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Salmonella contamination is a critical problem in poultry farms, with serious consequences for both animals and food products. The aim of this study is to investigate the use of phage cocktails to reduce Salmonella contamination in poultry farms. Within the scope of the study, Salmonella phages were isolated from chicken stool. After the host range of phages was determined, morphological characterization was performed through transmission electron microscopy analysis. Then, replication parameters and adsorption rates were determined by one-step growth curves. After that, phage cocktail was prepared, and its effectiveness was tested in three environments, which were drinking water, shavings, and plastic surfaces. The results obtained have demonstrated that the phage cocktail can reduce Salmonella count up to 2.80 log10 units in drinking water, up to 2.30 log10 units on shavings, and 2.31 log10 units on plastic surfaces. It has been determined that phage cocktails could be a successful alternative in reducing Salmonella contamination in poultry environment. This work is the first study to investigate the use of phage cocktails for reducing Salmonella contamination in poultry water and on shavings, and it is presumed that the results obtained will contribute to the fight against pathogens by making them applicable to poultry farms.

This study was designed to evaluate the possibility of using phage-amplification assay for discriminating between antibiotic-sensitive and antibiotic-resistant Salmonella Typhimurium. The characteristics of Salmonella phage PBST32 were determined by adsorption rate, one-step growth curve, and lytic activity. The ability of phage-based method to detect S. Typhimurium ATCC 19585 (STCIP) was determined in single culture and bacterial mixtures of S. Typhimurium ATCC 19585 (STWT), Klebsiella pneumoniae, and Staphylococcus aureus. The adsorption rates of PBST32 were 95% and 93% against STWT and STCIP after 20 min, respectively. The PBST32 showed latent period of 20 min and average burst size of 90 against STWT and STCIP. The STCIP was selectively detected in mixtures of S. aureus, K. pneumoniae, and STWT by phage amplification assay. These results provide useful information for designing phage amplification method that can differentially detect antibiotic-resistant pathogens.

S. Enteritidis and S. Typhimurium are typically linked to foodborne outbreaks. Phages have continued to expand in various food applications. In this study, microencapsulation is applied for enhancing the stability and efficacy of phages as bio-control agent. Microencapsulated phage cocktail kept in aluminium laminated foil bag (LF) at 4 °C showed the highest survivability with a titer loss of 0.5 log PFU/g after 12 weeks of storage. Titer loss of phage cocktail lysate >4 log PFU/mL was observed after 12 weeks, at 4 °C. Color change of microencapsulated phage cocktail kept in LF at 4 °C did not show any significant difference during storage, and water activity (free water content) at 0.13 was found in these conditions. In-vitro study, S. Enteritidis and S. Typhimurium were decreased 1.79 and 3.63 log CFU/mL, respectively at 37 °C. Whereas, 0.43 and 0.76 log CFU/mL, respectively were observed at 10 °C. In foods, S. Enteritidis and S. Typhimurium were decreased 0.57 and 1.78 log CFU/cm2, respectively in meat. Whereas, 0.86 and 1.2 log CFU/g, respectively were observed in sprout. Foods with/without microencapsulated phage cocktail showed non-significant differences in liking scores after 2 days of storage. Overall, microencapsulated phage cocktail suggests another alternative for phage-based biocontrol with improved stability and efficacy for food application.

