Pneumococci causing invasive disease in New Zealand, 1987-94: serogroup and serotype coverage and antibiotic resistances.

AIMS

Development of polysaccharide-conjugated pneumococcal vaccines, prompted by the ineffectiveness of the current 23-valent vaccine for young children, requires an understanding of the pneumococci causing invasive disease worldwide. We have reviewed the capsular serogroups and serotypes, and the antibiotic resistances of pneumococci identified from invasive disease in New Zealand, for the period 1987-94.

METHODS

Pneumococci referred from invasive disease were serogrouped and serotyped using the Neufeld test and allocated a capsular type according to the Danish system of nomenclature. Antibiotic susceptibility testing was performed by an agar dilution method following National Committee for Clinical Laboratory Standards (NCCLS) guidelines.

RESULTS

A total of 1506 pneumococci were examined of which, 584 (39.8%) were sourced from children less than 15 years and 573 (39%) were from adults 60 years or greater. The majority (88.3%) were from blood cultures. In descending order of frequency serogroups or serotypes 14, 19, 6, 9, 23, 7, 4 and 1 were common to all age-groups but serogroups 6 and 18 were significantly (p < 0.001) associated with children under 15 years and serotype 3 with adult patients. Penicillin resistance was demonstrated by 22 (1.4%) isolates, five of which showed high level resistance (MIC > or = 2 mg/L) and multidrug resistance. Fourteen percent of all isolates were resistant to at least one antibiotic and serogroups 23, 6, 18, 19 and serotype 14 accounted for 82.6% of these resistant isolates.

CONCLUSIONS

The serogroups and serotypes found most frequently associated with pneumococcal disease, and antibiotic resistance, were consistent with those described overseas. Continuing surveillance of antibiotic resistances and serotypes of pneumococci causing invasive disease is recommended.