Diversity of Salmonella Isolates from Central Florida Surface Waters

Identification of Salmonella serotypes is important for understanding the environmental diversity of the genus Salmonella. This study evaluates the diversity of Salmonella isolates recovered from 165 of 202 Central Florida surface water samples and investigates whether the serotype of the environmental Salmonella isolates can be predicted by a previously published multiplex PCR assay (S. Kim, J. G. Frye, J. Hu, P. J. Fedorka-Cray, R. Gautom, and D. S. Boyle, J. Clin. Microbiol. 44:3608–3615, 2006, http://dx.doi.org/10.1128/JCM.00701-06). Multiplex PCR was performed on 562 Salmonella isolates (as many as 36 isolates per water sample) to predict serotypes. Kauffmann-White serogrouping was used to confirm multiplex PCR pattern groupings before isolates were serotyped, analyzed by pulsed-field gel electrophoresis, and assayed for antimicrobial susceptibility. In 41.2% of the Salmonella-positive water samples, all Salmonella isolates had identical multiplex PCR patterns; in the remaining 58.8%, two or more multiplex PCR patterns were identified. Within each sample, isolates with matching multiplex PCR patterns had matching serogroups. The multiplex patterns of 495 isolates (88.1%) did not match any previously reported pattern. The remaining 68 isolates matched reported patterns but did not match the serotypes for those patterns. The use of the multiplex PCR allowed the number of isolates requiring further analysis to be reduced to 223. Thirty-three Salmonella enterica serotypes were identified; the most frequent included serotypes Muenchen, Rubislaw, Anatum, Gaminara, and IV_50:z4,z23:−. A majority (141/223) of Salmonella isolates clustered into one genotypic group. Salmonella isolates in Central Florida surface waters are serotypically, genotypically, and phenotypically (in terms of antimicrobial susceptibility) diverse. While isolates could be grouped as different or potentially the same using multiplex PCR, the multiplex PCR pattern did not predict the Salmonella serotype.     

Staphylococcal and other Bacterial Species Associated with Intramammary Infections in Danish Dairy Herds

Four thousand six hundred forty– five quarter milk samples from 1179 cows from 20 commercial dairy herds were examined in order to determine the prevalence of bacterial species. A total of 859 isolates from 839 (18.1%) culture positive samples could be assigned to 34 different species and subspecies. Diagnostics of staphylococcal species was based on conventional procedures able to differentiate between all 36 species and subspecies presently acknowledged. Staphylococcus aureus was found in 10.2% of the samples and was the most common species isolated. Streptococcus dysgalactiae (1.6%) and Streptococcus uberis (1.4%) were the second and third most common species isolated. Seventeen different coagulase negative staphylococcal species (CNS) were found in 4.1% of the samples. The most frequently isolated CNS were S. epidermidis (1.3%), S. chromogenes (1.0%) and S. simulans (0.7%). Isolates of S. aureus were phage typed, and isolates of S. epidermidis were investigated by phage typing, antibiogram typing, and biotyping. A total of 378 (79.9%) isolates of S. aureus could be typed by phages, assigning them to 18 different phage types. However, 6 phage types accounted for 92.1% of the typable isolates. One to 2 phage types predominated within each herd. Eleven (18%) isolates of S. epidermidis could be typed by phages, assigning the isolates to 3 different types. Biotyping of S. epidermidis produced a total of 8 different types, the most common accounting for 29.5% of the isolates. A total of 6 different antibiogram types were observed among all isolates of S. epidermidis. Resistance towards penicillin (36.1%), tetracycline (9.8%) and streptomycin (9.8%), were recorded in the isolates of S. epidermidis. However, 35 (57.4%) of the isolates were susceptible to all 12 antibiotics tested.     

