002) ( Table 3). In the control group, among the 20 pneumococcal isolates recovered from multiple carriers during

May 2001, four serotypes were identified, of which VT serotypes (6B, 19F, and 23F) represented 95% of the isolates ( Table 3). In June 2001, two serotypes were identified among the 10 pneumococcal isolates, with VT serotypes increasing from 95 to 100%, while NVT isolates decreased from 5 to 0% (P = 1) ( Table 3). Among the vaccinated group, in May 2001, co-colonization with VT isolates was detected in five out of seven multiple carriers, of which four presented the VT as the dominant serotype. In June 2001, co-colonization with VT isolates was detected selleckchem in four out of six multiple carriers, with the VT being identified always as a minor serotype (Fig. 1, children A to K). Regarding the control, in May 2001, co-colonization with VT isolates was detected in two children who presented

selleck chemical VTs as the dominant serotypes. In June 2001, co-colonization was detected only once and two VT serotypes were found in association (23F—dominant serotype; 19F—minor serotype) (Fig. 1, children L and M). Serotype 6A was the most common serotype found among multiple carriers—it was found co-colonizing with 19F (three occasions), 6B (two occasions), and 14, 19A and non-typeable isolates (one occasion). Overall we compared 174 PFGE profiles of representative isolates of each of the serotypes found among the vaccinated (124 isolates) and control (50 isolates) groups and no capsular switch phenomenon was detected. In the group where the vaccine pressure was present, no vaccine escapee recombinant isolate was observed and the NVT PFGE profiles were found to differ from the preceding VT serotypes. A few examples of the PFGE profiles analyzed are shown in Fig. 2. By observing the colonization pattern change from May to June 2001 among children of the vaccinated and control groups, we were able to assess the number of isolates that were cleared, de novo acquired, unmasked or maintained

( Fig. 3). Bearing in mind that PCV7 targets directly VT and indirectly NVT isolates, the effect of the vaccine on pneumococcal carriage was Dichloromethane dehalogenase explored based on three potential mechanisms: prevention of VT de novo acquisition, enhancement of VT clearance, and enhancement of NVT unmasking. We compared these three mechanisms capable of affecting pneumococcal colonization between vaccinated and control groups to identify those that could explain the vaccine’s effect. Serotype clearance was similar between VT and NVT isolates among the vaccinated and control groups (P = 0.635). VT and NVT isolates were equally probable to be cleared in both groups (OR, 1.12; 95% confidence interval (CI), 0.68–1.84) ( Table 4).