The Osmosis Unit
26 Cotlands Park, Longniddry East Lothian Scotland EH32 0QX
44 (0)1875 852761
The Bug Scanner
One developing problem within the Health Service is the increase in Methicillin Resistant Staphylococcus aureus (MRSA) in hospitals and clinics. This is an organism that has developed resistance to most of the commonly used antibiotics. Any outbreak results in closure of the affected area for 5-7 days while the areas is decontaminated. The greatest part of this delay is the time taken for microbiological incubation and identification. The ability to speed up this process would greatly reduce the shut down time in these clinical areas.
William Stewart, the Surgeon General in the US declared in the early 1960’s that the time had come to close the book on infectious diseases (Economist 1995; May 20th : p15). Since the discovery of the first antibiotics by Erlich in Germany and the discovery of Penicillin by Flemming in Britain, there was a growing belief that we had cracked the treatment of bacteriological infection. People had underestimated the adaptability of bacteria.
Bacteria are amazing. The healthy skin of one individual is home to about one trillion bacteria. There are 100 trillion more in every individuals gut. Most people have ten times as many bacteria as they have cells. These organisms are generally not only harmless but co exist symbiotically with their host. They multiply roughly every 20 minutes and normally produce perfect copies of themselves. However, about every million divisions they produce a mutant. This rarely provides benefit for the species but occasionally an individual is produced with an advantage. This advantage may include antibiotic resistance. More worryingly bacteria have a method of sharing the genetic code that provides this resistance through a process known as plasmid transfer. Any bacteria can take little pieces of genetic information and share it with all other bacteria. Much of antibiotic resistance is believed to be spread in this way. Antibiotic development is therefore a race between the pharmaceutical companies and microbiological mutation. At present the microbes are winning. As we cannot kill this agent with antibiotics we have to remove it from contaminated areas by disinfection. Infected areas are washed from floor to ceiling with disinfectant. After leaving time for the disinfectant to work the area is swabbed and the swabs incubated to ensure that the infection has been removed. The aim of the process is not to cure the infected patient but to prevent the spread of the infection to other patients.
Microbiological testing at present involves sample collection, spreading this onto settle plates, transferring any areas of growth to secondary culture tubes, further incubation and colourimetric identification. The methods used have changed little since Robert Koch first grew anthrax bacteria in 1862. Koch, a country GP in Germany, worked out how to grow the organisms first on slices of cooked potatoe and then, after being shown how to make jelly by one of his wife’s friends, on agar jelly.
Agar jelly is still the standard growth medium used in microbiology.
Present microbiological techniques
The infected area is first swabbed with a cotton wool swab. This is then wipes over the surface of a sterile agar plate. This is then incubated at about 37 deg C for 2-3 days. Any visible areas of growth are then cut out of the agar and transferred to a broth. This is incubated for a further two days. The broth is then plated out into an OPI well disk which contains a range of different colour chemicals. The organism is identified depending on the resultant colour pattern produced. Various other methods of early bacterial identification are presently being tested. These are listed in table 1
Table 1 Methods of early identification of bacteria presently being tested
The equipment used in many of these tests (HPLC, mass spectroscopy, scanning
electron microscopy etc) costs several hundreds of thousands of pounds, requires
specially trained staff and requires expert interpretation. These tests are not
viable for the routine quality control lab. The other tests are focusing on DNA
analysis. At present these cost in the region of about £300 per test. Again this
is too expensive to consider for routine quality control. A simpler, cheaper
test is required.
|Identification of growth sooner than conventional “colony counters”|
|Enables identification of bacterial strain which should enable better targeting of antibiotic therapy where appropriate.|
|In the pharmaceutical industry it should enable faster analysis of antibiotic effectiveness during the antibiotic development process|
|It requires no significant changes to the methods of preparation, or the subsequent handling of samples for analysis|
|Uses existing techniques of preparation- little additional user training|
|Builds on existing principles- rapid, cost effective Route to Market|