Source Of Human Salmonellosis Research Articles

Application of Acidulants to Control Salmonella spp. in Rendered Animal Fats and Oils with Different Levels of Unsaturation.

Salmonella-contaminated pet foods could potentially become a source of human salmonellosis. This study evaluated the survival of Salmonella without and with the addition of acidulants in different fat types (chicken fat (CF), canola oil (CO), Menhaden fish oil (FO), lard (La), and tallow (Ta)) commonly used to coat dry pet food kibbles. The minimum inhibitory concentration (MIC) of individual acidulants and the combination were determined using the broth microdilution method. Autoclave-sterilized rendered fats were treated with pre-determined concentrations of antimicrobial acidulants (0.5% sodium bisulfate (SBS), 0.5% phosphoric acid (PA), 0.25% lactic acid (LA), etc.) and incubated overnight at 45 °C. The treated fats were inoculated with approximately eight logs of a Salmonella cocktail. Microbiological analyses were conducted separately for the fat-phase and water-phase at predetermined time intervals (0, 2, 6, 12, and 24 h) by plating them onto TSA plates. After incubating at 37 °C for 24 h, the plate count results were expressed as log CFU/mL. The MIC of SBS was 0.3125%, and of PA and LA were both 0.1953% against cocktail Salmonella serotypes. We observed a possible synergistic effect when SBS and organic acid were combined. All the acidulant tested at targeted concentrations individually as well as in combination with organic acids were highly effective against Salmonella spp. (non-detectable within 2 h) across different fat types. A potent anti-bactericidal effect leading to non-detectable Salmonella immediately (<1 h) at 45 °C was observed in the aqueous phase of the fish oil system, even without the addition of acidulants. These findings are significant for the dry pet food industries, where potential post-processing contamination of Salmonella could be controlled by treating fats and oils with acidulants.

Serotype Diversity and Antimicrobial Resistance Profile of Salmonella enterica Isolates From Freshwater Turtles Sold for Human Consumption in Wet Markets in Hong Kong

Chelonians are recognized as a source of human salmonellosis through direct contact or consumption of their meat. Freshwater turtles sold for food are widely available in wet markets in Asia. In this pilot study, 50 turtles belonging to three species were randomly sampled from wet markets throughout Hong Kong. The turtles were humanely euthanised and their feces or the colon were sampled for Salmonella culture. The Salmonella isolates obtained were serotyped and examined for phenotypic antimicrobial resistance and the presence of antimicrobial resistance genes. The study reports a high prevalence (42%, 95% CI: 29.4–55.8) and considerable serotype diversity of Salmonella among turtles sold in wet markets. The most common among the 11 serotypes isolated were S. Oranienburg and S. Thompson, which have been reported in turtles previously. The serotype S. Manhattan is reported in chelonians for the first time. Resistance to streptomycin and chloramphenicol was common, despite the latter being banned from aquaculture in mainland China since 2002. Resistance against fluoroquinolones and third-generation cephalosporins which represent first-line treatment options for salmonellosis was also observed. The multidrug-resistance gene cfr is identified for the first time in Salmonella. This is a worrying finding as it indicates an expansion of the cfr reservoir and potential horizontal spread to other bacteria. The results of this study emphasize the need for close surveillance of Salmonella from turtles sold as food and better regulation of turtle farming to safeguard public health and improve animal welfare.

Аgglutination test and passive hemagglutination test as immunological methods of antigenisisty assessment of vaccines against poultry salmonellosis

