Carriage of penicillin-resistant Pneumococci in a military population in Washington, DC: Risk factors and correlation with clinical isolates

To assess the carriage of penicillin-resistant pneumococci (PRP) in our local (military) population, we retrospectively reviewed our laboratory isolates from the period of January 1990 through May 1994 and prospectively obtained nasopharyngeal culture specimens from 179 children during January through May 1994. The incidence of PRP increased from 0% of pneumococcal isolates in 1990 to 36.2% by 1994. Fifty-two of 179 subjects (29%) were carriers of S. pneumonia, and 25 (48%) of them carried PRP; 11 (21.7%) of these isolates were highly resistant to penicillin (MIC, >1.0 mu g/ mL), and 14 (26.9%) were intermediately resistant (MIC, 0.1-1.0 mu g/mL). Exposure to a health care worker was correlated with pneumococcal carriage (P < .007). Frequent courses of antimicrobial treatment correlated both with carriage of pneumococci (P < .009) and with carriage of PRP (P < .0001). In contrast, antimicrobial prophylaxis was protective against carriage of pneumococci (P < .002). We conclude that there is a high proportion of PRP among carriers of pneumococci in our community, as corroborated by the rise in laboratory isolations of PRP. Children who have had frequent antimicrobial courses are at particular risk.