Florfenicol Resistance in Enterobacteriaceae and Whole-Genome Sequence Analysis of Florfenicol-Resistant Leclercia adecarboxylata Strain R25. - Related Documents




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542101.0000Florfenicol Resistance in Enterobacteriaceae and Whole-Genome Sequence Analysis of Florfenicol-Resistant Leclercia adecarboxylata Strain R25. Due to inappropriate use, florfenicol resistance is becoming increasingly serious among animal respiratory tract and gut bacteria. To detect the florfenicol resistance mechanism among Enterobacteriaceae bacteria, 292 isolates from animal feces were examined. The agar dilution method was conducted to determine the minimum inhibitory concentration (MIC) for florfenicol, and polymerase chain reaction (PCR) was performed to detect florfenicol resistance genes. To further explore the molecular mechanism of florfenicol resistance, the whole-genome Leclercia adecarboxylata R25 was sequenced. Of the strains tested, 61.6% (180/292) were resistant to florfenicol, 64.4% (188/292) were positive for floR, and 1.0% (3/292) for cfr. The whole-genome sequence analysis of L. adecarboxylata R25 revealed that the floR gene is carried by a transposon and located on a plasmid (pLA-64). Seven other resistance genes are also encoded on pLA-64, all of which were found to be related to mobile genetic elements. The sequences sharing the greatest similarities to pLA-64 are the plasmids p02085-tetA of Citrobacter freundii and p234 and p388, both from Enterobacter cloacae. The resistance gene-related mobile genetic elements also share homologous sequences from different species or genera of bacteria. These findings indicate that floR mainly contributes to the high rate of florfenicol resistance among Enterobacteriaceae. The resistance gene-related mobile genetic elements encoded by pLA-64 may be transferred among bacteria of different species or genera, resulting in resistance dissemination.201931662959
203510.9997In Vitro Susceptibility and Florfenicol Resistance in Citrobacter Isolates and Whole-Genome Analysis of Multidrug-Resistant Citrobacter freundii. The genus Citrobacter is an opportunistic pathogen causing infections in animals, and the published data for its resistance to florfenicol are scarce. In this study, we investigated the antimicrobial susceptibility and molecular characteristics of florfenicol resistance genes among Citrobacter isolates from animal and relevant environmental samples and conducted a comparative analysis of a multidrug-resistant Citrobacter freundii strain isolated from a rabbit. Among 20 Citrobacter strains isolated from animal samples, resistance was most commonly observed to ampicillin (100%), tetracycline (75%), streptomycin (65%), florfenicol (60%), chloramphenicol (60%), and aztreonam (50%), while all the strains found in environmental samples were resistant to few antibiotics. The florfenicol resistance gene floR was detected in 12 isolates (48%, 12/25) from animal samples, and all of the floR-positive isolates were resistant to florfenicol with minimum inhibitory concentration (MIC) values ≥256 μg/mL. Sequencing and comparative analysis of the plasmids from a multidrug-resistant C. freundii isolate named R47 showed that the floR-containing region in the plasmid pR47-54 was a truncated transposon-like structure and could be found on both plasmids and chromosomes of bacteria of either animal or human origin. Furthermore, a range of antimicrobial and metal resistance genes associated with mobile genetic elements could be identified in pR47-54 and the other plasmid pR47-309 of C. freundii R47. These results provide in-depth views into the phenotypic and molecular characteristics of Citrobacter isolates recovered from animal and relevant environmental samples, as well as highlight the role horizontal gene transfer plays in the dissemination of plasmid-encoded resistance genes.201931828082
545720.9996Persistence of transferable oxazolidinone resistance genes in enterococcal isolates from a swine farm in China. The appearance of transferable oxazolidinone resistance genes poses a major challenge to public health and environmental safety. These genes not only lead pathogenic bacteria to become resistant to linezolid but also reduce sensitivity to florfenicol, which is widely used in the veterinary field. To verify the dissemination of oxazolidinone resistance genes in enterococcal isolates from pigs at different production stages in a swine farm in China, we collected 355 enterococcal isolates that were resistant to florfenicol from 600 (150 per stage) fresh fecal swabs collected from a swine farm. Through initial PCR screening and whole-genome sequencing, 175 isolates harboring different oxazolidinone resistance genes were identified. All isolates carried the optrA gene. A total of 161 (92%, 161/175) isolates