First Aid Microbiology 2 Flashcards
”. . . organism is isolated and cultured, forming pink colonies on McConkey augar. . .”
- This indicates that the organisms are lactose fermenters
- Narrows it down to:
- E. coli
- Klebsiella pneumoniae
- Serratia marcescens
- Enterobacter species
- These organisms are all common causes of pneumonia and UTI, especially nosocomial pneumonia and UTI
- Note on Serratia: It ferments lactose slowly, so it may appear negative on culture at first. However, it also produces a slight pink pigment – in fact you have probably seen this pigment if you ever had a moldy bathtub, because Serratia likes to grow on wet tile surfaces.
The three A’s of Klebsiella
- Alcoholics
- Abscesses
- Aspiration
“Currant jelly sputum”
Klebsiella pneumoniae buzz word
What is going on in this image?
Oral hairy leukoplakia
Often mistaken for thrush, but it only occurs on the lateral undersides of the tongue and cannot be scraped off.
This is almost exclusively seen in individuals co-infected with HIV and EBV
Why must patients with EBV avoid contact sports?
Due to risk of traumatic splenic rupture
What is going on in this infant?
Blueberry muffin rash
Characteristic of congenital CMV or rubella infection (two ToRCHES-group infections)
CMV Torch infection
- >80% asymptomatic, but when it is not:
- Blueberry muffin rash
- Sensorineural deafness
- Hepatosplenomegaly
- Jaundice
- Ventricular enlargement
- Periventricular calcifications
- Developmental delay and/or seizures
- In asymptomatic individuals, CMV activation may later cause unilateral or bilateral sensorineural hearing loss. It is the #1 cause for childhood sensorineural hearing loss.
When are HIV patients at risk for CMV?
When CD4 count is below 50
Most common presentation is necrosing retinitis, with “pizza pie” retina.
Esophagitis in a single, deep, linear ulceration is also common. Colitis with ulceration may also occur.
Treatments of choice for CMV
1st line: Gancyclovir
2nd line: Foscarnet (use when UL97 resistance mutation to gancyclovir is present)
“Mononucleosis” may be caused by. . .
EBV, CMV, or initial HIV
Tell them apart w/ monospot, which will be negative for CMV and HIV. If it returns negative, further CMV and HIV workup is required. Since monospot is sometimes falsely negative, a different EBV test may also be warranted.
Drawing the line between HIV and AIDS
CD4 < 200
OR
Low CD4 in the context of an AIDS-defining opportunistic infection
OR
Low CD4 in the context of an HIV-driven diffuse large B cell lymphoma
Testing for HIV in a neonate
HIV is a TORCHES-group infection. So, it can be passed from mother to child.
This presents a diagnostic problem. The way we usually diagnose HIV is with a screening ELISA, followed by a confirmatory Western blot.
But, of course, if mom is infected, the baby will for sure have HIV anti-IgG that it acquired from mom even if the baby is not infected!
So, in neonates, we instead look for HIV genetic material directly.
Antiretrovirals for pregnant women infected with HIV
Ziduvodine is the drug of choice
Antiretroviral summary
Donovanosis
Aka granuloma inguinale
Sexually transmissible genital ulcer disease caused by Klebsiella granulomatis.
Characterized as painless ulcers with raised borders and “kissing” apperance. May be complicated by subsequent coinfection.
Diagnosed by presence of “Donovan bodies” (bacteria within macrophage cytoplasm) on biopsy
Treat w/ azithromycin
The four “C”s of Measles
Remember that measles = rubeolla!
Koplik spots are pathognomonic for measles. Here they are shown on the tongue, but they can also appear on the cheeks. They are often white, but may be bluish, and are surrounded by red erythematous mucosa.
Four C’s are followed by a maculopapular rash that starts from the head and moves down.
Complications of measles
- Bacterial superinfection (usually pneumonia)
-
Sclerosing pan-encephalitis
- May present DECADES after the infection, or without known history of infection at all, but CSF will contain anti-rubeolla antibodies. There is no treatment.
What is going on in this pathology section?
This is a Warthin-Finkeldey cell, pathognomonic for measles/rubeolla.
It is a syncytial cell created by multiple cells expressing rubeolla’s fusion proteins.
Phases of pertussis
Patient presents with focal deficits, high fever, and neck stiffness following a weekend trip to Yellow Stone, where they went to swim in the park’s fresh water rivers. Lumbar puncture reveals trophozoites in the CSF.
What was the original source of the causative organism?
Animal pee
This is Naegleria fowleri, the cause of acute amoebic meningoencephalitis.
It recently caused an epidemic in Texas where the local water supply was contaminated. Trophozoites enter through the nasal pathway and cribriform plate.
Treat w/ amphotericin – remember, amoebae are protists and closely related to fungi!
Patient presents with flu-like symptoms following return from a vacation to Hawaii. They are perscribed oseltamavir for symptoms.
Two days later, they return with continued occular symptoms, the following occular finding, and in severe distress. They are found to have significantly elevated creatinine and bilirubin.
What is the likely diagnosis?
Leptospirosis precipitating Weil’s disease (hematogenous leptospirosis affecting multiple organ systems)
It was most likely acquired from fresh water swimming in Hawaii in a waterbed that had been contaminated by animal urine
Rose Gardener’s Disease
Sporothix schenckii: When a rose shanks you
A local pustule or ulcer forms at the site of trauma. Nodules then develop along the path of draining lymphatics, which if biopsied will show granulomas (similar to M. marinum). They will also contain budding yeast (unlike M. marinum).
The treatment of choice is oral itraconazole. An old-timey treatment was potassium iodide, which contributed to the naming of the disease since it was also a pesticide used in rose gardens (but not used for either any more).
Neonatal gonorrheal conjunctavitis vs neonatal chlamydial conjunctavitis
The big difference is in time of onset. When comparing gonorrhea and chlamydia, they are always similar, but gonorrhea is always faster and worse. It grows faster, it spreads faster, it causes a live arthritis as opposed to a reactive arthritis, its discharge is thicker, etc.
Note: This table has a mistake. Whenever you see gonorrhea or chlamydia, be it in the genitals or in the eyes, you always assume that the other is present as a coinfection. So, you treat both forms of conjunctavitis the same way: erythromycin AND ceftriaxone.
Based on the following x-ray, what is the likely causative organism? How should the patient be treated?
Proteus mirabilis
This is a staghorn calculus in the renal pelvix, most commonly caused by Proteus infection.
These calculi are made of ammona, magnesium, and phosphate.
The optimal treatment is with sulfonamides.
