Rapidly emerging antimicrobial resistances in Streptococcus pneumoniae in Australia. Pneumococcal Study Group

Abstract

Objective: To examine the prevalence of resistance in Streptococcus pneumoniae to key antimicrobials in Australia during 1997.

Design: Prospective, Australia-wide, laboratory-based survey.

Setting: 11 microbiology laboratories from seven Australian States and Territories (five private laboratories and six public hospital laboratories) between March and November 1997. STRAINS: Up to 100 consecutive, clinically significant strains of S. pneumoniae isolated by each laboratory.

Main outcome measures: Susceptibility to penicillin, amoxycillin-clavulanate, cefaclor, ceftriaxone, erythromycin, tetracycline, and sulfamethoxazole-trimethoprim (cotrimoxazole), measured by a gradient diffusion, minimum inhibitory concentration technique.

Results: Of 1020 strains, 16.8% had intermediate susceptibility to penicillin and 8.6% were resistant. Rates of resistance to other drugs were: amoxycillin-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 was also common, with 21.2% of strains resistant to two or more classes of drug, and 9.3% of non-invasive and 1.7% of invasive isolates resistant to four classes. There were no obvious differences in resistance rates between private and public hospital laboratories.

Conclusions: Rates of antimicrobial resistance are rising rapidly in S. pneumoniae in Australia. Recommendations for empiric treatment of invasive and respiratory infection need to take account of these changes.