Salmonella Serotypes Research Articles

Studies on different salmonella serotypes isolated from poultry in different governorates in Egypt

The aim of this study was to isolate Salmonellae from 579 birds (348 chickens, 104 ducks, 30turkeys, 50 quail, 30 pigeons and 17 geese) from 4 Egyptian Governorates. The Samplescollected from internal organs (liver, cecum, spleen and heart) were examined bacteriologicallyand serologically. Sixty-three (10.9%) out of 579 birds were found positive while 516 (89.1%)birds were negative for Salmonella isolation. The number and percentage of positive chickens,ducks, turkeys, quails, pigeons and geese were 43 (12.4%), 10 (9.6%), 3 (10%), 5 (10%), 2(6.7%) and 0 (0%) respectively. In this study, S. Typhimurium, S. Apeyeme, S. Kentucky, S.Daula, S. Newport, S. Tamale, S. Molade, S. Colindale, S. Lexington, S. Bargny, S. Enteritidis,S. Papuana, S. Labadi, S. Santiago, S. Magherafelt, S. Rechovot, S. Takoradi, S. Angers and S.Shubra were isolated from chickens. While S. Inganda, S. Infantis and S. Larochelle wereisolated from ducks but S. Virchow and S. Vejle were isolated from turkeys. S. Shangani and S.Jedburgh were isolated from quails while S. Alfort and S. Wingrove were isolated from pigeonsin this study.

Development of a Salmonella cross-protective vaccine for food animal production systems

Intensive livestock production is associated with increased Salmonella exposure, transmission, animal disease, and contamination of food and water supplies. Modified live Salmonella enterica vaccines that lack a functional DNA adenine methylase (Dam) confer cross-protection to a diversity of salmonellae in experimental models of murine, avian, ovine, and bovine models of salmonellosis. However, the commercial success of any vaccine is dependent upon the therapeutic index, the ratio of safety/efficacy. Herein, secondary virulence-attenuating mutations targeted to genes involved in intracellular and/or systemic survival were introduced into Salmonella dam vaccines to screen for vaccine candidates that were safe in the animal and the environment, while maintaining the capacity to confer cross-protective immunity to pathogenic salmonellae serotypes. Salmonella dam mgtC, dam sifA, and dam spvB vaccine strains exhibited significantly improved vaccine safety as evidenced by the failure to give rise to virulent revertants during the infective process, contrary to the parental Salmonella dam vaccine. Further, these vaccines exhibited a low grade persistence in host tissues that was associated with reduced vaccine shedding, reduced environmental persistence, and induction of cross-protective immunity to pathogenic serotypes derived from infected livestock. These data indicate that Salmonella dam double mutant vaccines are suitable for commercial applications against salmonellosis in livestock production systems. Reducing pre-harvest salmonellae load through vaccination will promote the health and productivity of livestock and reduce contamination of livestock-derived food products, while enhancing overall food safety.

An outbreak of multiple serotypes of salmonella in New Zealand linked to consumption of contaminated tahini imported from Turkey.

A widespread salmonellosis outbreak linked to consumption of hummus made from contaminated tahini imported from Turkey occurred in New Zealand in November 2012. This article summarizes the outbreak detection, investigation, and control. The New Zealand Enteric Reference Laboratory alerted public health units regarding a cluster of 11 persons with Salmonella Montevideo infection identified from different regions of the North Island of New Zealand. A multiagency outbreak investigation commenced to determine the source of illness and prevent further transmission. Salmonellosis is a notifiable disease in New Zealand. Outbreak cases were identified through routine salmonellosis notifications, and interviewed using a standardized questionnaire to identify common exposures. Clinical and food isolates were initially characterized by serotyping and then further typed by pulsed-field gel electrophoresis (PFGE). PFGE profiles were sent to PulseNet and international alerts were posted. The scope of the investigation widened to include persons with either Salmonella Maastricht and Salmonella Mbandaka infection following detection of these serotypes in tahini epidemiologically linked to laboratory-confirmed cases. All three of the tahini-associated serotypes were detected in people who had consumed tahini, and these were found to have PFGE profiles indistinguishable from the tahini isolates. Twenty-seven salmonellosis cases infected with at least one of the three tahini-associated Salmonella serotypes were detected between September 1 and December 31, 2012; of these, 16 (59%) cases (12 with Salmonella Montevideo, 3 with Salmonella Mbandaka, and 1 with Salmonella Maastricht infection) had PFGE patterns indistinguishable from the outbreak profile. The investigation led to a trade withdrawal and consumer recall for tahini sesame paste from the consignment and products containing this tahini. The outbreak ceased following the recall. The importer of the implicated tahini was reminded of his duties as a food importer, including ensuring appropriate product testing. Changes to New Zealand legislation strengthened food safety responsibilities of food importers.

