Interrelationship of Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus colonization within and between pneumococcal-vaccine naïve mother-child dyads

Impact of vaccines on Staphylococcus aureus colonization: A systematic review and meta-analysis

BACKGROUND

Concerns regarding vaccine effects on microbial ecology have led to interest in the non-targeted effects of vaccinations.

OBJECTIVES

To systematically review the literature related to the impact of vaccines on S. aureus carriage.

METHODS

We conducted a systematic search of MEDLINE, Scopus and clinical trials.gov for studies that assessed vaccine effects on S. aureus carriage in children and adults using predefined inclusion and exclusion criteria. Generic inverse variance meta-analysis was done using random-effects models.

RESULTS

Of 1,686 studies screened, 34 were eligible for inclusion, of which 22 were observational and 12 randomized controlled studies (RCTs). 88.2% (30/34) provided data on pneumococcal conjugate vaccines (PCV), 23.5% on influenza vaccines (8/34), 6% on other vaccines (2/34) and 20.6% on more than one vaccine (7/34). Most studies tested nasopharyngeal specimens (82.3%, 28/34). Among children aged more than 18-24 months, evidence suggested no effect of PCV on S. aureus colonization [2 RCTs, pooled OR 1.09 (95% CI 0.94-1.25), p 0.25; 7 observational studies, pooled OR: 1.02 (95% CI 0.83-1.25), p 0.86]. A transient increase in S. aureus carriage in PCV-vaccinated infants 9-15 months was shown [2 RCTs, pooled OR 1.11 (95% CI 1.00-1.23), p 0.06; 4 observational studies, pooled OR 1.64 (95% CI 1.00-2.68), p 0.05]. A reduction in S. aureus carriage was observed after influenza vaccination [4 observational studies; OR 0.85 (95% CI 0.78-0.94), p 0.0001]. Based on the Grading of Recommendations Assessment, Development and Evaluation, the quality of evidence was considered low for randomized and very low for non-randomized trials.

CONCLUSION

Evidence did not suggest long-term effects of pneumococcal vaccinations on S. aureus nasopharyngeal carriage in children, however transient niche changes may occur in infants. Influenza vaccination was related to decreased rates of S. aureus carriage. Data regarding other vaccines is scarce. Further research and ongoing surveillance are needed to monitor colonization changes.

Nasopharyngeal Staphylococcus aureus colonization among HIV-infected children in Addis Ababa, Ethiopia: antimicrobial susceptibility pattern and association with Streptococcus pneumoniae colonization

Background

Staphylococcus aureus and Streptococcus pneumoniae are common inhabitants of the nasopharynx of children. HIV-infected children have higher risk of invasive diseases caused by these pathogens. With widespread use of pneumococcal conjugate vaccines and the emergence of methicillin-resistant S. aureus , the interaction between S. aureus and S. pneumoniae is of a particular significance. We sought to determine the magnitude of colonization by methicillin-sensitive and -resistant S. aureus and colonization by S. pneumoniae ; associated risk factors and antimicrobial susceptibility pattern among HIV-infected children in Addis Ababa, Ethiopia.

Method

A prospective observational study was conducted among 183 HIV-infected children at ALERT hospital Addis Ababa, Ethiopia from September 2016 to August 2018. S. aureus and S. pneumoniae were identified using standard bacteriological techniques, antimicrobial susceptibility testing was performed on S. aureus and screening for methicillin resistance was carried out by amplifying the mecA gene. Risk factors were analysed by using binary logistic regression.

Results

The prevalence of nasopharyngeal S. aureus , MRSA and S. pneumoniae colonization were 27.3, 2.7 and 43.2 %, respectively. Multivariable analysis indicated an inverse association between S. aureus and S. pneumoniae nasopharyngeal colonization [aOR, 0.49; CI, (0.24, 0.99); P=0.046]. The highest level of resistance in both methicillin-sensitive S. aureus (MSSA) and MRSA was observed against tetracycline.

Conclusions

. We found an inverse association between S. aureus and S. pneumoniae colonization among HIV-infected children. Continued assessment of the impact of pneumococcal conjugate vaccines and antiretroviral therapy on nasopharyngeal bacterial ecology is warranted.

Non-diphtheriae Corynebacterium species are associated with decreased risk of pneumococcal colonization during infancy

Streptococcus pneumoniae (pneumococcus) is a leading cause of severe infections among children and adults. Interactions between commensal microbes in the upper respiratory tract and S. pneumoniae are poorly described. In this study, we sought to identify interspecies interactions that modify the risk of S. pneumoniae colonization during infancy and to describe development of the upper respiratory microbiome during infancy in a sub-Saharan African setting. We collected nasopharyngeal swabs monthly (0-6 months of age) or bimonthly (6-12 months of age) from 179 mother-infant dyads in Botswana. We used 16S ribosomal RNA gene sequencing to characterize the nasopharyngeal microbiome and identified S. pneumoniae colonization using a species-specific PCR assay. We detect S. pneumoniae colonization in 144 (80%) infants at a median age of 71 days and identify a strong negative association between the relative abundance of the bacterial genera Corynebacterium within the infant nasopharyngeal microbiome and the risk of S. pneumoniae colonization. Using in vitro cultivation experiments, we demonstrate growth inhibition of S. pneumoniae by secreted factors from strains of several Corynebacterium species isolated from these infants. Finally, we demonstrate that antibiotic exposures and the winter season are associated with a decline in the relative abundance of Corynebacterium within the nasopharyngeal microbiome, while breastfeeding is associated with an increase in the Corynebacterium relative abundance. Our findings provide novel insights into the interspecies interactions that contribute to colonization resistance to S. pneumoniae and suggest that the nasopharyngeal microbiome may be a previously unrecognized mechanism by which environmental factors influence the risk of pneumococcal infections during childhood. Moreover, this work lays the foundation for future studies seeking to use targeted manipulation of the nasopharyngeal microbiome to prevent infections caused by S. pneumoniae.

Factors associated with pneumococcal nasopharyngeal carriage: A systematic review

Pneumococcal disease is a major contributor to global childhood morbidity and mortality and is more common in low- and middle-income countries (LMICs) than in high-income countries. Pneumococcal carriage is a prerequisite for pneumococcal disease. Pneumococcal conjugate vaccine reduces vaccine-type carriage and disease. However, pneumococcal carriage and disease persist, and it is important to identify other potentially modifiable factors associated with pneumococcal carriage and determine if risk factors differ between low, middle, and high-income countries. This information may help inform pneumococcal disease prevention programs. This systematic literature review describes factors associated with pneumococcal carriage stratified by country income status and summarises pneumococcal carriage rates for included studies. We undertook a systematic search of English-language pneumococcal nasopharyngeal carriage studies up to 30th June 2021. Peer-reviewed studies reporting factors associated with overall pneumococcal nasopharyngeal carriage in healthy, community-based study populations were eligible for inclusion. Two researchers independently reviewed studies to determine eligibility. Results are presented as narrative summaries. This review is registered with PROSPERO, CRD42020186914. Eighty-two studies were included, and 46 (56%) were conducted in LMICs. There was heterogeneity in the factors assessed in each study. Factors positively associated with pneumococcal carriage in all income classification were young age, ethnicity, symptoms of respiratory tract infection, childcare attendance, living with young children, poverty, exposure to smoke, season, and co-colonisation with other pathogens. Breastfeeding and antibiotic use were protective against carriage in all income classifications. Median (interquartile range) pneumococcal carriage rates differed by income classification, ranging from 51% (19.3-70.2%), 38.5% (19.3-51.6%), 31.5% (19.0-51.0%), 28.5% (16.8-35.4%), (P = 0.005) in low-, lower-middle, upper-middle, and high-income classifications, respectively. Our findings suggest that where measured, factors associated with pneumococcal nasopharyngeal carriage are similar across income classifications, despite the highest pneumococcal carriage rates being in low-income classifications. Reducing viral transmission through vaccination and public health interventions to address social determinants of health would play an important role.

