10 Non-enteric Gram Negative Rods (25) Flashcards
Case
A 55-year-old man was brought to the emergency department with a 2-day history of high fever, chills, malaise, productive cough, dyspnea, and diarrhea. He has been diabetic for the last 5 years. He is a tobacco smoker for more than 30 years. This patient was on a Caribbean cruising during the previous week and had spent a few hours in the whirlpool spa. He started feeling ill the day after his return. Clinical and radiographic findings were suggestive of atypical pneumonia. The clinician considered Legionella infection as a possible cause of the pneumonia taking into account the patient’s history of travel and association with whirlpool spa. He sent clinical samples from the patient for microbiological investigations, which included blood, sputum, and urine. Based on a report received within 2 hours of sending the specimens, the clinician diagnosed the disease as pneumonia due to Legionella pneumophila group 1.
Which of the following tests helped him to make this early diagnosis?
1 Gram stain of sputum
2 Culture of sputum on BCYE medium
3 Blood culture
4 Serological test for IgM antibodies
5 Urinary antigen assay
Urinary antigen assay
Urinary antigen assay is a rapid and very useful test for making early diagnosis of pneumonia due to Legionella pneumophila. The test has good specificity and sensitivity. It detects a heat stable antigen, which is a component of the lipopolysaccharide portion of the cell wall of the organism. The antigen can be detected in urine as early as within 3 days after the onset of symptoms. Tests based on enzyme-linked immunosorbant assay (ELISA) and radioimmuno assay (RIA) are available. The most recent and rapid method is the immunochromatographic (ICT) membrane assay with which results can be obtained in 15 minutes. Concentrating the urine sample increases the sensitivity of the test.
Legionella infection (legionellosis) can present as Legionnaire’s disease, a severe multisystem disease with pneumonia or a mild self-limiting flu-like illness called Pontiac fever.
Legionella pneumophila is a ubiquitous gram-negative intracellular bacterium found widely in warm moist environment. The bacterium survives temperatures up to 63 degrees centigrade. It can survive water treatment processes. Small number of organisms may enter the water distribution systems where they proliferate. Legionellae are found to survive in biofilms that form in building water systems. Of the 15 serogroups, Legionella pneumophila serogroup 1 is responsible for most cases of legionellosis in the United States. In susceptible hosts infection commonly follows inhalation of bacteria from aerosols generated from man-made aquatic environments such as contaminated air-conditioning systems, cooling towers, and whirlpool spas. Risk factors include immunosuppression or immune system disorders, diabetes mellitus, systemic malignancies, chronic lung disease, and heavy smoking. The organisms are known to cause community-acquired sporadic infections, outbreaks, and travel associated as well as nosocomial outbreaks. Maintaining water systems at temperatures unfavorable for amplification of legionellae and use of effective biocides help to control transmission of infection. Azithromycin and levofloxacin are preferred antibiotics for treatment of Legionnaire’s disease.
Gram stain of sputum does not help to detect Legionella. Sputum is often nonpurulent and contains very few polymorphonuclear leukocytes. Legionella stains poorly by gram stain. Basic fuchsin has to be used as counterstain so as to stain these gram-negative pleomorphic bacilli. Direct Fluorescent Antibody tests can be useful for detecting legionella in clinical specimens such as respiratory secretions.
Culture on BCYE medium (buffered charcoal yeast extract medium) enriched with alpha ketoglutarate and containing antibiotics to make it selective is used for isolation of Legionella organisms from sputum. Cultural isolation and identification is a time consuming procedure though it remains the gold standard for diagnosis. Immediate culture of the sample is required for isolation of the bacteria, as they survive poorly in respiratory secretions. They grow slowly on the culture medium and visible colonies are detected after 3 days incubation. Immunofluorescent staining can be used for identifying the isolate. Bronchial Alveolar Lavage (BAL) is considered as better specimen than sputum for isolation of legionella. PCR procedures have been developed for direct detection of legionella in clinical specimens. In outbreak settings, cultural isolation and characterization of the organism is important in order to trace the source of infection.
