S1B5 - Degenerate Bacteria Flashcards
What organism causes Q fever?
Coxiella burnetii is morphologically similar to Rickettsia but is no longer included in the Rickettsia family and causes Q fever.
What are the clinical presentations of Q fever? Chronic infection can lead to what sequelae?
Q fever can present with
- Self-limited flu-like illness
- Atypical pneumonia
- Hepatitis accompanied by prolonged fever of unknown origin with granulomas on biopsy
- Culture-negative endocarditis (in chronic infections). Bartonella hensalae can also be a cause of culture-negative endocarditis.
What organism is responsible for scrub typhus? What is the vector for this organism?
Orientia tsutsugamushi is another intracellular parasite from the Rickettsia family that is transmitted by trombiculid mites (“chiggers”), and is responsible for scrub typhus found in Asia and the South Pacific.
How is Coxiella burnetii transmitted?
C. burnetii is carried in cattle, sheep, and goats and is shed and survives as spores in animal products. Commonly associated with cattle and sheep amniotic fluid. Transmission occurs through inhalation of spores.
What is the motility, spore-forming, gram-staining, and morphology of Rickettsia organisms?
Rickettsia is a genus of non-motile, non-sporeforming, weakly gram-negative, highly pleomorphic bacteria.
What are the symptoms of ehrlichiosis and anaplasmosis? What makes it different from Rocky Mountain Spotted Fever?
Ehrlichiosis and anaplasmosis is similar to the presentation of RMSF, however infected patients present without a rash. In addition, patients have
- Thrombocytopenia
- Morulae (mulberry-shaped aggregates of organisms within a phagosome)
- Leukopenia
What cells do Ehrlichia and Anaplasma infect?
Ehrlichia and Anaplasma are obligate intracellular bacteria of mononuclear or granulocytic phagocytes.
Serum from a patient is tested for agglutinins against a panel of O-antigens (Weil-Felix reaction). Infection by which of the following would not be detected by this test?
A) Rickettsia prozazekii
B) Rickettsia typhi
C) Rickettsia ricketsii
D) Orientia tsutsugamushi
E) Coxiella buirnettii
Coxiella burnetii
Answer Explanation
C. burnetii causes Q fever, the only disease in which the Weil-Felix reaction won’t be positive. R. rickettsii causes Rocky Mountain spotted fever. The other 3 species cause various forms of typhus.
What is the main diagnostic test for rickettsial diseases and vector-born illnesses?
Diagnosis can be made via serology using the indirect fluorescent antibody (IFA) test.
What vector transmits Rocky Mountain Spotted Fever?
R. rickettsii is carried in dogs and rodents and is transmitted to humans from the bite of the Dermacentor wood or dog tick.
What are the symptoms of Rocky Mountain Spotted Fever?
Symptoms of RMSF include an acute onset of fever, headache, and myalgias. 2-6 days after onset a petechial rash starts on the ankles and wrists and spreads to the trunk. Rash that appears on the palms and soles is highly characteristic of RMSF, but usually occurs in later stages.
What property of Rickettsia makes it hard to diagnose?
Rickettsia spp. are obligate intracellular parasites, which make them difficult to diagnose.
What is the causative organism of Rocky Mountain spotted fever?
R. rickettsii causes Rocky Mountain Spotted Fever (RMSF), an infection of endothelial cells.
Where is the incidence of anaplasmosis highest in the United States?
Anaplasmosis occurs more often in the Northeast and upper Midwest.
What is the treatment for all rickettsial diseases and vector-born illnesses?
Treatment for all rickettsial diseases and vector-borne illnesses is doxycycline. Chloramphenicol may be used as an adjunct therapy.
What is the vector of Ehrlichia and what cell does it infect?
Ehrlichia is transmitted by the Lone star tick and is characterized infection of monocytes and macrophages.
What vector transmits R. typhi?
R. typhi is carried usually in rats and transmitted to humans from feces of fleas.
What vector transmits R. prowazekii?
R. prowazekii is transmitted from the feces of lice.
What is the classic triad of symptoms common to all Rickettsial diseases?
