Tetracycline Resistance Gene Tet Research Articles

Antimicrobial Susceptibility and Occurrence of Resistance genes among Salmonella arizonae isolated from Chicken Meat samples in Sokoto Metropolis, Sokoto State, Nigeria

This study was conducted to determine the antimicrobial susceptibility and occurrence of resistance genes among Salmonella Arizonae isolated from chicken meat samples collected in Sokoto metropolis, Sokoto State Nigeria. A total of 400 Chicken’s Meat samples (breast muscle) were collected and examined for the presence of Salmonella organisms. The isolated Salmonella Arizonae were then tested for antimicrobial susceptibility using disc diffusion technique and antimicrobial resistant isolates were then examined for the presence of ampicillin resistance gene blaTEM, chloramphenicol resistance gene floR and tetracycline resistance gene tetA by PCR. Salmonella aizonae were isolated in only 4.5% (18 / 400) of the samples examined. Antimicrobial susceptibility test of the isolates showed susceptibility to nitrofurantoin (94.4%), nalidixic acd (94.4%), oflxacin (77.8%), augmentin (72.2%) and cotrimoxazole (66.7%). However, the isolates were resistant to tetracycline (88.9%), ampicillin (72.2%) and chloramphenicol (66.6%). Only 8 of these isolates were resistant to one or more of the antimicrobial agents tested. Resistance gene analysis of the resistant isolates shows the presence of ampicillin resistance gene, blaTEM in 75% (6 / 8) of the tested isolates. Presence of chloramphenicol resistance gene, floR was also detected in 37.5% (3 / 8) of the isolates. Presence of multiple resistance genes was also detected in the isolates. A combination of two different resistance genes was detected in 62.5% (5 / 8) of the isolates and presence of all the three resistance genes (blaTEM, tetA and floR) was detected in one of the isolates. Antibiotics have been used widely in poultry to treat, prevent infections and also in feeds to promote growth. Such practice has improved poultry performance effectively and economically but has resulted in the increase in the spread of resistant bacterial strains. In our study, a high resistance profile of 88.9% to tetracycline, a popularly use drug in poultry industry and the presence of multiple resistance genes in 62.5% of the isolates was also observed. There is therefore the need for more rational use of antibiotics in animal production and more prudent use in humans.

Injectable antimicrobials in commercial feedlot cattle and their effect on the nasopharyngeal microbiota and antimicrobial resistance

Beef cattle in North America that are deemed to be at high risk of developing bovine respiratory disease (BRD) are frequently administered a metaphylactic antibiotic injection to control the disease. Cattle may also receive in-feed antimicrobials to prevent specific diseases and ionophores to improve growth and feed efficiency. Presently, attempts to evaluate the effects that these medications have on antibiotic resistance in the bovine nasopharyngeal microbiota have been focused on culturable bacteria that are associated with BRD. Therefore, we assessed the effects of injectable antibiotics on the nasopharyngeal microbiota of commercial feedlot cattle in Alberta, Canada, through the first 60 d on feed. Although all cattle in the study were also receiving in-feed chlortetracycline and monensin, the administration of a single injection of either oxytetracycline or tulathromycin at feedlot placement altered the nasopharyngeal microbiota in comparison with the cattle receiving only in-feed antibiotics. Oxytetracycline significantly (P < 0.05) reduced the relative abundance of Mannheimia spp. from feedlot entry to exit (≥60 d) and both oxytetracycline and tulathromycin treated cattle had a significantly lower relative abundance of Mycoplasma spp. at feedlot exit compared with the in-feed antibiotic only group. The proportion of the tetracycline resistance gene tet(H) was significantly increased following oxytetracycline injection (P < 0.05). Oxytetracycline also reduced both the number of OTUs and the Shannon diversity index in the nasopharyngeal microbiota (P < 0.05). These results demonstrate that in feedlot cattle receiving subtherapeutic in-feed antimicrobials, the administration of a single injection of either oxytetracycline or tulathromycin resulted in measurable changes to the nasopharyngeal microbiota during the first 60 d following feedlot placement.

Probing Genomic Aspects of the Multi-Host Pathogen Clostridium perfringens Reveals Significant Pangenome Diversity, and a Diverse Array of Virulence Factors.

