Group B streptococcal carriage, serotype distribution and antibiotic susceptibilities in pregnant women at the time of delivery in a refugee population on the Thai-Myanmar border

<p>Abstract</p> <p>Background</p> <p>Group B Streptococcus (GBS) is the leading cause of neonatal sepsis in the developed world. Little is known about its epidemiology in the developing world, where the majority of deaths from neonatal infections occur. Maternal carriage of GBS is a prerequisite for the development of early onset GBS neonatal sepsis but there is a paucity of carriage data published from the developing world, in particular South East Asia.</p> <p>Methods</p> <p>We undertook a cross sectional study over a 13 month period in a remote South East Asian setting on the Thai-Myanmar border. During labour, 549 mothers had a combined vaginal rectal swab taken for GBS culture. All swabs underwent both conventional culture as well as PCR for GBS detection. Cultured GBS isolates were serotyped by latex agglutination, those that were negative or had a weak positive reaction and those that were PCR positive but culture negative were additionally tested using multiplex PCR based on the detection of GBS capsular polysaccharide genes.</p> <p>Results</p> <p>The GBS carriage rate was 12.0% (95% CI: 9.4-15.0), with 8.6% positive by both culture and PCR and an additional 3.5% positive by PCR alone. Serotypes, Ia, Ib, II, III, IV, V, VI and VII were identified, with II the predominant serotype. All GBS isolates were susceptible to penicillin, ceftriaxone and vancomycin and 43/47 (91.5%) were susceptible to erythromycin and clindamycin.</p> <p>Conclusions</p> <p>GBS carriage is not uncommon in pregnant women living on the Thai-Myanmar border with a large range of serotypes represented.</p

Developmental roadmap for antimicrobial susceptibility testing systems

Antimicrobial susceptibility testing (AST) technologies help to accelerate the initiation of targeted antimicrobial therapy for patients with infections and could potentially extend the lifespan of current narrow-spectrum antimicrobials. Although conceptually new and rapid AST technologies have been described, including new phenotyping methods, digital imaging and genomic approaches, there is no single major, or broadly accepted, technological breakthrough that leads the field of rapid AST platform development. This might be owing to several barriers that prevent the timely development and implementation of novel and rapid AST platforms in health-care settings. In this Consensus Statement, we explore such barriers, which include the utility of new methods, the complex process of validating new technology against reference methods beyond the proof-of-concept phase, the legal and regulatory landscapes, costs, the uptake of new tools, reagent stability, optimization of target product profiles, difficulties conducting clinical trials and issues relating to quality and quality control, and present possible solutions

Evaluation of a novel real-time PCR test based on the ssrA gene for the identification of group B streptococci in vaginal swabs

<p>Abstract</p> <p>Background</p> <p>Despite the implementation of prevention guidelines, early-onset group B streptococci (GBS) disease remains a cause of neonatal morbidity and mortality worldwide. Strategies to identify women who are at risk of transmitting GBS to their infant and the administration of intrapartum antibiotics have greatly reduced the incidence of neonatal GBS disease. However, there is a requirement for a rapid diagnostic test for GBS that can be carried out in a labour ward setting especially for women whose GBS colonisation status is unknown at the time of delivery. We report the design and evaluation of a real-time PCR test (<it>RiboSEQ </it>GBS test) for the identification of GBS in vaginal swabs from pregnant women.</p> <p>Methods</p> <p>The qualitative real-time PCR <it>RiboSEQ </it>GBS test was designed based on the bacterial <it>ssrA </it>gene and incorporates a competitive internal standard control. The analytical sensitivity of the test was established using crude lysate extracted from serial dilutions of overnight GBS culture using the IDI Lysis kit. Specificity studies were performed using DNA prepared from a panel of GBS strains, related streptococci and other species found in the genital tract environment. The <it>RiboSEQ </it>GBS test was evaluated on 159 vaginal swabs from pregnant women and compared with the GeneOhm™ StrepB Assay and culture for the identification of GBS.</p> <p>Results</p> <p>The <it>RiboSEQ </it>GBS test is specific and has an analytical sensitivity of 1-10 cell equivalents. The <it>RiboSEQ </it>GBS test was 96.4% sensitive and 95.8% specific compared to "gold standard" culture for the identification of GBS in vaginal swabs from pregnant women. In this study, the <it>RiboSEQ </it>GBS test performed slightly better than the commercial BD GeneOhm™ StrepB Assay which gave a sensitivity of 94.6% and a specificity of 89.6% compared to culture.</p> <p>Conclusion</p> <p>The <it>RiboSEQ </it>GBS test is a valuable method for the rapid, sensitive and specific detection of GBS in pregnant women. This study also validates the <it>ssrA </it>gene as a suitable and versatile target for nucleic acid-based diagnostic tests for bacterial pathogens.</p

