatment is streptomycin and gentamicin.

Question 9

Case
Sixteen game show contestants volunteer to be stranded for 39 days on a remote island in Borneo, which is in the middle of the South China Sea, for a chance to win 1 million dollars. During the third week of the game, a contestant develops fever, chills, and muscle aches. She is unable to compete in any challenges because she is too ill. Her muscles ache, and pains markedly limit her physical capacity. Her condition worsens and she develops vomiting and diarrhea. She is examined by the television network’s doctor. He notices that her liver is enlarged. She has conjunctival suffusion.

What is the agent that is likely causing her disease?

1 Rickettsia
2 Leptospira
3 Chlamydia
4 Mycobacteria
5 Legionella

Answer 9

Leptospira

The clinical condition is consistent with the diagnosis of leptospirosis. Leptospirosis is caused by spirochetes called Leptospira. Leptospira are spiral-shaped obligate aerobes. Fever, severe muscles aches, nausea and vomiting, jaundice, and a conjunctival suffusion can all be seen with leptospirosis. Central nervous system findings may also be present. The organism is transmitted via breaks in the skin or mucosa. It is commonly transmitted via contaminated water.
Rickettsia are obligate intracellular coccobacilli. Examples include Rickettsia rickettsii and Rickettsia prowazekii. Rickettsial diseases often produce fever and myalgias but also a rash.
Chlamydia are obligate intracellular parasites. Examples include Chlamydia trachomatis, which causes genital infections, and Chlamydia pneumoniae, which causes pneumonia.
Mycobacteria are rod-shaped bacteria. Examples include Mycobacteria tuberculosis and Mycobacteria leprae. Mycobacterial infections are associated with tuberculosis and pneumoniae. They may also cause some types of skin infections.
Legionella are aerobic Gram-negative bacteria. Infection may be asymptomatic or cause severe disease marked by fevers, hypoxia, chills, diarrhea, and delirium. The organism grows in moist environments.

Question 10

Which of the following is the smallest free living organism in nature?

1 Fungi
2 Virus
3 Coxiella
4 Mycoplasmas

Answer 10

Mycoplasmas

Mycoplasmas are the smallest free-living pleomorphic organisms. They lack a cell wall, which renders them resistant to cell wall active antibiotics. The cytoplasmic contents are embedded in plasma membrane.
The additional characteristics of Mycoplasmas are as follows:
Highly fastidious
Facultative anaerobe (except Mycoplasma pneumoniae)
Membrane glycolipids and proteins are major antigenic determinants
Divide by binary fission
Most species requires media with cholesterol and fatty acids for growth
Colony gives “fried egg” appearance on solid media
Resistant to cell wall active antibiotics
Fungi are eukaryotes that consist of mitochondria and nucleus with nuclear membrane. They absorb nutrients from the environment and are much bigger than Mycoplasmas in size.
Coxiella
are obligate intracellular parasites.
Viruses are the parasite that can function only within another cell and uses host cell components to assemble new virus particles.

Question 11

A 27-year old female developed mild fever, malaise, headache and mild cough while she was visiting family in Mexico. She had loss of appetite and felt lethargic. The parents took her to the family physician who gave her ampicillin and some cough syrup. There was no improvement in her condition and she was not able to sleep because of unproductive cough. She felt weak and had shortness of breath. On her next visit to the doctor’s office she was given some sleeping pills and asthalin with cephalothin. She was able to sleep well with the pills but her cough was getting worse. She returned to Baltimore and resumed to working. She was able to function properly except for the dry cough and was seen at the university physician center. The chest radiograph revealed patchy infiltrates with feathery outline. The gram stain of the sputum was negative for bacteria but had many neutrophils. The routine cultures were negative. Her cold agglutinin titer was 1:128. The physician prescribed her erythromycin and patient recovered within 12 days. What is the etiological agent of patient’s condition?

