Disease burden due to Streptococcus dysgalactiae subsp equisimilis (group G and C streptococcus) is higher than that due to Streptococcus pyogenes among Mumbai school children

Streptococcus pyogenes [group A streptococcus (GAS)], a human pathogen, and Streptococcus dysgalactiae subsp. equisimilis [human group G and C streptococcus (GGS/GCS)] are evolutionarily related, share the same tissue niche in humans, exchange genetic material, share up to half of their virulence-associated genes and cause a similar spectrum of diseases. Yet, GGS/GCS is often considered as a commensal bacterium and its role in streptococcal disease burden is under-recognized. While reports of the recovery of GGS/GCS from normally sterile sites are increasing, studies describing GGS/GCS throat colonization rates relative to GAS in the same population are very few. This study was carried out in India where the burden of streptococcal diseases, including rheumatic fever and rheumatic heart disease, is high. As part of a surveillance study, throat swabs were taken from 1504 children attending 7 municipal schools in Mumbai, India, during 2006-2008. GAS and GGS/GCS were identified on the basis of beta-haemolytic activity, carbohydrate group and PYR test, and were subsequently typed. The GGS/GCS carriage rate (1166/1504, 11%) was eightfold higher than the GAS carriage (22/1504, 1.5%) rate in this population. The 166 GGS/GCS isolates collected represented 21 different emm types (molecular types), and the 22 GAS isolates represented 15 different emm types. Although the rate of pharyngitis associated with GGS/GCS is marginally lower than with GAS, high rates of throat colonization by GGS/GCS underscore its importance in the pathogenesis of pharyngitis.

Metallo beta lactamase producing Pseudomonas aeruginosa and Acinetobacter baumannii

This study aims in identifying MBLs particularly Zn requiring Molecular Class B enzymes produced by Pseudomonas aeruginosa and Acinetobacter baumannii. The resistance by these organisms are in a rise against all antibiotics including carbapenems and no prescribed CLSI guidelines is available for detecting them. Clinical isolates antibiotic susceptibility was determined by number of phenotypic tests by addition of 50mM of 10 mu l zinc as cofactor for metallo beta lactamase production along with 0.5M ETDA of 5 mu l (930 mu g per disk) plain disks. Increase in zone size of the meropenem -EDTA disk compared to the meropenem disk without EDTA was recorded positive. For Zn requiring MBLs zone towards both disks of EDTA and Zn along with meropenem is detected by DDST.

Bordetella pertussis from functional genomics to intranasal vaccination.

Whooping cough still represents a major health problem, despite the use of effective vaccines for several decades. Being classically a typical childhood disease, whooping cough in young adults is now more common than it used to be, suggesting that protection after vaccination wanes during adolescence. As an alternative to the current vaccines, we wish to develop live attenuated vaccines to be delivered by the nasal route, such as to mimic the natural route of infection and to induce long lasting immunity. Bordetella pertussis, the etiological agent of whooping cough, produces a number of virulence factors, including toxins. Its recently determined genome sequence makes it now possible to apply functional genomics, such as transcriptomics and systematic knock-out mutagenesis. The expression of most known B. pertussis virulence genes is controlled by the two-component system BvgA/S. DNA microarray analyses have led to the identification of novel genes in the BvgA/S regulon, some of which are activated by BvgA/S and others are repressed by BvgA/S. In addition, some genes appear to be differentially modulated by nicotinic acid and MgSO4, both known to modulate the expression of BvgA/S-regulated genes. Among others, the functional genomics approach has uncovered two strongly BvgA/S-activated genes, named hotA and hotB (for 'homolog of toxin'), the products of which show high sequence similarities to pertussis toxin subunits. The identification of the full array of virulence factors, as well as an integrated understanding of the bacterial physiology should allow us to design attenuated B. pertussis strains useful for intranasal vaccination. A first generation of attenuated strains has already shown full protection in mice after a single intranasal administration. Such strains may also serve as vaccine carriers for heterologous antigens, in order to vaccinate against several different pathogens simultaneously.

Detection of Staphylococcus aureus by 16S rRNA directed in situ hybridisation in a patient with a brain abscess caused by small colony variants.

Kipp F, Ziebuhr W, Becker K, Krimmer V, Höbeta N, Peters G, Von Eiff C. Institute of Medical Microbiology, Hospital and Clinics, University of Münster, Germany. A 45 year old man was admitted to hospital with a right sided facial paralysis and three month history of seizures. Computed tomography showed a left temporal mass including both intracerebral and extracerebral structures. Ten years earlier the patient had undergone a neurosurgical intervention in the same anatomical region to treat a subarachnoid haemorrhage. In tissue samples and pus obtained during neurosurgery, Staphylococcus aureus was detected by a 16S rRNA-directed in situ hybridisation technique. Following long term cultivation, small colony variants (SCV) of methicillin resistant S aureus were identified. The patient was treated successfully with a combination of vancomycin and rifampin followed by prolonged treatment with teicoplanin, with no sign of infection on follow up nine months after discharge. This is the first report in which S aureus SCV have been identified as causative organisms in a patient with brain abscess and in which in situ hybridisation has been used to detect S aureus in a clinical specimen containing SCV. Antimicrobial agents such as rifampin which have intracellular activity should be included in treatment of infections caused by S aureus SCV.

Chromosomal rearrangements affecting biofilm production and antibiotic resistance in a Staphylococcus epidermidis strain causing shunt-associated ventriculitis.

Ziebuhr W, Dietrich K, Trautmann M, Wilhelm M. Institut für Molekulare Infektionsbiologie, Würzburg, Germany. w.ziebuhr@mail.uni-wuerzburg.de During two clinical courses of shunt-associated meningitis in a 3-month-old child, five multiresistant S. epidermidis isolates were obtained and analyzed with regard to biofilm production and antibiotic susceptibility. Three S. epidermidis strains, which were initially isolated from the cerebrospinal fluid, produced biofilms on polystyrene tissue culture plates. Following antibiotic treatment and subsequent exchange of the shunt system, sterilization of the CSF was achieved. However, after three weeks a relapse of the infection occurred. The two S. epidermidis isolates obtained now were biofilm negative, but showed an identical resistance pattern as those from the previous infection, except that resistance to rifampicin and increased mininal inhibitory concentrations of aminoglycoside antibiotics had emerged. DNA fingerprinting by PFGE indicated the clonal origin of all isolates. However, some DNA rearrangements and differences in the IS256-specific hybridization patterns could be identified in the isolates from the second infection period that led to altered biofilm formation and increased expression of aminoglycoside resistance traits. The data evidence that variation of biofilm expression occurs in vivo during an infection and highlight the extraordinary genome flexibility of pathogenic S. epidermidis.