Human Carriage Research Articles

Anthropogenic and environmental factors associated with high incidence of mcr-1 carriage in humans across China.

Introductory ParagraphMCR-1-positve E. coli (MCRPEC) have been reported in human worldwide; however, thus far it’s prevalence is low and potential sources for human mcr-1 carriage have not yet been identified. Herein, we analysed a nationwide epidemiological data set on MCRPEC in humans throughout China and assessed factors associated with MCRPEC carriage using natural and national anthropogenic data. We identified 774 non-duplicate MCRPEC isolates from 774 stool samples collected from 5,159 healthy individuals in 30 provinces/municipalities in 2016, with a prevalence of MCRPEC ranging from 3.7% to 32.7% (average of 15.0%), substantially higher than previously reported. MCRPEC carriage was associated with provincial regions, production of sheep and freshwater aquaculture, annual consumption of total meat, pork and mutton, and daily intake of aquaculture products. MCRPEC was significantly more prevalent in provinces with higher aquaculture industries. WGS analysis revealed that the MCRPEC isolates were clustered into four distinct lineages, two of which were dominant and harbored most of the MCRPEC isolates. The high prevalence of MCRPEC in community poses a substantial risk for colistin usage in clinical practice and suggests the need for intestinal screening of mcr-1 carriers in intensive care units in Chinese hospitals. Furthermore, our data suggests that aquaculture is a significant reservoir of mcr-1.

Mannitol-fermenting methicillin-resistant staphylococci (MRS) in pig abattoirs in Cameroon and South Africa: A serious food safety threat

Food animals can be reservoirs of methicillin-resistant staphylococci (MRS) and are involved in their zoonotic transmission through the food chain. In Africa, there is a dearth of information about the food safety issues associated with their dissemination in the farm-to-plate continuum. This study sought to determine and compare the carriage, antimicrobial resistance profiles and clonal relatedness of circulating MRS strains among pigs and exposed workers in Cameroon and South Africa.A total of 288 nasal and rectal pooled samples collected from 432 pigs as well as nasal and hand swabs from 82 humans were cultured on mannitol salt agar supplemented with 6 mg/l cefoxitin. Presumptive MRS were screened for methicillin resistance using the cefoxitin disc test and confirmed with the VITEK 2 system. Selected isolates underwent genomic fingerprinting via REP-PCR. Univariate and multivariate logistic regression analyses were performed to identify risk factors for MRS carriage in humans from a questionnaire survey among slaughterhouse workers.Overall, 75% and 70% of nasal and rectal pooled samples were respectively positive for MRS. The MRS prevalence in all pooled pig samples from Cameroon was higher than that of South Africa. MRS prevalence of carriage (nasal and hand) was higher in Cameroonian exposed workers compared to those from South Africa, with high statistical significance. Nasal MRS colonization was highly statistically associated with hand MRS (31.58% vs 86.21%; p = 0.000; OR = 13.54; 95% CI 3.99–45.95; p = 0.015). Recent antibiotic use, previous hospitalization, occupation of relatives, years in the employment and contact with poultry were the main risk factors identified in the emergence and spread of MRS.MRS are emerging as serious foodborne pathogens and present a food safety threat. There is an urgent need to implement stringent and effective prevention and containment measures to curb antibiotic resistance in the farm-to-plate continuum in Cameroon and South Africa.

Development of a New Application for Comprehensive Viability Analysis Based on Microbiome Analysis by Next-Generation Sequencing: Insights into Staphylococcal Carriage in Human Nasal Cavities.