Clostridium perfringens is an important cause of animal and human infections, however information about the genetic makeup of this pathogenic bacterium is currently limited. In this study, we sought to understand and characterise the genomic variation, pangenomic diversity, and key virulence traits of 56 C. perfringens strains which included 51 public, and 5 newly sequenced and annotated genomes using Whole Genome Sequencing. Our investigation revealed that C. perfringens has an “open” pangenome comprising 11667 genes and 12.6% of core genes, identified as the most divergent single-species Gram-positive bacterial pangenome currently reported. Our computational analyses also defined C. perfringens phylogeny (16S rRNA gene) in relation to some 25 Clostridium species, with C. baratii and C. sardiniense determined to be the closest relatives. Profiling virulence-associated factors confirmed presence of well-characterised C. perfringens-associated exotoxins genes including α-toxin (plc), enterotoxin (cpe), and Perfringolysin O (pfo or pfoA), although interestingly there did not appear to be a close correlation with encoded toxin type and disease phenotype. Furthermore, genomic analysis indicated significant horizontal gene transfer events as defined by presence of prophage genomes, and notably absence of CRISPR defence systems in >70% (40/56) of the strains. In relation to antimicrobial resistance mechanisms, tetracycline resistance genes (tet) and anti-defensins genes (mprF) were consistently detected in silico (tet: 75%; mprF: 100%). However, pre-antibiotic era strain genomes did not encode for tet, thus implying antimicrobial selective pressures in C. perfringens evolutionary history over the past 80 years. This study provides new genomic understanding of this genetically divergent multi-host bacterium, and further expands our knowledge on this medically and veterinary important pathogen.

Wide but Variable Distribution of a Hypervirulent Campylobacter jejuni Clone in Beef and Dairy Cattle in the United States

ABSTRACTCampylobacter jejuni clone SA is the major cause of sheep abortion and contributes significantly to foodborne illnesses in the United States. Clone SA is hypervirulent because of its distinct ability to produce systemic infection and its predominant role in clinical sheep abortion. Despite the importance of clone SA, little is known about its distribution and epidemiological features in cattle. Here we describe a prospective study on C. jejuni clone SA prevalence in 35 feedlots in 5 different states in the United States and a retrospective analysis of clone SA in C. jejuni isolates collected by National Animal Health Monitoring System (NAHMS) dairy studies in 2002, 2007, and 2014. In feedlot cattle feces, the overall prevalence of Campylobacter organisms was 72.2%, 82.1% of which were C. jejuni. Clone SA accounted for 5.8% of the total C. jejuni isolates, but its prevalence varied by feedlot and state. Interestingly, starlings on the feedlots harbored C. jejuni in feces, including clone SA, suggesting that these birds may play a role in the transmission of Campylobacter. In dairy cattle, the overall prevalence of clone SA was 7.2%, but a significant decrease in the prevalence was observed from 2002 to 2014. Whole-genome sequence analysis of the dairy clone SA isolates revealed that it was genetically stable over the years and most of the isolates carried the tetracycline resistance gene tet(O) in the chromosome. These findings indicate that clone SA is widely distributed in both beef and dairy cattle and provide new insights into the molecular epidemiology of clone SA in ruminants.IMPORTANCE C. jejuni clone SA is a major cause of small-ruminant abortion and an emerging threat to food safety because of its association with foodborne outbreaks. Cattle appear to serve as a major reservoir for this pathogenic organism, but there is a major gap in our knowledge about the epidemiology of clone SA in beef and dairy cattle. By taking advantage of surveillance studies conducted on a national scale, we found a wide but variable distribution of clone SA in feedlot cattle and dairy cows in the United States. Additionally, the work revealed important genomic features of clone SA isolates from cattle. These findings provide critically needed information for the development of preharvest interventions to control the transmission of this zoonotic pathogen. Control of C. jejuni clone SA will benefit both animal health and public health, as it is a zoonotic pathogen causing disease in both ruminants and humans.

