Functional studies of the otrB gene from Streptomyces rimosus

Oxytetracyline, (OTC), is a secondary metabolite antibiotic produced by the actinomycete Streptomyces rimosus. All of the structural genes for OTC synthesis are clustered on the S. rimosus chromosome and flanked by resistance determinants, otrA and otrB. OtrA mediates resistance through non-covalent modification of the bacterial ribosome whilst otrB, the subject of this thesis, acts by efflux of the drug from the cell. At the outset of this thesis otrB had previously been cloned and sequenced. During the course of the work some discrepancies with previously published data were found, parts of the gene were then re-sequenced and a revised otrB sequence submitted to the NCBI database. The OtrB protein is a transmembrane protein belonging the Major facilitator Superfamily (MFS). Sequence comparison with other members of the family shows OtrB to be part of a subfamily of antibiotic transporters and multi drug resistance proteins made up from 14 transmembrane helices (6+2+6) arrangement. OtrB contains many conserved motifs typical of the subfamily and of the MFS. otrB was cloned into E. coli and expressed. The functional activity of the cloned gene was assessed by growth on various concentrations of OTC. Substrate specificity was investigated using TET and CTC in the growth media. Isolation of OtrB from E. coli as a polyhistidine fusion was attempted, reasons why this was not successful are discussed. Tetracycline exporters from Gram-negative bacteria generally contain 12 transmembrane helices (6+6). The relevance of the two "extra" helices present in OtrB was investigated by the construction and expression in E. coli, of a deletion mutant in which the two putative central helices were absent

Pneumococcal conjugate vaccine implementation in middle-income countries

Since 2000, the widespread adoption of pneumococcal conjugate vaccines (PCVs) has had a major impact in the prevention of pneumonia. Limited access to international financial support means some middle-income countries (MICs) are trailing in the widespread use of PCVs. We review the status of PCV implementation, and discuss any needs and gaps related to low levels of PCV implementation in MICs, with analysis of possible solutions to strengthen the PCV implementation process in MICs

Pneumococcal 13-valent conjugate vaccine for the prevention of invasive pneumococcal disease in children and adults

Pneumococcal disease remains a global problem despite the availability of effective conjugate vaccines. The 13-valent pneumococcal conjugate vaccine (PCV13) extends the valency of PCV7 by including six additional serotypes highly associated with invasive pneumococcal disease (IPD). Comparisons between PCV13 and PCV7 or the pneumococcal polysaccharide vaccine have established noninferiority of PCV13 for both safety and immunogenicity profiles for use in children and adults, respectively. At the end of 2011, PCV13 had been approved and launched in 104 countries worldwide, with 54 including the vaccine in their pediatric national immunization program. Surveillance data from early adopters of PCV13 has indicated reductions are occurring in both overall IPD and IPD caused by the six non-PCV7 serotypes; early reports of serotype replacement in carriage are also emerging. While serotype replacement for PCV7 was observed to varying degrees for both carriage and disease, the extent to which this will occur for PCV13 is yet to be determined

PclA, a pneumococcal collagen-like protein with selected strain distribution, contributes to adherence and invasion of host cells

Analysis of Streptococcus pneumoniae sequenced genomes revealed a region present only in selected strains consisting of two ORFs: a putative cell wall anchored protein and a putative transcriptional regulator. The cell wall anchored protein contains large regions of collagen-like repeats, the number of which varies between strains. We have therefore named this protein PclA for pneumococcal collagen-like protein A. The second gene, spr1404, encodes a putative transcriptional regulator. We examined the strain distribution of these two genes among a collection of clinical isolates from invasive pneumococcal disease and found them to be present in 39% of the strains examined. Strains were either positive for both genes or lacked both, with the two genes always present together in the same location of the genome. RT-PCR analysis revealed that pclA is transcribed in vitro, even in the absence of spr1404. Single deletion mutants lacking either gene were not attenuated in a mouse model of invasive pneumonia. However, the pclA mutant was defective in adherence and invasion of host cells in vitr

13-valent pneumococcal conjugate vaccine (PCV13)

The thirteen valent pneumococcal conjugate vaccine (PCV13, Prevenar 13Ô) is the broader coverage successor to the highly effective seven valent vaccine (PCV7, PrevenarÔ) which has reduced rates of pneumococcal disease in many countries. Despite the success of PCV7, pneumococcal disease due to non-PCV7 serotypes remains a threat in many settings, in particular many developing countries with a high burden of pneumococcal disease where serotype 1 and 5 are among the most common serotypes. Disease due to certain non-PCV7 serotypes, in particular serotype 19A has also begun to increase in incidence in countries with widespread use of PCV7. PCV13 consists of thirteen pneumococcal capsular polysaccharides individually conjugated to the diphtheria-derived protein carrier CRM197. In addition to serotypes 4, 6B, 9V, 14, 18C, 19F and 23F included in PCV7, PCV13 also includes serotypes 1, 3, 5, 6A, 7F and 19A. PCV13 was licensed on the basis of non-inferiority trials and has proved to be at least as safe and effective as PCV7. PCV13 replaced PCV7 in the childhood immunisation schedules of the USA and UK in 2010 and is being rolled out to an increasing number of developing countries during 2011. Here we review the current literature regarding this vaccine, describing safety, efficacy, global serotype coverage and use and future directions

