Characterization of Virulence Genotypes, Antimicrobial Resistance Patterns, and Biofilm Synthesis in Salmonella spp Isolated from Foodborne Outbreaks

Salmonella is the main bacterial pathogen that causes foodborne disease, particularly in developing countries. Nontyphoidal Salmonella (NTS) include Enteritidis and Typhimurium as the most prevalent strains which are one of the significant causes of acute gastroenteritis in children. Therefore, identifying the most predominant serovars, types of common contaminated food, and paying attention to their antibiotic resistance are the main factors in the prevention and control strategy of salmonellosis. This study was undertaken to evaluate the prevalence rate of serovars, the biofilm formation, antimicrobial resistance (AMR) status, and phenotypic virulence factors of Salmonella strains isolated from diarrhea samples in some cities of Iran. A total of 40 (10.41%) Salmonella isolates were recovered from 384 diarrhea samples processed and the most common serovar was Salmonella serovar Typhimurium (82.5). Also, all isolates belonging to serovar Typhimurium showed more virulence factors compared to other serovars. The isolates showed a high resistance rate to ampicillin (95%) and nalidixic acid (87.5%), while a low resistance rate was found for chloramphenicol (2.5%). Moreover, significant variances in the capacity of biofilm formation were found between different Salmonella serotypes. The resistance of NTS to extant choice drugs is a potential public health problem. Constant monitoring of AMR pattern and virulence profile of NTS serovars is suggested for the prevention of salmonellosis in humans.

Assessing hygiene indicators in two dairies in Algeria in producing pasteurized milk

Background and Aim:

There is a worldwide controversy about the choice of microbial flora for use as process hygiene indicators. This study aimed to evaluate the pertinence of using either coliforms or Enterobacteriaceae (EB) as process hygiene indicators in the pasteurized milk production line. Two flora families and total flora were used as bacterial indicators in some stages of pasteurized milk production line to identify the origin of post-pasteurization contamination and compare the results obtained for each flora. In addition, the bacteriological profile of isolated coliforms and EB was developed.

Materials and Methods:

One thousand and two hundred samples of pasteurized cow milk and surfaces (pipes and tank) at various processing stages were taken from two dairies in the northern region of Algeria. The total microbial flora (TF), total coliforms (TC), thermotolerant coliforms, and EB were enumerated, following the recommendations of ISO 4833:2006, ISO 4832:2006, and ISO 21528-2:2017 methods, respectively. The bacteriological profile was determined using the API 20E and 10S tests (bioMérieux, France). Furthermore, the cleaning efficiency and disinfection protocol of surfaces were evaluated using contact agar slides 1 (Liofilchem™, Italy).

Results:

Enumeration of the different indicators shows that the highest contamination rate is recorded by the total flora in the two units, 3.28 and 3.78 log CFU/mL, respectively. EB (−0.60 log CFU/mL) at post-pasteurization stage in Unit 1 and coliforms (0.44 log CFU/mL) at the pasteurized packaged milk stage in Unit 2 are the least significant germ families. The lowest compliance rates of bacterial contamination were reported for total flora (82-85%) at the three sampled sites in Unit 2. In comparison, the highest was reported in Unit 1 (99.8%) and 2 (98%) by the EB indicator. Assessing the surface cleaning and disinfection protocol compliance shows that the tank records the highest non-compliance rates for EB and TF (4% and 3%) in Unit 2. EB are represented in both units by various species. Acinetobacter baumannii in Unit 1 and Enterobacter cloacae in Unit 2 are the common species of the three indicator families. Acinetobacter and Enterobacter in Unit 1, Escherichia, Citrobacter, Enterobacter, Klebsiella, and Hafnia in Unit 2 are the most time persistent bacterial genera along the production line. Stenotrophomonas, Serratia, Salmonella, Enterobacter, and Escherichia are common genera in both units.

Conclusion:

The results obtained show no difference in the use of EB or TC as hygiene indicators. However, if the objective is to identify the species of bacterial populations, using EBs are the most appropriate.