The quality of milk is directly linked to a reduced number of deteriorating microorganisms, low somatic cell count and absence of pathogens. Therefore, the objective of this study was to evaluate the microbiological quality of type C pasteurized milk, marketed in the Cariri region, in the state of Ceará. The Most Probable Number (MPN) of Coliforms at 45°C and the presence of Salmonella spp were determined, according to the limits established by the Resolution of the Collegiate Board (RCD) number 12, 02/2001. 33 samples of pasteurized type C milk sold in commercial establishments, including supermarkets and bakeries, were collected in different cities in the state of Ceará. The results showed that 39.40%, equivalent to 13 of the samples, were outside the standards established by the current legislation regarding the coliform count at 45°C. Regarding the analysis of Salmonella spp. all samples showed absence of the microorganism. La calidad de la leche está directamente relacionada con un número reducido de microorganismos en deterioro, bajo recuento de células somáticas y ausencia de patógenos. Por tanto, el objetivo de este estudio fue evaluar la calidad microbiológica de la leche pasteurizada tipo C, comercializada en la región de Cariri, en el estado de Ceará. Se determinó el Número Más Probable (NMP) de Coliformes a 45 ° C y la presencia de Salmonella spp, de acuerdo con los límites establecidos por la Resolución de la Junta Colegiada (RCD) número 12, 02/2001. Se recolectaron 33 muestras de leche pasteurizada tipo C que se venden en establecimientos comerciales, incluidos supermercados y panaderías, en diferentes ciudades del estado de Ceará. Los resultados arrojaron que el 39,40%, equivalente a 13 de las muestras, se encontraba fuera de los estándares establecidos por la legislación vigente en cuanto al recuento de coliformes a 45 ° C. En cuanto al análisis de Salmonella spp. todas las muestras mostraron ausencia del microorganismo. A qualidade do leite está diretamente ligada a um número reduzido de microrganismos em deterioração, baixa contagem de células somáticas e ausência de patógenos. Portanto, o objetivo deste estudo foi avaliar a qualidade microbiológica do leite pasteurizado tipo C, comercializado na região do Cariri, estado do Ceará. Foram determinados o Número Mais Provável (NMP) de Coliformes a 45 ° C e a presença de Salmonella spp, de acordo com os limites estabelecidos pela Resolução da Diretoria Colegiada (RCD) nº 12, de 02/2001. 33 amostras de leite pasteurizado tipo C vendidas em estabelecimentos comerciais, incluindo supermercados e padarias, foram coletadas em diferentes cidades do estado do Ceará. Os resultados mostraram que 39,40%, o equivalente a 13 das amostras, estavam fora dos padrões estabelecidos pela legislação em vigor para a contagem de coliformes a 45 ° C. Em relação à análise de Salmonella spp. todas as amostras apresentaram ausência do microrganismo.

Simple Summary There is a lack of knowledge about the impact that phages present in the environment may have against certain Salmonella serovars. Thus, an improved understanding of Salmonella phage diversity will provide a better insight into the role of phages in Salmonella ecology and diversity. The results of this study showed that the poultry farm environment could represent a valuable source of Salmonella phages, which are more varied in broiler than in layer farms. Abstract The exploration of novel nonantibiotic interventions in the field, such as the use of bacteriophages, is necessary to avoid the presence of Salmonella. Bacteriophages are a group of viruses widely distributed in nature, strictly associated with the prokaryotic cell. Researchers have demonstrated the success of phage therapy in reducing Salmonella counts in poultry products. However, the impact that phage concentration in the environment may have against certain Salmonella serovars is not well understood. Therefore, the aim of this study was to assess Salmonella phage prevalence in commercial poultry farms in terms of the production type: layers or broilers. The most prevalent Salmonella serovars isolated in poultry production were used for phage isolation. Salmonella specific phages were isolated from 141 layer and broiler farms located in the Valencia region during 2019. Analysis of the samples revealed that 100% presented Salmonella phages, the most prevalent being against serovar S. Enteritidis (93%), followed by S. Virchow (59%), S. Typhimurium (55%), S. Infantis (52%) and S. Ohio (51%). These results indicate that poultry farms could represent an important source of Salmonella phages. Nevertheless, further studies are needed to assess the epidemiology of phages against other serovars present in other countries and their diversity from the point of view of molecular studies.

