[Genetic characterization and drug resistance analysis of Salmonella Kentucky ST314 in Shenzhen in 2010-2021].

OBJECTIVE: To understand the prevalence, genetic characteristics and drug resistance features of Salmonella Kentucky ST314 in Shenzhen. METHODS: Whole genome sequencing of 14 strains of Salmonella Kentucky ST314 collected from 2010-2021 by the Foodborne Disease Surveillance Network of Shenzhen Center for Disease Control and Prevention for phylogenetic evolutionary analysis, drug resistance gene and plasmid detection; drug susceptibility experiments were performed by micro-broth dilution method. RESULTS: A total of 57 strains of Salmonella Kentucky were collected from the foodborne disease surveillance network, 14 of which were ST314. The Shenzhen isolates were clustered with isolates from Southeast Asian countries such as Vietnam and Thailand on clade 314.2, and the single nucleotide polymorphism distance between local strains in Shenzhen was large, indicating dissemination. In this study, a total of 17 drug resistance genes/mutations in 9 categories were detected in the genome of Salmonella Kentucky ST314, carrying 3 extended spectrum beta-lactamases(ESBLs), including bla_(CTX-M-24)(14.3%, 2/14), bla_(CTX-M-55)(7.1%, 1/14), and bla_(CTX-M-130)(14.3%, 2/14), all located on plasmids. Regarding quinolone resistance factors, two plasmid-mediated quinolone resistance(PMQR) genes were identified in the genome: qnrB6(71.4%, 10/14) and aac(6')Ib-cr(78.6%, 11/14), a quinolone resistance quinolone resistance-determining regions(QRDR) mutation T57 S(100%, 14/14). The multi-drug resistance rate of Salmonella Kentucky ST314 in Shenzhen was 92.86%(13/14)with the highest rate of resistance to tetracycline and cotrimoxazole(100%, 14/14), followed by chloramphenicol(92.86%, 13/14), cefotaxime and ampicillin(78.57%, 11/14), ciprofloxacin and nalidixic acid(71.43%, 10/14), and ampicillin-sulbactam had the lowest resistance rate(21.43%, 3/14). CONCLUSION: ST314 is the second most prevalent ST type among Salmonella Kentucky in Shenzhen, mainly isolated from food, especially poultry; phylogenetic analysis suggests that ST314 is a disseminated infection and the genome shows a highly genetically conserved phenotype. Drug resistance of Salmonella Kentucky ST314 is very serious, especially QRDR mutation, PMQR gene co-mediated quinolone resistance and plasmid-mediated cephalosporin resistance are prominent and deserve extensive attention.

Emergence and genomic chion of Proteus mirabilis harboring blaNDM-1 in Korean companion dogs.

Proteus mirabilis is a commensal bacterium dwelling in the gastrointestinal (GI) tract of humans and animals. Although New Delhi metallo-ß-lactamase 1 (NDM-1) producing P. mirabilis is emerging as a threat, its epidemiology in our society remains largely unknown. LHPm1, the first P. mirabilis isolate harboring NDM-1, was detected from a companion dog that resides with a human owner. The whole-genome study revealed 20 different antimicrobial resistance (AMR) genes against various classes of antimicrobial agents, which corresponded to the MIC results. Genomic regions, including MDR genes, were identified with multiple variations and visualized in a comparative manner. In the whole-genome epidemiological analysis, multiple phylogroups were identified, revealing the genetic relationship of LHPm1 with other P. mirabilis strains carrying various AMR genes. These genetic findings offer comprehensive insights into NDM-1-producing P. mirabilis, underscoring the need for urgent control measures and surveillance programs using a "one health approach".

Chromosomal integration and plasmid fusion occurring in ST20 carbapenem-resistant Klebsiella pneumoniae isolates coharboring blaNDM-1 and blaIMP-4 induce resistance transmission and fitness variation.