Allelic replacement of the streptococcal cysteine protease SpeB in a Δsrv mutant background restores biofilm formation

<p>Abstract</p> <p>Background</p> <p>Group A <it>Streptococcus </it>(GAS) is a Gram-positive human pathogen that is capable of causing a wide spectrum of human disease. Thus, the organism has evolved to colonize a number of physiologically distinct host sites. One such mechanism to aid colonization is the formation of a biofilm. We have recently shown that inactivation of the streptococcal regulator of virulence (Srv), results in a mutant strain exhibiting a significant reduction in biofilm formation. Unlike the parental strain (MGAS5005), the streptococcal cysteine protease (SpeB) is constitutively produced by the <it>srv </it>mutant (MGAS5005Δ<it>srv</it>) suggesting Srv contributes to the control of SpeB production. Given that SpeB is a potent protease, we hypothesized that the biofilm deficient phenotype of the <it>srv </it>mutant was due to the constitutive production of SpeB. In support of this hypothesis, we have previously demonstrated that treating cultures with E64, a commercially available chemical inhibitor of cysteine proteases, restored the ability of MGAS5005Δ<it>srv </it>to form biofilms. Still, it was unclear if the loss of biofilm formation by MGAS5005Δ<it>srv </it>was due only to the constitutive production of SpeB or to other changes inherent in the <it>srv </it>mutant strain. To address this question, we constructed a Δ<it>srv</it>Δ<it>speB </it>double mutant through allelic replacement (MGAS5005Δ<it>srv</it>Δ<it>speB</it>) and tested its ability to form biofilms <it>in vitro</it>.</p> <p>Findings</p> <p>Allelic replacement of <it>speB </it>in the <it>srv </it>mutant background restored the ability of this strain to form biofilms under static and continuous flow conditions. Furthermore, addition of purified SpeB to actively growing wild-type cultures significantly inhibited biofilm formation.</p> <p>Conclusions</p> <p>The constitutive production of SpeB by the <it>srv </it>mutant strain is responsible for the significant reduction of biofilm formation previously observed. The double mutant supports a model by which Srv contributes to biofilm formation and/or dispersal through regulation of <it>speB</it>/SpeB.</p

Acetyl-11-keto-β-boswellic acid (AKBA); targeting oral cavity pathogens

<p>Abstract</p> <p>Background</p> <p>Boswellic acids mixture of triterpenic acids obtained from the oleo gum resin of <it>Boswellia serrata </it>and known for its effectiveness in the treatment of chronic inflammatory disease including peritumor edema. Boswellic acids have been extensively studied for a number of activities including anti inflammatory, antitumor, immunomodulatory, and inflammatory bowel diseases. The present study describes the antimicrobial activities of boswellic acid molecules against oral cavity pathogens. Acetyl-11-keto-β-boswellic acid (AKBA), which exhibited the most potent antibacterial activity, was further evaluated in time kill studies, mutation prevention frequency, postantibiotic effect (PAE) and biofilm susceptibility assay against oral cavity pathogens.</p> <p>Findings</p> <p>AKBA exhibited an inhibitory effect on all the oral cavity pathogens tested (MIC of 2-4 μg/ml). It exhibited concentration dependent killing of S<it>treptococcus mutans </it>ATCC 25175 up to 8 × MIC and also prevented the emergence of mutants of <it>S.mutans </it>ATCC 25175 at 8× MIC. AKBA demonstrated postantibiotic effect (PAE) of 5.7 ± 0.1 h at 2 × MIC. Furthermore, AKBA inhibited the formation of biofilms generated by <it>S.mutans </it>and <it>Actinomyces viscosus </it>and also reduced the preformed biofilms by these bacteria.</p> <p>Conclusions</p> <p>AKBA can be useful compound for the development of antibacterial agent against oral pathogens and it has great potential for use in mouthwash for preventing and treating oral infections.</p