carried only the optrA gene. Three (1.71%, 3/175) isolates carried both the optrA and poxtA genes, and 11 (3.1%, 11/175) isolates contained the optrA gene and poxtA2 and cfr(D) variants. A total of 175 isolates that harbored oxazolidinone resistance genes included 161 E. faecalis, 6 E. faecium, and 8 E. hirae. By sequencing the whole genomes, we found that the 161 isolates of E. faecalis belonged to 28 different STs, including 8 new STs, and the 6 isolates of E. faecium belonged to four different STs, including one new ST. The phylogenetic tree based on SNPs of the core genome showed that both clonal spread and horizontal transfer mediated the diffusion of oxazolidone resistance genes in enterococcal isolates at specific stages in pig farms. Moreover, enterococcal isolates carrying oxazolidone resistance genes could spread from breeding pigs to fattening pigs, while transferable oxazolidone resistance genes in enterococcal isolates could persist on a pig farm throughout all production stages. Representative enterococcal isolates with different oxazolidinone resistance genes were further studied through Nanopore sequencing. We identified a novel plasmid, pM4-80 L4 (15,008 bp), carrying the poxtA2 and cfr(D) genes in enterococcal isolates at different stages. We also found three different plasmids harboring the poxtA gene with high genetic variation, and all poxtA genes were flanked by two copies of IS1216E elements. In addition, four genetically distinct plasmids carrying the optrA gene were identified, and Tn554 was found to mediate chromosome-localized optrA gene transfer. Our study highlighted that transferable oxazolidinone resistance genes in enterococcal isolates could persist throughout all production stages on a pig farm, and the prevalence and dissemination of oxazolidinone resistance genes in enterococcal isolates from animal farms should be continually monitored.202236299730
205330.9996Replicon typing of plasmids in environmental Achromobacter sp. producing quinolone-resistant determinants. This study aimed to investigate the antimicrobial resistance profile to quinolones, the presence of quinolone-resistant determinants and the plasmid replicon typing in environmental Achromobacter sp. isolated from Brazil. Soil and water samples were used for bacterial isolation. The antimicrobial susceptibility testing was performed by minimum inhibitory concentration method. The detection of mutations in the quinolone resistance-determining regions (QRDR) genes, the presence of plasmid-mediated quinolone resistance (PMQR) genes, and plasmid replicons were performed by PCR. A total of 16 isolates was obtained from different cultures, cities, and states of Brazil. All isolates were non-susceptible to ciprofloxacin, norfloxacin, and levofloxacin. Some mutations in QRDR genes were found, including Gln-83-Leu and Asp-87-Asn in the gyrA and Gln-80-Ile and Asp-84-Ala in the parC. Different PMQR genes were detected, such as qnrA, qnrB, qnrS, oqxA, and oqxB. Three different plasmid families were detected, being most presented the ColE-like, followed by IncFIB and IncA/C. The presence of different PMQR genes and plasmids in the isolates of the present study shows that environmental bacteria can act as reservoir of important genes of resistance to fluoroquinolones, which is of great concern, due to the potential of horizontal dissemination of these genes. Besides that, there are no studies reporting these results in Achromobacter sp. isolates.201830357960
292240.9996Tetracycline-resistance genes in gram-negative isolates from estuarine waters. AIMS: To investigate the diversity and dissemination of tetracycline resistance genes in isolates from estuarine waters. METHODS AND RESULTS: Forty-two out of 164 multi-resistant isolates previously obtained were resistant or less-susceptible to tetracycline, as evaluated by the disc diffusion method. Minimal inhibitory concentration for resistant bacteria ranged from 16 to 256 mg l(-1). Screening of tet genes by polymerase chain reaction showed that 88% of the isolates carried at least one of the genes tested, namely tet(A) (present in 13 isolates), tet(B) (present in 13 isolates), tet(C) (present in 3 isolates), tet(D) (present in 1 isolate), tet(E) (present in 6 isolates) and tet(M) (present in 1 isolate). One isolate carried tet(A) and tet(M). To our knowledge, this study presents the first description of a tet(D) gene in Morganella morganii. Hybridization revealed that tet genes were plasmid-located in 31% of the isolates. Those isolates were included as donors in conjugation experiments and 38% transferred tetracycline resistance. CONCLUSIONS: A considerable diversity of tet genes was detected in the estuary. Frequently, these genes were associated with plasmids and could be transferred to Escherichia coli. SIGNIFICANCE AND IMPACT OF THE STUDY: The results presented provide further evidence of the role played by estuarine reservoirs in antibiotic resistance maintenance and dissemination.200819120920