To investigate the epidemiology of ST20 carbapenem-resistant Klebsiella pneumoniae (CRKP) in China, and further explore the genomic characteristics of blaIMP-4 and blaNDM-1 coharboring isolates and plasmid contributions to resistance and fitness. Seven ST20 CRKP isolates were collected nationwide, and antimicrobial susceptibility testing was performed. Antimicrobial resistance genes, virulence genes, and plasmid replicons were identified via whole-genome sequencing, and clonality assessed via core-genome multilocus sequence typing. Furthermore, we found four dual-metallo-ß-lactamases (MBL)-harbouring isolates, the gene location was detected by Southern blotting, and plasmid location analysis showed that blaIMP-4 was located on a separate plasmid, a self-conjugative fusion plasmid, or the bacterial chromosome. These isolates were subjected to long-read sequencing, the presence of blaIMP-4 in different locations was identified by genomic comparison, and transposon units were detected via inverse PCR. We subsequently found that blaIMP-4 on the fusion plasmid and bacterial chromosome was formed via intact plasmid recombination by the IS26 and ltrA, respectively, and the circular transposon unit was related to cointegration, however, blaIMP-4 in different locations did not affect the gene stability. The blaNDM-1-harbouring plasmid contributed to the increased resistance to ß-lactams and shortened survival lag time which was revealed in plasmid cured isolates. In summary, the K. pneumoniae ST20 clone is a high-risk resistant clone. With the use of ceftazidime/avibactam, MBL-positive isolates, especially dual-MBL-harbouring isolates, should be given additional attention.

Inferring Mycobacterium Tuberculosis Drug Resistance and Transmission using Whole-genome Sequencing in a High TB-burden Setting in China.

Objective: China is among the 30 countries with a high burden of tuberculosis (TB) worldwide, and TB remains a public health concern. Kashgar Prefecture in the southern Xinjiang Autonomous Region is considered as one of the highest TB burden regions in China. However, molecular epidemiological studies of Kashgar are lacking. Methods: A population-based retrospective study was conducted using whole-genome sequencing (WGS) to determine the characteristics of drug resistance and the transmission patterns. Results: A total of 1,668 isolates collected in 2020 were classified into lineages 2 (46.0%), 3 (27.5%), and 4 (26.5%). The drug resistance rates revealed by WGS showed that the top three drugs in terms of the resistance rate were isoniazid (7.4%, 124/1,668), streptomycin (6.0%, 100/1,668), and rifampicin (3.3%, 55/1,668). The rate of rifampicin resistance was 1.8% (23/1,290) in the new cases and 9.4% (32/340) in the previously treated cases. Known resistance mutations were detected more frequently in lineage 2 strains than in lineage 3 or 4 strains, respectively: 18.6% vs. 8.7 or 9%, P < 0.001. The estimated proportion of recent transmissions was 25.9% (432/1,668). Multivariate logistic analyses indicated that sex, age, occupation, lineage, and drug resistance were the risk factors for recent transmission. Despite the low rate of drug resistance, drug-resistant strains had a higher risk of recent transmission than the susceptible strains (adjusted odds ratio, 1.414; 95% CI, 1.023-1.954; P = 0.036). Among all patients with drug-resistant tuberculosis (DR-TB), 78.4% (171/218) were attributed to the transmission of DR-TB strains. Conclusion: Our results suggest that drug-resistant strains are more transmissible than susceptible strains and that transmission is the major driving force of the current DR-TB epidemic in Kashgar.

The recent rapid expansion of multidrug resistant Ural lineage Mycobacterium tuberculosis in Moldova.

The projected trajectory of multidrug resistant tuberculosis (MDR-TB) epidemics depends on the reproductive fitness of circulating strains of MDR M. tuberculosis (Mtb). Previous efforts to characterize the fitness of MDR Mtb have found that Mtb strains of the Beijing sublineage (Lineage 2.2.1) may be more prone to develop resistance and retain fitness in the presence of resistance-conferring mutations than other lineages. Using Mtb genome sequences from all culture-positive cases collected over two years in Moldova, we estimate the fitness of Ural (Lineage 4.2) and Beijing strains, the two lineages in which MDR is concentrated in the country. We estimate that the fitness of MDR Ural strains substantially exceeds that of other susceptible and MDR strains, and we identify several mutations specific to these MDR Ural strains. Our findings suggest that MDR Ural Mtb has been transmitting efficiently in Moldova and poses a substantial risk of spreading further in the region.

High carriage of plasmid-mediated quinolone resistance (PMQR) genes by ESBL-producing and fluoroquinolone-resistant Escherichia coli recovered from animal waste dumps.

