Fluoroquinolone (FQ) antibiotics are a key component of treatment of multi-drug resistant tuberculosis (MDR-TB) and are also used against drug susceptible TB in patients intolerant of any first-line agents.
Australia has a low incidence of TB (5-6 cases/100,000 population) with the majority of patients being born and/or acquiring their infection overseas, most commonly from the Subcontinent, the Philippines, Vietnam and China. Over the past ten years, we have observed a shift in the epidemiology of Mycobacterium tuberculosis (MTB) in NSW from a predominance of East Asian lineages to Indo Oceanic strains.
There have also been reports, from some of these geographic regions, of an alarming increase in MTB fluoroquinolone resistance attributed to the widespread use of fluoroquinolones for treatment of respiratory and gastrointestinal syndromes in primary care.
Fluoroquinolone resistance surveillance was prospectively conducted at the NSW Mycobacterium Reference Laboratory, Westmead Hospital between February 2013 and January 2014. Susceptibility testing on all new MTB isolates in NSW is routinely performed in this facility. MTB isolates found to be phenotypically resistant to Ofloxacin underwent gyrA gene PCR and DNA sequencing. Minimum inhibitory concentrations (MICs) to Ofloxacin and Moxifloxacin were additionally determined .
Our results indicate that FQ resistance in MDR-TB and non MDR-TB in NSW remains uncommon. The lack of laboratory surveillance studies in the majority of regions where TB is endemic hampers our knowledge of the global extent of FQ resistance. Periodic surveillance of FQ resistance in MTB should be integral to the rational and cost-effective use of FQ and ascertaining their feasibility as empiric first line anti-TB agents in Australia and overseas.