Medical Microbiology Flashcards
Rx of clostridium perfringens
Remove necrotic tissue
Metronidazole
(?hyperbaric chambers, ?antitoxin)
Gram stain clostridium perfringens
Gram positive bacilli
Toxin causing gas gangrene
Lecithinase
Diagnosis of clostridium perfringens
Aspirate bullae or remove necrotic tissue.
Gram stain fluid and culture.
Gram positive and grows only under anaerobic conditions.
Describe gas gangrene
Infection involves muscle tissue. Overlying skin = oedematous/ tense and may be large haemorrhagic bullae. Pain but no high fever.
Alert despite hypotension/RF.
Gas in tissues = crepitus
Types of infections in C. perfringens
Simple contamination Soft tissue infections Anaerobic cellulitis Gas gangrene (also uterine) Bacteraemia
What type of soft tissue infections occur with C. Perfringens
Intraabdominal (perforation) Diabetic foot Pelvic infection Empyaema Pararectal abscesses Resp infection
Anaerobic gram neg bacilli
Bacteroides
Fusobacterium
Prevotella
Porphyromonas
Anaerobic infections above diaphragm most likely
Prevotella, porphyromonas and fusobacteria
Anaerobic infection below the diaphragm most likely..
B. fragilis
Clostridium
Infections presumed anaerobic until proven otherwise
Peritonsillar cellilitis/abscess Dental/jaw infection Brain abscess Aspiration pneumonia Lung abscess/ bronchiectasis Peritonitis/ peritoneal abscess Perirectal abscess Tuboovarian abscess Necrotising cellulitis/ fasciitis
What orgs produce black pigment when grown on blood agar
Prevotella
Porphyromonas
Presence of anaerobic infection strongly suggested when…
Underlying predisposition Proximity to mucosal surface Preceding treated aerobic infection Necrosis, black, gangrene, gas Septic embolus Putrid odour
Rx of anaerobic infection
Die ride necrotic tissue
Remove pus
Metronidazole
Gram stain of candida
Large gram positive oval (budding) yeasts
Predisposing factors for candida infection
- Disruption of flora - Abx
- Decreased immunity - DM, chemo, HIV
- Trauma - catheter
Common site of infection for candida
Skin (axillae, obese, DM - red macerated)
Nails (washerwoman)
Mouth (AIDS, leukaemia - dysphagia)
Vulvovaginitis (pruritis)
Chronic mucocutaneous candidiasis (children deficient CMI)
Disseminated candidiasis
Rx of candidiasis
Local - topical nystatin
Invasive - Amphotericin B , fluconazole
Pathogenesis of zygomycosis
Spore inhaled.
If immunocomprimsed (DM,HIV,leukaemia) implant in nasal sinuses.
Hyphae invasion through/across blood vessels
Thrombosis.
Severe tissue destruction of face, eye, brain.
Lab diagnosis of zygomycosis
Broad non-septate hyphae in tissues. Difficult to grow.
Rx of zygomycosis
Surgical removal
Amphotericin B
Two main pathogens in zygomycosis
Mucor
Rhizopus
Lab diagnosis of trichomanos vaginalis
Microscopic exam of wet prep (high vaginal/urethral swab) looking for motile trophozoites.
Possible rapid Ag and PCR
Clinical manifestations of trichomonas vaginalis
Vaginitis - yellow, foul-smelling, frothy, itchy
Urethritis - burning on urination
Rx of T. vaginalis
Metronidazole
TREAT PARTNER
Morphology of T. vaginalis
Flagellate protozoan
Four anterior flagella
Short undulating membrane with fifth flagella at margin.
Gram stain of N. gonorrhoeae
Gram negative diplococci
Rx of N. gonorrhoeae
Cefixime
Ceftriaxone
Lab diagnosis of N. gonorrhoeae
Pus collection.
Microscopy, culture.
Plus blood culture.
Clinical manifestations of N. gonorrhoeae
Asymptomatic female Local infection (male - urethritis > epididymitis. female - cervicitis > PID) Ascending infection (prostatitis, salpingitis, epidydymitis, perihepatitis)
Clinical manifestations of Chlamydia trachomatis
Cervicitis / urethritis (serovars D-K) thin watery discharge Inclusion conjunctivitis (serovars D-K) Pneumonia (serovars D-K) <6years Lymphogranuloma venereum (serovars L1-3) small ulcerative papule. Trachoma (serovars A-C) chronic conjunctivitis plus scaring that leads to blindness
Rx of C. Trachomatis
Tetracyclines (eg doxycycline )
Detection of C. Trachomatis
Giemsa staining
Immunoflourescence - Ag detection
Morphology of C. Trachomatis
Small round INTRACELLULAR organisms.
No gram stain.
Microscopic appearance of gardnerella vaginalis
Clue cells
Rx of gardnerella vaginalis
Metronidazole
Pathogenesis of C. perfringens
Anaerobe infects ischemic or necrotic tissue. Produce toxins and enzymes that cause further necrosis allowing for spread of the organism.
Microscopic appearance of treponema pallidum
Not visible on gram stain.
Spirochete on darkfield microscopy
