JC M MICROBIOLOGY

JC M MICROBIOLOGY

TEACHING CLINIC 1
Dr Patrick Woo

Microbiology

Fri 25-10-02
INFECTIOUS DISEASE

Hx

P/E

Syndrome, Clinical Dx, Possible Causes

Investigations

± Empirical Tx / ± Infection control

Progress: New information, Sx, Ix results, Response to Tx

Revise Dx

New Ix: Review Tx regimen + Infection control protocol (back to step 6 or on to step ()

FINAL MICROBIOL Dx

Microbiol/ Lab 1. Clinical spec (BAL, bld, stool, sputum) 2. Test (culture bld, sputum Gram smear, MSU bact culture, biopsy MB/ fungus

Imaging: CXR, CT, MRI, US ® Localise/ extent of infection (eg. contrast CT ab ® ab abscess)

Empirical Tx: Tx B4 final Dx (acute cases)

Empirical infection control - eg. severe diarrhoea, open TB

PAPER CASE

Hx

M/45, PUO

Job: EO

Fever 1m, every day 39^oC

Transferred from another hospital

Injection no use (injection ABX for IE)

US: showed "heart inflammation"

No headache

Cough (intermittent), dry, no D w/ posture (occasionally cough awake at night)

No chest pain

Lost 10lb BW this year

No past Hx medial illness etc

Grade IV dyspnoea (at rest)

DDx = IE (atypical), TB

Note: ca lung does not/ rarely presents with fever (presents with cough)
Smoked 1 pack/d for 20 years
Alcohol (social)
Fam Hx unremarkable
No heart problems in youth
No dentist appointments
Fever each afternoon, chills beforehand
2m ago: travelled to Thailand for 1w (tour group)
No stomach pain/ diarrhoea
Married
No palpitations
No allergies

DDx = pericarditis, HIV/AIDS, leukaemia (chronic)

P/E

P 110 bpm, regular
RR 32/min (tachypnoea)
SaO2 90%
T 39 deg
No LN, ankle oedema, clubbing
RS: diffuse fine crackles bilaterally
CVS: heart sounds normal, ejection systolic murmur grade 2/6, no radiation

DDx: aortic stenosis (syphilitic aortitis?)

No organomegaly, rash, muscle wasting, external genitalia lesions, peripheral IE signs, neurological signs

DDx = chronic pneumonia syndrome

Ix

Chronic pneumonia syndrome ® CXR

TB ® smear ZN (early morning - physio-assisted, BAL if no good sputum), culture LJ, Mantoux

CBC

VDRL ® syphilis

ESR

Atypical TB (1) Legionella (2) Chlamydia (3) Mycoplasma pneumonia

HIV (1) Measure Ab presence - HIV Ab (2) Clotted blood - lab gets serum

Empirical Tx

MRSA - vancomycin

MSSA - enteroccus faecium, strep viridans

Pseudomonas aeruginosa - IVDU

But this case, do not need empirical Tx (already previous Tx with no response, sick 1m already \ not acute)

Ddx = subacute bacterial endocarditis

Can give supportive Tx (O2)
No Panadol - want to see fever pattern, response to Tx

Infection Control

Not needed for IE

DAY 2

CBC: WBC , ESR?

Blood: 2 bottles (aero, anaerobic), incubation (notified when growth), Gram smear of broth ® tell Dr what organism, then lab carries out ABX sensitivity testing

ECHO: valve N, chambers N, no vegetations

CXR: interstitial clouding (NOT lobar pneumonia)

HIV Ab: need to wait > 1w (faster if results have impact on Mx)

Blood: neutrophils N, ¯ lymphocytes (lymphopaenia)

Repeat P/E every day

Revise Dx

Aspergillosis: immunocompromised (CXR: parenchymal infiltrate - white-out)
Cryptococcus neoformans - sputum (Indian ink) - usu. imm-comp but not always
Use clotted blood - fungal culture - cryptococcal Ag testing

DAY 3

No D in S/Sx

Cryptoccocal Ag -ve (Indian ink -ve)

ESR (N < 10) = 30 (non-specific)

Ix: sputum - methylene silver (pneumocyti carinii)

Mycoplasma, Chlamydia IgM

Legionella (urine - Ag testing)

DAY 4

Result of Mantoux test: 0 mm
Silver stain -ve

DDx: chronic pneumonia syndrome (atypical organism) - eg. Legionella (empirical macrolides - eg. Arithro/ Clarithro/ Azithromycin)

Previous ECHO shows nodules on valve

Dx = PNEUMOCYSTIS CARINII PNEUMONIA (PCP) in HIV+ve Pt

CXR = ground-glass appearance

dyspnoea/ hypoxia

PCP: BAL is specimen of choice (sputum no good, except induce-sputum in HIV+ve Pt, b/c PC load cf. non-HIV Pt)

Suspect PCP ® urgent BAL, empirical Tx ( dose cotrimoxazole + steroid)

Steroid: immunomodulation (if only ABX, all PC die ® host response ® dyspnoea ® symptoms/ mortality rate/ ¯ SaO2

Note: this Pt's murmur is physiological (flow)

In this cause, should ask for rushed HIV Ab test

¯ CMV pneumonitis in HIV+ve (but retinitis, cholitis)

HIV CD4+ < 0.3/0.4

PNEUMOCYSTIS CARINII

Has not been grown in artificial culture

In imm-competent ® infection asymptomatic

Imm-compromised ® AIDS, cytotoxic drugs, malnutrition ® pneumonia

Large number of individuals are exposed at an early age - cysts remain in lungs until immunity impaired (reactivation)

Dx: examination of BAL by methanamine silver or IF

Lung biopsy useful when trophpozoites and cysts demonstrated by EM or silver impregnation stains

PCR detection of P carinii - demonstrates organism in nasopharyngeal aspirates

Tx: high dose cotrimoxazole, dapsone, pentamidine

Cotrimoxazole - prophylaxis in imm-compromised