1 Streptococcus pneumoniae
2 Haemophilus influenza
3 Mycoplasma pneumoniae
4 Staphylococcus aureus

Answer 11

Mycoplasma pneumoniae

Mycoplasma pneumoniae is the causative agent of atypical pneumoniae or walking pneumoniae. Infection is spread by close contacts and is community acquired. The organism is very small in size and can not be revealed by gram stain.
The patient did not respond to ampicillin and cephalothin as these antibiotics are cell wall active antibiotics and Mycoplasma pneumoniae lacks the cell wall.

Question 12

Which of the following causative agents corresponds with rocky mountain spotted fever?
Answer Choices

1 Coxiella burnetii
2 Rickettsia rickettsii
3 Rickettsia tsutsugamushi
4 Rickettsia prowazekii
5 Rochalimaea quintana

Answer 12

Rickettsia rickettsii

Rickettsia rickettsii is associated with Rocky mountain spotted fever. Human acquires the infection through tick bite. Clinical symptoms are fever, rash, headache, myalgia, nausea and lymphadenopathy. There is hematogenous spread of the organism throughout the body. It causes vasculitis in the blood vessels of the lungs, heart and brain leading to pneumonitis, myocarditis and central nervous system. Vasculitis can lead to decreased blood volume, hypotension, and intravascular coagulation.
The infection can be treated with tetracycline or chloramphenicol.

Question 13

An outbreak of Epidemic louse borne typhus is favored by crowded living conditions with poor hygiene and is especially common in parts of central and northeastern Africa. Which of the following causative organisms is spread by a louse and causes epidemic louse borne typhus?

1 Coxiella burnetii
2 Rickettsia rickettsii
3 Rickettsia tsutsugamushi
4 Rickettsia prowazekii
5 Rochalimaea quintana

Answer 13

Rickettsia prowazekii

Epidemic typhus is louse borne and is caused by Rickettsia prowazekii. It has 10 to 14 days of incubation period. The infection is characterized by high fever and rash on trunk and extremities. It has a high mortality rate (40% for untreated patients). Myocardial and neurological involvement can lead to the death of the patient. Treatment includes tetracycline or chloramphenicol in combination with measures for louse control.Rickettsia prowazekii can reactivate and cause Brill-Zinsser disease (recrudescent typhus) in previously infected host.

Question 14

Which of the following causative agents corresponds with scrub typhus

1 Coxiella burnetii
2 Rickettsia rickettsii
3 Rickettsia tsutsugamushi
4 Rickettsia prowazekii
5 Rochalimaea quintana

Answer 14

Rickettsia tsutsugamushi

Chiggers (red mite) are the vector involved in transmission of Rickettsia tsutsugamushi, the causative agent of scrub typhus. It is characterized by development of an eschar at the site of mite bite along with fever, headache and rash all over the body. Untreated cases can lead to death due to serious neurological and cardiovascular complications.

Question 15

Which of the following causative agents corresponds with Q fever

1 Coxiella burnetii
2 Rickettsia rickettsii
3 Rickettsia tsutsugamushi
4 Rickettsia prowazekii
5 Rochalimaea quintana

Answer 15

Coxiella burnetii

Coxiella burnetii is associated with Q fever and is transmitted by inhalation of infected aerosols. Q fever occurs mostly among people working with livestock or research animals. Clinical manifestation of the disease includes flu-like symptoms characterized by high fever and lack of rash. Hepatosplenomegaly or pneumonia is observed in some patients. Endocarditis is serious sequela of chronic Q fever and has poor prognosis.

Question 16

The most frequent cause of sexually transmitted disease in the United States is

1 Ureaplasma Urealyticum
2 Mycoplasma hominis
3 Neisseria gonorrhoeae
4 Chlamydia trachomatis
5 Haemophilus ducreyi

Answer 16

Chlamydia trachomatis

Chlamydia trachomatis is most frequent cause of sexually transmitted disease in the United States. Each year 4 to 10 million new cases are reported. It is associated with following infections:
Lymphogranuloma venereum
Non gonococcal urethritis
Epididymitis
Prostatitis
Follicular Cervicitis
Endometritis
Proctitis
Salpingitis that may lead to sterility
Pelvic Inflammatory disease

Question 17

Which of the following is associated with ornithosis

1 Chlamydia trachomatis
2 Chlamydia psittaci
3 Rickettsia rickettsii
4 Rickettsia typhi
5 Coxiella burnetii

Answer 17

Chlamydia psittaci

Ornithosis or parrot fever is caused by Chlamydia psittaci and is commonly known as psittacosis. It is associated with exposure to birds, mostly parrots. Four fold rise in complement fixing antibody to the chlamydial group LPS antigen is observed.