The Etiology of Pneumonia in HIV-1-infected South African Children in the Era of Antiretroviral Treatment: Findings From the Pneumonia Etiology Research for Child Health (PERCH) Study

BACKGROUND

HIV-1 infection predisposes to an increased burden of pneumonia caused by community-acquired and opportunistic pathogens.

METHODS

Within the context of the Pneumonia Etiology Research for Child Health case-control study of under 5 pneumonia, we investigated the etiology of World Health Organization-defined severe/very severe pneumonia requiring hospitalization in South African HIV-infected children. Nasopharyngeal-oropharyngeal swabs and blood, collected from cases and age- and season-matched HIV-infected controls attending outpatient antiretroviral therapy (ART) clinics, were analyzed using molecular diagnostic methods. Cases were also investigated for tuberculosis. Etiologic fractions among cases with radiologically confirmed pneumonia were derived using Bayesian analytic techniques.

RESULTS

Of 115 HIV-infected cases, 89 (77.4%) had radiologically confirmed pneumonia. Severe immunosuppression (adjusted odds ratio, 32.60; 95% confidence interval, 7.25-146.64) was significantly associated with radiologically confirmed pneumonia. Cotrimoxazole prophylaxis (46.4% vs. 77.4%) and ART (28.2% vs. 83.1%) coverage were significantly lower in cases compared with ART-clinic controls. An etiologic agent was identified in 99.0% of the radiologically confirmed cases. The 'top 4' pathogens associated with radiologically confirmed pneumonia were Pneumocystis jirovecii [23.0%; 95% credible interval (CrI), 12.4%-31.5%], Staphylococcus aureus (10.6%; 95% CrI, 2.2%-20.2%), pneumococcus (9.5%; 95% CrI, 2.2%-18.0%) and respiratory syncytial virus (9.3%; 95% CrI, 2.2%-14.6%). Bacteremia (6.7%) and in-hospital death (10.1%) were frequent among those with radiologically confirmed disease.

CONCLUSIONS

Pneumocystis jirovecii, S. aureus, pneumococcus and respiratory syncytial virus contribute a considerable burden of radiologically confirmed pneumonia in South African HIV-infected children under 5 years. Expediting access to ART and cotrimoxazole prophylaxis would decrease the burden of pneumonia in these children.

Metal/metal oxide nanocomposites for bactericidal effect: A review

Many microbial species causing infectious disease all over the world became a social burden and creating threat among community. These microbes possess long lifetime, enhancing mortality and morbidity rate in affected organisms. In this condition, the treatment was ineffective and more chances of spreading of infection into other organisms. Hence, it is necessary to initiate infection control efforts and prevention activities against multidrug resistant microbes, to reduce the death rate of people. Seriously concerning towards this problem progress was shown in developing significant drugs with least side effects. Emergence of nanoparticles and its novelty showed effective role in targeting and destructing microbes well. Further, many research works have shown nanocomposites developed from nanoparticles coupled with other nanoparticles, polymers, carbon material acted as an exotic substance against microbes causing severe loss. However, metal and metal oxide nanocomposites have gained interest due to its small size and enhancing the surface contact with bacteria, producing damage to it. The bactericidal mechanism of metal and metal oxide nanocomposites involve in the production of reactive oxygen species which includes superoxide radical anions, hydrogen peroxide anions and hydrogen peroxide which interact with the cell wall of bacteria causing damage to the cell membrane in turn inhibiting the further growth of cell with leakage of internal cellular components, leading to death of bacteria. This review provides the detailed view on antibacterial activity of metal and metal oxide nanocomposite which possessed novelty due to its physiochemical changes.

Resident bacteria contribute to opportunistic infections of the respiratory tract

Opportunistic pathogens frequently cause volatile infections in hosts with compromised immune systems or a disrupted normal microbiota. The commensalism of diverse microorganisms contributes to colonization resistance, which prevents the expansion of opportunistic pathogens. Following microbiota disruption, pathogens promptly adapt to altered niches and obtain growth advantages. Nevertheless, whether and how resident bacteria modulate the growth dynamics of invasive pathogens and the eventual outcome of such infections are still unclear. Here, we utilized birds as a model animal and observed a resident bacterium exacerbating the invasion of Avibacterium paragallinarum (previously Haemophilus paragallinarum) in the respiratory tract. We first found that negligibly abundant Staphylococcus chromogenes, rather than Staphylococcus aureus, played a dominant role in Av. paragallinarum-associated infectious coryza in poultry based on epidemic investigations and in vitro analyses. Furthermore, we determined that S. chromogenes not only directly provides the necessary nutrition factor nicotinamide adenine dinucleotide (NAD⁺) but also accelerates its biosynthesis and release from host cells to promote the survival and growth of Av. paragallinarum. Last, we successfully intervened in Av. paragallinarum-associated infections in animal models using antibiotics that specifically target S. chromogenes. Our findings show that opportunistic pathogens can hijack commensal bacteria to initiate infection and expansion and suggest a new paradigm to ameliorate opportunistic infections by modulating the dynamics of resident bacteria.

There is an urgent need for novel intervention strategies and techniques to address the increasing dissemination of multidrug-resistant Gram-negative bacterial pathogens. More importantly, secondary bacterial infections are common in clinical practice, whereas the growth dynamics of each individual in such coinfections are still complicated and elusive. In the current study, we first identified Staphylococcus spp., especially negligibly abundant S. chromogenes, facilitating the pathogenesis of Av. paragallinarum, a Gram-negative bacterium responsible for severe and acute avian respiratory disease worldwide. Furthermore, we developed therapeutic strategies using specific antibiotics against Staphylococcus spp. to relieve clinical symptoms and reduce Av. paragallinarum-associated infections in chickens. These results show that implementation of a proper intervention strategy can prevent opportunistic infections by regulating the microbiota and elucidate the development of alternative approaches for treating Gram-negative pathogenic bacterial infections.

