Occurrence Of Resistance Genes Research Articles

Molecular Assessment of Resistance and Virulence Potential of Vibrio Species Isolated From Dumpsites in Port Harcourt, Nigeria

Background: Dumpsites have the potential to serve as reservoirs for various medically important bacteria and their virulence and resistance gene markers. For Vibrio spp., numerous genes associated with virulence have been identified in environmental strains. Due to the specific growth requirements of Vibrio spp., such strains can often be overlooked. This study aimed to assess the potential of Vibrio spp. isolated from two dumpsites in Port Harcourt, Nigeria, to serve as reservoirs of virulence and resistance genes. Methods: The soil samples were evaluated for the presence of Vibrio spp. following enrichment, using standard microbiological and biochemical test methods. DNA from Vibrio spp. was extracted using the boiling method, and isolates were tested for the presence of four resistance (sxt, strB, BlaTEM, and dfrA1) and four virulence (ctxA, hlyA, tcpA, and toxR) genes. Results: The study found a 40% occurrence of resistance genes and a 10% occurrence of virulence genes, with the strB streptomycin resistance gene being the most commonly detected (42%). Two of the virulence genes (ctxA and tcpA) were not detected. Seven of the test isolates exhibited multiple gene markers, with four gene markers present in each of two isolates. Conclusion: Overall, the study revealed a generally low potential for Vibrio sp. isolated from the dumpsites in Port Harcourt, Nigeria, to act as reservoirs of virulence and resistance genes. Additionally, the study reported an absence of major virulence markers associated with V. cholerae. A concerning finding was the high occurrence (42%) of the strB gene among these environmental isolates.

Isolation, antimicrobial resistance and virulence characterization of Salmonella spp. from fresh foods in retail markets in Hangzhou, China.

Salmonella can cause severe foodborne diseases. This study investigated the prevalence of Salmonella spp. in fresh foods in Hangzhou market and their harborage of antibiotic resistance and virulence genes, antibiotic susceptibility, and pathogenicity. A total of 500 samples (pork, n = 140; chicken, n = 128; vegetable, n = 232) were collected over a one-year period. Salmonella was found in 4.2% (21) of samples with the detection rate in pork, chicken and vegetables as 4.3% (6), 6.3% (8), and 3% (7), respectively. One Salmonella strain was recovered from each positive sample. The isolates were identified as six serotypes, of which S. Enteritidis (n = 7) and S. Typhimurium (n = 6) were the most predominant serotypes. The majority of isolates showed resistance to tetracycline (85.7%) and/or ciprofloxacin (71.4%). Tetracycline resistance genes showed the highest prevalence (90.5%). The occurrence of resistance genes for β-lactams (blaTEM-1, 66.7%; and blaSHV, 9.5%) and aminoglycosides (aadA1, 47.6%; Aac(3)-Ia, 19%) was higher than sulfonamides (sul1, 42.9%) and quinolones (parC, 38.1%). The virulence gene fimA was detected in 57.1% of isolates. Gene co-occurrence analysis implied that resistance genes were associated with virulence genes. Furthermore, selected S. Typhimurium isolates (n = 4) carrying different resistance and virulence genes up-regulated the secretions of cytokines IL-6 and IL-8 by Caco-2 cells in different degrees, suggesting that virulence genes may play a role in inflammatory transcription. In in vivo virulence test, microbiological counts in mouse feces and tissues showed that all included S. Typhimurium were able to infect mice, with one strain showing significantly higher virulence than others. In conclusion, this study indicates Salmonella contamination in fresh foods in Hangzhou market poses a risk to public health and it should be closely monitored to prevent and control foodborne diseases.

Antibiotic use in infants within the first year of life is associated with the appearance of antibiotic-resistant genes in their feces.