Comparison of the virulence of exopolysaccharide-producing Prevotella intermedia to exopolysaccharide non-producing periodontopathic organisms

<p>Abstract</p> <p>Background</p> <p>Evidence in the literature suggests that exopolysaccharides (EPS) produced by bacterial cells are essential for the expression of virulence in these organisms. Secreted EPSs form the framework in which microbial biofilms are built.</p> <p>Methods</p> <p>This study evaluates the role of EPS in <it>Prevotella intermedia </it>for the expression of virulence. This evaluation was accomplished by comparing EPS-producing <it>P. intermedia </it>strains 17 and OD1-16 with non-producing <it>P. intermedia </it>ATCC 25611 and <it>Porphyromonas gingivalis </it>strains ATCC 33277, 381 and W83 for their ability to induce abscess formation in mice and evade phagocytosis.</p> <p>Results</p> <p>EPS-producing <it>P. intermedia </it>strains 17 and OD1-16 induced highly noticeable abscess lesions in mice at 10⁷colony-forming units (CFU). In comparison, <it>P. intermedia </it>ATCC 25611 and <it>P. gingivalis </it>ATCC 33277, 381 and W83, which all lacked the ability to produce viscous materials, required 100-fold more bacteria (10⁹CFU) in order to induce detectable abscess lesions in mice. Regarding antiphagocytic activity, <it>P. intermedia </it>strains 17 and OD1-16 were rarely internalized by human polymorphonuclear leukocytes, but other strains were readily engulfed and detected in the phagosomes of these phagocytes.</p> <p>Conclusions</p> <p>These results demonstrate that the production of EPS by <it>P. intermedia </it>strains 17 and OD1-16 could contribute to the pathogenicity of this organism by conferring their ability to evade the host's innate defence response.</p

Development of Bacterial Biofilms on Artificial Corals in Comparison to Surface-Associated Microbes of Hard Corals

Numerous studies have demonstrated the differences in bacterial communities associated with corals versus those in their surrounding environment. However, these environmental samples often represent vastly different microbial micro-environments with few studies having looked at the settlement and growth of bacteria on surfaces similar to corals. As a result, it is difficult to determine which bacteria are associated specifically with coral tissue surfaces. In this study, early stages of passive settlement from the water column to artificial coral surfaces (formation of a biofilm) were assessed. Changes in bacterial diversity (16S rRNA gene), were studied on artificially created resin nubbins that were modelled from the skeleton of the reef building coral Acropora muricata. These models were dip-coated in sterile agar, mounted in situ on the reef and followed over time to monitor bacterial community succession. The bacterial community forming the biofilms remained significantly different (R = 0.864 p<0.05) from that of the water column and from the surface mucus layer (SML) of the coral at all times from 30 min to 96 h. The water column was dominated by members of the α-proteobacteria, the developed community on the biofilms dominated by γ-proteobacteria, whereas that within the SML was composed of a more diverse array of groups. Bacterial communities present within the SML do not appear to arise from passive settlement from the water column, but instead appear to have become established through a selection process. This selection process was shown to be dependent on some aspects of the physico-chemical structure of the settlement surface, since agar-coated slides showed distinct communities to coral-shaped surfaces. However, no significant differences were found between different surface coatings, including plain agar and agar enhanced with coral mucus exudates. Therefore future work should consider physico-chemical surface properties as factors governing change in microbial diversity