Blood culture is usually done using a biphasic BCYE medium and it takes 2 or more weeks to detect growth. Growth appears on the agar surface of the medium and has to be identified by conventional methods.
Serological test for IgM antibodies: Delay in the development of measurable antibody response limits its usefulness in the diagnosis of acute patients. Antibody levels rise slowly during the illness. Testing of paired sera (acute and convalescent) and demonstration of 4-fold or higher rise in antibody titer is helpful for diagnosis. Indirect immunofluorescence test, rapid microagglutination test, and ELISA test have been evaluated and found most useful for retrospective diagnosis in outbreak situations. Recent studies have shown that IgM detection by ELISA in single serum sample can be a suitable complement to antigenuria detection for diagnosis of legionellosis.
Case
A 75-year-old woman was hospitalized with a localized subcutaneous abscess at the site of a cat bite. Pus drained from the abscess was cultured in the microbiology laboratory. Colonies of small Gram-negative coccobacilli grew on chocolate agar incubated at 37°C for 24 hours. The bacterium was non-motile, oxidase and catalase positive, urease negative, and showed fermentative activity on carbohydrates.
The isolate is most likely to be what zoonotic pathogen?
1 Bartonella henselae
2 Ehrlichia chaffeensis
3 Coxiella burnetii
4 Pasteurella multocida
5 Bordetella bronchiseptica
Pasteurella multocida
The majority of infections involves skin and subcutaneous tissue. Rapid onset of wound infection and development of cellulitis or abscess at the site of the bite is very characteristic. Among the listed zoonotic pathogens, Pasteurella multocida is the only bacterium possessing the described characteristics of the isolate. The bacterium is part of the normal flora of cats, dogs, and other domestic and pet animals. Human infection often follows bite, scratches, or licks from these carrier animals. Increased carriage rates have been observed in cats. Infections following cat bites and scratches are more common.
P.multocida can also cause bacteremia, meningitis, pneumonia, septic arthritis, osteomyelitis, endocarditis, peritonitis, sinusitis, and urinary tract infection. Persons in extremes of age and immunocompromised individuals, including those with liver cirrhosis, renal disease, hematological malignancies, and post-transplant patients, are at risk for more severe invasive disease by P.multocida. P.multocida causes a wide variety of diseases in animals such as fowl cholera in poultry, atrophic rhinitis in pigs, and bovine respiratory diseases and hemorrhagic septicemia in cattle. Key virulence factors of P.multocida are its capsule and lipopolysaccharide. Some strains associated with atrophic rhinitis in pigs are toxigenic. ToxA gene, the structural gene for P.multocida toxin (PMT), resides in a prophage. Antibiotics including beta-lactams, tetracyclines, and fluoroquinolones are used for treating P.multocida infections. Clindamycin and erythromycin are not recommended. Beta-lactamase producing P.multocida strains have been reported from human infections, though very rarely.
Bartonella henselae, the agent of “cat scratch disease” (CSD), is a fastidious Gram-negative bacterium, and cultural isolation on chocolate agar requires a minimum of 3 weeks of incubation. It gives negative catalase, oxidase, and carbohydrate utilization tests. CSD is often self-limited. Typical clinical presentation is fever and lymphadenopathy developing about 2 weeks after contact with a cat. B.henselae is associated with bacillary angiomatosis also.
Ehrlichia chaffeensis causes human monocyte ehrlichiosis and is transmitted by ticks. E.chaffeensis and Coxiella burnetii, the organism of Q fever, are strictly intracellular and fail to grow on cell-free media. C.burnetii is transmitted among animals by ticks. Humans acquire infection mostly by inhalation of contaminated aerosols and also by drinking unpasteurized milk.
