Host-dependent resistance of Group A Streptococcus to sulfamethoxazole mediated by a horizontally-acquired reduced folate transporter.

Described antimicrobial resistance mechanisms enable bacteria to avoid the direct effects of antibiotics and can be monitored by in vitro susceptibility testing and genetic methods. Here we describe a mechanism of sulfamethoxazole resistance that requires a host metabolite for activity. Using a combination of in vitro evolution and metabolic rescue experiments, we identify an energy-coupling factor (ECF) transporter S component gene (thfT) that enables Group A Streptococcus to acquire extracellular reduced folate compounds. ThfT likely expands the substrate specificity of an endogenous ECF transporter to acquire reduced folate compounds directly from the host, thereby bypassing the inhibition of folate biosynthesis by sulfamethoxazole. As such, ThfT is a functional equivalent of eukaryotic folate uptake pathways that confers very high levels of resistance to sulfamethoxazole, yet remains undetectable when Group A Streptococcus is grown in the absence of reduced folates. Our study highlights the need to understand how antibiotic susceptibility of pathogens might function during infections to identify additional mechanisms of resistance and reduce ineffective antibiotic use and treatment failures, which in turn further contribute to the spread of antimicrobial resistance genes amongst bacterial pathogens.

Lung abscess: 14 years of experience in a tertiary paediatric hospital.

BACKGROUND: Lung abscess is a rare condition in paediatrics with a paucity of literature. Intravenous antibiotics is the main therapy; however interventional radiological approaches have led to the use of percutaneous drainage. Surgery is reserved for the management of complications. The aim of this study was to describe lung abscess in a cohort of paediatric patients' and determine associations between factors at presentation and outcomes. METHODS: A 14-year retrospective cohort study was conducted including all children who presented to a tertiary paediatric hospital in Western Australia with lung abscess. Clinical characteristics, laboratory and radiologic findings, management options and clinical outcomes were examined. RESULTS: Sixty-eight patients (median age 3.6 (0.08-17.6) years; 44.1% female) were identified to have a lung abscess, with 81% being primary lung abscess. Staphylococcus aureus (including MRSA) and Streptococcus pneumoniae were the most common organisms identified, with S. aureus being most common in Aboriginal patients (80%). A total of 25 antibiotics were prescribed on initiation of treatment in over 20 combinations. 44.9% of patients had complications and hospitalization was prolonged. Patients with S. aureus had longer hospitalization (20.5 days (3-67) than those without (median 13 days (3-52), p = 0.04). There were no associations between factors at presentation and subsequent outcomes. Factors at presentation were not associated with outcomes. CONCLUSION: There is unwarranted variation in management of paediatric lung abscess and high complication rates. There is a need for collaboration and clinical practice guidelines to standardize care for lung abscess in children.

Increased nasal Streptococcus pneumoniae presence in Western environment associated with allergic conditions in Chinese immigrants.

BACKGROUND: Chinese immigrants living in Australia experience increased allergic conditions: asthma, eczema, hay fever and wheeze. Recently we reported diminished innate cytokine responses in long-term immigrants, potentially increasing their pathogenic viral load and microbial carriage. We hypothesise that a Western environment changes the nasal microbiome profile, and this altered profile may be associated with the development of allergic conditions. In this cross-sectional study, we aimed to examine the loading of viral and microbial respiratory pathogens in the upper airway. METHODS: Adult Chinese immigrants were grouped depending on time spent in Australia: short-term (<6 years) or long-term (≥6 years). First, age- and gender-matched immigrants were selected for an initial screen using quantitative polymerase chain reaction (qPCR) micro-array panels. Then based on initial results the viruses, human parainfluenza 3 and rhinovirus, and the bacteria, Burkholderia spp., Staphylococcus aureus and Streptococcus pneumoniae, were validated using qPCR in the population. Associations for bacterial prevalence with atopic phenotypes were investigated. RESULTS: Pooling the initial screen and validation subjects, S. aureus and S. pneumoniae had higher prevalence in long-term compared with short-term subjects (25.0% vs 8.1%, P = 0.012; and 76.8% vs 48.4%, P = 0.002). Those immigrants with nasal S. pneumoniae presence resided longer (average time 90.4 months) in Australia than immigrants without S. pneumoniae (52.7 months; P = 0.001). After adjusting for confounders, Chinese immigrants with S. pneumoniae carriage have a five-fold increased risk of doctor-diagnosed eczema (odds ratio, OR 5.36, 95% CI: 1.10-26.14; P = 0.038) compared to immigrants without S. pneumoniae carriage. There was a trend of S. pneumoniae abundance correlating with reduced host Toll-like receptor gene expression. CONCLUSION: Our findings suggest that nasal S. pneumoniae may play a role in the development of allergic conditions in Chinese immigrants in a Western environment.