BACKGROUND: There has been a rise in the consumption of fluoroquinolones in human and veterinary medicine recently. This has contributed to the rising incidence of quinolone resistance in bacteria. This study aimed at the determination of the antibiotic resistance profile of ESBL-producing and fluoroquinolone-resistant E. coli (FQEC) isolated from animal waste obtained from the waste dumps of an agricultural farm and their carriage of genes encoding PMQR. METHODS AND RESULTS: Isolation of ESBL-producing E. coli from animal waste samples was done on CHROMagar ESBL, while presumptive isolates were purified, and identified via the detection of uidA gene. Susceptibility to a panel of ten antibiotics was done using the disc diffusion method, and detection of PMQR genes (qnrA, qnrB, qnrS, aac(6')-lb-cr, qepA and oqxAB) was done using monoplex and duplex PCR. Twenty-five ESBL-producing and FQEC were obtained from the cattle (6), piggery (7) and poultry (12) waste dumps of the farm. There was 100% resistance to cefpodoxime, cefotaxime, enrofloxacin, trimethoprim-sulfamethoxazole and penicillin by the isolates. The resistance to the other antibiotics was streptomycin (48%), ceftazidime (24%), while no isolate resisted amoxicillin-clavulanate and imipenem. The frequencies of PMQR genes detected were; qnrA (96%), oqxAB (96%), qnrB (92%), while  qnrS was detected in 88% (22) of the isolates. Aminoglycoside acetyltransferase (aac(6')-lb-cr) and quinolone efflux pump (qepA) were each detected in 20 (80%) of the isolates. CONCLUSIONS: This study showed that animal wastes disposed indiscriminately into dumps could be a budding 'hotspot' for multidrug resistant, ESBL-producing and fluoroquinolone-resistant E. coli carrying multiple genes encoding resistance to fluoroquinolone antibiotics.

Comprehensive genomic and plasmid characterization of multidrug-resistant bacterial strains by R10.4.1 nanopore sequencing.

The escalating prevalence of multidrug-resistant (MDR) bacteria pose a significant public health threat. Understanding the genomic features and deciphering the antibiotic resistance profiles of these pathogens is crucial for development of effective surveillance and treatment strategies. In this study, we employed the R10.4.1 nanopore sequencing technology, specifically through the use of the MinION platform, to analyze eight MDR bacterial strains originating from clinical, ecological and food sources. A single 72-hour sequencing run could yield approximately 12 million reads which covered a total of 34 gigabases (Gbp). The nanopore R10.4.1 data was processed using the Flye assembler, successfully assembling the genomes of eight bacterial strains and their 18 plasmids. Notably, the assemblies generated solely from R10.4.1 nanopore data closely matched those from next-generation sequencing data. Diverse antibiotic resistance patterns and specific resistance genes in the test strains were identified. Hospital strains that exhibited multidrug resistance were found to harbor various resistance genes that encode efflux pumps and extended-spectrum ß-lactamases. Environmental and food sources were found to display resistance profiles in a species-specific manner. The composition of structurally complex plasmids in the test strains could also be revealed by analysis of nanopore long reads, which also suggested evidence of horizontal transfer of plasmids between different bacterial species. These findings provide valuable insights into the genetic characteristics of MDR bacteria and demonstrating the practicality of nanopore sequencing technology for detecting of resistance elements in bacterial pathogens.

Multidrug-resistant Mycobacterium tuberculosis transmission in Shandong, China.

Multidrug-resistant tuberculosis (MDR-TB) has imposed a significant economic and health burden worldwide, notably in China. Using whole genome sequence, we sought to understand the mutation and transmission of MDR-TB in Shandong. A retrospective study of patients diagnosed with pulmonary tuberculosis in Shandong from 2009 to 2018 was conducted. To explore transmission patterns, we performed whole genome sequencing on MDR-TB isolates, identified genomic clusters, and assessed the drug resistance of TB isolates. Our study analyzed 167 isolates of MDR-TB, finding that 100 were clustered. The predominant lineage among MDR-TB isolates was lineage 2, specifically with a notable 88.6% belonging to lineage 2.2.1. Lineage 4 constituted a smaller proportion, accounting for 4.2% of the isolates. We discovered that Shandong has a significant clustering percentage for MDR-TB, with Jining having the highest percentage among all Shandong cities. The clustering percentages of MDR-TB, pre-extensively drug-resistant tuberculosis, and extensively drug-resistant tuberculosis were 59.9%, 66.0%, and 71.4%, respectively, and the clustering percentages increased with the expansion of the anti-TB spectrum. Isolates from genomic clusters 1 and 3 belonged to lineage 2.2.1 and showed signs of cross-regional transmission. The distribution of rrs A1401G and katG S315T mutations in lineage 2.2.1 and 2.2.2 strains differed significantly (P < .05). MDR-TB isolates with rpoB I480V, embA-12C > T, and rrs A1401G mutations showed a higher likelihood of clustering (P < .05). Our findings indicate a significant problem of local transmission of MDR-TB in Shandong, China. Beijing lineage isolates and some drug-resistant mutations account for the MDR-TB transmission in Shandong.