Friend or Foe: Interbacterial Competition in the Nasal Cavity

Like other microbes that live on or in the human body, the bacteria that inhabit the upper respiratory tract, in particular the nasal cavity, have evolved to survive in an environment that presents a number of physical and chemical challenges; these microbes are constantly bombarded with nutritional fluctuations, changes in humidity, the presence of inhaled particulate matter (odorants and allergens), and competition with other microbes. Indeed, only a specialized set of species is able to colonize this niche and successfully contend with the host's immune system and the constant threat from competitors. To this end, bacteria that live in the nasal cavity have evolved a variety of approaches to outcompete contenders for the limited nutrients and space; broadly speaking, these strategies may be considered a type of "bacterial warfare." A greater molecular understanding of bacterial warfare has the potential to reveal new approaches or molecules that can be developed as novel therapeutics. As such, there are many studies within the last decade that have sought to understand the complex polymicrobial interactions that occur in various environments. Here, we review what is currently known about the age-dependent structure and interbacterial relationships within the nasal microbiota and summarize the molecular mechanisms that are predicted to dictate bacterial warfare in this niche. Although the currently described interactions are complex, in reality, we have likely only scratched the surface in terms of a true understanding of the types of interbacterial competition and cooperation that are thought to take place in and on the human body.

Bacterial nasopharyngeal carriage following infant immunization with pneumococcal conjugate vaccines according to a 2+1 schedule in children in South Africa: an exploratory analysis of two clinical trials

Background: We evaluated bacterial nasopharyngeal carriage (NPC) prevalence and cumulative acquisition following 7-valent pneumococcal conjugate vaccine (PCV7) or pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) administration. Methods: Participants were children from two clinical trials in a South African center who received PCV7 (n = 250) or PHiD-CV (n = 100) at ~6 weeks, ~14 weeks, and ~9-10 months of age, and were enrolled between Dec2009-Apr2010 and Mar2009-May2010 in the PCV7 and PHiD-CV studies, respectively. Sample collection, most microbiological assessments, and data re-analysis methods were identical. Results: NPC prevalence of any pneumococcal serotype was 18.5% and 17.0% at pre-vaccination, and 63.1% and 67.3% in 24-27 month-old children among PCV7 and PHiD-CV recipients, respectively. In 24-27 month-old children, 96.1% and 99.0% of PCV7 and PHiD-CV recipients had acquired ≥1 pneumococcal serotype, 53.7% and 62.9% ≥1 PCV7 serotype, 1.5%, and 3.1% ≥1 of serotypes 1, 5 or 7F, 23.2% and 19.6% serotype 6A, 23.2% and 21.7% serotype 19A, 88.7%, and 91.0% H. influenzae, and 50.3% and 62.9% Staphylococcus aureus, respectively. Conclusions: This analysis of two concurrent clinical trials did not reveal differences in bacterial NPC prevalence or acquisition in PCV7- and PHiD-CV-vaccinated children. Trial registration: South African National Clinical Trial Register (NHREC DOH-27-0511-299); ClinicalTrials.gov (NCT00829010).

Impact of pneumococcal conjugate vaccine on the carriage density of Streptococcus pneumoniae and Staphylococcus aureus in children living with HIV: a nested case-control study

Nasopharyngeal colonization density of Streptococcus pneumoniae (pneumococcus) is associated with disease severity and transmission. Little is known about the density of pneumococcal carriage in children with HIV (CLH). Pneumococcal vaccines may impact the density of pneumococcus and competing microbes within the nasopharynx. We examined the impact of one dose of PCV13 on carriage density of pneumococcus and Staphylococcus aureus, in CLH, HIV-uninfected children (HUC), and their unvaccinated parents. We conducted a pilot-nested case-control study, within a larger prospective cohort study, on the impact of PCV13, in families in West Bengal India. Quantitative real-time PCR was run on 147 nasopharyngeal swabs from 27 CLH and 23 HUC, and their parents, before and after PCV13 immunization. CLH had higher median pneumococcal carriage density, compared to HUC: 6.28 × 108 copies/mL vs. 2.11 × 105 copies/mL (p = .005). Following one dose of PCV13, pneumococcal densities dropped in both groups, with an increase in S. aureus carriage to 80% from 48% in CLH, and to 60% in HUC from 25%. While limited in sample size, this pilot study shows that CLH carried higher densities of pneumococcus. PCV13 was associated with a decrease in pneumococcal density and a temporal increase in S. aureus carriage regardless of HIV status.

Experimental Evolution In Vivo To Identify Selective Pressures during Pneumococcal Colonization

Experimental evolution is a powerful technique to understand how populations evolve from selective pressures imparted by the surrounding environment. With the advancement of whole-population genomic sequencing, it is possible to identify and track multiple contending genotypes associated with adaptations to specific selective pressures. This approach has been used repeatedly with model species in vitro, but only rarely in vivo Herein we report results of replicate experimentally evolved populations of Streptococcus pneumoniae propagated by repeated murine nasal colonization with the aim of identifying gene products under strong selection as well as the population genetic dynamics of infection cycles. Frameshift mutations in one gene, dltB, responsible for incorporation of d-alanine into teichoic acids on the bacterial surface, evolved repeatedly and swept to high frequency. Targeted deletions of dltB produced a fitness advantage during initial nasal colonization coupled with a corresponding fitness disadvantage in the lungs during pulmonary infection. The underlying mechanism behind the fitness trade-off between these two niches was found to be enhanced adherence to respiratory cells balanced by increased sensitivity to host-derived antimicrobial peptides, a finding recapitulated in the murine model. Additional mutations that are predicted to affect trace metal transport, central metabolism, and regulation of biofilm production and competence were also selected. These data indicate that experimental evolution can be applied to murine models of pathogenesis to gain insight into organism-specific tissue tropisms.IMPORTANCE Evolution is a powerful force that can be experimentally harnessed to gain insight into how populations evolve in response to selective pressures. Herein we tested the applicability of experimental evolutionary approaches to gain insight into how the major human pathogen Streptococcus pneumoniae responds to repeated colonization events using a murine model. These studies revealed the population dynamics of repeated colonization events and demonstrated that in vivo experimental evolution resulted in highly reproducible trajectories that reflect the environmental niche encountered during nasal colonization. Mutations impacting the surface charge of the bacteria were repeatedly selected during colonization and provided a fitness benefit in this niche that was counterbalanced by a corresponding fitness defect during lung infection. These data indicate that experimental evolution can be applied to models of pathogenesis to gain insight into organism-specific tissue tropisms.

