Typhimurium Serotypes Research Articles

Assessment of multidrug-resistant profile, multi-locus sequence typing and efflux pump activity in Salmonella Typhimurium isolated from hospital sewage

Salmonella enterica serovar Typhimurium is becoming a leading cause of gastroenteritis and mortality. The use of antibiotics has increased natural resistance of S. Typhimurium to antibiotics. This study aims to isolate and characterize multi-drug-resistant (MDR) Salmonella strains from hospital sewage samples in Bhopal City, central India. The MDR isolates were characterized by molecular identification, antimicrobial resistance patterns, multi-locus sequence typing, and efflux pump activity. Specific genes (hilA, stn, invA, typh, and iroB) were used to confirm S. Typhimurium isolates. The Kirbey-Bauer method was employed to profile antimicrobial resistance using 20 antibiotics. Multi-locus sequence typing confirmed S. Typhimurium using seven housekeeping genes (aroC, dnaN, hemD, hisD, purE, sucA, and thr). Out of five strains, only four were confirmed as S. Typhimurium during MLST analysis. Efflux pump activity was determined using the ethidium bromide (EtBr) cartwheel test. Of the 160 isolates, 38 were presumptively confirmed as S. Typhimurium based on biochemical characterization, and only five MDR Salmonella strains were selected for their resistance against most antibiotics. Efflux pump activity revealed that five out of the four MDR isolates did not retain EtBr inside the cells, indicating pronounced efflux activity. Additionally, the isolated strains showed a specific correlation between the antimicrobial phenotypes and genotypes. The results of this study provide a better understanding of the characterization of S. Typhimurium serotype in Bhopal City. Future studies should focus on understanding changing antimicrobial resistance patterns, pathogenicity, and the genetic background of Salmonella serotypes. Further surveillance activities for antimicrobial-resistant Salmonella in different environmental sources should be prioritized.

Epidemiological and clinicopathological findings in 15 fatal outbreaks of salmonellosis in dairy calves and virulence genes in the causative Salmonella enterica Typhimurium and Dublin strains.

Salmonella enterica is a major food-borne pathogen that affects cattle-rearing systems worldwide. Little information is available on the epidemiology and pathology of salmonellosis and the virulence genes (VGs) carried by Salmonella in spontaneous outbreaks in cattle. We describe epidemiological findings in 15 fatal outbreaks of salmonellosis in Uruguayan dairy farms and the age, clinical signs, and pathology in 20 affected calves. We also describe the serotypes and frequencies of 17 VGs in the causative Salmonella strains and explore their associations with epidemiological, clinical, and pathological findings. Salmonella Typhimurium and Dublin were identified in 11/15 and 4/15 outbreaks, respectively. The most frequent reason for consultation was digestive disease (8 outbreaks caused by S. Typhimurium), followed by sudden death (4 outbreaks, 3 caused by S. Dublin). Morbidity, mortality, and lethality ranged 4.8-100%, 3.8-78.9%, and 10-100%, without significant differences between serotypes. Diarrhea, the most common clinical sign (14 cases), was associated with the Typhimurium serotype (OR = 26.95), especially in ≤ 30-day-old calves with fibrinous enteritis as the main autopsy finding. The Dublin serotype affected ≥ 50-day-old calves and was associated with fibrinosuppurative splenitis (p = 0.01) and tubulointerstitial nephritis (OR = 48.95). The chances of the Dublin serotype increased significantly with age. There was low variability of VG across serotypes. The pefA gene was associated with the Typhimurium serotype (OR = 21.95), macroscopic enteritis (p = 0.03), and microscopic fibrinosuppurative splenitis (p = 0.04). Understanding the epidemiology, pathology, and virulence of S. enterica at the farm level is key to delineating prevention and control strategies to mitigate its impact on animal and human health.