A One Health Perspective on Salmonella enterica Serovar Infantis, an Emerging Human Multidrug-Resistant Pathogen.

Salmonella enterica serovar Infantis presents an ever-increasing threat to public health because of its spread throughout many countries and association with high levels of antimicrobial resistance (AMR). We analyzed whole-genome sequences of 5,284 Salmonella Infantis strains from 74 countries, isolated during 1989-2020 from a wide variety of human, animal, and food sources, to compare genetic phylogeny, AMR determinants, and plasmid presence. The global Salmonella Infantis population structure diverged into 3 clusters: a North American cluster, a European cluster, and a global cluster. The levels of AMR varied by Salmonella Infantis cluster and by isolation source; 73% of poultry isolates were multidrug resistant, compared with 35% of human isolates. This finding correlated with the presence of the pESI megaplasmid; 71% of poultry isolates contained pESI, compared with 32% of human isolates. This study provides key information for public health teams engaged in reducing the spread of this pathogen.

Antimicrobial resistance and public and animal health risks associated with pathogenic Escherichia coli isolated from calves.

We aimed to determine the antimicrobial susceptibility profile of pathogenic Escherichia coli strains isolated from fecal samples of calves and buffalo calves (2008-2013), in Minas Gerais, Brazil, as well as the frequency of O157 gene and strains carrying extended-spectrum beta-lactamases (ESBL) and mobile colistin resistance (mcr) genes. E. coli strains (n=518) were tested for susceptibility against ten antimicrobials. Tetracycline was the antimicrobial with the highest resistance rate (382/518), followed by ampicillin (321/518), sulfamethoxazole/trimethoprim (312/518), chloramphenicol (192/518), gentamicin (126/518), ciprofloxacin (148/518), cefazolin (89/518), colistin (54/518) and cefoxitin (34/518). Multidrug resistance (MDR) was observed in 381/518 isolates. No strain harbored mcr or O157 genes, whereas 19/99 were ESBL positive. The most prevalent pathotype and phylogroup were STEC and B1, respectively. Age, EHEC pathotype and resistance to aminoglycoside and cephem were significantly associated with MDR in the multivariate model. Overall, E. coli strains showed high rates of resistance to penicillin, tetracyclines and folate inhibitors, in addition to an alarming rate of MDR and ESBL-producing strains.

The spread of pESI-mediated extended-spectrum cephalosporin resistance in Salmonella serovars-Infantis, Senftenberg, and Alachua isolated from food animal sources in the United States.

The goal of this study is to investigate the origin, prevalence, and evolution of the pESI megaplasmid in Salmonella isolated from animals, foods, and humans. We queried 510,097 Salmonella genomes under the National Center for Biotechnology Information (NCBI) Pathogen Detection (PD) database for the presence of potential sequences containing the pESI plasmid in animal, food, and environmental sources. The presence of the pESI megaplasmid was confirmed by using seven plasmid-specific markers (rdA, pilL, SogS, TrbA, ipf, ipr2 and IncFIB(pN55391)). The plasmid and chromosome phylogeny of these isolates was inferred from single nucleotide polymorphisms (SNPs). Our search resolved six Salmonella clusters carrying the pESI plasmid. Four were emergent Salmonella Infantis clusters, and one each belonged to serovar Senftenberg and Alachua. The Infantis cluster with a pESI plasmid carrying blaCTX-M-65 gene was the biggest of the four emergent Infantis clusters, with over 10,000 isolates. This cluster was first detected in South America and has since spread widely in United States. Over time the composition of pESI in United States has changed with the average number of resistance genes showing a decrease from 9 in 2014 to 5 in 2022, resulting from changes in gene content in two integrons present in the plasmid. A recent and emerging cluster of Senftenberg, which carries the blaCTX-M-65 gene and is primarily associated with turkey sources, was the second largest in the United States. SNP analysis showed that this cluster likely originated in North Carolina with the recent acquisition of the pESI plasmid. A single Alachua isolate from turkey was also found to carry the pESI plasmid containing blaCTX-M-65 gene. The study of the pESI plasmid, its evolution and mechanism of spread can help us in developing appropriate strategies for the prevention and further spread of this multi-drug resistant plasmid in Salmonella in poultry and humans.

