Enterotoxin Production Research Articles

Both LTA and LTB Subunits Are Equally Important to Heat-Labile Enterotoxin (LT)-Enhanced Bacterial Adherence.

There is increasing evidence indicating that the production of heat-labile enterotoxin (LT) enhances bacterial adherence within in vitro and in vivo models. However, which subunit plays the main role, and the precise regulatory mechanisms remain unclear. To further elucidate the contribution of the A subunit of LT (LTA) and the B subunit of LT (LTB) in LT-enhanced bacterial adherence, we generated several LT mutants where their ADP-ribosylation activity or GM1 binding ability was impaired and evaluated their abilities to enhance the two LT-deficient E. coli strains (1836-2 and EcNc) adherence. Our results showed that the two LT-deficient strains, expressing either the native LT or LT derivatives, had a significantly greater number of adhesions to host cells than the parent strains. The adherence abilities of strains expressing the LT mutants were significantly reduced compared with the strains expressing the native LT. Moreover, E. coli 1836-2 and EcNc strains when exogenously supplied with cyclic AMP (cAMP) highly up-regulated the adhesion molecules expression and improved their adherence abilities. Ganglioside GM1, the receptor for LTB subunit, is enriched in lipid rafts. The results showed that deletion of cholesterol from cells also significantly decreased the ability of LT to enhance bacterial adherence. Overall, our data indicated that both subunits are equally responsible for LT-enhanced bacterial adherence, the LTA subunit contributes to this process mainly by increasing bacterial adhesion molecules expression, while LTB subunit mainly by mediating the initial interaction with the GM1 receptors of host cells.

Characterization of NanR Regulation of Sialidase Production, Sporulation and Enterotoxin Production by Clostridium perfringens Type F Strains Carrying a Chromosomal Enterotoxin Gene

Clostridium perfringens type F food poisoning (FP) strains produce C. perfringens enterotoxin (CPE) to cause a common bacterial food-borne illness in the United States. During FP, CPE is synthesized in the intestines when C. perfringens sporulates. Besides CPE, FP strains also produce sialidases. Most FP strains carry their cpe gene on the chromosome and all surveyed chromosomal cpe (c-cpe) FP strains produce NanH sialidase or both NanJ and NanH sialidases. NanR has been shown previously to regulate sialidase activity in non-FP strains. The current study investigated whether NanR also regulates sialidase activity or influences sporulation and CPE production for c-cpe FP strains SM101 and 01E809. In sporulation medium, the SM101 nanR null mutant showed lower sialidase activity, sporulation, and CPE production than its wild-type parent, while the 01E809 nanR null mutant showed roughly similar sialidase activity, sporulation, and CPE production as its parent. In vegetative medium, the nanR null mutants of both strains produced more spores than their parents while NanR repressed sialidase activity in SM101 but positively regulated sialidase activity in 01E809. These results demonstrate that NanR regulates important virulence functions of c-cpe strains, with this control varying depending on strain and culture conditions.

Virulence Potential and Antibiotic Susceptibility of S. aureus Strains Isolated from Food Handlers.

Staphylococcus spp. are common members of the normal human flora. However, some Staphylococcus species are recognised as human pathogens due to the production of several virulence factors and enterotoxins that are particularly worrisome in food poisoning. Since many of Staphylococcal food poisoning outbreaks are typically associated with cross-contamination, the detection of S. aureus on food handlers was performed. Hand swabs from 167 food handlers were analysed for the presence of S. aureus. More than 11% of the samples were positive for S. aureus. All S. aureus strains were isolated and analysed for the presence of virulence and enterotoxin genes, namely, sea, seb, sec, sed, seg, sei, tsst-1 and pvl. The same strains were phenotypically characterised in terms of antibiotic susceptibility using the disc diffusion method and antimicrobial agents from 12 different classes. A low prevalence of antibiotic-resistant strains was found, with 55.6% of the strains being sensitive to all of the antimicrobial agents tested. However, a high prevalence of resistance to macrolides was found, with 44.4% of the strains showing resistance to erythromycin. At least one of the virulence or toxin genes was detected in 61.1% of the strains, and seg was the most prevalent toxin gene, being detected in 44.4% of the strains.

