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OBJECTIVE: This study aims to analyze the genomic and clinical characteristics of Non-baumannii Acinetobacter strains misidentified as A. baumannii, causing bloodstream infections (BSIs) in our hospital. MATERIALS AND METHODS: Whole genome sequencing was performed and average nucleotide identity (ANI) was analyzed. Susceptibility testing was conducted using micro-broth methods. The distribution of antimicrobial resistance genes (ARGs) and mobile genetic elements (MGEs) was examined using online software tools. The prevalence of virulence factors (VFs) was investigated through nucleotide coding sequence comparisons. Genetic structures of blaOXA genes were analyzed by Gcluster software. Clinical information was collected from electronic medical records for patient characterization. RESULTS: ANI analysis identified five strains as Acinetobacter pittii, with the remaining four identified as A. geminorum, A. nosocomialis, A. soli and A. bereziniae. The GC content of all isolates was less than 38.9 % except for A. soli 16,294. All Non-baumannii Acinetobacter strains were relatively susceptible to antibiotics, except for one A. pittii isolate. Nine blaOXA variants were identified in seven isolates, with two isolates co-carrying 2 different types of blaOXA. Twenty-four insertion sequences (ISs) were identified, with ISAba and IS17 being the primary ISs. Five A. pittii isolates shared the same genetic structures around blaOXA. Genes related to adherence, immune modulation, and nutritional/metabolic factors were the most frequent. Few VFs were detected in A. soli 16,294 and A.bereziniae 14,325. CONCLUSIONS: The presence of carbapenem hydrolyzing oxacillinase encoding genes did not confer carbapenem resistance, possibly due to the lack of ISs in the blaOXA flanking sequences. Different blaOXA variants within distinct strains shared the same genetic structures, suggesting potential for multidrug resistance development, which warrants our attention.

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Background: The occurrence and dissemination of hypermucoviscous and hypervirulent Klebsiella pneumoniae (hm-hvKp) isolates in clinical settings are a critical public health problem in the world. However, the data on these isolates in community populations are limited. This study aims to understand the prevalence and molecular characteristics of hm-hvKp isolates in community patients in Shanghai, China. Methods: In 2018, an active surveillance system focused on hm-hvKp in community diarrhoeal cases was implemented in Pudong New Area, Shanghai, China, involving 12 sentinel hospitals. The antimicrobial susceptibility of hm-hvKp isolates from fecal samples was tested, and whole-genome sequencing (WGS) was performed to predict the serotypes and sequence types and to identify antimicrobial resistance determinants, virulence determinants, and phylogenetic clusters. Results: The overall prevalence of hm K. pneumoniae isolates was 2.48% (31/1252), with the proportions of 1.76% (22/1252) for hm-hvKp and 0.72% (9/1252) for hm not hv K. pneumoniae. The prevalence of hm-hvKp isolates among different age groups and different months was statistically significant. All the 22 hm-hvKp isolates were susceptible to 20 antimicrobial agents and only carried bla SHV gene, and KL1 and KL2 accounted for eight (36.36%) cases and seven (31.82%) cases, respectively. The eight ST23/KL1 isolates belonged to the predominant CG23-I clade, which typically possessed the virulence determinants profile of rmpA/rmpA2-iro-iuc-ybt-irp-clb. The five ST86/KL2 isolates were assigned to the global clusters ST86/KL2-1 (n=2), ST86/KL2-2 (n=2), ST86/KL2-3 (n=1), all lack of the clb gene. Shanghai ST23/KL1 and ST86/KL2 isolates were closely related to the global isolates from liver abscesses, blood, and urine. Conclusion: Hm-hvKp is carried by the community population of Shanghai, with ST23/KL1 and ST86/KL2 isolates predominant. Hm-hvKp isolates of different continents, different sources, and different virulence levels were closely related. Ongoing surveillance of hm-hvKp isolates in the community population is warranted.