290650.9996The mef(A) gene predominates among seven macrolide resistance genes identified in gram-negative strains representing 13 genera, isolated from healthy Portuguese children. Of the 176 randomly selected, commensal, gram-negative bacteria isolated from healthy children with low exposure to antibiotics, 138 (78%) carried one or more of the seven macrolide resistance genes tested in this study. These isolates included 79 (91%) isolates from the oral cavity and 59 (66%) isolates from urine samples. The mef(A) gene, coding for an efflux protein, was found in 73 isolates (41%) and was the most frequently carried gene. The mef(A) gene could be transferred from the donors into a gram-positive E. faecalis recipient and a gram-negative Escherichia coli recipient. The erm(B) gene transferred and was maintained in the E. coli transconjugants but was found in 0 to 100% of the E. faecalis transconjugants tested, while the other five genes could be transferred only into the E. coli recipient. The individual macrolide resistance genes were identified in 3 to 12 new genera. Eight (10%) of the oral isolates and 30 (34%) of the urine isolates for which the MICs were 2 to >500 microg of erythromycin per ml did not hybridize with any of the seven genes and may carry novel macrolide resistance genes.200415328110
206460.9996Co-spread of metal and antibiotic resistance within ST3-IncHI2 plasmids from E. coli isolates of food-producing animals. Concerns have been raised in recent years regarding co-selection for antibiotic resistance among bacteria exposed to heavy metals, particularly copper and zinc, used as growth promoters for some livestock species. In this study, 25 IncHI2 plasmids harboring oqxAB (20/25)/blaCTX-M (18/25) were found with sizes ranging from ∼260 to ∼350 kb and 22 belonged to the ST3-IncHI2 group. In addition to blaCTX-M and oqxAB, pcoA-E (5/25) and silE-P (5/25), as well as aac(6')-Ib-cr (18/25), floR (16/25), rmtB (6/25), qnrS1(3/25) and fosA3 (2/25), were also identified on these IncHI2 plasmids. The plasmids carried pco and sil contributed to increasing in the MICs of CuSO4 and AgNO3. The genetic context surrounding the two operons was well conserved except some variations within the pco operon. The ~32 kb region containing the two operons identified in the IncHI2 plasmids was also found in chromosomes of different Enterobacteriaceae species. Further, phylogenetic analysis of this structure showed that Tn7-like transposon might play an important role in cross-genus transfer of the sil and pco operons among Enterobacteriaceae. In conclusion, co-existence of the pco and sil operons, and oqxAB/blaCTX-M as well as other antibiotic resistance genes on IncHI2 plasmids may promote the development of multidrug-resistant bacteria.201627143648
205570.9996Prevalence and characterization of plasmid-mediated quinolone resistance genes in Salmonella isolated from poultry in Korea. The purpose of this study was to investigate the prevalence and characteristics of plasmid-mediated quinolone resistance (PMQR) genes qnr, aac(6')-Ib-cr, and qepA in a total of 185 non-duplicate Salmonella spp. isolated from hatcheries, poultry farms, and poultry slaughterhouses during the period 2001 to 2010 in Korea. Additionally, mutation analysis of quinolone resistance determining regions (QRDRs), conjugation experiments, and plasmid analysis were performed in the PMQR-positive isolates. Among the 185 isolates, six (3.2%) contained qnr genes (two qnrB4 and four qnrS1) but none carried the aac(6')-Ib-cr or qepA genes. Among the six PMQR-positive isolates, one showed a single mutation (Ser83-Phe substitution) in the QRDRs of gyrA. Among them, three were non-susceptible (intermediate or resistant) to nalidixic acid (minimum inhibitory concentration [MIC] ≥256 µg/ml), ciprofloxacin (MIC 2 µg/ml), and levofloxacin (MIC 4 µg/ml), but others were susceptible to all of the three fluoroquinolones. They were resistant to six or more antimicrobial agents tested and were able to transfer quinolone resistance to recipient Escherichia coli J53 by conjugation. By performing a hybridization test, plasmids harbouring qnrB4 and qnrS1 genes were less than 8 kb and about 70 kb in size, respectively. The horizontal dissemination of qnrS1 gene was mediated by IncN plasmid. Compared with the recipient strain, MICs of the transconjugants increased two-fold to four-fold for nalidixic acid, and eight-fold to 16-fold for ciprofloxacin and levofloxacin. This report is the first to describe the detection of qnr genes in Salmonella spp. isolated from poultry in Korea. Widespread horizontal transfer of these genes among bacteria may be a serious public health concern because these can rapidly increase fluoroquinolone resistance. To ensure the public health, it is essential to continuously survey and carefully monitor the spread of PMQR genes in Salmonella from poultry.201323607509