Bordetella bronchiseptica occurs as commensals in the upper respiratory tract of many wild and domestic animals. The bacterium is motile with peritrichous flagella. Human infections are very rare.
Which one of the following organisms requires both factor X (a heme compound) and factor V (nicotinamide adenine dinucleotide) in chocolate agar?
1 Haemophilus influenzae
2 Haemophilus parainfluenzae
3 Haemophilus ducreyi
4 Bordetella pertussis
5 Klebsiella pneumoniae
Haemophilus influenzae
Haemophilus influenzae requires both factor X (a heme compound) and factor V (nicotinamide adenine dinucleotide) in chocolate agar. Haemophilus parainfluenzae, Haemophilus parainfluenzae, Haemophilus ducreyi, Bordetella pertussis and Klebsiella pneumoniae do not require heme and NAD for growth.
The type b serotype of Haemophilus influenzae causes most of the severe diseases, such as meningitis and sepsis. The type b capsule is composed of
1 D-glutamate
2 Peptidoglycan
3 Teichoic acids
4 Lipopolysaccharide
5 Polyribitol phosphate
Polyribitol phosphate
The type b capsule of Haemophilus influenzae is composed of polyribitol phosphate. The anti-phagocytic capsule of Bacillus anthracis is unique in that it is composed of D-glutamate. Peptidoglycan is composed of peptides and sugars that are found in bacterial cell walls. Teichoic acids are polymers of glycerol phosphate or ribitol phosphate located in the outer layer of the cell wall of gram-positive bacteria. Lipopolysaccharides are present in the outer layer of the cell wall of gram-negative bacteria.
The feature of Legionella pneumophilia that accounts for the difficulty in isolating the organism during the 1976 outbreak at the American Legion Convention is
1 Growth at only 42 ° C
2 Requirement for a high iron and cysteine concentration in culture medium
3 Requirement for anaerobic conditions for growth
4 Requirement for acid conditions for growth
5 Requirement for basic conditions for growth
Requirement for a high iron and cysteine concentration in culture medium
The feature of Legionella pneumophilia that accounts for its difficulty in isolating the organism during the 1976 outbreak at the American Legion Convention is requirement for a high iron and cysteine concentration in culture medium. Legionella pneumophilia does not grow at only 42 C or require acidic or basic conditions for growth.
The main reservoir for tick-borne tuaremia is
1 Deer
2 Rabbits
3 Rat flea
4 Wild rodents
5 Lice
Rabbits
Tularemia is caused by Francisella tularensis. The main type of tularemia in the USA is tick-borne tularemia from a rabbit reservoir.
Which one of the following organisms is transmitted by ingestion of contaminated milk?
1 Brucella melitensis
2 Yersinia pestis
3 Francisella tularensis
4 Pasteurella multocida
5 Vibrio cholerae
Brucella melitensis
Brucella melitensis is spread by ingestion of contaminated dairy products or contaminated animal tissues. Yersinia pestis is spread by flea bites. Francisella tularensis is spread by contact with infected animal tissues and ticks. Pasteurella multocida is spread by cat or dog bites. Vibrio cholerae is spread by fecal contamination of water and food.
Cogntive Level: Understand
Case
A 28-year-old man presents with a lesion on his left arm that is getting worse. It has been there for 3 days. He also says that he has muscle aches, fatigue, and malaise, but he thinks that it is because he was on a camping trip last week and all that he ate was a rabbit and some chocolate bars. On physical exam, there is an ulcer with transparent exudates and an axillary lymphadenopathy. The rest of the exam is normal.
What bacteria is the most likely cause of his infection?
1 Bordetella pertussis
2 Borrelia Burgdorferi
3 Brucella
4 Francisella tularensis
5 Rickettsia rickettsii
Francisella tularensis
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.
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.
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.
