Lack of dissemination of acquired resistance to β-lactams in small wild mammals around an isolated village in the Amazonian forest

Staphylococcus aureus Host Spectrum Correlates with Methicillin Resistance in a Multi-Species Ecosystem

Although antibiotic resistance is a major issue for both human and animal health, very few studies have investigated the role of the bacterial host spectrum in its dissemination within natural ecosystems. Here, we assessed the prevalence of methicillin resistance among Staphylococcus aureus (MRSA) isolates from humans, non-human primates (NHPs), micromammals and bats in a primatology center located in southeast Gabon, and evaluated the plausibility of four main predictions regarding the acquisition of antibiotic resistance in this ecosystem. MRSA strain prevalence was much higher in exposed species (i.e., humans and NHPs which receive antibiotic treatment) than in unexposed species (micromammals and bats), and in NHP species living in enclosures than those in captivity-supporting the assumption that antibiotic pressure is a risk factor in the acquisition of MRSA that is reinforced by the irregularity of drug treatment. In the two unexposed groups of species, resistance prevalence was high in the generalist strains that infect humans or NHPs, supporting the hypothesis that MRSA strains diffuse to wild species through interspecific transmission of a generalist strain. Strikingly, the generalist strains that were not found in humans showed a higher proportion of MRSA strains than specialist strains, suggesting that generalist strains present a greater potential for the acquisition of antibiotic resistance than specialist strains. The host spectrum is thus a major component of the issue of antibiotic resistance in ecosystems where humans apply strong antibiotic pressure.

Naturalized Escherichia coli in Wastewater and the Co-evolution of Bacterial Resistance to Water Treatment and Antibiotics

Antibiotic resistance represents one of the most pressing concerns facing public health today. While the current antibiotic resistance crisis has been driven primarily by the anthropogenic overuse of antibiotics in human and animal health, recent efforts have revealed several important environmental dimensions underlying this public health issue. Antibiotic resistant (AR) microbes, AR genes, and antibiotics have all been found widespread in natural environments, reflecting the ancient origins of this phenomenon. In addition, modern societal advancements in sanitation engineering (i.e., sewage treatment) have also contributed to the dissemination of resistance, and concerningly, may also be promoting the evolution of resistance to water treatment. This is reflected in the recent characterization of naturalized wastewater strains of Escherichia coli-strains that appear to be adapted to live in wastewater (and meat packing plants). These strains carry a plethora of stress-resistance genes against common treatment processes, such as chlorination, heat, UV light, and advanced oxidation, mechanisms which potentially facilitate their survival during sewage treatment. These strains also carry an abundance of common antibiotic resistance genes, and evidence suggests that resistance to some antibiotics is linked to resistance to treatment (e.g., tetracycline resistance and chlorine resistance). As such, these naturalized E. coli populations may be co-evolving resistance against both antibiotics and water treatment. Recently, extraintestinal pathogenic strains of E. coli (ExPEC) have also been shown to exhibit phenotypic resistance to water treatment, seemingly associated with the presence of various shared genetic elements with naturalized wastewater E. coli. Consequently, some pathogenic microbes may also be evolving resistance to the two most important public health interventions for controlling infectious disease in modern society-antibiotic therapy and water treatment.

The oral microbiota of wild bears in Sweden reflects the history of antibiotic use by humans

Following the advent of industrial-scale antibiotic production in the 1940s,¹ antimicrobial resistance (AMR) has been on the rise and now poses a major global health threat in terms of mortality, morbidity, and economic burden.^2,3 Because AMR can be exchanged between humans, livestock, and wildlife, wild animals can be used as indicators of human-associated AMR contamination of the environment.⁴ However, AMR is a normal function of natural environments and is present in host-associated microbiomes, which makes it challenging to distinguish between anthropogenic and natural sources.^4,5 One way to overcome this difficulty is to use historical samples that span the period from before the mass production of antibiotics to today. We used shotgun metagenomic sequencing of dental calculus, the calcified form of the oral microbial biofilm, to determine the abundance and repertoire of AMR genes in the oral microbiome of Swedish brown bears collected over the last 180 years. Our temporal metagenomics approach allowed us to establish a baseline of natural AMR in the pre-antibiotics era and to quantify a significant increase in total AMR load and diversity of AMR genes that is consistent with patterns of national human antibiotic use. We also demonstrated a significant decrease in total AMR load in bears in the last two decades, which coincides with Swedish strategies to mitigate AMR. Our study suggests that public health policies can be effective in limiting human-associated AMR contamination of the environment and wildlife.