Analysis of molecular markers genetically linked to the Leptosphaeria maculans avirulence gene AvrLm1 in field populations indicates a highly conserved event leading to virulence on Rlm1 genotypes

Map-based cloning of the avirulence gene AvrLm1 of Leptosphaeria maculans was initiated utilizing a genetic map of the fungus and a BAC library constructed from an AvrLm1 isolate. Seven polymorphic DNA markers closely linked to AvrLm1 were identified. Of these, two were shown to border the locus on its 5' end and were present, with size polymorphism, in both the virulent and the avirulent isolates. In contrast, three markers, J19-1.1, J53-1.3 (in coupling phase with avirulence), and Vir1 (in repulsion phase with avirulence), cosegregated with AvrLm1 in 312 progeny from five in vitro crosses. J19-1.1 and J53-1.3 were never amplified in the virulent parents or progeny, whereas Vir1 was never amplified in the avirulent parents or progeny. J19-1.1 and J53-1.3 were shown to be separated by 40 kb within a 184-kb BAC contig. In addition, the 1.6-cM genetic distance between J53-1.3 and the nearest recombinant marker corresponded to a 121-kb physical distance. When analyzing a European Union-wide collection of 192 isolates, J53-1.3, J19-1.1, and Vir1 were found to be closely associated with the AvrLm1 locus. The results of polymerase chain reaction amplification with primers for the three markers were in accordance with the interaction phenotype for 92.2% (J53-1.3), 90.6% (J19-1.1), and 88.0% (Vir1) of the isolates. In addition, genome organization of the AvrLm1 region was highly conserved in field isolates, because 89.1% of the avirulent isolates and 79.0% of the virulent isolates showed the same association of markers as that of the parents of in vitro crosses. The large-scale analysis of field isolates with markers originating from the genetic map therefore confirms (i) the physical proximity between the markers and the target locus and (ii) that AvrLm1 is located in (or close to) a recombination-deficient genome region. As a consequence, map-based markers provided us with high-quality markers for an overview of the occurrence of race "AvrLm1" at the field scale. These data were used to propose hypotheses on evolution towards virulence in field isolates.     

Application of pulsed-field gel electrophoresis to laboratory surveillance of small community outbreaks of Salmonella enterica serovar Typhimurium

Infectious diarrhea syndrome is an important cause of human morbidity around the world, and Salmonella genus remains one of the most prevalent etiology. Salmonella enterica serovar Typhimurium outbreak-associated isolates received by the Laboratory for Enteric Pathogens from N.I.R.D.M.I. "Cantacuzino" for confirmation and typing were analyzed by genomic pulsed-field gel electrophoresis (PFGE) and phage susceptibility testing to establish their relatedness. Both typing methods proved to have similar discriminatory power. The isolates originating from the same outbreak belonged to the same phage type and showed indistinguishable PFGE profiles. The molecular characterization of autochthonal Salmonella enterica Typhimurium outbreak human isolates provided laboratory evidence that epidemiologically related isolates collected from community outbreaks of disease were also genetically related. In order to improve the national and international surveillance of major foodborne pathogens the reference laboratory centers are required to establish and maintain the capacity to perform a wide range of both phenotypic and genotypic methods to support outbreak investigations.     

Isolation of virulent Yersinia enterocolitica from porcine tongues.

Thirty-one tongues from apparently normal, freshly slaughtered pigs were assayed for the presence of Yersinia enterocolitica by different enrichment and postenrichment techniques. Sixteen different isolates were recovered, including six of serotype O:8, four of serotype O:6,30, two of serotype O:3 phage type IXb, and one each of serotypes O:13,7, O:18, and O:46. One isolate was not typable. Cold enrichment in phosphate-buffered saline followed by treatment with dilute KOH or subsequent enrichment in modified Rappaport broth recovered 12 and 7 isolates, respectively. Four of the same isolates were recovered from the same tongues by both procedures. Cold enrichment without a selective postenrichment treatment recovered two isolates. Direct enrichment in modified Rappaport broth or modified selenite broth was ineffective in recovering yersiniae, as no isolates were obtained by either method. All of the serotype O:8 isolates were virulent to mice, causing the death of adults after oral challenge. This is the first report that associates Y. enterocolitica serotype O:8 with a natural reservoir.     