The nasal carriage rate of Staphylococcus aureus in human is 25 to 30%, and S. aureus sporadically causes severe infections. However, the mechanisms underlying staphylococcal carriage remain largely unknown. In the present study, we constructed an rpoB-based microbiome method for staphylococcal species discrimination. Based on a microbiome scheme targeting viable cell DNA using propidium monoazide (PMA) dye (PMA microbiome method), we also developed a new method to allow the comprehensive viability analysis of any bacterial taxon. To clarify the ecological distribution of staphylococci in the nasal microbiota, we applied these methods in 46 nasal specimens from healthy adults. PMA microbiome results showed that Staphylococcaceae and Corynebacteriaceae were the most predominant viable taxa (average relative abundance: 0.435262 and 0.375195, respectively), and Staphylococcus epidermidis exhibited the highest viability in the nasal microbiota. Staphylococcus aureus detection rates from nasal specimens by rpoB-based conventional and PMA microbiome methods were 84.8% (39 of 46) and 69.5% (32 of 46), respectively, which substantially exceeded the values obtained by a culture method using identical specimens (36.9%). Our results suggest that Staphylococcaceae species, especially S. epidermidis, adapted most successfully to human nasal cavity. High detection of S. aureus DNA by microbiome methods suggests that almost all healthy adults are consistently exposed to S. aureus in everyday life. Furthermore, the large difference in S. aureus detection rates between culture and microbiome methods suggests that S. aureus cells frequently exist in a viable but nonculturable state in nasal cavities. Our method and findings will contribute to a better understanding of the mechanisms underlying carriage of indigenous bacteria.IMPORTANCE Metagenomic analyses, such as 16S rRNA microbiome methods, have provided new insights in various research fields. However, conventional 16S rRNA microbiome methods do not permit taxonomic analysis of only the viable bacteria in a sample and have poor resolving power below the genus level. Our new schemes allowed for viable cell-specific analysis and species discrimination, and nasal microbiome data using these methods provided some interesting findings regarding staphylococcal nasal carriage. According to our comprehensive viability analysis, the high viability of Staphylococcus species, especially Staphylococcus epidermidis, in human nasal carriage suggests that this taxon has adapted most successfully to human nasal tissue. Also, a higher detection rate of S. aureus DNA by microbiome methods (84.8%) than by a culture method (36.9%) suggests that almost all healthy adults are consistently exposed to Staphylococcus aureus in the medium and long term. Our findings will contribute to a better understanding of the mechanisms underlying the carriage of indigenous bacteria.

Evaluation of the pig-tailed macaque (Macaca nemestrina) as a model of human Staphylococcus aureus nasal carriage

Abstract Staphylococcus aureus (SA) nasal carriage is a common condition effecting both healthy and immunocompromised populations, and provides a reservoir for dissemination of potentially infectious strains by casual contact. Factors regulating the onset and duration of nasal SA colonization are mostly unknown, and a human-relevant animal model is needed. Here, we screened 17 pig-tailed macaques (Macaca nemestrina) for SA carriage, and 14 of 17 animals tested positive in the nose at one or both screening sessions (8 weeks apart), while the other three animals were negative in the nose but positive in the pharynx at least once. Similar to humans, SA colonization was densest in the nose, and treatment of the nostrils with mupirocin ointment effectively cleared the nostrils and 6 extra-nasal body sites. Experimental nasal SA colonization was established with 104 CFU/nostril, and both autologous and non-autologous strains survived over 40 days without any apparent adverse effects. A human nasal SA isolate (D579/ST398) was carried in 4 of 6 animals for over three weeks. Nostrils that did eradicate experimentally applied SA exhibited neutrophilic innate immunity marked by elevated nasal IL-1β, IL-8, and MCP-1, and a 10-fold decreased IL-1RA:IL-1β ratio within 7 days post-inoculation, analogous to the human condition. Taken together, pig-tailed macaques represent a physiological model of human SA nasal carriage with utility for testing natural colonization and decolonization mechanisms, and novel classes of anti-SA therapeutics.

Listeria

Listeria

Prospective study on human fecal carriage of Enterobacteriaceae possessing mcr-1 and mcr-2 genes in a regional hospital in Hong Kong