Co infection of respiratory syncytial viruses (RSV) and streptococcus pneumonia modulates pathogenesis and dependent of serotype and phase variant

Streptococcus pneumoniae (pneumococcus) is touted to be the generally found pathogen in patients with respiratory issues and there is an epidemiologic linkage present between Respiratory syncytial virus (RSV). This study aim at investigating the interaction between RSV and two serotypes of S. pneumoniae using a distinct animal model and a well-established colonizing pneumococcal strain. Phase variants phenotype of each strain was determined under oblique light. Co infection model was developed using BALB/c mice housed in a BSL-2 facility. Coinfection experiments were performed and number of bacterial colonies was quantified and phase determination was evaluated^. RSV was detected in sample through real-time quantitative PCR. Adherence assays were performed to determine adherence of Spn strains and its knock out ΔNanA to nasopharyngeal carcinoma (NPC) epithelial CNE3 cell line. The biofilm viability was determined and phase composition was counted using plate count. Neuraminidase activity was measured in fluorometircassessed using 2'-(4-methylumbelliferyl)-α-D-N-acetylneuraminic acid (MUAN) as substrate as described in earlier literature. The GraphPad Software version 5.01 i.e., GraphPad Prism was used to conduct the statistical analysis. The extent of bacterial colonization was increased significantly (p < 0.05), when the mice were co infected. Nasal epithelium remained intact in mock sample with features of a thick mucociliary border. A small percentage of pneumococci exhibit phase variation between opaque phase and transparent phase. The percentage adherent of both phase were not found to be varying significantly within serotype but it was seen that nonpathogenic type 27 was more adherent. Biofilm formation was selectively more for transparent phase from a mixed-phase inoculum. Adherence of both phase variant of S. pneumoniae to nasopharyngeal epithelial cells 2 h post infection expressed as the percentage of adherent bacteria relative to the inoculum. In absence of viral infection, the nasal colonization of the opaque and the transparent variant was increased many folds, which was a significant differences. The extent of nasal colonization by the ΔNanA mutant strain were significantly reduced post-bacterial infection for both type of wild-type (P < 0.05). The findings explore insights into the interactions occurring between S. pneumoniae and RSV during respiratory infections and pneumococcal acquisition, indicate that pneumococcal serotypes have different ability to cause infection as well as co infections and potentially follow an unappreciated mechanism. Much more research work is needed to further understand the minutiae of this interaction within co-infection process.

High-density Bacterial Nasal Carriage in Children Is Transient and Associated With Respiratory Viral Infections-Implications for Transmission Dynamics

BACKGROUND

This longitudinal study describes the associations between respiratory viral infections, rhinitis and the prevalence and density of the common nasopharyngeal bacterial colonizers, Streptococcus pneumoniae (Sp), Moraxella catarrhalis (Mc), Haemophilus influenzae (Hi) and Staphylococcus aureus.

METHODS

In an observational cohort study, 161 children attending day care centers in Bristol, United Kingdom, were recruited. Monthly nasopharyngeal swabs were taken and stored frozen in Skim-milk, tryptone, glucose and glycerin broth (STGG) broth. Quantitative polymerase chain reaction was used for detection of respiratory viruses and 4 bacterial species. t tests and logistic regression models were used for analysis.

RESULTS

The frequent colonisers, Sp, Mc and Hi were more frequently found at high density in contrast to Staphylococcus aureus although temporally, high-density carriage was short lived. Respiratory viral infections and symptoms of rhinitis were both independently and consistently associated with higher bacterial density with an observed 2-fold increase in density for Sp, Mc and Hi (P = 0.004-0.017).

CONCLUSIONS

For Sp and Hi, the association between young age and higher bacterial DNA density was explained by more frequent viral infection and increased nasal discharge, while the associations between some viral specie's and some bacterial species' density appear to be stronger than others. Increased colonization density and rhinitis may promote transmission of these commonly carried organisms.

"Epidemiology and aetiology of influenza-like illness among households in metropolitan Vientiane, Lao PDR": A prospective, community-based cohort study

Respiratory diseases are a major contributor to morbidity and mortality in many tropical countries, including Lao PDR. However, little has been published regarding viral or bacterial pathogens that can contribute to influenza-like illness (ILI) in a community setting. We report on the results of a community-based surveillance that prospectively monitored the incidence of ILI and its causative pathogens in Vientiane capital in Lao PDR. A cohort of 995 households, including 4885 study participants, were followed-up between May 2015 and May 2016. Nasopharyngeal swabs, throat swabs, and sputum specimens were collected from ILI cases identified through active case-finding. Real-Time PCR was used to test nasopharyngeal swabs for 21 respiratory pathogens, while throat and sputum samples were subjected to bacterial culture. Generalized linear mixed models were used to assess potential risk factors for associations with ILI. In total, 548 episodes of ILI were reported among 476 (9.7%) of the study participants and 330 (33.2%) of the study households. The adjusted estimated incidence of ILI within the study area was 10.7 (95%CI: 9.4-11.9) episodes per 100 person-years. ILI was significantly associated with age group (p<0.001), sex (p<0.001), and number of bedrooms (p = 0.04) in multivariate analysis. In 548 nasopharyngeal swabs, the most commonly detected potential pathogens were Streptococcus pneumoniae (17.0%), Staphylococcus aureus (11.3%), influenza A (11.1%; mostly subtype H3N2), rhinovirus (7.5%), and influenza B (8.0%). Streptococci were isolated from 42 (8.6%) of 536 throat swabs, most (27) of which were Lancefield Group G. Co-infections were observed in 132 (24.1%) of the 548 ILI episodes. Our study generated valuable data on respiratory disease burden and patterns of etiologies associated with community-acquired acute respiratory illness Laos. Establishment of a surveillance strategy in Laos to monitor trends in the epidemiology and burden of acute respiratory infections is required to minimize their impact on human health.

Indoor air pollution and tobacco smoke exposure: impact on nasopharyngeal bacterial carriage in mothers and infants in an African birth cohort study

Indoor air pollution (IAP) or environmental tobacco smoke (ETS) exposure may influence nasopharyngeal carriage of bacterial species and development of lower respiratory tract infection (LRTI). The aim of this study was to longitudinally investigate the impact of antenatal or postnatal IAP/ETS exposure on nasopharyngeal bacteria in mothers and infants. A South African cohort study followed mother-infant pairs from birth through the first year. Nasopharyngeal swabs were taken at birth, 6 and 12 months for bacterial culture. Multivariable and multivariate Poisson regression investigated associations between nasopharyngeal bacterial species and IAP/ETS. IAP exposures (particulate matter, carbon monoxide, nitrogen dioxide, volatile organic compounds) were measured at home visits. ETS exposure was measured through maternal and infant urine cotinine. Infants received the 13-valent pneumococcal and Haemophilus influenzae B conjugate vaccines. There were 881 maternal and 2605 infant nasopharyngeal swabs. Antenatal ETS exposure was associated with Streptococcus pneumoniae carriage in mothers (adjusted risk ratio (aRR) 1.73 (95% CI 1.03-2.92)) while postnatal ETS exposure was associated with carriage in infants (aRR 1.14 (95% CI 1.00-1.30)) Postnatal particulate matter exposure was associated with the nasopharyngeal carriage of H. influenzae (aRR 1.68 (95% CI 1.10- 2.57)) or Moraxella catarrhalis (aRR 1.42 (95% CI 1.03-1.97)) in infants. Early-life environmental exposures are associated with an increased prevalence of specific nasopharyngeal bacteria during infancy, which may predispose to LRTI.