Linking the westernised oropharyngeal microbiome to the immune response in Chinese immigrants.

BACKGROUND: Human microbiota plays a fundamental role in modulating the immune response. Western environment and lifestyle are envisaged to alter the human microbiota with a new microbiome profile established in Chinese immigrants, which fails to prime the immune system. Here, we investigated how differences in composition of oropharyngeal microbiome may contribute to patterns of interaction between the microbiome and immune system in Chinese immigrants living in Australia. METHODS: We recruited 44 adult Chinese immigrants: newly-arrived (n = 22, living in Australia < 6 months) and long-term Chinese immigrants (n = 22, living in Australia > 5 years), with age and gender matched. Oropharyngeal swabs, serum and whole blood were collected. The 16 s ribosomal RNA gene from the swabs was sequenced on the Illumina MiSeq platform. Innate immune responses were determined by 23 Toll-like receptors (TLR) pathway cytokines, while adaptive immune responses were determined by IgG-associated response to specific microbial/viral pathogens. RESULTS: The relative abundance of the genus Leptotrichia was higher in long-term immigrants as compared to that in newly-arrived Chinese immigrants, while the genus Deinococcus was significantly lower in long-term Chinese immigrants. The genera uncultured Lachnospiraceae, Erysipelotrichaceae UCG-007, Veillonella, and Actinomycetales_ambiguous taxa were negatively correlated with cytokine IL-6 in long-term Chinese immigrants (rho range: - 0.46 ~ - 0.73). With respect to adaptive immunity, several microbial taxa were significantly associated with IgG1 responsiveness to microbial antigens in long-term immigrants, while a significant correlation with IgG1 responsiveness to viral antigens was detected in newly-arrived immigrants. CONCLUSIONS: The composition of the oropharyngeal microbiome varies between newly-arrived and long-term Chinese immigrants. Specific microbial taxa are significantly associated with immunological parameters but with different association patterns between newly-arrived and long-term Chinese immigrants.

Western oropharyngeal and gut microbial profiles are associated with allergic conditions in Chinese immigrant children.

BACKGROUND: The allergy epidemic resulting from western environment/lifestyles is potentially due to modifications of the human microbiome. Therefore, it is of interest to study immigrants living in a western environment as well as their counterparts in the country of origin to understand differences in their microbiomes and health status. METHODS: We investigated 58 Australian Chinese (AC) children from Perth, Western Australia as well as 63 Chinese-born Chinese (CC) children from a city in China. Oropharyngeal (OP) and fecal samples were collected. To assess the microbiomes, 16s ribosomal RNA (rRNA) sequencing for variable regions V3 and V4 was used. Skin prick tests (SPT) were performed to measure the children's atopic status. Information on food allergy and wheezing were acquired from a questionnaire. RESULTS: AC children had more allergic conditions than CC children. The alpha diversity (mean species diversity) of both OP and gut microbiome was lower in AC children compared to CC children for richness estimate (Chao1), while diversity evenness (Shannon index) was higher. The beta diversity (community similarity) displayed a distinct separation of the OP and gut microbiota between AC and CC children. An apparent difference in microbial abundance was observed for many bacteria. In AC children, we sought to establish consistent trends in bacterial relative abundance that are either higher or lower in AC versus CC children and higher or lower in children with allergy versus those without allergy. The majority of OP taxa showed a consistent trend while the majority of fecal taxa showed a contrasting trend. CONCLUSION: Distinct differences in microbiome compositions were found in both oropharyngeal and fecal samples of AC and CC children. The association of the OP microbiome with allergic condition is different from that of the gut microbiome in AC children. The microbiome profiles are changed by the western environment/lifestyle and are associated with allergies in Chinese immigrant children in Australia.