First Genome-Based Characterisation and Staphylococcal Enterotoxin Production Ability of Methicillin-Susceptible and Methicillin-Resistant Staphylococcus aureus Strains Isolated from Ready-to-Eat Foods in Algiers (Algeria).

Staphylococcus aureus is a pathogenic microorganism of humans and animals, able to cause foodborne intoxication due to the production of staphylococcal enterotoxins (SEs) and to resist antibiotic treatment as in the case of methicillin-resistant S. aureus (MRSA). In this study, we performed a genomic characterisation of 12 genetically diverse S. aureus strains isolated from ready-to-eat foods in Algiers (Algeria). Moreover, their ability to produce some classical and new staphylococcal enterotoxins (SEs) was investigated. The 12 S. aureus strains resulted to belong to nine known sequence types (STs) and to the novel ST7199 and ST7200. Furthermore, S. aureus SA46 was assigned to the European clone MRSA-ST80-SCCmec-IV. The 12 strains showed a wide endowment of se and sel (staphylococcal enterotoxin-like toxin) genes (sea, seb, sed, seg, seh, sei, selj, sek, sem, sen, seo, seq, ser, selu2, selw, selx, sey, sel30; ψent1-ψent2), including variants and pseudogenes, and harboured the enterotoxin gene cluster (egc) types 1 and 5. Additionally, they produced various amounts of SEA (64.54-345.02 ng/mL), SEB (2871.28-14739.17 ng/mL), SED (322.70-398.94 ng/mL), SEH (not detectable-239.48 ng/mL), and SER (36,720.10-63,176.06 ng/mL) depending on their genotypes. The genetic determinants related to their phenotypic resistance to β-lactams (blaZ, mecA), ofloxacin (gyrA-S84L), erythromycin (ermB), lincomycin (lmrS), kanamycin (aph(3')-III, ant(6)-I), and tetracyclin (tet(L), tet(38)) were also detected. A plethora of virulence-related genes, including major virulence genes such as the tst gene, determinant for the toxic shock syndrome toxin-1, and the lukF-PV and lukS-PV genes, encoding the panton-valentine leukocidin (PVL), were present in the S. aureus strains, highlighting their pathogenic potential. Furthermore, a phylogenomic reconstruction including worldwide foodborne S. aureus showed a clear clustering based on ST and geographical origin rather than the source of isolation.

Microbiological hazard identification in selective food products and their association with food safety practices in Hyderabad, India

Microbiological risk assessment (MRA) is an emerging tool for evaluating the safety of food and water supplies. In this study, identification of microbial hazards in selected samples and their association with food safety practices were seen. Data were analyzed using Analysis of Variance (ANOVA) through the General Linear Models (GLM) procedure of the statistical analysis system software (SPSS version-11.5, 2003). The least significant differences were used to test means at p<0.05. Odds ratio (OR) values with 95% CI were computed to obtain the risk of the presence of the foodborne pathogen in a particular food. Analysis of 600 food samples indicated that (50%) was high in raw chicken samples followed by carrot salad (41%). The other emerging foodborne pathogens like (MRSA), , and were not detected in any of the food samples. Pathogens like (73.5%) in khoa, (45%) and (62.7%) in paneer were detected. A total of (n=143) cultures were analyzed for enterotoxin and coagulase enzyme. Nine cultures (6.3%) showed a positive result for enterotoxin production. For the risk assessment of contamination in foods, coagulase test and toxin production of isolates have to be evaluated. A significant association was found between the type of storage and log concentration of in khoa, whereas, with water for washing hands, the status of nails, and cleaning cloth were contributing to foodborne pathogens in other products. There is a need to provide food safety training to food handlers to improve food safety.

