Nicolas Veziris

Assessment of Clarithromycin Susceptibility in Strains Belonging to the Mycobacterium abscessus Group by erm(41) and rrl Sequencing

ABSTRACT Clarithromycin was the drug of choice for Mycobacterium abscessus infections until inducible resistance due to erm(41) was described. Because M. abscessus was split into M. abscessus sensu stricto, Mycobacterium massiliense, and Mycobacterium bolletii, we looked for erm(41) in the three species and determined their clarithromycin susceptibility levels. Ninety strains were included: 87 clinical strains from cystic fibrosis patients (61%) and others (39%), representing 43 M. abscessus, 30 M. massiliense, and 14 M. bolletii strains identified on a molecular basis, and 3 reference strains. Clarithromycin and azithromycin MICs were determined by broth microdilution and Etest with a 14-day incubation period. Mutations in rrl (23S rRNA gene) known to confer acquired clarithromycin resistance were also sought. erm(41) was detected in all strains but with two deletions in all M. massiliense strains. These strains were indeed susceptible to clarithromycin (MIC90 of 1 μg/ml) except for four strains with rrl mutations. M. abscessus strains harbored an intact erm(41) but had a T/C polymorphism at the 28th nucleotide: T28 strains (Trp10 codon) demonstrated inducible clarithromycin resistance (MIC90 of >16 μg/ml), while C28 strains (Arg10) were susceptible (MIC90 of 2 μg/ml) except for two strains with rrl mutations. M. bolletii strains had erm(41) sequences similar to the sequence of the T28 M. abscessus group, associated with inducible clarithromycin resistance (MIC90 of >16 μg/ml). erm(41) sequences appeared species specific within the M. abscessus group and were fully concordant with clarithromycin susceptibility when erm(41) sequencing was associated with detection of rrl mutations. Clarithromycin-resistant strains, including the six rrl mutants, were more often isolated in cystic fibrosis patients, but this was not significantly associated with a previous treatment.

Synergistic Activity of R207910 Combined with Pyrazinamide against Murine Tuberculosis

ABSTRACT In previous studies, the diarylquinoline R207910 (also known as TMC207) was demonstrated to have high bactericidal activity when combined with first- or second-line antituberculous drugs. Here we extend the evaluation of R207910 in the curative model of murine tuberculosis by assessing the activities of one-, two-, and three-drug combinations containing R207910 and isoniazid (INH), rifampin (RIF), pyrazinamide (PZA), or moxifloxacin (MXF) in the setting of a high initial bacillary load (7.2 log10 CFU). Two months of treatment with the combinations R207910-PZA, R207910-PZA-INH, R207910-PZA-RIF, or R207910-PZA-MXF resulted in culture-negative lung homogenates in 70 to 100% of the mice, while mice treated with INH-RIF-PZA (the reference regimen) or RIF-MXF-PZA remained culture positive. Combinations including R207910 but not PZA (e.g., R207910-INH-RIF and R207910-MXF-RIF) were less active than R207910-PZA-containing regimens administered either alone or with the addition of INH, RIF, or MXF. These results reveal a synergistic interaction between R207910 and PZA. Three-drug combinations containing these two drugs and INH, RIF, or MXF have the potential to significantly shorten the treatment duration in patients, provided that these results can be confirmed in long-term experiments including periods of relapse.

Molecular Investigation of Resistance to the Antituberculous Drug Ethionamide in Multidrug-Resistant Clinical Isolates of Mycobacterium tuberculosis

ABSTRACT Ethionamide (ETH) needs to be activated by the mono-oxygenase EthA, which is regulated by EthR, in order to be active against Mycobacterium tuberculosis. The activated drug targets the enzyme InhA, which is involved in cell wall biosynthesis. Resistance to ETH has been reported to result from various mechanisms, including mutations altering EthA/EthR, InhA and its promoter, the NADH dehydrogenase encoded by ndh, and the MshA enzyme, involved in mycothiol biosynthesis. We searched for such mutations in 87 clinical isolates: 47 ETH-resistant (ETHr) isolates, 24 ETH-susceptible (ETHs) isolates, and 16 isolates susceptible to ETH but displaying an intermediate proportion of resistant cells (ETHSip; defined as ≥1% but <10% resistant cells). In 81% (38/47) of the ETHr isolates, we found mutations in ethA, ethR, or inhA or its promoter, which mostly corresponded to new alterations in ethA and ethR. The 9 ETHr isolates without a mutation in these three genes (9/47, 19%) had no mutation in ndh, and a single isolate had a mutation in mshA. Of the 16 ETHSip isolates, 7 had a mutation in ethA, 8 had no detectable mutation, and 1 had a mutation in mshA. Finally, of the 24 ETHs isolates, 23 had no mutation in the studied genes and 1 displayed a yet unknown mutation in the inhA promoter. Globally, the mechanism of resistance to ETH remained unknown for 19% of the ETHr isolates, highlighting the complexity of the mechanisms of ETH resistance in M. tuberculosis.