Efficacy of peroxyacetic acid against Salmonella biofilms and as a decontaminant agent in poultry meat

We aimed to investigate the effect of the post-chilling Peroxyacetic Acid (PAA) application on chicken carcasses’ shelf life, PAA treatment on chicken neck skin samples contaminated with S. Enteritidis and S. Typhimurium serotypes, and its activity against single and mixed Salmonella biofilms. Initially, effects of the post-chilling PAA application on chicken carcasses’ shelf life was analyzed. Secondly, the effectiveness of PAA application in chicken neck skin samples which are experimentally contaminated was investigated. Then, biofilm forming capacity of Salmonella enterica serovars were determined, and PAA activity against single and mixed Salmonella biofilms was evaluated. According to the results, in all experimental groups at least 1 log cfu/g reduction was observed on the day of PAA application (0 hour), and we monitored significant decreases of Salmonella counts in all groups after both 100 and 200 ppm PAA treatments within the 6th hour. The combinations of PAA concentrations and duration of application used in the study were insufficient in terms of S. Typhimurium and S. Enteritidis counts in chicken neck skin samples; however, these treatments can be effective on extending the chicken meat’s shelf life. On the other hand, 200 ppm of PAA was effective in reducing S. Typhimurium and S. Enteritidis biofilms. As a mean of 4.8 log/ml reduction were detected against S. Enteritidis and S. Typhimurium biofilms. Moreover, we can conclude from statistical analysis that when biofilm is composed with more than one Salmonella, it is harder to reduce their counts with PAA treatments. However, there is a recommendation of EFSA (European Food Safety Authority) that PAA may be a decontamination agent in poultry production in the future, considering that PAA will not have toxic effects on human health. PAA studies on this subject will be of great importance in the future if it is passed to legislation.

Comparative Genomic Analysis Discloses Differential Distribution of Antibiotic Resistance Determinants between Worldwide Strains of the Emergent ST213 Genotype of Salmonella Typhimurium.

Salmonella enterica constitutes a global public health concern as one of the main etiological agents of human gastroenteritis. The Typhimurium serotype is frequently isolated from human, animal, food, and environmental samples, with its sequence type 19 (ST19) being the most widely distributed around the world as well as the founder genotype. The replacement of the ST19 genotype with the ST213 genotype that has multiple antibiotic resistance (MAR) in human and food samples was first observed in Mexico. The number of available genomes of ST213 strains in public databases indicates its fast worldwide dispersion, but its public health relevance is unknown. A comparative genomic analysis conducted as part of this research identified the presence of 44 genes, 34 plasmids, and five point mutations associated with antibiotic resistance, distributed across 220 genomes of ST213 strains, indicating the MAR phenotype. In general, the grouping pattern in correspondence to the presence/absence of genes/plasmids that confer antibiotic resistance cluster the genomes according to the geographical origin where the strain was isolated. Genetic determinants of antibiotic resistance group the genomes of North America (Canada, Mexico, USA) strains, and suggest a dispersion route to reach the United Kingdom and, from there, the rest of Europe, then Asia and Oceania. The results obtained here highlight the worldwide public health relevance of the ST213 genotype, which contains a great diversity of genetic elements associated with MAR.

Detection and differentiation of Salmonella Enteritidis and Salmonella Typhimurium by multiplex quantitative PCR from different poultry matrices

ABSTRACT 1. The aim of this study was to develop a multiplex quantitative polymerase chain reaction (qPCR) based molecular diagnostic kit for rapid diagnosis of Salmonella enterica serovar Enteritidis and S. enterica serovar Typhimurium serotypes, which are frequently isolated worldwide from poultry samples. 2. Detection and discrimination of S. Enteritidis and S. Typhimurium were performed by targeting the sdf and the STM4492 (putative cytoplasmic protein) gene, respectively. The invA (invasion protein) gene was used to detect Salmonella spp. as a target gene, since it is considered a standard. In this study, a total of 200 bacterial strains (178 Salmonella spp. strains and 22 other genera) were used to test the specificity and sensitivity of the developed kit. The limit of detection (LOD) of the assays was determined to be 100–101 cfu/25 g from chicken meat samples artificially contaminated by litter and 100–101 cfu/ml for cloacal swab samples. 3. The multiplex qPCR results were 100% compatible with conventional serotyping results while the specificity and sensitivity values were 100%. These findings indicated that the newly developed multiplex qPCR technique can provide an alternative method to conventional serotyping of S. Enteritidis and S. Typhimurium in laboratories lacking adequate infrastructure.

