Collection, Handling and Processing of Clinical Specimens

in the acute phase of an illness specimen should be collected before or after antibiotic therapy?

before

Deep tissue specimen preferrer collecting what than swab and why?

aspirate or pus, organisms would be more exposed to atmospheric oxygen on a swab compared to inside a tissue.

 Ideally, specimens should be transported to the lab within ? minutes of collection?

30

how should containers be transported?

Containers should be leak-proof and should be transported in sealable and leak-proof plastic bags marked with a biohazard label.

what is used to preserve urine? why?

Boric acid. number of cfu/ml is critical in interpreting results for true infection or mere contamination.

what is used for stool samples to maintain the integrity of cysts and trophozoites?

Polyvinyl alcohol (PVA) and buffered formalin

what do Holding media or preservatives do?

maintain the organisms so that no organism overgrows another or dies out.

what is added to some holding media to absorb the inhibitory fatty acids that could kill fastidious organisms?

 Charcoal

Refrigerator temperature (4°C) for storing what specimen? (6)

urine, stool, viral specimens, sputum, swabs and catheters

what should never be placed in the refrigerator? why?

Specimens for anaerobic culture. Anaerobes are sensitive to cold temperature.

Medically significant anaerobes grow at human body temperature.

CSF samples should always be stored at what temp? why?

37°C. Organisms causing central nervous system infections are fastidious and rapidly die at room or cooler temperatures.

tissue biopsies can be stored at what temp?

-70°C

Serum may be frozen for up to how long in what temp?

a week at -20°C

reject whe specimen transport time exceeds how long postcollection?

2 hours

in Gross Examination of Specimen, Stools should be examined for what?

barium

Microscopy is usually not performed for what specimen? Why?

throat, nasopharyngeal and stool specimens. All these anatomical sites have abundance of resident flora and it would be almost impossible to distinguish between pathogens and normal flora based on their microscopic morphology

fungi incubated in what temp?

 28°C

most bacteria and viruses and AFB incubate in what temp?

35-37°C

how to incubate Aerobes?

 grow in ambient air which contains 21% O2 and 0.03% CO2

how to grow Anaerobes?

grow in chambers or jars with 5-10% H2, 5-10% CO2, 80-90% N2 and 0% O2

what types of organisms are Campylobacter jejuni and

Helicobacter pylori?

Microaerophiles

how to grow Microaerophiles?

 grow under reduced O2 (5-10%) and increased CO2 (8-10%)

what types of organisms are H. influenzae and N. gonorrhoeae?

Capnophiles

how to grow Capnophiles?

increased tension of CO2 (5-10%) and approximately 15% O2

should CLSs discriminate reporting of normal flora?

yes, Indiscriminate reporting of normal flora can contribute to misuse of antibiotics and hence, emergence of resistant organisms

what do  Nutritive media  do? examples?

support the growth of wide variety of microbes. nonselective, primary

plating media. blood and chocolate agars

what do Differential media do? example?

differentiates between organisms on the basis of growth characteristics. e.g., blood agar differentiates hemolytic pattern

what do Selective media do? example?

support the growth of one group over another by adding antimicrobials, dyes or alcohol. e.g., MacConkey agar and Columbia Nalidixic Acid agar (CNA)

how to select media?

Selection of media is based on type or origin of the specimen