Drought may promote antibiotic resistance in soil, study suggests

News brief

Lake in drought conditions — ACES / Bruce Dupree / Flickr cc

New research suggests drought conditions may promote elevated antibiotic resistance in soil microbes, researchers reported yesterday in Nature Microbiology.

To determine how drought might affect soil microbial communities, which have been the source of many antibiotics used in clinical medicine, scientists from the California Institute of Technology began by compiling five metagenomic datasets from four previous studies in which drought was the only variable. The datasets included cropland and grassland in California, a forest in Switzerland, and a wetland in China.

Their hypothesis, based on previous studies of arid soil, was that reduced soil water content brought on by drought might increase the concentration of natural antibiotics in the soil, which would in turn “intensify the selective pressure exerted by these compounds, leading to enrichment of both antibiotic producers and resistant taxa.”

In all five datasets, metagenomic analysis revealed that the relative abundance of antibiotic biosynthesis genes produced by soil bacteria was significantly higher under drought conditions. The enrichment became stronger the longer the drought endured and spanned multiple classes of antibiotics, including beta-lactams, macrolides, and aminoglycosides.

When the researchers exposed dried soil samples to a representative natural antibiotic (phenazine-1-carboxylic acid), they found that lower water content favored the growth of bacteria that were resistant to the antibiotic. In addition, they found that drought conditions also increased the abundance of antibiotic-resistance genes.

Greater aridity tied to clinical antibiotic resistance

Finally, using antibiotic resistance data from hospitals in 116 countries and corresponding local climate data, the researchers found that the average frequency of drug-resistant clinical isolates was higher in more arid locations.

“The strong correlation between aridity and clinical antibiotic resistance is concerning, given anticipated global climatic changes,” the study authors wrote.

Although more research is needed to demonstrate a causal relationship, the authors say the findings reveal an “underrecognized link between climate factors and antibiotic resistance.”

“These findings underscore the importance of integrating environmental and clinical perspectives within a unified One Health framework,” they concluded. “As climate instability intensifies, such integrative approaches will be critical for anticipating and mitigating the global trajectory of antibiotic resistance.”

South Carolina: No new measles cases in Upstate outbreak

News brief

Stephanie Soucheray, MA

measles on toddler torso — Marina Demidiuk/iStock

For the first time in months, South Carolina health officials said a week has gone by with no new measles cases in the state, and the state total remains just under 1,000 cases, at 997. Of those cases, 940 were recorded in Spartanburg County, the epicenter of the outbreak.

School children ages 5 to 17 represent 456 of the cases in the state, and 931 cases occurred in unvaccinated people. Twenty-five were fully vaccinated, 21 were partially vaccinated, and 20 have unknown status.

There are currently two people in quarantine and none in isolation.

Outbreak could be officially over at end of April

According to the Greenville News, the outbreak will be officially over on April 26 if no new cases are reported; that date will mark 42 days with no new cases, or two measles transmission cycles.

The South Carolina measles outbreak began last fall with cases seeded in several Christian academy elementary and middle schools with low vaccination rates among the student body.

The outbreak surpassed the West Texas measles outbreak, which began last year, in size and is one of the largest US measles outbreaks recorded in the last 40 years.

Small study finds promise in phage therapy for cystic fibrosis patients

News brief

Chris Dall, MA

Bacteriophage illustration — iLexx / iStock

Bacteriophage therapy for chronic bacterial respiratory infections appears to be safe and well-tolerated in cystic fibrosis (CF) patients, according to a study published yesterday in the International Journal of Infectious Diseases.

Because of the thick, sticky mucus that builds up in their lungs, CF patients are predisposed to chronic respiratory infections and colonization by intrinsically multidrug-resistant (MDR) pathogens like Pseudomonas aeruginosa. This requires repeated exposure to antibiotics, which accelerates the emergence of MDR strains and further limits treatment options.

As a result, CF patients have become prime candidates for treatment with bacteriophages, which are live viruses that specifically target and kill bacteria. But because phage therapy to date has been used only in limited circumstances, evidence on safety and efficacy is scarce.

“The heterogeneity in treatment protocols, outcome measures, and follow-up periods across existing studies limits the ability to draw definitive conclusions about the efficacy and safety of phage therapy in CF patients,” researchers from Italy and the United States wrote.

Larger studies needed

To evaluate current evidence, the researchers conducted a systematic review and meta-analysis of 19 studies involving 51 CF patients and 52 bacteriophage treatments, which were administered in conjunction with antibiotics. Among the included studies were two randomized controlled trials, six case series, and 11 case reports. Nearly half the patients (46%) had P aeruginosa infections. Other pathogens included Mycobacterium abscessus, Achromobacter spp, Burkholderia spp, and Staphylococcus aureus.

Overall microbiologic improvement, defined as bacterial load reduction in specimen cultures, was achieved in 35 of 51 patients (68.8%), and lung function improved in 20 of 27 patients (74.1%). Forty-one of 52 patients (78.8%) experienced no adverse events directly attributable to phage therapy. Two patients reported serious adverse events, but they were considered unlikely to be related to treatment.

The study authors say the results support “the potential for phage therapy as a versatile therapeutic platform in CF management,” but add that the small sample size and non-randomized evidence “necessitate cautious interpretation and underscore the critical need for larger, well-designed randomized clinical trials with standardized outcomes and extended follow-up to confirm these promising preliminary results.”

Indiana: More than 350,000 birds killed in massive avian flu outbreak

News brief

Stephanie Soucheray, MA

table egg layer facility — UGA CAES Extension, John Amis / Flickr cc

Since the beginning of the month, more than 350,000 birds in Indiana have died from avian flu and response measures, and agricultural officials in the state are asking producers to be vigilant to stop the virus from spreading.

“We need sound biosecurity practices. It’s not just what’s happening on that one facility, there’s risk of lateral transmissions,” Dudley Hoskins, JD, the state’s under secretary of agriculture for marketing and regulatory programs, said in a press release.

It’s not just what’s happening on that one facility, there’s risk of lateral transmissions.

Over 10 million Indiana birds have been depopulated since February 2022 due to bird flu. This month’s frequent detections and cullings have included ducks, chickens, and table egg facilities, many in LaGrange and Elkhart counties.

No cattle infected—yet

While no cattle in Indiana have been infected with H5N1 yet, experts caution the virus could easily reach other agricultural animals and livestock.

The state said that although individual farms are devastated after an outbreak, overall poultry production in Indiana is strong. Indiana ranks first in duck production, third in eggs, and third in turkey production and is a significant producer of broilers.

In the past week, there have been three detections of avian flu in Indiana involving roughly 55,000 birds.