Staphylococcus aureus, Escherichia coli, and Klebsiella spp. prevalence in bulk tank milk of Colombian herds and associated milking practices

Phytochemical Screening, Antibacterial Activity, and Toxicity of Calathea lutea Leaf Extracts

In Colombia, there is a long tradition of using bijao (Calathea lutea) leaves to package or wrap various foods. However, scientific studies on C. lutea are limited, and research to evaluate its toxicity and/or antibacterial activity has not yet been conducted. The objective of this research, therefore, was to evaluate the content of phytochemical compounds, levels of toxicity, and antibacterial activity of the extracts, fractions, and essential oil derived from C. lutea leaves. The plant material was subjected to extraction by maceration, Soxhlet extraction, and steam distillation, and fractions of hexane, dichloromethane, ethyl acetate, and a residual ethanol-water fraction were obtained. Preliminary phytochemical screening was performed using standard procedures with staining reagents. Estimation of the toxicity was carried out using the Caenorhabditis elegans biological model. Antibacterial activity was determined by broth microdilution against Staphylococcus aureus and Escherichia coli. The results showed that the characteristic metabolites were flavonoids, triterpenes, and tannins. At the concentrations tested, the extracts, fractions, and essential oil showed minimal toxicity levels. In terms of antibacterial activity, E. coli showed no susceptibility; meanwhile, the dichloromethane fraction had high antibacterial activity against S. aureus, with a growth inhibition rate of 81.2%. The results suggested that the of dichloromethane fraction of C. lutea has antibacterial activity against S. aureus, suggesting its potential as a possible candidate as a natural antibacterial agent in the food industry. This alternative could offer a safer and more sustainable solution compared to the conventional synthetic preservatives.

Extended-spectrum beta-lactamase-producing Klebsiella pneumoniae and risk factors associated with high total bacterial count in bulk tank milk from dairy farms in Colombia

The objective of the study was to evaluate the frequency and genetic characteristics of ESBL-producing Escherichia coli and Klebsiella spp. and the risk factors associated with a high total bacterial count in bulk tank milk samples of dairy farms in three municipalities of the Antioquia Department, Colombia. Fifteen samples were positive for E. coli and Klebsiella spp. Subsequent analysis of the 16 S rRNA gene sequences confirmed these isolates included E. coli (n = 3), K. oxytoca (n = 11), and K. pneumoniae (n = 1). None of the isolates was positive for ESBL identification by phenotypic methods, but the only the isolate of K. pneumoniae was positive for the blaSHV61 gene by sequence analysis. The antibiotic susceptibility evaluation for all Klebsiella spp. isolates identified resistance to fosfomycin (50%; 6/12) and ampicillin (100%; 12/12). While most of the herds maintain adequate hygienic quality, specific risk factors such as having more than 60 milking cows, frequent changes in milkers, milking in paddocks, and using a chlorinated product for pre-dipping have been identified as associated with a high total bacterial count > 100,000 CFU/mL in bulk tank milk. However, certain variables including the milker being the owner of the animals and the proper washing and disinfection of the milking machine contribute to maintain a high level of hygiene and quality in the raw milk stored in the tanks. In conclusion, the frequency of ESBL producers was relatively low, with only K. pneumoniae testing positive for the blaSHV ESBL type. The presence of these bacteria in milk tanks represents a potential risk to public health for consumers of raw milk and its derivatives.

Microbial diversity in camel milk from Xinjiang, China as revealed by metataxonomic analysis

The quality of raw camel milk is affected by its bacterial composition and diversity. However, few studies have investigated the bacterial composition and diversity of raw camel milk. In this study, we obtained 20 samples of camel milk during spring and summer in Urumqi and Hami, Xinjiang, China. Single-molecule real-time sequencing technology was used to analyze the bacterial community composition. The results revealed that there were significant seasonal differences in the bacterial composition and diversity of camel milk. Overall, Epilithonimonas was the most abundant bacterial genus in our samples. Through the annotated genes inferred by PICRUSt2 were mapped against KEGG database. Non-parametric analysis of the bacterial community prediction function revealed a strong bacterial interdependence with metabolic pathways (81.83%). There were clear regional and seasonal differences in level 3 metabolic pathways such as fat, vitamins, and amino acids in camel milk. In addition, we identified lactic acid bacteria in camel milk with antibacterial and anti-tumor activities. Our findings revealed that camel milk from Xinjiang had serious risk of contamination by psychrophilic and pathogenic bacteria. Our research established a crucial theoretical foundation for ensuring the quality and safety of camel milk, thereby contributing significantly to the robust growth of China's camel milk industry.