Molecular analysis of multidrug-resistant E. coli in pediatric UTIs: findings from a Nigerian Hospital.

INTRODUCTION: This study aimed to isolate and characterize antibiotic-resistant Escherichia coli from urine samples of children at the Mother and Child Hospital in Ondo State, Nigeria, assessing antibiogram profiling and resistance genes. METHODOLOGY: Three hundred urine samples (158 females, 142 males), aged 3-5 years, were collected, transported on ice, and analyzed bacteriologically. E. coli and Gram-negative bacteria were isolated using Eosin Methylene Blue agar and identified through colony morphology and biochemical tests. Antibiotic susceptibility was determined via Kirby Bauer's disc diffusion, and resistance genes were detected using Polymerase Chain Reaction (PCR). RESULTS: Of the 300 samples, 40 (13.3%) yielded E. coli with varying antibiotic resistance profiles. The highest resistance was against Amoxicillin-clavulanate (87.5%) followed by Ceftriaxone (80%). Susceptibility was observed to Nitrofurantoin, Erythromycin, and Chloramphenicol. Multiple resistance patterns against 3-4 antibiotic classes were recorded, with 12 distinct patterns observed. Eight isolates harbored blaCTX-M gene, while five carried the aac3-IV gene. CONCLUSIONS: The study concluded a high occurrence of E. coli infection and multiple antibiotic resistance in the region. The presence of resistance genes suggests significant economic and health implications, emphasizing prudent antibiotic use under physician guidance to mitigate multiple antibiotic resistance.

Characterization of the diversity of type IV secretion system-encoding plasmids in Acinetobacter.

The multi-drug resistant pathogen Acinetobacter baumannii has gained global attention as an important clinical challenge. Owing to its ability to survive on surfaces, its capacity for horizontal gene transfer, and its resistance to front-line antibiotics, A. baumannii has established itself as a successful pathogen. Bacterial conjugation is a central mechanism for pathogen evolution. The epidemic multidrug-resistant A. baumannii ACICU harbours a plasmid encoding a Type IV Secretion System (T4SS) with homology to the E. coli F-plasmid, and plasmids with homologous gene clusters have been identified in several A. baumannii sequence types. However the genetic and host strain diversity, global distribution, and functional ability of this group of plasmids is not fully understood. Using systematic analysis, we show that pACICU2 belongs to a group of almost 120 T4SS-encoding plasmids within four different species of Acinetobacter and one strain of Klebsiella pneumoniae from human and environmental origin, and globally distributed across 20 countries spanning 4 continents. Genetic diversity was observed both outside and within the T4SS-encoding cluster, and 47% of plasmids harboured resistance determinants, with two plasmids harbouring eleven. Conjugation studies with an extensively drug-resistant (XDR) strain showed that the XDR plasmid could be successfully transferred to a more divergent A. baumanii, and transconjugants exhibited the resistance phenotype of the plasmid. Collectively, this demonstrates that these T4SS-encoding plasmids are globally distributed and more widespread among Acinetobacter than previously thought, and that they represent an important potential reservoir for future clinical concern.

Multilocus sequence typing and antibiotic resistance of Aeromonas isolated from freshwater fish in Hebei Province.