BackgroundHuman fecal carriage of Enterobacteriaceae possessing mobilized colistin resistance genes (mcr-1 and mcr-2) remains obscure in Hong Kong. As part of routine surveillance on emerging antibiotic resistance, we conducted a prospective study on this topic in a regional hospital in Hong Kong.MethodsFrom October 31 to November 25, 2016, all fecal specimens submitted for routine analysis were included in this surveillance study. These comprised 672 consecutive routine fecal specimens collected from 616 individuals. Fecal specimens were screened for colistin-resistant Enterobacteriaceae by culture-based method, and the presence of mcr-1 and mcr-2 genes in resistant isolates was identified by polymerase chain reaction and Sanger sequencing. Whole genome sequencing (WGS) of mcr-1-possessing Escherichia coli strains was facilitated using Illumina® MiSeq® followed by sequence analysis with appropriate bioinformatics tools.ResultsFourteen mcr-1-positive E. coli strains were isolated from 14 separate individuals (2.08% of total fecal specimens), with 9 of them being asymptomatic, healthy clients coming for health assessment. No mcr-2-possessing Enterobacteriaceae was identified. Colistin minimum inhibitory concentrations of these mcr-1-positive isolates ranged from 2 to 4 μg/mL. All these isolates were susceptible to carbapenems with 2 being extended spectrum β-lactamase producers. WGS data revealed that these isolates belonged to at least 12 different sequence types (STs) and possessed diversified plasmid replicons, virulence and acquired antibiotic resistance genes. Further study on an E. coli ST201 strain (Pasteur scheme) revealed coexistence of 47,818-bp IncP-1 and 33,309-bp IncX4 types of mcr-1 plasmids, which was a combination of stability and high transmissibility.ConclusionsTo the best of our knowledge, this is the first study on human fecal carriage of Enterobacteriaceae possessing mcr-1 and mcr-2 genes in Hong Kong. Our data further revealed asymptomatic carriage of mcr-1-possessing Enterobacteriaceae by both patients and healthy individuals. This is alarming considering wide diversity and high transmissibility of mcr-1 plasmids, which potentially facilitate emergence of pan-drug-resistant bacteria in future infection. This also highlights the importance of surveillance on emerging antibiotic resistance, especially for patients under intensive care.

High prevalence of ESBL-Producing E. coli in private and shared latrines in an informal urban settlement in Dar es Salaam, Tanzania

BackgroundData about the burden of extended-spectrum beta-lactamase (ESBL)-producing microorganisms in Africa are limited. Our study aimed to estimate the prevalence of human faecal ESBL carriage in the community of an informal urban settlement in Dar es Salaam (Tanzania, East Africa) by using environmental contamination of household latrines with ESBL as a surrogate marker.MethodsWithin the context of a large survey in February 2014 assessing 636 randomly selected household latrines for faecal contamination by the detection of growth of E. coli and total faecal coliform bacteria, a randomly selected subset of the samples were screened for ESBL.ResultsSeventy latrines were screened for ESBL. An average of 11.4 persons (SD ±6.5) were sharing one latrine. Only three (4.3%) latrines had hand-washing facilities and 50 showed faeces on the floor. ESBL-producing Enterobacteriaceae were confirmed in 17 (24.3%) of the 70 latrine samples: 16 E. coli and 1 Klebsiella pneumoniae. Five ESBL E. coli strains were detected on door handles. The most prevalent ESBL type was CTX-M-1 group (76.5%). Pulsed-field gel electrophoresis typing of a subset of ESBL-producing E. coli isolates revealed both diverse singular types and a cluster of 3 identical isolates. There was no significant difference of the latrine and household characteristics between the group with ESBL (n = 17) and the group with non-ESBL E. coli (n = 53) (p > 0.05).ConclusionsAlmost a quarter of private and shared latrines in an informal urban settlement in Tanzania are contaminated with ESBL-producing microorganisms, suggesting a high prevalence of human ESBL faecal carriage in the community. Shared latrines may serve as a reservoir for transmission in urban community settings in Tanzania.

Selection of ESBL-Producing E. coli in a Mouse Intestinal Colonization Model.

Asymptomatic human carriage of antimicrobially drug-resistant pathogens prior to infection is increasing worldwide. Further investigation into the role of this fecal reservoir is important for combatting the increasing antimicrobial resistance problems. Additionally, the damage on the intestinal microflora due to antimicrobial treatment is still not fully understood. Animal models are powerful tools to investigate bacterial colonization subsequent to antibiotic treatment. In this chapter we present a mouse-intestinal colonization model designed to investigate how antibiotics select for an ESBL-producing E. coli isolate. The model can be used to study how antibiotics with varying effect on the intestinal flora promote the establishment of the multidrug-resistant E. coli. Colonization is successfully investigated by sampling and culturing stool during the days following administration of antibiotics. Following culturing, a precise identification of the bacterial strain found in mice feces is applied to ensure that the isolate found is in fact identical to the strain used for inoculation. For this purpose random amplified of polymorphic DNA (RAPD) PCR specifically developed for E. coli is applied. This method allows us to distinguish E. coli with more than 99.95% genome similarity using a duplex PCR method.

Intestinal carriage of ampicillin- and vancomycin-resistant Enterococcus faecium in humans, dogs and cats in the Netherlands.