Rickettsial diseases usually clinically present as a classic triad of
- Headache
- Fever
- Rash
What is the vector of Anaplasma and what cell does it infect?
Anaplasma is transmitted by the Ixodes tick and is characterized by infection of neutrophils.
What diseases do Ehrlichia and Anaplasma cause?
Ehrlichia and Anaplasma are gram-negative bacilli that causes ehrlichiosis and anaplasmosis, respectively.
Describe the time course and symptoms of typhus.
Symptoms of typhus include an incubation of 8-16 days. The onset of illness is usually relatively abrupt, usually presenting with a sudden onset of
- Chills
- High fever
- Headache
- Maculopapular rash appearing on the trunk and spreading to extremities, usually sparing the face, palms, and soles.
What 2 lab findings may provide diagnostic clues in cases of suspected Rocky Mountain Spotted Fever?
As the illness progresses, patients with RMSF often develop thrombocytopenia, which provides a diagnostic clue to the possibility of a rickettsial disease. In addition, hyponatremia is common in patients with CNS involvement.
Four days after camping, an 18-year-old college student reports to the campus health center with a headache. The covering physician noted a fever but found no other abnormalities on examination. A few days later he develops the rash shown in the photo. The rash started on his ankles and wrist, then spread towards the trunk and is nonpruritic. Which of the following is most likely?
A) Rocky Mountain spotted fever
B) Secondary syphilis
C) Chickenpox
D) Hand-foot-mouth disease
E) Mumps
Rocky Mountain spotted fever
Answer Explanation
Three notable palm-sole rash diseases are RMSF, coxsackievirus A (hand-foot-mouth disease), and secondary syphilis. HFM disease typically has painful sores in the mouth that blister and become ulcers, making it less likely in this scenario. In secondary syphilis, the distal extremity lesions tend to be more papular and discrete. However, the RMSF rash is never pathognomonic and differentiating between RMSF and secondary syphilis can be difficult. The history of recent exposure to outdoors points more towards RMSF, which is transmitted by tick bites, but again, this is also not pathognomonic.
What organisms can cause typhus?
R. typhi and R. prowazekii cause endemic (murine) and epidemic typhus, respectively.
Where is the highest incidence of Rocky Mountain Spotted Fever seen?
RMSF is endemic to the East Coast, with highest incidence in camping in North Carolina.
How does the Weil-Felix test work? What organisms can they help diagnose?
The Weil-Felix test, which detects cross-reacting antibodies against Proteus vulgaris antigens, lacks sensitivity and specificity, is no longer recommended. Rickettsia are Weil-Felix positive and C. burnetti is Weil-Felix negative.
Where is the incidence of ehrlichiosis highest in the United States?
Ehrlichiosis is found mainly in the mid-Atlantic, southeastern, and south central states.
What are 3 notable Rickettsia spp.?
Notable Rickettsia spp. include:
- Rickettsia rickettsii
- Rickettsia typhi
- Rickettsia prowazekii
What is added in addition to normal rickettsial treatment regimen in Q fever-related endocarditis?
Treatment for Q fever-related endocarditis includes doxycycline and hydroxychloroquine.
Below is a description of which Rickettsia bacteria?
- Cosmopolitan distribution.
- Transmitted by mites.
- Biphasic clinical presentation
Below is a descripsion of disease caused by what bug?
1st phase:
- In a wk - a papule where the mite bites.
- Progresses to ulceration and eschar.
- High fever distinguishes it from anthrax.
- Systemic spread during skin manifestation
2nd phase
- Abrupt onset – high fever, severe headache.
- Generalized maculopapular rash in 2-3d.
- Pox like progression – vesicles form and crust over.
- In spite of rash, mild disease – recovery in 2-3 weeks
A patient presents with the skin lesions shown below. Lab results show a gram negative bacteria with no presence of any gram-positive, encapsulated bacilli. What is the most likely bug?
Below is a description of what bug?
- Causes louse borne typhus.
- Humans are principal reservoirs.
- Crowded unsanitary living conditions (easy lice spread).
- More common in Central & South America, less in the US
Below is a description of disease caused by what bug?
