Two Tests for Rapid Diagnosis of Resistance to Antibiotics Developed

Two new tests for the diagnosis of resistance to antibiotics, which have excellent sensitivity and specificity, would allow us to adapt antibiotic treatments to the individual's needs and to be more successful in controlling antibiotic resistance particularly in hospitals on a world-wide scale, researchers say.

These diagnostic tests will allow rapid identification of certain bacteria that are resistant to antibiotics and hence allow us to better adapt the treatment to the infected patients, avoid the inappropriate use of certain antibiotics, thus avoiding the over-use of certain wide-spectrum antibiotics and isolate patients infected with these resistant bacteria and thus avoid the development of epidemics in hospitals.

There is an ever-increasing number of emerging 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 like enterobacteriacae.

Whereas certain antibiotics like 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.

Hence, we are now faced with situations where the treatment of banal infection such as urinary or intra-abdominal infections has no effect. And this puts the life of the patients at risk. Every year, an estimated 25,000 deaths in Europe are due to multi-resistance to antibiotics.

Furthermore, the development of resistance to antibiotics affects an entire aspect of modern medicine that needs efficient antibiotics.

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 are based on the acidification properties generated by the activity of the enzymes 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.

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 2 hours as compared to 24 to 72 hours using current techniques. These tests are highly sensitive and 100 percent reliable. They are totally inoffensive since they are carried out on bacteria isolated from patients or on biological products such as urine.

"These tests are currently being assessed in order to ascertain their sensitivity directly from infected sites such as blood or urine," Patrice Nordmann, Inserm Research Director and main author of the study, said.

The findings of the study have been published in two international reviews - Emerging Infectious diseases and The Journal of Clinical Microbiology.