Aeromonas spp. are the opportunistic pathogens that infect both aquatic and terrestrial homeotherms. They were commonly present in aquatic environments, including effluent, tap water, marine, river, and lake, where they are often isolated from aquatic animals, including fish, molluscs, and crustaceans. The Aeromonas infections can cause sepsis, ulcer, and other symptoms, resulting in the death of massive aquatic animals. Therefore, the prevention and control of Aeromonas is of great significance for the healthy development of aquaculture. In this study, we used modern molecular methods to enhance disease control of Aeromonas isolates from freshwater fish in Hebei Province. A total of 130 Aeromonas spp. isolates were isolated from freshwater fish farms in Hengshui, Handan, and Shijiazhuang and all 130 Aeromonas spp. isolates were sequenced for species identification. Of the 130 Aeromonas spp. isolates, 104 isolates were successfully sequenced, and BLAST analysis showed that Aeromonas veronii was predominant in freshwater fish farms in Hebei Province. In addition, 26 antibiotic resistance profiles were obtained from 102 fully cultured isolates among the 104 Aeromonas spp. isolates whose species was primarily identified, and 44 multidrug-resistant bacteria among the 102 isolates were identified using an antibiotic susceptibility test. Using the Multilocus Sequence Typing (MLST) method, 33 out of 44 multidrug-resistant isolates with 14 non-Aeromonas reference strains were selected for phylogenetic and MLST analysis, and all 33 multidrug-resistant isolates were A. veronii. A total of 30 new Sequence Types (STs) were obtained by comparing concatenated sequences (gyrB-groL-gltA-metG-ppsA-recA) on PubMLST website. Furthermore, recombination event analysis detected using RDP5 and ClonalFrameML software 42 and 49 recombination events, respectively, and 22 recombination events were validated by four or more algorithms. Since mutation and recombination events increase clonal diversity and single housekeeping gene sequence alignments are limited for identifying species, we propose the use of multiple concatenated sequence loci to increase discriminatory power. In addition, we propose that the MLST method is an appropriate technique to study and develop the resistance mechanisms of multidrug-resistant Aeromonas and to identify Aeromonas systematically in complex samples obtained from the environment.

Antimicrobial Resistance and the Genomic Epidemiology of Multidrug-Resistant Salmonella enterica serovar Enteritidis ST11 in China.

BACKGROUND: With the recent evolution of multidrug-resistant strains, the genetic characteristics of foodborne Salmonella enterica serovar Enteritidis and clinical isolates have changed. ST11 is now the most common genotype associated with S. Enteritidis isolates. METHODS: A total of 83 strains of S. Enteritidis were collected at the General Hospital of the People's Liberation Army. Of these, 37 were from aseptic sites in patients, 11 were from the feces of patients with diarrhea, and the remaining 35 were of chicken-origin. The minimum inhibitory concentration of S. Enteritidis was determined by the broth microdilution method. Genomic DNA was extracted using the QiAamp DNA Mini Kit, and whole-genome sequencing (WGS) was performed using an Illumina X-ten platform. Prokka was used for gene prediction and annotation, and bioinformatic analysis tools included Resfinder, ISFinder, Virulence Factor Database, and PlasmidFinder. IQ-TREE was used to build a maximum likelihood phylogenetic tree. The phylogenetic relationship and distribution of resistance genes was displayed using iTOL. Comparative population genomics was used to analyze the phenotypes and genetic characteristics of antibiotic resistance in clinical and chicken-origin isolates of S. Enteritidis. RESULTS: The chicken-origin S. Enteritidis isolates were more resistant to antibiotics than clinical isolates, and had a broader antibiotic resistance spectrum and higher antibiotic resistance rate. A higher prevalence of antibiotic-resistance genes was observed in chicken-origin S. Enteritidis compared to clinical isolates, along with distinct patterns in the contextual characteristics of these genes. Notably, genes such as blaCTX-M and dfrA17 were exclusive to plasmids in clinical S. Enteritidis, whereas in chicken-origin S. Enteritidis they were found in both plasmids and chromosomes. Additionally, floR was significantly more prevalent in chicken-origin isolates than in clinical isolates. Careful analysis revealed that the delayed isolation of chicken-origin S. Enteritidis contributes to accelerated gene evolution. Of note, certain resistance genes tend to integrate seamlessly and persist steadfastly within the chromosome, thereby expediting the evolution of resistance mechanisms against antibiotics. Our comparative analysis of virulence genes in S. Enteritidis strains from various sources found no substantial disparities in the distribution of other virulence factors. In summary, we propose that chicken-origin S. Enteritidis has the potential to cause clinical infections. Moreover, the ongoing evolution and dissemination of these drug-resistant genes poses a formidable challenge to clinical treatment. CONCLUSIONS: Constant vigilance is needed to monitor the dynamic patterns of drug resistance in S. Enteritidis strains sourced from diverse origins.

Characteristic SNPs defining the major multidrug-resistant Mycobacterium tuberculosis clusters identified by EuSeqMyTB to support routine surveillance, EU/EEA, 2017 to 2019.