Characteristics and Epidemiology of Extended-Spectrum β-Lactamase-Producing Multidrug-Resistant Klebsiella pneumoniae From Red Kangaroo, China

Due to its drug resistant nature, β-lactamase represents a serious challenge for public health. Extended-spectrum β-lactamase (ESBL) producing Klebsiella pneumoniae clones are increasingly reported worldwide. Little is known about the prevalence and biological characteristics of drug-resistant strains in zoos. During routine surveillance at the Zhengzhou Zoo of China, we found Klebsiella pneumoniae isolate in healthy Red Kangaroos (Macropus Rufus) with severe MDR. The Klebsiella pneumoniae were especially resistant to Cefuroxime Sodium (MIC, > 64 μg/mL), Ceftriaxone (MIC, >8 μg/mL) and Cefepime (MIC, >64 μg/mL), and belonged to ST290. Subsequently, whole genome sequencing (WGS) showed that the Chrome Chr-M297-1 harbored bla_DHA–3, bla_SHV–1, bla_CTX–M–14, fosA5, dfrA3, sul3, etc., and pM297-1.1 [222,864 bp, IncFIB(K)], which carried nine antimicrobial genes including bla_CTX–M–14, bla_TEM–191, aph(3″)-Ib, aph(6)-Id and qnrS1, etc., and pM297-1.2 [225,763 bp, IncFII(K)] carried 22 antimicrobial genes including bla_TEM–1, bla_CTX–M–3, aph(3′)-Ia, aac(3)-IIa, aac(6′)-Ib-cr, aadA16, qnrB2, qnrS1, qacEΔ1, mphA, sul1, and dfrA27, etc. A traceability analysis then revealed that these two plasmids were highly similar to those recovered from human clinical samples in some southern cities in Sichuan Province, China (>99%), suggesting that these plasmids are spreading in China. Furthermore, two plasmids harboring conjugal transfer genes facilitated the transmission of antimicrobial genes by conjugation with E. coli J53. Our research shows that the transmission and adaptation of Klebsiella pneumoniae producing ESBLs is occurring in zoo environments, suggesting that zoos may be becoming important potential reservoirs for clinically important drug-resistant genes. It is therefore necessary to monitor the emergence and spread of drug-resistant gene strains in captive wild animals held in zoo environments.

Draft Genome Sequence of an Escherichia coli Sequence Type 155 Strain Isolated from Sewage in Kerala, India

We report the draft genome sequence of Escherichia coli ASBT-1, a representative of E. coli sequence type 155 (ST155), obtained from India. Considering the known wide variety of pathogenic and antibiotic resistance potentials, this strain should be of great interest for detailed comparative genomic analysis.

Day-to-Day Dynamics of Commensal Escherichia coli in Zimbabwean Cows Evidence Temporal Fluctuations within a Host-Specific Population Structure

To get insights into the temporal pattern of commensal Escherichia coli populations, we sampled the feces of four healthy cows from the same herd in the Hwange District of Zimbabwe daily over 25 days. The cows had not received antibiotic treatment during the previous 3 months. We performed viable E. coli counts and characterized the 326 isolates originating from the 98 stool samples at a clonal level, screened them for stx and eae genes, and tested them for their antibiotic susceptibilities. We observed that E. coli counts and dominant clones were different among cows, and very few clones were shared. No clone was shared by three or four cows. Clone richness and evenness were not different between cows. Within each host, the variability in the E. coli count was evidenced between days, and no clone was found to be dominant during the entire sampling period, suggesting the existence of clonal interference. Dominant clones tended to persist longer than subdominant ones and were mainly from phylogenetic groups A and B1. Five E. coli clones were found to contain both the stx₁ and stx₂ genes, representing 6.3% of the studied isolates. All cows harbored at least one Shiga toxin-producing E. coli (STEC) strain. Resistance to tetracycline, penicillins, trimethoprim, and sulfonamides was rare and observed in three clones that were shed at low levels in two cows. This study highlights the fact that the commensal E. coli population, including the STEC population, is host specific, is highly dynamic over a short time frame, and rarely carries antibiotic resistance determinants in the absence of antibiotic treatment.IMPORTANCE The literature about the dynamics of commensal Escherichia coli populations is very scarce. Over 25 days, we followed the total E. coli counts daily and characterized the sampled clones in the feces of four cows from the same herd living in the Hwange District of Zimbabwe. This study deals with the day-to-day dynamics of both quantitative and qualitative aspects of E. coli commensal populations, with a focus on both Shiga toxin-producing E. coli and antibiotic-resistant E. coli strains. We show that the structure of these commensal populations was highly specific to the host, even though the cows ate and roamed together, and was highly dynamic between days. Such data are of importance to understand the ecological forces that drive the dynamics of the emergence of E. coli clones of particular interest within the gastrointestinal tract and their transmission between hosts.