Evaluation of swabbing methods for estimating the prevalence of bacterial carriage in the upper respiratory tract: a cross sectional study

Objectives Bacterial carriage in the upper respiratory tract is usually asymptomatic but can lead to respiratory tract infection (RTI), meningitis and septicaemia. We aimed to provide a baseline measure of Streptococcus pneumoniae, Moraxella catarrhalis, Pseudomonas aeruginosa, Staphylococcus aureus, Haemophilus influenzae and Neisseria meningitidis carriage within the community. Self-swabbing and healthcare professional (HCP) swabbing were compared. Design Cross-sectional study. Setting Individuals registered at 20 general practitioner practices within the Wessex Primary Care Research Network South West, UK. Participants 10?448 individuals were invited to participate; 5394 within a self-swabbing group and 5054 within a HCP swabbing group. Self-swabbing invitees included 2405 individuals aged 0–4?years and 3349 individuals aged ?5?years. HCP swabbing invitees included 1908 individuals aged 0–4?years and 3146 individuals aged ?5?years. Results 1574 (15.1%) individuals participated, 1260 (23.4%, 95% CI 22.3% to 24.5%) undertaking self-swabbing and 314 (6.2%, 95% CI 5.5% to 6.9%) undertaking HCP-led swabbing. Participation was lower in young children and more deprived practice locations. Swab positivity rates were 34.8% (95% CI 32.2% to 37.4%) for self-taken nose swabs (NS), 19% (95% CI 16.8% to 21.2%) for self-taken whole mouth swabs (WMS), 25.2% (95% CI 20.4% to 30%) for nasopharyngeal swabs (NPS) and 33.4% (95% CI 28.2% to 38.6%) for HCP-taken WMS. Carriage rates of S. aureus were highest in NS (21.3%). S. pneumoniae carriage was highest in NS (11%) and NPS (7.4%). M. catarrhalis carriage was highest in HCP-taken WMS (28.8%). H. influenzae and P. aeruginosa carriage were similar between swab types. N. meningitidis was not detected in any swab. Age and recent RTI affected carriage of S. pneumoniae and H. influenzae. Participant costs were lower for self-swabbing (£41.21) versus HCP swabbing (£69.66). Conclusions Higher participation and lower costs of self-swabbing as well as sensitivity of self-swabbing favour this method for use in large population-based respiratory carriage studies. <br/

Nasopharyngeal bacterial carriage in the conjugate vaccine era with a focus on pneumococci

Seven-valent pneumococcal conjugate vaccine (PCV7) was included in the UK national immunisation program in 2006, and this was replaced by thirteen-valent PCV in 2010. During this time, the carriage of vaccine-type Streptococcus pneumoniae decreased but pneumococcal carriage remained stable due to increases in non-vaccine-type S. pneumoniae. Carriage studies have been undertaken in various countries to monitor vaccine-type replacement and to help predict the serotypes, which may cause invasive disease. There has been less focus on how conjugate vaccines indirectly affect colonization of other nasopharyngeal bacteria. If the nasopharynx is treated as a niche, then bacterial dynamics are accepted to occur. Alterations in these dynamics have been shown due to seasonal changes, antibiotic use, and sibling/day care interaction. It has been shown that, following PCV7 introduction, an eradication of pneumococcal vaccine types has resulted in increases in the abundance of other respiratory pathogens including Haemophilus influenzae and Staphylococcus aureus. These changes are difficult to attribute to PCV7 introduction alone and these studies do not account for further changes due to PCV13 implementation. This review aims to describe nasopharyngeal cocarriage of respiratory pathogens in the PCV era

Genomic diversity between strains of the same serotype and Multilocus sequence type among pneumococcal clinical isolates

The important human pathogen Streptococcus pneumoniae is known to be a genetically diverse species. We haveused comparative genome hybridization (CGH) microarray analysis to investigate this diversity in a collection ofclinical isolates including several capsule serotype 14 pneumococci, a dominant serotype among disease isolates. Wehave identified three new regions of diversity among pneumococcal isolates and, importantly, clearly demonstrategenetic differences between strains of the same multilocus sequence type (ST) and capsule serotype. CGH maytherefore, under certain circumstances, prove to be a valuable tool to supplement current typing methods. Finally,we show that these clonal strains with the same serotype and ST behave differently in an animal model. Strains ofthe same ST and serotype therefore have important genetic and phenotypic differences