- In 2-30d - high fever, severe headache and myalgia.
- Petechial maculopapular rash in 20-80% patients.
- Recovery in 2 wk but may remain dormant for years.
- Diagnosis: By MIF test.
Below is a description of what bug?
- Causes endemic or murine typhus worldwide.
- Usually in warm humid environment, rare in the US.
- Rodents are principal reservoir.
- Rat fleas are the vector worldwide, cat fleas in the US.
Below is a description of what bug?
- 7-14d incubation period, abrupt onset.
- Fever, severe headache, chills, myalgia and nausea.
- Patients present with rash - limited to chest & abdomen.
- Mild disease, lasts for ~3 weeks even without treatment
Below is a description of what bug?
- Etiologic agent for scrub typhus.
- Transmitted by mites (chiggers, red mites).
- In Eastern Asia, Australia, Japan & Western Pacific Islands
Below is a description of disease caused by what bug?
- Sudden onset after a 6-18d incubation period.
- Severe headache, fever and myalgias.
- A macular to papular rash on the trunk (<50% patients).
- Rash spreads centrifugally to the extremities.
- Even untreated patients recover in 2-3 weeks
Below is a description of what bugs?
- Transmitted by ticks.
- >2600 US cases of ehrlichiosis/anaplasmosis in 2010.
- Parasitize granulocytes, monocytes, RBCs and platelets
- Lack peptidoglycan, LPS & many glycolytic genes.
- Remain in phagosomes, don’t fuse with the lysosomes.
- 2 forms: small elementary (EB) & large reticulate bodies (RB).
- In few d, replicating EB form morulae (membrane-bound mass).
- Infected cells rupture, release bacteria, infect new cells
Below is a description of what disease?
- Caused by E. chaffeensis.
- Infection of blood and tissue monocytes.
- ~1-3 wk after tick bite, a flulike illness.
- High fever, headache, malaise, and myalgias.
- A late-onset rash in 1/3rd patients (more in children).
Human monocytic ehrlichiosis
Below is a description of what disease?
- Caused by A. phagocytophilum.
- Primarily infects granulocytes.
- In ~10d a flulike illness (high fever, headache, myalgias).
- Skin rash in <10% of patients
Human granulocytic ehrlichiosis (anaplasmosis)
Below are diagnostic findings of what bugs?
- Poor Gram stain (lack peptidoglycan).
- Giemsa-stain to see intracellular organisms (morulae) in blood.
- PCR & serology – m. common to confirm the clinical diagnosis
Below is a description of what bug?
- An intracellular pathogen.
- 2 forms: Small (SCV) and large cell variant (LCV).
- SCV – spore like and very resistant.
- Survive on wool (10 d), meat (1 mo), dust (3 mo), milk (3y).
Below is the epidemiology of what bug?
- Main reservoirs - farm animals.
- Increase In high numbers in placenta of infected livestock.
- Placentas, feces and urine can contaminate soil.
- Human infections - inhalation of airborne particles.
- Less commonly from unpasteurized dairy products
Below is a description of diseases cause by what bug?
- Cause of Q (query) fever worldwide.
- Small infectious dose & mostly asymptomatic.
- >50% with IgG lack a history of disease.
- Clinical presentation - nonspecific flulike.
- Chronic Q fever in mo-yr in I/C patients.
- S/A endocarditis in people with valvular heart defect
What is the life cycle of Chlamydophila spp. in human tissue?
Chlamydophila spp. have the same intracellular life cycle as Chlamydia trachomatis. Chlamydophila spp. enter cells of the upper respiratory epithelium and is phagocytosed by macrophages, and forms reticulate bodies (RB) that divide by binary fission and reorganize into elementary bodies (EB) within cytoplasmic inclusions. Once the cell is filled with cytoplasmic inclusions, the cells burst and release elementary bodies to infect nearby cells. EBs are infectious but metabolically inert outside of a human cell.
What is the causative organism of psittacosis (aka “parrot fever”)?
Chlamydophila psittaci causes atypical pneumonia known as psittacosis.
How is Chlamydophila pneumoniae transmitted?