Salmonellosis ranks first among acute intestinal infections with an established pathogen in Ukraine. Poultry products are the most frequent source of human salmonellosis is the highest in both the world and Ukraine. Therefore, Salmonella-specific prevention measures in most countries are an issue of great importance. The study's goal was to compare the levels of antibodies against Salmonella to the enteritidis, Typhimurium, and infantis monoantigens in the serum of poultry immunized with the experimental bivalent, the trivalent vaccine against salmonellosis using the Agglutination test (AT) and Passive Hemagglutination test (PHA). The research of two Salmonella inactivated emulsified vaccines – bivalent (S. enteritidis) and trivalent (S. enteritidis, S. typhimurium and S. infantis) was conducted on one of the poultry farms of the Lviv region. The birds were vaccinated two times in the 14th day's interval. The sera samples were taken on the 14, 21, and 28th days after the last shot. The antibody (agglutinin) levels were assessed in the AT and PHA. Both vaccines (bivalent and trivalent) inducted an intense immune response in birds' organisms. The average antibody titers were 1 : 512 –1 : 717 using the AT and 1 : 4096 – 1 : 5734 using the PHA. The highest antibody levels were detected for S. Enteritidis: 1 : 5734 for trivalent vaccine and 1 : 5120 for bivalent one using PHA. AT antibody levels were lower: 1 : 717 for the trivalent vaccine and 1 : 640 for the bivalent. The antibody levels to S. typhimurium were: 1 : 4915 for trivalent vaccine and 1 : 4710 for bivalent (PHA) and 1 : 640 for trivalent vaccine 1 : 589 for bivalent on (AT). The lowest antibody levels were detected in S. Infantis in both tests. An interesting fact of S. infantis agglutinins presence in serum samples from poultry vaccinated with the bivalent vaccine in both tests may be explained by cross-immunity formed by S. enteritidis – S. typhimurium vaccine.

In vitro invasiveness and antimicrobial resistance of Salmonella enterica subspecies isolated from wild and captive reptiles.

Reptiles are carriers of Salmonella and can intermittently shed bacteria in their faeces. Contact with snakes and lizards is a source of human salmonellosis. Here, two populations of reptiles, wild and captive were surveyed for Salmonella. One hundred thirty wild-caught reptiles were sampled for Salmonella including 2 turtle, 9 snake and 31 lizard species. Fifty-two of 130 (40%) animals were Salmonella positive: one of 5 (20%) turtles, 7 of 14 (50%) snakes and 44 of 111 (39.6%) lizards. One hundred twenty-two reptiles were sampled from a zoo collection including 1 turtle, 6 tortoise, 9 lizard, 14 snake and 1 crocodile species. Forty-two of 122 (34.4%) captive reptiles sampled were Salmonella positive. Salmonella was most commonly isolated from lizards and snakes. Fifteen serotypes were identified from zoo and 19 from wild-caught reptiles and most were members of subspecies enterica (I), salamae (II), arizonae (IIIa) or diarizonae (IIIb). Antimicrobial susceptibility testing was conducted on all Salmonella isolates; only two exhibited resistance, a Salmonella subsp. (II) ser. 21:z10 :z6 (Wandsbek) isolate cultured from a wild-caught reptile and a Salmonella Typhimurium DT120 isolated from a captive snake. The invasive capacity of reptile-associated Salmonella strains into cultured human intestinal epithelial (Caco2) and mouse macrophages cell lines (J774A.1) was also investigated. All isolates were invasive into both cell lines. Significant (P 0.001) variability in invasiveness into polarized Caco2 cells was observed. Salmonella Eastbourne exhibited the highest invasiveness into Caco2 cells and Salmonella Chester the lowest, with mean per cent recoveries of 19.99 0.32 and 1.23 0.30, respectively. Invasion into J774A.1 macrophages was also variable but was not significant. Salmonella subsp. II ser. 17:g,t:- (Bleadon) exhibited the highest invasiveness into J774A.1 with a mean per cent recovery of 10.19 0.19. Thus, reptile-associated Salmonellae are likely to have different capacities to cause disease in humans.