BackgroundThe EUSeqMyTB project, conducted in 2020, used whole genome sequencing (WGS) for surveillance of drug-resistant Mycobacterium tuberculosis in the European Union/European Economic Area (EU/EEA) and identified 56 internationally clustered multidrug-resistant (MDR) tuberculosis (TB) clones.AimWe aimed to define and establish a rapid and computationally simple screening method to identify probable members of the main cross-border MDR-TB clusters in WGS data to facilitate their identification and track their future spread.MethodsWe screened 34 of the larger cross-border clusters identified in the EuSeqMyTB pilot study (2017-19) for characteristic single nucleotide polymorphism (SNP) signatures that could identify and define members of each cluster. We also linked this analysis with published clusters identified in previous studies and identified more distant genetic relationships between some of the current clusters.ResultsA panel of 30 characteristic SNPs is presented that can be used as an initial (routine) screen for members of each cluster. For four of the clusters, no unique defining SNP could be identified; three of these are closely related (within approximately 20 SNPs) to one or more other clusters and likely represent a single established MDR-TB clade composed of multiple recent subclusters derived from the previously described ECDC0002 cluster.ConclusionThe identified SNP signatures can be integrated into routine pipelines and contribute to the more effective monitoring, rapid and widespread screening for TB. This SNP panel will also support accurate communication between laboratories about previously identified internationally transmitted MDR-TB genotypes.

Multi-platform whole genome sequencing for tuberculosis clinical and surveillance applications.

Whole genome sequencing (WGS) of Mycobacterium tuberculosis offers valuable insights for tuberculosis (TB) control. High throughput platforms like Illumina and Oxford Nanopore Technology (ONT) are increasingly used globally, although ONT is known for higher error rates and is less established for genomic studies. Here we present a study comparing the sequencing outputs of both Illumina and ONT platforms, analysing DNA from 59 clinical isolates in highly endemic TB regions of Thailand. The resulting sequence data were used to profile the M. tuberculosis pairs for their lineage, drug resistance and presence in transmission chains, and were compared to publicly available WGS data from Thailand (n = 1456). Our results revealed isolates that are predominantly from lineages 1 and 2, with consistent drug resistance profiles, including six multidrug-resistant strains; however, analysis of ONT data showed longer phylogenetic branches, emphasising the technologies higher error rate. An analysis incorporating the larger dataset identified fifteen of our samples within six potential transmission clusters, including a significant clade of 41 multi-drug resistant isolates. ONT's extended sequences also revealed strain-specific structural variants in pe/ppe genes (e.g. ppe50), which are candidate loci for vaccine development. Despite some limitations, our results show that ONT sequencing is a promising approach for TB genomic research, supporting precision medicine and decision-making in areas with less developed infrastructure, which is crucial for tackling the disease's significant regional burden.

Cell envelope structural and functional contributions to antibiotic resistance in Burkholderia cenocepacia.

Antibiotic activity is limited by the physical construction of the Gram-negative cell envelope. Species of the Burkholderia cepacia complex (Bcc) are known as intrinsically multidrug-resistant opportunistic pathogens with low permeability cell envelopes. Here, we re-examined a previously performed chemical-genetic screen of barcoded transposon mutants in B. cenocepacia K56-2, focusing on cell envelope structural and functional processes. We identified structures mechanistically important for resistance to singular and multiple antibiotic classes. For example, susceptibility to novobiocin, avibactam, and the LpxC inhibitor, PF-04753299, was linked to the BpeAB-OprB efflux pump, suggesting these drugs are substrates for this pump in B. cenocepacia. Defects in peptidoglycan precursor synthesis specifically increased susceptibility to cycloserine and revealed a new putative amino acid racemase, while defects in divisome accessory proteins increased susceptibility to multiple ß-lactams. Additionally, disruption of the periplasmic disulfide bond formation system caused pleiotropic defects on outer membrane integrity and ß-lactamase activity. Our findings highlight the layering of resistance mechanisms in the structure and function of the cell envelope. Consequently, we point out processes that can be targeted for developing antibiotic potentiators.IMPORTANCEThe Gram-negative cell envelope is a double-layered physical barrier that protects cells from extracellular stressors, such as antibiotics. The Burkholderia cell envelope is known to contain additional modifications that reduce permeability. We investigated Burkholderia cell envelope factors contributing to antibiotic resistance from a genome-wide view by re-examining data from a transposon mutant library exposed to an antibiotic panel. We identified susceptible phenotypes for defects in structures and functions in the outer membrane, periplasm, and cytoplasm. Overall, we show that resistance linked to the cell envelope is multifaceted and provides new targets for the development of antibiotic potentiators.

