Drug-resistant Streptococcus pneumoniae: the beginning of the end for many antibiotics? Australian Group on Antimicrobial Resistance (AGAR)

OBJECTIVE: To determine the levels of antibiotic resistance in Streptococcus pneumoniae in Australia. DESIGN: Prospective, Australia-wide, laboratory-based survey. SETTING: 27 hospital and private laboratories around Australia, from January 1994 to August 1995. SUBJECTS: First 100 patients with clinically significant isolates of S. pneumoniae at each laboratory. OUTCOME MEASURES: Resistance to penicillin (determined from penicillin minimum inhibitory concentration [MIC] measured by the Etest), erythromycin, trimethoprim-sulfamethoxazole, tetracycline, chloramphenicol, cefotaxime and ceftriaxone. RESULTS: A total of 2396 isolates were tested (including 537 invasive isolates and 740 from children). Penicillin resistance was seen in 161 isolates (6.7%), including 17 with high level resistance. Penicillin resistance rates were significantly lower in invasive than in non-invasive strains (3.7% versus 7.6%; odds ratio [OR], 0.47; 95% confidence interval [CI], 0.28-0.77; P = 0.001). There was no significant difference in penicillin resistance rates between children (< 15 years) and adults (7.3% versus 6.5%; OR, 1.14; 95% CI, 0.80-1.63; P = 0.47). Resistance rates were higher for most other antibiotics than for penicillin (chloramphenicol, 6%; erythromycin, 11%; tetracycline, 15%; and trimethoprim-sulfamethoxazole, 42%). No high level resistance was seen to third generation cephalosporins, but 17 of 109 penicillin-resistant isolates tested (16%) displayed intermediate resistance to cefotaxime. Rates of antibiotic resistance varied between States, with the lowest rates in Tasmania. CONCLUSIONS: Antibiotic resistance levels in S. pneumoniae are increasing in Australia and high level penicillin resistance is being encountered for the first time (including in invasive strains). This will lead to an increasing number of therapeutic dilemmas and possible therapeutic failures, especially important in meningitis.