The Enterotoxin Production and Antimicrobial Resistance of Campylobacter Strains Originating from Slaughter Animals.

The pathogenicity of animal-origin Campylobacter strains, including antimicrobial resistance and enterotoxigenicity, was determined in this study. Overall, 149 Campylobacter isolates originating from cattle, swine and poultry were tested. The antimicrobial resistance profiles were examined by the diffusion disk method. The dominant resistance pattern was CIP_TET. The resistance rates for ciprofloxacin among swine, cattle and poultry isolates were 84%, 51% and 66%, respectively; for tetracycline, they were 82%, 57.1% and 76%, respectively. None of the obtained isolates was resistant to all four antimicrobials tested. The ability to produce enterotoxins was assessed by the use of a suckling mouse bioassay, with intestinal fluid accumulation as a positive result, and by CHO assay, with the elongation of cells as a positive result. The ability to produce enterotoxins was significantly higher among cattle isolates (61.2% and 71.4% positive isolates, respectively, in the bioassay and the CHO assay) than among swine (16% and 32% positive isolates, respectively) or poultry isolates (14% and 22% positive isolates, respectively). A strong positive correlation between in vitro and in vivo enterotoxicity tests was demonstrated.

Influence of Season and Food Type on Bacterial and Entero-Toxigenic Prevalence of Staphylococcus aureus.

Staphylococcus (S.) aureus is a coagulase-positive pathogen of interest for human health and food safety in particular. It can survive in a wide environmental temperature range (7–48 °C, optimum 37 °C). Its enterotoxins are thermostable, which increases the risk of potential contamination in a variety of food products. Here we investigated the influence of seasonality and food type on bacterial count and presence of S. aureus enterotoxins. To do this, we analyzed 3604 food samples collected over a 5-year period (2016–2020). Ordinal logistic regression showed an influence of both seasonality and food type on the bacterial count. Regarding bacterial counts, winter was found to be the season with the highest risk, while with regards to enterotoxin production, the highest risk was found in autumn, specifically in October. The risk of contamination with S. aureus was greatest for dairy products. Our findings may inform food epidemiologists about foodborne illness prevention and risk to human health.

Lactic acid bacteria as biocontrol agents to reduce Staphylococcus aureus growth, enterotoxin production and virulence gene expression

The capacity of six lactic acid bacteria (LAB) strains to decrease both the growth of Staphylococcus aureus UCLM-1 and the production of staphylococcal enterotoxins growing in co-culture in sheep's milk, was evaluated. During incubation of the cultures, samples were taken to monitor LABs and Staphylococcus growth, pH, production of organic acids, presence of the staphylococcal enterotoxins A, B, C, D, and E and the expression of 11 staphylococcal genes involved in virulence and enterotoxin production. Strains Lactiplantibacillus plantarum UCLM-101 and UCLM-56 yielded the highest decreases of both Staphylococcus aureus viable cell counts and pH, followed by the strain Levilactobacillus brevis UCLM-99. Analysis of organic acids and enterotoxins production by these three strains displayed that the main acid produced was lactic acid, while enterotoxins were not detected in the co-cultures with any of them. In addition, a decrease in the expression of some staphylococcal genes was observed, which varied depending on the LAB strain and the incubation time. Results allow us to propose the use of any of these three strains as biocontrol agents in the manufacture of “free of preservatives” dairy products, to avoid the risk of staphylococcal foodborne infections.

Antibiogram and virulence profiling reveals multidrug resistant Staphylococcus aureus as the predominant aetiology of subclinical mastitis in riverine buffaloes.