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Globally, the main molecular trials being developed to study the genetic determinants responsible for conferring resistance to bacterial organisms are amplification-based methods, hybridization-based methods, and sequence-based methods. In the specific case of Streptococcus suis, polymerase chain reaction is the only test tuned up until now for detecting resistant clinical isolates to macrolides and/or tetracyclines, the two main groups of antibiotics being ineffective against this human and animal pathogen.

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Campylobacter jejuni and Campylobacter coli are the predominant thermophilic species responsible for foodborne gastroenteritis worldwide. Elevated resistance to certain antibiotics was observed due to antimicrobial therapy in farm animals and humans, while reduced antimicrobial usage partially reduced antibiotic resistance. Monitoring the antimicrobial resistance demonstrated a substantial fraction of multi-resistant isolates, indicating the necessity of reliable tools for their detection. In this study, resistance determinants in 129 German and 21 Vietnamese isolates were selected to establish a novel multiplex real-time PCR (qPCR), facilitating the simultaneous detection of four resistance determinants. These comprised tet(O) gene variants associated with tetracycline resistance, point mutations GyrA_T86I and GyrA_T86V associated with ciprofloxacin resistance, and the erm(B) gene together with the point mutation A2075G in the 23S rRNA gene, associated with erythromycin resistance. Moreover, the performance of the qPCR assay was evaluated by comparing the results of qPCR to phenotypic antimicrobial resistance profiles, obtained with standardized EUCAMP3 microdilution panel, which showed 100% similarity (inclusivity and exclusivity). Variation in measurement methods, including qPCR machines and master mixes showed robustness, essential for laboratories. The assay can be used for the rapid detection of resistance determinants, and is beneficial for monitoring the spread of antibiotic resistance in C. jejuni and C. coli.

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The emergence of carbapenem-resistant Klebsiella pneumoniae poses a significant threat to public health. In this study, we aimed to investigate the distribution and genetic diversity of plasmids carrying beta-lactamase resistance determinants in a collection of carbapenem-resistant K. pneumoniae blood isolates. Blood isolates of carbapenem-resistant K. pneumoniae bacteremia were collected and identified. Whole-genome sequencing, assembly and analysis were performed for the prediction of antimicrobial resistance determinants. Plasmidome analysis was also performed. Our plasmidome analysis revealed two major plasmid groups, IncFII/IncR and IncC, as key players in the dissemination of carbapenem resistance among carbapenem-resistant K. pneumoniae. Notably, plasmids within the same group exhibited conservation of encapsulated genes, suggesting that these plasmid groups may serve as conservative carriers of carbapenem-resistant determinants. Additionally, we investigated the evolution and expansion of IS26 integrons in carbapenem-resistant K. pneumoniae isolates using long-read sequencing. Our findings revealed the evolution and expansion of IS26 structure, which may have contributed to the development of carbapenem resistance in these strains. Our findings indicate that IncC group plasmids are associated with the endemic occurrence of carbapenem-resistant K. pneumoniae, highlighting the need for targeted interventions to control its spread. Although our study focuses on the endemic presence of carbapenem-resistant K. pneumoniae, it is important to note that carbapenem-resistant K. pneumoniae is indeed a global problem, with cases reported in multiple regions worldwide. Further research is necessary to better understand the factors driving the worldwide dissemination of carbapenem-resistant K. pneumoniae and to develop effective strategies for its prevention and control.