Chicken cecal DNA methylome alteration in the response to Salmonella enterica serovar Enteritidis inoculation

BackgroundSalmonella enterica serovar Enteritidis (SE) is one of the pathogenic bacteria, which affects poultry production and poses a severe threat to public health. Chicken meat and eggs are the main sources of human salmonellosis. DNA methylation is involved in regulatory processes including gene expression, chromatin structure and genomic imprinting. To understand the methylation regulation in the response to SE inoculation in chicken, the genome-wide DNA methylation profile following SE inoculation was analyzed through whole-genome bisulfite sequencing in the current study.ResultsThere were 185,362,463 clean reads and 126,098,724 unique reads in the control group, and 180,530,750 clean reads and 126,782,896 unique reads in the inoculated group. The methylation density in the gene body was higher than that in the upstream and downstream regions of the gene. There were 8946 differentially methylated genes (3639 hypo-methylated genes, 5307 hyper-methylated genes) obtained between inoculated and control groups. Methylated genes were mainly enriched in immune-related Gene Ontology (GO) terms and metabolic process terms. Cytokine-cytokine receptor interaction, TGF-beta signaling pathway, FoxO signaling pathway, Wnt signaling pathway and several metabolism-related pathways were significantly enriched. The density of differentially methylated cytosines in miRNAs was the highest. HOX genes were widely methylated.ConclusionsThe genome-wide DNA methylation profile in the response to SE inoculation in chicken was analyzed. SE inoculation promoted the DNA methylation in the chicken cecum and caused methylation alteration in immune- and metabolic- related genes. Wnt signal pathway, miRNAs and HOX gene family may play crucial roles in the methylation regulation of SE inoculation in chicken. The findings herein will deepen the understanding of epigenetic regulation in the response to SE inoculation in chicken.

Prevalence and characterization of Salmonella among humans in Ghana

BackgroundNon-typhoidal Salmonella (NTS) is a public health problem worldwide and particularly in Africa with high disease burden. This study characterized Salmonella isolates from humans in Ghana to determine serovar distribution, phage types, and antimicrobial resistance. Further, the clonal relatedness among isolates was determined.MethodsOne hundred and thirty-seven Salmonella isolates (111 clinical and 26 public toilet) were characterized using standard serotyping, phage typing, and antimicrobial susceptibility testing methods. The molecular epidemiology of common serovars (Salmonella Typhimurium and Salmonella Enteritidis) was established by pulsed field gel electrophoresis (PFGE).ResultsTwenty-two serovars were identified with S. Enteritidis, S. Typhimurium, and Salmonella Derby as the most dominant. One hundred and twelve isolates showed resistance to more than one antimicrobial. Fifty-eight (n = 58/112; 54.5%) strains were multi-resistant with low resistance to cephalosporins ceftazidime (8.0%), cefotaxime (4.5%), and cefoxitin (2.7%) with synergy to clavulanic acid indicating possible ESBLs. Isolates showed high resistance to trimethoprim (66.1%), tetracycline (61.6%), ampicillin (57.1%), sulfamethoxazole (46.4%), chloramphenicol (33.9%), and ciprofloxacin (25.0%). The most common resistance pattern of multi-resistant serovars was to ampicillin, chloramphenicol, sulphonamide, and trimethoprim. S. Enteritidis (18/43) strains reacted with typing phages but did not conform to any phage type with PT14B and PT4 as predominant definitive phage types. Six S. Typhimurium strains reacted but did not conform to any recognized phage type while seven were non-typable. The predominant definitive phage types were DT1 and DT22. PFGE patterns of human S. Enteritidis were closely related to patterns of poultry isolates obtained in a previous study in Ghana.ConclusionsCephalosporin resistance is uncommon among Salmonella from humans in Ghana. Poultry may be an important source of human salmonellosis. There is an urgent need for the implementation of routine surveillance of antimicrobial use and bacterial resistance among humans in Ghana.

Turtle-Associated Salmonellosis, United States, 2006-2014.

During 2006-2014, a total of 15 multistate outbreaks of turtle-associated salmonellosis in humans were reported in the United States. Exposure to small pet turtles has long been recognized as a source of human salmonellosis. The risk to public health has persisted and may be increasing. Turtles are a popular reptilian pet among children, and numerous risky behaviors for the zoonotic transmission of Salmonella bacteria to children have been reported in recent outbreaks. Despite a long-standing federal ban against the sale and distribution of turtles <4 in (<10.16 cm) long, these small reptiles can be readily acquired through multiple venues and continue to be the main source of turtle-associated salmonellosis in children. Enhanced efforts are needed to minimize the disease risk associated with small turtle exposure. Prevention will require novel partnerships and a comprehensive One Health approach involving human, animal, and environmental health.