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

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

The Antibiotic Resisting Profile of Salmonella spp Isolated from the Sewage of the Campus of the University of Cocody, Abidjan, Côte d’Ivoire

Background: Recent studies have shown that wastewater is contaminated by salmonella sp., pathogenic antibiotics-resisting bacteria. Using wastewater in periurban agriculture in Abidjan is likely to be the source of food-borne diseases such as salmonellosis. However, what we know about these resistant salmonella spp. in wastewater is limited in the country. Aims: This study aims to establish the susceptibility profile of Salmonella spp., isolated from wastewater to antibiotics and to antimetabolite commonly used by medical Original Research Article International Journal of TROPICAL DISEASE & Health, 4(5): 608-620, 2014 609 practitioners. Study Design: Spatio-temporal variation was taken into account. Place and Duration of Study: The study took place from August 2008 to January 2009 at the main campus of the university of Cocody in Abidjan. Methodology: Sampling was done on a weekly basis. Wastewater samples were collected at four different sewers in the campus area. Salmonella sp was isolated by a standard method of laboratory. The resistance of these isolated species to antibiotics was determined according to the disk diffusion method of Kirby-Baeur. The serotypes of salmonella were identified with the Kauffman-White table Results: Five serotypes of eleven strains, which consist of 4 Hato, 3 Farmsen, 2 Derby, 1 Essen and 1 Ovonmouth, were isolated and tested in order to determine their resistance to antibiotics. Amongst the various classes of antibiotics, high resistance was found to sulfonamid (100%), followed by cefotaxime (46.67%) and tetracycline (9.1%). Ampicillin, amoxicillin and clavulanic acid, gentamicin, kanamycin, amikacin, ciprofloxacine, nalidixic acid and chloramphenicol had a high potentiality: their efficacity in the elimination of the Salmonella sp was proved at a level of 100%. Although the majority of strains tested (85.94%) were eliminated by the antibiotics, the serotypes Derby, Hato and Farmsen showed resistance. Conclusion: The Wastewater in the area of the main campus of the University of Cocody contains the antibiotic-resisting strains of salmonella sp. In spite of the fact that the efficacity of some antibiotics in the elimination of Salmonella sp. is proved, the resistance of these strains to third generation of cephalosporin and sulfamid is worrisome. Further studies should be carried out to determine the effects of this antibiotic-resisting salmonella species on humain health..