BackgroundThe microbiota of broiler chicken gut affects positively or negatively the health, metabolism and immunity of chickens thus it has a significant impact on the animal productivity. Phages, host-specific parasites of bacterial cells, are a promising antimicrobial alternative that selectively target pathogens without disturbing the microbiota. The aim of the study is further characterizing the behaviour of phages and its effect on the commensal microbial community.MethodsWe used 16S rRNA gene amplicon sequencing to evaluate the effect of SalmoFree® (a phage cocktail against Salmonella) on the microbiota of the cecum of broilers reared in a commercial farming system. Two field trials were carried out including 2 control and 2 experimental houses. Phages were incorporated in the broilers’ drinking water using three doses at the grower stage. The core microbiome, differentially abundant taxa between treatments as well as taxa associated with age were identified using Qiime2 and the R-Project for statistics.ResultsAnalyses of similarities among communities over time allowed us to identify two stages of microbiota development at the last stage of the production cycle. The core microbiome identified some key species in the adaptation of the microbiota at the last stage of the cycle. Among these there are important degraders of complex polysaccharides and producers of short chain fatty acids such as Eisenbergiella and Lachnoclostridium. Additionally, the phage cocktail did not affect the normal development of the microbiota structure while its application contributes to reduce the presence of pathogenic Enterobacteria including Salmonella. The addition of the phage cocktail led to a significant reduction in the abundance of Campylobacter and Helicobacter and increase in Butyricimonas and Rikenellaceae abundance which are common inhabitants of the chicken gut with known negative and positive effects in the health, respectively.ConclusionsOur results suggest that phages can contribute to improve the chicken health and reduce pathogens burden at the end of the production cycle of broilers. Furthermore, it presents for the first time a detailed look of the microbiota composition and changes in broilers in a commercial scenario, information that will valuable towards the implementation of phage therapy technologies in the field.

Salmonella, one of the most common food-borne pathogens, is a significant public health and economic burden worldwide. Lytic phages are viable alternatives to conventional technologies for pathogen biocontrol in food products. In this study, 40 Salmonella phages were isolated from environmentally sourced water samples. We characterized the lytic range against Salmonella and among all isolates, phage LPST94 showed the broadest lytic spectrum and the highest lytic activity. Electron microscopy and genome sequencing indicated that LPST94 belongs to the Ackermannviridae family. Further studies showed this phage is robust, tolerating a wide range of pH (4&ndash, 12) and temperature (30&ndash, 60 &deg, C) over 60 min. The efficacy of phage LPST94 as a biological control agent was evaluated in various food products (milk, apple juice, chicken breast, and lettuce) inoculated with non-typhoidal Salmonella species at different temperatures. Interestingly, the anti-Salmonella efficacy of phage LPST94 was greater at 4 &deg, C than 25 &deg, C, although the efficacy varied between different food models. Adding phage LPST94 to Salmonella inoculated milk decreased the Salmonella count by 3 log10 CFU/mL at 4 &deg, C and 0.84 to 2.56 log10 CFU/mL at 25 &deg, C using an MOI of 1000 and 10000, respectively. In apple juice, chicken breast, and lettuce, the Salmonella count was decreased by 3 log10 CFU/mL at both 4 &deg, C and 25 &deg, C after applying phage LPST94 at an MOI of 1000 and 10,000, within a timescale of 48 h. The findings demonstrated that phage LPST94 is a promising candidate for biological control agents against pathogenic Salmonella and has the potential to be applied across different food matrices.

Aims The aims of this study were to isolate and characterize novel Salmonella phages and to evaluate the effectiveness of phage cocktails used as antibacterial agents in dishwashing materials. Methods and results The effective phages, vB_STy-RN5i1 and vB_STy-RN29, were isolated from drain water samples collected from open markets using Salmonella Typhimurium as the host strain. These phages were identified as members of Podoviridae and Siphoviridae, respectively. Both phages infected at least six Salmonella serovars and rapidly lysed their host within one hour. They were stable at 4-45°C and at pH 6-9 for at least an hour while being evaluated in this study. The phage application results indicated that bacterial cells were reduced by 3⋅1 and 2⋅7 log CFU per ml at room temperature when they encountered the phage cocktail on scouring pads (SPs) and dishwashing sponges (DSs), respectively. Conclusions The isolated Salmonella phages, vB_STy-RN5i1 and vB_STy-RN29, had potential against Salm. Typhimurium and could reduce the occurrence of bacterial-cross-contamination from dishwashing materials, which have been reported to be a source of bacteria, to other kitchen utensils and food. Significance and impact of the study The successful reduction of bacterial contamination in dishwashing materials by the phage cocktail consisting of vB_STy-RN5i1 and vB_STy-RN29 reveals its potential to be an alternative antimicrobial agent for SPs and DSs.

