Micro 7 Flashcards
Campylobacter jejuni
Gram ⊝ , comma or S shaped (with polar flagella) A , oxidase ⊕ , grows at 42°C (“Campylobacter likes the hot campfire”).
Major cause of bloody diarrhea, especially in children. Fecal-oral transmission through personto-person contact or via ingestion of undercooked contaminated poultry or meat, unpasteurized milk. Contact with infected animals (dogs, cats, pigs) is also a risk factor.
Common antecedent to Guillain-Barré syndrome and reactive arthritis.
Vibrio cholerae
🦋Gram ⊝ , flagellated, comma shaped A , oxidase ⊕ , grows in alkaline media. Endemic to developing countries.
🦋Produces profuse rice-water diarrhea via enterotoxin that permanently activates G, s cAMP. Sensitive to stomach acid (acid labile); requires large inoculum (high ID)50 unless host has gastric acidity.
🦋Transmitted via ingestion of contaminated water or uncooked food (eg, raw shellfish).
🦋Treat promptly with oral rehydration solution.
Helicobacter pylori
🔹Curved, flagellated (motile), gram ⊝ rod A that is triple ⊕ : catalase ⊕ , oxidase ⊕ , and urease ⊕ (can use urea breath test or fecal antigen test for diagnosis). Urease produces ammonia, creating an alkaline environment, which helps H pylori survive in acidic mucosa. 🔹🔶Colonizes mainly antrum of stomach; causes gastritis and peptic ulcers (especially duodenal). Risk factor for peptic ulcer disease, gastric adenocarcinoma, and MALT lymphoma.
🔹🔶Most common initial treatment is triple therapy: Amoxicillin (metronidazole if penicillin allergy) + Clarithromycin + Proton pump inhibitor; Antibiotics Cure Pylori.
Spirochetes
Spiral-shaped bacteria A with axial filaments. Includes Borrelia (big size), Leptospira, and Treponema. Only Borrelia can be visualized using aniline dyes (Wright or Giemsa stain) in light microscopy due to size. Treponema is visualized by dark-field microscopy or direct fluorescent antibody (DFA) microscopy.
BLT.
Borrelia is Big.
Lyme disease
🔸Caused by Borrelia burgdorferi, which is transmitted by the Ixodes deer tick A (also vector for Anaplasma spp. and protozoa Babesia). 🔸Natural reservoir is the mouse (and important to tick life cycle).
Common in northeastern United States.
🔸🔷🔸Stage 1—early localized: erythema migrans (typical “bulls-eye” configuration B is pathognomonic but not always present), flu-like symptoms.
🔸🔷🔸Stage 2—early disseminated: secondary lesions, carditis, AV block, facial nerve (Bell) palsy, migratory myalgias/transient arthritis.
🔸🔷🔸Stage 3—late disseminated: encephalopathy, chronic arthritis.
Lyme disease
A Key Lyme pie to the FACE:
🔺Facial nerve palsy (typically bilateral) 🔺Arthritis Cardiac block 🔺Erythema migrans
Treatment: doxycycline (1st line); amoxicillin and cefuroxime in pregnant women and children.
Leptospira interrogans
Spirochete with hook-shaped ends found in water contaminated with animal urine.
🔶Leptospirosis—flu-like symptoms, myalgias (classically of calves), jaundice, photophobia with
conjunctival suffusion (erythema without exudate). Prevalent among surfers and in tropics (eg, Hawaii).
🔶Weil disease (icterohemorrhagic leptospirosis)—severe form with jaundice and azotemia from liver and kidney dysfunction, fever, hemorrhage, and anemia.
Syphilis
Caused by spirochete Treponema pallidum.
Syphilis 1
. Localized disease presenting with painless chancre A . If available, use dark-field microscopy to visualize treponemes in fluid from chancre B . VDRL ⊕ in ~ 80%.
Syphilis 2
. Disseminated disease with constitutional symptoms, maculopapular rash C (including palms D and soles), condylomata lata E (smooth, painless, wart-like white lesions on genitals), lymphadenopathy, patchy hair loss; also confirmable with dark-field microscopy.
Serologic testing: VDRL/RPR (nonspecific), confirm diagnosis with specific test (eg, FTA-ABS). Secondary syphilis = Systemic. Latent syphilis ( ⊕ serology without symptoms) may follow.
Syphilis 3
. Gummas F (chronic granulomas), aortitis (vasa vasorum destruction), neurosyphilis (tabes dorsalis, “general paresis”), Argyll Robertson pupil (constricts with accommodation but is not reactive to light; also called “prostitute’s pupil” since it accommodates but does not react).
Signs: broad-based ataxia, ⊕ Romberg, Charcot joint, stroke without hypertension.
For neurosyphilis: test spinal fluid with VDRL, FTA-ABS, and PCR.
Syphilis congenital
. Presents with facial abnormalities such as rhagades (linear scars at angle of mouth, black arrow in G ), snuffles (nasal discharge, red arrow in G ), saddle nose, notched (Hutchinson) teeth H , mulberry molars, and short maxilla; saber shins; CN VIII deafness. To prevent, treat mother early in pregnancy, as placental transmission typically occurs after first trimester.
Jarisch-Herxheimer reaction
Flu-like syndrome (fever, chills, headache, myalgia) after antibiotics are started; due to killed bacteria (usually spirochetes) releasing toxins.
Gardnerella vaginalis
🔸A pleomorphic, gram-variable rod involved in bacterial vaginosis.
🔸🔷Presents as a gray vaginal discharge with a fishy smell; nonpainful (vs vaginitis).
🔸🔷Associated with sexual activity, but not sexually transmitted.
🔸Bacterial vaginosis is also characterized by overgrowth of certain anaerobic bacteria in vagina.
🔸🔷Clue cells (vaginal epithelial cells covered with Gardnerella) have stippled appearance along outer margin (arrow in A ).
🔴Treatment: metronidazole or clindamycin.
💥I don’t have a clue why I smell fish in the vagina garden!💥
Amine whiff test—mixing discharge with 10% KOH enhances fishy odor.