Question 18

Borrelia burgdorferi is the etiological agent of:

1 Relapsing fever
2 Plague
3 Chagas disease
4 Lyme disease
5 Psittacosis

Answer 18

Lyme disease

Lyme disease is caused by a spirochete Borrelia burgdorferi that is transmitted via tick. Lyme disease is more prevalent in the Northeast and Midwest regions of the Unites States and is common between May and November. The clinical symptoms include fever, headache, weakness, and muscle pain. The site of tick bite shows the skin lesions known as erythema chronicum migrans. The common manifestation of the disease includes arthritis, cardiac, and neurological problems. The drug of choice is tetracycline for patients over 9 years of age and penicillin for children under 9 years of age.
The table given below describes the zoonotic diseases with their corresponding etiological agents.
Disease Etiological Agents
Relapsing fever Borrelia recurrentis
Plague Yersinia pestis
Chagas disease Trypanosoma cruzi
Lyme disease Borrelia burgdorfeeri
Psittacosis Chlamydia psittaci

Question 19

Ixodes tick is the vector for

1 Plague
2 Malaria
3 Epidemic typhus
4 Lyme disease
5 Scrub typhus

Answer 19

Lyme disease

Lyme disease is zoonotic disease caused by Borrelia burgdorferi. It is a leading vector borne disease that is more common in Northeast and Midwest areas of the United States. The organism is inoculated in the host by Ixodes tick bite. This results in the development of skin lesion (erythema migrans) at the site of inoculation.
The vector to disease association is given in the following table.
DISEASE VECTOR
Plague Flea
Maleria Anopheles Mosquito
Epidemic typhus Body Louse
Lyme disease Ixodes tick
Scrub typhus Chigger

Question 20

Treponema pallidum ssp pallidum:

1 Can be visualized by gram stain under light microscope
2 Can be grown in vitro on artificial media
3 Is strict aerobe
4 Is associated with congenital syphilis

Answer 20

Is associated with congenital syphilis

Treponema pallidum ssp pallidum can not be seen by gram stain under light microscope because the transverse diameter of all pathogenic treponemes is below the ordinary light microscope.
It can be demonstrated by dark field microscopy or with specialized stains that impregnates on the cell. The organisms can be seen in exudates of chancres or secondary lesions.
It is an anaerobe that can not be grown in vitro or on artificial blood agar.Treponema pallidum ssp pallidum infects the neonate in utero by crossing the placenta or when it passes through the birth canal.
Congenital syphilis can result in premature birth or still birth, neonatal disease or latent infections.

Question 21

RPR and VDRL test

1 Employs Treponema pallidum antigen harvested in rabbit
2 Detects antibody specific to treponeme antigen
3 Remains positive after the patient is treated
4 Can yield biological false positive result in malaria patients
5 Cannot yield biological false positive result in malaria patients

Answer 21

Can yield biological false positive result in malaria patients

RPR and VDRL test are nonspecific nontreponemal test. Reagin is a distinct antibody of IgG and IgM nature that appears in patients with syphilis. These tests employ a cardiolipin antigen extracted from the heart muscle of an ox.
1The likelihood of a biologic false-positive (BFP) reaction depends on the underlying circumstances. For example, acute or transient false-positive nontreponemal reaginic test reactions may occur whenever there is a strong immunologic stimulus (e.g., acute bacterial or viral infection, vaccination, IV drug abuse, untreated HIV infection).
This cardiolipin antigen reacts with reagin antibody in RPR and VDRL test, giving visible reaction. These tests are used for the screening purpose for monitoring the course of the treatment. The test becomes negative once the patient is treated adequately.

