Researchers who developed two ultra-rapid new tests, designed for worldwide use, say they dramatically speed up the diagnosis of antibiotic resistant infections and will improve our ability to control antibiotic resistance, which is emerging at an alarming rate globally among a number of bacterial species.

The team, from INSERM, the National Institute of Health and Medical Research in France, write about their work in two international reviews that were published in September: Emerging Infectious Diseases and The Journal of Clinical Microbiology.

In a separate statement issued more recently on 12 October they write:

“With their excellent sensitivity and specificity, the use of these extremely efficient tests on a world-wide scale would allow us to adapt antibiotic treatments to the individual’s needs and to be more successful in controlling antibiotic resistance, particularly in hospitals.”

The growing problem of antibiotic resistance is causing increasing concern and putting patients’ lives at risk. Every year, an estimated 25,000 people in Europe die because of multi-resistance to antibiotics, say the researchers.

Not only should the new tests allow doctors adapt treatments to infected patients, but they should also help avoid inappropriate use of certain antibiotics, which in turn reduces the over-use that drives resistance.

More rapid diagnosis should also allow hospitals to isolate patients infected with resistant bacteria and thus avert hospital-wide epidemics.

The researchers also point out that an increasing number of emerging bacteria are causing cross-border epidemics, particularly Gram-negative species such as enterobacteriacae, a large family that includes familiar pathogens such as Salmonella and E. coli.

It is not the number of bacteria that is the problem, so much as their increasing resistance to antibiotics, they note.

They explain that even commonplace infections are getting hard to treat, with some, including certain urinary and stomach infections, now totally resistant. Plus, whereas certain antibiotics such as wide-spectrum cephalosporins were reserved only for the most serious infections, in some cases they are totally inactive against the bacteria, for which there is now no effective antibiotic treatment.

A contributing factor to their rapid spread, is that multiresistant strains are crossing from one country into another undetected.

Effective antibiotics are also desperately needed in more specialized areas of modern medicine: such as to prevent infection following grafts, transplants and major surgery.

Current methods of detecting antibiotic resistance are costly, time-consuming and not totally reliable.

To develop the new tests, the researchers focused on two enzymes (ß-lactamases and carbapenemases) that are responsible for causing antibiotic resistance in bacteria treated with two classes of common antibiotics: wide-spectrum cephalosprins and carpabenems.

The presence of the corresponding enzyme means the bacterium is resistant to that class of antibiotic.

The tests (Corba NP test and ESBL NDP test) look for changes in acidity generated by the enzymes when they are in the presence of the antibiotic. If either of the enzymes is present, the medium turns acid and the acidity indicator (pH) turns from red to yellow.

The tests are non-invasive and can be done on bacteria taken from a urine or stool sample. The results are ready in 2 hours: considerably less time than the current methods which typically take 24 to 72 hours.

The researchers say the tests are also 100% reliable, relatively simple and cheap to administer: they estimate the cost at 4 to 5 Euros each.

“Used straight at the patient’s bedside, these tests will help us to optimise the use of antibiotic treatment, in particular in the developing countries where the levels of resistance are extremely high,” says the press statement.

Senior author Patrice Nordmann, a Research Director at INSERM, adds:

“These tests are currently being assessed in order to ascertain their sensitivity directly from infected sites such as blood or urine”.

The team describes their invention as a “breakthrough” in the fight against antibiotic resistance.

With a cheap, fast and simple test, doctors will be able to rapidly detect the most serious cases of antibiotic resistance, which in turn should limit the spread of the problem, and as Nordmann explains:

“We can hope, in particular in many Western countries where the situation has not yet reached endemic proportions multi-resistances (France, in particular), to be able to preserve to a certain extent the efficiency of wide-spectrum cephalosporins and carbapenems, antibiotics used as a ‘last resource’.”

International patent applications have already been filed for the tests. And while they should be commercially available within 12 to 16 month, the technique is also available for any lab wishing to develop their own.

Written by Catharine Paddock PhD