Staphylococcus spp. are the major causal agents of mastitis in dairy animals worldwide leading to profound economic losses and public health threats. Recently, Staphylococcus aureus has emerged as a multidrug resistant and zoonotic pathogen. This study aimed to characterize S. aureus in subclinical mastitis (SCM) milk samples of riverine buffaloes in Bangladesh through antibiogram and virulence gene(s) profiling, and 16S rRNA gene sequencing. We characterized S. aureus in SCM milk samples (N = 500) of riverine buffaloes through antibiogram and virulence gene(s) profiling, and 16S rRNA gene sequencing. Out of 500 milk samples tested, 188 (37.6%) were found positive for SCM. From 188 SCM samples, 291 isolates were obtained with a prevalence of S. aureus in 37.4% (109/291) isolates. Phylogenetic analysis revealed the evolutionary divergence of S. aureus isolates in bubaline SCM milk samples. The antibiogram profiling showed that about 96.0% S. aureus isolates were multidrug resistant (MDR). Notably, 29 and 16 isolates harboured methicillin-resistant (mecA) and panton-valentine leucocidin (pvl) genes, respectively, and 46 plasmid-bearing isolates were MDR. Nine Staphylococcal enterotoxins (SEs/SEls) including sea (11.9%), sec (7.4%), sed (4.6%), seg (3.7%), and seh (3.7%) were detected with 72.48% toxinotypes comprising a single gene. This study therefore suggests S. aureus as the single-most aetiology (∼37.0%) of SCM in riverine buffaloes, and emergence of MDR, enterotoxin producing, and virulent S. aureus strains could impose potential threats to animal welfare and public health.

Molecular detection of staphylococcus aureus enterotoxin genes

In this work, S. aureus isolates from meat and meat products were examined for frequency, profiles of antibiotic susceptibility, and virulence genes (seb, sea, sec, sed, see, and fme A). Staphylococcal food poisoning is one of the most economically important foodborne diseases in the world. S. aureus is a prominent food-borne pathogen and common food contamination across the world. Some S. aureus strains generate staphylococcal enterotoxins (SEs), which can cause staphylococcal food poisoning (SFP). Staphylococcus aureus (S. aureus) is one of the most frequently studied foodborne bacteria due to its high pathogenicity, production of heat-stable enterotoxins, and its continued development of resistance to multiple antibiotics. Despite enterotoxigenic staphylococci being thermally killed, cooked beef products may still contain staphylococcal enterotoxins SEs since these toxins are thermo persistent and cannot be removed by heat processing. Therefore, this investigation into the frequency of MRSA genes in certain fresh meat and canned meat was done to learn more about the disease. A total of 80 random samples, Twenty meat samples from butchers, and sixty samples each of Luncheon, Tune, Chicken pieces, Minced meat, Grilled meat, Hamburger Fresh meat and Sausage from some supermarkets in Hilla city in Iraq.

Occurrence and Characteristics of Staphylococcus aureus Isolated from Dairy Products

Food, particularly milk and cheese, may be a reservoir of multi-drug resistant Staphylococcus aureus strains, which can be considered an important issue in terms of food safety. Furthermore, foods of animal origin can be a cause of staphylococcal food poisoning via the production of heat-stable enterotoxins (SE). For this reason, we investigated the prevalence of and characterized Staphylococcus aureus strains isolated from milk and fresh soft cheese obtained from farms located in Wielkopolskie and Zachodniopomorskie Provinces in Poland. Overall, 92% of S. aureus isolates were positive for at least one of the 18 enterotoxin genes identified, and 26% of the strains harbored 5 to 8 enterotoxin genes. Moreover, the S. aureus strains contained genes conferring resistance to antibiotics that are critically important in both human and veterinary medicine, i.e., β-lactams (mecA), aminoglycosides (aac(6′)/aph(2″), aph(3′)-IIIa, ant(4′)-Ia) and MLSB (erm(A), msr(A), lun(A)). The antimicrobial susceptibility of S. aureus to 16 antibiotics representing 11 different categories showed that 74% of the strains were resistant to at least 1 antibiotic. Moreover, 28% of the strains showed multidrug resistance; in particular, two methicillin-resistant S. aureus strains (MRSA) exhibited significant antibiotic resistance. In summary, our results show that dairy products are contaminated by S. aureus strains carrying genes encoding a variety of enterotoxins as well genes conferring resistance to antibiotics. Both MRSA strains and MSSA isolates showing multidrug resistance were present in foods of animal origin.