Phylogenomic and phenotypic analyses highlight the diversity of antibiotic resistance and virulence in both human and non-human Acinetobacter baumannii.

Acinetobacter baumannii is a Gram-negative, opportunistic pathogen that causes infections in the immunocompromised. With a high incidence of muti-drug resistance, carbapenem-resistant A. baumannii is designated as a priority 1 pathogen by the WHO. The current literature has expertly characterized clinical isolates of A. baumannii. As the challenge of these infections has recently been classified as a One Health issue, we set out to explore the diversity of isolates from human and non-clinical sources, such as agricultural surface water, urban streams, various effluents from wastewater treatment plants, and food (tank milk); and, importantly, these isolates came from a wide geographic distribution. Phylogenomic analysis considering almost 200 isolates showed that our diverse set is well-differentiated from the main international clones of A. baumannii. We discovered novel sequence types in both hospital and non-clinical settings and five strains that overexpress the resistance-nodulation-division efflux pump adeIJK without changes in susceptibility reflected by this overexpression. Furthermore, we detected a bla ADC-79 in a non-human isolate despite its sensitivity to all antibiotics. There was no significant differentiation between the virulence profiles of clinical and non-clinical isolates in the Galleria mellonella insect model of virulence, suggesting that virulence is neither dependent on geographic origin nor isolation source. The detection of antibiotic resistance and virulence genes in non-human strains suggests that these isolates may act as a genetic reservoir for clinical strains. This endorses the notion that in order to combat multi-drug-resistant infection caused by A. baumannii, a One Health approach is required, and a deeper understanding of non-clinical strains must be achieved.IMPORTANCEThe global crisis of antibiotic resistance is a silent one. More and more bacteria are becoming resistant to all antibiotics available for treatment, leaving no options remaining. This includes Acinetobacter baumannii. This Gram-negative, opportunistic pathogen shows a high frequency of multi-drug resistance, and many strains are resistant to the last-resort drugs carbapenem and colistin. Research has focused on strains of clinical origin, but there is a knowledge gap regarding virulence traits, particularly how A. baumannii became the notorious pathogen of today. Antibiotic resistance and virulence genes have been detected in strains from animals and environmental locations such as grass and soil. As such, A. baumannii is a One Health concern, which includes the health of humans, animals, and the environment. Thus, in order to truly combat the antibiotic resistance crisis, we need to understand the antibiotic resistance and virulence gene reservoirs of this pathogen under the One Health continuum.

Deciphering the molecular and functional basis of TMexCD1: the plasmid-encoded efflux pump of resistance-nodulation-division superfamily.

Horizontal gene transfer has been demonstrated to be an important driver for the emergency of multidrug-resistant pathogens. Recently, a transferable gene cluster tmexCD1-toprJ1 of the resistance-nodulation-division (RND) superfamily was identified in the plasmids of animal-derived Klebsiella pneumoniae strains, with a higher efflux capacity for various drugs than the Escherichia coli AcrAB-TolC homolog system. In this study, we focused on the differences in the inner membrane pump of these two systems and identified some key residues that contribute to the robust efflux activity of the TMexCD1 system. With the aid of homologous modeling and molecular docking, eight residues from the proximal binding pocket (PBP) and nine from the distal binding pocket (DBP) were selected and subjected to site-directed mutagenesis. Several of them, such as S134, I139, D181, and A290, were shown to be important for substrate binding in the DBP region, and all residues in PBP and DBP showed certain substrate preferences. Apart from the conservative switch loop (L613-623TMexD1) previously identified in the E. coli AcrB (EcAcrB), a relatively unconservative loop (L665-675TMexD1) at the bottom of PBP was proposed as a critical element for the robust activity of TMexD1, due to variations at sites E669, G670, N673, and S674 compared to EcAcrAB, and the significantly altered efflux activity due to their mutations. The conservation and flexibility of these key factors can contribute to the evolution of the RND efflux pumps and thus serve as potential targets for developing inhibitors to block the widespread of the TMexCD1 system.