Phage Type DT104 Research Articles

Comparative assessment of the disinfection effectiveness of thymol and benzalkonium chloride against adapted and non-adapted to thymol biofilm cells of a Salmonella Typhimurium epidemic phage type DT193 strain

Nowadays there is a need to develop cost-effective, safe, and preferably eco-friendly methods to combat the pathogenic and other detrimental robust biofilms. Ιn this work, the disinfection actions of thymol (THY), a phytocompound exhibiting wide antimicrobial action, and benzalkonium chloride (BAC), a synthetic biocide commonly used as surface disinfectant in the food industry and elsewhere, were comparatively evaluated against adapted and non-adapted to THY biofilm cells of a Salmonella enterica ser. Typhimurium epidemic phage type DT193 strain. Initially, the minimum inhibitory and bactericidal concentrations (MICs, MBCs) of each compound were determined against planktonic bacteria, together with their minimum biofilm inhibitory and eradication concentrations (MBICs, MBECs) against biofilms formed on polystyrene (PS). Bacteria were subsequently left to form biofilms on model stainless steel (SS) surfaces incubated in 1/10 diluted tryptone soy broth (dTSB) containing or not a sub-inhibitory THY concentration. Those sessile populations were finally submitted to disinfection (for 15 min) with THY or BAC and the viable biofilm bacteria were quantified by using in parallel agar plating and selective fluorescence staining. The results showed that when the terpenoid was applied at sub-MIC during biofilm formation, it was able to cause significant reductions of the final sessile populations on both surfaces (PS and SS). Disinfection results revealed the significant anti-biofilm action of THY on the non-adapted (control) biofilms (5 log reductions at MBC) and its superiority to that of BAC (<2 log reductions at 2 x MBC). However, the disinfection treatments applied on the THY-adapted biofilms were quite less efficient (achieving 2.6 and 1.3 log reductions, for THY and BAC, respectively). This demonstrates adaptation of Salmonella to THY, conferring co- and cross-disinfection resistance, as for many other antibacterial chemicals. Overall, the results demonstrate that natural compounds extracted from plants may be promising agents in helping to combat biofilms, multicellular microbial structures well-known for their remarkable hardiness against many stresses and antimicrobials.

Genomic Characterization of Salmonella typhimurium DT104 Strains Associated with Cattle and Beef Products

Salmonella enterica subsp. enterica serovar Typhimurium DT104, a multidrug-resistant phage type, has emerged globally as a major cause of foodborne outbreaks particularly associated with contaminated beef products. In this study, we sequenced three S. Typhimurium DT104 strains associated with a 2009 outbreak caused by ground beef, including the outbreak source strain and two clinical strains. The goal of the study was to gain a stronger understanding of the genomics and genomic epidemiology of highly clonal S. typhimurium DT104 strains associated with bovine sources. Our study found no single nucleotide polymorphisms (SNPs) between the ground beef source strain and the clinical isolates from the 2009 outbreak. SNP analysis including twelve other S. typhimurium strains from bovine and clinical sources, including both DT104 and non-DT104, determined DT104 strains averaged 55.0 SNPs between strains compared to 474.5 SNPs among non-DT104 strains. Phylogenetic analysis separated the DT104 strains from the non-DT104 strains, but strains did not cluster together based on source of isolation even within the DT104 phage type. Pangenome analysis of the strains confirmed previous studies showing that DT104 strains are missing the genes for the allantoin utilization pathway, but this study confirmed that the genes were part of a deletion event and not substituted or disrupted by the insertion of another genomic element. Additionally, cgMLST analysis revealed that DT104 strains with cattle as the source of isolation were quite diverse as a group and did not cluster together, even among strains from the same country. Expansion of the analysis to 775 S. typhimurium ST19 strains associated with cattle from North America revealed diversity between strains, not limited to just among DT104 strains, which suggests that the cattle environment is favorable for a diverse group of S. typhimurium strains and not just DT104 strains.

Phenotypic and Genotypic Eligible Methods for Salmonella Typhimurium Source Tracking.

