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Page 1: Microbiologic sampling

Iman M. FawzyClinical Pathology MD.

PhDMansoura, Egypt

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SamplingSamplinginin

MicrobiologyMicrobiology

Iman M. FawzyClinical Pathology MD.

PhDMansoura, Egypt

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The best use of microbiologic lab.

involves sending only relevant

specimens.

For obtaining good quality sample for

microbiologic examination, certain

precautions should be considered.

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Rapid transporting of the specimens to the lab.

Collection of specimens before antibiotic therapy.

Sample collection as early as possible in the disease.

Containers used for collection should be sterile, tightly capped, and clearly labeled.

Cleaning the site of infection

General precautionsGeneral precautionsGeneral precautionsGeneral precautions

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Any specimen should be accompanied by request containing:

Patient's name, age, gender, in or outpatient, ward number, home area .

Type & source of specimen, date & time of collection.

Investigation(s) required.

Clinical note summarizing the patient's illness, suspected diagnosis, antimicrobial therapy.

Name of clinical officer .

Request formRequest formRequest formRequest form

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Proper Sampling in Clinical Microbiology Laboratory

Collection of good quality specimens Depends on:

1. The optimal time of specimen collection .2. The correct type of specimen 3. Well collected specimens with minimum

contamination from normal flora of the patient or the person collecting the specimen.

4. Adequate amounts of each specimens and appropriate no. of specimens

5. Clearly labeled safe specimens

Proper SamplingProper SamplingProper SamplingProper Sampling

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Proper SamplingProper SamplingProper SamplingProper Sampling

1 -Optimal time of collection of specimens: 1 -Optimal time of collection of specimens:

Specimens for the culture of bacteria must be collected before the start of antibiotics

Blood films for malarial parasites are usually best collected just as the patient's temperature starts to rise

When infective endocarditis is suspected, three blood culture sets can be collected within a 24 h period irrespective of the temperature of the patient .

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Proper SamplingProper SamplingProper SamplingProper Sampling

1 -Optimal time of collection of specimens: 1 -Optimal time of collection of specimens:

Serology is usually most satisfactory when a fourfold or greater rising antibody titre to a pathogen can be demonstrated in paired sera.

Specimens for electron microscopy or isolation of viruses are most likely to give positive results when collected during the most acute stages of the disease

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Proper SamplingProper SamplingProper SamplingProper Sampling

2 -Correct types of specimens 2 -Correct types of specimens

Patients with possible bacterial meningitis should have blood cultures as well as cerebrospinal fluid collected.

Cervical, urethral and preferably rectal swabs should be collected rather than high vaginal swabs from female patients with suspected gonorrhoea.

Pernasal swabs should always be collected from children who may have pertussis rather than a throat or ordinary nose swab.

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Proper SamplingProper SamplingProper SamplingProper Sampling

3- Well- collected specimens with minimal contamination from normal flora

3- Well- collected specimens with minimal contamination from normal flora

All staff should become aware of the importance of minimizing the contamination of specimens.

Poor-quality specimens include saliva instead of sputum or a salivary-mucoid sputum sample instead of a mucopurulent specimen from a patient with pneumonia .

Mid-stream specimens of urine to avoid excessive contamination.

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Proper SamplingProper SamplingProper SamplingProper Sampling

3- Well- collected specimens with minimal contamination from normal flora

3- Well- collected specimens with minimal contamination from normal flora

Throat swab collected should not touch the buccal mucosa or tongue .

A high vaginal swab should be collected using a vaginal speculum which should not be wet with antiseptic solution with care not to touch the lower region or perineum.

Blood or cerebrospinal fluid (CSF) cultures can be contaminated by the skin flora of the patient or from the doctor .

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4 -Adequate quantity of the specimens 4 -Adequate quantity of the specimens

The collection of adequate quantities of early morning sputum.

At least two samples of faeces on different days are desirable from patients with diarrhoea.

When carriage of Salmonella typhi is investigated in a food handler, 6 samples of faces should be cultured.

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Proper SamplingProper SamplingProper SamplingProper Sampling

4 -Adequate quantity of the specimens 4 -Adequate quantity of the specimens

Patients with diarrhea at least 2 specimens of faces is collected for culture of Salmonellae or Shigella.

Serological investigations usually require paired sera.

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Proper SamplingProper SamplingProper SamplingProper Sampling

5 -Clearly labeled and safe containers 5 -Clearly labeled and safe containers

Microbiological investigations should be placed in leak-proof containers.

Each container should be enclosed in a plastic bag.

Examples of microbiological hazards to staff handling leaking containers include TB, and viruses such as HBV and HIV.

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Urine SamplesUrine Samples

When gonorrhea is suspected

immediate culture (bed side) or

using transport medium

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Blood SamplesBlood Samples

•Serum can be used for culture on fluid medium.

•Blood for serological diagnosis is collected in screw capped tubes without anticoagulant.

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Body Fluids SamplesBody Fluids Samples

Sterilizing the site with alcohol 70% and iodine.

Rapid transporting to the lab especially for CSF.

Using wide mouth, sterile containers to which 0.3ml of 20% Na citrate is added to prevent clot formation.

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Sputum SamplesSputum Samples

An alternative method, the tongue is depressed and cough is induced by touching the larynx, material from the trachea expelled during the cough will adhere on the swab.

Samples for T.B. are 3 consecutive morning samples.

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SwabsSwabs

It is a sample device

consist of sterile pledget of absorbent material, usually cotton-wool or synthetic fiber, mounted on a thin wire or stick.

Swabs for Bacterial (red) and Viral (green) Cultures

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Stool SamplesStool Samples

Stool is collected in wide-mouth container.

Stool is collected in leak proof sterile container into which the excreta can be passed directly.

Alternatively, rectal swab may be taken.

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Stool SamplesStool Samples

For preserving Salmonella, place several drops of luiquid faces or faecal emulsion on a sheet of filter paper and allow it to dry and preserve it in a cellophane envelop for transporting to the lab. In the lab a saline suspension of material from the filter paper is plated on a selective media.

For Cholera. The faeces is sent in bile peptone medium to prevent the death of Vibrio cholera .

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Gynacologicol samplingGynacologicol sampling

Cervical swab is preferred rather than vaginal ones.

Dry, sterile speculum should be used or moistened with sterile warm water.

No bimanual examination performed.

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Gynacologicol samplingGynacologicol sampling

Cleanse the cx. with swab moistened with sterile saline.

Sterile swab is used for sample collection by rotating it in the cervix.

When gonorrhea is suspected immediate culture (bed side) or using transport medium .

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Sampling for Mycologic examSampling for Mycologic exam

Clean the site with alcohol 70%.

Sterile scalpel is used for scrapping.

Sterile scissor is used for trimming the nails.

Scales are transferred in clean dark paper.

For systemic mycosis, precautions are those for blood culture.

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Sampling for Clinical VirologySampling for Clinical Virology

Collection of specimen during most active stage of the disease.

Samples as urine , stool , CSF , sputum are transported directly to the lab while swabs from throat , nose vesicles , cervix are transported in VTM.

If delay is in due, keep specimens at 4 0C.

Biohazard label should be used for containers of HBV, HCV and HIV.

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