Recent advances in otitis media.
ABSTRACT Otitis media (OM) is a pervasive illness in infants and children, and many children suffer multiple episodes during the first years of life. High rates of acute otitis media (AOM) are reported in developed and emerging countries. Early onset is common in both settings. Recurrent OM is associated with several factors, including early onset of disease, having a sibling with a history of AOM and absence of breast-feeding. Early onset disease has been hypothesized to result from Eustachian tube dysfunction, immunologic naivete and immaturity, and viral upper respiratory tract infection. Nasopharyngeal colonization with bacterial otopathogens increases the likelihood of AOM and the disease is most frequent in children with viral respiratory tract infection colonized with multiple otopathogens (Streptococcus pneumoniae, nontypeable Haemophilus influenzae [NTHi], Moraxella catarrhalis), potentially as a result of inflammation resulting from competition among the bacterial species within the nasopharynx. Epidemiologic observations and studies of pathogenesis suggest that successful strategies for reducing the burden of disease will be best accomplished by targeting multiple viral and/or bacterial pathogens and preventing early onset disease. Guidelines (2004) for the treatment of AOM in children establish a clear hierarchy among the various antibacterials for the treatment of this disease. Failure to achieve early bacterial eradication during antibiotic therapy for AOM increases the clinical failure rates in AOM in young children. Most recurrent AOM episodes occurring within 1 month after successful completion of antibiotic therapy are due to new otopathogens. Failure to eradicate middle ear and/or nasopharyngeal pathogens is associated with higher rates of clinical recurrent AOM, even when the patients show clinical improvement or cure at the end of therapy for the initial episode. Optimal strategy for the prevention of AOM recurrences requires sterilization of the middle ear and eradication of nasopharyngeal carriage of otopathogens during antimicrobial therapy.
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ABSTRACT: The Streptococcus pneumoniae pilus-1 is encoded by pilus islet 1 (PI-1), which has three clonal variants (clade I, II and III) and is present in about 30% of clinical pneumococcal isolates. In vitro and in vivo assays have demonstrated that pilus-1 is involved in attachment to epithelial cells and virulence, as well as protection in mouse models of infection. Several reports suggest that pilus-1 expression is tightly regulated and involves the interplay of numerous genetic regulators, including the PI-1 positive regulator RlrA. In this report we provide evidence that pilus expression, when analyzed at the single-cell level in PI-1 positive strains, is biphasic. In fact, the strains present two phenotypically different sub-populations of bacteria, one that expresses the pilus, while the other does not. The proportions of these two phenotypes are variable among the strains tested and are not influenced by genotype, serotype, growth conditions, colony morphology or by the presence of antibodies directed toward the pilus components. Two sub-populations, enriched in pilus expressing or not expressing bacteria were obtained by means of colony selection and immuno-detection methods for five strains. PI-1 sequencing in the two sub-populations revealed the absence of mutations, thus indicating that the biphasic expression observed is not due to a genetic modification within PI-1. Microarray expression profile and western blot analyses on whole bacterial lysates performed comparing the two enriched sub-populations, revealed that pilus expression is regulated at the transcriptional level (on/off regulation), and that there are no other genes, in addition to those encoded by PI-1, concurrently regulated across the strains tested. Finally, we provide evidence that the over-expression of the RrlA positive regulator is sufficient to induce pilus expression in pilus-1 negative bacteria. Overall, the data presented here suggest that the observed biphasic pilus expression phenotype could be an example of bistability in pneumococcus.PLoS ONE 01/2011; 6(6):e21269. · 4.09 Impact Factor
Article: Immunization with the RrgB321 fusion protein protects mice against both high and low pilus-expressing Streptococcus pneumoniae populations.[show abstract] [hide abstract]
ABSTRACT: RrgB321, a fusion protein of the three Streptococcus pneumoniae pilus-1 backbone RrgB variants, is protective in vivo against pilus islet 1 (PI-1) positive pneumococci. In addition, antibodies to RrgB321 mediate a complement-dependent opsonophagocytosis of PI-1 positive strains at levels comparable to those obtained with antisera against glycoconjugate vaccines. In the pneumococcus, pilus-1 displays a biphasic expression pattern, with different proportions of two bacterial phenotypes, one expressing and one not expressing the pilus-1. These two populations can be stably separated in vitro giving rise to the enriched high (H) and low (L) pilus expressing populations. In this work we demonstrate that: (i) the opsonophagocytic killing mediated in vitro by RrgB321 antisera is strictly dependent on the pilus expression ratio of the strain used; (ii) during the opsonophagocytosis assay pilus-expressing pneumococci are selectively killed, and (iii) no switch towards the pilus non-expressing phenotype can be observed. Furthermore, in sepsis and pneumonia models, mice immunized with RrgB321 are significantly protected against challenge with either the H or the L pilus-expressing population of strains representative of the three RrgB variants. This suggests that the pilus-1 expression is not down-regulated, and also that the expression of the pilus-1 could be up-regulated in vivo. In conclusion, these data provide evidence that RrgB321 is protective against PI-1 positive strains regardless of their pilus expression level, and support the rationale for the inclusion of this fusion protein into a multi-component protein-based pneumococcal vaccine.Vaccine 12/2011; 30(7):1349-56. · 3.77 Impact Factor