Salmonellosis is one of the most common causes of foodborne infection and a leading cause of human gastroenteritis. Throughout the last decade, Salmonella enterica serotype Typhimurium (ST) has shown an increase report with the simultaneous emergence of multidrug-resistant isolates, as phage type DT104. Therefore, to successfully control this microorganism, it is important to attribute salmonellosis to the exact source. Studies of Salmonella source attribution have been performed to determine the main food/food-production animals involved, toward which, control efforts should be correctly directed. Hence, the election of a ST subtyping method depends on the particular problem that efforts must be directed, the resources and the data available. Generally, before choosing a molecular subtyping, phenotyping approaches such as serotyping, phage typing, and antimicrobial resistance profiling are implemented as a screening of an investigation, and the results are computed using frequency-matching models (i.e., Dutch, Hald and Asymmetric Island models). Actually, due to the advancement of molecular tools as PFGE, MLVA, MLST, CRISPR, and WGS more precise results have been obtained, but even with these technologies, there are still gaps to be elucidated. To address this issue, an important question needs to be answered: what are the currently suitable subtyping methods to source attribute ST. This review presents the most frequently applied subtyping methods used to characterize ST, analyses the major available microbial subtyping attribution models and ponders the use of conventional phenotyping methods, as well as, the most applied genotypic tools in the context of their potential applicability to investigates ST source tracking.

Horizontal Acquisition of a Multidrug-Resistance Module (R-type ASSuT) Is Responsible for the Monophasic Phenotype in a Widespread Clone of Salmonella Serovar 4,[5],12:i:.

Salmonella enterica serovar 4,[5],12:i:- is a monophasic variant of S. Typhimurium incapable of expressing the second-phase flagellar antigen (fljAB operon), and it is recognized to be one of the most prevalent serovars causing human infections. A clonal lineage characterized by phage type DT193, PulseNet PFGE profile STYMXB.0131 and multidrug resistance to ampicillin, streptomycin, sulphonamides and tetracycline (R-type ASSuT) is commonly circulating in Europe. In this study we determined the deletions affecting the fljAB operon and the resistance region responsible for the R-type ASSuT in a strain of Salmonella enterica serovar 4,5,12:i:- DT193/STYMXB.0131, through an approach based on PCRs and Southern blot hybridization of genomic DNA. Using a set of nine specific PCRs, the prevalence of the resistance region was assessed in a collection of 144 S. enterica serovar 4,[5],12:i:-/ASSuT/STYMXB.0131 strains isolated from Germany, Switzerland and Italy. A 28 kb-region is embedded between the loci STM2759 and iroB, replacing the DNA located in between, including the fljAB operon. It encompasses the genes blaTEM−1, strA-strB, sul2 and tet(B) responsible for the R-type ASSuT together with genes involved in plasmid replication and orfs of unknown function characteristically located on IncH1 plasmids. Its location and internal structure is fairly conserved in S. enterica serovar 4,[5],12:i:-/ASSuT/STYMXB.0131 strains regardless of the isolation source or country. Hence, in the S. enterica serovar 4,[5],12:i:-/ASSuT/STYMXB.0131 clonal lineage widespread in Germany, Switzerland and Italy, a resistance region derived from IncH1 plasmids has replaced the chromosomal region encoding the second flagellar phase and is an example of the stabilization of new plasmid-derived genetic material due to integration into the bacterial chromosome.

Prevalence and Antibiotic Resistance of Salmonella SPP. and Salmonella Typhimurium in Broiler Carcasses Wings and Liver

AbstractThe objectives of this study were to isolate and identify Salmonella spp. from broiler carcasses, wings and liver samples by immunomagnetic separation based cultivation technique, to verify the isolates as Salmonella spp. by the detection of oriC gene by PCR, to identify the isolates using malic acid dehydrogenase and DT104 specific primers as S. Typhimurium and S. Typhimurium DT104. Also to determine the two important virulence genes, virulence plasmid (spvC) and invasion (invA) for molecular characterization, to evaluate the antibiotic resistance profiles of the isolates. For this purpose, 110 broiler carcasses, 110 broiler wings and 110 broiler liver samples with a total number of 330 were analyzed. Ninety six (29.1%) of the samples were detected as contaminated with Salmonella spp. According to the results 11 isolates (11.4%) were identified as S. Typhimurium. None of these serotypes were determined as specific phage type DT104. InvA gene was detected from all the (100.0%) Salmonella isolates and 14 isolates (14.6%) were detected as positive for spvC gene. Eighty‐three isolates (86.4%) were resistant to at least 5, 70 isolates (72.9 %) resistant to at least 7 and 36 isolates (37.5%) were resistant to at least 9 antibiotic.Practical ApplicationThis work is significant because Salmonella is still an important public health problem all around the world. This study would provide some data about the incidence of S. Typhimurium and S. Typhimurium DT104 in chicken meat and parts and the antibiotic resistance of the isolates in Turkey. Besides, the method used in study and the parts chosen for analysis would be a model for the other researchers who are thinking to study in this area.

