Phage types, plasmid profiles and chromosomal restriction profiles of Salmonella enterica subsp. enterica ser. enteritidis (S. enteritidis) isolated in Poland in 1999-2000]

Salmonella Enteritidis strains are the most often isolated Salmonella serovars in Poland. In the present study, phage typing, plasmid profile analysis, and PFGE have been applied to characterize 140 Polish S. Enteritidis isolates originated from human cases of salmonellosis and from other sources. The typing phages of Ward and colleagues scheme were used to type a total of 140 S. Enteritidis strains coming from Poland. All 140 strains were typable and six different phage types were observed. A total of 125 (89%) of 140 isolates examined belonged to PT 4. The others PTs were represented by small amount of strains (PT1-2, PT6-6, PT7-1, PT8-4 and PT21-2 strains). Among all tested isolates six different plasmid profiles were observed. Of the 140 examined strains, 128 (91.4%) contained the 57 kb plasmid alone. After XbaI digestion four distinct pulse field chromosomal restriction profiles among studied S. Enteritidis were observed. XbaI and SpeI chromosomal restriction profiles of S. Enteritidis PT4 were identical with reference strain profiles. Our findings confirmed earlier suggestions that the increase of human salmonellosis cases in Poland was caused by S. Enteritidis PT4 and was due to consumption of contaminated food. This study confirmed the importance of using PFGE in combination with phage typing, plasmid typing and antibiotic resistance testing for studying the epidemiology of S. Enteritidis.     

Pulsed-field gel electrophoresis, plasmid profiles and phage types for the human isolates of Salmonella enterica serovar Enteritidis obtained over 13 years in Taiwan

AIMS: Plasmid profile, phage typing, and pulsed-field gel electrophoresis (PFGE) patterns of 124 Salmonella Enteritidis strains isolated in 1998-2002 in Taiwan were analysed and the results were compared with those of the 63 strains obtained in 1991-1997, so that molecular subtypes and epidemic strains for Salmonella Enteritidis over a 13-year period (1991-2002) could be elucidated. METHODS AND RESULTS: A total of 124 strains of Salmonella Enteritidis isolated from human in Taiwan between 1998 and 2002 were analysed by PFGE, plasmid analysis and phage typing. The results obtained were compared with those of the 63 strains obtained in 1991-1997, so that the clonal relationships for a total of 187 strains obtained over 13 years could be elucidated. For PFGE, restriction enzymes XbaI, SpeI and NotI were used for chromosomal DNA digestion. Results showed 28 PFGE pattern combinations for the 187 Salmonella strains. Of them, pattern X3S3N3 was the major subtype as 130 strains isolated from different locations during 1991-2002 showed this PFGE pattern. For all these 187 strains, the genetic similarity was higher than 80%. Plasmid analysis showed 17 distinct types, which consist of one to four plasmids and the predominant phage type of those strains was PT4 (71.6%) and PT6a (13.4%). The three methods identified different degrees of polymorphism in the following order: plasmid profile (18 types, D = 0.659) > PFGE (28 types, D = 0.512) > phage typing (13 types, D = 0.438). As PFGE patterns, phage type and plasmid profile were combined for subtyping, the 187 strains could be grouped into 46 subtypes and the discriminatory index was raised to 0.795. For these 46 subtypes, the predominant one was X3S3N3/P1/PT4, which contained 77 (41%) isolates. CONCLUSIONS: Most of the Salmonella Enteritidis strains from sporadic cases were with pattern X3S3N3. They were the prevalent and may be the epidemic strains found in Taiwan during 1991-2002. The present study suggested that the several variants were derived from a single clonal line and the genome for strains of Salmonella Enteritidis are highly conserved over a 13-year period (1991-2002). SIGNIFICANCE AND IMPACT OF THE STUDY: The results obtained here are useful for epidemiolgical study of salmonellosis caused by Salmonella Enteritidis in Taiwan. Comparing the data of the present study with those obtained for strains from other countries, the major subtypes for Salmonella Enteritidis infection in the world can be elucidated.     