The prevalence of ampicillin- and/or vancomycin-resistant Enterococcus faecium (AREf and VREf) has increased in hospitalized patients in the Netherlands. To quantify the prevalence, risk factors and co-carriage of AREf and VREf in humans, cats and dogs in the Dutch population. From 2014 to 2015, ∼2000 inhabitants of the Netherlands each month were randomly invited to complete a questionnaire and provide a faecal sample. Subjects owning pets were also asked to submit one dog or cat sample. Faecal samples were screened for AREf and VREf. The genetic relatedness of isolates was determined using core genome MLST. Logistic regression analysis was used to determine risk factors. Of 25 365 subjects, 4721 (18.6%) completed the questionnaire and 1992 (42.2%) human, 277 dog and 118 cat samples were submitted. AREf was detected in 29 human (1.5%), 71 dog (25.6%) and 6 cat (5.1%) samples. VREf (vanA) was detected in one human and one dog. AREf/VREf co-carriage was not detected in 388 paired samples. The use of antibiotics (OR 4.2, 95% CI 1.7-11.2) and proton pump inhibitors (OR 2.7, 95% CI 1.1-6.3) were risk factors for AREf carriage in humans. In dogs, these were the use of antibiotics (OR 2.3, 95% CI 1.1-4.6) and eating raw meat (OR 3.2, 95% CI 1.4-6.6). Core genome MLST-based phylogenetic linkage indicated clonal relatedness for a minority of human (16.7%) and pet AREf isolates (23.8%) in three clusters. Intestinal carriage with AREf or VREf is rare in the Dutch general population. Although AREf carriage is high in dogs, phylogenetic linkage between human and pet AREf isolates was limited.

Molecular relatedness of ESBL/AmpC-producing Escherichia coli from humans, animals, food and the environment: a pooled analysis.

In recent years, ESBL/AmpC-producing Escherichia coli (ESBL/AmpC-EC) have been isolated with increasing frequency from animals, food, environmental sources and humans. With incomplete and scattered evidence, the contribution to the human carriage burden from these reservoirs remains unclear. To quantify molecular similarities between different reservoirs as a first step towards risk attribution. Pooled data on ESBL/AmpC-EC isolates were recovered from 35 studies in the Netherlands comprising >27 000 samples, mostly obtained between 2005 and 2015. Frequency distributions of ESBL/AmpC genes from 5808 isolates and replicons of ESBL/AmpC-carrying plasmids from 812 isolates were compared across 22 reservoirs through proportional similarity indices (PSIs) and principal component analyses (PCAs). Predominant ESBL/AmpC genes were identified in each reservoir. PCAs and PSIs revealed close human-animal ESBL/AmpC gene similarity between human farming communities and their animals (broilers and pigs) (PSIs from 0.8 to 0.9). Isolates from people in the general population had higher similarities to those from human clinical settings, surface and sewage water and wild birds (0.7-0.8), while similarities to livestock or food reservoirs were lower (0.3-0.6). Based on rarefaction curves, people in the general population had more diversity in ESBL/AmpC genes and plasmid replicon types than those in other reservoirs. Our 'One Health' approach provides an integrated evaluation of the molecular relatedness of ESBL/AmpC-EC from numerous sources. The analysis showed distinguishable ESBL/AmpC-EC transmission cycles in different hosts and failed to demonstrate a close epidemiological linkage of ESBL/AmpC genes and plasmid replicon types between livestock farms and people in the general population.

Transmission of Methicillin-Resistant Staphylococcus aureus to Human Volunteers Visiting a Swine Farm.

