Resistance Genes floR Research Articles

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

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 (284bp), two Salmonella pathogenicity island 2 (SPI-2) genes ssaT (780bp) and sseF (888bp) and three antibiotic resistance genes floR (198bp), sul1 (425bp), tetG (550bp) 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.

Genetic analysis of multiple antimicrobial resistance in Salmonella isolated from diseased broilers in Egypt

To date, no information has been available on the molecular bases of antimicrobial resistance in Salmonella spp. from poultry in Egypt or even in Africa. Therefore, the objective of this study was to analyze, at the molecular level, the mechanisms of multidrug-resistance in isolates of Salmonella recovered from diseased broilers in Egypt. Twenty-one Salmonella isolates were identified; 13 of these isolates were Salmonella enterica serovar Enteritidis and eight Salmonella enterica serovar Typhimurium. 17 (81%). Salmonella isolates displayed multidrug resistance phenotypes, particularly against ampicillin, streptomycin, spectinomycin, kanamycin, tetracycline, chloramphenicol, and trimethoprim/sulfamethoxazole. PCR and DNA sequencing identified class 1 integrons in nine (42.9%) isolates and class 2 integrons in three (14.3%) isolates. The identified resistance genes within class 1 integrons were aminoglycoside adenyltransferase type A, aadA1, aadA2 and aadA5 and dihydrofolate reductase type A, dfrA1, dfrA5, dfrA12, dfrA15 and dfrA17. The β-lactamase encoding genes bla(TEM-1) and bla(CMY-2) and florfenicol resistance gene floR were also identified. Furthermore, the tetracycline resistance gene tet(A) was identified in 14 (66.7%) Salmonella isolates. To the best of our knowledge, this is the first report of the molecular basis of antimicrobial resistance in Salmonella spp. isolated from poultry in Africa.

Prevalence of Antimicrobial Resistance Among Salmonella Isolates from Chicken in China

We evaluated the antimicrobial resistance of Salmonella isolated in 2008 from a chicken hatchery, chicken farms, and chicken slaughterhouses in China. A total of 311 Salmonella isolates were collected from the three sources, and two serogroups of Salmonella were detected, of which 133 (42.8%) consisted of Salmonella indiana and 178 (57.2%) of Salmonella enteritidis. The lowest percentage of S. indiana isolates was found in the chicken hatchery (4.2%), followed by the chicken farms (54.9%) and the slaughterhouses (71.4%). More than 80% of the S. indiana isolates were highly resistant to ampicillin (97.7%), amoxicillin/clavulanic acid (87.9%), cephalothin (87.9%), ceftiofur (85.7%), chloramphenicol (84.9%), florfenicol (90.9%), tetracycline (97.7%), doxycycline (98.5%), kanamycin (90.2%), and gentamicin (92.5%). About 60% of the S. indiana isolates were resistant to enrofloxacin (65.4%), norfloxacin (78.9%), and ciprofloxacin (59.4%). Of the S. indiana isolates, 4.5% were susceptible to amikacin and 5.3% to colistin. Of the S. enteritidis isolates, 73% were resistant to ampicillin, 33.1% to amoxicillin/clavulanic acid, 66.3% to tetracycline, and 65.3% to doxycycline, whereas all of these isolates were susceptible to the other drugs used in the study. The S. indiana isolates showed resistance to 16 antimicrobial agents. Strains of Salmonella (n = 108) carrying the resistance genes floR, aac(6')-Ib-cr, and bla(TEM) were most prevalent among the 133 isolates of S. indiana, at a frequency of 81.2%. The use of pulsed-field gel electrophoresis to analyze the S. indiana isolates that showed similar antimicrobial resistance patterns and carried resistance genes revealed six genotypes of these organisms. Most of these isolates had the common pulsed-field gel electrophoresis patterns found in the chicken hatchery, chicken farms, and slaughterhouses, suggesting that many multidrug-resistant isolates of S. indiana prevailed in the three sources. Some of these isolates were not derived from a specific clone, but represented a variety of genotypes of S. indiana.

Structural and functional study of the phenicol-specific efflux pump FloR belonging to the major facilitator superfamily.

The florfenicol-chloramphenicol resistance gene floR from Salmonella enterica was previously identified and postulated to belong to the major facilitator (MF) superfamily of drug exporters. Here, we confirmed a computer-predicted transmembrane topological model of FloR, using the phoA gene fusion method, and classified this protein in the DHA12 family (containing 12 transmembrane domains) of MF efflux transporters. We also showed that FloR is a transporter specific for structurally associated phenicol drugs (chloramphenicol, florfenicol, thiamphenicol) which utilizes the proton motive force to energize an active efflux mechanism. By site-directed mutagenesis of specific charged residues belonging to putative transmembrane segments (TMS), two residues essential for active efflux function, D23 in TMS1 and R109 in TMS4, were identified. Of these, the acidic residue D23 seems to participate directly in the affinity pocket involved in phenicol derivative recognition. A third residue, E283 in TMS9, seems to be necessary for correct membrane folding of the transporter.

642 Use of high dose fractionated cyclophosphamide and coordinated high dose methotrexate and cytarabine in childhood B cell Non Hodgkin's Lymphoma

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.