Molecular Studies on Salmonella Species Isolated From Chicken

Although many pathogens have recently received considerable attention, Salmonella remains among the leading sources of food-borne illness throughout much of the world. A poultry producer suffers losses due to Salmonella infection of the flock including loss of birds and production time. The present study was carried out to compare between the conventional bacteriological method and pre-enriched PCR assay for detection of Salmonella in chicken swabs samples The culture method can detect Salmonella in 6 samples out of 105 of examined samples under investigation with an incidence of 5.7 %, where by using PCR can detect 7 Salmonella positive samples out of 105 examined samples with an incidence of 6.7 %. Dendrogram or phylogentic tree of 5 isolated salmonella serotypes on RAPD-PCR analysis – PCR pattern similarity. The phylogentic tree was constructed applying UPGMA to matrix of similarity established from the combined data obtained by using three RAPD-PCR primers (1, 2, and primer 5) which give the best discrimination out of the six Primers used in the study. The numbers indicate the percentage of similarity among RAPD-PCR profiles based on pair wise band sharing as compared with the molecular weight of the marker (DNA ladder).. it was found that Salmonella serotypes isolated chickens and environmental samples have different degrees of genetic similarity as follow; S. anatum with S. typhimurium (52 %), S. anatum with S. derby (57 %), S. anatum with S. kentucky ( 62 %), S. anatum with S. enteritidis ( 48 %). S. typhimurium with S. derby ( 67 %), S. typhimurium with S. kentucky ( 43 %), S. typhimurium with S. enteritidis ( 38 %). S. derby with S. kentucky ( 37 %) S. derby with S. enteritidis (33 %). S. kentucky with S. enteritidis (29%). These results indicate that there are a different degrees of polymorphism between the 5 serotypes under investigation from lower degree of genetic similarity between (29%) between S. kentucky and S. enteritidis to higher degree (67 %) between S. typhimurium with S. derby.

English

CONTEXT: Enteric fever prevails to be a considerable health issue worldwide. Ciprofloxacin became the mainstay of its therapy after multidrug resistant salmonellae emerged. Treatment failure was soon recorded with ciprofloxacin, the index being in-vitro resistance to nalidixic acid. Chloramphenicol sensitive strains have resurfaced. Resistance to alternatives- macrolides is cropping up though not documented widely. These variations in addition to the fact that India is witnessing escalating resistance to antibiotics, stress the significance of continual surveillance of salmonellae resistance. INTENT: The study undertaken intends to document the current deviations in the antibiogram of the Salmonella isolates from blood culture, with a perspective of evaluating ciprofloxacin susceptibility and macrolide resistance, further considering, if there is a need to modify the antibiotic strategies for this condition. METHODOLOGY: The isolates from blood cultures from January 2012 to September 2013 obtained using commercial BACTEC 9120 system, sub-cultured and processed for determining salmonellae serotypes were further subjected to drug susceptibility testing for patterning their resistance. MICs to ciprofloxacin of nalidixic acid resistant (NAR) isolates were recognized. RESULTS: Salmonella was isolated from 114 out of 8210 blood culture specimens received. There were 74 Salmonella Typhi isolates, 39 Salmonella Paratyphi A and 1 Salmonella Paratyphi B. Highest resistance of salmonellae (85.96%) was exhibited to nalidixic acid and highest susceptibility (100%) to ceftriaxone. Decreased ciprofloxacin susceptibility-DCS (MIC of 0.125-1μg/ml) was noticed in around 90% of NAR salmonellae. Isolates demonstrated sizable resistance (42.10%) to azithromycin. Only three strains were multidrug resistant. INTERPRETATION AND CONCLUSION: Routine screening of nalidixic acid sensitivity should be encouraged as a means to predict decreased fluoroquinolone susceptibility, thereby preventing therapeutic failure. In order to avert the profound impact of antimicrobial resistance and to define the best possible therapy, periodic monitoring of Salmonella antibiogram is of prime value. The upsurge of occurrence of ciprofloxacin resistance, impending resistance to macrolide- azithromycin, re-emergence of chloramphenicol sensitive strains is of particular concern and necessitates a change towards 'evidence-based' treatment and rationalization of existing empirical therapy of enteric fever shifting the vital focus towards antibiotic recycling.

English

AIM AND OBJECTIVE: The interpretation of the Widal test depends upon the baseline titre among healthy individuals in a particular geographical area. This study was undertaken to determine the baseline Widal titre in apparently healthy individuals in, Hadoti region, Rajasthan. MATERIALS AND METHODS: Blood samples were collected from healthy blood donors (n= 200) who attended blood bank of this institution from May 2012 to August 2012. The Widal tube agglutination test was carried out. 0.5 ml of two fold serially diluted patients' sera (dilutions from 1:20 to 1:160) in 0.9% normal saline was tested by adding an equal amount of antigen. RESULTS: Of the 200 serum samples which were tested, 108 serum samples were positive for agglutinins against Salmonella serotypes (≥ 1:20) and 92 serum samples were negative for agglutinins. Among 54 samples with an anti-O titer (≥ 1:20) , 39 samples had titres of 1:40. Among the 63 samples demonstrating anti-H titres of ≥ 1:20 to salmonella serotype, 48 had a titer of 1:40. For salmonella Paratyphi A and B, anti-H titres of 1:20 were found in 3% and 1.5%, respectively, of all samples tested. CONCLUSION: We recommended that the significant titre of the 'H' agglutinin and the 'O' agglutinin of Salmonella Typhi is ≥ 1: 80. While the significant titre of the 'H' agglutinins of Salmonella Paratyphi A and Salmonella Paratyphi B is ≥ 1: 40.