Identification of risk factors for Salmonella spp. in pigs and control measures during management and transport of animals

Pigs and pork meat products are common source of human salmonellosis. Salmonella can enter the food chain at any point such as the livestock feed, via the on-farm production site, at the slaughterhouse or packing plant, as well as during manufacturing, processing and retailing of food, or through catering and food preparation at home. The understanding of epidemiology of Salmonella sp. at all stages of production chain is of crucial importance. The production of ?Salmonella free pigs? would reduce the risk for the occurrence of human infections Also, production of ?Salmonella free pigs? is difficult to achieve due to a number of practical and financial reasons. However, serological status of particular pig farm can be determined based on the analysis of blood- or meat juice samples taken from slaughtered pigs. This procedure enables the identification of Salmonella free farms?. The basic actions for preventing salmonellosis in humans should involve the following: preventing the entrance of Salmonella to the farm, reducing the number of infected animals and preventing the spread of the infection. The best way to prevent the disease is to keep the infection away from the farm. In order to successfully resolve the problem of human salmonellosis associated with infected pork meat or meat products, control measures need to be simultaneously implemented at all levels of meat production chain.

Epidemiological Evidence That Garden Birds Are a Source of Human Salmonellosis in England and Wales

The importance of wild bird populations as a reservoir of zoonotic pathogens is well established. Salmonellosis is a frequently diagnosed infectious cause of mortality of garden birds in England and Wales, predominantly caused by Salmonella enterica subspecies enterica serovar Typhimurium definitive phage types 40, 56(v) and 160. In Britain, these phage types are considered highly host-adapted with a high degree of genetic similarity amongst isolates, and in some instances are clonal. Pulsed field gel electrophoresis, however, demonstrated minimal variation amongst matched DT40 and DT56(v) isolates derived from passerine and human incidents of salmonellosis across England in 2000–2007. Also, during the period 1993–2012, similar temporal and spatial trends of infection with these S. Typhimurium phage types occurred in both the British garden bird and human populations; 1.6% of all S. Typhimurium (0.2% of all Salmonella) isolates from humans in England and Wales over the period 2000–2010. These findings support the hypothesis that garden birds act as the primary reservoir of infection for these zoonotic bacteria. Most passerine salmonellosis outbreaks identified occurred at and around feeding stations, which are likely sites of public exposure to sick or dead garden birds and their faeces. We, therefore, advise the public to practise routine personal hygiene measures when feeding wild birds and especially when handling sick wild birds.

Subtype analysis of Salmonella isolated from subclinically infected dairy cattle and dairy farm environments reveals the presence of both human- and bovine-associated subtypes

While it is well established that clinically ill livestock represent a reservoir of Salmonella, the importance of subclinical shedders as sources of human salmonellosis is less well defined. The aims of this study were to assess the subtype diversity of Salmonella in healthy dairy cattle and farm environments and to compare the subtypes isolated from these sources with the Salmonella subtypes associated with clinical human cases in the same geographic area. A total of 1349 Salmonella isolates from subclinical dairy cattle and farm environments (46 farms) were initially characterized by traditional or molecular serotyping and tested for antimicrobial susceptibility. A set of 381 representative isolates was selected for further characterization by pulsed-field gel electrophoresis (PFGE); these isolates represented unique combinations of sampling date, serovar, antimicrobial resistance pattern, farm of origin, and source, to avoid overrepresentation of subtypes that were re-isolated from a given source. These 381 isolates represented 26 Salmonella serovars; the most common serovars were Cerro [(38.8%, 148/381) isolated from 21 farms], Kentucky [16.3%; 10 farms], Typhimurium [9.4%; 7 farms], Newport [7.6%; 8 farms], and Anatum [6.3%; 6 farms]. Among the 381 isolates, 90 (23.6%) were resistant to between 1 and 11 antimicrobial agents, representing 50 different antimicrobial resistance patterns. Overall, 61 XbaI-PFGE types were detected among these 381 isolates, indicating considerable Salmonella diversity on dairy farms. Fourteen PFGE types, representing 12 serovars, exactly matched PFGE types from human isolates, suggesting that subclinically infected dairy cattle could be sources of human disease-associated Salmonella.