Functional and molecular characterization of pSE34 encoding a type IV secretion system in Salmonella enterica serotype Enteritidis phage type 34

Salmonella enterica serotype Enteritidis infection remains a serious public health threat to humans. Salmonella Enteritidis phage type 4 (PT4) is a clone that has already caused a global pandemic for years. To investigate why PT34 becomes a subdominantly emerging phage type, molecular characterizations, including serotyping, pulsed-field gel electrophoresis (PFGE), phage typing, and plasmid profiling, were carried out on PT34. The results indicated that relative to PT4, PT34 contained an additional 32-kb DNA segment in PFGE and a 33-kb plasmid pSE34 in plasmid profiling. Southern blot hybridization showed that the DNA segment was the major part of pSE34. All of the S . Enteritidis PT34 clinical isolates possessed pSE34, while PT4 and PT21 did not. Sequencing analysis revealed that pSE34 is 32 950 bp long, with a G+C% content of 41.2%, and contains a total of 53 orf s. Transposon mutagenesis demonstrated that taxB, taxC , and the pilX operon on this plasmid participated in the process of conjugation. In virulence testing, PT34 that harbored pSE34, compared with PT4, showed no increased invasion to tissue culture cells in vitro . The presence of conjugative pSE34 in PT4 caused the conversion of phage type from PT4 to PT34, suggesting that the emergence of PT34 was a result of the introduction of the conjugative pSE34 into its common progenitor PT4.     

Plasmid pC present in Salmonella enterica serovar Enteritidis PT14b strains encodes a restriction modification system

Salmonella enterica serovar Enteritidis (S. Enteritidis) possesses plasmids of different sizes and roles. Besides the serovar-specific virulence plasmid present in most field strains, S. Enteritidis can harbour plasmids of low molecular mass whose biological role is poorly understood. We therefore sequenced plasmid pC present in S. Enteritidis strains belonging to phage type PT14b. The size of plasmid was determined to be 5,269 bp and it was predicted to encode four open reading frames (ORFs). The first two ORFs were found (initial 3,230 bp) to be highly homologous to rom and mbeA genes of ColE1 plasmid of Escherichia coli. Proteins encoded by the other two ORFs were 99% homologous to a restriction methylase and restriction endonuclease encoded by plasmid pECO29 of a field strain of E. coli. Using insertional mutagenesis we confirmed experimentally that the plasmid pC-encoded restriction modification system was functional and could explain the high resistance of S. Enteritidis PT14b strains to phage infection.     

Differences in gene content between Salmonella enterica serovar Enteritidis isolates and comparison to closely related serovars Gallinarum and Dublin

Salmonella enterica serovar Enteritidis is often transmitted into the human food supply through eggs of hens that appear healthy. This pathogen became far more prevalent in poultry following eradication of the fowl pathogen S. enterica serovar Gallinarum in the mid-20th century. To investigate whether changes in serovar Enteritidis gene content contributed to this increased prevalence, and to evaluate genetic heterogeneity within the serovar, comparative genomic hybridization was performed on eight 60-year-old and nineteen 10- to 20-year-old serovar Enteritidis strains from various hosts, using a Salmonella-specific microarray. Overall, almost all the serovar Enteritidis genomes were very similar to each other. Excluding two rare strains classified as serovar Enteritidis in the Salmonella reference collection B, only eleven regions of the serovar Enteritidis phage type 4 (PT4) chromosome (sequenced at the Sanger Center) were absent or divergent in any of the other serovar Enteritidis strains tested. The more recent isolates did not have consistent differences from 60-year-old field isolates, suggesting that no large genomic additions on a whole-gene scale were needed for serovar Enteritidis to become more prevalent in domestic fowl. Cross-hybridization of phage genes on the array with related genes in the examined genomes grouped the serovar Enteritidis isolates into two major lineages. Microarray comparisons of the sequenced serovar Enteritidis PT4 to isolates of the closely related serovars Dublin and Gallinarum (biovars Gallinarum and Pullorum) revealed several genomic areas that distinguished them from serovar Enteritidis and from each other. These differences in gene content could be useful in DNA-based typing and in understanding the different phenotypes of these related serovars.     

The presence of major world-wide clones for phage type 4 and 8 Salmonella enterica serovar Enteritidis and the evaluation of their virulence levels by invasiveness assays in vitro and in vivo

Seventy-seven animal isolates of Salmonella enterica serovar Enteritidis (S. Enteritidis) obtained from the United States were analyzed by phage typing and pulsed field gel electrophoresis (PFGE). Thirty-nine strains were found with phage types (PT) 4, 8, and 13a. When the chromosomal DNA of these 39 isolated strains with PT4, 8, and 13a were digested with XbaI, SpeI and NotI, followed by PFGE analysis, 28 strains were found with a pattern combination of X4S4N4, which was the major subtype. When PFGE patterns of the US isolates with PT 4 and 8 were compared with those of the Taiwanese and German isolates, pattern X3S3N3 was confirmed to be the world-wide subtype shared by PT 4 isolates, as previously reported, while pattern X4S4N4 was newly found to be the most common subtype shared by PT 8 strains. The presence of such major world-wide clones, however, does not necessarily mean that these clones are highly virulent, at least not according to the results of invasiveness assays using cultured human intestinal epithelium cell line Int-407 and living BALB/mice.     