Case
An outbreak of respiratory illness occurred in a day-care center involving children who had not completed the primary vaccination series. The illness was characterized by catarrhal symptoms followed by paroxysmal cough. The etiological agent of the outbreak was a small Gram-negative coccobacillus that was isolated from the nasopharyngeal aspirates of children in the early phase of the illness. Bordet Gengou medium was the selective medium used for isolating the bacterial agent.
What is a characteristic of this bacterial species that caused the outbreak?
1 Is motile with peritrichous flagella
2 Rodents are natural reservoirs
3 Requires X and V factors for growth
4 Is an obligate anaerobe
5 Can produce symptomatic infection in adults
6 Is an important cause of meningitis in newborns
Can produce symptomatic infection in adults
The case description is suggestive of an outbreak of pertussis (whooping cough) in the day-care center caused by Bordetella pertussis.
Though pertussis was considered as a childhood disease, especially in the prevaccine era, it is observed that Bordetella pertussis can produce symptomatic infection in adults and adolescents as well.
Other features listed are not characteristics of B.pertussis. B.pertussis is aerobic, non-motile, and does not require X and V factors for growth. The bacterium is not systemically invasive and is not found to disseminate beyond the respiratory tract, and hence is not an important cause of meningitis in newborns.
An increase in the incidence of infection by B.pertussis in adolescents and adults has been noticed during the last 15 years. Immunity from natural infection or immunization wanes in 5-10 years. This is considered as a significant reason for the increase in incidence in adults and adolescents. Infection by B.pertussis in adults and adolescents often goes unrecognized because a persistent uncharacteristic cough might be the only presenting symptom. When such individuals with protracted cough seek medical advice, it is often too late to diagnose by culture or polymerase chain reaction (PCR) assay.
This under-diagnosis/missed diagnosis becomes a significant public health problem, as infected adults and adolescents can be major reservoirs and source of transmission to infants who are unimmunized or not fully immunized. Hospital-acquired pertussis outbreaks in newborns have been documented. Mothers or health care workers with B.pertussis infection have been identified as sources of infection for these outbreaks.
Serological test using ELISA is considered to be a useful tool in diagnosing B.pertussis infection, particularly among older patients presenting late in the course of their illness when culture and PCR tests are negative. Serology is less helpful during acute illness.
Tdap (tetanus, diphtheria, and pertussis) vaccines for immunization of adolescents and adults have been licensed for use in the U.S.
Case Highlights
A 33-year-old man presents with left-sided chest pain and difficulty breathing; the symptoms have been present for a few days. He reports a pain intensity of 10 on a scale of 0-10, and he describes the pain as sharp and sudden. He has a non-productive cough.
His tympanic temperature reading is 102.3°F, peripheral pulse rate is 120 bpm, respiratory rate is 28/min, blood pressure is 106/44 mm Hg, and oxygen saturation is 88%. He has diminished breath sounds in all lobes.
His medical history is significant for a history of recreational heroin and cocaine use, as well as a recent uncomplicated appendectomy.
Radiographic studies of his lungs and cardiac studies are unremarkable. His ALT and AST are slightly elevated. The CBC results are significant for a WBC of 22.1 x 103 cells/cm, with an elevated granulocytic left shift differential count.
Purulent sputum is collected from the patient and sent to the laboratory; 2 sets of blood cultures are also sent. The initial Gram stain of the sputum results in a specimen that has many WBCs, no epithelial cells, and many Gram-negative coccobacilli. The blood culture is subsequently positive after 6 hours incubation for Gram-negative coccobacilli (see image). Both cultures produce an organism that grows only on chocolate agar media, has a characteristic musty odor, and is nitrate-positive, catalase-positive, and H2S-negative.
This patient is diagnosed with pneumonia with secondary bacteremia due to what organism?