Antibiogram profiles and virulence factors associated with water-borne gram-negative bacteria from Ogbese river, Edo State, Nigeria

Surface waters such as flowing rivers, fresh water lakes and hand dug wells are the major sources of water for most rural dwellers in Nigeria. These are often consumed without testing their potability. This study was conducted to assess the bacteriological quality of surface water sampled from five (5) sampling locations on Ogbese river in Ogbese and Olumoye towns, Ovia North East Local Government Area, Edo State. Water samples were collected in duplicates from the sampling locations during the months of June 2018 to February 2019. Bacteriological analysis of the water samples was conducted using the membrane filtration technique and isolates identified by standard cultural and genomic procedures. Disc diffusion technique was utilized to determine the antibiotic sensitivity profiles of the identified bacteria. Other microbiological analysis which comprised of screening for enterotoxin production, invasiveness, hemolysin production and serum resistance, which are all virulence factors were performed using relevant methods. The total heterotrophic bacterial count varied from 1.0 ± 32.0 ×104𝑐𝑓𝑢/𝑚𝑙 and 1.0 ±0.12 ×104𝑐𝑓𝑢/𝑚𝑙 to 9.7 ± 2.23 ×104𝑐𝑓𝑢/𝑚𝑙. The total coliform count ranged from 0.1 ± 0.02 ×102𝑐𝑓𝑢/𝑚𝑙 to 5.5 ± 0.05 ×102𝑐𝑓𝑢/𝑚𝑙. The observed differences between the mean heterotrophic bacterial and coliform counts recorded for Ogbese and Olumoye sampling points was significant (P< 0.05). The identified bacterial isolates included; Escherichia coli, Enterobacter cloacae, Shigella flexneri, Salmonella enterica, Vibrio cholerae, Klebsiella pneumoniae and Pseudomonas aeruginosa Both E. coli (60.0%) and E. cloacae (60.0%) were the most frequently isolated water borne isolates cultured from Ogbese sampling point. All E. coli and S. enterica isolates exhibited sensitivity towards ciprofloxacin and streptomycin. All S. flexneri isolates were invasive and serum resistant. There is an urgent need by relevant Governmental and Non –Governmental agencies to conduct advocacy programs targeted at these communities on the necessity of treating and disinfecting abstracted water sourced directly from the water body prior to drinking.

Detection and enterotoxin production of Staphylococcus aureus isolates in artisanal cheese made from raw milk

Abstract The aim of the study was to determine whether the physicochemical factors of the matrix and the traditional acid-set cheese-making conditions allow the growth of coagulase-positive staphylococci (CoPS) and the synthesis of enterotoxins, which should contribute to an objective risk assessment in cheese production related to CoPS. CoPS were isolated from 72% of acid-set cheeses ranging from 1.70 to 5.15 log10 CFU g−1. CoPS in a number ≥ 4 log10 CFU g−1 were determined in 5.56% of the acid-set cheese samples. Out of the total number of CoPS isolated from cheese, 37.62% of the isolates have been shown to produce enterotoxins. All isolated strains that produced enterotoxins were identified as Staphylococcus aureus based on the detection of spa gene by PCR. For cheese-derived isolates with CoPS number ≥ 4 log10 CFU g−1, it has been proven that they possess sec gene encoding staphylococcal enterotoxin C. According to our results, during the proper fermentation process of artisanal acid-set cheese, the conditions do not support the growth of a critical level of staphylococci or the production of enterotoxins.

