Control of Streptococcus pneumoniae serotype 5 epidemic of severe pneumonia among young army recruits by mass antibiotic treatment and vaccination

Abstract

During an outbreak of severe pneumonia among new army recruits, an epidemiological investigation combined with repeated nasopharyngeal/oropharyngeal cultures from sick and healthy contacts subjects was conducted. Fifteen pneumonia cases and 19 influenza-like illness cases occurred among 596 recruits over a 4-week period in December 2005. Pneumonia attack rates reached up to 5.5%. A single pneumococcus serotype 5 clone was isolated from blood or sputum cultures in 4 patients and 30/124 (24.1%) contacts. Immunization with 23-valent polysaccharide vaccine supplemented with a 2-dose azithromycin mass treatment rapidly terminated the outbreak. Carriage rates dropped to <1%, 24 and 45 days after intervention.

Fig. 1

Pneumonia (black bars) and influenza-like illness (white bars) cases by date of fever onset (marked as ‘outbreak days’) (pneumonia follow-up was maintained until outbreak day 47. ILI follow-up was halted on outbreak day 37). a: First recorded ILI case (outbreak day 1); b: general practitioner alert of suspected outbreak (outbreak day 12); c: S. pneumoniae mass sampling among control recruits in the base (outbreak day 17); d: recruits sent home (outbreak day 19); e: antibiotic prophylaxis (first dose) and mass vaccination (outbreak day 23); f: recruits return to base, second dose of antibiotic prophylaxis administered (outbreak day 30); g: first follow-up cultures (outbreak day 47); h: second follow-up cultures (outbreak day 68).

Fig. 2

PFGE patterns generated by SmaI digestion of S. pneumoniae serotype 5 isolates recovered from military recruits. Lane 1 contains a lambda ladder; lane 2 contains a reference strain R6 used as a molecular weight marker; lane 3 contains the Columbia⁵-19 international clone. Numbers on the left show molecular weight sizes in kilobases. Lanes 4–34 contain nasopharyngeal isolates; lanes 35–36 contain oropharyngeal isolates; lanes 37–38 contain blood isolates; lanes 39–40 contains respiratory secretion isolate.

Fig. 3

PFGE patterns generated by SmaI digestion of S. pneumoniae serotype 5 isolates recovered from children in Southern Israel during 2004–2006. Lanes 1 and 28 contain a lambda ladder; lanes 2 and 27 contain a reference strain R6 used as a molecular weight marker. Numbers on the left show molecular weight sizes in kilobases. Lanes 3–11 contain nasopharyngeal isolates; lanes 12–20 contain isolates recovered from middle ear fluids; lanes 21–26 contain blood isolates.