Antibiotic resistance, an increasing challenge, is not only a national threat but also a global threat. Carriage of resistance genes is not limited to adults alone, various microbiota niches present in the body system of children have been found to harbor bacteria carrying resistant genes, especially, their gut microbiota. This study aims to identify selected antibiotic-resistant genes from the fecal samples of infants and the association of antibiotics use with the occurrence of resistant genes in the infant's gut. A total number of 172 metagenomic DNA samples previously extracted from stool samples of 28 Nigerian babies longitudinally within their first year of life were screened for the presence of ESBL genes (blaSHV, blaTEM, and blaCTX-M), PMQR genes (qnrA, qnrB, qnrS, qepA), ribosomal protection protein tetracycline resistance gene, (RPP) β-lactamase (blaZ), macrolide (ermA, ermB, mefA/E), aminoglycoside modifying enzymes gentR (aac(6')/aph(2″)) and dfrA genes by PCR. Nineteen (19) of the 28 babies used antibiotics during the study. The association between antibiotic use by the babies within the first year of life and occurrence of resistant genes were analyzed by Spearman rank correlation. One hundred and twenty-two (122) samples (71%) out of the 172 isolates had antibiotic-resistance genes. PMQR genes were absent in all the samples. Three isolates had blaTEM gene, nine isolates had blaSHV gene, six isolates had blaCTX-M gene and 19 isolates had dfrA gene, 31 samples had tet gene, 29 samples had mef gene, 27 samples had ermB gene, four samples had ermA gene, 13 samples had blaZ gene and 16 samples had aac gene. The babies whose samples had resistant genes used antibiotics in the same months the samples were collected. Interestingly, the 11 babies whose samples had the dfrA gene all used antibiotics in the same months their samples were collected but none of them used trimethoprim/sulfamethoxazole antibiotic. The overall correlation matrix of the babies showed a strong association between antibiotic use (AU) and antibiotic use presence of resistance genes (AUPRG) with a coefficient of 0.89. Antibiotic-resistant genes are present in the gut of infants and their occurrence is strongly connected with antibiotic use by infants.

Molecular characterization of antimicrobial resistance related genes in E. coli, Salmonella and Klebsiella isolates from broilers in the West Region of Cameroon.

Antibiotic resistance has become an enduring threat to human health. This has prompted extensive research to identify the determinants responsible in a bid to fight the spread of resistance and also develop new antibiotics. However, routine procedures focus on identifying genetic determinants of resistance only on phenotypically resistant isolates. We aimed to characterise plasmid mediated resistance determinants in key Enterobacteriaceae isolates with differential phenotypic susceptibility profiles and evaluated the contribution of resistance genes on phenotypic expression of susceptibility. The study was carried out on 200 Enterobacteriaceae isolates belonging to the genera E. coli, Salmonella, and Klebsiella; 100 resistant and 100 susceptible to quinolones, aminoglycosides, and ESBL-producing as determined by disk diffusion. Reduced susceptibility in susceptible isolates was determined as an increased MIC by broth microdilution. Plasmid-borne resistance genes were sought in all isolates by endpoint PCR. We performed correlations tests to determine the relationship between the occurrence of resistance genes and increased MIC in susceptible isolates. We then used the notion of penetrance to show adequacy between resistance gene carriage and phenotypic resistance as well as diagnostic odds ratio to evaluate how predictable phenotypic susceptibility profile could determine the presence of resistant genes in the isolates. Reduced susceptibility was detected in 30% (9/30) ESBL negative, 50% (20/40) quinolone-susceptible and 53.33% (16/30) aminoglycoside-susceptible isolates. Plasmid-borne resistance genes were detected in 50% (15/30) of ESBL negative, 65% (26/40) quinolone susceptible and 66.67% (20/30) aminoglycoside susceptible isolates. Reduced susceptibility increased the risk of susceptible isolates carrying resistance genes (ORs 4.125, 8.36, and 8.89 respectively for ESBL, quinolone, and aminoglycoside resistance genes). Resistance gene carriage correlated significantly to reduced susceptibility for quinolone and aminoglycoside resistance genes (0.002 and 0.015 at CI95). Gene carriage correlated with phenotypic resistance at an estimated 64.28% for ESBL, 56.90% for quinolone, and 58.33% for aminoglycoside resistance genes. A high carriage of plasmid-mediated genes for ESBL, quinolone, and aminoglycoside resistance was found among the Enterobacteriaceae tested. However, gene carriage was not always correlated with phenotypic expression. This allows us to suggest that assessing genetic determinants of resistance should not be based on AST profile only. Further studies, including assessing the role of chromosomal determinants will shed light on other factors that undermine antimicrobial susceptibility locally.

Multi-Drug Resistance to Salmonella spp. When Isolated from Raw Meat Products.

