Typing of Salmonella enterica serovar Infantis isolates from 51 outbreaks in Germany between 1974 and 2009 by a novel phage-typing scheme

Development of a rapid diagnostic test based on loop-mediated isothermal amplification to identify the most frequent non-typhoidal Salmonella serovars from culture

Identification of Salmonella serovars is performed by conventional seroagglutination or sequencing. These methods are labor-intensive and require technical experience. An easy-to-perform assay allowing the timely identification of the most common non-typhoidal serovars (NTS) is needed. In this study, a molecular assay based on loop-mediated isothermal amplification (LAMP) targeting specific gene sequences of Salmonella Enteritidis, S. Typhimurium, S. Infantis, S. Derby, and S. Choleraesuis has been developed for rapid serovar identification from cultured colonies. A total of 318 Salmonella strains and 25 isolates of other Enterobacterales species that served as negative controls were analyzed. All S. Enteritidis (n = 40), S. Infantis (n = 27), and S. Choleraesuis (n = 11) strains were correctly identified. Seven out of 104 S. Typhimurium and 10 out of 38 S. Derby strains missed a positive signal. Cross-reactions of the gene targets were only rarely observed and restricted to the S. Typhimurium primer set (5 false-positives). Sensitivity and specificity of the assay compared to seroagglutination were as follows: 100% and 100% for S. Enteritidis, 93.3% and 97.7% for S. Typhimurium, 100% and 100% for S. Infantis, 73.7% and 100% for S. Derby, and 100% and 100% for S. Choleraesuis, respectively. With results available in just a few minutes of hands-on time and a test run time of 20 min, the LAMP assay developed here may be a useful tool for the rapid identification of common Salmonella NTS in daily routine diagnostics.

Enteric Organisms Detected in Feces of Dogs With Bloody Diarrhea: 45 Cases

Bloody diarrhea is a common condition in dogs, but studies evaluating the enteropathogens involved specifically in adult dogs are scarce. In the present study, stool samples from 45 adult dogs with bloody diarrhea were evaluated for the four enteric organisms mainly reported in these cases: canine parvovirus type 2 (CPV-2), Clostridioides difficile, Clostridium perfringens, and Salmonella spp. In addition, the samples were also tested for coronavirus, rotavirus, Giardia spp., and Escherichia coli pathotypes to provide a better understanding of possible co-occurrence. Vaccination status, diet, and clinical outcome were also obtained when available. CPV-2b was identified in 17 dogs (37.8%), being the most frequent cause of bloody diarrhea, including completely vaccinated adult dogs. Toxigenic C. difficile and C. perfringens netF⁺ were detected in 6 (13.3%) and 5 (11.1%) dogs, in some cases in a co-occurrence with other enteric organisms. Three fatal cases of salmonellosis were identified in dogs fed a raw meat-based diet, raising the risks associated with this increasing practice.

Characterization of Salmonella enterica serovars recovered from meat products legally and illegally imported into the EU reveals the presence of multiresistant and AmpC-producing isolates

BACKGROUND

Food products of animal origin brought into the EU from third countries, both legally and illegally, can harbor foodborne pathogens such as Salmonella enterica. In this study, we examined five S. enterica isolates recovered either from legally imported chicken meat (n = 3) or from meat products confiscated from air travel passengers arriving in Germany (n = 2). The isolates were serotyped and further characterized by antimicrobial susceptibility testing, PCR-detection and sequencing of genes associated with antimicrobial resistances, and macrorestriction analysis. Transferability of resistance to third-generation cephalosporins was assessed by conjugation experiments and the plasmids tested for their incompatibility groups.

RESULTS

The three isolates from legal imports were identified as S. Heidelberg or as non-flagellated. All three isolates were identified as AmpC producers carrying bla CMY-2 and as non-susceptible to ciprofloxacin. They were additionally resistant to tetracycline and sulfamethoxazole. The bla CMY-2-carrying plasmids were transferable by conjugation and belonged to incompatibility groups IncI1 or IncA/C. The two isolates from illegally imported meat belonged to the serovars Infantis or Weltevreden. The former was phenotypically resistant to five classes of antimicrobial agents while the S. Weltevreden isolate was fully susceptible to all agents tested.

CONCLUSION

The results of this study demonstrate that meat products imported from third countries, both legally and illegally, can harbor multiresistant Salmonella enterica. Consequently, these imports could constitute a source for the dissemination of antimicrobial resistant isolates, including those resistant to third-generation cephalosporins and fluoroquinolones.

Detection of common clones of Salmonella enterica serotype Infantis from human sources in Tehran hospitals

AIM

The aims of this study were to investigate antibiotic resistance pattern and molecular characterization of Salmonella Infantis strains, isolated from human sources in Tehran hospitals from 2008 to 2010.

