Assessment of trends of ofloxacin resistance in Mycobacterium tuberculosis

High prevalence of fluoroquinolone resistance amongst commensal flora of antibiotic naïve neonates: a study from India

BACKGROUND

The emergence of resistance amongst commensal flora is a serious threat to the community. However, there is paucity of data regarding antibiotic resistance in commensals in the absence of antibiotic pressure.

METHODS

Altogether, 100 vaginally delivered antibiotic naïve exclusively breastfed neonates were selected. Stool samples collected on day (D)1, D21 and D60 of birth were cultured. Enterobacteriaceae isolates were screened for nalidixic acid (NA) and ciprofloxacin susceptibility as per CLSI guidelines. In 28 randomly selected neonates, isolates (n=92) resistant to NA and ciprofloxacin were characterized for the presence of plasmid-mediated quinolone resistance (PMQR) genes (qnrA, qnrB and qnrS, qepAand aac(6')-Ib-cr) and mutations in the quinolone resistance determining region (QRDR) of gyrA and parC genes by specific primers and confirmed by sequencing.

RESULTS

A total of 343 Enterobacteriaceae were isolated from 100 neonates. On D1, 58 % of neonates were colonized with at least one Enterobacteriaceae predominantly E. coli. Overall resistance to NA was 60 % but ciprofloxacin resistance increased significantly from 15 % (14/96) on D1 to 38 % (50/132) on D60 (P-value <0.001). The predominant mechanism of fluoroquinolone resistance was mutation in gyrA (n=49) with or without PMQR. PMQR carrying isolates increased more than fivefold from D1 to D60.

CONCLUSION

A high level of fluoroquinolone resistance in gut flora of antibiotic naïve and exclusively breastfed neonates suggests a rampant rise of resistance in the community. The source of resistance genes on D1 is probably maternal flora acquired at birth. High load of PMQR genes in commensal flora are a potential source of spread to pathogenic organisms.

Changing prevalence and resistance patterns in children with drug-resistant tuberculosis in Mumbai

BACKGROUND

The prevalence of drug-resistant (DR) tuberculosis (TB) in children is increasing. Although, in India, multi-drug-resistant (MDR) TB rates have been relatively stable, the number of children with pre-extensively drug-resistant and extensively drug-resistant (XDR) TB is increasing.

AIM

To determine whether the prevalence of DR TB in children in Mumbai is changing and to study the evolving patterns of resistance.

METHODS

A retrospective study was undertaken in 1311 paediatric patients referred between April 2007 and March 2013 to the Paediatric TB clinic at B. J. Wadia Hospital for Children, Mumbai. Children were defined as having DR TB on the basis of drug susceptibility testing (DST) of Mycobacterium tuberculosis grown on culture of body fluids (in the case of extra pulmonary TB) or from gastric lavage/bronchi-alveolar lavage/sputum in patients with pulmonary TB or from DST of the contacts. The prevalence of DR TB was calculated and the type of DR was evaluated yearly and in the pre-2010 and post-2010 eras.

RESULTS

The overall prevalence of DR TB was 86 (6.6%) with an increase from 23 (5.6%) patients pre-2010 to 63 (7%) post-2010 (P = 0.40). Nine (10.4%) patients were diagnosed on the basis of contact with a parent with DR TB. Overall fluoroquinolone resistance increased from 9 (39.1%) pre-2010 to 59 (93.7%) post-2010 (P = 0.0001): moxifloxacin resistance increased from 2 (8.7%) to 29 (46%) (P = 0.0018) and ofloxacin resistance increased from 7 (30.4%) to 30 (47.6%) (P = 0.14). Ethionamide resistance also increased from 6 (26.1%) to 31 (49.2%) (P = 0.04), aminoglycoside resistance was one (4.3%) pre-2010 and 12 (19%) post-2010 (P = 0.17) and resistance remained virtually the same for both amikacin [0 pre-2010 and 6 (9.5%) after 2010] and kanamycin [one (4.3%) pre- and 6 (9.5%) post-2010]. Of the first-line drugs, resistance remained the same for isoniazid [23 (100%) to 61 (96.8%)], rifampicin [22 (95.7%) to 51 (80.9%),P = 0.17], pyrazinamide [15 (65.2%) to 35 (55.6%), P = 0.47], ethambutol [14 (60.9%) to 38 (60.3%), P = 1.00] and streptomycin [19 (82.6%) to 50 (79.4%), P = 1.00]. Resistance to PAS remained unchanged [2 (8.7%) to 5 (7.9%), P = 1.00].