542580.9996The novel mef(C)-mph(G) macrolide resistance genes are conveyed in the environment on various vectors. BACKGROUND: The novel tandem genes mef(C) and mph(G) have been reported in marine bacteria in Japan. This paper aimed to characterise the extent of environmental distribution of mef(C) and mph(G) as well as their dissemination and persistence in aquatic bacterial communities. METHODS: Erythromycin-resistant bacteria were isolated from Japan, Taiwan and Thailand aquaculture sites. The mef(C)-mph(G) genes were detected by PCR. The size of mobile genetic elements conveying mef(C) and mph(G) was examined by Southern blotting. The conjugation rate was assessed by filter mating. RESULTS: The mef(C)-mph(G) tandem genes were distributed in erythromycin-resistant isolates from aquaculture seawater in Japan and northern Taiwan and in animal farm wastewater in Thailand. A total of 29 bacterial isolates were positive for mef(C)-mph(G). The genes were found on vectors of various sizes. Partial sequencing of the traI relaxase gene revealed homology with a pAQU1-like plasmid, an IncA/C-type plasmid and an SXT/R391 family integrative conjugative element (SRI) as vectors. Thirteen isolates (45%) were positive for traI(pAQU-IncA/C-SRI), whereas the others were negative. The traI(pAQU-IncA/C-SRI)-positive isolates exhibited a higher transfer frequency (10(-4)-10(-5) transconjugants/donor) than traI(pAQU-IncA/C-SRI)-negative isolates (<10(-9)). CONCLUSIONS: These results suggest that mef(C)-mph(G) are coded on various vectors and are distributed among marine and wastewater bacteria in Asian countries. Vectors with traI(pAQU-IncA/C-SRI) play a role in the spread of mef(C)-mph(G).201728689921
542290.9996Analysis of Resistance to Florfenicol and the Related Mechanism of Dissemination in Different Animal-Derived Bacteria. Bacterial resistance to antibiotics has become an important concern for public health. This study was aimed to investigate the characteristics and the distribution of the florfenicol-related resistance genes in bacteria isolated from four farms. A total of 106 florfenicol-resistant Gram-negative bacilli were examined for florfenicol-related resistance genes, and the positive isolates were further characterized. The antimicrobial sensitivity results showed that most of them (100, 94.33%) belonged to multidrug resistance Enterobacteriaceae. About 91.51% of the strains carried floR gene, while 4.72% carried cfr gene. According to the pulsed-field gel electrophoresis results, 34 Escherichia coli were subdivided into 22 profiles, the genetic similarity coefficient of which ranged from 80.3 to 98.0%. The multilocus sequence typing (MLST) results revealed 17 sequence types (STs), with ST10 being the most prevalent. The genome sequencing result showed that the Proteus vulgaris G32 genome consists of a 4.06-Mb chromosome, a 177,911-bp plasmid (pG32-177), and a 51,686-bp plasmid (pG32-51). A floR located in a drug-resistant region on the chromosome of P. vulgaris G32 was with IS91 family transposase, and the other floR gene on the plasmid pG32-177 was with an ISCR2 insertion sequence. The cfr gene was located on the pG32-51 flanked by IS26 element and TnpA26. This study suggested that the mobile genetic elements played an important role in the replication of resistance genes and the horizontal resistance gene transfer.202032903722
1642100.9996Characterization of resistance genes and plasmids from sick children caused by Salmonella enterica resistance to azithromycin in Shenzhen, China. INTRODUCTION: Samonella is 1 of 4 key global causes of diarrhoeal diseases, sometimes it can be serious, especially for yong children. Due to the extensive resistance of salmonella serotypes to conventional first-line drugs, macrolides (such as azithromycin) have been designated as the most important antibiotics for the treatment of salmonella. Antimicrobial resistance is a major public health problem in the world, and the mechanism of azithromycin resistance is rarely studied. METHODS: This study determined the azithromycin resistance and plasmids of Salmonella enterica isolates from children attending the Shenzhen Children's Hospital. The susceptibility of ampicillin (AMP), ciprofloxacin (CIP), ceftriaxone (CRO), sulfamethoxazole (SMZ), chloramphenicol (CL), and azithromycin (AZM) were detected and the genes and plasmids from azithromycin-resistant Salmonella were detected by Illumina hi-seq and Nanopore MinIone whole genome sequencing (WGS) using a map-based method, and the genomic background of these factors was evaluated using various bioinformatics tools. RESULTS: In total, 15 strains of nontyphoid Salmonella