Question 22

Primary syphilis is characterized by

1 Destructive gummas
2 Genital chancres
3 Tabes dorsalis
4 Absence of organism in the skin lesions

Answer 22

Genital chancres

Spirochetes produce inflammatory chancre at the site of inoculation. After entering the host the organism moves to lymph nodes and then to bloodstream. Spirochetes are demonstrable in primary lesions by darkfield microscopy.
Secondary syphilis is characterized by appearance of maculopapular rash all over the body. These rash as well as chancres contain large number of organism and are highly infectious.
Appearance of gummas indicates tertiary stage of syphilis. Gummas are non infectious, nonspecific granulomatous lesions that do not contain the spirochetes.
Tertiary stage of syphilis is characterized by the following:
Presence of gummas in skin, bones, and liver
Neurosyphilis that can be manifested as
Meningovascular syphilis
Tabes dorsalis
General paresis
Syphilitic cardiovascular lesion manifested as
Aortitis
Aortic aneurysm
>Aortic valve insufficiency

Question 23

Treponema pallidum ssp endemicum is the causative agent of

1 Syphilis
2 Yaws
3 Pinta
4 Bejel

Answer 23

Bejel

Syphilis is a venereal disease caused by Treponema pallidum ssp pallidum. Yaws, Pinta and Bejel are non venereal treponemal disease acquired by direct contact. All four infections can be treated with penicillin.
Following table summarizes the associations of treponemes with the clinical infection.
Disease Causative Agent
Syphilis Treponema pallidum ssp pallidum
Yaws Treponema pallidum ssp pertenue
Pinta Treponema pallidum ssp carateum
Bejel Treponema pallidum ssp endemicum

Question 24

The organ that is the main focus of disease in Q fever is the

1 Skin
2 Lungs
3 Kidneys
4 Heart
5 Brain

Answer 24

Lungs

Lungs are the main focus of disease in Q fever. The skin, kidneys, heart, and brain are not involved.

Question 25

The mode of transmission of Q fever is

1 Bite of arthropod
2 Inhalation of aerosols
3 Contact with body fluids
4 Louse bite
5 Tick bite

Answer 25

Inhalation of aerosols

Q fever is spread by inhalation of C. burnetii aerosols. It is not spread by bite of arthropods, louse or ticks.

Question 26

The Weil-Felix test is used for detection of which of the following type of antibodies?

1 Antirickettsial
2 Antichlamydial
3 Antiarenavirus
4 Antiretrovirus
5 Antitogavirus

Answer 26

Antirickettsial

The Weil-Felix test is used for detection of antirickettsial antibodies. These are detected in the patient’s serum by their ability to agglutinate Proteus bacteria. The specific rickettsial organism can be identified by the agglutination observed with the O antigen polysaccharide of one or another of three different strains (OX-2, OX-19 and OX-K) of Proteus vulgaris. However, the test is of limited value as there can be false positives following Proteus urinary tract infection and false negatives due to variable antibody response.

Question 27

You are an epidemiologist employed by the Public Health Service to investigate several outbreaks of disease. Which organism is MOST likely to cause an outbreak in people handling birds originating from Central America?

1 Chlamydia psittaci
2 Yersinia pestis
3 Rickettsiae prowazeki
4 Mycobacterium tuberculosis
5 Brucella melitensis

Answer 27

Chlamydia psittaci

Chlamydia psittaci is an obligate intracellular parasite and its habitat is birds, both psittacine and others. Transmission is via aerosol of dried bird feces.

Question 28

Rocky mountain spotted fever is caused by

1 Rickettsia rickettsi
2 Chlamydia trachomatis
3 Herpes virus
4 Leptospira
5 Brucella melitensis

Answer 28

Rickettsia rickettsi

Rocky mountain spotted fever is caused by Rickettsia rickettsi , an obligate intracellular parasite. The Dermacentor ticks are the natural reservoir and transmission is via tick bite. The organism invades the endothelial lining of capillaries, causing vasculitis.