BACKGROUND

Infection caused by Salmonella is one of the major public health problems. Despite the clinical importance of Salmonella enteric subsp. enteric serovar Infantis in humans, there is no information available about the common clones of Salmonella Infantis in clinical isolates in Iran.

METHODS

S. Infantis strains were identified by conventional microbiological and serological testing. The antimicrobial susceptibility of the S.Infantis isolates was determined using the disk diffusion method. The genetic relatedness and the dominant clones of S. Infantis strains were detected by the Multi Locus Sequence Typing (MLST) and pulsed-field gel electrophoresis (PFGE) techniques.

RESULTS

More than 80% of the S. Infantis isolates represented multidrug-resistant patterns. PFGE revealed high genetic similarity among S. Infantis strains. While, MLST indicated high-clonal similarity among strains, where all S. Infantis strains were assigned to the ST32 sequence type.

CONCLUSION

This is the first study in Iran conducted to determine the sequence types of S. Infantis in clinical isolates using MLST. The genetically closed MDR S. Infantis clones were responsible for the apparent endemic occurrence of salmonellosis, caused by this Salmonella serovar, in Tehran.

Brotes de enfermedades transmitidas por los alimentos estudiados mediante técnicas moleculares

Objetivo Aplicar una técnica de reacción en cadena de la polimerasa (PCR) múltiple en tiempo real para la detección de Salmonella spp., Listeria monocytogenes y Yersinia enterocolitica, como herramienta de apoyo diagnóstico en la vigilancia de brotes de enfermedad transmitida por alimentos.Materiales y Métodos Se aplicó la metodología molecular en muestras clínicas provenientes de individuos que estaban asociados a brotes de enfermedad transmitida por alimentos de dos departamentos de Colombia. Los resultados se compararon con los datos arrojados por la metodología convencional de cultivo. Adicionalmente a los aislamientos obtenidos se les evaluó relación clonal mediante la técnica de electroforesis de campo pulsado (PFGE).Resultados Se determinó un total de 123 casos de enfermedad transmitida por alimentos de los cuales 45 muestras biológicas fueron confirmadas por laboratorio y 88 mediante nexo epidemiológico. La metodología molecular detectó 35/45 muestras positivas frente a 17/45 muestras positivas detectadas mediante la metodología convencional. La PFGE demostró relación clonal en cada brote.Conclusión Los resultados del estudio demuestran la aplicabilidad de la técnica molecular como herramienta útil de apoyo diagnóstico en la caracterización de brotes de enfermedad transmitida por alimentos, permitiendo una respuesta oportuna y confiable.

Multiple clones and low antimicrobial resistance rates for Salmonella enterica serovar Infantis populations in Greece

All the Salmonella enterica ser. Infantis strains isolated under official control programs in Greece during a four year period were studied, 23 of human origin, 16 from food animals and one from food. Molecular analyses (PFGE) in combination with antimicrobial susceptibility testing were used to study whether the occurrence S. Infantis in Greece resulted from different biotypes or a successful spread of one clone. Low rates of antimicrobial resistance were observed, except for streptomycin among human isolates (48%), indicating that selective pressure due to consumption of antimicrobials has not resulted the spread of dominant clones. Pulsed Field Gel Electrophoresis revealed 31 XbaI distinct pulsotypes among the 40 strains with 60% overall similarity reflecting diversity. Four main clusters were constructed, using an 85% cut off value, clusters A, B, C and D consisting of 14, 6, 8 and 8 isolates respectively. Point source of transmission was not hypothesized as multiple reservoirs of the serovar seem to be present in Greece during the study period.

The risk of carriage of Salmonella spp. and Listeria monocytogenes in food animals in dynamic populations

Salmonella spp. and Listeria monocytogenes are foodborne pathogens of global importance. We assessed their risks and associated factors in a highly dynamic population of animals. Animal and environmental samples were collected from dairy cattle, sheep, camel and chickens at either the farms or the abattoirs. The pathogens were detected using a combination of bacterial enrichment culture and real‐time polymerase chain reaction (PCR). Data on putative risk factors were collect and analysed for their significance of association with these pathogens.