Intestinal Epithelial Cells Modulate the Production of Enterotoxins by Porcine Enterotoxigenic E. coli Strains.

Enterotoxigenic Escherichia coli (ETEC) strains are one of the most common etiological agents of diarrhea in both human and farm animals. In addition to encoding toxins that cause diarrhea, ETEC have evolved numerous strategies to interfere with host defenses. These strategies most likely depend on the sensing of host factors, such as molecules secreted by gut epithelial cells. The present study tested whether the exposure of ETEC to factors secreted by polarized IPEC-J2 cells resulted in transcriptional changes of ETEC-derived virulence factors. Following the addition of host-derived epithelial factors, genes encoding enterotoxins, secretion-system-associated proteins, and the key regulatory molecule cyclic AMP (cAMP) receptor protein (CRP) were substantially modulated, suggesting that ETEC recognize and respond to factors produced by gut epithelial cells. To determine whether these factors were heat sensitive, the IEC-conditioned medium was incubated at 56 °C for 30 min. In most ETEC strains, heat treatment of the IEC-conditioned medium resulted in a loss of transcriptional modulation. Taken together, these data suggest that secreted epithelial factors play a role in bacterial pathogenesis by modulating the transcription of genes encoding key ETEC virulence factors. Further research is warranted to identify these secreted epithelial factors and how ETEC sense these molecules to gain a competitive advantage in the early engagement of the gut epithelium.

Establishment and Validation of a Two-Step LAMP Assay for Detection of Bacillus cereus-Group Isolates in Food and Their Possibility of Non-haemolytic Enterotoxin Production.

The closely related members of the Bacillus cereus-group can mainly only be differentiated by whole genome sequencing. Among them, there are potentially toxin-producing bacteria. When consumed with food, these can cause vomiting or diarrhea and abdominal cramps. To date, although no EU-wide threshold exists, a bacterial count of 105 CFU/g can be regarded as critical. Specific and rapid detection of the bacteria is difficult due to their close relationship, and no loop-mediated isothermal amplification (LAMP) assay has been developed so far to detect potentially toxin-producing members of the B. cereus-group. Aim of this study was to develop a LAMP method to detect critical cell counts specifically and rapidly of potentially non-haemolytic enterotoxin (NHE)-producing cells of this group. A two-step LAMP assay was developed. First, the target sequence groEL was used to determine the representatives of the B. cereus-group. Second, since bacteria in which nheB is present are basically capable of producing enterotoxins, this gene was chosen for detection. The specificity of the developed assay was 100% for B. cereus-group isolates and 93.7% for the detection of nheB. The analytical sensitivity was 0.1 pg DNA/μl. Using simplified DNA extraction by boiling, cell-based sensitivity was determined. Targeting groEL and nheB, 11.35–27.05 CFU/reaction and 11.35–270.5 CFU/reaction were detectable, respectively. Artificially contaminated samples were investigated to prove the application in foods. Direct detection of the critical value of B. cereus-group cells was possible in 83.3% of samples and detecting the toxin-gene 50% thereof. After a 6-h incubation period, the detection rate increased to 100 and 91.7%, respectively. Additionally, 100 natively contaminated food samples were tested, also quantitatively and culturally. Samples with relevant contamination levels were reliably detected using groEL-LAMP. After a 6-h incubation period, isolates bearing the toxin gene nheB could also be reliably detected. In addition, colony material was boiled and used as a LAMP template for simple detection. Specificity for the B. cereus-group was 100 and 93.22% detecting nheB. The study demonstrated that screening of food samples with the groEL/nheB-LAMP assay can be performed within 1 day, making it possible to detect critical levels of potentially NHE-toxin-producing cells of the B. cereus-group.

Regulatory and Enterotoxin Gene Expression and Enterotoxins Production in Staphylococcus aureus FRI913 Cultures Exposed to a Rotating Magnetic Field and trans-Anethole.