Molecular characterization of Salmonella enterica serovar Typhimurium strains isolated from humans in Turkey

Multidrug resistant (MDR) Salmonella infections, especially infections due to Salmonella Typhimurium DT104 phage type strains are an important public health issue in many parts of the world. S.Typhimurium is the most common serotype isolated from clinical samples in Turkey but we have limited data about the phage types of these isolates. The aims of this study were to find out whether these MDR S.Typhimurium isolates are DT104 phage type isolates and have class 1 integrons and to investigate the relationships of these characteristics between plasmid and pulsed field gel electrophoresis (PFGE) profiles. A total of 66 S.Typhimurium stock strains selected from Enterobacteria Laboratory culture collections of Ankara University School of Medicine, Department of Medical Microbiology were investigated by plasmid profile analysis (PPA) and PFGE with the use of XbaI and SpeI enzymes. The presence of class 1 integrons and the phage type 104 were investigated by polymerase chain reaction (PCR). The strains used in the study were sporadically isolated cases from seven provinces after year 2000 with ACSSuT (63), ACGSSuTT/S (1), ACSSuTT/S (1) and ASSuTT/S (1) resistance types [ampicillin (A), chloramphenicol (C), gentamicin (G), streptomycin (S), sulphonamide (Su), tetracycline (T), trimethoprim/sulfamethoxazole (T/S)]. Of the isolates 65 were found as DT104 phage type. Forty-three S.Typhimurium DT104 isolates that carry class 1 integrons had five different bands between 350-1600 base pairs (bp); all of the isolates harbored 1-4 plasmids with sizes ranging from 1.0-180 kbp and 62 isolates had 90 kbp plasmid which was serotype specific and virulence related. S.Typhimurium DT104 isolates were grouped into five (X1-X5) and seven (S1-S7) profiles with XbaI and SpeI enzymes, respectively. When the profiles of the two enzymes were evaluated, 58 of the 65 (89.2%) isolates showed similar (X1.S1) profile. The molecular characteristics of the most S.Typhimurium isolates were clustered in similar groups when class 1 integron, plasmid and PFGE types were analyzed together. In this study we showed that nearly all S.Typhimurium isolates with five drug resistance pattern (ACSSuT) were DT104 isolates. PFGE profiles of these sporadic isolates suggested that they were epidemiologically related.

Characterization of Salmonella enterica Serovar 4,[5],12:i:- Isolates from Korean Food Animals.

Salmonella enterica subspecies enterica serovar 4,[5],12:i:-, a monophasic variant of Salmonella Typhimurium, has emerged as one of the most common serotypes related to human salmonellosis. In this study, the 22 isolates of S. 4,[5],12:i:- from food animals were identified by a specific multiplex polymerase chain reaction between 2009 and 2012. The isolation rate of S. 4,[5],12:i:- accounted for 1.7% (22/1271) of Salmonella spp. isolates from food animal origins: more specifically, 7.6% (18/235) from pigs and 0.6% (4/686) from chickens. The predominant S. 4,[5],12:i:- isolates in Korea belonged to phage type DT193 (12/22) with ampicillin-streptomycin-sulfonamide-tetracycline (ASSuT) resistance pattern (9/22). The XbaI-pulsed-field gel electrophoresis (PFGE) analysis revealed 11 different pulsotypes, and the major X-1 pattern was shared by 8 isolates. The isolates belonging to pattern X-1 were further subdivided into three BlnI-PFGE patterns and four variable-number tandem-repeat analysis (MLVA) allele combinations. The combining of MLVA and PFGE data could be valuable in characterizing highly clonal strains and discriminating their epidemiological relationship.

