Impact of pneumococcal conjugate vaccine and the severity of winter influenza-like illnesses on invasive pneumococcal infections in children and adults.

BACKGROUND: Pneumococcal conjugate vaccine (PCV7), recommended in July 2000 for routine use in infants, has resulted in a reduction in the rate of invasive pneumococcal disease (IPD) in young children. We studied the impact of PCV7 and the possible contribution of the severity of influenza-like respiratory infection season on the rate of IPD on children and adults. METHODS: In 7 hospitals of a health system, episodes of IPD were identified by the microbiology laboratories during the 2-year period before July 2000 and the 4-year period after July 2000 during routine use of PCV7, and patient records were reviewed. Episodes of influenza-like illnesses during each winter in a local county were prospectively measured by reports from all acute care hospitals and episodes of absenteeism resulting from influenza-like illnesses from all schools. RESULTS: There were 720 patients with blood and/or cerebrospinal fluid isolates of Streptococcus pneumoniae. There were significant reductions in cases of IPD in children younger than 2 years, 68% reduction; children 2-4 years of age, 70%; adults 18-49 years of age, 42%; and adults older than 64 years, 30%. Annually, during the PCV7 period, there were significantly fewer episodes of influenza-like illnesses than during the pre-PCV7 years. CONCLUSIONS: PCV7 efficacy and resultant herd-type immunity resulted in a reduction in the rate of IPD not only in young children but also in young and elderly adults. Milder winter respiratory viral seasons may possibly have contributed to the observed reduction in the rate of IPD.

Use of incubation time to detection in BACTEC 9240 to distinguish coagulase-negative staphylococcal contamination from infection in pediatric blood cultures.

BACKGROUND: Growth of coagulase-negative staphylococci (CoNS) in a blood culture indicates infection or contamination. Differentiation may be difficult in pediatric patients from whom only a single blood culture is commonly obtained. METHODS: We evaluated the use of the incubation time to detection of growth [time to positive (TTP)] of CoNS in a continuously monitored blood culture system (BACTEC Peds/F bottles in BACTEC 9240) to differentiate infection from contamination. Three groups of febrile pediatric patients with blood cultures growing CoNS were identified: Group 1, children with vascular catheter-associated bloodstream infection; Group 2, previously healthy children with a contaminant; Group 3, chronically ill children with a contaminant. RESULTS: The median TTP for blood cultures from the 17 infection episodes, 11 h [mean, 13.2 h; 95% confidence interval (CI), 11.4 to 17.7], was significantly shorter than either the 30 episodes in the previously healthy group with contaminant, median 19 h (mean, 22.7 h; 95% CI 19.5 to 26.2; P < 0.0001) or the 12 episodes in the chronically ill group with contaminant, median 24 h (mean, 35.2 h; 95% CI 17.2 to 53.1; P < 0.0001). A TTP of < or =15 h had a positive predictive value of 84% for diagnosis of infection. A TTP of > or =22 h had a positive predictive value of 87% for diagnosis of contaminant. CONCLUSION: In our experience the TTP was a useful adjunctive test to determine the clinical significance of isolation of CoNS from a blood culture from a pediatric patient.