Antibiotic-Resistant Tuberculosis: Relatively Low Rate In France

Main Category: Tuberculosis
Also Included In: Infectious Diseases / Bacteria / Viruses
Article Date: 26 Oct 2007 - 13:00 PDT

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Resistance to the antibiotics that specifically target the tuberculosis (TB) bacillus is a severe challenge in developing countries, yet seems relatively uncommon among subjects born in France who have not previously been treated for TB.

So concludes an important study by Jérôme Robert and his team (Université Pierre et Marie Curie-Paris 6, Laboratoire de Bactériologie-Hygiène) in the forthcoming issue of the European Respiratory Journal (ERJ).

It finds, in particular, that the principal risk factors for resistance to first-line anti-TB drugs are having already been treated for the disease, or having been born in a country where resistance rates are high. Co-infection with HIV is also a significant risk factor.

With ten million new cases and two million fatalities every year, TB is a leading cause of mortality worldwide, particularly in the developing countries, where it frequently occurs in conjunction with AIDS.

Koch's bacillus is becoming increasingly resistant to antibiotics, and this is a major challenge in controlling the disease globally.

Catastrophic outlook

The phenomenon of multi-resistance (resistance of the bacillus to two of the most powerful first-line anti-TB drugs, isoniazid and rifampicin) affects over 1.5 million patients, according to the World Health Organization (WHO).

Even more alarmingly, since 2006 ultra-resistant forms have also been identified (with resistance not only to isoniazid and rifampicin, but also to second-line drugs); in these cases there is a catastrophic outlook for affected patients since there is practically no means of saving them.

In response, WHO has developed guidelines for monitoring antibiotic-resistant TB and identifying the most vulnerable patients.

These guidelines have also been adapted for European countries, where the disease is much rarer and there are lower levels of drug resistance.

Major network

So what is the situation in countries with low levels of infection, such as France, with 9.2 cases per 100,000 population?

This was what Jérôme Robert's team set out to examine in their prospective study, using data gathered over ten years from a large network of university laboratories. In total, the data cover 13,283 patients.

At the start of the study, the network already included 17 laboratories, which covered some 10% of the TB cases recorded in France.

The network continued to expand, and by 2004 contained 33 laboratories, which covered almost a third of TB cases in France.

One in ten TB patients also has AIDS

As Robert explains in the ERJ article, the data on the 13,283 patients were studied in great detail.
Two-thirds of them were male, approximately half were of French origin and 10% were co-infected with the AIDS virus.

"The proportion of subjects co-infected with AIDS is higher among patients of foreign origin (13.6%) than among those of French origin (7.5%)", the authors explain, pointing out that the proportion of TB patients born abroad increased during the ten years of monitoring.

They also noted that TB was confined to the lungs in seven out of ten cases, while 22% of patients had extrapulmonary TB. The remaining 8% were mixed cases (with pulmonary and extrapulmonary TB).

Most of the subjects (80%) had never been treated before, while 8% had already received a course of anti-TB treatment lasting at least a month.

Previously treated patients at greater risk

The results published in the ERJ show that the rate of TB cases with resistance to first-line drugs is 8.8% among patients who have not been treated for the disease previously.

Streptomycin resistance is the commonest form (6.6%), followed by isoniazid resistance (4.2%).

These levels are comparable to those recorded in other European countries, the authors note. But resistance is significantly commoner among patients born abroad (11%) than in those born in France (7%). HIV co-infection is also a risk factor for resistance. Meanwhile, the dreaded multi-resistance was rare (0.7% of cases) among this subject group.

The situation is very different among patients previously treated for TB. One in five of these displayed resistance to anti-TB drugs, and this proportion remained constant over the ten years of the study.

Risk factors for resistance

"Our data confirm that TB rates are declining in France, and particularly among subjects born here," Robert concludes.

"Our study also shows that drug-resistant tuberculosis is not a major public health problem in our country, at least among subjects who have not been treated before."

He suggests that the two main risk factors, namely having been born in a country with a high level of resistance or having previously received treatment with an anti-TB drug, should be screened for systematically before a TB treatment is selected.

Systematic monitoring by networks like the one that provided the data for this study (which remains in operation) also makes it possible to keep track of the level of multi-resistant TB, which has increased in France recently.

European Respiratory Journal