Association of Three Plasmid-Encoded spv Genes Among Different Salmonella Serotypes Isolated from Different Origins

The virulence plasmid associated Salmonella plasmid virulence (spv) locus is strongly concomitant with strains that cause non typhoid bacteremia. The spv region contains three genes required for the virulence, the positive transcriptional regulator spvR and two structural genes spvB and spvC. The purpose of this study was to investigate the presence of these three genes among salmonella serotypes isolated from different sources. A collection of 60 salmonella serotypes from different sources were used. Polymerase chain reaction was carried out for the presence of these genes using specific primers. The prevalence of spvB, spvC, and spvR genes were 26 (43.3%), 44 (73.3%), and 28 (46.6%), respectively. The findings revealed that the distribution of these genes was dissimilar among these serotypes. Many of the human pathogenic salmonella strains which can be transmitted by animals may have these genes and can be very injurious for public health.

A case of urinary tract infection due to Salmonella enterica serovar Virchow and review of the related literature

Nontyphoid salmonella (NTS) serotypes can cause gastroenteritis, bacteriemia, and focal infections. However, these focal infections, including urinary tract infections (UTI), are occasionally observed; in particular, the presence of several predisposing factors, such as immunodeficiency and structural abnormality in the urinary tract, increase the possibility of the occurrence of infection. We present a case of UTI caused by Salmonella enterica serovar Virchow in an elderly and debilitated patient with benign prostatic hyperplasia (BPH). Administration of appropriate antibiotic treatment resulted in recovery of the patient's clinical course.

Geographical distribution of salmonella infected pig, cattle and sheep herds in Sweden 1993-2010

BackgroundThe Swedish salmonella control programme covers the entire production chain, from feed to food. All salmonella serotypes are notifiable. On average, less than 20 cases of salmonella in food-producing animals are reported every year. In some situations, the cases would be expected to cluster geographically. The aim of this study was to illustrate the geographic distribution of the salmonella cases detected in pigs, cattle and sheep.MethodsData on all herds with pigs, cattle and sheep found to be infected with salmonella during the time period from 1993 to 2010 were obtained from the Swedish Board of Agriculture. Using the ArcGIS software, various maps were produced of infected herds, stratified on animal species as well as salmonella serotype. Based on ocular inspection of all maps, some were collapsed and some used separately. Data were also examined for temporal trends.ResultsNo geographical clustering was observed for ovine or porcine cases. Cattle herds infected with Salmonella Dublin were mainly located in the southeast region and cattle herds infected with Salmonella Typhimurium in the most southern part of the country. Some seasonal variation was seen in cattle, but available data was not sufficient for further analyses.ConclusionsAnalyses of data on salmonella infected herds revealed some spatial and temporal patterns for salmonella in cattle. However, despite using 18 years' of data, the number of infected herds was too low for any useful statistical analyses.