Question 29

Syphilis is caused by

1 Actinomyces
2 Treponema pallidum
3 Borrelia burgdorferi
4 Mycoplasma pneumoniae
5 Nocardia

Answer 29

Treponema pallidum

Syphilis is caused by Treponema pallidum, whose habitat is the human genital tract and transmission is by sexual contact and from mother to fetus across the placenta. The organism multiplies at the site of inoculation and then spreads widely via the bloodstream.
Lyme disease is caused by Borrelia burgdorferi which is found in ixodid ticks. The organism invades skin and spreads via the bloodstream to involve primarily the heart, joints, and central nervous system.
Q fever is caused by Coxiella burnetii, an obligate intracellular parasite. Its habitat is domestic livestock and it is the only rickettsia not transmitted to humans by an anthropod.

Question 30

Lyme disease is caused by

1 Borrelia burgdorferi
2 Treponema pallidum
3 Nocardia asteroides
4 Chlamydia trachomatis
5 Coxiella burnetii

Answer 30

Borrelia burgdorferi

Lyme disease is caused by Borrelia burgdorferi, which is found in ixodid ticks. The organism invades skin and spreads via the bloodstream to involve primarily the heart, joints, and central nervous system.
Syphilis is caused by Treponema pallidum, whose habitat is the human genital tract and transmission is by sexual contact and from mother to fetus across the placenta. The organism multiplies at the site of inoculation and then spreads widely via the bloodstream.
Q fever is caused by Coxiella burnetii, an obligate intracellular parasite. Its habitat is domestic livestock and it is the only rickettsia not transmitted to humans by an anthropod.

Question 31

Q fever is caused by

1 Coxiella burnetii
2 Leptospira interrogans
3 Chlamydia trachomatis
4 Chlamydia psittaci
5 Herpes virus

Answer 31

Coxiella burnetii

Q fever is caused by Coxiella burnetii, an obligate intracellular parasite. Its habitat is domestic livestock and is the only rickettsia not transmitted to humans by an anthropod.

Question 32

Treponema pallidum is the causative agent of syphilis, a sexually transmitted disease which naturally occurs only in humans. To what group of bacteria do these organisms belong?

1 Spirochetes
2 Spirillum
3 Filamentous
4 Enterobacteriaceae

Answer 32

Spirochetes

Treponema pallidum is a member of the spirochete group of bacteria. These are flexible, helical bacteria which contain a fibrillar structure similar to a flagella. These are associated with the cell wall and are called endoflagella. These bacteria are gram-negative, but are generally too thin to observe by standard light microscopy. Because of this, several special methods and techniques are used to observe these organisms. Dark field microscopy, florescent antibodies, and electron microscopy are all used for this purpose.

Question 33

Case
An 18-year-old woman presents with a mild fever and feels achy all over. Over the course of the next 3 days, she develops a headache and a hacking non-productive cough. She sees the student health service because of her symptoms. Her physical examination is not very dramatic, except that chest examination reveals slight rales. Her chest x-ray shows patchy infiltration, predominantly at the bases of the lung. No pleural fluid is seen. Her laboratory results are as follows:
TEST RESULTS REFERENCE RANGE
Hematocrit 40 40-50 (male)
36-44 (female)
Hemoglobin 13.2 gm/dL 13.8-17.2 gm/dL (male)
12.1-15.1 gm/dL (female)
RBC 4.3 x 106/μl 4.5-5.7 x 106/μl (male)
3.9-5.0 x 106/μl (female)
Platelets 239,000/mm3 130,000-400,000/mm3
mean corpuscular volume 95 cu μ 80-100 cu μ
MCHC 34 31-36
WBC 11.8 x 103/mm3 4.0-11 x 103/mm3
Neutrophils 71 40-75%
Lymphocytes 17 15-45%
Monocytes 8 1-10%
Eosinophils 4 1-6 %
Basophils 0 0-2 %
Her doctor prescribes medication for her, but she loses the prescription. She decides to simply rest and not bother with medication. Unfortunately, a week later she is again seen by the student health service because of sudden and pronounced hemolysis.