Use of WARD et al's scheme for bacteriophage typing of Salmonella enteritidis strains isolated in Poland

The typing phages set of Ward et al. was used to type a total of 517 strains of Salmonella Enteritidis isolated in Poland in 1986-1995. According to the Ward et al. scheme, 56.5% of the strains tested were assigned to 14 different phage types. Phage types 8, 4, 1 and 4a were placed first, second, third and fourth, respectively. They were dominated both in the outbreak isolates and in the isolates from the other sources. Ten phage types were represented by single strains. Other strains reacted with phages without showing any of the designated phage type (37.1%) or were untypable (6.4%). The Ward et al. scheme seems to demonstrate not enough high degree of strain discrimination for Salmonella Enteritidis isolates in Poland. It seems that the Ward et al. scheme is not enough useful for the epidemiological investigations of Salmonella Enteritidis in Poland.     

Correlation of phenotype with the genotype of egg-contaminating Salmonella enterica serovar Enteritidis

The genotype of Salmonella enterica serovar Enteritidis was correlated with the phenotype using DNA-DNA microarray hybridization, ribotyping, and Phenotype MicroArray analysis to compare three strains that differed in colony morphology and phage type. No DNA hybridization differences were found between two phage type 13A (PT13A) strains that varied in biofilm formation; however, the ribotype patterns were different. Both PT13A strains had DNA sequences similar to that of bacteriophage Fels2, whereas the PT4 genome to which they were compared, as well as a PT4 field isolate, had a DNA sequence with some similarity to the bacteriophage ST64b sequence. Phenotype MicroArray analysis indicated that the two PT13A strains and the PT4 field isolate had similar respiratory activity profiles at 37 degrees C. However, the wild-type S. enterica serovar Enteritidis PT13A strain grew significantly better in 20% more of the 1,920 conditions tested when it was assayed at 25 degrees C than the biofilm-forming PT13A strain grew. Statistical analysis of the respiratory activity suggested that S. enterica serovar Enteritidis PT4 had a temperature-influenced dimorphic metabolism which at 25 degrees C somewhat resembled the profile of the biofilm-forming PT13A strain and that at 37 degrees C the metabolism was nearly identical to that of the wild-type PT13A strain. Although it is possible that lysogenic bacteriophage alter the balance of phage types on a farm either by lytic competition or by altering the metabolic processes of the host cell in subtle ways, the different physiologies of the S. enterica serovar Enteritidis strains correlated most closely with minor, rather than major, genomic changes. These results strongly suggest that the pandemic of egg-associated human salmonellosis that came into prominence in the 1980s is primarily an example of bacterial adaptive radiation that affects the safety of the food supply.     

Development of a sequence typing scheme for differentiation of Salmonella Enteritidis strains

A DNA sequence typing scheme based on the caiC and SEN0629 loci was developed for differentiation of Salmonella Enteritidis strains and validated using a diverse collection of 102 isolates representing 38 phage types from different sources, year of isolation, geographical locations and epidemiological backgrounds. caiC encodes a probable crotonobetaine/carnitine-CoA ligase, and SEN0629 is a pseudogene. Our system allowed for discrimination of 16 sequence types (STs) among the 102 isolates analysed and intraphage type differentiation. Our findings also suggested that the stability of phage typing may be adversely affected by the occurrence of phage type conversion events. During a confirmatory phage typing analysis performed by a reference laboratory, 13 of 31 S. Enteritidis strains representing nine phage types were assigned phage types that differed from the ones originally determined by the same reference laboratory. It is possible that this phenomenon passes largely unrecognized in reference laboratories performing routine phage typing analyses. Our results demonstrate that phage typing is an unstable system displaying limited reproducibility and that the two-loci sequence typing scheme is highly discriminatory, stable, truly portable and has the potential to become the new gold standard for epidemiological typing of S .?Enteritidis strains.     

