Nutrient-Limited Conditions May Dramatically Alter Antibiotic Effectiveness

Standard antimicrobial susceptibility testing is typically performed using nutrient-rich laboratory media, but new research suggests those conditions may not accurately reflect the environments bacteria encounter during infection. According to Rachana Rao Battaje, PhD, a postdoctoral fellow at Rutgers University, evaluating bacterial responses under nutrient-limited conditions could improve understanding of antibiotic performance in real-world infections.

She spoke to Contagion at the recent ASM Microbe in Washington DC, where she presented her study examining how nutrient limitation drives antibiotic response in E Coli.

Rather than examining a single nutrient limitation, the investigators evaluated bacterial responses under carbon limitation, nitrogen limitation, and simultaneous carbon-nitrogen co-limitation. The findings showed that antibiotic susceptibility differed substantially depending on the specific nutrient environment.

"If we only look at nutrient-rich media, we are missing a critical part of the picture. This might explain why some of the laboratory results that we see do not actually give the clinical outcomes that we expect," Rao Battje said.

The study also demonstrated contrasting responses to different antibiotic classes. Susceptibility to aminoglycosides increased under nitrogen-limited conditions, while tolerance to ciprofloxacin increased during carbon limitation. Rao Battaje explained that the findings challenge the long-held assumption that nutrient-poor environments uniformly make bacteria more tolerant to antibiotics.

According to Rao Battaje, nitrogen limitation and aminoglycosides both impair protein synthesis, creating a compounded effect that increases bacterial susceptibility. In contrast, carbon limitation slows bacterial growth and DNA replication, reducing the availability of ciprofloxacin's molecular target and allowing bacteria to better tolerate treatment.

One of the study's most unexpected findings was that certain antibiotics appeared to increase bacterial biomass under specific carbon-limited and co-limited conditions, suggesting that bacteria may undergo metabolic adaptations that improve survival under simultaneous stresses.

"That was one of the most striking results from our study because we expected that the bacterial response to antibiotics would reduce, but we didn't expect this opposite kind of effect, where you know what doesn't kill you makes you stronger. What we're able to see is that under certain nutrient-limited conditions, including co-limitation, that the antibiotics are not just failing to kill the bacteria, but it appears that they are actually promoting the growth, so it shows that there's some kind of compensatory response, like this cell is reshuffling some of its resources to handle one stress, which is enabling it to handle the other stress much better,” Rao Battaje said.

Rao Battaje said future work will focus on integrating multiple "omics" approaches to better understand the metabolic pathways responsible for these unexpected responses.

“We need to look at the mechanism, like what's happening within the cell, which includes looking at proteomics and transcriptomics to see how the proteins and what functional pathways are getting enhanced or inhibited. We can also look at metabolomics, which is to see what metabolites are getting enhanced, which is helping it you know compensate the other stress. It could be antibiotic versus nutrient limitation,” she said.

Such studies may improve antimicrobial susceptibility testing and help bridge the gap between laboratory findings and clinical outcomes.

Reference
Perish or Prosper: Nutrient Limitation Drives Antibiotic Response in E. Coli. Rao Battaje R. Presented at ASM Microbe 2026. June 4-7, 2026. Washington DC.