Foodborne Pathogens In Raw Milk Research Articles

Prevalence and Characterization of Pathogenic Bacteria in Bulk Tank Raw Milk, Thailand

Although there are a number of raw milk collection centers in Nakhon Ratchasima, there is a lack of information with regard to the process of isolation and characterization of foodborne pathogens in raw milk. Therefore, the purpose of this research was to investigate the prevalence and characterization of foodborne pathogens, including Bacillus cereus, Escherichia coli, Listeria monocytogenes, Salmonella spp. and Staphylococcus aureus from 33 raw milk samples from 9 different raw milk collection centers located in 8 districts in Nakhon Ratchasima, Thailand. This study was conducted from January to March 2016. Results revealed that the contaminations of L. monocytogenes and Salmonella spp. were not detected in any of the raw milk samples tested. The prevalence of B. cereus, E. coli, and S. aureus in raw milk samples was found to be 9 % (10 - 2.0 ×104 CFU/ml), 42.4 and 54 % (85 - 2.7 ×104 CFU/ml), respectively. The distribution of virulence genes was tested in B. cereus and S. aureus using gene specific primers by polymerase chain reaction. Out of the 29 analyzed coagulase-positive S. aureus isolates, 27 isolates (93 %) were positive for eap gene amplification and 14 isolates (48 %) showed amplicon of eap gene and all 5 enterotoxin genes, including seG, seGV, seI, seIV, and seM genes. All 8 B. cereus isolates tested showed positive PCR result with enterotoxin FM (entFM) gene but they showed negative with hemolysin gene (hblA and hblD genes) amplifications. It was inferred from these findings that bulk tank milk is a potential source of S. aureus and B. cereus in milk.

Foodborne pathogens in raw milk and cheese of sheep and goat origin: a meta-analysis approach

This review compiles published information concerning the incidence of pathogenic microorganisms — Listeria monocytogenes, Salmonella spp., Staphylococcus aureus and shiga-toxin producing Escherichia coli (STEC) — in goat and sheep raw milk and cheese. Meta-analytical data were extracted from 37 primary studies undertaken in Australia, Brazil, China, Colombia, Costa Rica, Czech Republic, Egypt, Germany, Greece, Iran, Italy, Malaysia, Mexico, Norway, Poland, Portugal, Spain, Sweden, Switzerland, Turkey, UK and USA. Pooled frequencies of detection of pathogens were found to be similar for sheep and goat raw milk: Salmonella (1.4–2.4%), L. monocytogenes (2.9–3.6%), STEC (4.3–4.8%) and S. aureus (35–39%). Likewise, in goat cheeses, regardless of being made of raw or heat-treated milk, S. aureus has been the most frequent contaminant (16.0%), whereas in raw milk cheeses, regardless of origin, the pooled prevalence of S. aureus is equally high in hard (34.6%) and soft cheeses (25.7%). L. monocytogenes is another important pathogen in sheep and goat milk cheeses (3.6–12.8%) while E. coli O157 strains with virulence genes (4.3%) also appear to persist during cheese manufacture. As expected, STEC has a higher pooled incidence in raw milk cheeses (10.0%) than in pasteurised milk cheeses (4.7%). Thus, the moderate contamination in raw milk and cheese of sheep and goat origin, revealed by this meta-analysis, advocates the reinforcement of general prevention measures such as close monitoring of hygiene on farms and eradication of disease by sheep and goat dairy farmers. Moreover, for the production of traditional cheeses made of raw milk, preventive measures during processing, namely, regular sterilisation of dairy equipment, process monitoring and hygiene of operators, should be even more stringent.

The prevalence of Listeria monocytogenes and Staphylococcus aureus and their virulence genes in bulk tank milk in Kosovo.

Milk is considered to be a healthy, nutritious food product. Microbiological quality is an important aspect in evaluating the quality of milk. A total of 603 bulk tank milk samples from 221 farms distributed across ten different regions were collected for milk quality assessment. Quality was judged by total viable count, and the prevalence of two foodborne pathogens (Listeria monocytogenes and Staphylococcus aureus) by using selective media and 16S rRNA gene sequencing. The presence of virulence genes was detected by polymerase chain reaction (PCR) using specific primers. Milk from only 7% (15/221) of farms were found to comply with the European Union standard. Interestingly, the microbiological quality of milk from the larger herd size farms (more than 10 cows) was better than in smaller herds. L. monocytogenes was found in 2.7% (6/221) of farms, and all the examined L. monocytogenes isolates were positive with respect to the virulence genes prfA, actA, and hlyA. S. aureus was found in 39.8% (88/221) of the farms. In total, 30.7% (27/88) of the staphylococci were positive for enterotoxin production. The enterotoxins identified were toxin B (40.7%), toxin D (33.4%), toxin C (18.5%), and toxin A (7.4%). The total number of bacteria in milk was very high. The presence of two foodborne pathogens in raw milk represents a great health risk to consumers. To improve the microbial quality of milk in Kosovo, important measures to improve hygiene, including better information, guidance, and control, are needed.