Salmonella spp. were detected at higher proportions in sheep faeces and sheep carcasses in comparison to cattle faeces (odds ratio = 2.4 and 2.2, respectively). This pathogen was less common in milk or carcasses samples from cattle or chickens. Sheep and camel carcass samples were highly contaminated with Salmonella spp. Faecal samples from cattle had the most diverse serovars of Salmonella enterica including S. Newport, S. Haifa, S. Kedougou, S. Kentucky, S. Mbandaka and S. Goettingen. Exotic serovars in sheep included S. Eastbourne, S. Chester and S. Kottnus. Serovars that were shed in camel faeces included S. Newport, S. Bovismorbificans and S. Infantis. In all sampled populations, detection of Salmonella spp. was more likely during warmer months than cold months. Listeria monocytogenes was not common in the targeted populations and was detected at a rate of 2.4%, mainly from sheep carcasses. The study highlights the role of food animals as reservoirs of pathogens across boundaries since all feed are imported in that population from different parts of the world.

Genotyping of Salmonella with lineage-specific genes: correlation with serotyping

BACKGROUND

The bacterial genus Salmonella encompasses a large number of serotypes that are genetically very similar but biologically quite different, especially in pathogenic properties and host specificity. Serotyping has been used for the classification, identification, and epidemiological investigation due to its excellent discriminating power, but it cannot distinguish the different pathogenic lineages within a polyphyletic serotype. Additionally, very few institutions have the comprehensive set of antisera for typing. Therefore various studies have been performed to explore alternative assays to differentiate Salmonella isolates, such as the search for genes that can be used as potential molecular substitutes for serotyping. However, the genes tested so far have often given inconsistent results.

METHODS

In this study, the discriminating power of seven genes to differentiate 309 Salmonella strains representing 26 serotypes was evaluated and the results were compared with those of other methods.

RESULTS

The seven newly selected genes have a good power to differentiate different serovars. The tree based on the concatenated sequences of these genes revealed phylogenetic relationships of the bacteria consistent with that of the whole genome tree.

CONCLUSION

Individual Salmonella lineages each have specific genes that can be used to differentiate Salmonella isolates on a phylogenetic basis.

A prolonged outbreak of Salmonella Infantis associated with pork products in central Germany, April-October 2013

One of the largest and longest Salmonella outbreaks in Germany within the last 10 years occurred in central Germany in 2013. To identify vehicles of infection, we analysed surveillance data, conducted a case-control study and food traceback. We identified 267 cases infected with Salmonella Infantis with symptom onset between 16 April and 26 October 2013 in four neighbouring federal states. Results of our study indicated that cases were more likely to have eaten raw minced pork from local butcher's shops [odds ratio (OR) 2·5, 95% confidence interval (CI) 1·1-5·8] and have taken gastric acid-reducing or -neutralizing medication (OR 3·8, 95% CI 1·3-13) than controls. The outbreak was traced back to contaminated raw pork products found in different butcher's shops supplied by one slaughterhouse, to pigs at one farm and to an animal feed producer. Characterization of isolates of human, food, animal, feed, and environmental origin by phage-typing and pulsed-field gel electrophoresis confirmed the chain of infection. Insufficient hygiene standards in the slaughterhouse were the most probable cause of the ongoing transmission. We recommend that persons taking gastric acid suppressants should refrain from consuming raw pork products. Improving and maintaining adequate hygiene standards and process controls during slaughter is important to prevent future outbreaks.

From network analysis to risk analysis--An approach to risk-based surveillance for bovine tuberculosis in Minnesota, US

Bovine tuberculosis (bTB) was first detected in 2005 in cattle in northwestern Minnesota (MN) through slaughter surveillance. By the end of 2008, 12 cattle herds were infected with bTB, and the main cause for infection was determined to be the movement of infected animals between herds. Bovine tuberculosis was contained in a smaller area in northwestern Minnesota classified as modified accredited (MA), corresponding to a prevalence inferior to 0.1% in cattle. From January 2008 to 2011, all cattle movements within the bTB MA were recorded electronically. The primary objectives of this study were to characterize cattle movements within this region and identify cattle herds with higher risk of bTB introduction based on network parameters and known risk factors from the published literature. During the period that data was collected, 57,460 cattle were moved in 3762 movements corresponding to permits issued to 682 premises, mostly representing private farms, sale yards, slaughter facilities and county or state fairs. Although sale yards represented less than 2% of the premises (nodes), 60% of the movements were to or from a sale yard. The network showed an overall density of 0.4%, a clustering coefficient of 14.6% and a betweenness centralization index of 12.7%, reflecting the low connectivity of this cattle network. The degree distribution showed that 20% of nodes performed 90% of the movements. Farms were ranked based on the total risk score and divided into high, medium, and low risk groups based on the score and its variability. The higher risk group included 14% (n=50) of the farms, corresponding to 80% of the cumulative risk for the farms in the bTB area. This analysis provides a baseline description about the contact structure of cattle movements in an area previously infected with bTB and develops a framework for a targeted surveillance approach for bTB to support future surveillance decisions.