Identification and Characterization of Class 1 Integron Resistance Gene Cassettes among Salmonella Strains Isolated from Imported Seafood (original) (raw)

Simultaneous detection of Salmonella pathogenicity island 2 and its antibiotic resistance genes from seafood

Journal of Microbiological Methods, 2013

Salmonella enterica serovars are virulent pathogens of humans and animals with many strains possessing multiple drug resistance traits. They have been found to carry resistance to ampicillin, chloramphenicol, florfenicol, streptomycin, sulfonamides, and tetracycline (ACSSuT-resistant). A rapid and sensitive multiplex PCR (mPCR)-based assay was developed for the detection of Salmonella serovars from seafood. Six sets of primers which are one primer pair targeting Salmonella specific gene invA (284 bp), two Salmonella pathogenicity island 2 (SPI-2) genes ssaT (780 bp) and sseF (888 bp) and three antibiotic resistance genes floR (198 bp), sul1 (425 bp), tetG (550 bp) were used for the study. The specificity and sensitivity of the assay were tested by spiking shrimp/fish/clam homogenate with viable cells of Salmonella. This assay allows for the cost effective and reliable detection of pathogenic Salmonella enterica from seafood. The mPCR developed in the present study proved to be a potent analytical tool for the rapid identification of multidrug-resistant Salmonella serovars from seafood.

Unique Class 1 Integron and Multiple Resistance Genes Co-located on IncHI2 Plasmid Is Associated with the Emerging Multidrug Resistance of Salmonella Indiana Isolated from Chicken in China

Foodborne Pathogens and Disease, 2013

The objective of this study was to clarify the molecular antimicrobial resistance mechanisms of Salmonella enterica serovar Indiana isolated from chickens in China. A total of 327 chicken intestinal content and feces were collected in Shandong, China in 2009. Isolates were serotyped and antimicrobial susceptibility testing was performed. Thirty-five (10.7%) Salmonella isolates were recovered, and 16 (45.7%) were Salmonella enterica serovar Indiana, which were resistant to at least 14 of 15 antimicrobial agents. The 16 Salmonella enterica serovar Indiana detected and other 13 Salmonella enterica serovar Indiana that were selected from 133 Salmonella enterica serovar Indiana isolated in 2008 were subjected to pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Then class 1 integron and drug resistance genes were detected by polymerase chain reaction. Linkage between plasmids and resistance components was determined by conjugation, electrotransformation, S1 nuclease-PFGE, polymerase chain reaction-based replicon typing and Southern blot assays. Regions flanking integrons were sequenced by modified random primer walking strategy. PFGE and MLST suggested that all the 29 Salmonella enterica serovar Indiana isolates that shared > 78% similarity in PFGE patterns were of the same MLST type, ST17. Two kinds of class 1 integrons had different integrase genes and the same variable region (dfrA7/aadA4/IS26/aac(6¢)-Ib/bla OXA-1 /catB3/arr-3), and additional antimicrobial resistance genes such as bla CTX-M-24 , floR, and so on were detected on IncHI2 plasmids in 29 Salmonella enterica serovar Indiana, and seven plasmids were conjugative. Analysis of the genetic environment of the integrons suggested that these integrons might have been formed by the help of IS26. To our knowledge, the variable region in class 1 integrons is the longest reported in Salmonella to date. The unique integrons and multiple resistance genes co-located on the IncHI2 plasmid contributed to the dissemination of multidrug resistance.

Molecular Detection of Antimicrobial Resistance Gene Cassettes Associated with Class 2 Integron in Salmonella Serovars Isolated in Iran

British Microbiology Research Journal, 2014

This study was carried out to detect the distribution of antibiotic-resistant genes in Escherichia coli isolates from slaughtered commercial chickens in Iran by PCR. The investigated genes included aadA1, tet(A), tet(B), dfrA1, qnrA, aac(3)-IV, sul1, bla SHV , bla CMY , ere(A), catA1 and cmlA. According to biochemical experiments, 57 isolates from 360 chicken meat samples were recognized as E. coli. The distribution of antibiotic-resistance genes in the E. coli isolates included tet(A) and tet(B) (52.63%), dfrA1, qnrA, catA1 and cmlA (36.84%) and sul1 and ere(A) (47.36%), respectively. Nine strains (15.78%) were resistant to a single antimicrobial agent and 11 strains (19.29%) showed resistance to two antimicrobial agents. Multi-resistance which was defined as resistance to three or more tested agents was found in 64.91% of E. coli strains. The results indicate that all isolates harbour one or more of antibiotic resistance genes and that the PCR technique is a fast, practical and appropriate method for determining the presence of antibiotic-resistance genes.