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Acidithiobacillus caldus is a common bioleaching bacterium that is inevitably exposed to extreme copper stress in leachates. The ArsR/SmtB family of metalloregulatory repressors regulates homeostasis and resistance in bacteria by specifically responding to metals. Here, we characterized A. caldus Cu(I)-sensitive repressor (AcsR) and gained molecular insights into this new member of the ArsR/SmtB family. Transcriptional analysis indicated that the promoter (PIII) of acsR was highly active in Escherichia coli but inhibited upon AcsR binding to the PIII-acsR region. Size exclusion chromatography and circular dichroism spectra revealed that CuI-AcsR shared an identical assembly state with apo-AcsR, as a dimer with fewer α helices, more extended strands, and more ß turns. Mutation of the cysteine site in AcsR did not affect its assembly state. Copper(I) titrations revealed that apo-AcsR bound two Cu(I) molecules per monomer in vitro with an average dissociation constant (KD) for bicinchoninic acid competition of 2.55 × 10-9 M. Site-directed mutation of putative Cu(I)-binding ligands in AcsR showed that replacing Cys64 with Ala reduces copper binding ability from two Cu(I) molecules per monomer to one, with an average KD of 6.05 × 10-9 M. Electrophoretic mobility shift assays revealed that apo-AcsR has high affinity for the 12-2-12 imperfect inverted repeats P2245 and P2270 in the acsR gene cluster and that Cu-loaded AcsR had lower affinity for DNA fragments than apo-AcsR. We developed a hypothetical working model of AcsR to better understand Cu resistance mechanisms in A. caldus. IMPORTANCE Copper (Cu) resistance among various microorganisms is attracting interest. The chemolithoautotrophic bacterium A. caldus, which can tolerate extreme copper stress (≥10 g/L Cu ions), is typically used to bioleach chalcopyrite (CuFeS2). Understanding of Cu resistance in A. caldus is limited due to scant investigation and the absence of efficient gene manipulation tools. Here, we characterized a new member of the ArsR/SmtB family of prokaryotic metalloregulatory transcriptional proteins that repress operons linked to stress-inducing concentrations of heavy metal ions. This protein can bind two Cu(I) molecules per monomer and negatively regulate its gene cluster. Members of the ArsR/SmtB family have not been investigated in A. caldus until now. The discovery of this novel protein enriches understanding of Cu homeostasis in A. caldus.

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The aim of this work was to study the resistance to macrolides (azithromycin) in the modern Russian population of N. gonorrhoeae with the analysis of genetic resistance determinants. Azithromycin is not used to treat gonococcal infection in Russia. However, among 162 isolates collected in 2020-2021, 22 isolates (13.6%) were phenotypically resistant to azithromycin. Mutations in 23S rRNA genes were found only in two isolates; erm and mefA genes were absent. Azithromycin resistance was shown to be predominantly associated with mutations in the mtrR and mtrD genes of the MtrCDE efflux pump and their mosaic alleles which may have formed due to a horizontal transfer from N. meningitidis. A total of 30 types of mtrR alleles and 10 types of mtrD alleles were identified including mosaic variants. Matching between the mtrR and mtrD alleles was revealed to indicate the cooperative molecular evolution of these genes. A link between the mtrR and mtrD alleles and NG-MAST types was found only for NG-MAST 228 and 807, typical of N. gonorrhoeae in Russia. The high level of resistance to azithromycin in Russia may be related to the spread of multiple transferable resistance to antimicrobials regardless of their use in the treatment of gonococcal infection.

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The high incidence of human salmonellosis and multi-drug resistant (MDR) strains of Salmonella Typhimurium (ST) is of concern to global public and animal health. Our research, by means of the broth microdilution method, evaluated the Minimum Inhibitory Concentration (MIC) distribution of 12 antimicrobials against a collection of 73 ST and mST and S. typhimurium monophasic variant 4,[5],12:i:- (mST) isolates from slaughtered pigs reared in extensive systems in southern Spain, and also 12 resistance-associated genes or antimicrobial resistance (AMR) determinants using qPCR. Our data revealed that 98.6% of strains were MDR, with resistance to cephalothin/tetracycline/sulfamethoxazole-trimethoprim/ampicillin/chloramphenicol being the most common pattern (55.6%). Regarding AMR determinants, the most significantly (p < 0.05) genes detected by qPCR were sul1 and aadA2 (89% of strains positive), aadA1 and dfrA12 (87.7%), and blaTEM and tet(B) (86.3% and 84.9%, respectively). Up to date information on ST antimicrobial resistance patterns is essential for epidemiological surveillance programs to support animal and public health. The high number of MDR isolates and variability regarding resistance determinants revealed in this study highlights the role of animals reared in extensive systems as a source of resistant Salmonella strains.