C. pneumoniae is transmitted by aerosol droplets and has been associated with outbreaks in nursing homes.
What is the role of Gram stain in the diagnosis of Chlamydophila infection?
Microscopy is not useful for Chlamydophila spp. infection because, like Chlamydia trachomatis, Chlamydophila species are intracellular and cannot be visualized by Gram staining because it stains poorly.
How is Chlamydophila spp. pneumonia usually treated?
As most cases of C. pneumoniae and C. psittaci are empirically diagnosed without lab tests, the first course of treatment is usually azithromycin, as for all atypical pneumonias.
How are Chlamydophila pneumoniae and Chlamydophila psittaci diagnosed?
Specific diagnosis of C. pneumoniae and C. psittaci is made with a variety of techniques, including
- Immunofluorescence
- PCR
- Direct antigen testing
Culture is avoided since C. psittaci is highly infectious
A 41-year-old female complains of 2 weeks of fever and nonproductive cough. She works in a pet store. Chest X-ray reveals diffuse interstitial infiltrates in the left lobe. If the causative organism is an obligate intracellular microbe, which is most likely?
A) Bacillus anthracis
B) Streptococcus pneumoniae
C) Legionella pneumophila
D) Chlamydia psittaci
E) Rhinovirus
Chlamydophila psittaci
Answer Explanation
Fever, nonproductive cough, and diffuse interstitial infiltrates suggests an atypical pneumonia. C. psittaci, C. pneumoniae, and Legionella are candidates for atypical pneumonia. The history of exposure to birds (pet shop worker) leans the diagnosis more towards C. psittaci.
Legionella is not an obligate intracellular bacterium. Rhinovirus rarely causes lobar consolidation.
How is confirmed Chlamydophila spp. pneumonia best treated?
Treatment of choice for confirmed C. pneumoniae infections is doxycycline.
How does Chlamydophila pneumoniae infection present?
C. pneumoniae pneumonia is clinically indistinguishable from other infectious causes of pneumonia. Patients typically present with symptoms typical of pneumonia:
- Chest pain
- Cough
- Low fever
- Chills
- Myalgia
What disease(s) do Chlamydophila spp. cause?
C. pneumoniae causes atypical pneumonia, with a higher incidence in older adults. This is in contrast with Mycoplasma pneumoniae infection, which occurs most commonly in younger age groups.
How is Chlamydophila psittaci spread from birds to humans?
Transmission of C. psittaci is from birds via inhalation of organisms in dried feces. Activities such as cage cleaning may increase risk of infection.
How do Chlamydophila spp. survive in the human cell?
Chlamydophila spp. survives within a cytoplasmic inclusion in the cell by inhibiting lysosomal and endosomal fusion.
What are the two known species of Chlamydophila spp. associated with human disease?
Chlamydophila spp. are obligate intracellular bacteria that are weakly gram-negative. Chlamydophila spp. encompasses Chlamydophila pneumoniae and Chlamydophila psittaci.
Note: These species were previously identified as Chlamydia pneumoniae and Chlamydia psittaci, and may still appear under those names in some sources. They are closely related to Chlamydia trachomatis.
What findings on chest x-ray will indicate Chlamydophila pneumoniae rather than S. pneumoniae infection?
Chest X-ray usually shows one patchy area of subsegmental infiltration, as opposed to the lobar pneumonia more commonly seen in Streptococcus pneumoniae
How does Chlamydia trachomatis survive in the endosome once inside the body?
Chlamydia trachomatis survives within an endosome in the cell by inhibiting fusion of the endosome to the lysosome.
What changes in the cervix can be visualized in Chlamydia trachomatis infection?
Females may have cervical ectopy (columnar epithelium in outer layer of cervix) and easily induced endocervical bleeding.
What is a unique feature of Chlamydia trachomatis’ cell wall?
C. trachomatis cell wall lacks peptidoglycan due the absence of muramic acid, a component of bacterial cell walls. For this reason, penicillins are not very effective in treating chlamydial infection.
What disease process associated with Chlamydia trachomatis infection can progress to female infertility?
In Pelvic inflammatory disease, the infection spreads to the fallopian tubes and can lead to infertility and ectopic pregnancies.