Presence of Chlamydia trachomatis and Mycoplasma spp., but not Neisseria gonorrhoeae and Treponema pallidum, in women undergoing an infertility evaluation: high prevalence of tetracycline resistance gene tet(M)

Chlamydia trachomatis, Mycoplasma spp., Neisseria gonorrhoeae and Treponema pallidum are sexually transmitted pathogens that threaten reproductive health worldwide. In this study, vaginal swabs obtained from women (n = 133) that attended an infertility clinic in China were tested with qPCRs for C. trachomatis, Mycoplasma spp., N. gonorrhoeae, T. pallidum and tetracycline resistance genes. While none of vaginal swabs were positive for N. gonorrhoeae and T. pallidum, 18.8% (25/133) of the swabs were positive for Chlamydia spp. and 17.3% of the swabs (23/133) were positive for Mycoplasma species. All swabs tested were positive for tetracycline resistance gene tet(M) which is the most effective antibiotic for bacterial sexually transmitted infections. The qPCRs determined that the gene copy number per swab for tet(M) was 7.6 times as high as that of C. trachomatis 23S rRNA, and 14.7 times of Mycoplasma spp. 16S rRNA. In China, most hospitals do not detect C. trachomatis and Mycoplasma spp. in women with sexually transmitted infections and fertility problems. This study strongly suggests that C. trachomatis and Mycoplasma spp. should be routinely tested in women with sexually transmitted infections and infertility in China, and that antimicrobial resistance of these organisms should be monitored. Further studies are warranted to determine the prevalences in different regions and associated risk factors.

Antibiotic Resistance in Salmonella from Retail Foods of Animal Origin and Its Association with Disinfectant and Heavy Metal Resistance.

This study aims to demonstrate the antibiotic resistance and its association with disinfectant and heavy metal resistance in 152 Salmonella isolates recovered from retail foods of animal origins. Susceptibility testing demonstrated that 92.8% isolates were resistant to at least one antibiotic, and the resistance was highest to oxytetracycline (80.9%), followed by trimethoprim (64.5%), amoxicillin (28.9%), ampicillin (28.3%), levofloxacin (21.7%), ciprofloxacin (16.4%), and gentamicin (10.5%), respectively. The blaTEM and tetA genes (44.7%) were commonly present. The qacF and qacEΔ1 genes were detected in 18.4% and 8.6% of all isolates. The Cu-resistance genes pcoR, pcoC, and pcoA were the most prevalent (20.4-40.8%), followed by Hg-resistance gene merA (17.8%) and As-resistance genes arsB (6.6%). The antibiotic resistance was highly associated with disinfectant or certain heavy metal resistance genes. Most notably, the association among Cu-resistance genes (pcoC, pcoR), disinfectant resistance genes (qacF, qacEΔ1), and tetracycline and sulfonamide resistance genes (tet, sul) was significant (p < 0.05). Pulsed-field gel electrophoresis revealed that Salmonella isolates was associated with supermarkets indicating the possibility of crosscontamination in farms or processing environment. This study indicated that retail meats may be a reservoir for the dissemination of antibiotic-resistant Salmonella and using disinfectants for decontamination or metals in livestock may provide a pressure for coselecting strains with acquired resistance to other antimicrobials.

Use of a filtering process to remove solid waste and antibiotic resistance genes from effluent of a flow-through fish farm

The objective of this study was to investigate reduction in antibiotic resistance genes (ARGs) via targeting solid waste in effluent from a flow-through aquaculture in South Korea. The level of suspended solids in the filtrates was approximately 12.5±2.3mg/L, corresponding to a removal efficiency of 68.8±5.7% irrespective of variations in the size of the filter pores. The total number of particles in the effluent was reduced to the lowest numbers of particles using a filter pore size of 25μm, corresponding to a removal efficiency of 40.3%. Among the 23 ARGs conferring resistance to tetracyclines, beta-lactam antibiotics, sulfonamides, quinolones, macrolides, florfenicol and multidrug, tetracycline resistance genes were the most prevalent with a relative abundance of 67.5%. Of eleven tetracycline resistance genes (tetA, tetB, tetD, tetE, tetG, tetH, tetM, tetQ, tetX, tetZ, tetB/P) analyzed, the relative abundance of tetG was the highest in the effluent. The removal efficiency of the total number of particles showed similar patterns to the removal efficiency of ARGs depending on the size of the filter pores. Levels of ARGs in the filtrates were reduced to approximately 60.5% of those of the ARGs in the effluents. With a filter pore size of 25μm, a maximum removal efficiency of 66.0% was achieved. In particular, the relative abundance of detected tetracycline resistance genes decreased only after passing through the filters, perhaps reflecting the presence of high quantities of tetracycline resistance genes in particles from the fish farm. Using Illumina sequencing based on a 16S rRNA gene, the dominant phyla were found to be Bacteroidetes, Proteobacteria, Planctomycetes and Verrucomicrobia in the effluent. Although the overall composition of the bacterial communities was not significantly changed via filtering tests, only the relative abundance of Bacteroidetes and Proteobacteria was changed. These results demonstrate that a filtering process in aquaculture facilities can be used to reduce solid waste as well as ARGs from aquaculture farms.