The study aimed to examine the influence of a rotating magnetic field (RMF) of two different frequencies (5 and 50 Hz) on the expression of regulatory (agrA, hld, rot) and staphylococcal enterotoxin (SE—sea, sec, sel) genes as well as the production of SEs (SEA, SEC, SEL) by the Staphylococcus aureus FRI913 strain cultured on a medium supplemented with a subinhibitory concentration of trans-anethole (TA). Furthermore, a theoretical model of interactions between the bacterial medium and bacterial cells exposed to RMF was proposed. Gene expression and SEs production were measured using quantitative real-time PCR and ELISA techniques, respectively. Based on the obtained results, it was found that there were no significant differences in the expression of regulatory and SE genes in bacteria simultaneously cultured on a medium supplemented with TA and exposed to RMF at the same time in comparison to the control (unexposed to TA and RMF). In contrast, when the bacteria were cultured on a medium supplemented with TA but were not exposed to RMF or when they were exposed to RMF of 50 Hz (but not to TA), a significant increase in agrA and sea transcripts as compared to the unexposed control was found. Moreover, the decreased level of sec transcripts in bacteria cultured without TA but exposed to RMF of 50 Hz was also revealed. In turn, a significant increase in SEA and decrease in SEC and SEL production was observed in bacteria cultured on a medium supplemented with TA and simultaneously exposed to RMFs. It can be concluded, that depending on SE and regulatory genes expression as well as production of SEs, the effect exerted by the RMF and TA may be positive (i.e., manifests as the increase in SEs and/or regulatory gene expression of SEs production) or negative (i.e., manifests as the reduction in both aforementioned features) or none.

Prevalence and diversity of Staphylococcus aureus in the Zambian dairy value chain: A public health concern

Staphylococcus aureus is an important opportunistic pathogen of both humans and animals. It can cause several diseases, including mastitis, as well as food poisoning by production of heat-stable enterotoxins in food. The aim of this study was to determine the prevalence of S. aureus and the diversity of strains circulating in the Zambian dairy value chain, which have not been studied in detail before. Three provinces were covered by the study (Lusaka, Southern, and Western) and almost 2000 samples along the dairy value chain, covering both the informal and formal market sectors, were taken at two time points (dry and wet season), with a special focus on raw milk. Nearly 300 presumptive S. aureus isolates were confirmed by MALDI-TOF MS and real-time PCR. Raw milk from traditional and smallholder farms was widely contaminated with S. aureus; prevalence was 33–46% depending on the study province. Raw milk from milk collection centres, informal traders, traditional market sellers, and processors were also frequently contaminated with S. aureus. In addition, S. aureus was detected in several milk bucket swabs and nasal and hand swabs of milkers. From industrially processed (heat-treated) milk and dairy products, no S. aureus was isolated. Methicillin-resistant S. aureus (MRSA) were not detected, but around 10% of the S. aureus isolates carried lukS-PV, a marker gene for the virulence factor Pantone-Valentine leucocidin (PVL), which has been associated with severe diseases in human. Molecular typing identified a total of 44 spa types including 13 novel types: t18396, t18397, t18398, t18399, t18400, t18402, t18416, t20459, t20460, t20461, t20462, t20463, and t20464. Furthermore, 12 novel multi-locus sequence types were identified: ST7012, ST7100, ST7101, ST7177, ST7291, ST7304, ST7305, ST7344, ST7596, ST7597, ST7598, and ST7599, of which ST7012, ST7177, and ST7596 fall into the bovine-associated clonal linage CC97. The spa types t084, t267, t355, and the novel type t20464 were common in all three study provinces. The predominant spa type varied depending on the province. Whole genome sequencing (WGS) and core genome multi-locus sequence typing (cgMLST) indicates transmission of strains along the Zambian dairy chain with possible persistence in the chain over time. cgMLST also revealed a very close relatedness between some isolates from milkers and from raw milk or milk buckets. The high prevalence and wide spa type diversity of S. aureus, as well as possible direct or indirect transmission of (potentially highly virulent) S. aureus to humans along the Zambian dairy value chain, are of public health concern, particularly as milk and milk products are often consumed raw by the Zambian population.