Pneumococcal vaccine impacts on the population genomics of non-typeable Haemophilus influenzae

The implementation of pneumococcal conjugate vaccines (PCVs) has led to a decline in vaccine-type disease. However, there is evidence that the epidemiology of non-typeable Haemophilus influenzae (NTHi) carriage and disease can be altered as a consequence of PCV introduction. We explored the epidemiological shifts in NTHi carriage using whole genome sequencing over a 5-year period that included PCV13 replacement of PCV7 in the UK’s National Immunization Programme in 2010. Between 2008/09 and 2012/13 (October to March), nasopharyngeal swabs were taken from children <5 years of age. Significantly increased carriage post-PCV13 was observed and lineage-specific associations with Streptococcus pneumoniae were seen before but not after PCV13 introduction. NTHi were characterized into 11 discrete, temporally stable lineages, congruent with current knowledge regarding the clonality of NTHi. The increased carriage could not be linked to the expansion of a particular clone and different co-carriage dynamics were seen before PCV13 implementation when NTHi co-carried with vaccine serotype pneumococci. In summary, PCV13 introduction has been shown to have an indirect effect on NTHi epidemiology and there exists both negative and positive, distinct associations between pneumococci and NTHi. This should be considered when evaluating the impacts of pneumococcal vaccine design and policy.

Pharyngeal colonization and drug resistance profiles of Morraxella catarrrhalis, Streptococcus pneumoniae, Staphylococcus aureus, and Haemophilus influenzae among HIV infected children attending ART Clinic of Felegehiwot Referral Hospital, Ethiopia

Background

Asymptomatic pharyngeal colonization by potential bacteria is the primary reservoir for bacterial species within a population and is considered a prerequisite for development of major childhood diseases such as sinusitis, otitis media, pneumonia, bacteremia, and meningitis. However, there is dearth of data on the colonization and drug resistance pattern of the main bacterial pathogens in the pharynx of HIV infected children in Ethiopia. Therefore, this study determined the pharyngeal colonization and drug resistance profile of bacterial pathogens in HIV infected children attending ART clinic of Felegehiwot Referral Hospital (FHRH), Amhara Region, Ethiopia.

Methods

A hospital based cross-sectional study was conducted from May 2016 to June 2017 at the ART clinic of FHRH. A total of 300 HIV infected children were enrolled in the study. Data on socio-demographic characteristics of the study participants were collected with face-to-face interview and patient—card review using structured questionnaire. Bacterial species were identified using standard bacteriological techniques. Drug susceptibility testing was performed using disk diffusion technique. Chi-square test was done to determine associations among variables.

Results

The median age of the participants was 11 years. Overall, 153 (51%) of children were colonized by respiratory bacteria in their pharynx. Colonization rate was higher in children from mothers who had attained college and above levels of education than others (P = 0.04). It was also higher in children without the sign of malnutrition than others (P = 0.004). The colonization rate of S.aureus, M.catarrhalis, S.pneumoniae and H.influenzae were 88 (29%), 37 (12.3%), 31 (10.3%) and 6 (2%), respectively. S.aureus—M.catarrhalis concurrent colonization was found in 14 (4.7%) of children. Age (P = 0.03), schooling (P = 0.045) and history of running nose (P = 0.043) were significantly associated with S.aureus colonization. Living in urban setting (P = 0.042) and children from mothers with college and above levels of education (P = 0.002) were significantly associated with M.catarrhalis colonization. Majority of the isolates were resistant to penicillin (68.5%) and cotrimoxazole (52.5%).S.aureus isolates were resistant to penicillin (84.1%) and cotrimoxazole (51.1%).M.catarrhalis isolates were resistant to penicillin (94.6%), erythromycin (86.5%)and cotrimoxazole (78.4%). Overall, 99 (59.3%) of the isolates were multi-drug (MDR) resistant. The overall MDR rates among S.aureus, M.catarrhalis and S.pneumoniae isolates were 65.9%, 78.4% and 22.6%, respectively.

Conclusions

Pharyngeal colonization of respiratory bacteria in HIV infected children is a major public health problem. Single and multiple antibiotic resistant is alarmingly high among respiratory colonizers. Therefore, regular screening of HIV infected children for culture and antimicrobial susceptibility testing is recommended to prevent the development of severe opportunistic infections.

Nasopharyngeal microbiota in infants and changes during viral upper respiratory tract infection and acute otitis media

Background

Interferences between pathogenic bacteria and specific commensals are known. We determined the interactions between nasopharyngeal microbial pathogens and commensals during viral upper respiratory tract infection (URI) and acute otitis media (AOM) in infants.

Methods

We analyzed 971 specimens collected monthly and during URI and AOM episodes from 139 infants. The 16S rRNA V4 gene regions were sequenced on the Illumina MiSeq platform.

Results

Among the high abundant genus-level nasopharyngeal microbiota were Moraxella, Haemophilus, and Streptococcus (3 otopathogen genera), Corynebacterium, Dolosigranulum, Staphylococcus, Acinetobacter, Pseudomonas, and Bifidobacterium. Bacterial diversity was lower in culture-positive samples for Streptococcus pneumoniae, and Haemophilus influenzae, compared to cultured-negative samples. URI frequencies were positively associated with increasing trend in otopathogen colonization. AOM frequencies were associated with decreasing trend in Micrococcus colonization. During URI and AOM, there were increases in abundance of otopathogen genera and decreases in Pseudomonas, Myroides, Yersinia, and Sphingomonas. Otopathogen abundance was increased during symptomatic viral infection, but not during asymptomatic infection. The risk for AOM complicating URI was reduced by increased abundance of Staphylococcus and Sphingobium.

Conclusion

Otopathogen genera played the key roles in URI and AOM occurrences. Staphylococcus counteracts otopathogens thus Staphylococcal colonization may be beneficial, rather than harmful. While Sphingobium may play a role in preventing AOM complicating URI, the commonly used probiotic Bifidobacterium did not play a significant role during URI or AOM. The role of less common commensals in counteracting the deleterious effects of otopathogens requires further studies.

Low prevalence of Kingella kingae carriage in children aged 6-48 months in Sydney, Australia

AIM

A prospective observational study was conducted to estimate the prevalence of oropharyngeal carriage of Kingella kingae in healthy Australian pre-school children.

METHODS

Screening for carriage of K. kingae as well as Streptococcus pyogenes, Streptococcus pneumoniae, Streptococcus agalactiae, Staphylococcus aureus, Haemophilus influenzae, and K. kingae was undertaken using a single bacterial throat swab taken from well children aged 6 months to 4 years. Standard laboratory procedures were used for culture and identification of organisms.

RESULTS

One hundred children were enrolled between October and December 2014 at the Children's Hospital at Westmead. Median age was 24.0 months (range 6.1-48.8 months); 52 children were male and 36 attended day-care facilities. Forty-one children had siblings aged less than 5 years and 67 children had siblings of any age. K. kingae oropharyngeal carriage was not detected in any of the children. Rates of carriage of other organisms were: 30% S. aureus, 21% H. influenzae, 2% S. pneumoniae and 2% S. pyogenes. Thirty-eight children were colonised with Kingella denitrificans.

CONCLUSIONS

Our results suggest that prevalence of K. kingae carriage in pre-school children in Sydney is very low and support local and national guidelines that recommend flucloxacillin as empiric first-line therapy for children with osteoarticular infections. Studies conducted over the winter months and in other Australian centres could help answer outstanding questions regarding differences in carriage rates of K. kingae in children.