ABSTRACTTransmission of methicillin-resistant Staphylococcus aureus (MRSA) from animals to humans is of great concern due to the implications for human health and the health care system. The objective was to investigate the frequency and duration of MRSA carriage in human volunteers after a short-term exposure in a swine farm. The experimental study included 34 human volunteers staying 1 h in a MRSA-positive swine farm in four trials. In two of the trials, the influence of farm work involving pig contact was studied using a crossover design. The quantities of MRSA in nasal swabs, throat swabs, and air samples were measured at different time points and analyzed in relation to relevant covariates. This investigation showed that, overall, 94% of the volunteers acquired MRSA during the farm visit. Two hours after the volunteers left the stable, the nasal MRSA count had declined to unquantifiable levels in 95% of the samples. After 48 h, 94% of the volunteers were MRSA-negative. Nasal MRSA carriage was positively correlated to personal exposure to airborne MRSA and farm work involving pig contact and negatively correlated to smoking. No association was observed between MRSA carriage and face touching behavior, nasal methicillin-susceptible Staphylococcus aureus (MSSA) carriage, age, or gender. The increase in human MRSA carriage among the volunteers with pig contact seems to be dependent on the increased concentration of airborne MRSA of the surrounding air and not directly on physical contact with pigs. MRSA was not detected in any of the throat samples.IMPORTANCE The experimental approach made it possible to elucidate the contributions of airborne MRSA levels and farm work to nasal MRSA carriage in a swine farm. Short-term exposure to airborne MRSA poses a substantial risk for farm visitors to become nasal carriers, but the carriage is typically cleared within hours to a few days. The risk for short-term visitors to cause secondary transmissions of MRSA is most likely negligible due to the observed decline to unquantifiable levels in 95% of the nasal samples after only 2 h. The MRSA load in the nose was highly correlated to the amount of MRSA in the air and interventions to reduce the level of airborne MRSA or the use of face masks might consequently reduce nasal contamination.

Energy performance analysis of a backpack suspension system with a timed clutch for human load carriage

This work theoretically investigates methods of reducing the energetic cost of bipedal walking while carrying a backpack with a suspension system. We extend a previous 2DOF model proposed by Ackerman and Seipel (2014) by adding a timed clutch to the suspension mechanism. The clutch allows the mechanism to switch between states of elastic or rigid connection of the backpack and the body. Periodic switching between the two states of the mechanism is either event-based or timing-based, and may result in inelastic impacts. We study the hybrid dynamics induced by the action of the clutch mechanism, analyze energy expenditure and stability of periodic solutions, and seek for optimal values of stiffness and switching times that minimize the energetic cost. It is found that in many cases, the clutch mechanism can significantly reduce energy expenditure compared to both rigid and elastic suspensions.

High Rates of Human Fecal Carriage of mcr-1-Positive Multidrug-Resistant Enterobacteriaceae Emerge in China in Association With Successful Plasmid Families.

mcr-1-mediated colistin resistance in Enterobacteriaceae is concerning, as colistin is used in treating multidrug-resistant Enterobacteriaceae infections. We identified trends in human fecal mcr-1-positivity rates and colonization with mcr-1-positive, third-generation cephalosporin-resistant (3GC-R) Enterobacteriaceae in Guangzhou, China, and investigated the genetic contexts of mcr-1 in mcr-1-positive 3GC-R strains. Fecal samples were collected from in-/out-patients submitting specimens to 3 hospitals (2011-2016). mcr-1 carriage trends were assessed using iterative sequential regression. A subset of mcr-1-positive isolates was sequenced (whole-genome sequencing [WGS], Illumina), and genetic contexts (flanking regions, plasmids) of mcr-1 were characterized. Of 8022 fecal samples collected, 497 (6.2%) were mcr-1 positive, and 182 (2.3%) harbored mcr-1-positive 3GC-R Enterobacteriaceae. We observed marked increases in mcr-1 (0% [April 2011] to 31% [March 2016]) and more recent (since January 2014; 0% [April 2011] to 15% [March 2016]) increases in human colonization with mcr-1-positive 3GC-R Enterobacteriaceae (P < .001). mcr-1-positive 3GC-R isolates were commonly multidrug resistant. WGS of mcr-1-positive 3GC-R isolates (70 Escherichia coli, 3 Klebsiella pneumoniae) demonstrated bacterial strain diversity; mcr-1 in association with common plasmid backbones (IncI, IncHI2/HI2A, IncX4) and sometimes in multiple plasmids; frequent mcr-1 chromosomal integration; and high mobility of the mcr-1-associated insertion sequence ISApl1. Sequence data were consistent with plasmid spread among animal/human reservoirs. The high prevalence of mcr-1 in multidrug-resistant E. coli colonizing humans is a clinical threat; diverse genetic mechanisms (strains/plasmids/insertion sequences) have contributed to the dissemination of mcr-1, and will facilitate its persistence.

Consumption of edible ice contaminated with Acinetobacter, Pseudomonas, and Stenotrophomonas is a risk factor for fecal colonization with extended-spectrum β-lactamase-producing Escherichia coli in Vietnam.