Characteristics of group A streptococcal bacteriophages

Friend, Patric L. (Northwestern University Medical School, Chicago, Ill.), and Hutton D. Slade. Characteristics of group A streptococcal bacteriophages. J. Bacteriol. 92:148-154. 1966.-A medium for the growth of group A streptococcal phages is described, consisting of Brain Heart Infusion broth supplemented with 0.2% yeast extract, 10(-4)m CaCl(2), and 10 mug/ml of dl-tryptophan. Cell and phage growth in this medium was excellent, and did not require the addition of serum or other proteins as indicated by other workers. Growth of one phage has also been achieved in a completely synthetic medium. The adsorption characteristics of two group A phages in protein broth and synthetic broth were studied, and the initial adsorption of phage was found to be more extensive in synthetic broth. However, the final amounts of adsorption in both were similar. The addition of purified group A carbohydrate antigen to the adsorption mixture in synthetic broth had no effect on the adsorption, and cells containing type-specific M protein adsorbed phage at the same rate as those lacking M protein. It was concluded that neither the group antigen nor the type antigen was the primary site of phage adsorption. One-step growth curves of the two phages showed a second step or burst occurring. Sonic oscillation of the bacterial cultures, which broke up the chains to single cells, abolished the second step of the growth curve. It appears that the second step is a function of the chain formation of streptococcal cells.     

Differentiation of Shigella strains by plasmid profile analysis, serotyping and phage typing

Ninety-one Shigella flexneri and 29 Shigella sonnei strains isolated during 1994 from sporadic cases of shigellosis and healthy carriers were analyzed for plasmid profile in order to compare the discriminating ability of this method with that of serotyping and phage typing. Our study revealed 10 plasmid profiles (PP) among S. sonnei strains. A total of 26 out of 29 (89%) S. sonnei isolates could be placed into two phage types (type 1 and 20) comprising four PP for phage type 1 and seven PP for type 20, respectively. Twenty-three different PP were identified among S. flexneri strains. Each serotype was associated with a specific predominant plasmid profile, except serotype 2a. This serotype, the most frequently isolated in Romania, was still rather homogeneous: 33 out of 39 isolates belonged to phage type 125, 27 of which could be placed into two related PP (F10 and F17). Comparison of plasmid patterns of epidemiologically independent S. flexneri serotype 2a isolates with those exhibited by 45 serotype 2a isolates associated to six independent outbreaks revealed the same homogeneity. Thirty-eight strains, representing 4 of 6 outbreaks, had F10 and F17 plasmid patterns. The discrimination indices (D) for plasmid profile analysis alone (D = 0.890) and for the combination of serotyping and phage typing (D = 0.841) indicate that both typing systems have a nearly similar ability of discriminating among S. flexneri strains. By combining the results of the three typing methods, a total of 42 types are distinguished and the D value is 0.942. Our data suggest that plasmid profile analysis can complement phenotyping methods resulting in a degree of discrimination that cannot be achieved by either system alone.     

Isolation of insertion, deletion, and nonsense mutations of the uracil-DNA glycosylase (ung) gene of Escherichia coli K-12.

Two uracil-DNA glycosylase (ung) mutation selection procedures based upon the ability of uracil glycosylase to degrade the chromosomes of organisms containing uracil-DNA were devised to obtain a collection of well-defined ung alleles. In an enrichment procedure, lysogens were selected from Escherichia coli cultures infected with lambda pKanr phage containing uracil in their DNA. (These uracil-DNA phage were prepared by growth on host cells deficient in both dUTPase and uracil-DNA glycosylase.) The lysogenic Kanr population was enriched for uracil glycosylase-deficient mutants by a factor of 10(4). In a phage suicide selection procedure, lambda pung+ phage were unable to form plaques on dut ung cells containing uracil-DNA in their chromosomes, and all of the progeny were lambda pung-. Deletion, insertion (ung::Mu and ung::Tn10), nonsense, and missense mutants were isolated by using these procedures. Extracts of three insertion mutants contained no detectable enzyme activity. All of the other mutant isolates had less than 1% of the normal uracil glycosylase specific activity. The previously studied ung-1 allele, which was derived by N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis, produced about 0.02% of the normal amount of uracil glycosylase activity. No significant phenotypic differences between ung-1 and ung::Tn10 alleles were observed. Variations of the lysogen selection procedure may be helpful for isolating other DNA glycosylase mutations in E. coli and other organisms.     