Outbreak of uncommon O4 non-agglutinating Salmonella typhimurium linked to minced pork, Saxony-Anhalt, Germany, January to April 2013.

IntroductionIn January 2013, the National Reference Centre for Salmonella (NRC) detected a salmonellosis cluster in Saxony-Anhalt, Germany, caused by uncommon O4 non-agglutinating, monophasic Salmonella (S.) Typhimurium DT193. Circulating predominant monophasic S. Typhimurium DT193 clones typically display resistance phenotype ASSuT. We investigated common exposures to control the outbreak, and conducted microbiological investigations to assess the strains’ phenotype.MethodsWe conducted a case-control study defining cases as persons living or working in Saxony-Anhalt diagnosed with the O4 non-agglutinating strain between January and March 2013. We selected two controls contemporarily reported with norovirus infection, frequency-matched on residence and age group, per case. We interviewed regarding food consumption, especially pork and its place of purchase. We calculated odds ratios (ORs) with 95% confidence intervals (95% CI) using logistic regression. The NRC investigated human and food isolates by PCR, SDS-PAGE, MLST, PFGE, MLVA and susceptibility testing.ResultsAltogether, 68 O4 non-agglutinating human isolates were confirmed between January and April 2013. Of those, 61 were assigned to the outbreak (median age 57 years, 44% female); 83% cases ≥ 60 years were hospitalized. Eating raw minced pork from butcheries within 3 days was associated with disease (31 cases, 28 controls; OR adjusted for sex: 3.6; 95% CI: 1.0-13). Phage type DT193 and MLST ST34 were assigned, and isolates’ lipopolysaccharide (LPS) matched control strains. Isolates linked to Saxony-Anhalt exhibited PFGE type 5. ASSuT- and ACSSuT phenotype proportions were 34 and 39% respectively; 54% were resistant to chloramphenicol. Three pork isolates matched the outbreak strain.DiscussionRaw minced pork was the most likely infection vehicle in this first reported outbreak caused by O4 non-agglutinating, mostly chloramphenicol-resistant S. Typhimurium DT193. High hospitalization proportions demand awareness on the risk of consumption of raw pork among elderly. LPS analysis indicated O4 expression; therefore, testing with antisera from different lots is recommendable in unexpected agglutination reactions.

Fluoroquinolone induction of phage-mediated gene transfer in multidrug-resistant Salmonella

Fluoroquinolones are broad-spectrum antibiotics that inhibit bacterial DNA gyrase and topoisomerase activity, which can cause DNA damage and result in bacterial cell death. In response to DNA damage, bacteria induce an SOS response to stimulate DNA repair. However, the SOS response may also induce prophage with production of infectious virions. Salmonella strains typically contain multiple prophages, and certain strains including phage types DT120 and DT104 contain prophage that upon induction are capable of generalised transduction. In this study, strains of multidrug-resistant (MDR) Salmonella enterica serovar Typhimurium DT120 and DT104 were exposed to fluoroquinolones important for use in human and veterinary disease therapy to determine whether prophage(s) are induced that could facilitate phage-mediated gene transfer. Cultures of MDR S. Typhimurium DT120 and DT104 containing a kanamycin resistance plasmid were lysed after exposure to fluoroquinolones (ciprofloxacin, enrofloxacin and danofloxacin). Bacterial cell lysates were able to transfer the plasmid to a recipient kanamycin-susceptible Salmonella strain by generalised transduction. In addition, exposure of DT120 to ciprofloxacin induced the recA gene of the bacterial SOS response and genes encoded in a P22-like generalised transducing prophage. This research indicates that fluoroquinolone exposure of MDR Salmonella can facilitate horizontal gene transfer, suggesting that fluoroquinolone usage in human and veterinary medicine may have unintended consequences, including the induction of phage-mediated gene transfer from MDR Salmonella. Stimulation of gene transfer following bacterial exposure to fluoroquinolones should be considered an adverse effect, and clinical decisions regarding antibiotic selection for infectious disease therapy should include this potential risk.

Monophasic expression of FliC by Salmonella 4,[5],12:i:- DT193 does not alter its pathogenicity during infection of porcine intestinal epithelial cells.