Antimicrobial susceptibility of Salmonella isolates recovered from calves with diarrhoea in Australia

OBJECTIVE To identify the common serotypes and antimicrobial resistance patterns of Salmonella spp. associated with diarrhoea in Australian dairy calves under the age of 6 weeks. DESIGN Cross-sectional study. METHODS Faecal samples were collected from outbreaks of diarrhoea in dairy and dairy beef calves less than 6 weeks old. Samples were screened for Salmonella using standard enrichment culture techniques. The antimicrobial susceptibility to 12 commonly used veterinary and human antimicrobials was assessed using the Kirby-Bauer disk diffusion method and the susceptibility profiles of dairy and dairy beef properties were compared using Fisher's exact test. RESULTS Salmonella ser. Dublin, S. ser. Typhimurium and S. ser. Bovismorbificans were the three most common salmonella serotypes isolated. The majority of properties had one serotype. Most of the Salmonella isolates were not resistant to any of the antimicrobials tested. No resistance was seen to amikacin and nalidixic acid, and only one isolate was resistant to ceftiofur or amoxicillin-clavulanic acid. The most common antimicrobial resistance was to streptomycin, ampicillin or combination sulfonamides. Multi-drug resistance was detected in S. ser. Anatum, S. ser. Bovismorbificans, S. ser. Muenster, S. ser. Newport and S. ser. Typhimurium. Isolates from dairy beef properties were more likely to be resistant to ampicillin, kanamycin, neomycin, sulfamethoxazole/trimethoprim and tetracycline (P < 0.05) and were more likely to exhibit multi-drug resistance. CONCLUSION The prevalence of antimicrobial resistance in Salmonella isolates from dairy calves in Australia is low compared with that reported overseas. From a human health perspective, resistance to antimicrobials used in the treatment of human salmonellosis was infrequent.

Emergence of resistant salmonella spp.; new challenges, new trends.

Salmonella enterica is a common cause of human food borne gastroenteritis and bacteremia worldwide. Salmonellosis is caused by different serotypes of salmonella; humans and animals are generally infected with these bacteria by the consumption of contaminated food products (1–3). Non-typhi salmonella gastroenteritis in contrast to the invasive salmonellosis that requires prompt antibiotic therapy, is usually self-limited (4). According to the WHO license for the treatment of salmonellosis in last decades, increasing usage of antimicrobial agents in clinics and slaughterhouses is becoming a major problem (5). Chloramphenicol, sulfamethoxazole-trimethoprim, and ampicillin were the earliest antibiotics used the treatment of salmonellosis. However, following the development of resistance to the aforementioned drugs, quinolones and cephalosporines are currently in use (6). The usage of quinolones and cephalosporines in the veterinary world as the therapeutic agents or growth factors led to the emergence of highly resistant veterinary Salmonella strains which might transfer into human via the food chain process. This transmission will cause failure in clinical treatment of related diseases (7, 8). Frequency of antimicrobial resistance found among isolates from human is directly linked to their use in animals (9). Evaluation of the results of regional studies especially in the countries with uncontrolled use of antibiotics has revealed a significant increase in the number of resistant strains, principally in animal foods as growth factors or therapeutic agents (10–12). Resistance to the aforementioned antibiotics is either chromosomal or plasmid-encoded. Different molecular mechanisms are responsible for the occurrence of resistance against antibiotics in Salmonella spp. (13). Transmissibility of the plasmid-encoded resistant phenotypes among enteric bacteria within the gastrointestinal tract and environment has resulted to a change in the use of the first-line antibiotics against salmonellosis towards antibiotics with no identified similar resistant mechanisms, i.e., quinolones, as the last choice in treatment strategy. New studies in this context have demonstrated the emergence of great numbers of quinolone resistant serotypes in recent years (6, 14, 15). Studies about the aforementioned bacteria have revealed new mechanism of resistance for this group of antibiotics. Mutation in DNA gyrase A/B, topoisomerase IV and plasmid-mediated resistance due to (Qnr), Aac (6′)-Ib-cr, and QepA efflux genes in both of human and animal isolates are three major types of resistance mechanisms in these bacteria. Transmission of these plasmids from other enteric bacteria and natural selection of chromosomally mutated strains could be responsible for the emergence of this type of resistance (16). On the basis of our findings, regarding the regional screening study of the resistance patterns among different S. enterica serotypes isolated from humans, the highest rates of antibiotic resistance were as follows: nalidixic acid; 45.7%, trimethoprim-sulfamethoxazole; 36.4%, ampicillin 15.5%, chloramphenicol; 14.7%, and cephalothin; 6.2% (11). Similar result was found in another study in Iran (12). Most of these isolates have carried mutations on gyrA gene (14). In a new study in USA, the plasmid harboring quinolon resistant bacteria was identified in all of the plasmid harboring human-derived non-typhi enterica isolates of Salmonella spp. (17). According to the report of National Antimicrobial Resistance Monitoring System (NARMS), the increase in MIC (≥ 32 µg/ml) for nalidixic acid in non typhoidal salmonella as the last-line antibiotic and increase in their resistance rates from 0.9% to 2% during 1997 – 2008 (for human isolates of Salmonella enterica serovar Enteritidis about 1.7% to 6.6%), the need for alternative therapeutic approaches seems necessary (18). It seems foresighted that prescription of new antibiotics in future will not guarantee the successful treatment as a result of present resistance mechanisms in these bacteria. Eradication of bacteria from their animal sources seems to be the best inhibitory manner for emergence of resistant strains among these bacteria. Nowadays usage of probiotics and prebiotics and competitive exclusion (CE) cultures are considered as successful and acceptable treatments strategies. These methods can help us to control colonization and growth of gastrointestinal pathogens (19). Exploitation of the mucosal immune system against these bacteria is another useful strategy. Vaccination of animals with an inactived salmonella ghost or its related DNA-based vaccines is a suitable method to prevent bacterial colonization in these bacteria. In addition, use of preservative food additives will reduce microbial infections (20, 21). However, the elimination of any possible source of infection for Salmonella spp. instead of antibiotic therapy seems to be a well- advised solution for controlling the emergence of more resistant Salmonella serotypes.