Limited genetic diversity in <Emphasis Type="Italic">Salmonella enterica</Emphasis> Serovar Enteritidis PT13

Background  

Salmonella enterica serovar Enteritidis has emerged as a significant foodborne pathogen throughout the world and is commonly characterized by phage typing. In Canada phage types (PT) 4, 8 and 13 predominate and in 2005 a large foodborne PT13 outbreak occurred in the province of Ontario. The ability to link strains during this outbreak was difficult due to the apparent clonality of PT13 isolates in Canada, as there was a single dominant pulsed-field gel electrophoresis (PFGE) profile amongst epidemiologically linked human and food isolates as well as concurrent sporadic strains. The aim of this study was to perform comparative genomic hybridization (CGH), DNA sequence-based typing (SBT) genomic analyses, plasmid analyses, and automated repetitive sequence-based PCR (rep-PCR) to identify epidemiologically significant traits capable of subtyping S. Enteritidis PT13.     

Plasmid profiles and randomly amplified polymorphic DNA analysis of Salmonella enterica serotype Enteritidis strains from outbreaks and sporadic cases in Turkey

The aim of the study was to investigate the characteristics of Salmonella serotype Enteritidis strains isolated from outbreaks and sporadic cases in Turkey by plasmid profiles and randomly amplified polymorphic DNA (RAPD) patterns. A total of 64 S. Enteritidis clinical strains were selected from the culture collection of the Enterobacteria Laboratory of Ankara University Medical School Department of Microbiology and Clinical Microbiology for molecular analysis using the plasmid profiles and RAPD method. Fifty-six isolates (88%) harbored one to four plasmids ranging in size from 2.5 to 100 kbp. 57 kbp plasmids were the most common plasmids, and forty-four strains (69%) carried 57 kbp plasmids alone or together with other plasmids. The outbreak strains carried the same plasmid profile: three plasmids sized 57, 40, 3.0 kbp. None of the strains analyzed displayed any RAPD bands with the primer OPB-17. By using primer p-1254, 42 strains (66%) were divided into fourteen RAPD patterns. Ten of the outbreak strains (77%) showed >80% similarity by cluster analysis program. Analysis of RAPD-PCR with primer p-1254 proved an easy, rapid and discriminative method complementing antibiogram and plasmid profiles in routine laboratories, and may contribute to the investigations of S. Enteritidis which still cause outbreaks in Turkey. This study presents the first report on S. Enteritidis isolates in Turkey investigated by plasmid profiles and RAPD methods.     

Correlation of Phenotype with the Genotype of Egg-Contaminating Salmonella enterica Serovar Enteritidis

The genotype of Salmonella enterica serovar Enteritidis was correlated with the phenotype using DNA-DNA microarray hybridization, ribotyping, and Phenotype MicroArray analysis to compare three strains that differed in colony morphology and phage type. No DNA hybridization differences were found between two phage type 13A (PT13A) strains that varied in biofilm formation; however, the ribotype patterns were different. Both PT13A strains had DNA sequences similar to that of bacteriophage Fels2, whereas the PT4 genome to which they were compared, as well as a PT4 field isolate, had a DNA sequence with some similarity to the bacteriophage ST64b sequence. Phenotype MicroArray analysis indicated that the two PT13A strains and the PT4 field isolate had similar respiratory activity profiles at 37°C. However, the wild-type S. enterica serovar Enteritidis PT13A strain grew significantly better in 20% more of the 1,920 conditions tested when it was assayed at 25°C than the biofilm-forming PT13A strain grew. Statistical analysis of the respiratory activity suggested that S. enterica serovar Enteritidis PT4 had a temperature-influenced dimorphic metabolism which at 25°C somewhat resembled the profile of the biofilm-forming PT13A strain and that at 37°C the metabolism was nearly identical to that of the wild-type PT13A strain. Although it is possible that lysogenic bacteriophage alter the balance of phage types on a farm either by lytic competition or by altering the metabolic processes of the host cell in subtle ways, the different physiologies of the S. enterica serovar Enteritidis strains correlated most closely with minor, rather than major, genomic changes. These results strongly suggest that the pandemic of egg-associated human salmonellosis that came into prominence in the 1980s is primarily an example of bacterial adaptive radiation that affects the safety of the food supply.     