CONCLUSION

There is increasing resistance to second-line anti-tuberculosis (ATT) drugs, particularly flouroquinolones and ethionamide. Hence, there is an urgent need to avoid the use of ATT drugs for non-tuberculous infection and to increase surveillance for DR TB in adults as MDR TB in children is usually through contact with an adult with infectious MDR TB.

Detection of ofloxacin resistance by nitrate reductase assay in Mycobacterium tuberculosis isolates from extrapulmonary tuberculosis

CONTEXT

Increased use of fluoroquinolones to treat community-acquired infections has led to the decreased susceptibility to Mycobacterium tuberculosis. There is a paucity of data on ofloxacin (OFX) resistance detection by nitrate reductase assay (NRA). Hence, the present study was carried out to find the efficacy of NRA for detection of OFX resistance in M. tuberculosis isolated from extrapulmonary tuberculosis (EPTB) cases.

AIMS

(1) To compare sensitivity, specificity and median time required to obtain results by NRA with economic variant proportion method (PM) for detection of OFX resistance.(2) To determine the extent of OFX resistance in clinical isolates of M. tuberculosis.

SETTINGS AND DESIGN

Seventy-three M. tuberculosis isolates from cases of EPTB were subjected to economic variant of PM for isoniazid, rifampicin and OFX. NRA was done for detection of OFX resistance.

SUBJECTS AND METHODS

Seventy-three isolates from clinical samples of suspected EPTB received in the Department of Microbiology were included in the study. Drug susceptibility test was performed on Lowenstein-Jensen medium with and without drugs.

STATISTICAL ANALYSIS USED

Of turnaround time was done by Mann-Whitney test on SPSS (version 19, released in 2010, IBM Corp, Armonk NY),P < 0.05.

RESULTS

OFX resistance was seen in nine isolates. The sensitivity and specificity of OFX resistance by NRA was 100% and 96.87%, respectively. Median time required to obtain results by NRA was 10 days as compared to 28 days by PM.

CONCLUSIONS

NRA is a specific and sensitive method for detection of OFX resistance in resource-restricted settings.

Fluoroquinolone-resistant tuberculosis: implications in settings with weak healthcare systems

Fluoroquinolones (FQ) play an essential role in the treatment and control of multidrug-resistant tuberculosis (MDR-TB). They are also being evaluated as part of newer regimens under development for drug-sensitive TB. As newer FQ-based regimens are explored, knowledge of FQ resistance data from high TB burden countries becomes essential. We examine available FQ resistance data from high TB burden countries and demonstrate the need for comprehensive surveys to evaluate FQ resistance in these countries. The factors driving FQ resistance in such conditions and the cost of such resistance to weak healthcare systems are discussed. The need for a comprehensive policy for addressing the issue of FQ resistance is highlighted.

Fluoroquinolone resistance in non-multidrug-resistant tuberculosis-a surveillance study in New South Wales, Australia, and a review of global resistance rates

BACKGROUND

Fluoroquinolones (FQs) are used for drug-susceptible tuberculosis (TB) in patients unable to tolerate first-line agents. Current trials are also investigating these drugs in empiric first-line TB therapy, to improve outcomes and allow for shortened treatment regimens. Widespread FQ use in the community has resulted in FQ resistance in many microorganisms, including Mycobacterium tuberculosis. Despite this, FQ drug susceptibility testing (DST) is rarely performed in non-multidrug-resistant TB (non-MDR-TB).