Non-typhoidal serotypes of Salmonella enterica remain important food-borne pathogens worldwide and the frequent emergence of epidemic strains in food-producing animals is a risk to public health. In recent years, Salmonella 4,[5],12:i:- isolates, expressing only phase 1 (FliC) of the two flagellar antigens, have emerged and increased in prevalence worldwide. In Europe, the majority of 4,[5],12:i:- isolates belong to phage types DT193 and DT120 of Salmonella Typhimurium and pigs have been identified as the reservoir species. In this study we investigated the ability of pig-derived monophasic (4,[5],12:i:-) and biphasic DT193 isolates to invade a porcine intestinal epithelial cell line (IPEC-1) and activate TLR-5, IL-8 and caspases. We found that the 4,[5],12:i:- isolates exhibited comparable adhesion and invasion to that of the virulent S. Typhimurium isolate 4/74, suggesting that these strains could be capable of colonizing the small intestine of pigs in vivo. Infection with 4,[5],12:i:- and biphasic DT193 isolates resulted in approximately the same level of TLR-5 (a flagellin receptor) and IL-8 (a proinflammatory chemokine) mRNA upregulation. The monophasic variants also elicited similar levels of caspase activation and cytotoxicity to the phase-variable DT193 isolates. These findings suggest that failure of 4,[5],12:i:- DT193 isolates to express a second phase of flagellar antigen (FljB) is unlikely to hamper their pathogenicity during colonization of the porcine intestinal tract.

Clonal distribution of monophasic Salmonella enterica subsp. enterica serotype 4,[5],12:i:- in the Czech Republic.

Abstract Salmonella 4,[5],12:i:- has become the third most common serotype in Europe, including the Czech Republic. In this study, phenotypic and genotypic methods for a more detailed description of this serotype were used. Analysis of a limited number of isolates revealed that 76% of them belonged to phage type DT193. Also, rare phage types DT208 and U311 were identified. In total, 88.6% of the isolates were resistant to at least four antimicrobial agents. In this study, 24 multilocus variable-number tandem-repeat analysis profiles were detected, and some of them matched with the profiles recently described in Europe.

Characterization of the EmergingSalmonella4,[5],12:i:- in Danish Animal Production

The monophasic Salmonella variant with the antigenic formula Salmonella 4,[5],12:i:- has emerged in the last decade as one of the main serotypes related to human salmonellosis. In the present study, a collection of 94 isolates of the S. 4,12:i:- and S. 4,5,12:i:- coming from Danish farm animals, swine (86), cattle (7), and poultry (1), with well-defined identification was further typed by polymerase chain reaction serotyping, phage typing, and molecular typing (polymerase chain reaction and multilocus variable-number tandem-repeat analysis [MLVA]). Moreover, the determination of antimicrobial resistance pattern of each isolate was tested. In 68 of the isolates the fljB gene was absent (i.e., they were true monophasic strains), whereas in 26 isolates, the gene was present despite the fact that the isolates did not express it. The results clustered the isolates in three main pulse-types. The predominant cluster was compatible with the previously described pattern STYMXB.0131. All the isolates included in this cluster lacked the fljB gene, and all the isolates except one belonged to phage type DT 193 with the AMP-STR-SMX-TET resistance pattern. MLVA analysis divided the clusters in several MLVA profiles previously reported by other studies. Finally, antimicrobial resistance and multiresistance was frequent, although no resistance was detected in critical compounds: fluoroquinolones and cephalosporins. The present study demonstrates the presence of monophasic Salmonella Typhimurium-like strains in Danish food animal production with well-characterized clones that are described by previous studies, demonstrating the emergence and spread of this serotype in Denmark.

The agricultural antibiotic carbadox induces phage-mediated gene transfer in Salmonella