Salmonella spp. is the most frequent cause of foodborne diseases, and the increasing occurrence of MDR strains is an additional and increasing problem. We collected Salmonella spp. strains isolated from meat (poultry and pork) and analysed their antibiotic susceptibility profiles and the occurrence of resistance genes. To determine the susceptibility profiles and identify MDR strains, we used two MIC methods (MICRONAUT and VITEC2 Compact) and 25 antibiotics. Phenotypic tests showed that 53.84% strains were MDR. Finally, molecular analysis strains revealed the presence of blaSHV, blaPSE-1, blaTEM, but not blaCTX-M genes. Moreover, several genes were associated with resistance to aminoglycosides, cephalosporins, fluorochinolones, sulfonamides, and tetracyclines. This suggests that further research on the prevalence of antibiotic resistance genes (ARGs) in foodborne strains is needed, especially from a One Health perspective.

Microorganisms from starter and protective cultures - Occurrence of antibiotic resistance and conjugal transfer of tet genes in vitro and during food fermentation

This study analyzed antibiotic resistance and the occurrence of resistance genes in strains from starter and protective cultures. The largest number of obtained strains belonged to the genus Lactobacillus (n = 26; 44.9%), followed by Lactococcus (n = 17; 29.3%), Pediococcus (n = 8; 13.8%), Streptococcus (n = 4; 6.9%), Staphylococcus (n = 2; 3.4%) and Leuconostoc (n = 1; 1.7%). Among all strains, the highest Minimum Inhibitory Concentrations (MICs) were noted for tetracycline (max. >256 μg/ml), kanamycin (max. 48 μg/ml) and chloramphenicol (max. 32 μg/ml). The most common resistance genes were aph(3’)-IIIa (n = 35; 60.3%) and cat (n = 32; 55.2%). Strains derived from starter and protective cultures have the ability to horizontally transfer resistance genes in vitro and in situ. It should be noted that antibiotic resistance of bacteria from starter and protective cultures does not present an immediate risk to consumers. However, these microorganisms could become an environmental reservoir of antibiotic resistance. The obtained results indicate that antibiotic resistance in starter and protective cultures is not a critical issue, however it creates a concern that cannot be ignored.

Research progress on lyophilization for pretreatment of emerging organic contaminants in environmental samples

有机新污染物是一类在先进分析技术帮助下新鉴定的、现有法规未管制的、人为源的有机污染物。有机新污染物主要包括药品与个人护理、农药、全氟化合物、内分泌干扰物等,其会产生内分泌干扰效应、诱发抗性基因传播,还对人类和野生生物的生存与发展构成潜在威胁,因此检测环境样品中的有机新污染物浓度对生态环境和人体健康具有重大意义。由于环境样品中的有机新污染物浓度较低,为了达到检测仪器的检测要求,通常需要对环境样品进行前处理,包括样品的净化和浓缩。冷冻干燥技术是一种在真空干燥条件下通过升华方式去除水分的前处理技术,主要包括样品冷冻、初级干燥和再干燥3个阶段,常用于食品和药品行业。在药品行业中,冷冻干燥技术能维持药品的生物活性和化学活性,保持药品的物理化学特性。近年来,冷冻干燥技术逐步用于环境水样中有机新污染物的前处理。其主要的操作步骤包括水样预处理、冷冻干燥、洗脱、吹干、过滤、定容和上机检测。冷冻干燥技术具有操作简单、低成本、样品处理体积少、样品易保存和处理过程中样品损失少等优点,具有广泛应用于环境样品中有机新污染物监测的潜力。该文综述了环境样品中有机新污染物常见的种类,并重点介绍冷冻干燥技术的原理及其在环境样品前处理过程中的应用,提出了冷冻干燥技术在环境分析中的应用前景,为环境样品中有机新污染物的监测提供了参考。

Occurrence of Virulence and Resistance Genes in Salmonella in Cloacae of Slaughtered Chickens and Ducks at Pluck Shops in Trinidad