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The rapidly emerging phenomenon of antibiotic resistance threatens to substantially reduce the efficacy of available antibacterial therapies. Dissemination of resistance, even between phylogenetically distant bacterial species, is mediated mainly by mobile genetic elements, considered to be natural vectors of horizontal gene transfer. Transposable elements (TEs) play a major role in this process-due to their highly recombinogenic nature they can mobilize adjacent genes and can introduce them into the pool of mobile DNA. Studies investigating this phenomenon usually focus on the genetic load of transposons and the molecular basis of their mobility. However, genes introduced into evolutionarily distant hosts are not necessarily expressed. As a result, bacterial genomes contain a reservoir of transcriptionally silent genetic information that can be activated by various transposon-related recombination events. The TEs themselves along with processes associated with their transposition can introduce promoters into random genomic locations. Thus, similarly to integrons, they have the potential to convert dormant genes into fully functional antibiotic resistance determinants. In this review, we describe the genetic basis of such events and by extension the mechanisms promoting the emergence of new drug-resistant bacterial strains.

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Sewage treatment plants are an essential source of antibiotics, antibiotic resistance determinants, and bacteria in environmental waters. However, it is still unclear whether they can maintain a relatively stable relationship in wastewater and environmental waters. This study analyzed the removal capacity of the above three pollutants in the sewage treatment plant in summer and their impact on environmental waters, and then examines the relationship between the three contaminants in the wastewater and environmental waters in summer and winter based on our previous study. The results found that the removal capacity of bacteria in summer was poor, the concentration of fluoroquinolone in the effluent was higher than that in influent, and the abundance of intI1, tetW, qnrB, and ermB increased after wastewater treatment. Proteobacteria and Bacteroides were the main bacteria that constitute the correlation network between bacteria, and they existed stably in summer and winter. However, fluoroquinolones occupied a significant position in the determinant network of antibiotics and antibiotic resistance in summer and winter. There are fewer correlation between antibiotics and antibiotics resistance determinants in winter. Interestingly, the relationship between bacteria, antibiotics, and antibiotic resistance determinants was a mainly positive correlation in summer and negative correlation in winter. This study analyzed the relationship between bacteria, antibiotics, and antibiotic resistance determinants that were stable in the wastewater and environmental waters and pointed out the direction for subsequent targeted seasonal control of novel pollutants in wastewater and environmental waters.

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BACKGROUND: Thermo-tolerant Campylobacter species are the major cause of foodborne diseases worldwide. This study aimed to evaluate the prevalence of virulence genes and antibiotic resistance determinants in Campylobacter jejuni and Campylobacter coli isolates, and to investigate the relationship between these two traits. METHODS: A total of 132 Campylobacter isolates from poultry were tested for the presence of 13 virulence genes; flaA, cadF, racR, virB11, pldA, dnaJ, cdtA, cdtB, cdtC, ciaB, wlaN, cgtB and ceuE. The mechanisms underlying antibiotic resistance phenotypes were also studied by PCR and MAMA-PCR. RESULTS: PCR results revealed the presence of antimicrobial resistance genes in C. jejuni and C. coli as follows: cmeB (80% and 100%), tet(O) (100% and 80%), and the blaOXA-61 (81% and 93%), respectively. None of these strains harbored the aphA-3 gene. The Thr-86-Ile mutation associated with resistance to quinolones was found in 90% of C. jejuni and 80% of C. coli isolates. While the A2075G and A2074C mutations linked to the erythromycin resistance were detected in 100% of both species. Virulence genes were prevalent and ranged from 40 to 100%. A positive relationship was revealed between cadF, racR, and ciaB genes and resistance to ampicillin, amoxicillin/clavulanic acid, chloramphenicol, and nalidixic acid, in C. jejuni. However, no association was observed for C. coli isolated strains. CONCLUSION: This study provides for the first time an overview of antibiotic resistance mechanisms and pathogenic profiles of Campylobacter isolates, which emphasizes the potential risk for consumer health.

