There are three main situations where microbiology investigations are sent:
1. Where the patient has signs / symptoms of infection
The aim here is to try and identify the infecting organism.
2. Where the patient has been exposed to infection
In many cases the patient's immunity needs to be checked. e.g.
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immunocompromised patients in contact with various infectious diseases such as chicken pox, shingles, or measles.
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pregnant women in contact with rubella or chicken pox.
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staff following "needlestick" incidents.
Please contact medical staff in the lab when sending these tests, as urgent action is often needed e.g. administration of immunoglobulin. These samples are regarded as emergencies. The request form should be completed fully, as tests and advice will depend on the information given.
3. Where screening for a particular organism is required
e.g. MRSA,
If the patient has a fever within 3 weeks after departure from an area where viral haemorrhagic fever (eg Lassa fever) is endemic - mainly Central or West Africa: do not take any specimens or move the patient. Contact the Consultant Microbiologist (either in the laboratory or out-of-hours via switchboard).
When to take specimens
Before sending a specimen consider whether any result from the investigation is likely to alter the clinical management of the patient.
Whenever possible take specimens before antibiotics are started; this MUST NOT delay the antibiotic therapy in septic or immunocompromised patients. It is important to telephone the laboratory staff when emergency samples are sent.
Which specimens to take
Three main types of specimen are possible:
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Specimen from the infected site for microscopy culture and sensitivity
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Serum to look for antibodies following infection. Paired sera are usually
needed; one taken acutely and one at least 7 days after the onset of infection.
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Screening samples from designated sites according to protocol.
Patients with acute infection requiring admission to hospital nearly all need blood cultures and 10 ml of clotted blood sent with a virology form as an "acute" serum.
How to send specimens
All specimens must be accompanied by a correctly completed request form and must always be sent in a sealed plastic specimen bag. The request form must be placed in the separate side pocket of the plastic bag. (GP request forms are usually attached to the specimen bag)
Please always supply clinical details as we rely on these in the laboratory to carry out the appropriate tests.
All specimens except blood cultures should be stored in a fridge at 4oC if transport to the laboratory is delayed. Blood cultures must be stored at room temperature until transported to the laboratory.
It is important to telephone the laboratory when samples need to be examined urgently.
Hospital Air Tubes
Specimen may be sent to the laboratory by air tube where available. Respiratory and "Danger of Infection" specimens should sent in sealed double bags. Specimens that cannot be repeated should never be sent by air tube.