The study used PCR to determine the molecular basis of the antibiotic resistance and virulence profiles of isolates of Salmonella by targeting genes encoding for carriage and persistence in the poultry. Of a total 1,503 cecal samples collected from poultry, 91 (6.1%) were positive for Salmonella. Ten different serotypes were detected from Salmonella isolates. The study was also conducted to determine the occurrence of 13 virulence and 12 resistance genes in isolates of Salmonella. All 46 isolates of Salmonella tested were positive for one or more of the 12 virulence genes detected, ranging from 0.0% (viaB) to 100.0% (invA, mgtB, pipA, and spi4D) (P < 0.05). Occurrence of virulence genes varied significantly (P < 0.05) by serotype but not by animal species. Only 4 (33.3%) of 12 resistance genes assayed were detected: strA, ampC, cmy2, and qnrB. Overall, the occurrence of detected resistance genes was 71.7% (33 of 46), and 87.1 and 40.0% of the isolates from chickens and ducks, respectively, were positive (P = 0.0009). The occurrence of resistance genes ranged from 2.2% (cmy2) to 50.0% (qnrB) in isolates positive for resistance gene. The findings provide evidence that poultry from "pluck shops" are colonized by Salmonella pathogens that harbor virulence and antimicrobial resistance genes; this may have clinical and therapeutic consequences, if the genes detected are expressed. Although there is a need for prudent use of antimicrobial agents in poultry production systems, there should be constant monitoring for the prevalence of resistance in Salmonella isolates using phenotypic methods. The importance of monitoring the occurrence of resistance genes in the pathogens in Trinidad cannot be ignored.

Genotyping of multi drug resistant Bacteroides fragilis group of clinical isolates from mangalore, south India

IntroductionBacteroides fragilis group, the most encountered anaerobic bacterium is emerging with resistance to antibiotics. This study explores the antibiogram and occurrence of resistance genes in isolates of B fragilis group from clinical samples. MethodIn this study the antimicrobial susceptibility test was done using commercially available E strip test and the results were recorded according to CLSI guidelines. Genotypic investigations were performed by conventional PCR to detect the target resistant genes. ResultsCeftriaxone, cefoxitin, clindamycin and imipenem were found to be the most resistant antimicrobials in E test method. Metronidazole has shown resistance in 7 strains in vitro while resistance nim genes were detected in 12 strains from 62 randomly selected isolates. Other resistance genes (cfiA, ermF and cepA) were expressed at 58%, 62.9% and 48.3% respectively, among these strains. ConclusionB fragilis group harbouring the resistant genes may not be fully expressed phenotypically. Hence, detection of these genes by PCR might be necessary for a pertinent conclusion.

Enterococci isolated from plant-derived food - Analysis of antibiotic resistance and the occurrence of resistance genes

This study analyzed phenotypic and molecular resistance to tetracyclines, macrolides, glycopeptides, aminoglycosides in Enterococcus strains isolated from plant-derived food. The study involved examining 270 food samples and 72 obtained Enterococcus sp. strains were isolated and identified as E. faecium, E. faecalis and E. casseliflavus. Most of them (55.6%) were resistant to streptomycin, followed by those resistant to rifampicin (51.4%), tigecycline (37.5%), erythromycin (36.1%) and fosfomycin (27.8%). More than half of the strains under analysis showed the high-level aminoglycoside resistance (HLAR) phenotype (55.6%). Resistance to aminoglycosides was associated mainly with the presence of the ant(6′)-Ia gene (54.2%), followed by the aph(3′)-IIIa gene (30.5%), and – to a small extent – with the presence of the aac(6′)-Ie-aph(2″)-la gene (8.3%). Resistance to tetracycline was caused mainly by the tetM (40.3%) and tetL (22.2%) genes and to macrolides - by ermB (33.3%) and ermA (11.1%). A conjugative transposon of the Tn916/Tn1545 family was present in nearly half (45.8%) of the isolates. The findings show that there is a need to monitor plant-derived food for the presence of antibiotic-resistant Enterococcus strains, because it can be a potential reservoir of genes encoding resistance to clinically important antibiotics.

Molecular characterization of multidrug-resistant avian pathogenic Escherichia coli from broiler chickens in Korea

This study was conducted to determine the phenotypic and genotypic characteristics of multidrug-resistant ( MDR ) avian pathogenic Escherichia coli ( APEC ). A total of 54 MDR APEC were divided into 23 serotypes, and O78 (16.6%) was the most frequently observed. The MDR APEC carried β-lactamase–encoding genes (38.9%), integrons (61.6%), plasmid-mediated quinolone–resistant genes (20.4%), tetracycline-resistant genes (79.6%), sulfonamide-resistant genes (40.7%), and chloramphenicol-resistant genes (18.5%). Phylogenetic group D (44.4%), which is associated with extraintestinal strains, was the most frequently observed, but all MDR APEC, including groups A, B1, and B2, carried one or more virulence genes. This study analyzed the phenotypic and genotypic characterization in MDR APEC isolated from broilers with colibacillosis in Korea. It is important to monitor the occurrence of resistance genes in APEC. These bacteria may pose serious therapeutic problems when treating sick broilers. The MDR strains carried by animals and birds can enter the human food chain through the consumption of meat or other animal or poultry products.