1 Haemophilus influenzae
2 Pasteurella multocida
3 Moraxella catarrhalis
4 Vibrio vulnificus
5 Eikenella corrodens
Haemophilus influenzae
Haemophilus influenzae is a facultative anaerobic, Gram-negative coccobacillus, which requires the presence of X factor (hemin) and V factor (nicotinamide adenine dinucleotide [NAD]) for growth. For this reason, the organism will only grow on chocolate agar media that is made with blood that has been heated to induce lysing of the red blood cells and in turn release the needed factors into the agar media. The organism has a characteristic musty smell on chocolate agar media. H. influenzae can produce any of several clinical syndromes, including meningitis, bacteremia, epiglottitis, and pneumonia. Vaccination of small children is an effective tool in preventing Haemophilus infections.
Pasteurella multocida is a Gram-negative, oxidase-positive rod that will characteristically grow on blood agar plate (BAP) and chocolate agar but not on MacConkey agar. The organism is part of the normal oral flora of dogs and cats, and it is associated with cat and dog bite wound infections. The organism is commonly mistaken for Haemophilus species, but it is easily distinguished by its ability to grow on BAP and chocolate agar media; Haemophilus species will only grow on chocolate agar media.
Moraxella catarrhalis, which was formerly called Branhamella catarrhalis, causes acute, localized infections, such as otitis media, sinusitis, and bronchopneumonia; it also causes life-threatening systemic diseases, including endocarditis and meningitis. The organism is a Gram-negative diplococci; it is oxidase positive, has a slight pink pigment, is catalase positive, and it is usually positive for the production of the beta-lactamase enzyme. The organism characteristically produces butyrate esterase, and the detection of this enzyme will provide a rapid identification.
Vibrio vulnificus normally lives in warm seawater and is part of a group of vibrios that are called “halophilic” because they require salt. It is a Gram-negative rod that is oxidase positive and motile by means of polar flagella. It is characteristically lactose positive. Infections with the organism are generally due to ingestion of raw oysters and/or exposure of traumatic wounds to infected marine animals or contaminated water. TCBS (thiosulfate citrate bile salts sucrose) agar is the agar media of choice in isolating the organism. The organism can cause life-threatening septicemia (40-60% mortality) and painful wound infections with considerable skin and muscle necrosis.
Eikenella corrodens, which was formerly called Bacteroides ureolyticus, is a facultative anaerobic, Gram-negative bacterium; it is a normally occurring inhabitant of the oral cavity, and it is often one of the pathogens associated with infected human bite wounds. Characteristically, the organism will pit the agar and produce a strong hypochlorite odor.
Case
A 25-year-old man presents with pain and swelling of his left hand and arm. He reports having been bitten by a dog on the left hand 3 days prior to presentation. The wound undergoes debridement, and material is collected for Gram-stain and culture. The Gram-stain result is significant for the presence of many polymorphonuclear cells (PMNs) and small Gram-negative rods. The patient is discharged after a course of intravenous antibiotic therapy with a 10-day supply of oral antibiotics. He is instructed to call the office immediately if symptoms worsen and to return for a follow-up visit after his 10 days of antibiotic therapy.
The culture was significant for the growth of Gram-negative rods (see image) that grew on blood and chocolate agar media, but not on MacConkey agar media. The organism was oxidase-positive, catalase-positive, indole-positive, and urease-negative.
The clinical history and preliminary laboratory results point to an infection due to what organism?
1 Haemophilus influenza
2 Pasteurella multocida
3 Moraxella catarrhalis
4 Vibrio vulnificus
5 Eikenella corrodens
Pasteurella multocida
Pasteurella multocida is a Gram-negative, oxidase-positive rod that will characteristically grow on blood agar plate (BAP) and chocolate agar, but not on MacConkey agar. The organism is part of the normal oral flora of dogs and cats, and it is associated with cat and dog bite wound infections. The organism is commonly mistaken for Haemophilus species but is easily distinguished by its ability to grow on BAP and chocolate agar media; Haemophilus species will only grow on chocolate agar media.
