The effect of multiplex-PCR-assessed major pathogens causing subclinical mastitis on somatic cell profiles

Microbial Properties of Raw Milk throughout the Year and Their Relationships to Quality Parameters

Raw milk microbiota is complex and influenced by many factors that facilitate the introduction of undesirable microorganisms. Milk microbiota is closely related to the safety and quality of dairy products, and it is therefore critical to characterize the variation in the microbial composition of raw milk. In this cross-sectional study, the variation in raw milk microbiota throughout the year (n = 142) from three farms in China was analyzed using 16S rRNA amplicon sequencing, including α and β diversity, microbial composition, and the relationship between microbiota and milk quality parameters. This aimed to characterize the contamination risk of raw milk throughout the year and the changes in quality parameters caused by contamination. Collection month had a significant effect on microbial composition; microbial diversity was higher in raw milk collected in May and June, while milk collected in October and December had the lowest microbial diversity. Microbiota composition differed significantly between milk collected in January−June, July−August, and September−December (p < 0.05). Bacterial communities represented in raw milk at the phylum level mainly included Proteobacteria, Firmicutes and Bacteroidota; Pseudomonas, Acinetobacter, Streptococcus and Lactobacillus were the most common genera. Redundancy analysis (RDA) found strong correlations between microbial distribution and titratable acidity (TA), fat, and protein. Many genera were significantly correlated with TA, for example Acinetobacter (R = 0.426), Enhydrobacter (R = 0.309), Chryseobacterium (R = 0.352), Lactobacillus (R = −0.326), norank_o__DTU014 (R = −0.697), norank_f__SC-I-84 (R = −0.678), and Subgroup_10 (R = −0.721). Additionally, norank_f__ Muribaculaceae was moderately negatively correlated with fat (R = −0.476) and protein (R = −0.513). These findings provide new information on the ecology of raw milk microbiota at the farm level and contribute to the understanding of the variation in raw milk microbiota in China.

Simultaneous Detection of Four Main Foodborne Pathogens in Ready-to-Eat Food by Using a Simple and Rapid Multiplex PCR (mPCR) Assay

The increasing consumption of organic or ready-to-eat food may cause serious foodborne disease outbreaks. Developing microbiological culture for detection of food-borne pathogens is time-consuming, expensive, and laborious. Thus, alternative methods such as polymerase chain reaction (PCR) are usually employed for outbreaks investigation. In this work, we aimed to develop a rapid and simple protocol for the simultaneous detection of Escherichia coli (E coli), Listeria monocytogenes (L. monocytogenes), Staphylococcus aureus (S. aureus) and Salmonella enterica (S. enterica), by the combination of an enrichment step in a single culture broth and a multiplex PCR (mPCR) assay. The effectiveness of several enrichment media was assessed by culture and PCR. Buffered peptone water (BPW) was selected as the optimum one. Then, mPCR conditions were optimized and applied both to pure co-cultures and artificially inoculated food samples (organic lettuce and minced meat). In the culture medium inoculated at 10⁰ CFU/mL, mPCR was able to detect the four microorganisms. When performed on artificially food samples, the mPCR assy was able to detect E. coli, S. enterica, and L. monocytogenes. In conclusion, BPW broth can effectively support the simultaneous growth of E. coli, S. aureus, L. monocytogenes, and S. enterica and could be, thus, used prior to a mPCR detection assay in ready-to-eat food, thereby considerably reducing the time, efforts and costs of analyzes.

Application of culture, PCR, and PacBio sequencing for determination of microbial composition of milk from subclinical mastitis dairy cows of smallholder farms

Mastitis is a cow disease usually signalized by irritation, swelling, and soreness of the udder. It is characterized by physical, chemical, and biological changes in the udder and milk. The aim of this study was to detect and characterize pathogens causing subclinical mastitis (SCM) from the milk of dairy cows of small-scale farmers through culture and molecular techniques. Milk was collected from 32 cows belonging to 8 small-scale farmers around Harrismith District, South Africa. The results showed that screening of SCM by California mastitis test and somatic cell counts (SCC) was 21.87 and 25%, respectively. Culture methods revealed the presence of Staphylococcus aureus at 93% followed by Streptococci spp. and Escherichia coli at 36.4 and 13.3%, respectively. The PCR could only detect E. coli, while single-molecule real-time sequencing showed a total of 2 phyla, 5 families, 7 genera, and 131 species. Clostridiaceae was the most abundant family, while Romboutsia was the most abundant genus followed by Turicibacter spp. The present study has documented the occurrence of SCM causing pathogens in milk collected from cows of small-scale farmers in Harrismith, indicating that SCM may be present at higher levels than expected.