Phenotypic and Molecular Characterization of Human <Emphasis Type="Italic">Salmonella enterica</Emphasis> serovar 4,[5],12:i:- Isolates in Slovakia

Forty-three epidemiologically unrelated emerging Salmonella enterica subsp. enterica serovar 4,[5],12:i:- strains isolated during the period 2009–2010 in Slovakia were characterized by phenotypic and genotypic methods. Thirty-one isolates (72.1%) expressed resistance to ampicillin, streptomycin, sulfizoxazole, and tetracycline [R-type ASSuT]. The majority of the strains belonged to both definitive phage types DT193 (30.2%) and U311 (27.9%). Other phage types identified were U302 (6.9%), DT18 (4.7%), and DT194 (2.3%). Twelve strains (27.9%) were not typeable. Pulsed-field gel electrophoresis analysis identified three closely related major banding profiles (X1, X1a, and X2), suggesting the similarity and close epidemiological relationship between S. enterica serovar 4,[5],12:i:- strains. In two isolates with R-type ASSuT, phage type NT and in one isolate with R-type ACROSSuSxTTTMPNA, phage type DT193 class 1 integrons were found encoding bla_PSE-1 and dfrA, aadA1, respectively.     

Genotypes of multidrug-resistant Salmonella enterica serotype typhimurium from two regions of Kenya

A combination of phage typing and pulsed-field gel electrophoresis of Xbal-digested chromosomal DNA has been used to study the epidemiological relationships of multidrug-resistant Salmonella enterica serotype typhimurium from Nairobi (64 isolates) and Kilifi (40 isolates) collected over the period 1994-1997. Isolates from Nairobi belonged to 11 definitive phage types (DTs) encompassing eight different PFGE patterns. In contrast, isolates from Kilifi were mainly DT 56 (60%) and all fell into a single PFGE pattern. The remaining isolates did not conform to a recognisable phage type. We conclude that multidrug-resistant S. typhimurium infections from Nairobi were caused by multiple strains while those from Kilifi were likely to be from a microepidemic caused by a single clone.     

Characterization of Salmonella enterica serovar Enteritidis isolates recovered from blood and stool specimens in Thailand

ABSTRACT: BACKGROUND: Bacteremia due to Salmonella spp. is a life-threatening condition and is commonly associated with immune compromise. A 2009 observational study estimated risk factors for the ten most common non-typhoidal Salmonella (NTS) serovars isolated from Thai patients between 2002-2007. In this study, 60.8% of Salmonella enterica serovar Enteritidis isolates (n = 1517) were recovered from blood specimens and infection with Salmonella serovar Enteritidis was a statistically significant risk factor for bacteremia when compared to other NTS serovars. Based on this information, we characterized a subset of isolates collected in 2008 to determine if specific clones were recovered from blood or stool specimens at a higher rate. Twenty blood isolates and 20 stool isolates were selected for antimicrobial resistance testing (MIC), phage typing, PFGE, and MLVA. Result Eight antibiogrammes, seven MLVA types, 14 XbaI/BlnI PFGE pattern combinations, and 11 phage types were observed indicating considerable diversity among the 40 isolates characterized. Composite analysis based on PFGE and MLVA data revealed 22 genotypes. Seven of the genotypes containing two or more isolates were from both stool and blood specimens originating from various months and zones. Additionally, those genotypes were all further discriminated by phage type and/or antibiogramme. Ninety percent of the isolates were ciprofloxacin resistant. CONCLUSIONS: The increased percentage of bloodstream infections as described in the 2009 observational study could not be attributed to a single clone. Future efforts should focus on assessing the immune status of bacteriaemic patients and identifying prevention and control measures, including attribution studies characterizing non-clinical (animal, food, and environmental) isolates.     