Molecular characterization showed limited genetic diversity among Salmonella Enteritidis isolated from humans and animals in Malaysia

Salmonella enterica serovar Enteritidis (S. Enteritidis) is the most common causative agent of non-typhoidal salmonellosis in Malaysia. We aimed to characterize S. Enteritidis isolated from humans and animals by analyzing their antimicrobial resistance profiles and genotypes. A total of 111 strains were characterized using multiple-locus variable-number tandem repeat analysis, pulsed-field gel electrophoresis, and antimicrobial susceptibility testing. Both typing methods revealed that genetically similar S. Enteritidis strains had persisted among human and animal populations within the period of study (2003–2008). Only 39% of the strains were multi-drug resistant (i.e., resistant to 3 or more classes of antimicrobial agents), with a majority (73%) of these in low-risk phase (multiple antibiotic resistant index <0.20). Limited genetic diversity among clinical and zoonotic S. Enteritidis suggested that animals are possible sources of human salmonellosis. The degree of multi-drug resistance among the strains was generally low during the study period.

Perfil de resistência a antimicrobianos, fagotipagem e caracterização molecular de cepas de Salmonella Enteritidis de origem avícola

Salmonella enterica subsp. enterica serovar Enteritidis (SE) is currently responsible for significant losses in the poultry industry with consequences on public health. In the present study, 38 SE isolates from biological material of chicken breeders were characterized using phage typing, antimicrobial resistance profile and pulsed field gel electrophoresis (PFGE). The phage type (PT) 7 and 9 were predominant and 26.3% of the isolates were resistance to nalidixic acid (NAL). The phage typing and analysis of antimicrobial resistance profile showed high discriminatory power (0.85). The PFGE profile of 13 strains with XbaI and SpeI discriminated the SE phage types, as well characterized strains from the same serovar. The results showed the importance to associate different methods for the characterization of SE and suggest that poultry products may have been source of human salmonellosis in the Parana State during the period of study.

Distribution of virulence genes and antimicrobial susceptibility of Salmonella isolated from dogs and chickens in Zambia

The present study was conducted to investigate the distribution of virulence genes and the antimicrobial susceptibility of Salmonella isolated from dogs and chickens. A total of 379 samples were examined with 41 Salmonella isolates being cultured with 18 (7.4%; 95% CI: 4.57-11.6) and 23 (16.9%; 95% CI: 11.2-24.5) isolates from dog and chicken, respectively. On serotyping, the isolates belonged to Group B, C, D and E, while 6 isolates from dog were untypeable. The Polymerase chain reaction (PCR) assay was carried out to detect Salmonella invA, invF and sipC virulence genes. A varying distribution of the targeted virulence genes was observed amongst the isolates. InvA was found in all the 41 strains, invF was found among 3 dog and 10 chicken isolates with sipC being observed among 2 dog and chicken isolates respectively. On antimicrobial susceptibility, dog isolates were susceptible to amoxicillin (100%) and nitrofurantoin (94.4%), whereas chicken isolates showed susceptibility to nitrofurantoin (100%), amoxicillin (95.7%), ampicillin and tetracycline (82.6%). It was concluded that dogs and chickens are important carriers of invasive Salmonella in Zambia with a multiple antimicrobial drug resistance pattern. This may be a potential source of human salmonellosis which is difficult to manage by antibiotic therapy.