Identification of Salmonella spp. strains in poultry products and their impact on Public Health

Introduction. Poultry meat and eggs represent a risk of contamination with zoonotic bacterial agents. This requires permanent laboratory monitoring throughout the production chain segment.
 Material and methods. The research material consisted of samples retrieved from poultry carcasses and eggs for current consumption. There were examined 80 samples of eggs and 110 samples of poultry carcasses.
 Results. S. Gallinarum, S. Enteritidis and S. Infantins serotypes were isolated in 12.7% of samples out of 110 examined carcasses, whereas S. Gallinarum, S. Dublin și S. Typhimurium serotypes were detected in 6.25% of 80 egg samples.
 Conclusions. Bacteriological research on poultry carcasses and eggs showed the presence of pathogenic serotypes of Salmonella spp., which is a major risk to public health.

Non-typhoidal Salmonella intestinal carriage in a Schistosoma mansoni endemic community in a rural area of the Democratic Republic of Congo.

BackgroundClinical observations and animal studies have suggested that Salmonella intestinal carriage is promoted by concurrent Schistosoma infection. The present study assessed association of Salmonella intestinal carriage and Schistosoma mansoni infection among individuals in a Schistosoma endemic area in sub-Saharan Africa.MethodsFrom November 2015 to March 2016, a cross-sectional community-wide study was conducted in Kifua II, a rural village in Kongo Central Province, Democratic Republic of Congo. Stool samples were collected and analyzed for Salmonella intestinal carriage (culture) and Schistosoma mansoni infection (Kato Katz microscopy with determination of egg load). Salmonella Typhimurium and Enteritidis isolates were assessed for genetic similarity with blood culture isolates obtained during the same period in a neighboring hospital using multi-locus variable-numbers tandem repeat analysis (MLVA).ResultsA total of 1,108 participants were included (median age 15 years (IQR: 7–36), male-to-female ratio of 1:1.1). The overall prevalence of Schistosoma mansoni infection and non-typhoidal Salmonella carriage was 51.2% (95% CI: 48.2–54.1) and 3.4% (95% CI: 2.5–4.7) respectively, with 2.2% (95% CI: 1.5–3.2) of participants coinfected. The proportion of Salmonella carriage tended to be higher among Schistosoma mansoni infected participants compared to non-infected participants but this difference did not reach statistical significance (4.2% versus 2.6%, p = 0.132). However, the proportion of Salmonella carriage among participants with a heavy Schistosoma mansoni infection was significantly higher compared to those with a light and moderate infection (8.7% versus 3.2%, p = 0.012) and compared to Schistosoma mansoni negatives (8.7% versus 2.6%, p = 0.002). The 38 Salmonella isolates comprised five and four Enteritidis and Typhimurium serotypes respectively, the majority of them had MLVA types identical or similar to those observed among blood culture isolates.ConclusionSalmonella intestinal carriage was associated with a heavy intensity of Schistosoma mansoni infection. Further studies are needed to address causation.

Comparative study of egg contamination with Salmonella Heidelberg and Salmonella Typhimurium