strains that were isolated (including S. typhimurium, S.London, S. Goldcoast, and S.Stanley) demonstrated resistance to azithromycin (minimum inhibitory concentration,MIC from 32 to >256 µg/mL), and the resistance rate was 3.08% (15/487). The sensitivity test to other antibiotics demonstrated 100% resistance to AMP, and the resistance to SMZ and CL was 86.7% and 80.0%, respectively. Through WGS analysis, all isolates were positive for a plasmid-encoded mphA gene. Plasmid incompatibility typing identified five IncFIB(K), five IncHI2/HI2A/Q1, two IncC, one IncHI2/HI2A/N, one IncR, one IncFII and one IncHI2/HI2A plasmids. Sequence analyses of plasmids revealed extensive homology to various plasmids or transposons in regions involved in plasmid replication/maintenance functions and/or in antibiotic resistance gene clusters. CONCLUSION: mphA is the main gene involved in azithromycin, a macrolide, and resistance to Salmonella. It is usually located on plasmids and easily spreads, hence posing a great threat to the current treatment of Salmonella infection. The plasmid sequence similarities suggest that the plasmids acquired resistance genes from a variety of enterica bacteria and underscore the importance of a further understanding of horizontal gene transfer among enterica bacteria.202337065212
2050110.9996Identification of a novel fosfomycin resistance gene (fosA2) in Enterobacter cloacae from the Salmon River, Canada. AIMS: To investigate the occurrence of fosfomycin-resistant (fos(R) ) bacteria in aquatic environments. METHODS AND RESULTS: A fos(R) strain of Enterobacter cloacae was isolated from a water sample collected at a site (50°41'33·44″N, 119°19'49·50″W) near the mouth of the Salmon River at Salmon Arm, in south-central British Columbia, Canada. The strain was identified by PCR screening for plasmid-borne, fosA-family amplicons, followed by selective plating. Sequencing of the resistance gene cloned using PCR primers to conserved flanking DNA revealed a new allele (95% amino acid identity to fosA), and I-Ceu I PFGE showed that it was chromosomally located. In Escherichia coli, the cloned DNA conferred a greater resistance to fosfomycin than its fosA counterpart. CONCLUSIONS: Gene fosA2 conferred fosfomycin resistance in an environmental isolate of Ent. cloacae. SIGNIFICANCE AND IMPACT OF THE STUDY: The repurposing of older antibiotics should be considered in the light of existing reservoirs of resistance genes in the environment.201121392044
5927120.9996The prevalence of, associations between and conjugal transfer of antibiotic resistance genes in Escherichia coli isolated from Norwegian meat and meat products. OBJECTIVES: To investigate the distribution of, associations between and the transferability of antimicrobial resistance genes in resistant Escherichia coli strains isolated from Norwegian meat and meat products. METHODS: The 241 strains investigated were collected within the frame of the Norwegian monitoring programme for antimicrobial resistance in bacteria from feed, food and animals (NORM-VET) during the years 2000-2003. PCR was carried out for detection of resistance genes. Conjugation experiments were carried out with the resistant isolates from meat as donor strains and E. coli DH5alpha as the recipient strain. Statistical analyses were performed with the SAS-PC-System version 9.1 for Windows. RESULTS: Resistance genes common in pathogenic E. coli were frequently found among the isolates investigated. Strains harbouring several genes encoding resistance to the same antimicrobial agent were significantly (P < 0.0001) more frequently multiresistant than others. Strong positive associations were found between the tet(A) determinant and the genetic elements sul1, dfrA1 and aadA1. Negative associations were found between resistance genes encoding resistance to the same antimicrobial agent: tet(A)/tet(B), sul1/sul2 and strA-strB/aadA1. The resistance genes were successfully transferred from 38% of the isolates. The transfer was more frequent from resistant isolates harbouring class 1 integrons (P < 0.001). CONCLUSIONS: Acquired resistance played a major role in conferring resistance among the isolates investigated. The possibility of transferring resistance increases both by increased multiresistance and by the presence of class 1 integrons. The conjugation experiments suggest that tet(A) and class 1 integrons are often located on the same conjugative plasmid.200616931539
