Cees M. Verduin

Moraxella catarrhalis: from Emerging to Established Pathogen

SUMMARY Moraxella catarrhalis (formerly known as Branhamella catarrhalis) has emerged as a significant bacterial pathogen of humans over the past two decades. During this period, microbiological and molecular diagnostic techniques have been developed and improved for M. catarrhalis, allowing the adequate determination and taxonomic positioning of this pathogen. Over the same period, studies have revealed its involvement in respiratory (e.g., sinusitis, otitis media, bronchitis, and pneumonia) and ocular infections in children and in laryngitis, bronchitis, and pneumonia in adults. The development of (molecular) epidemiological tools has enabled the national and international distribution of M. catarrhalis strains to be established, and has allowed the monitoring of nosocomial infections and the dynamics of carriage. Indeed, such monitoring has revealed an increasing number of Β-lactamase-positive M. catarrhalis isolates (now well above 90%), underscoring the pathogenic potential of this organism. Although a number of putative M. catarrhalis virulence factors have been identified and described in detail, their relationship to actual bacterial adhesion, invasion, complement resistance, etc. (and ultimately their role in infection and immunity), has been established in a only few cases. In the past 10 years, various animal models for the study of M. catarrhalis pathogenicity have been described, although not all of these models are equally suitable for the study of human infection. Techniques involving the molecular manipulation of M. catarrhalis genes and antigens are also advancing our knowledge of the host response to and pathogenesis of this bacterial species in humans, as well as providing insights into possible vaccine candidates. This review aims to outline our current knowledge of M. catarrhalis, an organism that has evolved from an emerging to a well-established human pathogen.

Severity of nonbullous Staphylococcus aureus impetigo in children is associated with strains harboring genetic markers for exfoliative toxin B panton-valentine leukocidin, and the multidrug resistance plasmid pSK41

ABSTRACT Nonbullous impetigo is a common skin infection in children and is frequently caused by Staphylococcus aureus. Staphylococcal toxins and especially exfoliative toxin A are known mediators of bullous impetigo in children. It is not known whether this is also true for nonbullous impetigo. We set out to analyze clonality among clinical isolates of S. aureus from children with nonbullous impetigo living in a restricted geographical area in The Netherlands. We investigated whether staphylococcal nasal carriage and the nature of the staphylococcal strains were associated with the severity and course of impetigo. Bacterial isolates were obtained from the noses and wounds of children suffering from impetigo. Strains were genetically characterized by pulsed-field gel electrophoresis-mediated typing and binary typing, which was also used to assess toxin gene content. In addition, a detailed clinical questionnaire was filled in by each of the participating patients. Staphylococcal nasal carriage seems to predispose the patients to the development of impetigo, and 34% of infections diagnosed in the Rotterdam area are caused by one clonal type of S. aureus. The S. aureus strains harbor the exfoliative toxin B (ETB) gene as a specific virulence factor. In particular, the numbers (P = 0.002) and sizes (P < 0.001) of the lesions were increased in patients infected with an ETB-positive strain. Additional predictors of disease severity and development could be identified. The presence of a staphylococcal plasmid encoding multiple antibiotic resistance traits, as detected by binary typing, was associated with a reduction in the cure rate. Our results recognize that a combination of staphylococcal virulence and resistance genes rather than a single gene determines the development and course of nonbullous impetigo. The identification of these microbial genetic markers, which are predictive of the severity and the course of the disease, will facilitate guided individualized antimicrobial therapy in the future.

Pneumococcal vaccination does not affect the genetic diversity of Moraxella catarrhalis isolates in children