Genetic diversity of human isolates of Salmonella enterica serovar Enteritidis in Malaysia

AIMS: The study was undertaken to determine clonal relationship and genetic diversity of the human strains of Salmonella enterica serovar Enteritidis isolated from 1995 to 2002 from different parts of Malaysia. METHODS AND RESULTS: Antimicrobial susceptibility test, plasmid profiling and pulsed-field gel electrophoresis were applied to analyse 65 human isolates of S. Enteritidis obtained over an eight year period from different parts of Malaysia. Four nonhuman isolates were included for comparison. A total of 14 distinct XbaI-pulsed-field profiles (PFPs) were observed, although a single PFP X1 was predominant and this particular clone was found to be endemic in Malaysia. The incidence of drug resistant S. Enteritidis remained relatively low with only 37% of the strains analysed being resistant to one or more antimicrobial agents. All except one resistant strain carried at least one plasmid ranging in size from 3.7 to 62 MDa giving nine plasmid profiles. The three isolates from raw milk and one from well-water had similar PFPs to that of the human isolates. CONCLUSIONS: Salmonella Enteritidis strains were more diverse than was previously thought. Fourteen subtypes were noted although one predominant clone persisted in Malaysia. The combination of pulsed-field gel electrophoresis, plasmid profiling and antibiograms provided additional discrimination to the highly clonal strains of S. Enteritidis. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report to assess the genotypes of the predominant clinical S. Enteritidis in different parts of the country. As S. Enteritidis is highly endemic in Malaysia, the data generated would be useful for tracing the source during outbreaks of gastroenteritis in the study area.     

Influence of spv plasmid genes group in Salmonella Enteritidis virulence for chickens. I. Occurrence of spv plasmid genes group in Salmonella Enteritidis large virulence plasmid

Many Salmonella Enteritidis virulence factors are encoded by genes localized on plasmids, especially large virulence plasmid, in highly conserved fragment, they create spv plasmid gene group. The aims of realized researches were spv genes occurrence evaluation and composition analysis among Salmonella Enteritidis strains caused infection in chickens. Researches were realized on 107 isolates, where in every cases large virulence plasmid 59 kbp size were detected. Specific nucleotides sequences of spv genes (spvRABCD) were detected in 47.7% of isolates. In the rest of examined bacteria spv genes occurred variably. Most often extreme genes of spv group, like spvR and spvD were absent, what could indicate that factors encoded by them are not most important for Salmonella Enteritidis live and their expressed virulence.     

Characterization of class I integrons among Salmonella enterica serovar Enteritidis isolated from humans and poultry

A total of 84 Salmonella enterica serovar Enteritidis (S. Enteritidis) isolates, 42 of human and 42 of poultry origin, were characterized for antimicrobial resistance patterns and class I integrons. Among them, 58 (69%) S. Enteritidis were multidrug-resistant (MDR) and showed resistance to two or more antibiotic classes. By PCR assays and DNA sequencing, 50 (59.5%) S. Enteritidis isolates were found to carry class I integrons. Amplification of internal variable regions of class I integrons revealed five different arrays (0.75 kb only, 1 kb only, 1.3 kb only, both 1 and 1.2 kb, and both 1 and 1.3 kb). The integrons were further sequenced and the dfrA25 (0.75 kb), aadA1 (1 kb), aadA2 (1 kb), bla(PSE1) (1.2 kb) aadA6-orfD (1.3 kb) gene cassette arrays were identified. Ciprofloxacin minimum inhibitory concentration (MIC) values for the three isolates that showed resistance or reduced susceptibility via the disc diffusion method were 0.5-4 μg mL(-1), although only three isolates exhibited resistance to cefteriaxone (MIC: 128-256 μg mL(-1)) and four isolates were resistant to florfenicol (MIC: 32-128 μg mL(-1)). In conclusion, the high rates of multidrug-resistance and class I integrons found among S. Enteritidis isolates in humans and poultry in Tehran suggest that efforts are needed to confine the prevalence of MDR Salmonella isolates.     

Characterization of Salmonella virchow phage types by plasmid profile and IS200 distribution

The type strains of the 57 phage types of Salmonella virchow have been characterized by plasmid profile and by distribution of the insertion sequence IS 200 . Thirty-two strains carried plasmids and 21 profile types were identified; 17 strains were resistant to antimicrobial agents. In contrast only six of the type strains carried IS 200 elements and three patterns were identified. Within Salm. virchow phage type 31, five of 10 wild-type isolates carried plasmids and two plasmid profiles were identified; in contrast, an IS 200 element was identified in the genome of only one of these strains. It is concluded that for Salm. virchow , IS 200 is unlikely to significantly extend the degree of discrimination achieved by phage typing which may be supplemented when appropriate by plasmid profile typing.     