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Introduction. Shiga toxin-producing Escherichia coli (STEC) can cause severe to fatal disease in humans. Antimicrobial treatment is sometimes necessary, but contraindicated due to undesirable clinical outcome. However, recent studies have shown promising outcomes following antimicrobial treatment. Before the establishment of a possible antimicrobial treatment strategy for STEC infections, the prevalence of antimicrobial resistance in STEC needs to be determined.Gap Statement. The resistance status of Norwegian clinical STEC is not known and should be assessed.Aim. We aim to characterize genotypic antimicrobial resistance determinants in clinical STEC in Norway, and determine the prevalence of genotypic resistance in order to inform possible antimicrobial treatment options for STEC infections.Methodology. We included all clinical STEC submitted to the Norwegian Reference Laboratory from March 2018 to April 2020. All samples were whole-genome sequenced and screened for genotypic antimicrobial resistance,virulence determinants and plasmid incompatibility groups. We performed phylogenetic clustering of STEC by core-genome multi-locus sequence typing, and statistical association analyses between isolate characteristics and genotypic resistance.Results. A total of 459 STEC were analysed. For 385 (83.9 %) STEC we did not identify any antimicrobial resistance determinants. Seventy-four STEC (16.1 %) harboured antimicrobial resistance determinants against one or more antimicrobial classes. The most frequent genotypic resistance was identified against aminoglycosides (10.5 %). Thirty-nine STEC (8.5 %) had a multi-drug resistance (MDR) genotype. Genotypic resistance was more prevalent in non-O157 than O157 STEC (P=0.02). A positive association was seen between genotypic resistance and the low-virulent STEC O117:H7 phylogenetic cluster (no. 14) (P<0.001). Genotypic resistance was not significantly associated to high-virulent STEC. STEC O146:H28 and isolates harbouring the plasmid replicon type IncQ1 were positively associated with MDR.Conclusion. The overall prevalence of genotypic resistance in clinical STEC in Norway is low (16.1 %). Genotypic resistance is more prevalent in non-O157 strains compared to O157 strains, and not significantly associated to high-virulent STEC. Resistance to antimicrobials suggested for treatment, especially azithromycin is low and may present an empiric treatment alternative for severe STEC infections.

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A multiplex assay based on a low-density hydrogel microarray was developed to identify genomic substitutions in N. gonorrhoeae that determine resistance to the currently recommended treatment agents ceftriaxone and azithromycin and the previously used drugs penicillin, tetracycline, and ciprofloxacin. The microarray identifies 74 drug resistance determinants in the N. gonorrhoeae penA, ponA, porB, gyrA, parC, rpsJ, mtrR, blaTEM, tetM, and 23S rRNA genes. The hydrogel elements were formed by automated dispensing of nanoliter-volume droplets followed by UV-induced copolymerization of NH2-containing oligonucleotides with gel-forming monomers. Polybutylene terephthalate plates without special modifications were used as microarray substrates. Sequences and concentrations of immobilized oligonucleotides, gel composition, and hybridization conditions were carefully selected, and the median discrimination ratio ranged from 2.8 to 29.4, allowing unambiguous identification of single-nucleotide substitutions. The mutation identification results in a control sample of 180 N. gonorrhoeae isolates were completely consistent with the Sanger sequencing results. In total, 648 clinical N. gonorrhoeae isolates obtained in Russia during the last 5 years were analyzed and genotyped using these microarrays. The results allowed us to draw conclusions about the present situation with antimicrobial susceptibility of N. gonorrhoeae in Russia and demonstrated the possibility of using hydrogel microarrays to control the spread of antibiotic resistance.