Population density profiles of nasopharyngeal carriage of 5 bacterial species in pre-school children measured using quantitative PCR offer potential insights into the dynamics of transmission

Bacterial vaccines can reduce carriage rates. Colonization is usually a binary endpoint. Real time quantitative PCR (qPCR) can quantify bacterial DNA in mucosal samples over a wide range. Using culture and single-gene species-specific qPCRs for Streptococcus pneumoniae (lytA), Streptococcus pyogenes (ntpC), Moraxella catarrhalis (ompJ), Haemophilus influenzae (hdp) and Staphylococcus aureus (nuc) and standard curves against log-phase reference strain broth cultures we described frequency and peak density distributions of carriage in nasopharyngeal swabs from 161 healthy 2-4 y old children collected into STGG broth. In general, detection by qPCR and culture was consistent. Discordance mostly occurred at lower detection thresholds of both methods, although PCR assays for S. pyogenes and S. aureus were less sensitive. Density varied across 5-7 orders of magnitude for the 5 species with the abundant species skewed toward high values (modes: S. pneumoniae log3-4, M. catarrhalis & H. influenzae log4-5 CFU/ml broth). Wide ranges of bacterial DNA concentrations in healthy children carrying these bacteria could mean that different individuals at different times vary greatly in infectiousness. Understanding the host, microbial and environmental determinants of colonization density will permit more accurate prediction of vaccine effectiveness.

Staphylococcus aureus and Streptococcus pneumoniae interaction and response to pneumococcal vaccination: Myth or reality?

S. aureus and S. pneumoniae are both common pathogens that are also carried by a large proportion of healthy individuals in the nasal and nasopharyngeal spaces. A negative association between carriage of S. aureus and S. pneumoniae has been reported in children in various epidemiologic studies from different geographical regions. Most studies found that the negative association between S. pneumoniae and S. aureus was significant only for carriage of vaccine-type S. pneumoniae strains. In this review, we summarize the various suggested mechanisms of this suggested bacterial interference, and the clinical implications reported following PCV introduction to date in various geographical regions.

Impact of Haemophilus influenzae Type B Conjugate Vaccines on Nasopharyngeal Carriage in HIV-infected Children and Their Parents From West Bengal, India

BACKGROUND

In addition to reducing Haemophilus influenzae type b (Hib) disease in vaccinated individuals, the Hib conjugate vaccine (HibCV) has indirect effects; it reduces Hib disease in unvaccinated individuals by decreasing carriage. Human immunodeficiency virus (HIV)-infected children are at increased risk for Hib disease and live in families where multiple members may have HIV. The aim of this study is to look at the impact of 2 doses of the HibCV on nasopharyngeal carriage of Hib in HIV-infected Indian children (2-15 years) and the indirect impact on carriage in their parents.

METHODS

This prospective cohort study was conducted in HIV-infected and HIV-uninfected families. Nasopharyngeal swabs were collected from children and parents before and after vaccination. HIV-infected children 2-15 years of age got two doses of HibCV and were followed up for 20 months. Uninfected children 2-5 years of age got 1 dose of HibCV as catch-up.

RESULTS

123 HIV-infected and 44 HIV-uninfected children participated. Baseline colonization in HIV-infected children was 13.8% and dropped to 1.8% (P = 0.002) at 20 months. Baseline carriage in HIV-uninfected children was 4.5% and dropped to 2.3% after vaccination (P = 0.3). HIV-infected parents had 12.3 times increased risk of Hib carriage if their child was colonized (P = 0.04) and had 9.3 times increased risk if their child had persistent colonization postvaccine (P = 0.05). No parent of HIV-uninfected children had Hib colonization at any point. Pneumococcal colonization was associated with increased Hib colonization.

CONCLUSION

Making the HibCV available to HIV-infected children could interrupt Hib carriage in high-risk families.

Streptococcus pneumoniae Colonization Disrupts the Microbial Community within the Upper Respiratory Tract of Aging Mice

Nasopharyngeal colonization by the Gram-positive bacterium Streptococcus pneumonia is a prerequisite for pneumonia and invasive pneumococcal diseases. Colonization is asymptomatic, involving dynamic and complex interplay between commensals, the host immune system, and environmental factors. The elderly are at an increased risk of developing pneumonia, which might be due to changes in the respiratory microbiota that would impact bacterial colonization and persistence within this niche. We hypothesized that the composition of the upper respiratory tract (URT) microbiota changes with age and subsequently can contribute to sustained colonization and inefficient clearance of S. pneumoniae To test this, we used a mouse model of pneumococcal colonization to compare the composition of the URT microbiota in young, middle-aged, and old mice in the naive state and during the course of colonization using nasal pharyngeal washes. Sequencing of variable region 3 (V3) of the 16S rRNA gene was used to identify changes occurring with age and throughout the course of S. pneumonia colonization. We discovered that age affects the composition of the URT microbiota and that colonization with S. pneumoniae is more disruptive of preexisting communities in older mice. We have further shown that host-pathogen interactions followingS. pneumonia colonization can impact the populations of resident microbes, including Staphylococcus and Haemophilus. Together, our findings indicate alterations to the URT microbiota could be detrimental to the elderly, resulting in increased colonization of S. pneumonia and decreased efficiency in its clearance.

High genetic diversity of Staphylococcus aureus strains colonising the nasopharynx of Gambian villagers before widespread use of pneumococcal conjugate vaccines

Background

With the global efforts of reducing pneumococcal disease through widespread introduction of pneumococcal vaccines, concerns have emerged on the potential increase of morbidity and mortality from S. aureus disease. Little is known however, of the carriage rates of S. aureus or of its’ relationship with carriage of S. pneumoniae in rural Africa, and West Africa in particular where very high rates of carriage of S. pneumoniae have been reported. This study aims to evaluate the prevalence, antibiotic susceptibility patterns and genotypes of S. aureus isolated from the nasopharynx of healthy individuals in rural Gambia before the introduction of routine use of pneumococcal conjugate vaccines in the country.

Results

Overall prevalence of S. aureus nasopharyngeal carriage was 25.2 %. All S. aureus isolates tested were susceptible to methicillin. Resistant was observed for sulphamethoxazole-trimethoprim (15 %) and tetracycline (34.3 %). We found 59 different sequence types (ST), 35 of which were novel. The most prevalent sequence types were ST 15 (28 %) and ST 5 (4 %). Eighty two percent (494/600) of study individuals were S. pneumoniae carriers with S. pneumoniae carriage rates decreasing with increasing age groups. S. aureus carriage among pneumococcal carriers was slightly lower than among non-pneumococcal carriers (24.3 versus 29.3 %; p = 0.324). There were no associations of carriage between these two bacteria across the 4 age groups. However, analysis of pooled data children < 2 years and children 2 to < 5 years of age showed a statistically significant inverse association (24.1 and 50.0 % for S. aureus carriage among S. pneumoniae carriers and non-carriers respectively; p = 0.015).