A newborn with bacterial conjunctivitis is treated with IV cefotaxime. Isolates grown on chocolate agar containing lysed blood show that the gonococcus is sensitive to cefotaxime. 1 week later, the neonate continues to have purulent discharge from his eyes. What is the likely cause?
A) Herpes simplex virus
B) Chemical irritation from silver nitrate
C) Chlamydia trachomatis of types A-C
D) Staphylococcus aureus
E) Chlamydia trachomatis of types D-K
Chlamydia trachomatis of types D-K
Answer Explanation
Gonorrhea and Chlamydia genital infections occur together so often that CDC guidelines require treatment of both if gonorrhea is diagnosed. A neonate who is not prophylaxed against bacterial conjunctivitis is at risk for both types of gonococcal and chlamydial conjunctivitis.
In this case, the gonococcal conjunctivitis should be adequately treated with cefotaxime, especially in light of cultures showing that the strain is sensitive. This leaves chlamydial coinfection as the most likely cause of the continued infection.
Chlamydial serovars D-K cause genital infections. These infections can be passed to neonates who pass through infected birth canals. When the mother has chlamydia, uterine contractions during parturition not only provide the force to deliver the newborn into the world, they also may pry the tiny newborn’s eyelids open and thus expose the conjunctiva to the chlamydia-infested mucosa of their mother’s birth canal. Hello world! Ahhh! My eyes!
So in this situation, chlamydia serovars D-K can cause an acute conjunctivitis. This stands in contrast to trachoma, which is a chronic conjunctivitis (mainly occurring in Africa) caused by chlamydia serovars A-C.
How does epididymitis present in Chlamydia trachomatis infection?
In males with epididymitis, swelling of the epididymis may be accompanied by tenderness and palpable swelling.
What is the significance of serovars in Chlamydia trachomatis infection?
Serovars D-K and serovars A-C of Chlamydia trachomatis are distinguishable by different clinical manifestations. Classically, infections “above the waist” are caused by serovars A-C, while infections “below the waist” are caused by serovars D-K.
How do serovars A-C in Chlamydia trachomatis infection manifest?
Serovars A-C of Chlamydia trachomatis are transmitted by hand-eye contact, causing:
- Eye inflammation
- Corneal vascularization and scarring
- Blindness
Where in the body can Chlamydia trachomatis be found?
Chlamydia trachomatis is found in the genitourinary tract of infected, asymptomatic individuals. It can also be found in the eye, conjunctiva, and rectum.
What types of disease are caused by serovars D-K in Chlamydia trachomatis infection?
Serovars D-K of Chlamydia trachomatis infect columnar epithelium of the genitourinary tract, causing:
- Urethritis
- Cervicitis
- Pelvic inflammatory disease
- Neonatal disease (conjunctivitis and atypical pneumonia)
Note: Because neonatal infections are acquired during passage through the birth canal, they usually involve these serovars, even though they occur “above the waist.”
What is the triad of features in reactive arthritis (Reiter’s Syndrome) caused by Chlamydia trachomatis?
Rarely, patients develop reactive arthritis (a.k.a. Reiter’s Syndrome), a triad of arthritis, urethritis, and conjunctivitis. (“can’t see, can’t pee, can’t climb a tree.”) These symptoms may present in combination or individually.
How are neonatal Chlamydia trachomatis infection treated at birth?
Neonatal conjunctivitis and pneumonia are treated with oral erythromycin.
How is Chlamydia trachomatis diagnosed?
Diagnosis is made with nucleic acid amplification testing (NAAT) of vaginal swabs or first-catch urine in men. Rectal or conjunctival sampling can also be done if infection is localized here.
Chlamydia trachomatis causes what diseases?
Chlamydia trachomatis causes:
- Urethritis
- Pelvic inflammatory disease (PID)
- Chronic conjunctivitis
- Lymphogranuloma venereum (LGV)
- Neonatal pneumonia and conjunctivitis
- Fitz-Hugh-Curtis Syndrome
How is neonatal Chlamydia trachomatis infection acquired?