Although Vietnamese residents frequently harbor extended-spectrum β-lactamase-producing Escherichia coli (ESBL-E), it is unclear which foods/beverages are risk factors for acquiring these bacteria. The aim of this study was to evaluate the frequency with which edible ice served in restaurants is contaminated with antibiotic-resistant bacteria, and thereby clarify whether this product poses a risk for ESBL-E carriage in humans. Ice from restaurants in Vietnam and Japan was screened for bacteria capable of growing on agar containing cefotaxime (BG-CTX). Of the 119 BG-CTX strains isolated in Vietnam, 40%, 39%, and 12% were identified as Pseudomonas spp., Acinetobacter spp., and Stenotrophomonas maltophilia, respectively. Meanwhile, of the six such strains isolated in Japan, five were identified as Acinetobacter spp. and one as Pseudomonas spp. More than 10% of the Acinetobacter isolates exhibited cefotaxime, ceftazidime, and sulfa/trimethoprim resistance, while 21% of Pseudomonas and 14% of S. maltophilia isolates exhibited meropenem and sulfa/trimethoprim resistance, respectively. Subsequent multiplex polymerase chain reaction (PCR) analyses detected ESBL-encoding genes in 10% of the BG-CTX. Notably, feces harvested from mice administered water contaminated with BG-CTX contained E. coli harboring the blaCTX-M-9 gene. In conclusion, our findings indicate that consumption of contaminated edible ice is a risk factor for human ESBL-E carriage.

ESBL carriage in pig slaughterhouse workers is associated with occupational exposure.

We investigated the prevalence of extended-spectrum β-lactamase (ESBL) carriage in slaughterhouse workers and the association with occupational exposure to slaughter animals and products. Stool samples from 334 employees in a Dutch pig slaughterhouse were obtained. Presence of ESBL was determined by selective plating, microarray analysis, and gene sequencing. Questionnaires were used to collect personal and occupational information. The overall prevalence of ESBL carriage was 4·8% (16/334). All ESBL-producing isolates were Escherichia coli. The ESBL genes detected were bla CTX-M-1 (n = 8), bla CTX-M-15 (n = 3), bla CTX-M-27 (n = 2), bla CTX-M-24 (n = 1), bla CTX-M-55 (n = 1), and bla SHV-12 (n = 1). A higher prevalence of ESBL was seen in workers in jobs with as tasks 'removal of lungs, heart, liver, tongue' (33%), and 'removal of head and spinal cord' (25%). For further analysis, participants were divided in two groups based on potential exposure to ESBL as related to their job title. One group with an assumed higher exposure to ESBL (e.g. stable work, stabbing, dehairing, removal of organs) and another group with an assumed lower exposure to ESBL (e.g. refrigeration, packaging and expedition). In the 'higher exposure' group, ten out of 95 (10·5%) were carrying ESBL vs. six out of 233 (2·6%) in the 'lower exposure' group. Human ESBL carriage was significantly associated with job exposure in the slaughterhouse (OR 4·5, CI 1·6-12·6). Results suggest that ESBL carriage in slaughterhouse workers overall is comparable with the Dutch population. Within the slaughterhouse population a difference in carriage exists depending on their position along the slaughter line and tasks involved.

Prevalence, risk factors, outcomes, and molecular epidemiology of mcr-1-positive Enterobacteriaceae in patients and healthy adults from China: an epidemiological and clinical study