New complex recombinant genotype of hepatitis B virus identified in Vietnam

A novel variant of hepatitis B virus was identified in Vietnam. This strain (HBV-VH24) had a novel intergenotypic recombination between genotypes A, C, and G. VH24 showed high similarity (98.3 to 98.9%) to the "aberrant strains" among Vietnamese isolates reported by Hannoun et al. (C. Hannoun et al., J. Gen. Virol. 81:2267-2272, 2000) and also had similar breakpoints of recombination. Phylogenetic analysis of the complete genome of these strains formed a separate clade. Furthermore, their pre-S/S gene-encoded seven unique conserved amino acid residues were not present in other genotypes. These findings support the designation of the new genotype I.     

The highly virulent 2006 Norwegian EHEC O103:H25 outbreak strain is related to the 2011 German O104:H4 outbreak strain

In 2006, a severe foodborne EHEC outbreak occured in Norway. Seventeen cases were recorded and the HUS frequency was 60%. The causative strain, Esherichia coli O103:H25, is considered to be particularly virulent. Sequencing of the outbreak strain revealed resemblance to the 2011 German outbreak strain E. coli O104:H4, both in genome and Shiga toxin 2-encoding (Stx2) phage sequence. The nucleotide identity between the Stx2 phages from the Norwegian and German outbreak strains was 90%. During the 2006 outbreak, stx(2)-positive O103:H25 E. coli was isolated from two patients. All the other outbreak associated isolates, including all food isolates, were stx-negative, and carried a different phage replacing the Stx2 phage. This phage was of similar size to the Stx2 phage, but had a distinctive early phage region and no stx gene. The sequence of the early region of this phage was not retrieved from the bacterial host genome, and the origin of the phage is unknown. The contaminated food most likely contained a mixture of E. coli O103:H25 cells with either one of the phages.     

Isolation and characterization of a bacteriophage polysaccharide.

A high molecular weight heteropolysaccharide, composed of glucose, glucuronic acid, N-acetylglucosamine, and mannose in an approximate molar ratio of 1:2:2:5, respectively, was isolated from phage K-2 and from the soluble fraction of phage-infected Aerobacter aerogenes lysates. Treatment of pure phage with 8 M urea at 4 degrees quantitatively solubilizes the bound polysaccharide and capsular polysaccharide (Yurewicz, E.C., Ghalambor, M.A., Duckworth, D.H., and Heath, E.C. (1971) J. Biol. Chem. 246, 5607-5616) with the release of only traces of other phage constituents; on this basis, it was concluded that the polysaccharide, like the the glycanohydrolase, is externally localized in the phage structure. Phage polysaccharide and glycanohydrolase fractionate similarly on ion exchange resins and gel electrophoresis in sodium dodecyl sulfate, but each may be purified to homogeneity by the procedures employed. The biosynthesis of the polysaccharide was shown to be uniquely dependent upon phage K-2 infection by: (a) absence of the polysaccharide in cells, the culture filtrate, or sonicated extracts of uninfected cells; (b) kinetics of polysaccharide synthesis following phage infection; and (c) isotopic double-labeling experiments that demonstrated the synthesis of polysaccharide only after initiation of phage replication in infected cells.     

Fecal carriage of Escherichia coli O157:H7 and carcass contamination in cattle at slaughter in northern Italy.