Antibiotic Resistance Genes in Antibiotic-Free Chicken Farms.

Rising concern about the use of antibiotics in food production has resulted in many studies on the occurrence of antibiotic resistance genes (ARGs) in animal-associated bacterial communities. There are few baseline data on the abundance of ARGs on farms where chickens are intensively raised with little or no use of antibiotics. This study used a high-throughput quantitative PCR array to survey two antibiotic-free chicken farms for the occurrence of ARGs and mobile genetic elements known to enhance the spread of ARGs. No antibiotics had been used on the study farms for five years prior to this study. The results provide a baseline for the occurrence of resistance genes in the chicken production system without direct selective pressure.

Intestinal microbiota domination under extreme selective pressures characterized by metagenomic read cloud sequencing and assembly

BackgroundLow diversity of the gut microbiome, often progressing to the point of intestinal domination by a single species, has been linked to poor outcomes in patients undergoing hematopoietic cell transplantation (HCT). Our ability to understand how certain organisms attain intestinal domination over others has been restricted in part by current metagenomic sequencing technologies that are typically unable to reconstruct complete genomes for individual organisms present within a sequenced microbial community. We recently developed a metagenomic read cloud sequencing and assembly approach that generates improved draft genomes for individual organisms compared to conventional short-read sequencing and assembly methods. Herein, we applied metagenomic read cloud sequencing to four stool samples collected longitudinally from an HCT patient preceding treatment and over the course of heavy antibiotic exposure.ResultsCharacterization of microbiome composition by taxonomic classification of reads reveals that that upon antibiotic exposure, the subject’s gut microbiome experienced a marked decrease in diversity and became dominated by Escherichia coli. While diversity is restored at the final time point, this occurs without recovery of the original species and strain-level composition. Draft genomes for individual organisms within each sample were generated using both read cloud and conventional assembly. Read clouds were found to improve the completeness and contiguity of genome assemblies compared to conventional assembly. Moreover, read clouds enabled the placement of antibiotic resistance genes present in multiple copies both within a single draft genome and across multiple organisms. The occurrence of resistance genes associates with the timing of antibiotics administered to the patient, and comparative genomic analysis of the various intestinal E. coli strains across time points as well as the bloodstream isolate showed that the subject’s E. coli bloodstream infection likely originated from the intestine. The E. coli genome from the initial pre-transplant stool sample harbors 46 known antimicrobial resistance genes, while all other species from the pre-transplant sample each contain at most 5 genes, consistent with a model of heavy antibiotic exposure resulting in selective outgrowth of the highly antibiotic-resistant E. coli.ConclusionThis study demonstrates the application and utility of metagenomic read cloud sequencing and assembly to study the underlying strain-level genomic factors influencing gut microbiome dynamics under extreme selective pressures in the clinical context of HCT.

Antibiotic Resistance of LACTOBACILLUS Strains.

The study provides phenotypic and molecular analyses of the antibiotic resistance in 20 Lactobacillus strains including 11 strains newly isolated from fermented plant material. According to the results of disc diffusion method, 90% of tested lactobacilli demonstrated sensitivity to clindamycin and 95% of strains were susceptible to tetracycline, erythromycin, and rifampicin. Ampicillin and chloramphenicol were found to inhibit all bacteria used in this study. The vast majority of tested strains revealed phenotypic resistance to vancomycin, ciprofloxacin, and aminoglycosides. Most of Lactobacillus strains showed high minimum inhibitory concentrations (MICs) of cefotaxime, ceftriaxone, and cefazolin and therefore were considered resistant to cephalosporins. All the strains exhibited multidrug resistance. The occurrence of resistance genes was associated with phenotypic resistance, with the exception of phenotypically susceptible strains that contained genes for tetracycline (tetK, tetL) and erythromycin (ermB, mefA) resistance. The vanX gene for vancomycin resistance was among the most frequently identified among the lactobacilli (75% of strains), but the occurrence of the parC gene for ciprofloxacin resistance was sporadic (20% of strains). Our results mainly evidence the intrinsic nature of the resistance to aminoglycosides in lactobacilli, though genes for enzymatic modification of streptomycin aadA and aadE were found in 20% of tested strains. The occurrence of extended spectrum beta-lactamases (ESBL) was unknown in Lactobacillus, but our results revealed the blaTEM gene in 80% of strains, whereas blaSHV and blaOXA-1 genes were less frequent (20% and 15% of strains, respectively).

