Antimicrobial resistances among Shigella in New Zealand

To determine the prevalence of antimicrobial resistances among recent isolates of Shigella in New Zealand.

A total of 107 Shigella isolates referred to the Institute of Environmental Science and Research from 20 hospital and community laboratories between January and June 1996 were tested by an agar dilution method.

Shigella sonnei accounted for 70% of the isolates and S flexneri for 23%. Resistance to ampicillin and cotrimoxazole was detected in 42% and 57% of the isolates respectively, and combined ampicillin and co-trimoxazole resistance occurred in 30.8% of the isolates. The prevalence of cephalothin resistance was 5.6%. Resistance to cefotaxime, ciprofloxacid and gentamicin was not detected and 31.8% were sensitive to all agents tested. Ampicillin resistance was significantly more prevalent in S flexneri than S sonnei.

The high prevalence of ampicillin and cotrimoxazole resistance indicates that ampicillin and cotrimoxazole are no longer useful for empirical treatment of shigellosis in New Zealand. The findings indicate a need to monitor the prevalence of antimicrobial resistances among Shigella and suggest that antimicrobial susceptibility testing might be needed to guide antimicrobial therapy.