The impacts of a lower protein and energy density diet in aged male Sprague Dawley rat studies

The collaboration project VASIB aims at reducing the antibiotic consumption in pig production by integrating information from consulting expertise in clinical inspection, hygiene, epidemiology, microbiology and pharmacology. In this VASIB subproject, we investigated the antimicrobial susceptibility and relatedness of porcine respiratory tract pathogens. Bordetella bronchiseptica (n = 47), Pasteurella multocida (n = 18) and Streptococcus suis (n = 58) were obtained from weaner pigs at two farms. Antimicrobial susceptibility testing was performed by broth microdilution according to CLSI standards. Resistance genes were detected via specific PCR assays. Macrorestriction analysis was conducted to determine the relatedness of the isolates and to identify clones. The B. bronchiseptica isolates showed indistinguishable (farm 1) or two closely related XbaI-patterns (farm 2). Different SmaI-PFGE patterns of P. multocida isolates were obtained at three different time points. In contrast, PFGE analysis of S. suis indicated more than one fragment pattern per pig and time point. Isolates exhibiting indistinguishable PFGE patterns were considered to represent the same clone. This study showed that only two closely related B. bronchiseptica clones were present in both farms, which had low MICs to all antimicrobials, except to β-lactams. Different P. multocida clones were present at the three time points. They showed overall low MIC values, with two clones being resistant and one intermediate to tetracycline. S. suis clones were resistant to tetracycline (n = 19) and/or erythromycin/clindamycin (n = 16). They harboured the tetracycline resistance genes tet(O), tet(M) or tet(L) and/or the macrolide/lincosamide/streptogramin B resistance gene erm(B). Five penicillin-resistant S. suis clones were also detected.

Monitoring the prevalence of the tetracycline efflux genes among E. coli isolated from chicken colibacillosis

BACKGROUND: Avian Colibacillosis can lead to important economic losses in the poultry industry. Escherichia coli the causative agent of this disease has acquired resistance to different antibiotics, including tetracycline. OBJECTIVES: This study was carried out to detect the distribution of tetracycline Group І efflux genes genes among E.coli isolates from from avian colibacillosis in Iran by PCR assay .METHODS: A total of 50 E. coli isolates from chicken colibacillosis were characterized by cultural, biochemical and PCR methods. Kirby-Bauer disk diffusion method was used to define the resistance of isolates to tetracycline, then the Frequencies of tetracycline resistance genes (tetA, tetB, tetC, tetG, tetH, tetZ and tetE) were also determined using PCR method. RESULTS: According to biochemical and molecular experiments, 50 isolates from 237 chicken samples were recognized as E. coli. Seventy six(76%) of the isolates, however, were resistant to tetracycline. The distribution of tetracycline-resistance genes among E. coli isolates included tetB(34%) , tetA(26%), tetE(16%), tetC(15%), tetH(12%), tetG(12%) and tetZ(6%). CONCLUSION: The present study highlights the prevalence of tetracycline resistant E. coli among chickens which is due to extensive

Antimicrobial resistance and resistance genes in Salmonella strains isolated from broiler chickens along the slaughtering process in China