Neonatal pneumonia and/or neonatal conjunctivitis occur due to untreated maternal Chlamydia trachomatis infection, as the baby is exposed to C. trachomatis in the vaginal canal during delivery.
What organism is responsible for lymphogranuloma venereum?
Serovars L1-L3 of Chlamydia trachomatis cause lymphogranuloma venereum, a necrotizing granulomatous inflammation of the inguinal lymphatics and lymph nodes. Lymphogranuloma venereum can present as painless genital ulcers and painful lymphadenopathy (buboes). Eventual resolution can result in fibrosis that can lead to rectal strictures with perianal involvement.
How can Chlamydia trachomatis reinfection be prevented?
Sexual partners are often asymptomatic (85% of infected people have no symptoms) and can often cause reinfection in the successfully treated patient. Partners must also be treated to prevent reinfection.
How do male patients with Chlamydia trachomatis present?
Male patients usually present with watery or mucous discharge. In addition they may present with dysuria in urethritis, and may have unilateral testicular pain in epididymitis.
What first-line antibiotics are used to treat Chlamydia trachomatis?
Uncomplicated Chlamydia trachomatis infection can be easily treated with oral azithromycin and doxycycline.
How will Chlamydia trachomatis infection appear on urinalysis?
In cases of dysuria, urinalysis will demonstrate pyuria but no bacteria on urinalysis or gram stain.
Why is Chlamydia trachomatis difficult to visualize with gram staining?
Chlamydia trachomatis is an obligate intracellular bacterium that makes it difficult to visualize on microscopy and gram stain.
Chlamydia trachomatis is missing which of the following cellular components?
A) Ribonucleic acid
B) Lipopolysaccharide membrane
C) Plasma membrane
D) Muramic acid in the cell wall
E) Ribosomes
Muramic acid in the cell wall
Answer Explanation
Chlamydiae are technically gram-negative bacteria but Gram stain poorly because they lack muramic acid in their cell wall.
What will be visible on gram stain of vaginal/urethral swabs in Chlamydia trachomatis infection?
Vaginal or urethral swabs will show high levels of polymorphonuclear cells (PMNs) but, since Chlamydia trachomatis Gram stains poorly, no bacteria will appear on Gram stain.
How is Chlamydia trachomatis acquired?
Chlamydia trachomatis is sexually transmitted and often occurs in sexually active people and in neonates born vaginally to mothers with untreated C. trachomatis infection.
What is the life cycle of Chlamydia trachomatis in human tissue?
Chlamydia trachomatis enters epithelial cells as elementary bodies (EB) and is phagocytosed by macrophages, and forms reticulate bodies (RBs) that divide by binary fission and reorganize into EBs within cytoplasmic inclusions. Once the cell is filled with cytoplasmic inclusions, the cells burst and release elementary bodies to infect nearby cells. EBs are infectious but metabolically inert outside of a human cell.
What are common symptoms of genital Chlamydia trachomatis infection?
Genital Chlamydia trachomatis infection can present with lower abdominal pain, dysuria, and genital discharge.
What infectious diseases can cause the perihepatitis, or Fitz-Hugh-Curtis Syndrome?
Fitz-Hugh Curtis syndrome, or perihepatitis, consists of infection of the liver capsule and peritoneal surfaces of the anterior right upper quadrant from Neisseria and Chlamydia spp. Acute symptoms manifest as a patchy purulent and fibrinous exudate known as “violin string” adhesions.
How do female patients with Chlamydia trachomatis present?
Female patients typically present with
- Mucopurulent vaginal discharge in cervicitis
- Abdominopelvic pain in pelvic inflammatory disease
- Dysuria in dysuria-pyuria syndrome
How is Mycoplasma pneumoniae transmitted and what populations does this organism commonly affect?
M. pneumoniae is transmitted through inhalation of respiratory droplets and commonly affects young people, especially those in close quarters (prisons, military bases).
What are the treatments of Mycoplasma pneumoniae pneumonia?
Treatment can include either:
- Macrolide (erythromycin, azithromycin)
- Tetracycline (doxycycline)
- Fluoroquinolone
How does Mycoplasma pneumoniae cause the clinical symptoms once inhaled?