An imported enteric fever caused by a quinolone-resistantSalmonella typhi

Recent reports indicate that nalidixic acid susceptibility correlates well with the clinical outcome of patients with Salmonella Typhi infection treated with quinolones. We report a case of enteric fever caused by S Typhi in which the isolate was resistant to nalidixic acid, but showed in vitro susceptibility to ciprofloxacin. Following treatment with ciprofloxacin, the clinical outcome was not satisfactory and the patient had a relapse. However, after using a higher dose of ciprofloxacin, the patient was cured. We recommend that all Salmonella systemic infections resistant to nalidixic acid with in vitro but decreased susceptibility to fluoroquinolones be treated with other antibiotics like third-generation cephalosporins or azithromycin. These patients should be closely followed up and observed for further relapse.

Changing trends in antimicrobial resistance among salmonella serotypes in Southern India

Changing trends in antimicrobial resistance among salmonella serotypes in Southern India

Use of quantitative real-time PCR for the detection of Salmonella spp. in fecal samples from horses at a veterinary teaching hospital

A quantitative real-time (RT)-PCR assay was developed to detect Salmonella spp. in the feces of 911 equine species admitted to a veterinary hospital. Fresh feces and feces enriched for 24h in selenite broth were assessed by conventional culture and by RT-PCR targeting the Salmonella invA gene. The detection limit for the RT-PCR assay was 3 and 10 organisms, respectively, when spiked samples were purified from selenite broth and feces. The analytical specificity was 100% based on the detection of a panel of 40 salmonella serotypes from five serogroups and the lack of cross-reactivity with non-related micro-organisms. Although Salmonella spp. were not cultured from fresh feces, the organism was cultured from 6/911 (0.6%) of broth-enriched samples. The bacterial load in enriched samples varied from 3 to 861,037 salmonella invA gene copies/μL DNA. The RT-PCR assay had an overall relative accuracy of 98%, a relative sensitivity of 100% and a relative specificity of 98%, when compared to conventional culture. The judicious use of such a RT-PCR method has the potential to reduce the risk of nosocomial infections such as salmonellosis through the provision of highly accurate and rapid pathogen detection.