Effects of citronellal on growth and enterotoxins production in Staphylococcus aureus ATCC 29213

Staphylococcus aureus (S. aureus) is known to be one of the most common foodborne pathogens capable of secreting a wide range of exotoxins such as enterotoxin, which severely threatens the health of consumers. Over the past few years, the development of safe and effective strategies in inhibiting the growth and enterotoxins generation of S. aureus in food turns out to be the research focus and emphasis. This research explores citronellal (CIT), a native compound with extensive existence in spices, which could effectively inhibit the growth and enterotoxins generation of S. aureus (ATCC 29213). Results from minimal inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and time-kill curves, showed that CIT could tremendously inhibit the growth of S. aureus. Analysis on hemolysin showed that CIT at sub-MIC could significantly (p < 0.05) inhibit the hemolytic activity of S. aureus. As revealed by the results of ELISA, the production of enterotoxins in the culture supernatant and pork meat decreased significantly (p < 0.05) after exposure to CIT at sub-MIC. Furthermore, a significant (p < 0.05) decrease in dose-dependent was found in the transcription levels of virulence-related genes. In all, CIT proved to be a possible inhibitor of the growth and enterotoxins production of S. aureus with highly promising application in the food industry.

Reframing schizophrenia: Altering our perceptions?

Staphylococcus aureus (S. aureus) is known to be one of the most common foodborne pathogens capable of secreting a wide range of exotoxins such as enterotoxin, which severely threatens the health of consumers. Over the past few years, the development of safe and effective strategies in inhibiting the growth and enterotoxins generation of S. aureus in food turns out to be the research focus and emphasis. This research explores citronellal (CIT), a native compound with extensive existence in spices, which could effectively inhibit the growth and enterotoxins generation of S. aureus (ATCC 29213). Results from minimal inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and time-kill curves, showed that CIT could tremendously inhibit the growth of S. aureus. Analysis on hemolysin showed that CIT at sub-MIC could significantly (p < 0.05) inhibit the hemolytic activity of S. aureus. As revealed by the results of ELISA, the production of enterotoxins in the culture supernatant and pork meat decreased significantly (p < 0.05) after exposure to CIT at sub-MIC. Furthermore, a significant (p < 0.05) decrease in dose-dependent was found in the transcription levels of virulence-related genes. In all, CIT proved to be a possible inhibitor of the growth and enterotoxins production of S. aureus with highly promising application in the food industry.

Food safety inspection of tas kebab and salad processing line in a catering company

This study was conducted to evaluate the sufficiency of food safety practices in a catering company. The presence of some pathogenic and indicator bacteria was monitored in the samples collected from raw materials, food, food contact surfaces and workers' hands and various steps of the tas kebab (a Turkish meat stew) and salad processing lines. Bacillus cereus was found in ready-to-eat (RTE) tas kebab and RTE salad, while Listeria monocytogenes was isolated from RTE salad. Furthermore, it was observed that RTE salad contained coagulase-positive Staphylococcus aureus without staphylococcal enterotoxin production. The swab samples obtained from cutting board surfaces, knives and workers' hands contained high counts of total aerobic bacteria and some samples were contaminated with coliforms and coagulase-positive/negative staphylococci. The presence of B. cereus and L. monocytogenes in RTE foods is a serious threat to public health, especially in the catering business. Preventing the presence of toxin-producing bacteria in RTE food is a fundamental action. Also, the occurrence of L. monocytogenes in RTE salad and B. cereus in RTE tas kebab/salad samples showed insufficient cleaning/disinfection practices. As a result, hygiene practices and regular monitoring in the catering business are necessary for food safety.