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The spread of resistance to antibiotics is a major health concern worldwide due to the increasing rate of isolation of multidrug resistant pathogens hampering the treatment of infections. The food chain has been recognized as one of the key routes of antibiotic resistant bacteria transmission between animals and humans. Considering that lactic acid bacteria (LAB) could act as a reservoir of transferable antibiotic resistance genes, LAB strains intended to be used as feed additives should be monitored for their safety. Sixty-five LAB strains which might be potentially used as probiotic feed additives or silage inoculants, were assessed for susceptibility to eight clinically relevant antimicrobials by a minimum inhibitory concentration determination. Among antimicrobial resistant strains, a prevalence of selected genes associated with the acquired resistance was investigated. Nineteen LAB strains displayed phenotypic resistance to one antibiotic, and 15 strains were resistant to more than one of the tested antibiotics. The resistance to aminoglycosides and tetracyclines were the most prevalent and were found in 37 and 26% of the studied strains, respectively. Phenotypic resistance to other antimicrobials was found in single strains. Determinants related to resistance phenotypes were detected in 15 strains as follows, the aph(3″)-IIIa gene in 9 strains, the lnu(A) gene in three strains, the str(A)-str(B), erm(B), msr(C), and tet(M) genes in two strains and the tet(K) gene in one strain. The nucleotide sequences of the detected genes revealed homology to the sequences of the transmissible resistance genes found in lactic acid bacteria as well as pathogenic bacteria. Our study highlights that LAB may be a reservoir of antimicrobial resistance determinants, thus, the first and key step in considering the usefulness of LAB strains as feed additives should be an assessment of their antibiotic resistance. This safety criterion should always precede more complex studies, such as an assessment of adaptability of a strain or its beneficial effect on a host. These results would help in the selection of the best LAB strains for use as feed additives. Importantly, presented data can be useful for revising the current microbiological cut-off values within the genus Lactobacillus and Pediococcus.

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The copper-sensitive operon repressor (CsoR) family, which is the main Cu(I)-sensing family, is widely distributed and regulates regulons involved in detoxification in response to extreme copper stress (a general range of ≥3 g/liter copper ions). Here, we identified CsoR in hyper-copper-resistant Acidithiobacillus caldus (CsoRAc), an organism used in the bioleaching process of copper ores. CsoRAc possesses highly conserved Cu(I) ligands and structures within the CsoR family members. Transcriptional analysis assays indicated that the promoter (PIII) of csoR was active but weakly responsive to copper in Escherichia coli. Copper titration assays gave a stoichiometry of 0.8 mol Cu(I) per apo-CsoRAc monomer in vitro combined with atomic absorption spectroscopy analysis. CuI-CsoRAc and apo-CsoRAc share essentially identical secondary structures and assembly states, as demonstrated by circular dichroism spectra and size exclusion chromatography profiles. The average dissociation constants (KD = 2.26 × 10-18 M and 0.53 × 10-15 M) and Cu(I) binding affinity of apo-CsoRAc were estimated by bathocuproine disulfonate (BCS) and bicinchoninic acid (BCA) competition assays, respectively. Site-directed mutations of conserved Cu(I) ligands in CsoRAc did not significantly alter the secondary structure or assembly state. Competition assays showed that mutants had the same order of magnitude of Cu(I) binding affinity as apo-CsoRAc. Moreover, apo-CsoRAc could bind to the DNA fragment P08430 in vitro, although with low affinity. Finally, a working model was developed to illustrate putative copper resistance mechanisms in A. caldus. IMPORTANCE Research on copper resistance among various species has attracted considerable interest. However, due to the lack of effective and reproducible genetic tools, few studies regarding copper resistance have been reported for A. caldus. Here, we characterized a major Cu(I)-sensing family protein, CsoRAc, which binds Cu(I) with an attomolar affinity higher than that of the Cu(I)-specific chelator bathocuproine disulfonate. In particular, CsoR family proteins were identified only in A. caldus, rather than A. ferrooxidans and A. thiooxidans, which are both used for bioleaching. Meanwhile, A. caldus harbored more copper resistance determinants and a relatively full-scale regulatory system involved in copper homeostasis. These observations suggested that A. caldus may play an essential role in the application of engineered strains with higher copper resistance in the near future.