Molecular Characterization of Salmonella enterica and detection of antimicrobial resistance genes

Salmonella Typhimurium is an important nontyphoidal Salmonella serovar associated with foodborne diseases in many parts of the world. This organism is the major causative agent of nontyphoidal salmonellosis in Malaysia. We aimed to investigate the genetic profiles of the strains isolated from clinical, zoonotic, and dietary sources in Malaysia using multilocus variable number tandem repeat analysis (MLVA) and pulsed-field gel electrophoresis (PFGE). By focusing on the 5 common variable number tandem repeat (VNTR) loci, we found that PFGE (D = 0.99) was more discriminative than MLVA (D = 0.76). The low MLVA score might be because of a lack of VNTR loci STTR6 (81.0z) and STTR10pl (76.2z). Both subtyping methods suggested that our S. Typhimurium strains were largely endemic with limited genetic variation. Furthermore, we observed that biphasic S. Typhimurium strains were dominant (99z) and multidrug resistance was prevalent (50z) within our sample pool. The most frequently observed phenotypes were resistance to compound sulfonamides (49z), tetracycline (51z), and streptomycin (52z). In this study, we documented the genetic relationship, antimicrobial resistance characteristics, and flagellar-phase dominance among S. Typhimurium strains found in Malaysia.

Molecular characterization of Salmonella enterica serovar Saintpaul isolated from imported seafood, pepper, environmental and clinical samples

Food Microbiology, 2011

A total of 39 Salmonella enterica serovar Saintpaul strains from imported seafood, pepper and from environmental and clinical samples were analyzed for the presence of virulence genes, antibiotic resistance, plasmid and plasmid replicon types. Pulsed-field gel electrophoresis (PFGE) fingerprinting using the XbaI restriction enzyme and plasmid profiling were performed to assess genetic diversity. None of the isolates showed resistance to ampicillin, chloramphenicol, gentamicin, kanamycin, streptomycin, sulfisoxazole, and tetracycline. Seventeen virulence genes were screened for by PCR. All strains were positive for 14 genes (spiA, sifA, invA, spaN, sopE, sipB, iroN, msgA, pagC, orgA, prgH, lpfC, sitC, and tolC) and negative for three genes (spvB, pefA, and cdtB). Twelve strains, including six from clinical samples and six from seafood, carried one or more plasmids. Large plasmids, sized greater than 50 kb were detected in one clinical and three food isolates. One plasmid was able to be typed as IncI1 by PCR-based replicon typing. There were 25 distinct PFGE-XbaI patterns, clustered to two groups. Cluster A, with 68.5% similarity mainly consists of clinical isolates, while Cluster C, with 67.6% similarity, mainly consisted of shrimp isolates from India. Our findings indicated the genetic diversity of S. Saintpaul in clinical samples, imported seafood, and the environment and that this serotype possesses several virulent genes and plasmids which can cause salmonellosis.

Class 1 integron-borne multiple-antibiotic resistance carried by IncFI and IncL/M plasmids in Salmonella enterica serotype typhimurium

Antimicrobial agents and chemotherapy, 1998

The presence and genetic content of integrons were investigated for 37 epidemiologically unrelated multiple-drug-resistant strains of Salmonella enterica serotype Typhimurium from humans. All isolates were resistant to ampicillin, chloramphenicol, kanamycin, streptomycin, sulfonamides, and trimethoprim, as well as to tetracycline and/or nalidixic acid; 20% of them were also resistant to gentamicin and amikacin. Three different class 1 integrons (In-t1, In-t2, and In-t3) were identified by Southern blot hybridization, PCR, and DNA sequencing, and these integrons were found to carry the aadB, catB3, oxa1, aadA1a, aacA4, and aacC1 gene cassettes. Integrons In-t1 (aadB and catB3) and In-t2 (oxa1 and aadA1a) were both located on a conjugative IncFI plasmid of 140 kb. In-t3 (aacA4, aacC1, and aadAIa) was located on an IncL/M plasmid of 100 kb which was present, in association with the IncFI plasmid, in gentamicin- and amikacin-resistant isolates. Despite the extensive similarity at the le...