The mcr-1 gene confers transferable colistin resistance. mcr-1-positive Enterobacteriaceae (MCRPE) have attracted substantial medical, media, and political attention; however, so far studies have not addressed their clinical impact. Herein, we report the prevalence of MCRPE in human infections and carriage, clinical associations of mcr-1-positive Escherichia coli (MCRPEC) infection, and risk factors for MCRPEC carriage. We undertook this study at two hospitals in Zhejiang and Guangdong, China. We did a retrospective cross-sectional assessment of prevalence of MCRPE infection from isolates of Gram-negative bacteria collected at the hospitals from 2007 to 2015 (prevalence study). We did a retrospective case-control study of risk factors for infection and mortality after infection, using all MCRPEC from infection isolates and a random sample of mcr-1-negative E coli infections from the retrospective collection between 2012 and 2015 (infection study). We also did a prospective case-control study to assess risk factors for carriage of MCRPEC in rectal swabs from inpatients with MCRPEC and mcr-1 negative at the hospitals and collected between May and December, 2015, compared with mcr-1-negative isolates from rectal swabs of inpatients (colonisation study). Strains were analysed for antibiotic resistance, plasmid typing, and transfer analysis, and strain relatedness. We identified 21 621 non-duplicate isolates of Enterobacteriaceae, Acinetobacter spp, and Pseudomonas aeruginosa from 18 698 inpatients and 2923 healthy volunteers. Of 17 498 isolates associated with infection, mcr-1 was detected in 76 (1%) of 5332 E coli isolates, 13 (<1%) of 348 Klebsiella pneumoniae, one (<1%) of 890 Enterobacter cloacae, and one (1%) of 162 Enterobacter aerogenes. For the infection study, we included 76 mcr-1-positive clinical E coli isolates and 508 mcr-1-negative isolates. Overall, MCRPEC infection was associated with male sex (209 [41%] vs 47 [63%], adjusted p=0·011), immunosuppression (30 [6%] vs 11 [15%], adjusted p=0·011), and antibiotic use, particularly carbapenems (45 [9%] vs 18 [24%], adjusted p=0·002) and fluoroquinolones (95 [19%] vs 23 [30%], adjusted p=0·017), before hospital admission. For the colonisation study, we screened 2923 rectal swabs from healthy volunteers, of which 19 were MCRPEC, and 1200 rectal swabs from patients, of which 35 were MCRPEC. Antibiotic use before hospital admission (p<0·0001) was associated with MCRPEC carriage in 35 patients compared with 378 patients with mcr-1-negative E coli colonisation, whereas living next to a farm was associated with mcr-1-negative E coli colonisation (p=0·03, univariate test). mcr-1 could be transferred between bacteria at high frequencies (10-1 to 10-3), and plasmid types and MCRPEC multi-locus sequence types (MLSTs) were more variable in Guangdong than in Zhejiang and included the human pathogen ST131. MCRPEC also included 17 unreported ST clades. In 2017, colistin will be formally banned from animal feeds in China and switched to human therapy. Infection with MRCPEC is associated with sex, immunosuppression, and previous antibiotic exposure, while colonisation is also associated with antibiotic exposure. MLST and plasmid analysis shows that MCRPEC are diversely spread throughout China and pervasive in Chinese communities. National Key Basic Research Program of China, National Natural Science Foundation of China/Zhejiang, National Key Research and Development Program, and MRC, UK.

Suspending loads decreases load stability but may slightly improve body stability

Here, we seek to determine how compliantly suspended loads could affect the dynamic stability of legged locomotion. We theoretically model the dynamic stability of a human carrying a load using a coupled spring-mass-damper model and an actuated spring-loaded inverted pendulum model, as these models have demonstrated the ability to correctly predict other aspects of locomotion with a load in prior work, such as body forces and energetic cost. We report that minimizing the load suspension natural frequency and damping ratio significantly reduces the stability of the load mass but may slightly improve the body stability of locomotion when compared to a rigidly attached load. These results imply that a highly-compliant load suspension could help stabilize body motion during human, animal, or robot load carriage, but at the cost of a more awkward (less stable) load.

Extended-spectrum β-lactamase- and pAmpC-producing Enterobacteriaceae among the general population in a livestock-dense area

ObjectivesIn the Netherlands there is an ongoing debate regarding environmental health risks of livestock farming for neighbouring residents. This explorative study aims to determine the prevalence of carriage of extended-spectrum β-lactamase and/or plasmid-mediated AmpC-producing Enterobacteriaceae (ESBL/pAmpC-E) in the general population living in a livestock-dense area, and to study associations between determinants, including exposure through contact with animals and the environment, and human carriage of ESBL/pAmpC-E. MethodsA cross-sectional study was performed among 2432 adults (aged 20–72 years) in 12 temporary research centres in the south of the Netherlands, consisting of a questionnaire and analysis of a faecal sample to assess carriage of ESBL/pAmpC-E. Risk factors were analysed using logistic regression. ResultsThe prevalence for carriage of ESBL/pAmpC-E was 4.5% (109/2432; 95% CI 3.7–5.4) ranging from 1.4% to 10.9% among the research centres. ESBL/pAmpC resistance genes were detected in Escherichia coli and Klebsiella pneumoniae isolates obtained from these 109 persons and the most common ESBL-resistance genes were blaCTX-M-15, blaCTX-M-14/17 and blaCTX-M-1, originating from 76 participants. Travel in the previous 12 months to Africa, Asia or Latin America (OR 2.82; 95% CI 1.71–4.63), having kept cows for a hobby in the previous 5 years (OR 3.77; 95% CI 1.22–11.64), usage of proton-pump inhibitors (OR 1.84; 95% CI 1.05–3.23), and living within 1000 m of a mink farm (OR 2.26; 95% CI 1.28–3.98) were identified as risk factors. Exposure to poultry was not identified as a risk factor. ConclusionsOverall, living in close proximity to livestock animals and farms does not seem to be a risk factor for carriage of ESBL/pAmpC-E.