Genetic characterization of commensal Escherichia coli isolated from laboratory rodents

Background

Escherichia coli, a commensal in the intestines of vertebrates, is capable of colonizing many different hosts and the environment. Commensal E. coli strains are believed to be the precursor of pathogenic strains by means of acquisition of antimicrobial resistant and virulence genes. Laboratory rodents are inherently susceptible to numerous known infectious agents, which could transfer virulence determinants to commensal E. coli. Hence, in this study, the genetic structure of commensal E. coli found in laboratory rodents and their antimicrobial resistance profiles were investigated.

Results

E. coli strains belonging to phylogroup A were the predominant strain obtained from the animals used in the study. Four novel sequence types (ST746, ST747, ST748 and ST749) were discovered using the multi locus sequence typing, together with one common ST357 in the gastrointestinal tract, liver and, the trachea and lung. Serotyping demonstrated that these commensal E. coli strains were non-Shiga toxin-producers. Phenotypic and genotypic analyses of extended spectrum beta lactamases were also negative.

Conclusions

These findings implied that the E. coli strains recovered from the laboratory rodents were truly commensal in nature. Further study is required to investigate the possible influence of gender on the susceptibility of hosts to E. coli colonization in laboratory rodents.

Electronic supplementary material

The online version of this article (doi:10.1186/s40064-016-2745-9) contains supplementary material, which is available to authorized users.

Escherichia coli Population Structure and Antibiotic Resistance at a Buffalo/Cattle Interface in Southern Africa

At a human/livestock/wildlife interface, Escherichia coli populations were used to assess the risk of bacterial and antibiotic resistance dissemination between hosts. We used phenotypic and genotypic characterization techniques to describe the structure and the level of antibiotic resistance of E. coli commensal populations and the resistant Enterobacteriaceae carriage of sympatric African buffalo (Syncerus caffer caffer) and cattle populations characterized by their contact patterns in the southern part of Hwange ecosystem in Zimbabwe. Our results (i) confirmed our assumption that buffalo and cattle share similar phylogroup profiles, dominated by B1 (44.5%) and E (29.0%) phylogroups, with some variability in A phylogroup presence (from 1.9 to 12%); (ii) identified a significant gradient of antibiotic resistance from isolated buffalo to buffalo in contact with cattle and cattle populations expressed as the Murray score among Enterobacteriaceae (0.146, 0.258, and 0.340, respectively) and as the presence of tetracycline-, trimethoprim-, and amoxicillin-resistant subdominant E. coli strains (0, 5.7, and 38%, respectively); (iii) evidenced the dissemination of tetracycline, trimethoprim, and amoxicillin resistance genes (tet, dfrA, and blaTEM-1) in 26 isolated subdominant E. coli strains between nearby buffalo and cattle populations, that led us (iv) to hypothesize the role of the human/animal interface in the dissemination of genetic material from human to cattle and toward wildlife. The study of antibiotic resistance dissemination in multihost systems and at anthropized/natural interface is necessary to better understand and mitigate its multiple threats. These results also contribute to attempts aiming at using E. coli as a tool for the identification of pathogen transmission pathway in multihost systems.

Emergence of Antimicrobial-Resistant Escherichia coli of Animal Origin Spreading in Humans

In the context of the great concern about the impact of human activities on the environment, we studied 403 commensal Escherichia coli/Escherichia clade strains isolated from several animal and human populations that have variable contacts to one another. Multilocus sequence typing (MLST) showed a decrease of diversity 1) in strains isolated from animals that had an increasing contact with humans and 2) in all strains that had increased antimicrobial resistance. A specific B1 phylogroup clonal complex (CC87, Institut Pasteur schema nomenclature) of animal origin was identified and characterized as being responsible for the increased antimicrobial resistance prevalence observed in strains from the environments with a high human-mediated antimicrobial pressure. CC87 strains have a high capacity of acquiring and disseminating resistance genes with specific metabolic and genetic determinants as demonstrated by high-throughput sequencing and phenotyping. They are good mouse gut colonizers but are not virulent. Our data confirm the predominant role of human activities in the emergence of antimicrobial resistance in the environmental bacterial strains and unveil a particular E. coli clonal complex of animal origin capable of spreading antimicrobial resistance to other members of microbial communities.