Penicillin resistance in serogroups/serotypes of Streptococcus pneumoniae causing invasive infections in Central Saudi Arabia

OBJECTIVE: To determine the minimum inhibitory concentrations (MICs) of penicillin, ceftriaxone and vancomycin of serogroups/serotypes of Streptococcus pneumoniae (S. pneumoniae) from invasive diseases in all age groups from major hospitals in Riyadh, Kingdom of Saudi Arabia (KSA).

METHODS: All isolates of S. pneumoniae from patients with invasive pneumococcal infections between February 2000 and November 2001 were prospectively collected from 8 major hospitals in Riyadh, KSA. The isolates were confirmed as S. pneumoniae at the King Khalid University Hospitals, Riyadh, KSA and then serogrouped/serotyped using the agglutination method. The MICs for penicillin, ceftriaxone and vancomycin were carried out using the E-test.

RESULTS: Forty-three percent of the isolates were resistant to penicillin mostly of the intermediate type (97%). The resistant strains were mainly confined to serogroups/serotypes 6, 23, 19 and 15 and the 7-valent conjugate vaccine covers 76% of the penicillin-resistant strains. Only one isolate was resistant to ceftriaxone.

CONCLUSION: In view of the rather insignificant level of highly resistant-penicillin strains and the virtual absence of resistance to ceftriaxone we would like to suggest using ceftriaxone for treating invasive pneumococcal infections outside the central nervous system. We recommend that the conjugate vaccine would be a useful adjunct to penicillin prophylaxis in patients at risk in our community.