Moraxella catarrhalis is an acknowledged pathogen of the respiratory tract in both adults and children [1], occupying a similar niche to that of Streptococcus pneumoniae and Haemophilus influenzae. In a recent study, Veenhoven et al. [2] showed that toddlers and older children who had previously experienced episodes of acute otitis media (AOM) did not experience a reduction of AOM episodes when vaccinated with a conjugate pneumococcal vaccine followed by a polysaccharide pneumococcal vaccine. Moreover, the incidence of M. catarrhalis isolation did not differ between the two groups, while Staphylococcus aureus was isolated more often from children in the vaccinated group than from children in the control group vaccinated against hepatitis A or B (P=0.02). It was also noted that an “immediate and complete” replacement of S. pneumoniae vaccine serotypes by non-vaccine serotypes tended to occur within the vaccinated group. Since bacterial interference of M. catarrhalis by competing streptococcal species has been demonstrated in vitro [3], the present study was conducted to determine whether vaccination against S. pneumoniae (and its subsequent removal from the M. catarrhalis niche) had an effect in altering the genetic diversity of M. catarrhalis isolates compared to a control vaccinated group. During the course of the study, children were followed for a total of 18 months, with routine microbiological and clinical investigations occurring at 1, 7, 14, 20 and 26 months after vaccination as well as during any episode of AOM. Bacterial cultures were obtained from nasopharyngeal swabs collected at routine visits as well as from middle ear fluids during episodes of AOM. In total, 41 M. catarrhalis isolates obtained from 13 children vaccinated with pneumococcal vaccine and 21 M. catarrhalis isolates obtained from six children vaccinated with a control (hepatitis A or B) vaccine were genotyped using pulsedfield gel electrophoresis (PFGE) as described by Verduin et al. [4]. The results of PFGE analysis are presented as a dendrogram in Fig. 1. As an indication of pathogenic potential, all isolates were also tested for the phenotypic expression of complement resistance using the “culture and spot” test [5]. PFGE analysis of the isolates indicated the presence of four clusters comprising a wide range of genotypes. The high degree of diversity within the M. catarrhalis species has already been documented in several publications [6, 7]. No pattern could be observed between PFGE cluster and vaccination status, or PFGE cluster and the isolation of other (co-colonizing) bacteria. M. catarrhalis PFGE types belonging to different clusters were found to occur within the same patient overtime (e.g. patient 1001), an observation that also held true for PFGE types associated with episodes of AOM (e.g. patient 4025). The vast majority of isolates (56/62) were found to be resistant to the effect of complement in human serum, and there was no difference between the isolation of complement-resistant and complement-sensitive phenotypes between the two vaccinated groups (Fisher’s exact test, P=1). The percentage of complement-resistant M. catarrhalis strains isolated appears to be relatively high compared to some studies involving healthy children (90% vs 30–60% [8], respectively), though other studies have yielded results similar to ours [9]. The percentage of complementresistant isolates could have been influenced by the fact that the children enrolled in the study had previously experienced episodes of AOM disease, possibly resulting in an enhanced immune response (including complementmediated responses) against potential bacterial pathogens. J. P. Hays (*) . K. Eadie . C. M. Verduin . H. Verbrugh . A. van Belkum Department of Medical Microbiology and Infectious Diseases, Erasmus University Medical Center Rotterdam (EMCR), Dr Molewaterplein 40, 3015 GD Rotterdam, The Netherlands e-mail: j.hays@erasmusmc.nl Tel.: +31-10-4633668 Fax: +31-10-4633875

Fusidinezuurcrème ter behandeling van impetigo: een dubbelblind gerandomiseerd placebogecontroleerd onderzoek

Doel Impetigo is de meest voorkomende huidinfectie bij kinderen. Wij toetsten de hypothese dat fusidinezuur het behandeleffect van alleen desinfectie met povidonjood niet verbetert. Opzet Gerandomiseerd placebogecontroleerd onderzoek. Alle kinderen werden behandeld met povidonjoodshampoo en gerandomiseerd naar behandeling met fusidinezuurcreme of met placebocreme. Setting Huisartspraktijken in de regio Rotterdam. Deelnemers Honderdvierentachtig kinderen van nul tot twaalf jaar met impetigo werden aangemeld door hun huisarts en bezocht door een onderzoeksverpleegkundige. Honderdzestig kinderen werden gerandomiseerd. Beoordeling vond plaats na een, twee en vier weken. Primaire uitkomsten Klinische en bacteriele genezing na een week. Resultaten Na een week behandeling waren 55% van de kinderen in de fusidinezuurgroep klinisch genezen tegenover 13% in de placebogroep (odds-ratio 12,6; 95%-BI 5,0-31,5; NNT 2,3). Na twee en vier weken waren de verschillen in genezing tussen beide groepen kleiner. In de placebogroep waren meer kinderen therapieontrouw en kregen meer kinderen alsnog een antibioticum voorgeschreven. De placebogroep rapporteerde meer bijwerkingen. In 96% van de positieve kweken werdS. aureus aangetroffen. Geen van de stammen was resistent voor fusidinezuur. Conclusies Fusidinezuur bleek veel effectiever dan placebo in de behandeling van impetigo. De waarde van povidonjood is twijfelachtig.