A total of 189 Salmonella isolates were recovered from 627 samples which were collected from cecal contents of broilers, chicken carcasses, chicken meat after cutting step and frozen broiler chicken products along the slaughtering process at a slaughterhouse in Sichuan province of China. The Salmonella isolates were subjected to antimicrobial susceptibility testing to 10 categories of antimicrobial agents using the Kirby–Bauer disk diffusion method. Those antibiotics-resistant isolates were further investigated for the occurrence of resistance genes, the presence of class 1 integron as well as the associated gene cassettes, and the mutations within the gyrA and parC genes. Consequently, the prevalence of Salmonella was 30.14% (47.96% for cecal content, 18.78% for chicken carcasses, 31.33% for cutting meat and 14.00% for frozen meat, respectively). The predominant serotypes were S. Typhimurium (15.34%) and S. Enteritidis (69.84%). High resistance rates to the following drugs were observed: nalidixic acid (99.5%), ampicillin (87.8%), tetracycline (51.9%), ciprofloxacin (48.7%), trimethoprim/sulfamethoxazole (48.1%), and spectinomycin (34.4%). Antimicrobial resistance profiling showed that 60.8% of isolates were multidrug resistant (MDR), and MDR strains increased from 44.7% to 78.6% along the slaughtering line. 94.6% (n=157) of beta-lactam-resistant isolates harbored at least one resistance gene of blaTEM or blaCTX-M. The relatively low prevalence of aminoglycoside resistance genes (aac(3)-II, aac(3)-IV, and ant(2″)-I) was found in 49 (66.2%) of antibiotic-resistant isolates. The tetracycline resistance genes (tet(A), tet(B), tet(C), and tet(G) and sulfonamide resistance genes (sul1, sul2, and sul3) were identified in 84 (85.7%) and 89 (97.8%) antibiotic-resistant isolates respectively. floR was identified in 44 (97.8%) florfenicol-resistant isolates. Class 1 integron was detected in 37.4% (n=43) of the MDR isolates. Two different gene cassettes, blaOXA-30-aadA1 (19 isolates) and blaOXA-30-aadA1/drfA1-orfC (2 isolates), were identified in class 1 integron-positive isolates. 97.9% (184/188) of quinolone-resistant isolates had at least one mutation within gyrA or parC. Overall, antimicrobial resistance showed an increasing trend along the slaughtering process. The results showed that broiler chicken products in the slaughterhouse were contaminated with MDR Salmonella, which might originate from food producing animals to some extent, and cross-contamination during slaughter, and facilitate the dissemination of the resistance genes to consumers along the production chain, which suggests importance of controlling Salmonella during slaughter for public health, underlying strict hygiene method and HACCP management to reduce cross-contamination.

Degradation of Extracellular Antibiotic Resistance Genes with UV254 Treatment.

Disinfected wastewater effluent contains a complex mixture of biomolecules including DNA. If intact genes conveying antibiotic resistance survive the disinfection process, environmental bacteria may take them up. We treated plasmid pWH1266, which contains ampicillin resistance gene blaTEM-1 and tetracycline resistance gene tetA, with UV254 doses up to 430 mJ/cm2 and studied the ability of those genes to be acquired by Acinetobacter baylyi. The plasmids required approximately 20-25 mJ/cm2 per log10 loss of transformation efficiency. We monitored plasmid DNA degradation using gel electrophoresis and qPCR with both short amplicons (∼200 bps, representative of ARG amplicon lengths commonly used for environmental monitoring) and long amplicons (800-1200 bps, designed to cover the entire resistance genes). The rate of transformability loss due to UV254 treatment was approximately 20× and 2× larger than the rate of gene degradation measured with the short and long amplicons qPCR, respectively. When extrapolated to account for the length of the entire pWH1266 plasmid, the qPCR rate constants were 2-7× larger than the rate constants measured with transformation assays. Gel electrophoresis results confirmed that DNA cleavage was not a major inactivating mechanism. Overall, our results demonstrate that qPCR conservatively measures the potential for a gene to be transformed by environmental bacteria following UV254 treatment.

Serotype identification and antibiotic susceptibility of Shiga toxin-producing Escherichia coli in the Weishan area in Shandong Province, China