What is the classification of the agent that caused her disease?

1 Mycoplasma
2 Rickettsia
3 Enteric bacilli
4 Chlamydia
5 Mycobacteria

Answer 33

Mycoplasma

This patient has Mycoplasma pneumonia caused by Mycoplasma pneumoniae, and cold antibody hemolytic anemia is seen in this condition.
Mycoplasma pneumonia is sometimes called “atypical pneumonia” or “walking pneumonia”. Mycoplasma pneumonia has a slower onset than some other types of pneumonia. The hacking dry cough that she has is characteristic of Mycoplasma pneumonia. The white blood count can be normal or elevated, as is the case here. Cold agglutinins are seen in over 50% of the cases of Mycoplasma pneumonia. Cold agglutinins are IgM antibodies. These antibodies agglutinate red blood cells at 4°C but not at 37°C. The result is hemolysis, which is more prominent at low temperatures and parts of the body exposed to lower temperatures.
The causative agent is Mycoplasma pneumoniae, a type of mycoplasma. Mycoplasmas are free-living organisms. Other mycoplasmas include Mycoplasma hominis. Ureaplasma is closely related.
Rickettsia are obligate intracellular organisms. Examples include Rickettsia rickettsii and Rickettsia prowazekii.
There are many human pathogens that are enteric bacilli. Most enteric bacilli are in the family Enterobacteriacae and Vibrionaceae. Specific examples include Salmonella typhi, Escherichia coli, and Klebsiella pneumoniae.
Chlamydia are obligate intracellular parasites. Examples include Chlamydia trachomatis and Chlamydia psittaci.
Mycobacteria are rod-shaped bacteria. Examples include Mycobacteria tuberculosis and Mycobacteria leprae. Mycoplasma pneumonia is not caused by mycobacteria.

Question 34

Case
A 27-year-old man presents with burning pain with urination. There is also some urethral discharge. Several laboratory tests are done, including a Gram stain and culture on a sample of the discharge. The results are negative, and gonorrhea is ruled out. He is diagnosed with nongonococcal urethritis.

What mycoplasma could cause this patient’s nongonococcal urethritis?

1 Chlamydia psittaci
2 Chlamydia trachomatis
3 Ureaplasma urealyticum
4 Trichomonas vaginalis
5 Pneumocystis jirovecii

Answer 34

Ureaplasma urealyticum

Urethritis is an inflammation of the urethra. It is classified as either gonococcal urethritis (caused by Neisseria gonorrhoeae) or nongonococcal urethritis (caused by something other than Neisseria gonorrhoeae). Common causes of nongonococcal urethritis are Chlamydia trachomatis, Trichomonas vaginalis, and Ureaplasma urealyticum.
Ureaplasma urealyticum, which is the correct response, is considered a mycoplasma. Ureaplasma urealyticum is in the family Mycoplasmataceae and the genus Ureaplasma. Bacteria in the genus Ureaplasma require urea. Ureaplasma urealyticum is found primarily in the genitourinary tract. Ureaplasma urealyticum is a common cause of nongonococcal urethritis.
Chlamydia are bacteria, not mycoplasma. Chlamydia was once thought to be protozoa as well as viruses, but it is neither. They are bacteria in the order Chlamydiales. Chlamydia is obligate intracellular organisms. Characteristic of chlamydia infections is the development of inclusion bodies. Chlamydia trachomatis cause approximately 30-40% all cases of nongonococcal urethritis in males. Chlamydia trachomatis causes more nongonococcal urethritis in males than does Trichomonas vaginalis.
Chlamydophila psittaci does not cause nongonococcal urethritis. Chlamydophila psittaci causes a systemic illness called psittacosis, parrot fever, or ornithosis. Psittacosis is acquired from birds.
Trichomonas vaginalis is a protozoan. Trichomonas vaginalis can cause nongonococcal urethritis in males. It also causes trichomoniasis vaginitis, sometimes called trichomoniasis.
Pneumocystis jirovecii (formerly called Pneumocystis carinii) is a fungus, not mycoplasma. In an immunosuppressed host, Pneumocystis jirovecii can cause pneumonia. Pneumocystis jirovecii does not cause nongonococcal urethritis.