Haemophilus influenza is a facultative anaerobic, Gram-negative coccobacillus that requires the presence of X factor (hemin) and V factor (nicotinamide adenine dinucleotide [NAD]) for growth. For this reason, the organism will only grow on chocolate agar media, which is made with blood that has been heated to induce lysing of the red blood cells, and in turn, releases the needed factors into the agar media. The organism has a characteristic musty smell on chocolate agar media.
Moraxella catarrhalis, which was formerly called Branhamella catarrhalis, causes acute, localized infections such as otitis media, sinusitis, and bronchopneumonia as well as life-threatening systemic diseases including endocarditis and meningitis. The organism is a Gram-negative diplococci; it is oxidase-positive, has a slight pink pigment, is catalase-positive, and is usually positive for the production of the beta-lactamase enzyme. The organism characteristically produces butyrate esterase, and the detection of this enzyme will provide a rapid identification.
Vibrio vulnificus normally lives in warm seawater and is part of a group of vibrios that are called “halophilic” because they require salt. It is a Gram-negative rod that is oxidase-positive and motile by means of polar flagella. Characteristically, it is lactose-positive. Infections with the organism are generally due to ingestion of raw oysters and/or exposure of traumatic wounds to infected marine animals or contaminated water. TCBS (thiosulfate citrate bile salts sucrose) agar is the agar media of choice in isolating the organism. The organism can cause life-threatening septicemia (40-60% mortality) and painful wound infections with considerable skin and muscle necrosis.
Eikenella corrodens, formerly called Bacteroides ureolyticus, is a facultative anaerobic, Gram-negative bacterium; it is a normally-occurring inhabitant of the oral cavity, and it is often one of the pathogens associated with infected human bite wounds. The organism characteristically will pit the agar and produce a strong hypochlorite odor.
Tommy is usually an active 2-year-old. Today, he is abruptly lethargic, drooling, and has a temperature of 105 degrees Farenheit. The most likely organism causing his illness is
1 Bordetella pertussis
2 Influenza
3 Hemophilus influenzae
4 Adenovirus
5 Herpes zoster
Hemophilus influenzae
Hemophilus influenzae Type B typically affects children of age 2 and under. The onset is rapid, with sore throat and high fever. The epiglottis undergoes severe swelling until it is bright red and stiff, which can cause death due to obstruction of the airway. Usually the child struggles to breathe and often leans forward and drools. Attempts to move the epiglottis are contraindicated, as this may precipitate acute respiratory failure. Hemophilus influenzae may also present in other ways, including: meningitis, pyarthrosis, pneumonia, cellulitis, pericarditis, and bacteremia without any evidence of localized disease.
Bordetella pertussis is a small gram negative coccobacillus, which causes whooping cough. Half of the cases occur in children under the age of 2. There are usually three stages to the infection: the first stage demonstrates moderate upper respiratory symptoms, such as sneezing, lacrimation, and a hacking cough, particularly in the evening. There is no significant fever. The second stage is the most pathognomonic, as the patient coughs sequentially 5-15 times, followed by a whooping inspiration (hence the name whooping cough). This stage develops at about 10-14 days from onset of the infection. The last stage occurs around 4 weeks from onset and is the recuperative phase. There is diminishing cough, and the patient begins to improve.
Influenza is caused by Influenza Type A, B, or C, which are orthomyxoviruses containing a core of RNA and soluble nucleoprotein antigens enclosed by a membrane. There are numerous strains of influenza and frequent mutations within these organisms. The three most common influenza strains are A, B, and C. Children of school age are most likely to contract influenza via airborne droplets, usually in the late fall or early winter. Influenza A is most prevalent and also potentially the most deadly of the strains. Incubation is brief, within 48 hours. Symptoms come on abruptly, including fever of 102-103 F, chills, aching of the back and legs, headache, and sore throat. This typically evolves to a non-productive cough, injected conjunctivae, and red throat without exudates. Symptoms usually last 2-3 days, although fever may persist for up to 5 days. In rare occasions, influenza can lead to pneumonia and/or hemorrhagic bronchitis, usually in immunocompromised hosts (i.e. lung, cardiac, or neurologic disease). Neurologic or cardiac complications are rare manifestations in influenza.