Objective: To determine the serotypes and drug resistance profiles of Shiga toxin-producing Escherichia coli (STEC) in animal stools from the Weishan area in Shandong Province, China. To provide the basis for further study. Methods: Five hundred animal stool samples (from pigs, cattle, sheep, dogs and birds) were collected from the Weishan area and STEC strains were isolated from these samples. Strains were serotyped by a serum agglutination test, and their drug resistance profiles were determined through antimicrobial sensitivity experiments. In this study, PCR was used to detect tetracycline resistance genes (tetA, tetB, tetC, tetD) and beta-lactam resistance genes (blaSHV-1, blaCTX-M, blaTEM). Results: Sixteen strains of STEC were isolated from animal stool samples. Thirteen strains were isolated from pig stool samples, two from bovine stool samples and one from a sheep stool sample. Two of the strains were identified as E. coli O157:H7, and other 14 strains were non-O157 STEC of different serotypes. Antimicrobial sensitivity experiments showed that 15 of the strains were multidrug resistant. The rates of resistance were as follows: nalidixic acid (12/16 strains), sulfisoxazole (11/16), trimethoprim and sulphame-thoxazole (11/16), doxycycline (9/16), azithromycin (9/16), tetracycline (9/16), chloramphenicol (8/16) and streptomycin (8/16). Therefore, nalidixic acid showed the highest rate of resistance among the strains, followed by trimethoprim and sulphame-thoxazole, and sulfisoxazole. Resistance to cefepime or imipenem was not detected. In total, three types of drug resistance genes (tetA, tetB and tetC) were detected among the 16 strains. Conclusion: The results showed that STEC strains isolated from animals in the Weishan area were of a range of serotypes. The 16 strains of STEC isolated from animal stools in this area were resistant to a number of antibiotics, with many strains displaying multidrug resistance.

The role of zero valent iron on the fate of tetracycline resistance genes and class 1 integrons during thermophilic anaerobic co-digestion of waste sludge and kitchen waste

Activated sludge has been identified as a potential significant source of antibiotic resistance genes (ARGs) to the environment. Anaerobic digestion is extensively used for sludge stabilization and resource recovery, and represents a crucial process for controlling the dissemination of ARGs prior to land application of digested sludge. The objective of this study is to investigate the effect of zero valent iron (Fe0) on the attenuation of seven representative tetracycline resistance genes (tet, tet(A), tet(C), tet(G), tet(M), tet(O), tet(W), and tet(X)), and the integrase gene intI1 during thermophilic anaerobic co-digestion of waste sludge and kitchen waste. Significant decrease (P < 0.05) in the quantities of tet (except tet(W)) and intI1 genes was observed at Fe0 dosage of 5 g/L, whereas no significant differences (P > 0.05) were found for all gene targets between digesters with Fe0 dosages of 5 and 60 g/L. A first-order kinetic model favorably described the trends in concentrations of tet and intI1 gene targets during thermophilic anaerobic digestion with or without Fe0. Notably, tet genes encoding different resistance mechanisms behaved distinctly in anaerobic digesters, although addition of Fe0 could enhance their reduction. The overall results of this research suggest that thermophilic anaerobic digestion with Fe0 can be a potential alternative technology for the attenuation of tet and intI1 genes in waste sludge.

Distribution of tetracycline resistance genes and AmpC β-lactamase genes in representative non-urban sewage plants and correlations with treatment processes and heavy metals

The mixed development of livestock breeding and industry in non-urban zones is a very general phenomenon in China. Distribution of antibiotic resistance genes (ARGs) in non-urban sewage treatment systems has not been paid enough attentions. In this study, eleven tetracycline resistance genes (tetA, tetB, tetC, tetE, tetG, tetL, tetM, tetO, tetQ, tetS and tetX), four AmpC β-lactamase genes (EBC, MOX, FOX and CIT) and four heavy metals (Cu, Zn, Cd and Pb) were detected and analyzed in four non-urban sewage plants with different sewage sources and different treatment processes in Guangzhou. The results showed that tetA and tetC were the most prevalent tetracycline resistance genes with the same detection frequency of 85% and EBC was the most prevalent AmpC β-lactamase gene with a detection frequency of 75%. The relative abundance of tetracycline resistance genes was approximately 1.6 orders of magnitudes higher than that of AmpC β-lactamase genes in all samples. A/O was the most effective process for the non-urban sewage plant receiving industrial or agricultural wastewater. Sedimentation was the most key process to eliminate ARGs from liquid phase. Most ARGs were carried in excess sludge rather than effluent. Significant correlation was found between the tet gene and Zn (r = 0.881, p < 0.01), followed by the AmpC gene and Cu (r = 0.847, p < 0.01), the tet gene and Cu (r = 0.714, p < 0.05). Therefore, the pollution of ARGs in the sewage treatment systems of non-urban zones co-polluted by heavy metals should be paid more attentions.