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Staphylococcus saprophyticus is a common pathogen of the urinary tract, a heavy metal-rich environment, but information regarding its heavy metal resistance is unknown. We investigated 422 S. saprophyticus isolates from human infection and colonization/contamination, animals, and environmental sources for resistance to copper, zinc, arsenic, and cadmium using the agar dilution method. To identify the genes associated with metal resistance and assess possible links to pathogenicity, we accessed the whole-genome sequence of all isolates and used in silico and pangenome-wide association approaches. The MIC values for copper and zinc were uniformly high (1,600 mg/liter). Genes encoding copper efflux pumps (copA, copB, copZ, mco, and csoR) and zinc transporters (zinT, czrAB, znuBC, and zur) were abundant in the population (20 to 100%). Arsenic and cadmium showed various susceptibility levels. Genes encoding the ars operon (arsRDABC), an ABC transporter and a two-component permease, were linked to resistance to arsenic (MICs ≥ 1,600 mg/liter; 14% [58/422]; P < 0.05). At least three cad genes (cadA or cadC and cadD-cadX or czrC) and genes encoding multidrug efflux pumps and hyperosmoregulation in acidified conditions were associated with resistance to cadmium (MICs ≥ 200 mg/liter; 20% [85/422]; P < 0.05). These resistance genes were frequently carried by mobile genetic elements. Resistance to arsenic and cadmium were linked to human infection and a clonal lineage originating in animals (P < 0.05). Altogether, S. saprophyticus was highly resistant to heavy metals and accumulated multiple metal resistance determinants. The highest arsenic and cadmium resistance levels were associated with infection, suggesting resistance to these metals is relevant for S. saprophyticus pathogenicity.

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OBJECTIVES: The purpose of this study was to investigate the distribution pattern of genes responsible for erythromycin and tetracycline resistance and their association with resistance phenotypes in enterococcus isolates. MATERIALS AND METHODS: Eighty-six Enterococcus faecalis and 26 E. faecium isolates were collected from 2 hospitals in Kerman, Iran. Minimum inhibitory concentration of erythromycin and tetra-cycline was determined and then genes encoding resistance to erythromycin - erm (A-C), mef, and msr - and tetracycline - tet (M), tet (O), tet (S), tet (K), and tet (L) - were investigated. RESULTS: In all resistant isolates (n = 72, 64%), high-level resistance to both tested antibiotics was found. The most prevalent erm gene was erm (B) (77.7%), followed by erm (A) (15.2%) and erm (C) (8.3%). Genes mediating erythromycin efflux were detected in 70.8% (mef) and 9.7% (msr) of resistant isolates. Regarding tetracycline, tet (M) was detected at the highest rate (50%), followed by tet (O) (31%) and tet (S) (11%). Export of tetracycline was found in 31% (tet (K)) and 12% (tet (L)) of isolates. CONCLUSION: A high prevalence of high-level resistance to both erythromycin and tetracycline was documented. Alterations at the ribosomal level was more frequently detected in erythromycin and tetracycline resistance than efflux systems. Concurrent resistance mechanisms were more involved in resistance to erythromycin than tetracycline.

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The problem of antimicrobial-resistant bacteria has not been adequately explored in the tropical island environment. To date, there has not been a systematic investigation into the prevalence and distribution of antimicrobial resistance determinants in the Hawaiian Islands. Urinary isolates are the most common bacterial pathogens encountered in the clinical laboratory. Therefore, the antimicrobial resistance determinant profiles of these organisms can serve as a sentinel of the overall antimicrobial resistance situation in a localized patient population. In this study, 82 clinical isolates of Escherichia coli derived from 82 distinct patients were collected at a large medical center on the island of O'ahu. Each isolate was evaluated for the presence of antimicrobial resistance genes using a microarray-based approach. A total of 36 antimicrobial resistance genes covering 10 classes of antimicrobial compounds were identified. Most isolates were found to harbor between 3 and 5 antimicrobial resistance genes. Only a few isolates were found to harbor more than 12 genes. Significantly, a high rate of phenotypic resistance to one of the first-line treatments for uncomplicated urinary tract infection (sulfamethoxazole) was identified. This phenotype was correlated to the presence of sulfonamides and trimethoprim resistance determinants. Since E. coli is one of the most encountered pathogens in the hospital environment, the presence of clinically relevant resistance determinants in isolates of this organism from a clinical setting on O'ahu is a significant finding that warrants further investigation.