Prevalence and characterization of foodborne pathogens from Australian dairy farm environments

The ability of foodborne pathogens to gain entry into food supply systems remains an ongoing concern. In dairy products, raw milk acts as a major vehicle for this transfer; however, the sources of pathogenic bacteria that contaminate raw milk are often not clear, and environmental sources of contamination or the animals themselves may contribute to the transfer. This survey examined the occurrence of 9 foodborne pathogens in raw milk and environments of 7 dairy farms (3 bovine, 3 caprine, and 1 ovine farm) in summer and autumn, in Victoria, Australia. A total of 120 samples were taken from sampling points common to dairy farms, including pasture, soil, feed, water sources, animal feces, raw milk, and milk filters. The prevalence of the Bacillus cereus group, Campylobacter, Clostridium perfringens, Cronobacter, Shiga-toxigenic Escherichia coli, Listeria, Salmonella, coagulase-positive staphylococci (CPS), and Yersinia enterocolitica across the farms was investigated. The 2 most prevalent bacteria, which were detected on all farms, were the B. cereus group, isolated from 41% of samples, followed by Cl. perfringens, which was isolated from 38% of samples. The highest occurrence of any pathogen was the B. cereus group in soil, present in 93% of samples tested. Fecal samples showed the highest diversity of pathogens, containing 7 of the 9 pathogens tested. Salmonella was isolated from 1 bovine farm, although it was found in multiple samples on both visits. Out of the 14 occurrences where any pathogen was detected in milk filters, only 5 (36%) of the corresponding raw milk samples collected at the same time were positive for the same pathogen. All of the CPS were Staphylococcus aureus, and were found in raw milk or milk filter samples from 6 of the 7 farms, but not in other sample types. Pathogenic Listeria species were detected on 3 of the 7 farms, and included 4 L. ivanovii-positive samples, and 1 L. monocytogenes-positive water sample. Shiga-toxigenic Escherichia coli were identified in fecal samples from 3 of the 7 farms and in a single raw milk sample. Cronobacter species were identified on 4 of the 7 farms, predominantly in feed samples. No Y. enterocolitica was detected. Results of this study demonstrate high standards of pathogen safety across the 7 farms, with a low incidence of pathogens detected in raw milk samples. Monitoring feed contamination levels may help control the spread of bacterial species such as Cl. perfringens and B. cereus through the farm environment, which is a natural reservoir for these organisms.

A rapid method for the detection of foodborne pathogens by extraction of a trace amount of DNA from raw milk based on amino-modified silica-coated magnetic nanoparticles and polymerase chain reaction

A method based on amino-modified silica-coated magnetic nanoparticles (ASMNPs) and polymerase chain reaction (PCR) was developed to rapidly and sensitively detect foodborne pathogens in raw milk. After optimizing parameters such as pH, temperature, and time, a trace amount of genomic DNA of pathogens could be extracted directly from complex matrices such as raw milk using ASMNPs. The magnetically separated complexes of genomic DNA and ASMNPs were directly subjected to single PCR (S-PCR) or multiplex PCR (M-PCR) to detect single or multiple pathogens from raw milk samples. Salmonella Enteritidis (Gram-negative) and Listeria monocytogenes (Gram-positive) were used as model organisms to artificially contaminate raw milk samples. After magnetic separation and S-PCR, the detection sensitivities were 8CFUmL−1 and 13CFUmL−1 respectively for these two types of pathogens. Furthermore, this method was successfully used to detect multiple pathogens (S. Enteritidis and L. monocytogenes) from artificially contaminated raw milk using M-PCR at sensitivities of 15 CFUmL−1 and 25 CFUmL−1, respectively. This method has great potential to rapidly and sensitively detect pathogens in raw milk or other complex food matrices.

Inactivation of foodborne pathogens in raw milk using high hydrostatic pressure

Plate counting, viability test, pulse field gel electrophoresis (PFGE) and transmission electron microscopy (TEM) were used to investigate the effect of high hydrostatic pressure (HHP) on Salmonella, Escherichia coli, Shigella and Staphyloccocus aureus in raw milk in order to determine the optimal inactivation conditions, and further understand the mechanisms of HHP on pathogens inactivation in food. The results exhibited that 300Mpa treatment with 30min duration at 25°C was the optimal condition for Salmonella, E. coli, Shigella and S. aureus inactivation. Damage of the cell wall, cell membrane and cytoplasmic components by high pressure treatment can be observed in TEM micrographs. The injured cells could not be recovered, the growth rate of survivors was much lower than that of the untreated cells. PFGE showed neither corresponding DNA bands with same molecular weight nor DNA bands with same brightness could be found in the lanes between HHP treated pathogens and untreated ones. The results indicated that HHP processing can be applied to inactivate pathogens in food, the inactivation is mainly due to cell membrane damage, cell wall rupture and chromosome DNA degradation.

A Survey of Foodborne Pathogens in Bulk Tank Milk and Raw Milk Consumption Among Farm Families in Pennsylvania

A 2-part study was conducted to determine the risk of exposure to human pathogens from raw milk. The first part of the study focused on determining raw milk consumption habits of dairy producers. A total of 248 dairy producers from 16 counties in Pennsylvania were surveyed. Overall, 105 (42.3%) of the 248 dairy producers consumed raw milk and 170 (68.5%) of the 248 dairy producers were aware of foodborne pathogens in raw milk. Dairy producers who were not aware of foodborne pathogens in raw milk were 2-fold more likely to consume raw milk compared with dairy producers who were aware of foodborne pathogens. The majority of dairy producers who consumed raw milk indicated that taste (72%) and convenience (60%) were the primary factors for consuming raw milk. Dairy producers who resided on the dairy farm were nearly 3-fold more likely to consume raw milk compared with those who lived elsewhere. In the second part of the study, bulk tank milk from the 248 participating dairy herds was examined for foodborne pathogens. Campylobacter jejuni (2%), Shiga toxin-producing Escherichia coli (2.4%), Listeria monocytogenes (2.8%), Salmonella (6%), and Yersinia enterocolitica (1.2%) were detected in the milk samples. Salmonella isolates were identified as S. enterica serotype Typhimurium (n = 10) and S. enterica serotype Newport (n = 5). Of the 248 bulk tank milk samples, 32 (13%) contained ≥1 species of bacterial pathogens. The findings of the study could assist in developing farm community-based educational programs on the risks of consuming raw milk.