Adenovirus has at least 40 different serotypes. It is a DNA iscosahedral shaped organism. Infants in the first month of life are the target of serotypes 1, 2, and 5.
This outbreak is usually limited to the respiratory or gastrointestinal tract. Type 3 attacks older children and adults. It often resides in pools and summer camps. The symptoms with this strain include conjunctivitis, fever, and sore throat. Adenovirus types 4 and 7 may also cause acute respiratory distress syndrome (ARDS) in military boot camps, typically in either the winter or spring. In children, water-borne exposure can cause fever, pharyngoconjunctivitis, tracheitis, bronchitis, and non-productive cough similar to whooping cough. In rare instances, respiratory tract infections may progress to pneumonia.
Herpes zoster is a virus that causes chickenpox. It can also cause shingles in adults who were exposed to this organism in childhood and now have a compromised immune system or direct exposure to someone actively shedding this organism. Normally, the organism lies dormant in the sensory ganglia adjacent to the spinal cord. When activated, the replicating viral particles migrate down the nerves from the ganglia to the skin where they trigger the formation of red papules, which rapidly form coalescing blisters. The blisters typically are located within the distribution of the sensory nerve infected with the virus. After 5 days or so, the vesicles scab over, but depending on the depth and extent of the infection, there may be residual scarring. In rare instances, particularly in immunocompromised patients, the rash may become generalized. In older adults, there is the possibility of developing a postherpetic neuralgia, which occurs after the initial rash clears. This painful condition may last weeks or months and sometimes persists indefinitely. Patients may become bed-ridden and fail to thrive due to the intensity of the pain. Consulting a pain management specialist may be necessary to provide suffering patients needed pain relief.
Which characteristic of Pasteurella multocida is correct?
1 Gram positive coccobacillus
2 Associated with cellulitis
3 Motile with polar flagellum
4 Oxidase negative
Associated with cellulitis
Pasteurella multocida is gram negative pleomorphic coccobacilli. It is associated with cellulitis resulting from bites or scratches of dogs or cats. Based on capsular antigen it is divided into five serogroups, A, B, D, E, and F.
Additional characteristics of Pasteurella multocida includes the following:
Non motile
Facultative anaerobe
Oxidase positive
Catalase positive
Gives “sick” TSI reaction by weak acid production from glucose and no gas
Non hemolytic on blood agar
Which of the following etiological agents corresponds with acute epiglottitis?
1 Bordetella pertussis
2 Haemophilus ducreyi
3 Haemophilus influenzae
4 Legionella pneumophilia
5 Yersinia pestis
Haemophilus influenzae
Acute epiglottitis is a rapidly progressive infection of epiglottis and the surrounding soft tissue present in the upper airway. The edema caused by epiglottitis can lead to upper airway obstruction and respiratory arrest. Other infections caused by Haemophilus influenzae type b includes sinusitis, arthritis, otitis media, meningitis, cellulitis, conjunctivitis, bronchitis and pneumonia.
Which of the following etiological agents corresponds with whooping cough?
1 Bordetella pertussis
2 Haemophilus ducreyi
3 Haemophilus influenzae
4 Legionella pneumophilia
5 Yersinia pestis
Bordetella pertussis
Whooping Cough is the term used in reference to the respiratory tract infection caused by Bordetella pertussis. It is associated with the characteristic “ whoop” upon inhalation and can lead to vomiting, cyanosis, and convulsions. Bordetella pertussis is small gram negative coccobacilli. Infection from this organism can be prevented by administration of DTP vaccine during the first year of infants. DTP vaccine contains pertussis vaccine as a crude suspension of bacteria along with toxoids of diphtheria and tetanus.