Salmonella spp. quorum sensing: an overview from environmental persistence to host cell invasion

Salmonella spp. is one of the main foodborne pathogens around the world. It has a cyclic lifestyle that combines host colonization with survival outside the host, implying that Salmonella has to adapt to different conditions rapidly in order to survive. One of these environments outside the host is the food production chain. In this environment, this foodborne pathogen has to adapt to different stress conditions such as acidic environments, nutrient limitation, desiccation, or biocides. One of the mechanisms used by Salmonella to survive under such conditions is biofilm formation. Quorum sensing plays an important role in the production of biofilms composed of cells from the same microorganism or from different species. It is also important in terms of food spoilage and regulates the pathogenicity and invasiveness of Salmonella by regulating Salmonella pathogenicity islands and flagella. Therefore, in this review, we will discuss the genetic mechanism involved in Salmonella quorum sensing, paying special attention to small RNAs and their post-regulatory activity in quorum sensing. We will further discuss the importance of this cell-to-cell communication mechanism in the persistence and spoilage of Salmonella in the food chain environment and the importance in the communication with microorganisms from different species. Subsequently, we will focus on the role of quorum sensing to regulate the virulence and invasion of host cells by Salmonella and on the interaction between Salmonella and other microbial species. This review offers an overview of the importance of quorum sensing in the Salmonella lifestyle.

Microbial Biofilms in the Food Industry-A Comprehensive Review

Biofilms, present as microorganisms and surviving on surfaces, can increase food cross-contamination, leading to changes in the food industry’s cleaning and disinfection dynamics. Biofilm is an association of microorganisms that is irreversibly linked with a surface, contained in an extracellular polymeric substance matrix, which poses a formidable challenge for food industries. To avoid biofilms from forming, and to eliminate them from reversible attachment and irreversible stages, where attached microorganisms improve surface adhesion, a strong disinfectant is required to eliminate bacterial attachments. This review paper tackles biofilm problems from all perspectives, including biofilm-forming pathogens in the food industry, disinfectant resistance of biofilm, and identification methods. As biofilms are largely responsible for food spoilage and outbreaks, they are also considered responsible for damage to food processing equipment. Hence the need to gain good knowledge about all of the factors favouring their development or growth, such as the attachment surface, food matrix components, environmental conditions, the bacterial cells involved, and electrostatic charging of surfaces. Overall, this review study shows the real threat of biofilms in the food industry due to the resistance of disinfectants and the mechanisms developed for their survival, including the intercellular signalling system, the cyclic nucleotide second messenger, and biofilm-associated proteins.

Antimicrobial Resistance and Biofilm Formation Capacity of Salmonella enterica Serovar Enteritidis Strains Isolated from Poultry and Humans in Poland

Salmonella enterica ser. Enteritidis (S. enterica ser. Enteritidis) is the most frequently detected serovar in human salmonellosis, and its ability to produce a biofilm and the risk of transmission from animals and food of animal origin to humans are significant. The main aim of the present work was to compare S. enterica ser. Enteritidis strains isolated from poultry and human feces in terms of resistance profiles, prevalence of selected resistance genes, and their potential for biofilm formation, by assessing their biofilm growth intensity, the prevalence and expression of selected genes associated with this phenomenon, and the correlation between increased antimicrobial resistance and biofilm formation ability of the two tested groups of S. enterica ser. Enteritidis. This study showed a difference in antimicrobial resistance (minimal inhibitory concentration value) between S. enterica ser. Enteritidis groups; however, the majority of multidrug-resistant (MDR) strains were isolated from poultry (environmental samples from chicken broilers, turkey broilers, and laying hens). Differences in the prevalence of resistance genes were observed; the most common gene among poultry strains was floR, and that among strains from humans was blaTEM. S. enterica ser. Enteritidis strains isolated from poultry under the tested incubation conditions exhibited better biofilm growth than strains isolated from humans. A higher level of gene expression associated with the production of cellulose was only detected in the S48 strain isolated from poultry. On the other hand, increased expression of genes associated with quorum sensing was observed in two strains isolated from poultry farms and one strain isolated from human feces.