Integron-Associated Antibiotic Resistance in Salmonella enterica Serovar Typhi from Asia

Antimicrobial Agents and Chemotherapy, 2003

Eighteen of 25 isolates of Salmonella enterica serovar Typhi were multidrug resistant and contained class 1 integrons with a single cassette, dfrVII or aadA1. The dfrVII-containing integron was likely borne on an IncHI1 plasmid. Salmonella serovar Typhi could become resistant to broad-spectrum cephalosporins by integrating cassettes, such as veb-1, a common cassette in Asia.

Molecular Clonality and Detection of Class 1 Integron in Multidrug-Resistant Salmonella enterica Isolates from Animal and Human in Iran

Microbial Drug Resistance, 2014

A total of 70 multidrug-resistant (MDR) Salmonella isolates (44 human and 26 poultry) were examined. The conserved segment-PCR, restriction fragment length polymorphism-PCR analysis, and DNA sequencing were used to determine the presence and cassette content of integrons. The genetic relatedness among the isolates was examined by pulsed-field gel electrophoresis (PFGE). The rate of integron carriage for MDR Salmonella isolates was 91.4% and integron-positive isolates belonged to six distinct serovars. Out of 64 integron-positive isolates, only four Salmonella Paratyphi C isolates could transfer integrons to Escherichia coli K12 by conjugation. Thirty-three PFGE types were detected in 52 integron-positive isolates, including 22, 4, 3, 2, 1, and 1 patterns among Salmonella serovars Enteritidis, Typhimurium, Paratyphi C, Paratyphi B, Paratyphi A, and Havana, respectively. The human and poultry Salmonella Enteritidis isolates from different regions with identical integrons had closely related PFGE patterns. Of the four integron-positive Salmonella Typhimurium isolates, the two poultry isolates with identical integron had very closely related PFGE patterns whereas the two human isolates with different integrons showed unrelated PFGE patterns. PFGE showed undistinguishable patterns in Salmonella Paratyphi C isolates with identical cassettes but revealed relatively unrelated patterns in those with different cassettes. Relatively unrelated and identical PFGE patterns were found in two Salmonella Paratyphi B and three Salmonella Paratyphi A isolates with the same integrons, respectively. In conclusion, PFGE patterns demonstrated more genetic relatedness among each Salmonella serovar with identical class 1 integrons than the same serovar with different class 1 integrons.

Antimicrobial Resistance and Spread of Class 1 Integrons among Salmonella Serotypes

Antimicrobial Agents and Chemotherapy, 2000

The resistance profiles, for 15 antimicrobial agents, of 333 Salmonella strains representing the most frequent nontyphoidal serotypes, isolated between 1989 and 1998 in a Spanish region, and 9 reference strains were analyzed. All strains were susceptible to amikacin, ceftazidime, ciprofloxacin, and imipenem, and 31% were susceptible to all antimicrobials tested. The most frequent types of resistance were to sulfadiazine, tetracycline, streptomycin, spectinomycin, ampicillin, and chloramphenicol (ranging from 46 to 22%); 13% were resistant to these six drugs. This multidrug resistance pattern was found alone or together with other resistance types within serotypes Typhimurium (45%), Panama (23%), and Virchow (4%). Each isolate was also screened for the presence of class 1 integrons and selected resistance genes therein; seven variable regions which carried one (aadA1a, aadA2, or pse-1) or two (dfrA14-aadA1a, dfrA1-aadA1a, oxa1-aadA1a, or sat1-aadA1a) resistance genes were found in integrons.