Identification and antibiotic susceptibility of lactobacilli isolated from turkeys

BackgroundThe aim of this study was to identify Lactobacillus isolates derived from turkeys from six Polish farms and to characterize their phenotypic and genotypic antibiotic resistance profiles.ResultsAmong 62 isolates identified by MALDI-TOF mass spectrometry and restriction analysis of 16S rDNA, the dominant species was L. salivarius (35%), followed by L. crispatus (21%), L. ingluviei (14.5%) and L. johnsonii (10%). A high prevalence of resistance to tetracycline (68% resistant isolates), lincomycin (64.5%) and enrofloxacin (60%) among the lactobacilli tested was observed. Fewer than 50% isolates were resistant to ampicillin (47%), erythromycin (45%), streptomycin (31%), chloramphenicol (29%) and gentamicin (10%). As many as 64,5% of the isolates showed multidrug resistance. High MIC values for ampicillin (≥64 μg/ml) were usually accompanied by elevated MICs for cephalosporins (≥16 μg/ml) and high MICs for tiamulin, i.e. ≥32 μg/ml, were noted in most of the turkey lactobacilli (61%). The occurrence of resistance genes was associated with phenotypic resistance, with the exception of five phenotypically susceptible isolates that contained the tetM, tetL, ermC, ermB or cat genes. The most frequently identified were ermB (45% isolates), tetL (40%), tetW (37%) and tetM (29%), and the occurrence of lnuA (18%), cat (10%), ermC (6%), ant(6)-Ia (5%) and aadE (5%) was less frequent. The mechanism of ampicillin resistance has not been elucidated, but the results of nitrocefin test confirmed that it is not involved in the production of beta-lactamases.ConclusionsThe high rate of antibiotic resistance observed in this study indicates the need to implement the principles of rational use of antibiotics in poultry. The presence of transmissible resistant genes in lactobacilli may contribute to the development of antibiotic resistant pathogenic strains that pose a threat to both poultry and consumers. The results of these studies may be useful for committees providing guidance on antibiotic susceptibility of microorganisms in order to revise and supplement current microbiological cut-offs values within the genus Lactobacillus.

Phenotypic and genotypic characterization of antimicrobial resistance profiles in Streptococcus dysgalactiae isolated from bovine clinical mastitis in 5 provinces of China

Bovine mastitis is among the most prevalent and costly diseases of dairy animals and is caused by a variety of bacterial pathogens including Streptococcus dysgalactiae. However, comprehensive studies reporting the prevalence and antimicrobial resistance profiles of S. dysgalactiae isolated from bovine mastitis are scarce. Therefore, this study was to investigate the occurrence of S. dysgalactiae associated with bovine clinical mastitis, to assess their antimicrobial resistance profiles, and to analyze the phenotypic and genotypic profiling of resistant isolates. In total, 1,180 milk samples were collected from dairy cows with clinical mastitis belonging to 74 commercial dairy herds located in 14 provinces of China from January 2014 to May 2016. Overall S. dysgalactiae isolates were recovered from 88 (7.5%) of the mastitic milk samples. The antimicrobial susceptibility of these isolates was tested against 8 antimicrobial agents by using minimum inhibitory concentrations. Results showed that 82 (93.2%) isolates expressed resistance to more than one antimicrobial agent. Antimicrobial resistance was highest against kanamycin (89.8%), sulfonamide (83.0%), and streptomycin (58.0%), which can be attributed to the intrinsic resistance for most of Streptococcus spp. against those antimicrobial substances. Strikingly, 30 (34.1%) and 12 (13.6%) isolates were found resistant to cephalexin and ceftriaxone, respectively. BlaTEM, ermB, and tetM were the most prevalent resistance genes. All isolates carried at least one of all tested resistance genes. Also, 1.1, 12.5, 18.2, 36.4, and 31.8% of isolates were positive for at least one tested resistance gene in 1, 2, 3, 4, or 5 classes of antimicrobials. Survival analysis showed a significant association between ermB and survival of the S. dysgalactiae isolates at increasing erythromycin concentrations. No other statistically significant associations were observed between the phenotypic and genotypic resistance profiles. This study concludes a considerable prevalence of S. dysgalactiae associated with bovine mastitis in dairy herds of China and these isolates exhibited high resistance rates to tested antimicrobials, coupled with high occurrence of resistance genes. Both the prevalence of S. dysgalactiae and their antimicrobial resistance profiles strongly varied among dairy herds, demonstrating the need for antimicrobial susceptibility surveillance at the herd level to ensure optimal therapeutic results.