A new mosaic integrative and conjugative element fromStreptococcus agalactiaecarrying resistance genes for chloramphenicol (catQ) and macrolides [mef(I) anderm(TR)

To investigate the genetic basis of catQ-mediated chloramphenicol resistance in Streptococcus agalactiae. Two clinical strains of catQ-positive chloramphenicol-resistant S. agalactiae (Sag236 and Sag403) were recently isolated, typed (MLST, PFGE pulsotypes, capsular types) and their antibiotic resistances investigated by phenotypic and genotypic approaches. Several molecular methods (PCR mapping, restriction assays, Southern blotting, sequencing and sequence analysis, conjugal transfer assays) were used to determine the genetic context of catQ and characterize a genetic element detected in the isolates. Sag236 and Sag403 shared the same ST (ST19), but exhibited a different capsular type (III and V, respectively) and pulsotype. Both harboured the macrolide resistance genes mef(I) and erm(TR) and the tetracycline resistance gene tet(M). Accordingly, they were resistant to chloramphenicol, erythromycin and tetracycline. catQ and mef(I) were associated in an IQ module that was indistinguishable in Sag236 and Sag403. In mating assays, chloramphenicol and erythromycin resistance proved transferable, at low frequency, only from Sag236. Transconjugants carried not only catQ and mef(I), but also erm(TR), suggesting a linkage of the three resistance genes in a mobile element, which, though seemingly non-mobile, was also detected in Sag403. The new element (designated ICESag236, ∼110 kb) results from recombination of two integrative and conjugative elements (ICEs) originally described in different streptococcal species: S. agalactiae ICESagTR7, carrying erm(TR); and Streptococcus pneumoniae ICESpn529IQ, carrying the prototype IQ module. These findings strengthen the notion that widespread streptococcal ICEs may form mosaics that enhance their diversity and spread, broaden their host range and carry new cargo genes.

Daphnia as a refuge for an antibiotic resistance gene in an experimental freshwater community

Mechanisms that enable the maintenance of antibiotic resistance genes in the environment are still greatly unknown. Here we show that the tetracycline resistance gene tet(A) is largely removed from the pelagic aquatic bacterial community through filter feeding by Daphnia obtusa while it becomes detectable within the microbiome of the daphniids themselves, where it was not present prior to the experiment. We moreover show that a multitude of Daphnia-associated bacterial taxa are potential carriers of tet(A) and postulated that the biofilm-like structures, where bacteria grow in, may enable horizontal transfer of such genes. This experiment highlights the need to take ecological interactions and a broad range of niches into consideration when studying and discussing the fate of antibiotic resistance genes in nature.

Antibiotics and Antibiotic Resistance Genes in Sediment of Honghu Lake and East Dongting Lake, China.

Sediment is an ideal medium for the aggregation and dissemination of antibiotics and antibiotic resistance genes (ARGs). The levels of antibiotics and ARGs in Honghu Lake and East Dongting Lake of central China were investigated in this study. The concentrations of eight antibiotics (four sulfonamides and four tetracyclines) in Honghu Lake were in the range 90.00-437.43μgkg-1 (dry weight (dw)) with mean value of 278.21μgkg-1 dw, which was significantly higher than those in East Dongting Lake (60.02-321.04μgkg-1 dw, mean value of 195.70μgkg-1 dw). Among the tested three sulfonamide resistance genes (sul) and eight tetracycline resistance genes (tet), sul1, sul2, tetA, tetC, and tetM had 100% detection frequency in sediment samples of East Dongting Lake, while only sul1, sul2, and tetC were observed in all samples of Honghu Lake. The relative abundance of sul2 was higher than that of sul1 at p < 0.05 level in both lakes. The relative abundance of tet genes in East Dongting Lake was in the following order: tetM > tetB > tetC > tetA. The relative abundance of sul1, sul2, and tetC in East Dongting Lake was significantly higher than those in Honghu Lake. The abundance of background bacteria may play an important role in the horizontal spread of sul2 and tetC genes in Honghu Lake and sul1 in East Dongting Lake, respectively. Redundancy analysis indicated that tetracyclines may play a more important role than sulfonamides in the abundance of sul1, sul2, and tetC gens in Honghu Lake and East Dongting Lake.