Feedlot cattle slaughtered at a large abattoir in northern Italy during 2002 were examined for intestinal carriage and carcass contamination with Escherichia coli O157:H7. Carcass samples were taken following the excision method described in the Decision 471/2001/EC, and fecal material was taken from the colon of the calves after evisceration. Bacteria were isolated and identified according to the MFLP-80 and MFLP-90 procedures (Food Directorate's Health Canada's). Eighty-eight non-sorbitol-fermenting E. coli O157:H7 isolates were obtained from 12 of the 45 calves examined. In particular, E. coli O157:H7 isolates were found in 11 (24%) fecal and five (11%) carcass samples. PCR analysis showed that all 11 fecal samples and five carcass samples carried eae-gamma1-positive E. coli O157:H7 isolates. In addition, genes encoding Shigatoxins were detected in O157:H7 isolates from nine and two of those 11 fecal and five carcasses, respectively. A representative group of 32 E. coli O157:H7 isolates was analyzed by phage typing and DNA macrorestriction fragment analysis (PFGE). Five phage types (PT8, PT32v, PT32, PT54, and PT not typable) and seven (I-VII) distinct restriction patterns of similarity >85% were detected. Up to three different O157:H7 strains in an individual fecal sample and up to four from the same animal could be isolated. These findings provide evidence of the epidemiological importance of subtyping more than one isolate from the same sample. Phage typing together with PFGE proved to be very useful tools to detect cross-contamination among carcasses and should therefore be included in HACCP programs at abattoirs. The results showed that the same PFGE-phage type E. coli O157:H7 profile was detected in the fecal and carcass samples from an animal, and also in two more carcasses corresponding to two animals slaughtered the same day.     

Phage types and pulsed-field gel electrophoresis patterns of <Emphasis Type="Italic">Salmonella enterica</Emphasis> serovar Enteritidis isolated from humans and chickens

We analyzed 66 Salmonella Enteritidis isolates in 2002. Thirty isolates were obtained from human patients with diarrhea, and 36 were obtained from chickens. A total of ten phage types (PT) were identified in the human and chicken isolates. PT1 and PT21 were the predominant PTs in both the human (20% and 13%) and chicken (17% and 47%) isolates. Twelve pulsotypes were generated by PFGE and divided into two major groups. Most of the PFGE types were categorized into cluster group 1. Eighteen chicken isolates in cluster group 1 showed high-level genetic association (>95%) with 22 other human isolates. Additionally, six chicken isolates from cluster group 2 showed fairly high-level genetic association (>95%) with the other seven human isolates. The highest levels of genetic association in humans and chickens were seen with A5-PT21 (11 isolates), A2-PT1 (7 isolates), and B1-PT4 (6 isolates). The Pulsed-Field Gel Electrophoresis (PFGE) and phage typing provided conclusive evidence that human Salmonella infections are attributable to the consumption of contaminated chicken.     

Evaluation of seven experimental phages for inclusion in the international phage set for the epidemiological typing of Listeria monocytogenes.

The purpose of our study was to evaluate the inclusion of seven experimental phages into the international phage set for subtyping Listeria monocytogenes. The seven additional phages included the broad-host-range virulent Myoviridae phage A511 (M. J. Loessner, Appl. Environ. Microbiol. 57:1912-1918, 1991), three temperate phages from the Danish subsystem for typing serotype 1/2 strains (12682, 6223, and 5775) (P. Gerner-Smidt, V.T. Rosdahl, and W. Frederiksen, APMIS 101:160-167, 1993), and three temperate phages isolated by this laboratory in France (9425, 1313, and 197). A panel of 395 Listeria monocytogenes isolates (including 180 that were non-phage typeable by the international set) were used in the study for a comparison of the lytic spectra of the various bacteriophages. These results showed that the inclusion of five of the experimental phages contributed greatly to the overall typeability and discriminatory power of the system, especially for strains within serogroup 1/2.     