Cases of salmonellosis in humans have been associated with consumption of eggs contaminated with this bacterial pathogen due to insufficient heat treatment. The most prevalent serotypes of Salmonella in Brazil include serotypes Enteritidis, Typhimurium, and Heidelberg. The first two serotypes are major causes for eggs to be withheld from sale and for recalls over Salmonella contamination concerns in both domestic and foreign markets. Eggs may be contaminated through transovarian infection (transovarial transmission) due to the presence of the microorganism in the hen’s oviduct and bacterial penetration of the eggshell. There is little data in the literature on the susceptibility of egg contamination and eggshell penetration by Brazilian serotypes of Salmonella. The present study aimed to evaluate the ability of S. Heidelberg and S. Typhimurium serotypes to penetrate through the eggshell and detect these bacteria in the albumen and yolk according to the thickness of the eggshell. SPF (specific-pathogen-free) eggs were artificially contaminated by contact with moist cotton containing Salmonella (15 x 108 CFU/ml). Eggs were divided into the following groups: negative control (not contaminated), S. Heidelberg, and S. Typhimurium. Subsequently, these eggs were incubated at 37°C, and their contents analyzed after 4 h and 24 h of incubation. The evaluation (assessment) of the contamination was performed by traditional bacteriology and confirmed by biochemical and serological tests. Treatments were compared with Fisher’s test using a SAS statistical software. For S. Heidelberg, the percentage of positivity (positive cases) was lower in both albumen and yolk at 4 h and 24 h intervals (33.33% and 3.7%, and 3.7% and 3.7%, respectively) compared to S. Typhimurium (26.63% and 7.41%, and 33.33% and 33.33%, respectively). These findings suggest that the former strain (S. Heidelberg) was unable to survive in the hostile environment of the albumen. In contrast, eggshell thickness had no significant correlation with the number of positive samples. In conclusion, the results obtained in the egg infection model show that the Salmonella strains tested were able to penetrate the eggshell and multiply in both the albumen and yolk and that S. Typhimurium proved to be the most efficient to grow within these portions of the egg.

Salmonella Typhimurium in Iran: Contribution of molecular and IS200 PCR methods in variants detection.

Salmonella Typhimurium, a zoonotic pathogen, is regarded as a major health and economic concern worldwide. Recently, monophasic variants of this serovar have been significantly associated with human gastroenteritis outbreaks globally, making its accurate identification essential for epidemiological and control purposes. We have identified and analyzed 150 S. Typhimurium from 884 Salmonella genus isolated from humans, domestic animals, poultry, food items and abattoirs origins. The Salmonella isolates were obtained from Iranian National Veterinary Reference Laboratories of 9 provinces during 2007–2016, and from five hospitals in Tehran in 2015. The isolates were evaluated biochemically, serologically, and by PCR amplification of invA, mdh, STM4492, fliC, fljA, fljB, hin genes, IS200 and DT104. invA and mdh genes were used to confirm the S. Typhimurium serotype, fliC and fljB genes for determination of monophasic variants and amplification of IS200 to discriminate the monophasic variants from the closely related serotypes. We identified 78.6% (118/150) as classical S. Typhimurium (fliC, fljB and IS200 positive), 12.6% (19/150) were IS200 negative from all isolates. DT104 is another marker for S.Typhimurium serovar typing. Contrary to EFSA guidelines 20.6% (19/29) of human isolates that lacked IS200 insertion sequence, were confirmed as S.Typhimurium. Compared to the North American/European isolates the low prevalence of fljB negative 6% (9/150) and the high abundance of fliC negative 23.3% (35/150) isolates also were indicative of a different regional atypical population. Studies have shown that the prevalence of monophasic (fljB-) S. Typhimurium worldwide is promoted by the Swine industry. Thus, one reason for this high number of different atypical strains could be inhibition of swine breeding system (house hold and industry) in Iran. These results demonstrate a need for a modified identifying protocol to overcome the regional differences.

Epidemiology of non‐typhoid Salmonella infection in the Australian Capital Territory over a 10‐year period

To describe the epidemiology of non-typhoid Salmonella (NTS) infection in the Australian Capital Territory (ACT), including factors associated with hospitalisation. This was a retrospective descriptive and observational study of culture-confirmed NTS infections using data collected from ACT public health, public pathology and hospital services in the period 2003-2012. Outcome measures include incidence and NTS serotype for total reported and hospitalised cases and focus of infection, complications and antibiotic susceptibility for hospitalised cases. In total, 1469 cases of NTS infection were reported, with the crude annual incidence increasing from 24.4 to 61.3 cases per 100 000 population; 14% were hospitalised, representing an incidence of 5.9 hospitalisations per 100 000 population, without significant change over time. Hospitalisation incidence peaked at the extremes of age. Comorbid disease and age ≥ 80 years were associated with complications during hospitalisation. Salmonella serotype Typhimurium was the most common serotype, accounting for 64% of NTS. Independent risk factors for invasive disease included non-S. Typhimurium serotype (aRR 5.46, 95%CI 1.69-17.65 P = 0.005), ischaemic heart disease (aRR 4.18, 95%CI 1.20-14.60 P = 0.025) and haematological malignancy (aRR 6.93, 95%CI 2.54-18.94 P < 0.001). Among hospitalised patients, resistance to ampicillin, ceftriaxone, trimethoprim-sulfamethoxazole and quinolones was 9.9%, 0%, 4.4% and 2.5% respectively. NTS notifications in the ACT have increased over time, with outbreaks of food-borne disease contributing to this increase. Crude age-specific incidence is highest in the very young, while rates of hospitalisation are highest in the elderly. Comorbid disease and infection with a non-S. Typhimurium serotype were associated with complicated NTS disease course. Antimicrobial resistance in NTS is low and has not increased over time.