Antibiotics are used for disease therapeutic or preventative effects in humans and animals, as well as for enhanced feed conversion efficiency in livestock. Antibiotics can also cause undesirable effects in microbial populations, including selection for antibiotic resistance, enhanced pathogen invasion, and stimulation of horizontal gene transfer. Carbadox is a veterinary antibiotic used in the US during the starter phase of swine production for improved feed efficiency and control of swine dysentery and bacterial swine enteritis. Carbadox has been shown in vitro to induce phage-encoded Shiga toxin in Shiga toxin-producing Escherichia coli (STEC) and a phage-like element transferring antibiotic resistance genes in Brachyspira hyodysenteriae, but the effect of carbadox on prophages in other bacteria is unknown. This study examined carbadox exposure on prophage induction and genetic transfer in Salmonella enterica serovar Typhimurium, a human foodborne pathogen that frequently colonizes swine without causing disease. S. Typhimurium LT2 exposed to carbadox induced prophage production, resulting in bacterial cell lysis and release of virions that were visible by electron microscopy. Carbadox induction of phage-mediated gene transfer was confirmed by monitoring the transduction of a sodCIII::neo cassette in the Fels-1 prophage from LT2 to a recipient Salmonella strain. Furthermore, carbadox frequently induced generalized transducing phages in multidrug-resistant phage type DT104 and DT120 isolates, resulting in the transfer of chromosomal and plasmid DNA that included antibiotic resistance genes. Our research indicates that exposure of Salmonella to carbadox induces prophages that can transfer virulence and antibiotic resistance genes to susceptible bacterial hosts. Carbadox-induced, phage-mediated gene transfer could serve as a contributing factor in bacterial evolution during animal production, with prophages being a reservoir for bacterial fitness genes in the environment.

MLVA as a tool for public health surveillance of human Salmonella Typhimurium: prospective study in Belgium and evaluation of MLVA loci stability.

Surveillance of Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium) is generally considered to benefit from molecular techniques like multiple-locus variable-number of tandem repeats analysis (MLVA), which allow earlier detection and confinement of outbreaks. Here, a surveillance study, including phage typing, antimicrobial susceptibility testing and the in Europe most commonly used 5-loci MLVA on 1,420 S. Typhimurium isolates collected between 2010 and 2012 in Belgium, was used to evaluate the added value of MLVA for public health surveillance. Phage types DT193, DT195, DT120, DT104, DT12 and U302 dominate the Belgian S. Typhimurium population. A combined resistance to ampicillin, streptomycin, sulphonamides and tetracycline (ASSuT) with or without additional resistances was observed for 42.5% of the isolates. 414 different MLVA profiles were detected, of which 14 frequent profiles included 44.4% of the S. Typhimurium population. During a serial passage experiment on selected isolates to investigate the in vitro stability of the 5 MLVA loci, variations over time were observed for loci STTR6, STTR10, STTR5 and STTR9. This study demonstrates that MLVA improves public health surveillance of S. Typhimurium. However, the 5-loci MLVA should be complemented with other subtyping methods for investigation of possible outbreaks with frequent MLVA profiles. Also, variability in these MLVA loci should be taken into account when investigating extended outbreaks and studying dynamics over longer periods.

Identification of Virulence Properties in Salmonella Typhimurium DT104 Using Caenorhabditis elegans

Salmonella enterica serover Typhimurium definitive phage type DT104, resistant to multiple antibiotics, is one of the most widespread Salmonella species in human infection worldwide. Although several cohort studies indicate that DT104 carrying the multidrug resistance (MDR) locus on salmonella genomic island 1 is a possible hyper-virulent strain compared to DT104 strains without MDR, or other Salmonella enterica serotypes, existing experimental evidence regarding virulence properties associated with the MDR region is controversial. To address this question, we constructed an isogenic MDR deletion (∆MDR) mutant strain of DT104, SNS12, by allelic exchange and used Caenorhabditis elegans as a host model to assess differences in virulence between these two strains. SNS12 exhibited decreased virulence in C. elegans, and we observed increased colonization and proliferation of the intestine of C. elegans by DT104. The immune response against MDR-carrying DT104 appears to function through a non-canonical Unfolded Protein Response (UPR) pathway, namely prion-like-(QN-rich)-domain-bearing protein pathway (PQN), in a ced-1 dependent manner in C. elegans. Further, we also demonstrate that genes of the PQN pathway and antimicrobial peptide gene abf-2, are expressed at higher transcriptional levels in worms immediately following exposure to DT104, in comparison with worms exposed to SNS12. Altogether, our results suggest that the MDR region of Salmonella Typhimurium DT104 has a direct role in virulence against Caenorhabditis elegans.