Transmission of Staphylococcus aureus from Humans to Green Monkeys in The Gambia as Revealed by Whole-Genome Sequencing.

ABSTRACTStaphylococcus aureus is an important pathogen of humans and animals. We genome sequenced 90 S. aureus isolates from The Gambia: 46 isolates from invasive disease in humans, 13 human carriage isolates, and 31 monkey carriage isolates. We inferred multiple anthroponotic transmissions of S. aureus from humans to green monkeys (Chlorocebus sabaeus) in The Gambia over different time scales. We report a novel monkey-associated clade of S. aureus that emerged from a human-to-monkey switch estimated to have occurred 2,700 years ago. Adaptation of this lineage to the monkey host is accompanied by the loss of phage-carrying genes that are known to play an important role in human colonization. We also report recent anthroponotic transmission of the well-characterized human lineages sequence type 6 (ST6) and ST15 to monkeys, probably because of steadily increasing encroachment of humans into the monkeys' habitat. Although we have found no evidence of transmission of S. aureus from monkeys to humans, as the two species come into ever-closer contact, there might be an increased risk of additional interspecies exchanges of potential pathogens. IMPORTANCE The population structures of Staphylococcus aureus in humans and monkeys in sub-Saharan Africa have been previously described using multilocus sequence typing (MLST). However, these data lack the power to accurately infer details regarding the origin and maintenance of new adaptive lineages. Here, we describe the use of whole-genome sequencing to detect transmission of S. aureus between humans and nonhuman primates and to document the genetic changes accompanying host adaptation. We note that human-to-monkey switches tend to be more common than the reverse and that a novel monkey-associated clade is likely to have emerged from such a switch approximately 2,700 years ago. Moreover, analysis of the accessory genome provides important clues as to the genetic changes underpinning host adaptation and, in particular, shows that human-to-monkey switches tend to be associated with the loss of genes known to confer adaptation to the human host.

A dynamic relationship between mucosal T helper type 17 and regulatory T-cell populations in nasopharynx evolves with age and associates with the clearance of pneumococcal carriage in humans

Pneumococcal carriage is common in young children, which may account for the high incidence of disease in this age group. Host factors determining the clearance of carriage in humans remain unclear. We aimed to study the relationships between T helper type 17 (Th17) and Foxp3+ regulatory T (Treg) cells in nasopharynx-associated lymphoid tissue (NALT) and carriage in children and adults. Frequencies of Th17 and Treg cells in NALT were analysed by flow cytometry in association with age and pneumococcal carriage status. Cytokine responses following pneumococcal stimulation were analysed by cytometric beads array. The frequencies of Th17 and Treg cells in NALT were inversely correlated (R –0.60). Whereas Treg cell frequency decreased with age (R –0.63), both Th17 and the Th17: Treg ratio increased with age (R 0.62 and R 0.64, respectively). Also, the Th17: Treg ratio was higher in carriage-negative than in carriage-positive children (p <0.01). Pneumococcal stimulation of tonsillar cells increased both Th17 and Treg cell numbers, but the Th17: Treg ratio and pattern of cytokine responses differed between carriage-negative and carriage-positive children. The former showed markedly higher Th17: Treg and interleukin-17A: interleukin-10 ratios than in the latter (p <0.01). Pneumococcal stimulation also induces Th17, although the capacity of this Th17 differentiation from naive T cells of young children was low, but increased with age. We demonstrated a dynamic relationship between Th17 and Treg cells in human nasopharynx that evolves with age. The balance between Th17 and Treg cells in NALT appears to be a major host factor closely associated with the clearance of Streptococcus pneumoniae from the nasopharynx.