Medical Microbiology

Question 0

Rx of clostridium perfringens

Answer 0

Remove necrotic tissue
Metronidazole

(?hyperbaric chambers, ?antitoxin)

Question 1

Gram stain clostridium perfringens

Answer 1

Gram positive bacilli

Question 2

Toxin causing gas gangrene

Answer 2

Lecithinase

Question 3

Diagnosis of clostridium perfringens

Answer 3

Aspirate bullae or remove necrotic tissue.
Gram stain fluid and culture.
Gram positive and grows only under anaerobic conditions.

Question 4

Describe gas gangrene

Answer 4

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

Question 5

Types of infections in C. perfringens

Answer 5

Simple contamination
Soft tissue infections
Anaerobic cellulitis
Gas gangrene (also uterine)
Bacteraemia

Question 6

What type of soft tissue infections occur with C. Perfringens

Answer 6

Intraabdominal (perforation)
Diabetic foot
Pelvic infection
Empyaema 
Pararectal abscesses 
Resp infection

Question 7

Anaerobic gram neg bacilli

Answer 7

Bacteroides
Fusobacterium
Prevotella
Porphyromonas

Question 8

Anaerobic infections above diaphragm most likely

Answer 8

Prevotella, porphyromonas and fusobacteria

Question 9

Anaerobic infection below the diaphragm most likely..

Answer 9

B. fragilis

Clostridium

Question 10

Infections presumed anaerobic until proven otherwise

Answer 10

Peritonsillar cellilitis/abscess
Dental/jaw infection
Brain abscess
Aspiration pneumonia 
Lung abscess/ bronchiectasis
Peritonitis/ peritoneal abscess
Perirectal abscess
Tuboovarian abscess
Necrotising cellulitis/ fasciitis

Question 11

What orgs produce black pigment when grown on blood agar

Answer 11

Prevotella

Porphyromonas

Question 12

Presence of anaerobic infection strongly suggested when…

Answer 12

Underlying predisposition 
Proximity to mucosal surface
Preceding treated aerobic infection
Necrosis, black, gangrene, gas
Septic embolus 
Putrid odour

Question 13

Rx of anaerobic infection

Answer 13

Die ride necrotic tissue
Remove pus
Metronidazole

Question 14

Gram stain of candida

Answer 14

Large gram positive oval (budding) yeasts

Question 15

Predisposing factors for candida infection

Answer 15

1. Disruption of flora - Abx
2. Decreased immunity - DM, chemo, HIV
3. Trauma - catheter

Question 16

Common site of infection for candida

Answer 16

Skin (axillae, obese, DM - red macerated)
Nails (washerwoman)
Mouth (AIDS, leukaemia - dysphagia)
Vulvovaginitis (pruritis)
Chronic mucocutaneous candidiasis (children deficient CMI)
Disseminated candidiasis

Question 17

Rx of candidiasis

Answer 17

Local - topical nystatin

Invasive - Amphotericin B , fluconazole

Question 18

Pathogenesis of zygomycosis

Answer 18

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.

Question 19

Lab diagnosis of zygomycosis

Answer 19

Broad non-septate hyphae in tissues. Difficult to grow.

Question 20

Rx of zygomycosis

Answer 20

Surgical removal

Amphotericin B

Question 21

Two main pathogens in zygomycosis

Answer 21

Mucor

Rhizopus

Question 22

Lab diagnosis of trichomanos vaginalis

Answer 22

Microscopic exam of wet prep (high vaginal/urethral swab) looking for motile trophozoites.

Possible rapid Ag and PCR

Question 23

Clinical manifestations of trichomonas vaginalis

Answer 23

Vaginitis - yellow, foul-smelling, frothy, itchy

Urethritis - burning on urination

Question 24

Rx of T. vaginalis

Answer 24

Metronidazole | TREAT PARTNER

Question 25

Morphology of T. vaginalis

Answer 25

Flagellate protozoan Four anterior flagella Short undulating membrane with fifth flagella at margin.

Question 26

Gram stain of N. gonorrhoeae

Answer 26

Gram negative diplococci

Question 27

Rx of N. gonorrhoeae

Answer 27

Cefixime | Ceftriaxone

Question 28

Lab diagnosis of N. gonorrhoeae

Answer 28

Pus collection. Microscopy, culture. Plus blood culture.

Question 29

Clinical manifestations of N. gonorrhoeae

Answer 29

``` Asymptomatic female Local infection (male - urethritis > epididymitis. female - cervicitis > PID) Ascending infection (prostatitis, salpingitis, epidydymitis, perihepatitis) ```

Question 30

Clinical manifestations of Chlamydia trachomatis

Answer 30

``` 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 ```

Question 31

Rx of C. Trachomatis

Answer 31

Tetracyclines (eg doxycycline )

Question 32

Detection of C. Trachomatis

Answer 32

Giemsa staining | Immunoflourescence - Ag detection

Question 33

Morphology of C. Trachomatis

Answer 33

Small round INTRACELLULAR organisms. | No gram stain.

Question 34

Microscopic appearance of gardnerella vaginalis

Answer 34

Clue cells

Question 35

Rx of gardnerella vaginalis

Answer 35

Metronidazole

Question 36

Pathogenesis of C. perfringens

Answer 36

Anaerobe infects ischemic or necrotic tissue. Produce toxins and enzymes that cause further necrosis allowing for spread of the organism.

Question 37

Microscopic appearance of treponema pallidum

Answer 37

Not visible on gram stain. | Spirochete on darkfield microscopy