Bacteriophages that lyse Salmonella enterica are potential tools to target and control Salmonella infections. Investigating the host range of Salmonella phages is a key to understand their impact on bacterial ecology, coevolution and inform their use in intervention strategies. Virus–host infection networks have been used to characterize the “predator–prey” interactions between phages and bacteria and provide insights into host range and specificity. Here, we characterize the target-range and infection profiles of 13 Salmonella phage clones against a diverse set of 141 Salmonella strains. The environmental source and taxonomy contributed to the observed infection profiles, and genetically proximal phages shared similar infection profiles. Using in vitro infection data, we analyzed the structure of the Salmonella phage–bacteria infection network. The network has a non-random nested organization and weak modularity suggesting a gradient of target-range from generalist to specialist species with nested subsets, which are also observed within and across the different phage infection profile groups. Our results have implications for our understanding of the coevolutionary mechanisms shaping the ecological interactions between Salmonella phages and their bacterial hosts and can inform strategies for targeting Salmonella enterica with specific phage preparations.

Salmonella enterica associated with consumption of cucumbers ( Cucumis sativus ) has led to foodborne outbreaks in the United States. Whole and fresh-cut cucumbers are susceptible to S. enterica contamination during growing, harvesting, and postharvest handling. The application of lytic bacteriophages specific for S. enterica was evaluated to reduce Salmonella populations on cucumbers. Unwaxed cucumbers ('Lisboa' variety, or mini-cucumbers purchased at retail) were inoculated with Salmonella Newport (5 log CFU per cucumber) and were sprayed with 3.2 mL of phosphate-buffered saline (control) or 10 log PFU/ml of SalmoFresh, a Salmonella-specific bacteriophage preparation (phage), to deliver 4.76 × 10

Salmonella enterica serovar Enteritidis and Salmonella enterica serovar Typhimurium are major foodborne pathogens of concern worldwide. Bacteriophage applications have gained more interest for biocontrol in foods. This study isolated 36 Salmonella phages from several animal farms in Thailand and tested them on 47 Salmonella strains from several sources, including farms, seafood processing plant and humans in Thailand and USA. Phages were classified into three major groups. The estimated phage genome size showed the range from 50 &plusmn, 2 to 200 &plusmn, 2 kb. An effective phage cocktail consisting of three phages was developed. Approximately 4 log CFU/mL of S. Enteritidis and S. Typhimurium could be reduced. These phages revealed a burst size of up to 97.7 on S. Enteritidis and 173.7 PFU/cell on S. Typhimurium. Our phage cocktail could decrease S. Enteritidis on chicken meat and sunflower sprouts by 0.66 log CFU/cm2 and 1.27 log CFU/g, respectively. S. Typhimurium on chicken meat and sunflower sprouts were decreased by 1.73 log CFU/cm2 and 1.17 log CFU/g, respectively. Overall, animal farms in Thailand provided high abundance and diversity of Salmonella phages with the lysis ability on Salmonella hosts from various environments and continents. A developed phage cocktail suggests a potential biocontrol against Salmonella in fresh foods.

Prevalence of Salmonella in slaughter sheep and cattle was determined by International Organization for Standardization Method 6579 (ISO) and Vitek Immunodiagnostic Assay System UP Salmonella Phage Technology (VIDAS UP Salmonella SPT—VIDAS UP). A total of 400 healthy slaughter sheep (n = 200) and cattle (n = 200) carcass (C), fecal content (FC), mesenteric lymph node (MLN), liver (L), kidney (K), spleen (S) and gall bladder (GB) were randomly sampled and analysed. ISO and VIDAS UP results indicated 13 (3.25%) and 17 (4.25%) of 400 animals carried Salmonella, respectively, regardless of sample type. There was no isolation from L, S, GB, while 2 C (0.5%), 6 FC (1.5%), 7 MLN (1.75%), 3 K (0.75%) were contaminated with Salmonella. S. Typhimurium (27.8%), S. Enteritidis (22.2%), S. Newport (22.2%) were the three dominant serovars, followed by S. Kentucky (11.1%), S. Umbilo (5.6%), S. Corvallis (5.6%), and S. Albany (5.6%). Overall prevalence in 2800 samples was 0.46% by ISO and 0.61% by VIDAS UP. High relative trueness (RT: 99.79%) of VIDAS UP with a substantial agreement to ISO (? value: 0.80) indicated its efficiency to accompany ISO to monitor Salmonella in slaughter animals. As the first report to evaluate ISO and VIDAS UP in detecting Salmonella from slaughter sheep and cattle, this current prevalence signifies a risk for public health in red-meat and related products in Turkey. © 2019, Association of Food Scientists & Technologists (India). OUAP(V)-2013/29 This project was funded in part by the Bursa Uludag University Scientific Research Unit Grant, Project No: OUAP(V)-2013/29.