Investigation of Outbreak of Infections Caused by Salmonella Saintpaul

The US Centers for Disease Control and Prevention (CDC) has been working with state, local and tribal health departments, the Indian Health Service, and the Food and Drug Administration (FDA) to investigate a large, multistate outbreak of Salmonella Saintpaul.On May 22, 2008, the New Mexico Department of Health notified CDC of 4 persons who became ill with the outbreak strain of Salmonella Saintpaul and 15 other persons with Salmonella infection whose isolates had not yet been characterized. In the following weeks, cases of illness with the outbreak strain continued to be reported and the outbreak had expanded to include 43 states, the District of Columbia, and Canada. The outbreak now seems to be over. The CDC and its public health partners on the federal, state, local, and tribal levels searched for the source of the outbreak and said it “took steps to stop transmission of the infection.” The investigation involved the cooperation of hundreds of ill and well persons across the country who answered questions about what foods they had recently consumed.According to agency officials, “This allowed investigators to link illness with particular food items. In addition, public health officials in several states, with the assistance of CDC, investigated clusters of ill persons who had eaten at the same restaurants. FDA and state investigators traced the origin of some produce items back through the distribution chain and collected samples to test for the presence of the outbreak strain.“The investigation showed that jalapeño peppers were a major source of contamination and that serrano peppers also were a source. In addition, tomatoes were possibly a source, particularly early in the outbreak. Jalapeño peppers were traced back to distributors in the United States that received produce grown and packed in Mexico. The outbreak strain was isolated from samples of jalapeño peppers collected in a US warehouse and a patient's home and from samples of serrano peppers and water collected on a farm in Mexico.”The CDC and state health departments are continuing to conduct surveillance for cases of infection with the outbreak strain and will continue to analyze data gathered during the investigations (Figure).See “Outbreak of salmonella serotype Saintpaul infections associated with multiple raw produce items—United States, 2008,” MMWR 2008;57;929–934. The US Centers for Disease Control and Prevention (CDC) has been working with state, local and tribal health departments, the Indian Health Service, and the Food and Drug Administration (FDA) to investigate a large, multistate outbreak of Salmonella Saintpaul. On May 22, 2008, the New Mexico Department of Health notified CDC of 4 persons who became ill with the outbreak strain of Salmonella Saintpaul and 15 other persons with Salmonella infection whose isolates had not yet been characterized. In the following weeks, cases of illness with the outbreak strain continued to be reported and the outbreak had expanded to include 43 states, the District of Columbia, and Canada. The outbreak now seems to be over. The CDC and its public health partners on the federal, state, local, and tribal levels searched for the source of the outbreak and said it “took steps to stop transmission of the infection.” The investigation involved the cooperation of hundreds of ill and well persons across the country who answered questions about what foods they had recently consumed. According to agency officials, “This allowed investigators to link illness with particular food items. In addition, public health officials in several states, with the assistance of CDC, investigated clusters of ill persons who had eaten at the same restaurants. FDA and state investigators traced the origin of some produce items back through the distribution chain and collected samples to test for the presence of the outbreak strain. “The investigation showed that jalapeño peppers were a major source of contamination and that serrano peppers also were a source. In addition, tomatoes were possibly a source, particularly early in the outbreak. Jalapeño peppers were traced back to distributors in the United States that received produce grown and packed in Mexico. The outbreak strain was isolated from samples of jalapeño peppers collected in a US warehouse and a patient's home and from samples of serrano peppers and water collected on a farm in Mexico.” The CDC and state health departments are continuing to conduct surveillance for cases of infection with the outbreak strain and will continue to analyze data gathered during the investigations (Figure). See “Outbreak of salmonella serotype Saintpaul infections associated with multiple raw produce items—United States, 2008,” MMWR 2008;57;929–934.

