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Tests Target More Rapid Diagnosis Of Antibiotics Resistance

Fri, 10/12/2012 - 7:18am

With their sensitivity and specificity, the use of these tests on a world-wide scale could allow for adapting antibiotic treatments to an individual's needs, and to be more successful in controlling antibiotic resistance, particularly in hospitals. These works were published in Emerging Infectious diseases and The Journal of Clinical Microbiology. These diagnostic tests will allow rapid identification of certain bacteria that are resistant to antibiotics, helping to curb the inappropriate use of certain antibiotics and isolate patients infected with these resistant bacteria in helping to avoid the development of epidemics in hospitals.

There is an ever-increasing number of bacteria that cause cross-border epidemics. Researchers all agree on the fact that it is not the number of bacteria that is the problem, but their increasing resistance to antibiotics. The situation is particularly dramatic for certain species of bacteria, Gram-negative bacilli such as enterobacteriacae .

Whereas certain antibiotics such as wide-spectrum cephalosporins used to be reserved for the most serious cases, now there are cases where they are totally inactive against certain bacterial germs and consequently there is no effective antibiotic treatment for these. Furthermore, the development of resistance to antibiotics affects an entire aspect of modern medicine that needs efficient antibiotics (grafts, transplants, major surgery, reanimation, etc.).Undetected importation of multiresistant strains from foreign countries can also considerably accelerate the diffusion of this multiresistance phenomenon.

In an attempt to slow down these increasing resistances, the Inserm researchers have developed a system that can rapidly detect the two enzymes responsible for causing resistance to the bacteria of two classes of common antibiotics: wide-spectrum cephalosprins and carpabenems. In these tests, the presence of an enzyme indicates the presence of a resistant bacteria.

These tests (Corba NP test and ESBL NDP test) are based on the acidification properties generated by the activity of the enzymes (ß-lactamases and carbapenemases) when they are in the presence of an antibiotic. If any one of these enzymes is present, the medium becomes acid and the acidity indicator (pH) turns from red to yellow (Figure, Corba NP test).

At present, these tests can be performed using bacteria isolated from urine samples taken during a detected infection, or from bacteria present in stools. The result is obtained in less than two hours (compared to 24 to 72 hours using current techniques). These tests are highly sensitive and highly reliable (100 percent). They are totally inoffensive since they are carried out on bacteria isolated from patients or on biological products such as urine, etc.

Patrice Nordmann, Inserm Research Director and main author of this work, points out that "These tests are currently being assessed in order to ascertain their sensitivity directly from infected sites such as blood or urine". The invention of these tests is an important breakthrough in the fight against the resistance to antibiotics. These tests will provide a simple, inexpensive means of detecting the most serious cases of resistance to antibiotics in human medicine and will contribute to limiting international diffusion.

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