Effect of a mannanoligosaccharide-supplemented diet on intestinal mucosa T lymphocyte populations in chickens challenged withSalmonella Enteritidis

Salmonellosis is one of the most common worldwide zoonosis, and the Enteritidis and Typhimurium serotypes are most prevalent. In this study, we evaluated the effects of a diet supplemented with mannanoligosaccharides (MOS) on CD3+, CD4+, CD8+, and goblet cell counts in the intestines of broilers vaccinated and challenged withSalmonella Enteritidis. The evaluation was based on randomized experiments including 45 chickens divided into 3 experimental groups. Group 1 received a nonsupplemented control diet. Group 2 received a diet supplemented with 1 kg MOS/t from d 1 to 21 and 0.5 kg MOS/t from d 22 to 56. Group 3 received a diet supplemented with 2 kg MOS/t from d 1 to 21 and 1 kg MOS/t from d 22 to 56. Chickens fed the lower level of MOS demonstrated reduced fecal shedding ofSalmonella 14 d after being challenged (P < 0.05). Both groups of MOS-supplemented chickens showed an increase in CD4+ and CD8+ cell counts in the ileal and cecal mucosa after being challenged withSalmonella Enteritidis (SE). Supplementation with MOS increased the specific T lymphocyte infiltration in the intestinal mucosa of chickens vaccinated and challenged withSalmonella Enteritidis.

Molecular characterization of Salmonella strains in individuals with acute diarrhea syndrome in the State of Sucre, Venezuela

In Venezuela, acute diarrheic syndrome (ADS) is a primary cause of morbi-mortality, often involving the Salmonella genus. Salmonella infections are associated with acute gastroenteritis, one of the most common alimentary intoxications, and caused by the consumption of contaminated water and food, especially meat. Conventional and molecular methods were used to detect Salmonella strains from 330 fecal samples from individuals of different ages and both sexes with ADS. Polymerase chain reaction (PCR) was used for the molecular characterization of Salmonella, using invA, sefA, and fliC genes for the identification of this genus and the serotypes Enteritidis and Typhimurium, respectively. The highest frequency of individuals with ADS was found in children 0-2 years old (39.4%), and the overall frequency of positive coprocultures was 76.9%. A total of 14 (4.2%) strains were biochemically and immunologically identified as Salmonella enterica subsp. enterica, of which 7 were classified as belonging to the Enteritidis serotype, 4 to the Typhimurium serotype, and 3 to other serotypes. The S. enterica strains were distributed more frequently in the age groups 3-4 and 9-10 years old. The molecular characterization method used proved to be highly specific for the typing of S. enterica strains using DNA extracted from both the isolated colonies and selective enrichment broths directly inoculated with fecal samples, thus representing a complementary tool for the detection and identification of ADS-causing bacteria.

