Tag: milk

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

Photo by Robin Worrall on Unsplash

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.

Milk Consumption Does Not Raise Cholesterol Levels

Photo by ROBIN WORRALL on Unsplash

Regular consumption of milk is not associated with increased levels of cholesterol, according to new research.

A study published in the International Journal of Obesity analysed three large population studies and found that people who regularly drank high amounts of milk had lower levels of both ‘good’ and ‘bad’ cholesterol, although their BMI levels were higher than non-milk drinkers. Analysis of other large studies also suggests that regular milk drinkers had a 14% lower risk of coronary heart disease.

The team of researchers took a genetic approach to milk consumption by looking at a variation in the lactase gene associated with digestion of lactose. The study found that this gene variation for digesting lactose was a good identifier for people who consumed higher levels of milk.

“We found that among participants with a genetic variation that we associated with higher milk intake, they had higher BMI, body fat, but importantly had lower levels of good and bad cholesterol,” said Vimal Karani, Professor of Nutrigenetics and Nutrigenomics at the University of Reading said. “We also found that those with the genetic variation had a significantly lower risk of coronary heart disease. All of this suggests that reducing the intake of milk might not be necessary for preventing cardiovascular diseases.”

Contradictory research on the effect of high dairy intake and obesity and metabolic disorders was the motivation for the study. To exclude the effects of differences in sampling size, ethnicity and other factors, the team conducted a meta-analysis of data in up to 1.9 million people, including the UK Biobank and used the genetic approach to avoid confounding.

Even though the UK Biobank data showed that those with the lactase gene had an 11% reduced risk of type 2 diabetes, the study did not find a link between higher milk intake and increased likelihood of diabetes or related traits, such as glucose and inflammatory biomarkers.

“The study certainly shows that milk consumption is not a significant issue for cardiovascular disease risk even though there was a small rise in BMI and body fat among milk drinkers. What we do note in the study is that it remains unclear whether it is the fat content in dairy products that is contributing to the lower cholesterol levels or it is due to an unknown ‘milk factor’,” said Professor Karani.

Source: EurekaAlert

Journal information: Karani Santhanakrishnan Vimaleswaran et al, Evidence for a causal association between milk intake and cardiometabolic disease outcomes using a two-sample Mendelian Randomization analysis in up to 1,904,220 individuals, International Journal of Obesity (2021). DOI: 10.1038/s41366-021-00841-2