The Key Role of Pulsed-Field Gel Electrophoresis in Investigation of a Large Multiserotype and Multistate Food-Borne Outbreak of Salmonella Infections Centered in Pennsylvania

Five different serotypes of Salmonella enterica were implicated in a large outbreak linked to fresh Roma tomatoes served at gas station deli counters in Pennsylvania and nearby states during July 2004: S. enterica serotypes Javiana, Anatum, Thompson, Typhimurium, and Muenchen. One of these serotypes, Anatum, was isolated from both tomatoes and patients. Pulsed-field gel electrophoresis (PFGE) played a key role in identifying the outbreak-associated isolates and distinguishing them from unrelated sporadic isolates. It also demonstrated that the genetic fingerprints of serotype Anatum isolates derived from patients were indistinguishable from those derived from tomatoes. Rapid communication of PFGE fingerprints with other public health laboratories through the Centers for Disease Control and Prevention's PulseNet USA national molecular surveillance network for bacterial food-borne pathogens facilitated the tracking of this outbreak in other states. The work described in this report emphasizes the laboratory's role in core public health functions and services, thereby providing a highly visible example of public health in action.

Surveillance of human salmonellosis in Bulgaria, 1999-2004: trends, shifts and resistance to antimicrobial agents

This article analyses the distribution of resistant salmonella and resistance mechanisms among the most frequently encountered serotypes in Bulgaria. Culture, biochemical tests and serotyping were used for identification. Screening for resistance to 14 antimicrobial agents with the standard Bauer-Kirbi disk-diffusion method. The double disk synergy method was used to determine production of extended-spectrum a-lactamases (ESBL). Transfer of genes coding for ESBLs with experimental conjugation. Specific primers were used for PCR detection of bla-CTX-M, bla-SHV and bla-TEM. 245 resistant salmonella strains were determined in our study; the majority originated from sporadic cases of human illness or asymptomatic infection and the remaining 23 were isolated from outbreaks. 79 producers of ESBL were detected: 5 S. Enteritidis, 1 S. Typhimurium, 9 S. Isangi and 62 S. Corvallis with types of enzymes: CTX-M3, TEM and SHV. Gene coding for extended-spectrum a- lactamases were successfully transferred into a recipient Escherichia coli C1A strain simultaneously with genes coding for resistance to aminoglycosides and sulphonamides (for bla-CTX-M3) and gene coding for resistance to aminoglycosides and chloramphenicol (for bla-SHVand bla-TEM). PCR amplification revealed bla-CTX-M3 genes in S. Enteritidis, and bla-SHV and bla-TEM in S. Corvallis. Salmonellae have revealed increasing resistance to all clinically important groups of antimicrobial agents. Bulgaria is the first country in the world where ESBL in serotype Corvallis has been reported. A wide diversity of resistance genes is found among the leading serotypes of salmonella causing human disease in Bulgaria.

DNA Sequence-Based Subtyping and Evolutionary Analysis of Selected Salmonella enterica Serotypes

While serotyping and phage typing have been used widely to characterize Salmonella isolates, sensitive subtyping methods that allow for evolutionary analyses are essential for examining Salmonella transmission, ecology, and evolution. A set of 25 Salmonella enterica isolates, representing five clinically relevant serotypes (serotypes Agona, Heidelberg, Schwarzengrund, Typhimurium, and Typhimurium var. Copenhagen) was initially used to develop a multilocus sequence typing (MLST) scheme for Salmonella targeting seven housekeeping and virulence genes (panB, fimA, aceK, mdh, icdA, manB, and spaN). A total of eight MLST types were found among the 25 isolates sequenced. A good correlation between MLST types and Salmonella serotypes was observed; only one serotype Typhimurium var. Copenhagen isolate displayed an MLST type otherwise typical for serotype Typhimurium isolates. Since manB, fimA, and mdh allowed for the highest subtype discrimination among the initial 25 isolates, we chose these three genes to perform DNA sequencing of an additional 41 Salmonella isolates representing a larger diversity of serotypes. This "three-gene sequence typing scheme" allowed discrimination of 25 sequence types (STs) among a total of 66 isolates; STs correlated well with serotypes and allowed within-serotype differentiation for 9 of the 12 serotypes characterized. Phylogenetic analyses showed that serotypes Kentucky and Newport could each be separated into two distinct, statistically well supported evolutionary lineages. Our results show that a three-gene sequence typing scheme allows for accurate serotype prediction and for limited subtype discrimination among clinically relevant serotypes of Salmonella. Three-gene sequence typing also supports the notion that Salmonella serotypes represent both monophyletic and polyphyletic lineages.