Molecular characterization and resistance profile of Salmonella Enteritidis PT4 and PT9 strains isolated in Brazil

A total of 41 Salmonella Enteritidis strains, including phago-types (PTs) PT4 and PT9, were characterized by antimicrobial resistance profiles and PFGE. Of these strains, 34 were isolated from patients and foods, and 7 were of poultry origin. All strains were susceptible to ampicillin, chloramphenicol, cefotaxime, ciprofloxacin and trimethoprim/sulfamethoxazole, and 41.5 % (n = 17) were resistant to nalidixic acid. PFGE analysis using XbaI and SpeI restriction enzymes resulted in X1S1 as the prevalent pattern, which was present in 48.8 % (n = 20) of epidemic strains and in one strain isolated from discarded hatching eggs. Distinct patterns were found for the other strains isolated from poultry (X3S1, X8S8, X11S12, X11S13, X16S1 and X13S15). The S. Enteritidis PT9 strains associated with outbreaks of salmonellosis were highly similar (≥0.90), suggesting clonality. The PFGE genotypes were related to the PTs, and it was possible to differentiate strains isolated from patients with salmonellosis from other strains of non-epidemic origin. The PFGE results suggested that the S. Enteritidis strains of poultry origin were a possible source of human salmonellosis during the study period.

Validation of a real-time polymerase chain reaction assay for the detection ofSalmonella in crops of broiler chickens

Salmonella is one of the frequent causes of bacterial foodborne diseases with major public health impact in industrialized countries. Food-producing animals, in particular poultry, are major sources of human salmonellosis. Salmonella is normally found in the gastrointestinal tract of animals and can contaminate the carcass during the slaughtering process. In poultry, crops are also colonized by this pathogen. Crops are more likely to get ruptured during evisceration and contaminate the carcass and therefore present a health risk to consumers. Reducing Salmonella colonization in crops could decrease carcass contamination and is considered a potential preharvest critical control point in poultry production. Furthermore, rapid and reliable diagnostic methods to detect Salmonella are needed to monitor crop colonization to help ensure food safety. However, detection of Salmonella by bacteriological methods is time consuming and labor intensive and is not suitable for routine screening of a large number of samples. Therefore, this study was undertaken to validate a real-time PCR (RPCR) assay for the detection of Salmonella spp. in crop samples of broiler chickens. In total, 997 crop samples (35 spiked, 962 field) were processed by both RPCR and culture. The RPCR correctly identified all spiked crop samples. Out of 962 field crop samples, 100 tested positive by RPCR and 88 tested positive by culture for Salmonella, giving a sample level prevalence of 10.4 % (95% CI: 8.54 to 12.50%) and 9.1% (95% CI: 7.40 to 11.15%), respectively. The agreement beyond chance between RPCR and culture was 92% (P < 0.001) and 100% (P < 0.001) for field and spiked samples, respectively. Compared with culture, the sensitivity and specificity of RPCR were 98.86 and 98.51% for field samples and 100 and 100% for spiked samples, respectively. Where bacterial speciation is required, only the positive samples would be cultured. Therefore, RPCR can be used as a good screening tool for Salmonella spp. in crops by eliminating the time-consuming and labor-intensive culture of negative samples.

EU-wide baseline studies: achievements and difficulties faced

With the purpose of providing the scientific basis for setting targets for Salmonella in food-producing animals, several EU-wide baseline studies to determine the prevalence of Salmonella have been organised at the European Community level. The studies in laying hens and broilers are completed and reported. The achievements and difficulties faced are the main focus of this paper. The results support that poultry products, and table eggs in particular, are important sources of human salmonellosis in EU. However, they also illustrate that with effective surveillance and control efforts, as implemented in several Member States, the prevalence, and thus the associated human infections, can be reduced significantly.