Comparing Mycobacterium massiliense and Mycobacterium abscessus lung infections in cystic fibrosis patients

BACKGROUNDnMycobacterium massiliense is closely related to Mycobacterium abscessus and is also a frequent cause of mycobacterial lung disease in patients with cystic fibrosis (CF). There has been no previous investigation of possible differences between M. massiliense and M. abscessus infections in the setting of CF.nnnMETHODSnWe studied a prospective cohort of 16 M. massiliense and 27 M. abscessus lung infection cases with CF, with a mean follow-up of 6 years.nnnRESULTSnM. massiliense cases were younger than M. abscessus cases (mean age: 12.8 vs 17.1 years; p=0.02) at the time of the first mycobacterial isolation and also had lower body mass index values (mean: 16.4 vs 19.3 kg/m(2), p=0.002). All M. massiliense cases, except one, had negative BMI Z-score values at the time of the first mycobacterial isolation (11/12 vs 16/23 M. abscessus cases, p=0.04). Clarithromycin-based combination therapies led to mycobacterial eradication in 100% of M. massiliense cases but only in 27% of M. abscessus cases (p=0.009).nnnCONCLUSIONnOur data show a particular link between M. massiliense and malnutrition specifically in CF patients. Unlike M. abscessus, the bacteriological response of M. massiliense to combination antibiotic therapies containing clarithromycin was excellent. Distinguishing between M. massiliense and M. abscessus has major clinical implications for CF patients.

In Vivo Evaluation of Antibiotic Activity Against Mycobacterium abscessus

BACKGROUNDnThe prognosis of Mycobacterium abscessus infections is poor due to the lack of effective drug treatment. The objective of this study was to set up an animal model suitable to test antibiotic activity against M. abscessus.nnnMETHODSnThe following mouse strains were evaluated: Swiss, BALB/c, C57BL/6, nude, beige, A/J, and GKO. Antibiotic activity was tested for clarithromycin, amikacin, cefoxitin, tigecycline, and bedaquiline (TMC207). Finally, we evaluated the 3-drug combination clarithromycin, cefoxitin, and amikacin.nnnRESULTSnNude and GKO mice fulfilled criteria for the model but only nude mice offered sufficient availability for large therapeutic experiments. Among the 3 drugs usually combined for treatment of M. abscessus infection, cefoxitin was the most active because it improved survival and reduced bacillary loads in spleen whereas clarithromycin and amikacin prevented death but had little impact on bacillary loads. The triple-drug combination was not more active than cefoxitin alone. Tigecycline displayed bactericidal activity whereas bedaquiline was almost inactive.nnnCONCLUSIONSnNude mice are an adequate model for in vivo chemotherapy studies. Among tested drugs, cefoxitin and tigecycline showed promising in vivo activity against M. abscessus. The best drug combination remains to be determined.

Electronic sensors for assessing interactions between healthcare workers and patients under airborne precautions.

Background Direct observation has been widely used to assess interactions between healthcare workers (HCWs) and patients but is time-consuming and feasible only over short periods. We used a Radio Frequency Identification Device (RFID) system to automatically measure HCW-patient interactions. Methods We equipped 50 patient rooms with fixed sensors and 111 HCW volunteers with mobile sensors in two clinical wards of two hospitals. For 3 months, we recorded all interactions between HCWs and 54 patients under airborne precautions for suspected (nu200a=u200a40) or confirmed (nu200a=u200a14) tuberculosis. Number and duration of HCW entries into patient rooms were collected daily. Concomitantly, we directly observed room entries and interviewed HCWs to evaluate their self-perception of the number and duration of contacts with tuberculosis patients. Results After signal reconstruction, 5490 interactions were recorded between 82 HCWs and 54 tuberculosis patients during 404 days of airborne isolation. Median (interquartile range) interaction duration was 2.1 (0.8–4.4) min overall, 2.3 (0.8–5.0) in the mornings, 1.8 (0.8–3.7) in the afternoons, and 2.0 (0.7–4.3) at night (P<10−4). Number of interactions/day/HCW was 3.0 (1.0–6.0) and total daily duration was 7.6 (2.4–22.5) min. Durations estimated from 28 direct observations and 26 interviews were not significantly different from those recorded by the network. Conclusions The RFID was well accepted by HCWs. This original technique holds promise for accurately and continuously measuring interactions between HCWs and patients, as a less resource-consuming substitute for direct observation. The results could be used to model the transmission of significant pathogens. HCW perceptions of interactions with patients accurately reflected reality.

