Antibiotic susceptibility of Streptococcus pneumoniae in New Zealand

To determine the current antibiotic susceptibility patterns of Streptococcus pneumoniae from four centres in New Zealand.

Over a six-month period in 1997, 386 consecutive clinical isolates of S pneumoniae were collected by four laboratories (Auckland, Wellington, Hamilton and Christchurch) from general practice or inpatients. Susceptibility testing for seven antibiotics was performed by each centre using the Etest.

Eighty-three-percent of isolates were penicillin susceptible, 12% showed intermediate resistance to penicillin and 5% were penicillin resistant. Overall, 93 and 91% of isolates were susceptible to amoxicillin/clavulanic acid and ceftriaxone, respectively. Erythromycin and tetracycline had similar rates of susceptibility (88 and 87%, respectively). Resistance to cotrimoxazole was common, with only 57% of isolates susceptible to this combination. No National Committee for Clinical Laboratory Standard (NCCLS) breakpoints were available for cefaclor to allow interpretation of the minimum inhibitory concentration data for this agent. Wellington had lower resistance rates than Auckland, Christchurch and Hamilton. Isolates from children had consistently higher resistance rates (two- to five-fold greater for beta-lactams and 1.2 to 1.3-fold for other agents) compared with isolates from adult patients.

Resistance to multiple antibiotics among S pneumoniae is now evident in New Zealand, although rates varied between study centres. The overall rate of penicillin resistance is 5%, which is similar to that observed in many European and US cities but lower than the rates reported in badly affected areas (> 30%). These data suggest that amoxicillin (+/- clavulanic acid), erythromycin or tetracycline are appropriate agents for empirical use in less serious community acquired infections when S pneumoniae is suspected. Ceftriaxone, with or without vancomycin, should be considered in the empirical treatment of invasive, disease until sensitivities are known.