Conclusions

We report that nasopharyngeal carriage of S. aureus in rural Gambia is high in all age groups, with approximately 1 out of 4 individuals being carriers in the pre-pneumococcal vaccination era. There are indications that nasopharyngeal carriage of S.aureus could be inversely related to carriage of S. pneumoniae amongst younger children in The Gambian and that S. aureus clones in The Gambia show significant genetic diversity suggesting worldwide dissemination. Findings from this study provide a useful background for impact studies evaluating the introduction of pneumococcal vaccines or other interventions targeting the control of S. aureus infections and disease.

The role of respiratory viruses in the etiology of bacterial pneumonia: An ecological perspective

Pneumonia is the leading cause of death among children less than 5 years old worldwide. A wide range of viral, bacterial and fungal agents can cause pneumonia: although viruses are the most common etiologic agent, the severity of clinical symptoms associated with bacterial pneumonia and increasing antibiotic resistance makes bacterial pneumonia a major public health concern. Bacterial pneumonia can follow upper respiratory viral infection and complicate lower respiratory viral infection. Secondary bacterial pneumonia is a major cause of influenza-related deaths. In this review, we evaluate the following hypotheses: (i) respiratory viruses influence the etiology of pneumonia by altering bacterial community structure in the upper respiratory tract (URT) and (ii) respiratory viruses promote or inhibit colonization of the lower respiratory tract (LRT) by certain bacterial species residing in the URT. We conducted a systematic review of the literature to examine temporal associations between respiratory viruses and bacteria and a targeted review to identify potential mechanisms of interactions. We conclude that viruses both alter the bacterial community in the URT and promote bacterial colonization of the LRT. However, it is uncertain whether changes in the URT bacterial community play a substantial role in pneumonia etiology. The exception is Streptococcus pneumoniae where a strong link between viral co-infection, increased carriage and pneumococcal pneumonia has been established.

Nasopharyngeal colonization of Gambian infants by Staphylococcus aureus and Streptococcus pneumoniae before the introduction of pneumococcal conjugate vaccines

Staphylococcus aureus and Streptococcus pneumoniae commonly colonize the upper respiratory tract and can cause invasive disease. Several studies suggest an inverse relationship between these two bacteria in the nasopharynx. This association is of particular concern as the introduction of pneumococcal conjugate vaccines (PCVs) that affect pneumococcal nasopharyngeal carriage become widespread. A cohort of children in rural Gambia were recruited at birth and followed for 1 year, before the introduction of PCV into the routine immunization program. Nasopharyngeal swabs were taken immediately after birth, every 2 weeks for the first 6 months and then every other month. The presence of S. aureus and S. pneumoniae was determined using conventional microbiologic methods. Prevalence of S. aureus carriage was 71.6% at birth, decreasing with age to reach a plateau at approximately 20% between 10 to 20 weeks of age. Carriage with any S. pneumoniae increased during the first 10 weeks of life to peak at approximately 90%, mostly of PCV13 serotypes. Although in the crude analysis S. aureus carriage was inversely associated with carriage of any S. pneumoniae and PCV13 serotypes, after adjusting by age and season, there was a positive association with any carriage (odds ratio 1.32; 95% confidence interval 1.07-1.64; p 0.009) and no association with carriage of PCV13 serotypes (odds ratio 0.99; 95% confidence interval 0.70-1.41; p 0.973). Among Gambian infants, S. aureus and S. pneumoniae are not inversely associated in nasopharyngeal carriage after adjustment for age. Further carriage studies following the introduction of PCV are needed to better understand the relationship between the two bacteria.

Associations Between Viral and Bacterial Potential Pathogens in the Nasopharynx of Children With and Without Respiratory Symptoms

BACKGROUND

Nasopharyngeal (NP) bacterial colonization is necessary for subsequent respiratory and/or invasive infection. Our study aimed at comparing NP bacterial colonization rates between children with and without symptoms of an acute viral respiratory tract infection and examining associations between identified microorganisms.

METHODS

Children 3 months to 6 years of age with and without an acute viral respiratory tract infection were recruited, and a questionnaire was filled. NP samples were examined for Streptococcus pneumoniae (SP), Haemophilus influenzae (HI), Moraxella catarrhalis (MC), Staphylococcus aureus and Streptococcus pyogenes by culture. Viruses were detected with polymerase chain reaction.

RESULTS

Median age of the 386 recruited children was 23.4 months, and 127 had no respiratory symptoms. More asymptomatic subjects were found negative for all bacteria tested (P < 0.01). SP (P < 0.01), MC (P = 0.001) and mixed bacterial colonization patterns were more frequent among symptomatic children (P < 0.05). Colonization of symptomatic, virus-positive children with MC was higher than in asymptomatic and/or virus-negative children (P = 0.005). The highest HI and MC colonization rates were recorded in association with influenza virus. A strongly negative association between SP and S. aureus, a higher rate of HI detection among SP colonized children and an increased likelihood of MC detection in the presence of HI were observed. HI colonization was more likely in the presence of respiratory syncytial virus and MC colonization was associated with rhinovirus detection.

CONCLUSIONS

Viruses are associated with different NP bacterial colonization patterns. Observed pathogens' associations may play a role in disease, and continuous surveillance is required to follow possible effects of interventions such as vaccines.

Factors Affecting Staphylococcus aureus Colonization of the Nasopharynx in the First 6 Months of Life

BACKGROUND

Staphylococcal aureus (SA) colonization in early infancy is common, but the pattern and factors affecting its acquisition and persistence in the first few months of life are not well studied. The aim is to study the rate of SA nasopharyngeal (NP) colonization at monthly intervals in the first 6 months of life and its association with environmental and host factors and other pathogenic NP bacteria.

METHODS

Data from a prospective study were analyzed on bacterial cultures of 1765 NP swabs from 367 infants who were followed from birth to 6 months of age. Demographic, breastfeeding, cigarette smoke exposure and day care attendance data were collected at each monthly visit.

RESULTS

The rate of infants colonized with SA was highest at age 1 month (25%) and declined to lowest rate by age 6 months (12%). The proportion of SA strains that was methicillin-resistant SA was also highest at age 1 month and declined rapidly by age 4 months (18% vs. 6%, P = 0.05). Colonization with Streptococcus pneumoniae (SP), nontypeable Haemophilus influenzae (NTHI) and Moraxella catarrhalis (MC) increased at different rates up to age 6 months. Univariate analysis showed that SA colonization rate was significantly lower with increasing age, black race, day care attendance, and colonization with NTHI, MC and SP (P < 0.05). Multivariate analysis showed that this effect was independently associated only with increasing age and MC colonization (P < 0.05). Furthermore, the time to first acquisition of SA from one month of age onwards was significantly associated with day care attendance, and NTHI and MC colonization. None of the infants colonized with SA developed SA infections through age 6 months.

CONCLUSIONS

SA colonization of NP begins very early in life and declines quickly. Methicillin-resistant SA has lower ability to maintain prolonged colonization status than methicillin-susceptible strains in the first 6 months of life. As the NP is colonized with other respiratory bacterial pathogens, the colonization with SA declines; however, this effect is stronger with Gram-negative bacteria, such as NTHI and MC.