Question 35

Case
A 14-year-old boy enjoys taking his dog into the woods on hikes during his summer break from school. One day, the boy suddenly becomes ill. He complains of headache, chills, and muscle aches. His mother takes his temperature, and notes that he is febrile. He develops a maculopapular rash with petechiae. The wrist, ankles, palms of the hand, and soles of the feet are initially affected. The rash progresses to his trunk.

What is the most likely cause of his complaints?

1 Rickettsia rickettsii

2 Rickettsia conori

3 Borrelia hermsii

4 Babesia microti

5 Borrelia burgdorferi

Answer 35

Rickettsia rickettsii

Rickettsia rickettsii is transmitted by ticks. It is the cause of Rocky Mountain spotted fever. Rickettsias are obligate intracellular organisms. Symptoms of Rocky Mountain spotted fever include a characteristic rash, headache, chills, and fever. The rash initially involves the wrist, ankles, palms of the hand, and soles of the feet.
Rickettsia conori is transmitted by ticks. It is the cause of Boutonneuse fever. Rickettsias are obligate intracellular organisms. Boutonneuse fever is also called tick typhus.
Borrelia hermsii is transmitted by ticks. It is a cause of relapsing fever. Relapsing fever can occur wherever there are soft ticks. Relapsing fever can be caused by several types of Borrelia. Borrelias are spirochetes. Spirochetes are motile, spiral shaped microbes.
Babesia microti is transmitted by ticks. It is the cause of babesiosis. Babesia microti is a parasite of red blood cells. Symptoms of babesiosis include fever, anemia, and hemoglobulinuria. This is primarily a disease of animals. Human infection can occur, but it is rare.
Borrelia burgdorferi is transmitted by ticks. It is the cause of Lyme disease. Borrelia burgdorferi is classified as a spirochete. Spirochetes are motile, spiral shaped microbes.

Question 36

A teenager goes on a camping trip with his friends. Unfortunately, a soft tick attaches to his ear. When he returns home, he becomes abruptly ill. He has constant fever and chills. He sees his family doctor. He is found to be febrile, with a temperature of 39.5°C. His heart rate is 110. It turns out that he has relapsing fever. What is the most likely cause of his illness?

1 Rickettsia rickettsii
2 Rickettsia conori
3 Borrelia hermsii
4 Babesia microti
5 Borrelia burgdorferi

Answer 36

Borrelia hermsii

Borrelia hermsii is transmitted by ticks. It is a cause of relapsing fever. Relapsing fever can occur wherever there are soft ticks. Relapsing fever can be caused by several types of Borrelia species. Borrelias are spirochetes. Spirochetes are motile, spiral shaped microbes.
Rickettsia rickettsii is transmitted by ticks. It is the cause of Rocky Mountain spotted fever. Rickettsias are obligate intracellular organisms. Symptoms of Rocky Mountain spotted fever include a characteristic rash, headache, chills, and fever. The rash initially involves the wrist, ankles, palms of the hand, and soles of the feet.
Rickettsia conori is transmitted by ticks. It is the cause of Boutonneuse fever. Rickettsias are obligate intracellular organisms. Boutonneuse fever is also called tick typhus.
Babesia microti is transmitted by ticks. It is the cause of babesiosis. Babesia microti is a parasite of red blood cells. Symptoms of babesiosis include fever, anemia, and hemoglobulinuria. This is primarily a disease of animals. Human infection can occur, but it is rare.
Borrelia burgdorferi is transmitted by ticks. It is the cause of Lyme disease. Borrelia burgdorferi is classified as a spirochete. Spirochetes are motile, spiral shaped microbes.

Question 37

A 43-year-old cattle rancher develops a severe headache, fever and chills. He has complaints of malaise and muscle pain as well. He sees his family doctor. On physical examination, he is found to have a temperature of 39.2 C. There is no rash present. His liver is slightly enlarged. Diagnostic tests are done, and there is a five-fold rise in titer of complement fixing antibodies. He is diagnosed with Q fever. What is the causative agent of Q fever?

