Occult pneumococcal bacteremia: a review.
ABSTRACT Occult bacteremia is primarily caused by Streptococcus pneumoniae and has been an intense clinical controversy in pediatric emergency medicine, with passionate opinions rendered from inside and outside the field. Vaccine development and widespread immunization have rapidly affected the changing epidemiology of this disease. There is a growing consensus that the reduction in incidence of occult bacteremia and the significant problem of antibiotic resistance are tipping the balance in favor of no testing and no treatment for well-appearing febrile children between 6 and 36 months of age who are immunized with Haemophilus influenzae B vaccination and PCV-7 (pneumococcal conjugate vaccine). This review of occult pneumococcal bacteremia will not only elaborate on current knowledge and clinical practice, but will also provide historical context to this fascinating phenomenon.
Article: Direct molecular typing of Bordetella pertussis from clinical specimens submitted for diagnostic quantitative (real-time) PCR.[show abstract] [hide abstract]
ABSTRACT: Molecular typing of Bordetella pertussis is routinely performed on bacterial isolates, but not on DNA extracted from nasopharyngeal aspirates or pernasal swabs submitted for diagnostic real-time PCR (qPCR). We investigated whether these DNA extracts were suitable for mulitlocus variable-number tandem repeat analysis (MLVA) and DNA sequence-based typing. We analysed all the available qPCR-positive samples received by our laboratory from patients <1 year of age between January 2008 and August 2010. Eighty one percent (106/131) of these generated a complete MLVA profile. This rose to 92 % (105/114) if only samples positive for both of the two targets used for the B. pertussis PCR (insertion element, IS481 and pertussis toxin promoter, ptxP) were analysed. Sequence-based typing of the pertactin, pertussis toxin S1 subunit and pertussis promoter regions (prn, ptxA and ptxP) was attempted on 89 of the DNA extracts that had generated a full MLVA profile. Eighty three (93 %) of these produced complete sequences for all three targets. Comparison of molecular typing data from the 89 extracts with those from 111 contemporary bacterial isolates showed that the two sources yielded the same picture of the B. pertussis population (dominated by the MLVA-27 prn(2) ptxA(1) ptxP(3) clonal type). There was no significant difference in MLVA type distribution or diversity between the two sample sets. This suggests that clinical extracts can be used in the place of, or to complement, bacterial cultures for typing purposes (at least, in this age group). With small modifications to methodology, generating MLVA and sequence-based typing data from qPCR-positive clinical DNA extracts is likely to generate a complete data set in the majority of samples from the <1 year age-group. Its success with samples from older subjects remains to be seen. However, our data suggest that it is suitable for inclusion in molecular epidemiological studies of the B. pertussis population or as a tool in outbreak investigations.Journal of Medical Microbiology 08/2012; · 2.50 Impact Factor
Article: Prevalence of Streptococcus pneumoniae serotypes causing invasive and non-invasive disease in South East Asia: a review.[show abstract] [hide abstract]
ABSTRACT: Streptococcus pneumoniae is a major cause of bacterial infections resulting in significant morbidity and mortality worldwide. Currently, up to 13 serotypes are included in pneumococcal conjugate vaccines (PCVs). However, the serotype formulation of these vaccines was initially designed to protect children against serotypes most commonly causing invasive disease in North America, and may not reflect the serotype distribution across the world. Data regarding pneumococcal epidemiology from the other parts of the world, in particular South East Asia, has not been reviewed. This systematic literature review analyses published serotype data regarding S. pneumoniae isolates from South East Asian countries (defined as countries belonging to the Association of South East Asian Nations, ASEAN): Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, Philippines, Singapore, Thailand and Vietnam up to 3rd of March 2012. Analysis of data from six ASEAN countries, from which information on pneumococcal serotypes was available, showed that the most common disease causing serotypes (in rank order) were 19F, 23F, 14, 6B, 1, 19A and 3. Serotype distribution of pneumococcal isolates was similar across the ASEAN region. Serotype level data was more commonly reported for pneumococcal isolates causing invasive pneumococcal disease than for those from non-invasive disease. Studies from Malaysia, Thailand and Singapore contributed the largest proportion of pneumococcal isolates, and serotype data, when compared to other ASEAN countries. This review demonstrates that the majority of IPD causing serotypes in SE Asia are included in currently licensed PCVs. However, PCV's are included in the routine childhood immunisation schedule of only one of the ten countries included in this analysis. Our findings demonstrate the scarcity of information available on serotype prevalence and distribution of pneumococci in SE Asia.Vaccine 04/2012; 30(24):3503-14. · 3.77 Impact Factor