Prevalence of Salmonella in Grade A Whole Shell Eggs in the Island of Ireland

Following the emergence of Salmonella Enteritidis as a widespread contaminant of eggs and the role of eggs in the transmission of human salmonellosis, control measures were introduced to curb the spread of infection. Two approaches to Salmonella control are currently used by egg producers in Ireland, because Northern Ireland producers, like those in the rest of the United Kingdom, widely adopted a vaccination regime, whereas the Republic of Ireland does not permit vaccination but introduced controls based on routine monitoring for specific Salmonella serovars and subsequent culling of infected flocks. To compare the efficacy of these two approaches and determine the prevalence of salmonellae in eggs produced for retail sale in the island of Ireland, a major survey of approximately 30,000 grade A eggs was undertaken. Egg shells and contents were analyzed separately for salmonellae by procedures based on International Organization for Standardization methodology. The survey yielded only two positive samples, with Salmonella Infantis and Salmonella Montevideo isolated from shells; no egg contents yielded salmonellae. There was no statistically significant difference in the prevalence of salmonellae between eggs produced in Northern Ireland and those from the Republic of Ireland; hence, both regimes appeared to be equally effective in controlling salmonellae. The prevalence was also significantly lower than that found in a recent major United Kingdom survey. Hence, shell eggs produced in the island of Ireland are unlikely to be a source of human salmonellosis.

Detection of Salmonella spp. in Stray Dogs in Bursa Province, Turkey: First Isolation of Salmonella Corvallis from Dogs

The prevalence and antimicrobial sensitivity of Salmonella spp. in stray dogs in Bursa province, Turkey were determined from a total of 82 faecal samples by bacteriological methods. Of the dogs, nine (11%) were positive for salmonellae-carrying. All Salmonella isolates were serotyped as S. Corvallis, and were sensitive to amoxycillin/clavulanic acid, ampicillin, cephalothin, chloramphenicol, enrofloxacin, gentamicin, kanamycin, nalidixic acid, neomycin, oxytetracycline and trimethoprim/sulphamethoxazole, while 66.7% of them were resistant to streptomycin. It was concluded that stray dogs could be an important carrier of salmonellae as well as a source of human salmonellosis in Turkey. Additional studies are needed to clarify the epidemiological relationship between S. Corvallis isolated from dogs and humans with regard to public health. This is the first report on the isolation of S. Corvallis from dogs in the country.