5926130.9996Prevalence and Characterization of Gentamicin Resistance Genes in Escherichia coli Isolates from Beef Cattle Feces in Japan. Gentamicin is an important antibiotic for the treatment of opportunistic infections in the clinical field. Gentamicin-resistant bacteria have been detected in livestock animals and can be transmitted to humans through the food supply or direct contact. We have previously revealed that gentamicin-resistant Escherichia coli are distributed at a comparatively high rate from beef cattle in Japan, but few studies have focused on the molecular epidemiology of gentamicin-resistant bacteria. To understand these bacteria, this study examined the prevalence of various gentamicin resistance genes in gentamicin-resistant E. coli isolates from beef cattle feces. Of the 239 gentamicin-resistant E. coli isolates, the presence of the aacC2, aadB, or aac(3)-VIa genes was confirmed in 147, 84, and 8 isolates, respectively. All aac(3)-VIa-harboring isolates had an MIC value of 64 μg/mL for gentamicin and exhibited resistance to 11 antibiotic agents. An analysis of the representative aac(3)-VIa-harboring E. coli strain GC1-3-GR-4 revealed that the aac(3)-VIa gene was present on the IncA/C plasmid together with the aadA and bla(CMY) genes. Furthermore, the upstream region of the aac(3)-VIa gene contained the aadA gene and the class 1 integron-integrase gene (intI1). The aac(3)-VIa gene was detected for the first time in Japan and is expected to be able to transfer between bacteria via the IncA/C plasmid and integron. These results reveal the expansion of the distribution or diversity of gentamicin resistance genes in Japan.202235704076
2046140.9996QRDR mutations, efflux system & antimicrobial resistance genes in enterotoxigenic Escherichia coli isolated from an outbreak of diarrhoea in Ahmedabad, India. BACKGROUND & OBJECTIVES: Diverse mechanisms have been identified in enteric bacteria for their adaptation and survival against multiple classes of antimicrobial agents. Resistance of bacteria to the most effective fluoroquinolones have increasingly been reported in many countries. We have identified that most of the enterotoxigenic Escherichia coli (ETEC) were resistant to several antimicrobials in a diarrhoea outbreak at Ahmedabad during 2000. The present study was done to identify several genes responsible for antimicrobial resistance and mobile genetic elements in the ETEC strains. METHODS: Seventeen ETEC strains isolated from diarrhoeal patients were included in this study. The antimicrobial resistance was confirmed by conventional disc diffusion method. PCR and DNA sequencing were performed for the identification of mutation in the quinolone resistance-determining regions (QRDRs). Efflux pump was tested by inhibiting the proton-motive force. DNA hybridization assay was made for the detection of integrase genes and the resistance gene cassettes were identified by direct sequencing of the PCR amplicons. RESULTS: Majority of the ETEC had GyrA mutations at codons 83 and 87 and in ParC at codon 80. Six strains had an additional mutation in ParC at codon 108 and two had at position 84. Plasmid-borne qnr gene alleles that encode quinolone resistance were not detected but the newly described aac(6')-Ib-cr gene encoding a fluoroquinolne-modifying enzyme was detected in 64.7 per cent of the ETEC. Class 1 (intI1) and class 2 (intI2) integrons were detected in six (35.3%) and three (17.6%) strains, respectively. Four strains (23.5%) had both the classes of integrons. Sequence analysis revealed presence of dfrA17, aadA1, aadA5 in class 1, and dfrA1, sat1, aadA1 in class 2 integrons. In addition, the other resistance genes such as tet gene alleles (94.1%), catAI (70.6%), strA (58.8%), bla TEM-1 (35.2%), and aphA1-Ia (29.4%) were detected in most of the strains. INTERPRETATION & CONCLUSIONS: Innate gene mutations and acquisition of multidrug resistance genes through mobile genetic elements might have contributed to the emergence of multidrug resistance (MDR) in ETEC. This study reinforces the necessity of utilizing molecular techniques in the epidemiological studies to understand the nature of resistance responsible for antimicrobial resistance in different species of pathogenic bacteria.201121911975
5420150.9996A high incidence and coexistence of multiresistance genes cfr and optrA among linezolid-resistant enterococci isolated from a teaching hospital in Wenzhou, China. Linezolid is considered as a last-resort antimicrobial agent, the resistance of which is of great concern. The aim of this study was to investigate the mechanisms and transferability of linezolid resistance and molecular epidemiology of linezolid-resistant enterococcal isolates in Wenzhou, China. A collection of 1623 enterococcal strains, including 789 Enterococcus faecalis and 834 Enterococcus faecium, were isolated from our hospital during 2011-2016. Antimicrobial susceptibility testing and clinical data analysis were performed. Molecular mechanisms of linezolid resistance, including the existence of resistance genes cfr and optrA, as well as the mutations in 23S rRNA and ribosomal proteins L3, L4, and L22, were investigated by PCR and sequencing. Conjugation experiments were conducted, and epidemiological