In this issue of Structure, Dunne et al. (2018) unveil the architecture of Salmonella phage S16 adhesin. The structure unravels a beads-on-a-string topology consisting of three domains of which the C-terminal glycine-rich PGII domain, located at the distal tip of the long tail fiber, mediates cell surface attachment and host recognition.

Coliphages T7M and T3, Yersinia phage ϕYeO3-12, and Salmonella phage ϕSG-JL2 share high homology in genomic sequences. Simple sequence repeats (SSRs) are found in their genomes and variations of SSRs among these phages are observed. Analyses on regions of sequences in T7M and T3 genomes that are likely derived from phage recombination, as well as the counterparts in ϕYeO3-12 and ϕSG-JL2, have been discussed by Lin in “Simple sequence repeat variations expedite phage divergence: mechanisms of indels and gene mutations” [1]. These regions are referred to as recombinant regions. The focus here is on SSRs in the whole genome and regions of sequences outside the recombinant regions, referred to as non-recombinant regions. This article provides SSR counts, relative abundance, relative density, and GC contents in the complete genome and non-recombinant regions of these phages. SSR period sizes and motifs in the non-recombinant regions of phage genomes are plotted. Genomic sequence changes between T7M and T3 due to insertions, deletions, and substitutions are also illustrated. SSRs and nearby sequences of T7M in the non-recombinant regions are compared to the sequences of ϕYeO3-12 and ϕSG-JL2 in the corresponding positions. The sequence variations of SSRs due to vertical evolution are classified into four categories and tabulated: (1) insertion/deletion of SSR units, (2) expansion/contraction of SSRs without alteration of genome length, (3) changes of repeat motifs, and (4) generation/loss of repeats. Keywords: Simple sequence repeats, T7M, Bacteriophage genome, SSR variability classification

Antimicrobial resistance is a problem faced by humanity for quite some time now. Search for an intelligent alterative to antibiotics led the scientific community to join hands with an age old foe of pathogenic bacteria - bacteriophages. The present study elaborates the potential of a previously isolated phage with biocontrol capability, to survive and adsorb in various physicochemical environments . ΦSP-3, a Salmonella specific lytic phage capable of infecting host in nutrient deprived states with an added advantage of high host specificity and absence of virulence genes as previously reported was chosen for the study. Salmonella Enteritidis was used as host. Basic growth parameters like time taken for phage adsorption, optimal multiplicity of infection (MOI) and one step growth curve, were determined, followed by physicochemical characterization. Various parameters studied include temperature, pH, salinity and presence of sugars and CaCl2. 25 minutes of exposure time was required for 100% adsorption and optimal MOI was calculated as one. The latent period and the rise period was 30 minutes each with a subsequent burst size of 60 phages per bacterium. ΦSP-3 could survive upto 70ºC. 1M NaCl was optimal for phage viability while 0.25M favored maximal adsorption. The optimum pH for ΦSP-3 viability and adsorption was 8. Among the sugars,Arabinose was most influential in inactivating ΦSP-3. 100% adsorption was achieved at both 37ºC and at 40ºC. 10mM of CaCl2 to be optimum for ΦSP-3. Thus the present study substantiates the candidature of ΦSP-3 as a sturdy biocontrol agent capable of thriving well in diverse physicochemical environments.