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BACKGROUND: Group B Streptococcus (GBS) is a leading cause of neonatal sepsis and meningitis and an important cause of invasive infections in pregnant and nonpregnant adults. Vaccines targeting capsule polysaccharides and common proteins are under development. METHODS: Using whole genome sequencing, a validated bioinformatics pipeline, and targeted antimicrobial susceptibility testing, we characterized 6340 invasive GBS isolates recovered during 2015-2017 through population-based Active Bacterial Core surveillance (ABCs) in 8 states. RESULTS: Six serotypes accounted for 98.4% of isolates (21.8% Ia, 17.6% V, 17.1% II, 15.6% III, 14.5% Ib, 11.8% IV). Most (94.2%) isolates were in 11 clonal complexes (CCs) comprised of multilocus sequence types identical or closely related to sequence types 1, 8, 12, 17, 19, 22, 23, 28, 88, 452, and 459. Fifty-four isolates (0.87%) had point mutations within pbp2x associated with nonsusceptibility to 1 or more ß-lactam antibiotics. Genes conferring resistance to macrolides and/or lincosamides were found in 56% of isolates; 85.2% of isolates had tetracycline resistance genes. Two isolates carrying vanG were vancomycin nonsusceptible (minimum inhibitory concentration = 2 µg/mL). Nearly all isolates possessed capsule genes, 1-2 of the 3 main pilus gene clusters, and 1 of 4 homologous alpha/Rib family determinants. Presence of the hvgA virulence gene was primarily restricted to serotype III/CC17 isolates (465 isolates), but 8 exceptions (7 IV/CC452 and 1 IV/CC17) were observed. CONCLUSIONS: This first comprehensive, population-based quantitation of strain features in the United States suggests that current vaccine candidates should have good coverage. The ß-lactams remain appropriate for first-line treatment and prophylaxis, but emergence of nonsusceptibility warrants ongoing monitoring.

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We characterized by whole-genome sequencing (WGS) six carbapenem-resistant Acinetobacter baumannii strains isolated from a Brazilian tertiary hospital during a 14-day period. The ISAba1-blaOXA-23 structure was found in the chromosome of five isolates, whereas blaOXA-72 was inserted in a 16.6-kb plasmid in two isolates. The presence of ISAba1-blaADC-like justified the high broad-spectrum cephalosporins minimal inhibitory concentrations (MICs) (MIC50, > 512 mg/L) verified in all isolates. Only minocycline (MIC50, ≤ 0.5 µg/mL), polymyxin B (MIC50, 0.5 µg/mL), and tigecycline (MIC50, 0.5 µg/mL) were in vitro active against such isolates. A diversity of other antimicrobial resistance determinants (aph(3')-VIa, aadA1, aac(3')-IIa, strA, strB, sul2, drfA1, mph(E), msr(E), tetB, and floR) was also observed, which may confer resistance to at last six distinct antimicrobial classes. Four distinct pulsed-field gel electrophoresis (PFGE) profiles were observed during the study period, which belonged to ST79/ST258 (n = 2; IC5), ST25/ST229 (n = 2; IC7), ST1 (n = 1; IC1), and ST162/ST235 (n = 1; IC4). Although the ST1 isolate that carried blaOXA-23 and blaOXA-72 was introduced in this hospital setting by a transferred patient, two clonally related ST79/ST258 isolates carrying either one of these carbapenemase encoding genes were recovered from two patients who were hospitalized within the same period of time in the same hospital unit. Finally, a good correlation between PFGE/MLST, blaOXA-51 variant, and single nucleotide polymorphisms was also observed. Here we demonstrated that distinct extensively drug-resistant A. baumannii clones can circulate in the same hospital setting during a short time period, illustrating a very complex epidemiological scenario for this priority pathogen.

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