Assessment of anti-Salmonella activity of boot dip samples.

The introduction of pathogens from the external environment into poultry houses via the boots of farm workers and visitors presents a significant risk. The use of boot dips containing disinfectant to help prevent this from happening is common practice, but the effectiveness of these boot dips as a preventive measure can vary. The aim of this study was to assess the anti-Salmonella activity of boot dips that are being used on poultry farms. Boot dip samples were collected from commercial laying hen farms in the UK and tested within 24 hours of receipt at the laboratory to assess their anti-Salmonella activity. All boot dip samples were tested against a field strain of Salmonella enterica serovar Enteritidis using three test models: pure culture, paper disc surface matrix and yeast suspension model. Of the 112 boot dip samples tested 83.6% were effective against Salmonella in pure culture, 37.3% in paper disc surface matrix and 44.5% in yeast suspension model. Numerous factors may influence the efficacy of the disinfectants. Disinfectants used in the dips may not always be fully active against surface or organic matter contamination; they may be inaccurately measured or diluted to a concentration other than that specified or recommended; dips may not be changed regularly or may have been exposed to rain and other environmental elements. This study showed that boot dips in use on poultry farms are frequently ineffective.

Epidemiological investigation of Salmonella enterica serovar Kedougou in Thailand.

OBJECTIVE: Salmonella enterica serovar Kedougou is among the top 10 serovars reported in northern Thailand. The objective of this study was to identify risk factors associated with Salmonella Kedougou infection in Thailand and to compare the molecular types and antimicrobial resistance with Salmonella Kedougou isolates of human origin from United States and of animal origin from the United Kingdom. METHODS: Data from 13,976 Salmonella infections of which 253 were Salmonella Kedougou collected in Thailand between 2002 and 2008 were analyzed by logistic regression. Antimicrobial susceptibility testing and pulsed-field gel electrophoresis (PFGE) were performed on selected Salmonella Kedougou strains causing infections in Thailand (n = 66), and compared to isolates from the United States (n = 5) and the United Kingdom (n = 20). RESULTS: Logistic analysis revealed season (hot/dry; p = 0.023), region (northern Thailand; p < 0.001), and specimen (stool; p < 0.001) as significant risk factors associated with Salmonella Kedougou infection compared to other nontyphoid Salmonella. Of the Salmonella Kedougou isolates of human origin, 84% exhibited resistance to at least three antimicrobial classes. Three strains recovered from human stool in Thailand were resistant to third-generation cephalosporins: two harbored bla(CTX-M-63) and one bla(CMY-2). PFGE revealed 45 unique clusters. Isolates obtained from humans in Thailand and the United States presented identical PFGE profiles suggesting a travel association, whereas the majority of the animal isolates from United Kingdom clustered separately. CONCLUSIONS: This study reveals Salmonella Kedougou as a major cause of human infections in northern Thailand especially during the hot period and suggests a global spread probably due to travel. The clonal types causing infections in humans differed from those observed in animals in United Kingdom, which suggests the absence of an epidemiological link and could suggest differences in virulence. The high frequency of antimicrobial resistance, including emergence of resistance to fluoroquinolones and third-generation cephalosporins, might pose problems for treatment of infections.

Characterization of pathogenic and resistant genome repertoire reveals two clonal lines in Salmonella enterica subsp. enterica serovar Paratyphi B (+)-tartrate positive.

A total of 36 contemporary human, animal, and environmental (+)-tartrate-fermenting (dT+) Salmonella enterica serovar Paratyphi B isolates, formerly called Salmonella serovar Java, and five related monophasic S. enterica serovar 4,5,12:b:- isolates from Belgium, Germany, the Netherlands, and the United Kingdom were investigated for clonality and antimicrobial resistance profiles, as well as their virulence and resistance gene repertoire. Two major clonal lines, which could be phenotypically differentiated by the expression of the O:5 antigen, were identified. All O:5 antigen negative strains were multidrug resistant and originated (with two exceptions) from Belgian, Dutch, or German poultry. Strains exhibiting the O:5 antigen encoded by the oafA gene revealed a more heterogeneous group including multidrug-resistant and susceptible strains. Compared to O:5 antigen negative isolates, Salmonella Paratyphi B dT+ O:5 positive strains possessed additional virulence determinants. The Salmonella genomic island 1 was only found in O:5 positive strains. Five monophasic Salmonella 4,5,12:b:- lacking the phase-2 flagellar antigen were assigned to Salmonella Paratyphi B dT+ isolates of the O:5 positive group. The conclusion of the analysis is that Salmonella Paratyphi B dT+ O:5 negative and O:5 positive isolates evolved from a different lineage. Salmonella Paratyphi B dT+ O:5 positive strains possess additional fimbrial and virulence genes that probably enable this clone to interact with a broader range of hosts and the environment. Salmonella Paratyphi B dT+ O:5 negative continuously persists in poultry across Western Europe, especially Belgium, the Netherlands, and Germany.

Development of a miniaturised microarray-based assay for the rapid identification of antimicrobial resistance genes in Gram-negative bacteria.