Themarjoram plant is recorded as medicinal one, traditionally recommended as stimulant / tonic , and help to reduce the severity of asthma, indigestion, headache, rheumatism and toothache. Results of this study showed high total count of contaminating bacteria in marjoram plants in non-packed samples collected from eight Egyptian governorates as compared with the pre-packed ones from two local companies. The presence of Bacillus sp. and E. coli, butnot Salmonella sp. are note-worthy. One phage successfully infected Salmonella typhimurium was isolated using plaque assay which produced circular turbid plaques .The electron micrograph of negatively stained preparation indicated that the phage particles have hexagonal head (~80 nm) with short tail (~20 nm), which is classified to family Podoviridae. The biological characterization of the phage isolate is found to be : inactivation point at 62°C for 10 min., longevity in vitro for 72 hrs, dilution end point of 10-3 and stability for 1.5 hrs at pH 7.2.

The use of bacteriophages, instead of antibodies, in the ELISA-based detection of bacterial strains was tested. This procedure appeared to be efficient, and specific strains of Salmonella enterica and Escherichia coli could be detected. The sensitivity of the assay was about 10(5) bacterial cells/well (10(6)/ml), which is comparable with or outperforms other ELISA tests detecting intact bacterial cells without an enrichment step. The specificity of the assay depends on the kind of bacteriophage used. We conclude that the use of bacteriophages in the detection and identification of bacteria by an ELISA-based method can be an alternative to the use of specific antibodies. The advantages of the use of bacteriophages are their environmental abundance (and, thus, a possibility to isolate various phages with different specificities) and the availability of methods for obtaining large amounts of phage lysates, which are simple, rapid, cheap, and easy.

From 24 December to 24 July 2015, 174 cases were reported in a nationwide salmonellosis outbreak in Sweden: 108 cases were connected to a single restaurant. A spice mix, containing dried vegetables from the restaurant tested positive for the outbreak strain. Additional spice mixes with similar content from different suppliers also tested positive. The outbreak investigation suggests there could be a risk of contaminated products being also on the market in other countries.

Salmonella shedding in swine often increases in response to transportation and lairage. We previously demonstrated that such increases can be limited by directly feeding microencapsulated Salmonella bacteriophages. Here we present the genome sequence of vB_SalM_SJ_3, a broader spectrum Viuna-like Salmonella phage used in those studies.

Typing phages for Salmonella and the prophages of their typical propagation strains were analyzed at the DNA level. Most of them belong to the P22 branch of the lambdoid phages. Acquisition of new plating properties of the typing phages by propagation in particular strains can be due to different host specific modifications of the DNA or to recombination events with residing prophages which are reflected by changes in the respective DNA restriction patterns. It is concluded that the actually available set of typing phages is a historically unique combination of strains.

Salmonella phage SPT-1, a member of the Myoviridae family and a relative of phage O1, produces abnormally long tails with coordinate variations of sheath and core length. The length of abnormal tails varies between 140 and 445 nm.

A bacteriophage, EC6, capable of lysing Escherichia coli serotype O157:H7 was isolated and found to be a member of the family Myoviridae . The genomic sequence of phage EC6 was composed of 86,231 bp with a G+C content of 38.9% and is very similar to the sequences of Escherichia phage wV8 and Salmonella phage Felix O1.

A proposed new genus of the family Myoviridae, “rV5-like viruses”, includes two lytic bacteriophages: Escherichia coli O157: H7-specific bacteriophage rV5 and Salmonella phage PVP-SE1. Here, we present basic properties and genomic characterization of a novel rV5-like phage, vB_EcoM_FV3, which infects E. coli K-12-derived laboratory strains and replicates at high temperature (up to 47 °C). The 136,947-bp genome of vB_EcoM_FV3 contains 218 open reading frames and encodes 5 tRNAs. The genomic content and organization of vB_EcoM_FV3 is more similar to that of rV5 than to PVP-SE1, but all three phages share similar morphological characteristics and form a homogeneous phage group.