characteristics were analyzed by PFGE and MLST. In our study, 31 (3.93%) E. faecalis and 2 (0.24%) E. faecium exhibited resistance to linezolid. Risk factors correlated with linezolid-resistant enterococcal infections included gastrointestinal surgery hospitalization, urogenital disorders, tumor, diabetes, and polymicrobial infections. Among these isolates, 6 (18.18%) harbored cfr, 9 (27.27%) harbored optrA, and 18 (54.55%) co-harbored cfr and optrA. However, mutational mechanisms were not found in this study. Conjugation experiments demonstrated the transferability of cfr and optrA between Gram-positive and Gram-negative bacteria. The clone of these isolates was diverse and scattered. It is noteworthy that cfr and optrA were the main mechanisms of linezolid resistance in this study, posing a potential risk of spread of linezolid resistance. Strikingly, it reported firstly that the two transferable resistance genes cfr and optrA coexisted in the same E. faecalis isolates.201829909468
2953160.9996Diverse Mobile Genetic Elements and Conjugal Transferability of Sulfonamide Resistance Genes (sul1, sul2, and sul3) in Escherichia coli Isolates From Penaeus vannamei and Pork From Large Markets in Zhejiang, China. High prevalence rates of sulfonamide resistance genes sul1, sul2, and sul3 have been observed in Gram-negative bacteria isolated from humans, domestic animals, and aquaculture species worldwide. We investigated the distribution characteristics, location, conjugative transferability, and genetic environments of sul genes from Escherichia coli isolates collected from Penaeus vannamei and pork samples from three large markets in Zhejiang, China. The prevalence rates of sul genes in sulfonamide-resistant E. coli isolates from P. vannamei and pork samples were 90.0 and 88.6%, respectively, and the prevalence of sul1 and sul2 was significantly higher than that of sul3 (p < 0.05). Twenty-four representative sul-positive E. coli isolates were analyzed in detail. Southern blot hybridization confirmed that sul genes of E. coli isolates were located on plasmids and/or chromosomes. Transfer of resistance through conjugation was observed in all 18 E. coli isolates harboring sul genes on plasmids. Replicon typing identified seven different incompatibility groups and IncF was the dominant replicon type among sul gene-containing plasmids from both sources. PCR walking analysis indicated that 87.5% (35/40) of sul gene-related fragments carried insertion sequences (ISs) belonging to a variety of families in diverse sites, with IS26 occurring most frequently. In addition, the sul1 gene was detected mainly in fragments carrying class 1 integrons. Co-location on the same fragment with resistance genes that may contribute to the persistence and dissemination of sul1 and/or sul2 genes. The diversity of mobile genetic elements and resistance genes adjacent to sul3 was much lower than those adjacent to sul1 and sul2, especially those located in chromosomes, which reduced the transmission potential of the sul3 gene. In conclusion, combined with the results of clonal relatedness analysis by PFGE and MLST of 24 representative E. coli isolates from P. vannamei and pork samples, it showed that a small number of sul genes were vertically transmitted among E. coli from P. vannamei and that horizontal gene transfer was likely the main transmission mechanism of sul genes from both sources. Our results provide important information to better understand the risk of transmission of sul genes from seafood and meat to humans.201931428076
1978170.9996Antibiotic resistance plasmids in Enterobacteriaceae isolated from fresh produce in northern Germany. In this study, the genomes of 22 Enterobacteriaceae isolates from fresh produce and herbs obtained from retail markets in northern Germany were completely sequenced with MiSeq short-read and MinION long-read sequencing and assembled using a Unicycler hybrid assembly. The data showed that 17 of the strains harbored between one and five plasmids, whereas in five strains, only the circular chromosomal DNA was detected. In total, 38 plasmids were identified. The size of the plasmids detected varied between ca. 2,000 and 326,000 bp, and heavy metal resistance genes were found on seven (18.4%) of the plasmids. Eleven plasmids (28.9%) showed the presence of antibiotic resistance genes. Among large plasmids (>32,000 bp), IncF plasmids (specifically, IncFIB and IncFII) were the most abundant replicon types, while all small plasmids were Col-replicons. Six plasmids harbored unit and composite transposons carrying antibiotic resistance genes, with IS26 identified as the primary insertion sequence. Class 1 integrons carrying antibiotic resistance genes were also detected on chromosomes of two Citrobacter isolates and on four plasmids. Mob-suite analysis revealed that 36.8% of