Characterization ofSalmonella entericaSubsp.entericaSerovar 4,[5],12:i:- Clones Isolated from Human and Other Sources in Switzerland Between 2007 and 2011

Salmonella enterica subsp. enterica serovar 4,[5],12:i:- is a monophasic variant of Salmonella Typhimurium. In this study, a total of 651 human and 107 food and environmental isolates of serovar 4,[5],12:i:- recovered from 2007 through 2011 in Switzerland were characterized by antibiotic resistance profiles and pulsed-field gel electrophoresis (PFGE). In addition, a selection of isolates belonging to the most frequent PFGE patterns was further subjected to multilocus variable-number tandem-repeat analysis (MLVA) and phage typing. Over the years 2007-2011, the reports of salmonellosis caused by Salmonella enterica serovar 4,[5],12:i:- significantly increased. A high prevalence of multidrug-resistant isolates, mainly showing an ampicillin-streptomycin-sulfonamide-tetracycline resistance pattern (ASSuT), was observed. In addition, four extended spectrum beta lactamase (ESBL) (CTX-M-55)-producing isolates were found. XbaI PFGE analysis of all isolates revealed over 150 different pulsotypes, and generally showed a considerable diversity within the monophasic isolates. Nevertheless, among these we identified seven dominant profiles, which encompassed 66% of all isolates tested. The PFGE type STYMXB.0131 dominated among human as well as food isolates. Multilocus variable-number tandem-repeat analysis profile 3-12-10-0-0211, which, in many cases, coincided with PFGE type STYMXB.0131 and phage type DT193 were the most prevalent types found for the isolates further characterized by these typing methods. Our data provide strong evidence for a spread of two specific Salmonella serovar 4,[5],12:i:- clones (PFGE pattern STYMXB.0131, resistance type ASSuT) and (PFGE pattern STYMXB.0131, resistance type SSuT). In contrast to the human isolates, the pork/poultry isolates expressed predominantly the SSuT resistance type.

A retrospective analysis of Salmonella serovars isolated from pigs in Great Britain between 1994 and 2010

A retrospective study analysing Salmonella serovars and antimicrobial resistance data from pigs in Great Britain between 1994 and 2010 was performed. Data were obtained through scanning surveillance and compared with prevalence data from other livestock species as well as human data. During the study period, two serovars, S. Typhimurium and S. Derby, predominated in British pigs. The total number of Salmonella incidents has decreased steadily over the study period, from 360 incidents per year in 1994 to 172 incidents in 2010. S. Typhimurium has been the most common serovar every year, but the relative percentage went down over the past few years. During the same time period, monophasic strains of S. Typhimurium have increased in numbers and were accounting for as much as 25% of incidents in 2010, representing the second most common serovar in British pigs in 2010. Antimicrobial resistance data from S. Typhimurium isolates show that the percentage of isolates which are resistant to six or more antimicrobials has increased from 27.2% in 1994 to 58.3% in 2010 and that the percentage of isolates fully sensitive to the panel of antimicrobials tested was only 3.3% in 2010. S. Typhimurium isolates belonged mainly to phagetypes DT193 and U288 in 2010, and an increase can be seen in the number of isolates belonging to phage type DT193. DT104, which was the predominant phagetype during the 1990s, has gone down considerably and represented less than 5% of all S. Typhimurium isolates in 2010. Monophasic strains of S. Typhimurium belonged mainly to phagetype 193 with less than 20% belonging to phagetype 120.The overall trend shows that the number of Salmonella incidents reported from British pigs has gone down considerably over the 17-year study period, but that the relative percentage of monophasic strains of S. Typhimurium has increased significantly. This trend seems to be in line with observations from other European countries, where an increase of this serovar can be seen both in livestock and in human patients. The increasing percentage of Salmonella-isolates which show multi-resistance is a matter of concern and has to be monitored carefully in order to assess any potential risks this may pose to human patients.