Nontyphoid Salmonella gastroenteritis in pediatric patients from urban areas in the city of Mérida, Venezuela

Nontyphoid Salmonella (NTS) infections are a frequent cause of self-limited diarrhoeal illness in healthy children that do not usually require antibiotic treatment. This study was conducted by analyzing the phenotypic and genotypic traits of NTS strains from pediatric patients with acute gastroenteritis living in urban areas in the city of Mérida, Venezuela. Thirty-seven Salmonella strains (18 S. Enteritidis; 14 S. Typhimurium; 2 S. Java; 2 S. Saintpaul; 1 S. Infantis) were isolated from 243 stool specimens. These strains were biochemically identified and serotyped. Antimicrobial susceptibility was determined by the disc-diffusion assay. Genetic characterization included plasmid profiling, PCR detection of the spv region and inv genes, and IS200 typing. Thirty (81.0%) of the Salmonella isolates were resistant to the antimicrobial tested. Of these strains, 17 (56.7%) were resistant to at least one antibiotic. Five resistance patterns were observed, of which the most frequently found was the single type (tetracycline, streptomycin or ampicillin). All the S. Typhimurium harbored plasmids, but only three large plasmids (60, 72 and 84 kb) yielded amplicons with a spvR specific primers. All the Salmonella serotypes showed the presence of an inv region. Eight distinct IS200 profiles could be detected among the 37 Salmonella strains studied. Predominant Enteritidis and Typhimurium serotypes, as well as serotypes Java, Saintpaul and Infantis, are circulating in the city of Mérida, Venezuela. Most of these strains are susceptible to first-line antibiotics but active monitoring of isolates for antimicrobial resistance is necessary. IS200 typing, applied in association with conventional methods, allowed the characterization of all isolates and suggested the presence of different infection sources.

Surveillance and Antimicrobial Resistance of Salmonella Strains Isolated from Slaughtered Pigs in Spain

The prevalence of and the antibiotic resistance shown by Salmonella isolated from pigs in Andalusia (southern Spain) is reported. Salmonella enterica was recovered from 40 (33%) of 121 sampled herds, and a total of 65 isolates were serotyped. The most common Salmonella serotypes were Typhimurium and Rissen (30.7% each); others included Derby (9.2%), Brandenburg (9.2%), Newport (7.7%), Bredeney (4.6%), Anatum (3.0%), Hadar (1.5%), and Goldcoast (1.5%). One strain (1.5%) belonging to the monophasic variant of the Typhimurium serotype (Salmonella 4,5,12:i:−) was also detected. Definitive phage type (DT) 104b was the most common Typhimurium phage type isolated. These Salmonella strains were resistant to various antimicrobial agents, including tetracycline (84.6%), streptomycin (69.2%), neomycin (63.0%), sulfonamides (61.5%), ampicillin (53.8%), and amoxicillin (53.8%). All isolates were fully susceptible to ceftriaxone, ciprofloxacin, and colistin. Thirty-nine strains (64%) resistant to four or more antimicrobial agents were defined as multidrug resistant. Multidrug resistance profiles were observed in Salmonella serotypes Typhimurium, Rissen, Brandenburg, Bredeney, a monophasic variant, Gold-coast, Hadar, and Anatum, with serotypes Typhimurium and Brandenburg showing the most complicated resistance patterns (resistant to ≥11 drugs).

The Chemokine CCL2 Is Required for Control of Murine GastricSalmonella entericaInfection

Salmonella enterica is a gram-negative intracellular pathogen that can cause a variety of diseases ranging from gastroenteritis to typhoid fever. The Typhimurium serotype causes gastroenteritis in humans; however, infection of mice results in an enteric fever that resembles human typhoid fever and has been used as a model for typhoid fever. The present study examined the role of the chemokine CCL2 in the control of Salmonella infection. Upon infection with salmonellae, mucosal expression of CCL2 is rapidly up-regulated, followed by systemic expression in the spleen. CCL2(-/-) mice became moribund earlier and had a higher rate of mortality compared to wild-type C57BL/6 mice. Moreover, CCL2(-/-) mice had significantly higher levels of bacteria in the liver compared to wild-type controls. Mucosal and serum interleukin-6 and tumor necrosis factor alpha levels were elevated in CCL2(-/-) mice compared to wild-type mice. In vitro analysis demonstrated that CCL2(-/-) macrophages infected with salmonellae resulted in dysregulated cytokine production compared to macrophages derived from wild-type mice. These data are the first to directly demonstrate CCL2 as a critical factor for immune responses and survival following S. enterica infection.

Antibiotic resistance genes, integrons and multiple antibiotic resistance in thirty-five serotypes of Salmonella enterica isolated from humans and animals in the UK.