Prevalence of Salmonella enterica serovars and genovars from chicken carcasses in slaughterhouses in Spain

AIMS: To determine the prevalence of Salmonella enterica serovars in chicken carcasses in slaughterhouses in Spain and to examine genotypic relations among these serovars. METHODS AND RESULTS: A total of 336 chicken carcasses were collected from six slaughterhouses in Northwestern Spain. Salmonellae were isolated (ISO-6579-1993), serotyped, phage-typed, ribotyped and antibiotyped against 20 antibiotics. Salmonella strains were detected in 60 (17.9%) carcasses. Isolates belonged to nine different serotypes, with Salm. Enteritidis being the most common. Three strains (5%) were resistant to one antibiotic and 24 (40%) were multi-resistant (to more than one antibiotic). The most frequently encountered resistances were to sulphamides, fluoroquinolones and tetracycline. Ribotyping was able to differentiate isolates of the same serotype and phage type. CONCLUSIONS: The Salmonella serotypes and phage types detected are among those most frequently associated with human diseases in Spain. The large percentage of antimicrobial resistant strains is a matter for concern. A high genetic relationship between strains from different slaughterhouses was found. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides detailed information about Salmonella isolates from poultry in Spain. It emphasizes the importance of controlling this pathogen in poultry products, and suggests the need for more prudent use of antibiotics.     

Host range and lytic capability of four bacteriophages against bovine and clinical human isolates of Shiga toxin-producing Escherichia coli O157:H7

Aims:  To evaluate host range and lytic capability of four bacteriophages (rV5, wV7, wV8 and wV11) against Escherichia coli O157:H7 (STEC O157:H7) from cattle and humans.
Methods and Results:  Four hundred and twenty-two STEC O157:H7 isolates (297 bovine; 125 human) were obtained in Alberta, Canada. The four phages were serially diluted and incubated for 5 h with overnight cultures of STEC O157:H7 to estimate their multiplicity of infection (MOI). All bovine STEC O157:H7 were subjected to pulsed-field gel electrophoresis (PFGE) and phage typing (PT). Phage wV7 lysed all human and bovine isolates irrespective of PFGE genotype or PT phenotype and exhibited the lowest MOI (0·004–0·006, P  < 0·0001) of all phages. Phages rV5 and wV11 exhibited a lower MOI (0·002–0·04, P  < 0·0001) than did phage wV8 (25–29) and they had a narrower host range than wV7 or wV8. Phages rV5, wV11 and wV8 lysed 342 (81·0%), 321 (76·1%) and 407 (96·4%), respectively, of the 422 isolates. Susceptibility of bovine STEC O157:H7 to rV5, w11 and wV8 was influenced by PFGE genotype and/or PT phenotype.
Conclusions:  Phages exhibited activity against the majority of bovine and human STEC O157:H7 isolates. PFGE genotype and/or PT phenotype of the host-target influenced their vulnerability to phage attack. Susceptibility of bovine STEC O157:H7 to phage may also differ among farms. Both lytic capability and host range should be considered in the selection of therapeutic phage for on-farm control of STEC O157:H7.
Significance and Impact of the Study:  The present work indicates that a four-phage cocktail should be equally effective at mitigating STEC O157:H7 isolates both of bovine and of human origin. Given that some STEC O157:H7 exhibited resistance to some but not all phages, a phage cocktail is the logical approach to efficacious on-farm therapy.     

Incidence of Yersinia enterocolitica in raw milk in eastern France.

A total of 75 raw milk samples collected from a central dairy or from retailers in Alsace, France, were analyzed for the presence of Yersinia enterocolitica. Three procedures were used: enrichment at 4 degrees C for 1 month; enrichment in modified Rappaport medium at room temperature for 72 h after a preenrichment at 4 degrees C for 1 month; and enrichment in a new medium containing sucrose, tris(hydroxymethyl)aminomethane, sodium azide, and ampicillin (PSTA) at 28 degrees C for 48 h after a preenrichment at 4 degrees C for 1 month. Isolation of Y. enterocolitica was made on Hektoen medium plus ampicillin. Sixty-one samples were positive (81.4%), but the PSTA medium produced the greatest number of isolates. Biochemical, serological, and phage typing of 40 isolates showed that chemotype 1 and serogroup O:5 were predominant. In seven cases, two different strains were obtained from the same samples. Most of the 66 isolates tested for their antimicrobial susceptibility were resistant to ampicillin and carbenicillin, and all were sensitive to tetracycline, chloramphenicol, streptomycin, sulfonamides, and mercuric ions.