As part of our continual process of service improvement, this May has seen the introduction of a fully automated enzyme immunoassay system, in microbiology, for the detection of Cryptosporidium and Giardia in faecal samples. This replaces the painstaking, traditional microscopic method, giving greater sensitivity and specificity of results as well as a shorter turnaround time. It has the added benefit of minimising staff handling of samples, so improving laboratory safety. There will be no change in the appearance of the laboratory reports to our clients, but the quality & consistency of results will be significantly improved.

 The bacteriology section in Microbiology involves the isolation and identification through microscopy, culture and sensitivity of clinically significant isolates.

Typical samples that are investigated include blood cultures, faeces,urine, swabs, fluids, tissues and sputa. Where relevant antimicrobial susceptibility testing is then carried out to aid patient management. In addition antibiotic assays are carried out to determine the amount of gentamycin, vancomycin or tobramycin present in patients serum to ensure safe therapeutic levels are maintained.

This section performs the rapid MRSA screening test and Clostridium difficile toxin testing and typing, which is of vital importance for the prevention of infection throughout the trust sites.

Operational Lead - Ann Myatt

Clinical Lead - Kathy Nye

Bacteriology Requesting

Blood Culture

Antibiotic Guidelines

Antibiotic Assays

Change to automated analyser for urine microbiological investigation

We are proposing from 9^th October 2006 to replace urine microscopy with a new automated technique using flow cytometry (UF-100 Biostat) to count the number of white and red blood cells, epithelial cells, casts and bacteria.  This technique is approximately four times more sensitive than microscopy and can confidently identify those samples that do not require culture.  We will continue to culture all urines in immunosuppressed and pregnant patients and from suprapubic aspirates.

You will notice the following changes:

1. An absolute count of the number of white cells and red blood cells will be reported.
2. Because of the increased sensitivity of the technique the counts will be higher than those currently given.  A new reference range will be provided to assist in determining whether the value is raised.
3. Samples with counts within the normal range by flow cytometry will be reported as negative on the day of receipt.  Those with elevated counts will be processed as before.
4. To help prevent sample deterioration urines MUST now be submitted in boric acid containers (red top universal), except for low volumes where plain universals can be used.

The proposed changes will provide benefits to all as the technique is more accurate than microscopy and there will be a more rapid turnaround of negative results which account for about 50% of the samples received

This is a draft protocol being piloted in the Trust & will be subject to review.

GUIDELINES FOR TAKING ROUTINE SPECIMENS

(* Does not include MRSA specimens) *Routine specimens (see specific protocols for Urology, Gynaecology, ITU, HDU etc)

URINE

• Do not take sample if urine is cloudy, smelly or offensive unless the patient has pyrexia. 
• Obtain specimen before commencement of antibiotics, as results are difficult to interpret once antibiotics have been commenced.
• Do not take routine specimens at catheter changes, do not send catheter tips.
• Use universal containers, and fill to at least half way.

FAECES

• Send specimen on patients with diarrhoea where an infective cause is suspected. Do not send a specimen if one has been sent in the last seven days as this will not be processed.

CLOSTRIDIUM DIFFICILE

• Do not send repeat specimens to see if negative as decision not to isolate is made on the cessation of diarrhoea not microbiology results.

SWABS

• Only take specimens from postoperative wounds if there is a purulent discharge i.e. the wound is discharging pus.

PRESSURE SORES

• Only take a swab if there is inflammation in the surrounding area and a purulent discharge. N.B An offensive smell alone is NOT AN indication to take a swab.

SPUTUM

• Sputum specimens should only be sent on patients with a diagnosis of pneumonia and only if they are productive and they have not yet commenced on antibiotics. If already on antibiotics, this MUST be recorded on the request form. Samples from COPD patients need to be specifically requested by medics. TB specimens should be requested by medics and 3 early morning specimens are required.

If sample is urgent please telephone the laboratory so that it is expected and can be processed as quickly as possible.

N.B Tips, Catheters and drains are not useful specimens as they are often contaminated or colonised and do not provide useful information.

HPA Sampling Procedure