METHODS

We conducted a 1-year surveillance study of FQ resistance on all MTB isolates from New South Wales (NSW), Australia. In addition, we performed a literature review of previous studies assessing FQ resistance in non-MDR-TB to summarize the global extent of this resistance pattern.

RESULTS

Two (0.6%) out of 357 MTB isolates from NSW were found to be FQ-resistant. One isolate was an MDR strain (11% of all MDR-TB). The other was isoniazid-monoresistant (0.3% of all non-MDR-TB). Eleven studies from 10 countries had performed FQ resistance surveillance on non-MDR-TB. In the majority of these studies, FQ resistance was found to be low (mean 1%; 95% confidence interval 0.2-2%).

CONCLUSIONS

FQ resistance in non-MDR-TB is uncommon in NSW, Australia. The existing global evidence suggests that FQ resistance remains largely confined to MDR-TB strains. In the majority of TB endemic regions, however, FQ resistance in non-MDR-TB has not been assessed. Knowledge of the prevalence of FQ resistance in MTB is essential to guide the rational use of these drugs, including their feasibility as first-line agents.

Prevalence of gyrA and B gene mutations in fluoroquinolone-resistant and -sensitive clinical isolates of Mycobacterium tuberculosis and their relationship with MIC of ofloxacin

The study was done to know the prevalent mutations of gyrA and gyrB genes, and their significance with drug resistance in clinical isolates of Mycobacterium tuberculosis. A total of 100 ofloxacin- (OFX) resistant and 100 OFX-sensitive isolates of M. tuberculosis were consecutively selected from routine Tuberculosis laboratory. Drug resistance pattern of these isolates was recorded. MIC of OFX was tested in all these isolates by absolute concentration method. Quinolone resistance determining region (QRDR) of gyrA and gyrB genes of 320 and 428 bp, respectively, were amplified and sequenced. Sequencing data were analyzed by BLAST on NCBI with reference strain H37Rv. Of 100 OFX-sensitive isolates, 30 were pansusceptible, 28 were monoresistant, 10 were polyresistant and 32 were multidrug resistant (MDR). Among 100 OFX-resistant isolates, 19 were OFX monoresistant, 16 were polyresistant and 65 were MDR. Mutations in gyrA and gyrB genes were observed in 79% and 5% of OFX-resistant isolates, respectively. Most prevalent mutation was found at codon 94 in QRDR of gyrA gene. Double mutations found in gyrA gene and in both gyrA and gyrB genes signifies higher levels of OFX resistance. In one isolate, a substitution at codon 592 (Pro592Ser) was found as a novel mutation outside the QRDR of gyrB gene. Our findings support previous studies that the OFX resistance to M. tuberculosis is associated with mutations in the QRDR of gyrA gene; however, the level of OFX resistance may not be predicted based on the mutation patterns in the gyrA gene.

Alignment of new tuberculosis drug regimens and drug susceptibility testing: a framework for action

New tuberculosis drug regimens are creating new priorities for drug susceptibility testing (DST) and surveillance. To minimise turnaround time, rapid DST will need to be prioritised, but developers of these assays will need better data about the molecular mechanisms of resistance. Efforts are underway to link mutations with drug resistance and to develop strain collections to enable assessment of new diagnostic assays. In resource-limited settings, DST might not be appropriate for all patients with tuberculosis. Surveillance data and modelling will help country stakeholders to design appropriate DST algorithms and to decide whether to change drug regimens. Finally, development of practical DST assays is needed so that, in countries where surveillance and modelling show that DST is advisable, these assays can be used to guide clinical decisions for individual patients. If combined judiciously during both development and implementation, new tuberculosis regimens and new DST assays have enormous potential to improve patient outcomes and reduce the burden of disease.