Tag: milk

Categories : AntibioticsTags : 13/11/25antibiotic resistancemilk

Study Finds High Rates of Antibiotic-resistant Bacteria in Raw Milk

On November 13, 2025November 13, 2025 By ModernMedia

In Pakistan, 50% of strains of a common milk bacterium, Staphylococcus epidermidis, were multi-drug resistant

Raw cow and sheep milk is frequently contaminated with antibiotic-resistant bacteria that could pose a threat to human and animal health, reports a new study led by Tahir Usman of Abdul Wali Khan University Mardan, Pakistan, published November 12, 2025 in the open-access journal PLOS One.

In Pakistan, over 95% of milk is consumed in its raw form, which has not been pasteurized to kill off harmful bacteria. Milk can become contaminated by bacteria through improper handing or from infections in the teat, called subclinical mastitis. The overuse of antibiotics to treat subclinical sumastitis has led to the emergence of multidrug-resistant bacterial strains, which could then be transmitted to humans through raw milk.

In the new study, researchers investigated the risk posed by Staphylococcus epidermidis, a subclinical mastitis-causing bacteria that often does not lead to visible symptoms in the cow, but results in contaminated, lower-quality milk. They collected 310 milk samples, about half from cattle and half from ewes, and tested them for subclinical mastitis. They also isolated strains of Staphylococcus epidermidis from the milk samples and screened them for antibiotic resistance. About one quarter of the samples showed evidence of subclinical mastitis and almost 13% (1 in 8) were contaminated with Staphylococcus epidermidis. Strikingly, 95% of Staphylococcus epidermidis bacteria isolated from the milk were resistant to penicillin and erythromycin, and half were resistant to three or more antibiotics.

In humans, Staphylococcus epidermidis is a common, generally harmless inhabitant of the skin, but the researchers point out that multi-drug resistant Staphylococcus epidermis bacteria in raw milk could spread antimicrobial resistance to more harmful pathogens, like Staphylococcus aureus, the MRSA pathogen.

The study’s findings underscore the high rates of subclinical mastitis in cattle and ewes, and indicate that Staphylococcus epidermidis might be an important pathogen impacting both animal health and food safety. The high rates of antibiotic resistance observed in the samples also emphasize the urgent need for improved antibiotic stewardship in agriculture to prevent the rise of multi-drug resistant strains.

The authors add: “The presence of multidrug-resistant Staphylococcus epidermidis in raw milk highlights how on-farm antibiotic use directly shapes public health risks. These findings emphasize the urgent need for responsible antibiotic use and improved hygiene practices in the dairy sector to reduce the risk of antimicrobial resistance transmission through the food chain.”

Provided by PLOS

Categories : AntibioticsTags : 24/5/24antibiotic resistancemilk

Milk Samples From the 1940s Reveal Antibiotic Resistance in the Pre-antibiotic Era

On May 24, 2024May 24, 2024 By ModernMedia

Using stored milk samples as a kind of time capsule, veterinary researchers at the University of Connecticut have uncovered insights about the presence of antibiotic resistance even in the pre-antibiotic era.

Sometime in the 1940s or so, someone in what is now the Department of Pathobiology and Veterinary Science got a lyophiliser, a piece of equipment that freeze-dries samples, says Director of the Connecticut Veterinary Medical Diagnostic Laboratory (CVMDL) Dr Guillermo Risatti. Risatti explains that at that time, the microbiology lab was very active in testing milk for the dairy farms in the region. With an exciting new piece of equipment, it seems they started lyophilising hundreds of samples.

The samples have been in storage ever since. Beyond the scant details that these are milk samples containing Streptococcus bacteria from the 1940s, Risatti explains that he and his colleagues – CVMDL Research Associate Dr. Zeinab Helal, Ji-Yeon Hyeon and Dong-Hun Lee – were interested in exploring their microbial history.

Risatti says that over the years, the data was lost, so researchers don’t have precise details of the provenance of the samples. But knowing a bit of history about the department, they can deduce some information.

“We believe that most of them came from Connecticut or perhaps from cases from the region, but we cannot say which parts,” Risatti says. “Most likely, this lab provided a testing service to locals, as this was mainly a pathology lab. Now it’s more like a diagnostic lab, and we receive samples from all over the region, including New York and New Jersey.”

Learning about what these historical samples hold could help with research in unexpected ways, but the first step is piecing together the lost details. To do this, Risatti explains that the team established a workflow using standard techniques to streamline processes to analyse the visual characteristics, called phenotype, and to analyse their genotype with genomic sequencing.

Different species of Streptococcus use different strategies to inflict disease in the organisms they infect. These virulence factors are used to differentiate one species of Streptococcus from another and are one way to distinguish samples through phenotypic analysis. Another phenotypic analysis includes testing bacteria for their susceptibility to antibiotics.

The researchers started with 50 samples collected from 1941 to 1947, and they found that the samples contained seven different Streptococcus species, including two subspecies of S. dysgalactiae. Interestingly, the researchers found some of the samples were resistant to the antibiotic tetracycline and did not carry antibiotic resistance genes typically seen in today’s antibiotic-resistant bacterial strains. Since these samples were collected prior to the antibiotic era, the results add to a growing body of literature showing that antibiotic resistance occurred naturally before humans discovered and began to use antibiotics.

“Antibiotic resistance is a very big area of research, and it has been for many years,” says Risatti. “We did not go any further with our analysis because we don’t have the tools here, but we hope to bring this information to the public. I think it could be the jumpstart for somebody to study further.”

Risatti explains the hope is to partner with large agencies like the CDC and the Department of Public Health to help bolster antibiotic resistance research.