Inhaled organism adheres to respiratory epithelium and inhibits ciliary motion and destroys the mucosa, causing inflammation without invasion into the mucosa.
What do x-ray findings reveal in M. pneumoniae infection?
Chest x-ray findings may reveal vague ill-defined or patchy opacities.
How do patients typically present with Mycoplasma pneumoniae infections?
Patients with M. pneumoniae infection typically present with atypical pneumonia (walking pneumonia) and can include symptoms such as
- Fever
- Headache
- Myalgia
- Tracheobronchitis
- Non-productive cough
What is the mechanism of the cold serum agglutination test?
The cold serum agglutination test is an auto-immune response involving cold hemagglutinins of IgM antibodies (molecular mimicry) and blood group antigen I of human RBCs that result in the activation of complement.
Name a unique feature regarding the membrane of Mycoplasma pneumoniae.
The membrane of M. pneumoniae contains cholesterol.
What tests can be used to diagnose Mycoplasma pneumoniae infection?
Diagnosis can be made through serology or the cold serum agglutination test, which is non-specific. PCR, which is more specific, is becoming an accepted option.
A 17-year-old college freshman presents with a sore throat, dry cough, and associated dyspnea of 3 weeks’ duration. Chest X-ray demonstrates diffuse, bilateral infiltrates. Which test result is most suggestive of Mycoplasma pneumoniae pneumonia?
A) Leukocyte count of 8,000/mm3
B) The chest x-ray findings
C) Serum cold agglutinin titers of 1:128
D) Leukocyte count of 21,000/mm3
E) Erythrocyte sedimentation rate of 22 mm/hr
Serum cold agglutinin titers of 1:128
Answer Explanation
Patients with “walking pneumonia” can have upper respiratory and pneumonia Sx for up to a month. Most commonly affected are patients exposed to group-housing circumstances for the first time, like in college dorms or barracks. Patients with M. pneumoniae infections can have normal or elevated WBC counts, and normal or elevated ESR. The CXR findings are also non-specific and tend to “look worse than the patient.” Recall that serum cold agglutinins, while a non-specific test, are elevated in these patients. The titer cut-off for elevated levels is >1:64.
What group of bacteria grows in “mulberry” colonies and has a species with a “fried egg” appearance?
Mycoplasma
What growth medium is used for Mycoplasma?
Eaton agar
Below is a description of what bugs?
- Smallest-living bacteria.
- Tiny pleomorphic rods.
- Do not have a cell wall - resistant to cell wall inhibitors
- Cell membrane contains sterols.
- Membrane glycolipids & proteins are the major antigens
Mycoplasma and Ureaplasma
Below is the epidemiology of what bug?
- A strict human pathogen – worldwide.
- Mostly in school-age children & young adults.
- ~2m US pneumonias & 100K hospitalizations yearly.
- Easy spread among classmates, family members
Below are diseases of what bug?
- Most common presentation - tracheobronchitis.
- Low-fever, malaise, headache, a dry, nonproductive cough.
- Bronchial passages infiltrated with lymphocytes & plasma cells.
- May lead to pneumonia - atypical or walking pneumonia.
- Patchy bronchopneumonia seen on chest radiographs
Match the bug with the diseases:
Bugs:
- Mycoplasma genitalium
- Mycoplasma hominis
- Ureaplasma urealyticum
Diseases:
- Can cause nongonococcal urethritis (NGU) and PIDs
- NGU, pyelonephritis, abortion or premature birth
- Pyelonephritis, postpartum fever, septicemia in I/C patients
You would do the things below to diagnose what bugs?
- Culture throat & bronchial washings (no sputum).
- Use Eaton’s agar: media with serum (provides sterols).
- Also yeast extract (nucleic acids), glucose, and penicillin.
- Slow growth - small homogeneous granular colonies.
- “Mulberry shaped” (fried-egg for other mycoplasmas).
- As culturing takes weeks - most laboratories do not do it
Mycoplasma and Ureaplasma
What bug has a “fried egg” appearance?
Mycoplasma hominis:
- Large fried-egg appearance.