A surge of MDR and XDR tuberculosis in France among patients born in the Former Soviet Union.

A marked increase in the number of multidrug-resistant (MDR) tuberculosis (TB) cases entirely related to patients born in the Former Soviet Union was observed in France in the last two years. Very few cases were clustered, suggesting it is a consequence of recent immigration of patients already infected in their country of origin. This major increase challenges the existing structures for management of MDR and extensively drug-resistant TB (XDR-TB).

Efficient intermittent rifapentine-moxifloxacin-containing short-course regimen for treatment of tuberculosis in mice.

ABSTRACT Long-half-life drugs raise the hope of once-a-week administration of antituberculous treatment. In a previous study with the murine model of tuberculosis, the most active intermittent regimen which contained rifapentine (RFP), isoniazid (INH), and moxifloxacin (MXF) given once a week during 5.5 months, preceded by 2 weeks of daily treatment with INH, rifampin (RIF), pyrazinamide (PZA), and MXF, was less active than the standard 6-month daily RIF-INH-PZA regimen. We evaluated with the same model similar regimens in which we increased the dosing of rifapentine from 10 to 15 mg/kg of body weight and of moxifloxacin from 100 to 400 mg/kg. Mice infected intravenously by 6.2 ×106 CFU of Mycobacterium tuberculosis H37Rv were treated 2 weeks later when infection was established. After 6 months of treatment, all mice had negative lung culture. After 3 months of follow-up, no relapse occurred in the two groups that received moxifloxacin at 400 mg/kg, whatever the dosage of RFP, and in the group receiving the standard RIF-INH-PZA control regimen. In contrast, in the two groups receiving moxifloxacin at a lower dosage, the relapse rate was significantly higher (13% in mice receiving RFP at 15 mg/kg and 27% in those receiving RFP at 10 mg/kg). Finally, the fully intermittent once-a-week regimen (26 drug ingestions) of INH, RFP (15 mg/kg), and MXF (400 mg/kg) led to a relapse rate of 11%. In conclusion, when used at high dosage, rifapentine and moxifloxacin are very efficient when combined with isoniazid in a once-a-week treatment in mouse tuberculosis.

Increase in primary drug resistance of Mycobacterium tuberculosis in younger birth cohorts in France.

BACKGROUNDnMonitoring of primary drug resistance is of interest for long-term evaluation of the efficacy of a national tuberculosis program. The objective was to describe changes over time in primary drug resistance among new tuberculosis patients.nnnMETHODSnStratified analysis by birth cohorts, region of birth, HIV-coinfection of data from 14,610 culture-positive new tuberculosis patients diagnosed by a network of university hospitals between 1995 and 2008.nnnRESULTSnHalf of the patients were foreign-born, and 9% HIV-coinfected. For foreign-born and French-born patients, there was an upward trend in resistance rates to streptomycin, isoniazid, and rifampicin from the oldest to the youngest cohorts. For a same age at tuberculosis diagnosis, the risk of isoniazid resistance was higher in younger cohorts, revealing a cohort effect. Among French-born patients, the only factor independently associated with primary resistance to streptomycin, or isoniazid was birth after 1950, and particularly after 1980. Risk of streptomycin resistance increased in youngest cohorts among European-born patients. HIV-coinfection was associated to rifampicin resistance among foreign-born and French-born patients,nnnCONCLUSIONSnTheses results indicate that among French-born patients, isoniazid-resistant strains are currently circulating in younger patients that are more likely to be infected recently, and that among foreign-born patients, HIV-coinfection is a strong risk factor for primary resistance.

Mycobacterial infection of breast prosthesis – a conservative treatment: a case report

BackgroundBacterial infection is a well-known risk of breast implant surgery. It is typically caused by bacterial skin flora, specifically Staphylococcus aureus and the coagulase negative staphylococci. There have been infrequent reports of breast implant infection caused by the atypical mycobacteria, of which Mycobacterium canariasense not yet reported in the literature.Case presentationThis report summarizes the case of a female patient who underwent mastectomy followed by bilateral breast augmentation and presented approximately three years later with clinical evidence of infected breast prosthesis by Mycobacterium canariasense. One year after thoroughly follow-up, appropriate antibiotherapy and the change of the infected prosthesis, the patient presented no signs of reinfection.ConclusionOur case demonstrates that Mycobacterium canariasense should be considered as a new potential cause of infected breast prosthesis.