The occurrence of somatic (F') and male-specific (F') coliphages and Salmonella phages in a variety of environmental water samples was studied using different bacterial hosts. The number of plaque-forming units (pfu) of the different bacteriophages were compared and their resistance pattern to a biological treatment (humus tank) and chlorination was evaluated. The presence of the bacteriophages in shellfish was also studied. The morphology of isolate bacteriophages was examined as well as the visibility of the different plaques formed. Coliphages were found to produce larger and clearer plaques than all other bacteriophages studied. In most of the environmental water samples coliphages outnumbered all other bacteriophages, with the exception of dam water in which higher levels of F' Salmonella phages were detected. The majority of the F' Salmonella phages were shown to be RNA bacteriophages.

Salmonella Enteritidis phage type 6 (PT6) increased dramatically in the United Kingdom during 1997. The sharp rise suggests that PT6 contamination has spread rapidly throughout a basic food commodity; however, the source and food vehicle remain unknown. We present evidence from three outbreaks suggesting a possibile link between PT6 and eggs. Poor documentation of the egg supply network continues to pose problems for public health investigators. Thorough investigation of all future PT6 outbreaks and case-control studies of sporadic infections are needed to confirm the etiology of PT6 infection.

Numerous bacteriophages specific to Salmonella have been isolated or identified as part of host genome sequencing projects. Phylogenetic analysis of the sequenced phages, based on related protein content using CoreGenes, reveals that these viruses fall into five groupings (P27-like, P2-like, lambdoid, P22-like, and T7-like) and three outliers (epsilon15, KS7, and Felix O1). The P27 group is only represented by ST64B; the P2 group contains Fels-2, SopEphi, and PSP3; the lambdoid Salmonella phages include Gifsy-1, Gifsy-2, and Fels-1. The P22-like viruses include epsilon34, ES18, P22, ST104, and ST64T. The only member of the T7-like group is SP6. The properties of each of these phages are discussed, along with their role as agents of genetic exchange and as therapeutic agents and their involvement in phage typing.

Around two thirds of enteric fever cases reported in England and Wales are known to be associated with foreign travel, the majority to India and Pakistan

To understand the interaction between lipopolysaccharide (LPS) and proteins in molecular detail, a molecular genetic approach has been employed, using phage as a model system. The phage epsilon(34) is a Salmonella phage whose tailspike protein (TSP) uses the host LPS as its initial host cell receptor. Previous studies indicated that there was a similarity between the well-studied tail protein of Salmonella phage P22 and the epsilon(34). This study reports the identification of the gene for the epsilon(34) TSP as well as its initial characterization. In addition, some aspects of the structure of the epsilon(34) TSP have been deduced.

Salmonella-spedfic bacteriophages (BP) and competitive exclusion (CE) were used to reduce Salmonella colonization in experimentally infected chickens. A "cocktail" of distinct phage (i.e., phage showing different host ranges and inducing different types of plaques on Salmonella Typhimurium [ST] cultures) was developed. The killing activity of the selected BPs on ST cultures differed significantly, as determined in in vitro killing assays. BPs were administered orally to the chickens several days prior and after ST challenge but not simultaneously. BPs were readily isolated from the feces of the BP-treated chickens approximately 48 hr after administration. A CE product consisting of a defined culture of seven different microbial species was used either alone or in combination with BP treatment. CE was administered orally at hatch. Salmonella counts in intestine, ceca, and a pool of liver/spleen were evaluated in Salmonella-challenged chickens treated with BP or with BP and CE. In both trials 1 and 2, a beneficial effect of the phage treatment on weight gain performance was evident. A reduction in Salmonella counts was detected in cecum and ileum of BP-, CE-, and BP+CE-treated chickens as compared with nontreated birds. In trial 1, BP treatment reduced ST counts to marginal levels in the ileum and reduced counts sixfold in the ceca. A reduction of Salmonella counts with BP, CE, and BP+CE treatments was evident in chickens from trial 2. Both CE and BP treatments showed differences in the reduction of Salmonella counts after challenge between spedmens obtained at days 4 and 14 postchallenge in ceca, liver/spleen, and ileum. The preliminary data presented in this report show that isolation and characterization of Salmonella-specific BP is uncomplicated and feasible on a larger scale. Results indicate a protective effect of both Salmonella-specific BPs and a defined competitive exclusion product against Salmonella colonization of experimentally infected chickens. These results are encouraging for further work on the use of BP as an effective alternative to antibiotics to reduce Salmonella infections in poultry.