Antimicrobial Resistance of Human &lt;i&gt;Salmonella enterica&lt;/i&gt; Serovar Typhimurium U302 Strains: Prevalence of R-Type ASSuT in Slovakia, 2006&amp;ndash;2011

Salmonella enterica serovar Typhimurium is a common cause of non-typhoid salmonellosis in humans. Since 2006, an increase in the human infections caused by U302 phage type in Slovakia has been documented and, from 2006 to 2011, a total of 291 U302 human strains were isolated. Antimicrobial susceptibility testing demonstrated that these strains had a high overall antimicrobial resistance and 244 (83.8%) of the tested strains were multidrug-resistant (MDR). The most prevalent resistance was to ampicillin, streptomycin, sulfisoxazole, and tetracycline (R-type ASSuT), which was verified in 87 (29.9%) strains. The annual rate of this resistance type varies, but the largest number of these strains were identified in 2009 and 2010. The classical pentaresistance phenotype (R-type ACSSuT), characteristic of the DT104 phage type, was found only in 40 (13.7%) U302 strains. These results suggested that although the prevalence of DT104 phage type has decreased, ASSuT as well as ACSSuT resistance markers continue to circulate. Therefore, continual surveillance of the occurrence of these and similar MDR phage types is necessary.

Prevalence and characterization of Salmonella enterica from the feces of cattle, poultry, swine and hedgehogs in Burkina Faso and their comparison to human Salmonella isolates

BackgroundProduction and wild animals are major sources of human salmonellosis and animals raised for food also play an important role in transmission of antimicrobial resistant Salmonella strains to humans. Furthermore, in sub-Saharan Africa non-typhoidal Salmonella serotypes are common bloodstream isolates in febrile patients. Yet, little is known about the environmental reservoirs and predominant modes of transmission of these pathogens. The purpose of this study was to discover potential sources and distribution vehicles of Salmonella by isolating strains from apparently healthy slaughtered food animals and wild hedgehogs and by determining the genetic relatedness between the strains and human isolates. For this purpose, 729 feces samples from apparently healthy slaughtered cattle (n = 304), poultry (n = 350), swine (n = 50) and hedgehogs (n = 25) were examined for the presence of Salmonella enterica in Burkina Faso. The isolates were characterized by serotyping, antimicrobial-susceptibility testing, phage typing, and pulsed-field gel electrophoresis (PFGE) with XbaI and BlnI restriction enzymes.ResultsOf the 729 feces samples, 383 (53%) contained Salmonella, representing a total of 81 different serotypes. Salmonella was present in 52% of the cattle, 55% of the poultry, 16% of the swine and 96% of the hedgehog feces samples. Antimicrobial resistance was detected in 14% of the isolates. S. Typhimurium isolates from poultry and humans (obtained from a previous study) were multiresistant to the same antimicrobials (ampicillin, chloramphenicol, streptomycin, sulfonamides and trimethoprim), had the same phage type DT 56 and were closely related in PFGE. S. Muenster isolates from hedgehogs had similar PFGE patterns as the domestic animals.ConclusionsBased on our results it seems that production and wild animals can share the same Salmonella serotypes and potentially transmit some of them to humans. As the humans and animals often live in close vicinity in Africa and the hygiene control of the meat retail chain is defective, high Salmonella carriage rates of the animals can pose a major public health risk in Burkina Faso. This underlines the necessity for a joint and coordinated surveillance and monitoring programs for salmonellosis in Africa.

Phenotypic and genetic traits of Salmonella enterica subsp. serovar Typhimurium strains causing salmonellosis foci in rabbit farms from Southern Italy in 1999–2003

In this study, we characterised the Salmonella Typhimurium strains responsible for four outbreaks which occurred in distinct rabbit farms (Southern Italy) from 1999 to 2003. Strains were typed by Pulsed Field Gel Electrophoresis (PFGE) and the genetic basis of antimicrobial resistance was established. A major group of clonally related isolates, pulsotype STYMXB.0061, accounted for three of the salmonellosis foci. Strains were resistant to streptomycin, chloramphenicol, tetracycline, ampicillin and sulphonamides encoded respectively by the aadA2, floR, tetG, blaPSE-1, sul1 gene cluster harboured by a Salmonella Genomic Island 1. The clonally related group of isolates included strains phage type DT104, DT12 or undefined type (NT). The fourth salmonellosis focus was caused by a strain pulsotype STYMXB.0147, resistant to sulphonamides (encoded by sul2) and phage type U302. Results provided first molecular characterisation of S. Typhimurium strains isolated from rabbit farms in Italy and highlighted the presence of the pulsotype STYMXB.0061 even before its wide detection among human clinical isolates collected in Italy in the mid 2000s from clinical cases.