Longitudinal study on Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus nasopharyngeal colonization in HIV-infected and -uninfected infants vaccinated with pneumococcal conjugate vaccine

BACKGROUND

Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus are all potentially pathogenic, which frequently colonize the nasopharynx (NP) prior to causing disease. We studied bacterial NP-colonization in 321 HIV-infected and 243 HIV-uninfected children vaccinated with 7-valent pneumococcal conjugate vaccine (PCV7) at 6, 10 and 14 weeks of age.

METHODS

HIV-uninfected infants included those born to HIV-uninfected (HUU) and HIV-infected women (HEU); HIV-infected children with CD4+ lymphocyte ≥25% were randomized to initiate antiretroviral therapy immediately (ART-Immed) or when clinically indicated (ART-Def). Nasopharyngeal swabs for bacterial culture were taken prior to each PCV7 dose (Visits 1-3) and at 20, 39, 47 and 67 weeks of age (Visits 4-7). Swabs were cultured by standard methods and pneumococcal serotyping done by the Quellung method.

RESULTS

Colonization patterns for pneumococcus, H. influenzae and S. aureus did not differ between HUU and HEU children; and were also generally similar between ART-Def and ART-Immed children. Prevalence of PCV7-serotype colonization was similar between HIV-infected and HIV-uninfected children, however, overall pneumococcal and specifically non-vaccine serotype colonization tended to be lower in HIV-infected children. HIV-infected children also had a 44% lower prevalence of S. aureus colonization at Visit-1 (p=0.010); and H. influenzae colonization was also lower among HIV-infected than HIV-uninfected children at Visit-2, Visit-3, Visit-6 and Visit-7.

CONCLUSION

Vaccine-serotype colonization is similar in PCV-immunized HIV-infected and HIV-uninfected children. We, however, identified a lower prevalence of overall-pneumococcal and H. influenzae colonization in HIV-infected children post-PCV vaccination, the clinical-relevance of which warrants further study.

Haemophilus influenzae: recent advances in the understanding of molecular pathogenesis and polymicrobial infections

PURPOSE OF REVIEW

Non-typeable Haemophilus influenzae (NTHi) is a human-specific mucosal pathogen and one of the most common causes of bacterial infections in children and patients with chronic obstructive pulmonary disease. It is also frequently found in polymicrobial superinfections. Great strides have recently been made in the understanding of the molecular mechanisms underlying NTHi pathogenesis.

RECENT FINDINGS

By using new methodology, such as experimental human colonization models and whole-genome approaches, investigators have shed light upon the various strategies of NTHi that are involved in pathogenesis. These include the escape of the mucociliary elevator, evasion of host immunity, survival in environments with scarce nutrients, and finally participation in polymicrobial infections. Lipooligosaccharide branching, proteinous adhesins, metabolic adaption to nutrient availability and many scavenging systems are implicated in these processes. Interestingly, genome-based studies comparing virulent and commensal strains have identified many hypothetical proteins as virulence determinants, suggesting that much regarding the molecular pathogenesis of NTHi remains to be solved.

SUMMARY

NTHi is an opportunistic pathogen and highly specialized colonizer of the human respiratory tract that has developed intricate mechanisms to establish growth and survival in the human host. Continued research is needed to further elucidate NTHi host-pathogen and pathogen-pathogen interactions.

Acquisition of Streptococcus pneumoniae in South African children vaccinated with 7-valent pneumococcal conjugate vaccine at 6, 14 and 40 weeks of age

BACKGROUND

Seven-valent pneumococcal conjugate vaccine (PCV7) was introduced into the South African immunization program using 6, 14 and 40 weeks dosing schedule (2+1), with no catch-up in older children since April 2009. We investigated pneumococcal colonization acquisition in children who received this schedule and also compared it to historical cohorts of PCV-naïve children (n=123 in 2007) and children who received a 3+1 PCV7 schedule (n=124 in 2005/06).

METHODS

Two hundred and fifty children aged 6-12 weeks were enrolled from December 2009 to April 2010. Participants had nasopharyngeal swabs collected on eight occasions between enrolment and 2-years of age. Standard methods were undertaken for bacterial culture and Streptococcus pneumoniae were serotyped using the Quellung method. Pneumococcal and Staphylococcus aureus colonization in the present study was compared to colonization in two historical longitudinal cohorts.

RESULTS

S. pneumoniae was identified in 1081 (61.4%) of 1761 swabs collected in the current cohort. Pneumococcal colonization peaked at 41-weeks of age (76.8%) and decreased to 62.8% by 2-years of age (p=0.002); PCV7-serotype colonization decreased during the same period from 28.6% to 15.6% (p=0.001). Children from the current cohort compared to PCV-naïve children were less likely to be colonized by PCV7-serotypes from 40-weeks to 2-years of age and acquired PCV7-serotypes less frequently. No differences in overall pneumococcal, PCV7-serotype and non-PCV7-serotype colonization or new serotype acquisitions were detected comparing the current cohort to the historical cohort who received the 3+1 PCV7 schedule. Staphylococcus aureus colonization was similar in all three cohorts.

CONCLUSION

A 2+1 PCV7 schedule implemented in South Africa was temporally associated with reduced risk of vaccine-serotype colonization compared to historically unvaccinated children. Also, vaccine-serotype acquisition rate using the 2+1 schedule was similar to that in the 3+1 dosing cohort, suggesting that similar indirect protection against pneumococcal disease could be derived from either schedule in South Africa.

Staphylococcus aureus manganese transport protein C (MntC) is an extracellular matrix- and plasminogen-binding protein

Infections caused by Staphylococcus aureus – particularly nosocomial infections - represent a great concern. Usually, the early stage of pathogenesis consists on asymptomatic nasopharynx colonization, which could result in dissemination to other mucosal niches or invasion of sterile sites, such as blood. This pathogenic route depends on scavenging of nutrients as well as binding to and disrupting extracellular matrix (ECM). Manganese transport protein C (MntC), a conserved manganese-binding protein, takes part in this infectious scenario as an ion-scavenging factor and surprisingly as an ECM and coagulation cascade binding protein, as revealed in this work. This study showed a marked ability of MntC to bind to several ECM and coagulation cascade components, including laminin, collagen type IV, cellular and plasma fibronectin, plasminogen and fibrinogen by ELISA. The MntC binding to plasminogen appears to be related to the presence of surface-exposed lysines, since previous incubation with an analogue of lysine residue, ε-aminocaproic acid, or increasing ionic strength affected the interaction between MntC and plasminogen. MntC-bound plasminogen was converted to active plasmin in the presence of urokinase plasminogen activator (uPA). The newly released plasmin, in turn, acted in the cleavage of the α and β chains of fibrinogen. In conclusion, we describe a novel function for MntC that may help staphylococcal mucosal colonization and establishment of invasive disease, through the interaction with ECM and coagulation cascade host proteins. These data suggest that this potential virulence factor could be an adequate candidate to compose an anti-staphylococcal human vaccine formulation.