Rapidly emerging antimicrobial resistances in Streptococcus pneumoniae in Australia

Objective: To examine the prevalence of resistance in Streptococcus pneumon iae to key antimicrobials in Australia during 1997. Design: Prospective, Australia-wide, laboratory-based survey. Setting: 11 microbiology laboratories from seven Australian States and Terr itories (five private laboratories and six public hospital laboratories) be tween March and November 1997. Strains: Up to 100 consecutive, clinically significant strains of S. pneumo niae isolated by each laboratory. Main outcome measures: Susceptibility to penicillin, amoxycillin-clavulanat e, cefaclor, ceftriaxone, erythromycin, tetracycline, and sulfamethoxazole- trimethoprim (cotrimoxazole), measured by a gradient diffusion, minimum inh ibitory concentration technique. Results: Of 1020 strains, 16.8% had intermediate susceptibility to penicill in and 8.6% were resistant. Rates of resistance to other drugs were: amoxyc illin-clavulanate, 3.1%; cefaclor, 21.4%; ceftriaxone, 3.1%; erythromycin, 15.6%; tetracycline, 15.7%; and cotrimoxazole, 33.4%. Non-invasive isolates harboured more resistances than invasive isolates, and resistance was more prevalent in isolates from children under two years. Multiple resistance w as also common, with 21.2% of strains resistant to two or more classes of d rug, and 9.3% of non-invasive and 1.7% of invasive isolates resistant to fo ur classes. There were no obvious differences in resistance rates between p rivate and public hospital laboratories. Conclusions: Rates of antimicrobial resistance are rising rapidly in S. pne umoniae in Australia. Recommendations for empiric treatment of invasive and respiratory infection need to take account of these changes.