Susceptibility testing of extensively drug-resistant and pre-extensively drug-resistant Mycobacterium tuberculosis against levofloxacin, linezolid, and amoxicillin-clavulanate

Antimicrob Agents Chemother. 2013 Jun;57(6):2522-5. doi: 10.1128/AAC.02020-12. Epub 2013 Mar 18.

Abstract

Pakistan is a high-burden country for tuberculosis (TB). The emergence and increasing incidence of extensively drug-resistant (XDR) TB has been reported in Pakistan. Similarly, the prevalence of multidrug-resistant TB infections with fluoroquinolone resistance (pre-XDR) is also increasing. To treat these infections, local drug susceptibility patterns of alternate antituberculosis agents, including levofloxacin (LVX), linezolid (LZD), and amoxicillin-clavulanate (AMC), is urgently needed. The aim of this study was to determine the susceptibility frequencies of drug-resistant (DR) Mycobacterium tuberculosis against LVX, LZD, and AMC. All susceptibilities were determined on Middlebrook 7H10 agar. A critical concentration was used for LVX (1 μg/ml), whereas MICs were determined for LZD and AMC. M. tuberculosis H37Rv was used as a control strain. A total of 102 M. tuberculosis isolates (XDR, n = 59; pre-XDR, n = 43) were tested. Resistance to LVX was observed in 91.2% (93/102). Using an MIC value of 0.5 μg/ml as a cutoff, resistance to LZD (MIC ≥ 1 μg/ml) was noted in 5.9% (6/102). Although the sensitivity breakpoints are not established for AMC, the MIC values were high (>16 μg/ml) in 97.1% (99/102). Our results demonstrate that LZD may be effective for the treatment of XDR and pre-XDR cases from Pakistan. High resistance rates against LVX in our study suggest the use of this drug with caution for DR-TB cases from this area. Drug susceptibility testing against LVX and AMC may be helpful in complicated and difficult-to-manage cases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetamides / pharmacology*
  • Amoxicillin-Potassium Clavulanate Combination / pharmacology*
  • Antitubercular Agents / pharmacology*
  • Extensively Drug-Resistant Tuberculosis / epidemiology
  • Extensively Drug-Resistant Tuberculosis / microbiology*
  • Humans
  • Levofloxacin*
  • Linezolid
  • Microbial Sensitivity Tests
  • Mycobacterium tuberculosis / drug effects*
  • Mycobacterium tuberculosis / isolation & purification
  • Ofloxacin / pharmacology*
  • Oxazolidinones / pharmacology*
  • Pakistan / epidemiology
  • Tuberculosis, Multidrug-Resistant / epidemiology
  • Tuberculosis, Multidrug-Resistant / microbiology*
  • Tuberculosis, Pulmonary / epidemiology
  • Tuberculosis, Pulmonary / microbiology

Substances

  • Acetamides
  • Antitubercular Agents
  • Oxazolidinones
  • Levofloxacin
  • Amoxicillin-Potassium Clavulanate Combination
  • Ofloxacin
  • Linezolid