plasmids in this study were found to be conjugative, while 28.9% were identified as mobilizable. Overall, our study showed that Enterobacteriaceae from fresh produce possess antibiotic resistance genes on both chromosome and plasmid, some of which are considered to be transferable. This indicates the potential for Enterobacteriaceae from fresh produce that is usually eaten in the raw state to contribute to the transfer of resistance genes to bacteria of the human gastrointestinal system. IMPORTANCE: This study showed that Enterobacteriaceae from raw vegetables carried plasmids ranging in size from 2,715 to 326,286 bp, of which about less than one-third carried antibiotic resistance genes encoding resistance toward antibiotics such as tetracyclines, aminoglycosides, fosfomycins, sulfonamides, quinolones, and β-lactam antibiotics. Some strains encoded multiple resistances, and some encoded extended-spectrum β-lactamases. The study highlights the potential of produce, which may be eaten raw, as a potential vehicle for the transfer of antibiotic-resistant bacteria.202439287384
1520180.9996Colistin resistance in Salmonella and Escherichia coli isolates from a pig farm in Great Britain. OBJECTIVES: The objective of this study was to characterize colistin-resistant bacteria isolated from pigs on a farm in Great Britain following identification of a plasmid-borne colistin resistance mechanism in Escherichia coli from China. METHODS: Phenotypic antimicrobial susceptibility testing was undertaken by broth dilution and WGS was performed to detect the presence of genes encoding resistance and virulence. Transferable colistin resistance was investigated by conjugation. RESULTS: Two E. coli and one Salmonella Typhimurium variant Copenhagen were shown to be MDR, including resistance to colistin, with one E. coli and the Salmonella carrying the mcr-1 gene; all three harboured chromosomal mutations in genes conferring colistin resistance and both E. coli harboured β-lactamase resistance. The Salmonella mcr-1 plasmid was highly similar to pHNSHP45, from China, while the E. coli mcr-1 plasmid only had the ISApII and mcr-1 genes in common. The frequency of mcr-1 plasmid transfer by conjugation to recipient Enterobacteriaceae from Salmonella was low, lying between 10(-7) and 10(-9) cfu/recipient cfu. We were unable to demonstrate mcr-1 plasmid transfer from the E. coli. Plasmid profiling indicated transfer of multiple plasmids from the Salmonella resulting in some MDR transconjugants. CONCLUSIONS: Identification of the mcr-1 gene in Enterobacteriaceae from pigs confirms its presence in livestock in Great Britain. The results suggest dissemination of resistance through different horizontally transferable elements. The in vitro transfer of multiple plasmids carrying colistin and other resistances from the Salmonella isolate underlines the potential for wider dissemination and recombination.201627147305
2926190.9996Molecular characterization of antibiotic resistance in Pseudomonas and Aeromonas isolates from catfish of the Mekong Delta, Vietnam. A collection of 116 motile Pseudomonas spp. and 92 Aeromonas spp. isolated from 15 Vietnamese intensive catfish farms was analyzed to examine the molecular antibiotic resistance characteristics and the transferability of resistance markers within and between species. High levels of resistance to ampicillin, trimethoprim/sulfamethoxazole, nalidixic acid, chloramphenicol, and nitrofurantoin were observed. The percentage of multiple drug resistance of Pseudomonas spp. and Aeromonas spp. isolates was 96.6% and 61.9%, respectively. The multiple antibiotic resistance (MAR) index mean values of 0.457 and 0.293 of Pseudomonas and Aeromonas isolates, respectively, indicated that these isolates were exposed to high risk sources of contamination where antibiotics were commonly used. Approximately 33% of Pseudomonas spp. and 28% of Aeromonas spp. isolates from catfish contained class 1 integrons, but no class 2 integrons were detected. Several common resistance genes including aadA, dfrA and catB were harbored in class 1 integrons. Large plasmids (>55 kb) were frequently detected in 50% and 71.4% of the plasmids extracted from Pseudomonas and Aeromonas isolates, respectively. Conjugation and transformation experiments demonstrated the successful transfer of all or part of the resistance phenotypes of catfish isolates to the recipient strains, including laboratory strains and strains isolated from this study. These results highlight the likely role of catfish bacteria as a reservoir of antibiotic resistant, Gram-negative bacteria harboring a pool of mobile genetic elements that can readily be transferred intra- and interspecies. To our knowledge, this is the first report on molecular characterization of antibiotic resistance of bacteria isolated from catfish in Vietnam.201424629778