Characterization of Salmonella enterica serovar typhimurium from marine environments in coastal waters of Galicia (Spain)

Twenty-three Salmonella enterica serovar Typhimurium isolates from marine environments were characterized by phage typing, pulsed-field gel electrophoresis (PFGE) analysis, plasmid analysis, and antibiotic resistance, and the distribution of the different types in the coastal waters were subsequently analyzed. Five phage types were identified among the isolates (PT41, PT135, PT99, DT104, and DT193). PT135 isolates were exclusively detected during the winter months from 1998 to 2000, whereas DT104 and PT41 isolates were detected exclusively in the summer months from 2000 to 2002. XbaI PFGE analysis revealed 9 PFGE types, and plasmid profiling identified 8 plasmid types (with 1 to 6 plasmids) among the isolates. Only three isolates presented multidrug resistance to antibiotics. Two DT104 isolates were resistant to 8 and 7 antibiotics (profiles ACCeFNaSSuT and ACeFNeSSuT), whereas a PT193 isolate presented resistance to 6 antibiotics (profile ACFSSu). In addition, four PT41 isolates were resistant to a single antibiotic. The detection of multidrug-resistant phage types DT104 and DT193 in shellfish emphasizes the importance of monitoring the presence of Salmonella in routine surveillance of live bivalve molluscs.     

Restriction enzyme analysis of randomly amplified polymorphic DNA amplicons of Salmonella enterica ser. Enteritidis PT4 and Typhimurium DT104

Salmonella enterica serotype Enteritidis PT4 and Typhimurium DT104 isolates were characterized using a random amplification of polymorphic DNA (RAPD) protocol found previously to be highly discriminatory for isolates of Salmonella . Profiles generated with a single primer 1254, and independently 1283, successfully characterized an outbreak strain of Enteritidis PT4 but could not differentiate epidemiologically unrelated strains of Enteritidis PT4 from the outbreak strains. Primer 1254 differentiated one strain, and 1283 two strains of Typhimurium DT104 previously undifferentiated on the basis of biochemical and physical properties. Subsequent analysis using a combination of RAPD and restriction enzyme analysis could not provide additional differentiation of Enteritidis PT4 and Typhimurium DT104 isolates but did, however, exhibit the potential to be a useful combination of molecular techniques.     

Multi Locus Variable-Number Tandem Repeat (MLVA) Typing Tools Improved the Surveillance of Salmonella Enteritidis: A 6 Years Retrospective Study

Surveillance of Salmonella enterica subsp. enterica serovar Enteritidis is generally considered to benefit from molecular techniques like multiple-locus variable-number of tandem repeats analysis (MLVA), which allow early detection and confinement of outbreaks. Here, a surveillance study, including phage typing, antimicrobial susceptibility testing and MLVA on 1,535 S. Enteritidis isolates collected between 2007 and 2012, was used to evaluate the added value of MLVA for public health surveillance in Belgium. Phage types PT4, PT8, PT21, PT1, PT6, PT14b, PT28 and PT13 dominate the Belgian S. Enteritidis population. The isolates of S. Enteritidis were most frequently susceptible to all antibiotics tested. 172 different MLVA profiles were detected, of which 9 frequent profiles included 67.2% of the S. Enteritidis population. During a serial passage experiment on selected isolates to investigate the in vitro stability of the 5 MLVA loci, no variations over time were observed indicating that the MLVA profiles were stable. The MLVA profile of isolates originating from different outbreaks in the Democratic Republic of the Congo (DRC) between 2010 and 2011 were distinct from any of the MLVA profiles found in Belgian isolates throughout the six year observational period and demonstrates that MLVA improves public health surveillance of S. Enteritidis. However, MLVA should be complemented with other subtyping methods when investigating outbreaks is caused by the most common MLVA profile.     

Phage types of Australian isolates of Salmonella enterica subsp. enterica serovar Virchow

Australian isolates (79) of Salmonella enterica subsp. enterica serovar Virchow ( Salmonella Virchow) were characterized by phage typing. Thirteen phage types were identified, of which phage type (PT) 8, representing 54 of 79 isolates, was predominant, as it had been in England and Wales up to 1994 when it was replaced by PT26. Other phage types identified in Australia were distinct from those observed in England and Wales. This suggests that PT8 may be a global phage type, while others may be distinct to particular geographical regions.