Complete sequence of a plasmid from a bovine methicillin-resistant Staphylococcus aureus harbouring a novel ica-like gene cluster in addition to antimicrobial and heavy metal resistance genes

The multiresistance plasmid pAFS11, obtained from a bovine methicillin-resistant Staphylococcus aureus (MRSA) isolate, was completely sequenced and analysed for its structure and organisation. Moreover, the susceptibility to the heavy metals cadmium and copper was determined by broth macrodilution. The 49,189-bp plasmid harboured the apramycin resistance gene apmA, two copies of the macrolide/lincosamide/streptogramin B resistance gene erm(B) (both located on remnants of a truncated transposon Tn917), the kanamycin/neomycin resistance gene aadD, the tetracycline resistance gene tet(L) and the trimethoprim resistance gene dfrK. The latter three genes were part of a 7,284-bp segment which was bracketed by two copies of IS431. In addition, the cadmium resistance operon cadDX as well as the copper resistance genes copA and mco were located on the plasmid and mediated a reduced susceptibility to cadmium and copper. Moreover, a complete novel ica-like gene cluster of so far unknown genetic origin was detected on this plasmid. The ica-like gene cluster comprised four different genes whose products showed 64.4–76.9% homology to the Ica proteins known to be involved in biofilm formation of the S. aureus strains Mu50, Mu3 and N315. However, 96.2–99.4% homology was seen to proteins from S. sciuri NS1 indicating an S. sciuri origin. The finding of five different antibiotic resistance genes co-located on a plasmid with heavy metal resistance genes and an ica-like gene cluster is alarming. With the acquisition of this plasmid, antimicrobial multiresistance, heavy metal resistances and potential virulence properties may be co-selected and spread via a single horizontal gene transfer event.

Copresence of tet(K) and tet(M) in Livestock-Associated Methicillin-Resistant Staphylococcus aureus Clonal Complex 398 Is Associated with Increased Fitness during Exposure to Sublethal Concentrations of Tetracycline.

The tetracycline resistance gene tet(K) was shown to be integrated within the predominant staphylococcal cassette chromosome mec (SCCmec) element of Danish livestock-associated methicillin-resistant Staphylococcus aureus CC398 (LA-MRSA CC398). These LA-MRSA CC398 isolates already possessed tet(M), but the acquisition of tet(K) significantly improved their fitness at sublethal concentrations of tetracycline. Because tet(K) is genetically linked to SCCmec, the use of tetracycline in food animals may have contributed to the successful spread of LA-MRSA CC398.

Isolation and Identification of Aerobic Bacteria Carrying Tetracycline and Sulfonamide Resistance Genes Obtained from a Meat Processing Plant.

Microbial contamination in food-processing plants can play a fundamental role in food quality and safety. The purpose of this study was to investigate aerobic bacteria carrying tetracycline and sulfonamide resistance genes from a meat processing plant as possible sources of meat contamination. One hundred swab samples from surfaces of conveyor belts, meatslicers, meat knives, benches, plastictrays, gloves, and aprons were analyzed. A total of 168 isolates belonging to 10 genera were obtained, including Pseudomonas sp. (n = 35), Acinetobacter sp. (n = 30), Aeromonas sp. (n = 20),Myroides sp. (n = 15), Serratia sp. (n = 15), Staphylococcus sp. (n = 14), Enterobacter sp. (n = 11), Escherichia coli (n = 10), Lactococcus sp. (n = 10), and Klebsiella sp. (n = 8). Of the 168 isolates investigated, 60.7% showed resistance to tetracycline and 57.7% to trimethoprim/sulfamethoxazole. The tetracycline resistance genes tetL, tetA, tetB, tetC, tetE, tetM, tetS, tetK, and tetX were found in the frequency of 7.7%, 6.0%, 4.8%, 4.8%, 3.6%, 3.6%, 3.6%, 1.2%, and 0.6%, respectively. Sulfonamide resistance genes sul1 and sul2 were observed in the frequency of 17.9% and 38.1%, respectively. The tetracycline resistance genes tetX was first found in Myroides sp. This investigation demonstrated that food contact surfaces in a meat processing plant may be sources of contamination of aerobic bacteria carrying tetracycline and sulfonamide antibiotic resistance genes.