To examine 397 strains of Salmonella enterica of human and animal origin comprising 35 serotypes for the presence of aadB, aphAI-IAB, aadA1, aadA2, bla(Carb(2)) or pse1, bla(Tem), cat1, cat2, dhfr1, floR, strA, sul1, sul2, tetA(A), tetA(B) and tetA(G) genes, the presence of class 1 integrons and the relationship of resistance genes to integrons and antibiotic resistance. Some strains were resistant to ampicillin (91), chloramphenicol (85), gentamicin (2), kanamycin (14), spectinomycin (81), streptomycin (119), sulfadiazine (127), tetracycline (108) and trimethoprim (45); 219 strains were susceptible to all antibiotics. bla(Carb(2)), floR and tetA(G) genes were found in S. Typhimurium isolates and one strain of S. Emek only. Class 1 integrons were found in S. Emek, Haifa, Heidelberg, Mbandaka, Newport, Ohio, Stanley, Virchow and in Typhimurium, mainly phage types DT104 and U302. These strains were generally multi-resistant to up to seven antibiotics. Resistance to between three and six antibiotics was also associated with class 1 integron-negative strains of S. Binza, Dublin, Enteritidis, Hadar, Manhattan, Mbandaka, Montevideo, Newport, Typhimurium DT193 and Virchow. The results illustrate specificity of some resistance genes to S. Typhimurium or non- S. Typhimurium serotypes and the involvement of both class 1 integron and non-class 1 integron associated multi-resistance in several serotypes. These data also indicate that the bla(Carb(2)), floR and tetA(G) genes reported in the SG1 region of S. Typhimurium DT104, U302 and some other serotypes are still predominantly limited to S. Typhimurium strains.

Antibiotic Resistance of Salmonella spp. from Animal Sources in Spain in 1996 and 2000

Emergence of resistant and multiresistant bacteria has become an important worldwide sanitary problem. International agencies recommend improving resistance surveillance studies in not only human but also animal origin strains. Because of its ubiquitous characteristics and zoonotic agent consideration, Salmonella spp. can be used as a good indicator microorganism for resistance surveillance studies. Salmonella spp. strains from animal sources isolated in 1996 (107) and 2000 (474) in Spain were tested against 12 different antimicrobials agents, using the disc diffusion method. Results were interpreted following the NCCLS criteria. Data showed that Salmonella spp. strains (61.7% in 1996 and 81.5% in 2000) were resistant to at least one antibiotic. Pig-related strains were considerably more resistant than strains from other sources. Enteritidis serotype was less resistant than other serotypes, except for ampicillin in 1996 (50% resistant) and nalidixic acid in 2000 (65.1% resistant). An emergent monophasic serotype, 4,5,12:i:–, first detected in 1997 in Spain was 100% resistant and 90% multiresistant. Typhimurium serotype was the most common Salmonella serotype from animal sources in both years. It was widely distributed among animals and was among the serotypes with a higher degree of resistance. The ampicillin, chloramphenicol, sulfonamides, streptomycin, and tetracycline resistance pattern, commonly associated with Salmonella serotype Typhimurium DT 104, had spread among other Typhimurium phage types and other Salmonella serotypes. Salmonella spp. strains isolated from feeding stuffs were considerably more susceptible than animal source strains, suggesting that the high Salmonella spp. resistance percentage was probably due to the use of antibiotics in animal farms rather than the consumption of contaminated feeding stuffs.

Evolution of antibiotic resistance of non-typhoidal salmonellae in Greece during 1990-97

Susceptibility to 15 antibiotics was determined in 1548 non-typhoidal salmonella strains isolated in Greece from l990 to l997. The overall prevalence of resistance of both Salmonella enterica serotype Enteritidis and Salmonella enterica serotype Typhimurium increased during the first years of the study. A decrease was observed from 1996, especially for S. Enteritidis, which showed the highest overall antibiotic resistance. S. Typhimurium was the serotype with the highest multiresistance to antibiotics. The rest of the serotypes had very low resistance prevalence compared with both S. Enteritidis and Typhimurium serotypes.