The Institute of Biomedical Science

All about microbiology: the work and roles of microbiologists

What is a medical microbiologist?

The work of medical microbiologists often breaks into the news with stories such as hospital 'superbugs', the latest meningitis outbreak or fears of anthrax attacks. More scientifically, a microbiologist is concerned with the detection, isolation and identification of micro-organisms such as bacteria, fungi and parasites that cause disease. Any part of the human body, whether tissue or fluid, can be examined.

Urinary Tract Infections are by far the most common infection in the UK, and as a consequence, urine samples are the most common sample examined. Samples, which often arrive as fluid or swabs from various orifices, are inoculated onto culture media which allows the micro-organisms to grow after overnight incubation, usually at body temperature (37°C). The following morning the culture plates are examined and interpreted to determine whether any of the organisms growing is a pathogen or not. Remember the body is covered with a normal flora, or 'good bacteria', that help prevent infection. Tests are carried out to determine both the full identity of any suspect pathogens, and the sensitivity of the pathogens to a range of currently used antibiotics. The work can be painstaking and meticulous but it has to be - patients' lives depend on it. This information, along with reports from other biomedical scientists such as haematologists, is given to the doctor who will make a decision on the correct management and treatment of the patient.

Typical roles

Medical microbiologists diagnose diseases such as tuberculosis, meningitis, salmonella, thrush (candida) and MRSA infection, to name a few. They investigate food poisoning outbreaks and provide a quality control service to the food and drinks industry. Certain microbiology labs also form part of the frontline defence against bio-terrorism. They also undertake research and can be found in areas as diverse as medicine, industry, environment and education but the most common area is healthcare. Advanced roles can be found in management, medical research, consultancy, media and education.

The work of all biomedical scientists is constantly evolving as relatively new infections, such as campylobacter, helicobacter and legionella are recognised, while research and medical development always push diagnosis techniques forward. Often ‘older’ diseases such as tuberculosis may occur, and less commonly cholera and diphtheria are still being diagnosed in the UK, although often foreign travel is involved.

There are two main methods of analysis - the traditional method involves culturing the patient specimen onto plates or into broths, in order to isolate and identify bacteria. The more modern molecular methods involves looking for specific DNA, within the specimen or bacteria and is at the cutting edge of technology. Tuberculosis, for example, once took 12 weeks to diagnose - now using molecular methods it takes two days.

A day in the life of a...medical microbiologist

Name: Matthew Hughes
Works at: Medical microbiology department, St Peters and Ashford Hospital
Career: graduated with a BSc degree in biomedical science from the University of Bradford and went on to complete a long distance learning MSc course in biomedical science provided by the University of Ulster (both courses accredited by the IBMS). Now working towards taking the IBMS Higher Specialist Diploma, which is a professional qualification.

8.30 am It's a hot August Bank Holiday Monday and I’m heading for the microbiology lab at St. Peter’s Hospital. No traffic jams this morning and a parking space right outside the lab door for once! Just like other professionals in health we provide a 24-hour, 365-day service but today I only have to work until 13.30 so its not too bad.

First stop is the 'out of hours incubator' to collect the blood cultures. These samples are taken from very ill patients with septicaemia (blood poisoning). I take them to pathology reception to check and number the bottles before heading for the microbiology lab.

There are positive cultures requiring attention in the computer controlled Bactec blood culture machine. I put in the newly collected bottles and remove the positive bottles. I prepare slides of their contents and put them on a hot plate to dry. I check for any special instructions left by the weekend working team.

First to the 'wound bench' where I gather the Petri-dish cultures which have been incubated and examine or 'read' them, recording all my findings on one of the many computer terminals around the lab. The phone rings. There is concern about a patient. A urine sample was sent down yesterday and results are needed urgently. I promise to look at the cultures and phone back. This lab processes 250 urine samples every day. I trace the lab culture number for this patient’s sample, find the culture and telephone back with the results so they can provide treatment for the patient as soon as possible. Although we rarely deal with patients at first hand that doesn't mean we forget the human story behind the sample or that effective and quick treatment of a patient depend on our work. Sometimes you see the results of a test and your heart goes out when you know what it means for the patient.

10.00 am The slides I made earlier are now dry so I stain and examine them under the microscope at 500 and 1000 X magnification so that the bacteria present are clearly visible. I telephone these results to the consultant microbiologist (medical staff) on duty who will liase with and give advice to the ward staff. I set up Petri-dish cultures and antibiotic sensitivity tests from these important blood culture samples. Part of the reason why I like this job is because it’s so hand-on - I really enjoy investigating specimens. That and of course the fact that I can make a difference.

11.00 am The phone rings - a seriously ill patient is being treated with Vancomycin, a potentially toxic antibiotic. The ward want me to measure the level of drug in the patient’s blood to make sure it’s not too high. The test is done by machine but a good deal of preparation has to be done. There are chemicals to prepare, the sample to collect then centrifuge and the appropriate blood component to separate first. The test is soon up and running.

I move to the Stool bench and a note from the Sunday team asks me to complete the identification of probable food poisoning bacteria from a patient. I add reagents to an identification system of 20 biochemical reactions. The results produce a numerical profile that I enter into a computer to obtain identification. The organism identifies as Salmonella species and so we have found a reason why the patient is suffering with diarrhoea. I phone the ward then read off the Vancomycin level results that are now ready to be phoned to the appropriate wards.

12.30 pm Coffee would be nice but I need to sort through the new samples which arrive for processing. Only urgent samples are cultured on Bank Holidays. I do culture and microscopy on a fluid extracted by needle from an infected knee, a sample of pus taken in theatre from a burst appendix and a sputum from a patient with pneumonia.

1.30 pm I take a while to clear up and remember the joke that you can always tell a microbiologist by how thoroughly they wash their hands! As I head for home the sun is still shining but I can’t completely relax as I am 'On call' until 8.30 tomorrow morning and almost certainly will have to return to the lab. I arrive home and the coffee goes down a treat. I take the opportunity to complete some reading for my Continuing Professional Development portfolio. This will also help me with my professional diploma, which I am working towards, as I want to progress to more advanced and specialised roles. No matter how experienced you become you always need to keep up with scientific and professional trends, but that’s what makes a career in medical microbiology so interesting and rewarding.

Our thanks to Alex Gullon at the pathology department at Ashford's and St Peter's Hospitals and Steve Davies of the IBMS's Medical Microbiology Advisory Panel.