Antibiotics and multiresistant bacteria

Antibiotics and multiresistant bacteria

My physician informed me that my bacteria are multiresistant to antibiotics. I have heard about a laboratory in Ottawa where antibiotic combinations capable of destroying recalcitrant bacteria are being developed through a specific technique. I would like some information on the lab procedures used in the analyses, on the dependability of the “winning” combinations and on costs associated with this type of operation.

A technique has indeed been developed for performing laboratory studies on antibiotic combinations that can destroy multiresistant bacteria in cystic fibrosis patients. The process involves testing 298 different double and triple antibiotic combinations for Burkholderia cepacia and 361 different double and triple antibiotic combinations for Pseudomonas aeruginosa.

The tests are carried out using plastic plates, each with 96 tiny openings, or wells, which are filled with a special fluid, or culture broth. Samples from the patient are also added. One, two or three different antibiotics are added individually to each well. We then examine the plates at 24 and 48 hours to determine if the well is turbid (cloudy) or clear. A turbid well indicates that the organism has managed to grow in the fluid despite the presence of antibiotics. A clear well indicates destruction of the organism. We perform additional tests on the fluid to make sure the organism has truly been destroyed. We then provide the consulting physician with lists of all the antibiotic combinations that would be effective for the sample that was studied for a specific patient. This technique is very specific: what works in one patient may not work in another.

We recently published the results of our study, in which a large number of people with cystic fibrosis received antibiotic combinations based on our technique. The results seem to show that our technique might not be better than the standard method when selecting antibiotics to treat patients with multiresistant bacterial infections. However, patients with more serious infections may benefit from our typical process. It is important to note that our technique allows us to determine which antibiotic combinations should be avoided, in that certain combinations promote the growth of multiresistant bacteria.

Our process is very labour-intensive and requires great technical expertise. The tests cost around $300 per sample, which is what our hospital charges to test specimens referred from outside our hospital. We perform the tests at cost and hope that the results will help the consulting physicians. We are now testing only multiresistant organisms, namely bacteria for which routine laboratory tests show multiresistance to antibiotics.

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