1 Brucella abortus
2 Coxiella burnetii
3 Brucella Suis
4 Borrelia burgdorferi
5 Rickettsia prowazekii

Answer 37

Coxiella burnetii

Q fever is an acute illness that is caused by the Rickettsia Coxiella burnetii. It is transmitted to humans from exposure to infected livestock. The symptoms that this male experienced are consistent with Q fever: fever, chills, headache, muscle pain, and malaise. Endocarditis can be a complication of Q fever.
Brucella is a non-motile gram-negative rod. They do not form spores. The disease caused by Brucella is called Brucellosis. Brucellosis can be caused by Brucella Suis, Brucella abortus, Brucella melitensis, and Brucella canis. Malta is where Brucellosis infection was originally documented. Therefore, brucellosis is sometimes called Malta fever. Brucella abortus is not the cause of Q fever. Brucella abortus is one of the causes of brucellosis. Brucella abortus generally infects cattle and it can then be transmitted to humans. Brucella Suis is not the cause of Q fever. Brucella Suis is one of the causes of brucellosis. Brucella Suis generally infects pigs and it can then be transmitted to humans.
Borrelia burgdorferi is not the cause of Q fever. Borrelia burgdorferi is the cause of Lyme disease. This is transmitted to humans by a tick bite, specifically by deer ticks (Ixodes ticks). Borrelia burgdorferi is classified as a spirochete. Some of the symptoms that can be seen with Lyme disease include arthritis, bull’s eye rash and fatigue, chills and fever, headache, and muscle pain.
Rickettsia prowazekii is not the cause of Q fever. Rickettsia prowazekii is the cause of epidemic typhus. This is transmitted to humans by the human body louse. War, poverty, crowding, famine, and unsanitary conditions predispose to the occurrence of epidemic typhus. Some of the symptoms of epidemic typhus include rash, headache, chills, delirium, and high fever.

Question 38

A 43-year-old cattle rancher develops a severe headache, fever and chills. He has complaints of malaise and muscle pain as well. He sees his family doctor. On physical examination, he is found to have a temperature of 39.2 C. There is no rash present. His liver is slightly enlarged. Diagnostic tests are done, and there is a five-fold rise in titer of complement fixing antibodies. He is diagnosed with Q fever. What can be a complication of Q fever?

1 Vasculitis
2 Splenomegaly
3 Endocarditis
4 Thrombocytosis
5 Meningitis

Answer 38

Endocarditis

Q fever is an acute illness that is caused by the Rickettsia Coxiella burnetii. It is transmitted to man from exposure to infected livestock. The symptoms that this male experienced are consistent with Q fever: fever, chills, headache, muscle pain, and malaise. Endocarditis can be a complication of Q fever.
Vasculitis is an inflammation of the blood vessels. Both arteries and veins can be affected by vasculitis. Numerous diseases can result in vasculitis; however, vasculitis is not a complication of Q fever.
Splenomegaly refers to an enlarged spleen. Numerous conditions can result in splenomegaly. Some of the diseases that can result in splenomegaly include chronic myelogenous leukemia, malaria, and Gaucher’s disease. Many other diseases can result in splenomegaly. However, splenomegaly is not a complication of Q fever.
Thrombocytosis is an increase in the platelet count. A complication of thrombocytosis is a hypercoagulable state that can lead to venous thrombosis. Some conditions in which a thrombocytosis can be seen include idiopathic thrombocythemia, myeloproliferative syndrome, and chronic inflammatory conditions. There are other causes of thrombocytosis as well. However, thrombocytosis is not a complication of Q fever.
Meningitis is an inflammation and infection of the meninges. Bacteria, virus, and fungus can all cause meningitis. Examples of bacteria that can lead to meningitis include Streptococcus pneumoniae (pneumococcus), Neisseria meningitidis (meningococcus), and H. influenzae. An example of a fungus that can cause meningitis is Cryptococcus neoformans. Meningitis is not a complication of Q fever.