We describe the development of a miniaturised microarray for the detection of antimicrobial resistance genes in Gram-negative bacteria. Included on the array are genes encoding resistance to aminoglycosides, trimethoprim, sulphonamides, tetracyclines and beta-lactams, including extended-spectrum beta-lactamases. Validation of the array with control strains demonstrated a 99% correlation between polymerase chain reaction and array results. There was also good correlation between phenotypic and genotypic results for a large panel of Escherichia coli and Salmonella isolates. Some differences were also seen in the number and type of resistance genes harboured by E. coli and Salmonella strains. The array provides an effective, fast and simple method for detection of resistance genes in clinical isolates suitable for use in diagnostic laboratories, which in future will help to understand the epidemiology of isolates and to detect gene linkage in bacterial populations.

Comparison of antimicrobial resistance genes in nontyphoidal salmonellae of serotypes enteritidis, hadar, and virchow from humans and food-producing animals in England and wales.

Isolates of Salmonella enterica serovars Enteritidis (n = 17), Hadar (n = 18), and Virchow (n = 13) from cases of human infection and from food production animals were screened using a miniaturized antimicrobial microarray to determine the number and spectra of resistance genes. Among Enteritidis, the number of genes detected was: animal isolates, mean = 4.6; human isolates, mean = 5.3. Resistance to streptomycin, trimethoprim, and sulfonamides was usually encoded by only one resistance gene in animal isolates, but human isolates often carried more than one gene encoding resistance to the same class of antimicrobial. Among Hadar, the number of genes detected was: animal isolates, mean = 2.0; human strains, mean = 2.6. Resistance to streptomycin was encoded by strA, rather than aadA genes because these were detected in only one human isolate. Among Virchow, the number of genes detected was: animal isolates, mean = 1.6; human isolates, mean = 5.6. As with Enteritidis, human Hadar isolates often carried more than one gene encoding resistance to the same class of antimicrobial. Due to the complexity of routes of transmission of Salmonella spp. from food production animals to humans, full phenotypic and genotypic comparison of resistant isolates is critical in ascertaining the sources of resistant isolates.

Characterization of beta-lactamases responsible for resistance to extended-spectrum cephalosporins in Escherichia coli and Salmonella enterica strains from food-producing animals in the United Kingdom.

Nine epidemiologically unrelated isolates [1 Salmonella Bredeney from turkeys, and 8 Escherichia coli [3 environmental isolates (2 from chickens, 1 from pigs), and 5 isolates from cattle with neonatal diarrhea]] were examined both pheno- and genotypically for extended-spectrum beta-lactam (ESBL) resistance. Resistance phenotypes (ampicillin, aztreonam, cefotaxime, cefpodoxime, ceftazidime, and ceftriaxone) suggested the presence of an ESBL enzyme, but cefoxitin MICs (>/= 32 mg/L) suggested the presence of an AmpC-like enzyme. Synergism experiments with benzo(b)thiophene-2-boronic acid (BZBTH2B) and isoelectric focusing (IEF) revealed the presence of an AmpC beta-lactamase with a pI >/= 9. amp C multiplex PCR, sequence, and Southern analyses indicated that only the Salmonella isolate had a plasmid-encoded AmpC beta-lactamase CMY-2 on a nonconjugative 60-MDa plasmid. PCR and sequence analysis of the E. coli ampC promoter identified mutations at positions -88(T), -82(G), -42(T), -18(A), -1(T) and +58(T) in all the isolates. In addition one strain had two extra-mutations at positions +23(A) and +49(G), and another strain had one extra-mutation at position +32(A). DNA fingerprinting revealed that all the E. coli isolates were different clones. It also showed that the U.K. Salmonella isolate was indistinguisable from a Canadian Salmonella isolate from turkeys; both had identical resistance phenotypes and produced CMY-2. This is the first report of a CMY-2 Salmonella isolate in the United Kingdom. These data imply that beta-lactam resistance in animal isolates can be generated de novo as evidenced by the E. coli strains, or in the case of the Salmonella strains be the result of intercontinental transmission due to an acquired resistance mechanism.

Multiple genetic typing of Salmonella Enteritidis phage-types 4, 6, 7, 8 and 13a isolates from animals and humans in the UK.

Salmonella enterica serovar Enteritidis is a common cause of salmonellosis in people in the UK. This study aimed to assess the degree of genetic diversity among animal and human isolates from UK, Wales and northern Ireland. A total of 250 isolates from humans (n = 59) and animals or their environment (n = 191), belonging to the most common phage-types, were fingerprinted by a combination of PFGE, PS ribotyping and plasmid profiling. The different techniques identified different degrees of polymorphism (PS ribotyping (52 types) > PFGE (22 types) > plasmid profiling (17 types)). A prevalent genomic clone, as well as a variety of less frequent clones are present for each of the phage-types. In most cases, the prevalent clones appeared within isolates from several animal species and from several geographical locations. The percentage of sporadic clones found in animal and human populations were very similar. There was not clear evidence of a higher degree of diversity for human or animal isolates. Some clones were found to be present in both human and animal.