The ability of two strains of Salmonella enteritidis PT4 to cross-contaminate from inoculated egg droplets on surfaces onto melon or beef (sterile or non-sterile) was investigated. When the foods were placed on these surfaces where egg droplets were still wet, cross-contamination occurred within 1 s onto every piece of food. It took at least 1 min for all the food pieces to be contaminated when egg droplets had been allowed to dry. Both strains were capable of rapid growth on melon and beef (sterile or non-sterile) at 20 degrees C, but growth rates on beef appeared to be slowed by pre-exposure to either 4 or -18 degrees C.

To probe the organizational structure of the adsorption apparatus of bacteriophage epsilon 15 (E15) using genetic and biochemical methodologyHydroxylamine was used to create nonsense mutants of bacteriophage E15. The mutants were then screened for defects in their adsorption apparatus proteins, initially by measuring the concentrations of free tail spike proteins in lysates of cells that had been infected by the phage mutants under non-permissive growth conditions. Phage strains whose infected cell lysates contained above-average levels of free tail spike protein under non-permissive growth conditions were assumed to contain nonsense mutations in genes coding for adsorption apparatus proteins. These mutants were characterized by classical genetic mapping methods as well as automated sequencing of several of their genes. Finally, sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography were used to examine the protein compositions of the radioactive particles produced when the various mutants were grown on a non-permissive host cell in the presence of (35)S-methionine and co-purified along with E15wt phage on CsCl block gradients.Our results are consistent with gp4 forming the portal ring structure of E15. In addition, they show that proteins gp15 and gp17 likely comprise the central tube portion of the E15 adsorption apparatus, with gp17 being more distally positioned than gp15 and dependent upon both gp15 and gp16 for its attachment. Finally, our data indicates that tail spike proteins comprised of gp20 can assemble onto nascent virions that contain gp7, gp10, gp4 and packaged DNA, but which lack both gp15 and gp17, thereby forming particles that are of sufficient stability to survive CsCl buoyant density centrifugation.The portal ring (gp4) of E15 is bound to tail spikes (gp20) and the tail tube (gp15 and gp17); gp17's attachment requires both gp15 and gp16.

Somatic salmonella (SS) phages were commonly found in higher numbers than F-specific RNA (FRNA) coliphages in a multi-site survey of contamination-vulnerable groundwaters. The relative abundance of SS phages required that a pretreatment procedure be implemented to reduce the SS phage content of samples before FRNA coliphage assay with Salmonella typhimurium WG49. Pretreatment involved selective SS phage removal by Salm. typhimurium WG45 cells. This pretreatment proved effective in producing interference-free samples throughout the one-year survey period and in seeded evaluation, was shown not to affect the detection of representative FRNA coliphage MS2. During the survey, 30 groundwater sites located in the continental United States, Puerto Rico and the Virgin Islands were examined for FRNA coliphages and SS phages at monthly intervals. FRNA coliphages were detected at six of the 30 sites and in 33 of 329 monthly samples. SS phages were also detected at six sites and in 28 of 329 monthly samples. Five of the phage-positive sites were positive for both phage groups. At those five sites, 58 monthly samples were collected during the survey period. Those 58 samples yielded an average FRNA coliphage concentration of 140 pfu per 100 l of groundwater as compared to an average SS phage concentration of 565 pfu per 100 l of groundwater. Twenty of the 58 samples were positive for both the FRNA coliphages and SS phages. In those samples, FRNA coliphages were more abundant in five samples; SS phages were more abundant in 15 samples. Because these results demonstrate that SS phage levels may often exceed FRNA coliphage levels in environmental waters, it is clear that SS phage removal procedures will greatly enhance the effectiveness of the WG49-based FRNA coliphage assay.

BACTERIAL TRANSFORMA nON ......... 48 BACTERIAL CONJUGATION . ....... ... . .... ... ..... 53 GENERALIZED TRANSDUCTION 54 BACTERIOPHAGE RECOMBINATION .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 CONCLUSION 62