Reptile-associated Salmonellosis in Man, Italy

To the Editor: Reptiles are reservoirs of a wide variety of Salmonella serotypes, including all Salmonella enterica subspecies and S. bongori. In reptiles born in captivity or kept as pets, S. enterica subsp. enterica is frequently isolated (1). Salmonella strains are well adapted to reptiles, and they usually cause asymptomatic infections in such animals, while retaining pathogenicity for warm-blooded animals. For several years, reptiles have been recognized as a source of human salmonellosis. In North America, reptile-associated salmonellosis (RAS) has been reported, particularly in children, the elderly, or immunocompromised persons; severe and fatal infections are described occasionally (2). In contrast, only a limited amount of information on RAS is available in Europe. We report a case of RAS that occurred in an adult man in Italy. A 32-year-old man had symptoms of enteritis. For 2 weeks, he had experienced intermittent watery diarrhea, mild fever, and abdominal pain. He was then treated with ciprofloxacin, and after 15 days of treatment, he recovered from enteritis. A stool sample, collected before treatment, underwent bacteriologic analysis, and Salmonella spp. were identified biochemically (api 20E, bioMerieux, Marcy l'Etoile, France) and by a polymerase chain reaction assay specific for the invA gene of Salmonella spp (3). Since the man was a reptile owner, RAS, rather than a foodborne infection, was initially suspected. He owned several cold-blooded animals; all had been tested for Salmonella spp. (at least 3 times at 2- to 3-week intervals), and results were negative. Three weeks before the onset of enteric symptoms, he acquired a boa (Boa imperator) that was subjected to routine analysis for Salmonella spp. in our laboratories (1). Salmonella spp. were isolated from a cloacal swab of the snake. Subsequently, both the human and reptile Salmonella isolates were characterized as S. enterica serovar Paratyphi B. In addition, both strains were found to be d-tartrate–fermenting (dT+) biovars (4), susceptible to ampicillin, amoxicillin-clavulanic acid, cephalothin, ceftazidime, gentamicin, streptomycin, chloramphenicol, tetracycline, neomycin, nalidixic acid, norfloxacin, and ciprofloxacin and resistant to sulfamethoxazole and co-trimoxazole. By pulsed-field gel electrophoresis analysis of DNA, the strains displayed the same pattern, which suggests a clonal origin (4). The isolates were also assayed for virulence-associated genes. The SopE1 gene was detected in both isolates, and the avrA gene was not detected, which is consistent with an invasive pathovar of S. Paratyphi B (4). Conversely, the spvC, pef, and sef genes were not detected (5). In recent years, a general increase in RAS detection has been observed, which may be the result of the increasing diffusion of reptiles as pets and a better awareness of RAS risk. In the United States, annual reports of RAS cases are published by the Centers for Diseases Control and Prevention (2). In Europe, studies on free-living and captive reptiles have shown a high prevalence of Salmonella spp (1). Nevertheless, national surveillance systems for RAS do not exist, and epidemiologic data are incomplete. Notably, since Sweden became a member of the European Union in 1995, and the import restriction rules for reptiles were removed, a marked increase in RAS was observed in that country (6). As the deregulation of the trade in reptiles is applied, in agreement with the European Union laws, a similar scenario may be projected in other European countries. As is the case for nontyphoid salmonellosis, RAS may be underestimated, especially if patients are not hospitalized. Although a few cases of RAS have been previously reported in children in Italy (7,8), this report provides the first description of RAS in adults. S. Paratyphi B dT+, also known as S. enterica serovar Java, has been isolated in reptiles and tropical fish and has been associated with epidemics of human salmonellosis acquired from food, such as goat milk or chicken (9). The evidence shows that salmonellosis by S. Paratyphi B dT+ apparently occurs more frequently in adults (10), while so-called exotic reptile strains seem to be more prone to causing salmonellosis in children (7,8), which has led to the proposition that S. Paratyphi B dT+ strains may be highly pathogenic. By screening virulence-associated genes, both our isolates were found to be SopE1+ and avrA–, a pattern usually observed in the systemic pathovars of S. Paratyphi B (4) and associated with invasiveness, which suggests a high pathogenic potential. Accordingly, strict preventive sanitation measures should be adopted when handling reptiles (2), and reptiles should be always regarded as a potential source of pathogenic Salmonella strains for humans.

Evaluation of Salmonella surveillance in pigs using a stochastic simulation model

Abstract. Pork is an important source of human Salmonellosis. Therefore efficient Salmonella surveillance programmes are recommended for minimising Salmonella entry into food production. With a stochastic simulation model, a Salmonella control programme (based on meat juice samples) was analysed depending on sample size (30 to 200 animals per finishing farm and year), prevalence in the population (8,13 and 24 %), farm size (400, 1500 and 3000 places per farm), threshold level classifying a farm as positive (20 and 40 %) and sensitivity of the test. The simulation model generates an integrated pig production chain with linkages between the stages farrowing, rearing, fattening and slaughter starting with the purchase of gilts. Salmonella may enter the system via purchase of animals, feedstuffs and other vectors. Crowding effects and pen-to-pen infection were also taken into account. Within each herd a dynamic pattern of Salmonella infection was simulated. The simulation covered a time interval of 24 months. Sensitivity, specificity and the predictive values were used for the evaluation of the different sampling strategies. At the base situation (prevalence 8%, 1500 places per finishing farm, 60 animals sampled per year and a threshold of 40 %) sensitivity was 65.9 and specificity 96.6 %. Increasing the sample size mainly improved the sensitivity (74.2 to 77.0 %). If the prevalence in the population is enhanced, more animals have to be sampled in order to realise the same detection rate. The effect of the farm size was negligible. The pattern of the Salmonella infection within a farm over 24 months demonstrated that a classification of farms supposes a handling time of 12 months.