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.

Extended-Spectrum Beta-Lactamase-/AmpC Beta-Lactamase-Producing Enterobacteriaceae in Broiler Farms: Transmission Dynamics at Farm Level.

The occurrence of extended-spectrum beta-lactamase- (ESBL) and/or AmpC beta-lactamase- (AmpC) producing Enterobacteriaceae in livestock, especially in broiler fattening flocks, has been demonstrated in previous studies. Nevertheless, data on transmission routes of these resistant bacteria into the fattening farms are rare. Therefore, seven broiler fattening flocks were investigated for the occurrence of ESBL-/AmpC-producing Enterobacteriaceae during the course of the fattening period with the special focus on horizontal transmission routes. ESBL-/AmpC-producing Enterobacteriaceae from both individual animals and their housing environment were isolated at different time points and the housing environment was even sampled before the arrival of the chickens. All obtained ESBL-/AmpC-producing Enterobacteriaceae were examined for their bacterial species, Escherichia coli phylogroup, and occurrence of resistance genes. Selected isolates were further analyzed via whole-genome sequencing. All seven investigated flocks were tested positive for ESBL-/AmpC-producing Enterobacteriaceae with widely varying prevalence between the flocks. In one flock, the ESBL-/AmpC-producing Enterobacteriaceae were already detected in the housing environment before the arrival of the animals. In general, among the different types of ESBL-/AmpC-producing Enterobacteriaceae determined E. coli harboring a blaCMY-2 gene was the most frequent. Using whole-genome analyses we observed a horizontal transmission of ESBL-/AmpC-producing Enterobacteriaceae through contaminated housing environment as two flocks consecutively fattened in the same farm harbored closely related ESBL-producing isolates. This demonstrates the influence of a previous fattened flock on the ESBL-/AmpC-status of a following broiler flock and, therefore, the importance of hygiene measures on farm level.

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.

Antibiotic susceptibility and molecular characterization of resistance genes among Escherichia coli and among Salmonella subsp. in chicken food chains

ObjectiveTo investigate the occurrence of resistance genes among Escherichia coli (E. coli) and Salmonella subsp. isolated in chicken food chains in Phnom Penh, 2012–2013. MethodsSix hundred eighty two E. coli and 181 Salmonella Albany, Corvallis, and Kentucky strains were examined for susceptibilities to eight antimicrobials and following resistance genes were identified by PCR: blaTem, StrA, aadA, sul1, sul2, gyrA, Tet (A), and Tet (B). ResultsE. coli presented high resistances to tetracycline, amoxicillin, and sulfamethoxazole (63.1%–76.1%). Salmonella Albany and Salmonella Kentucky traduced high resistance percentages to amoxicillin, tetracycline, sulfamethoxazole, and nalidixic acid (84.6%–100%). Among amoxicillin-resistant isolates, blaTem genes were observed for 62% of E. coli isolates and 20% of 65 Salmonella Kentucky. The StrA gene was prevalent in 36% of 331 aminoglycoside-resistant E. coli and 90% of 40 aminoglycoside-resistant Salmonella Corvallis. The sul2 gene was predominant among sulfamethoxazole-resistant isolates, for 56% of 431 E. coli and 53% of 66 Salmonella Corvallis; the sul1 gene was observed in 54% of Salmonella Albany. The Tet (A) resistance gene was prevalent in E. coli (86%), Salmonella Corvallis (82%), Salmonella Kentucky (84%). High percentages of gyrA genes observed among nalidixic-acid resistant E. coli (91%), Salmonella Albany (92%), Salmonella Corvallis (75%) and Salmonella Kentucky (85%). ConclusionsImportant occurrences of resistance gene were observed among E. coli and Salmonella in chicken food chains in Cambodia.