Investigating the collateral effects of antibiotics

November 1, 2017, American Society for Microbiology
Salmonella forms a biofilm. Credit: CDC

Antibiotics can influence the swimming and swarming ability of multidrug-resistant bacteria, according to a new study in mSphere, an open-access journal of the American Society for Microbiology. The study, conducted using multidrug-resistant Salmonella, explored how antibiotics may modulate Salmonella virulence mechanisms.

"Understanding the influence of antibiotics on multidrug-resistant bacteria is critical to the proper selection and prudent use of antibiotics while minimizing potential collateral consequences," said co-author Bradley Bearson, PhD, a microbiologist at the National Laboratory for Agriculture and the Environment, part of the United States Department of Agriculture Agricultural Research Service (USDA-ARS).

For several years, researchers at the USDA-ARS have been investigating the consequences of antibiotic exposure on Salmonella, including multidrug-resistant strains. "While antibiotics are important drugs to prevent and cure disease in humans and animals, the drugs can sometimes have unintentional side effects both detrimental and beneficial," said Dr. Bearson. "We have been trying to investigate some of the potential collateral effects."

In the new study, researchers evaluated the influence of four different antibiotics (chloramphenicol, kanamycin, streptomycin, or tetracycline) on bacterial motility in six different multidrug-resistant Salmonella strains. The six isolates were resistant to ampicillin, chloramphenicol, streptomycin and tetracycline, and three isolates were also resistant to kanamycin.

Motile bacteria use one or more methods to move around, including darting, gliding, sliding, swarming, swimming and twitching. The researchers exposed the bacteria to sub-inhibitory concentrations of the antibiotics while they evaluated motility. Sub-inhibitory concentrations used in this study would inhibit antibiotic sensitive Salmonella isolates, but don't decrease or inhibit the growth of the multidrug-resistant strains.

The researchers discovered that chloramphenicol and tetracycline reduced both swimming and swarming, though the effect was more pronounced for swimming than for swarming. Kanamycin and streptomycin limited swimming, but had less of an effect on decreasing swarming. In one strain, kanamycin significantly increased swarming.

"We found that most of the antibiotics decreased bacterial motility in multidrug-resistant Salmonella, but kanamycin increased the motility in one of the bacterial isolates," said Dr. Bearson. "Since this was surprising, we went on to dig deeper and found that the kanamycin resistance-gene was important, meaning if we put a different kanamycin resistance-gene in the bacterial cell, it didn't enhance the motility like the original gene did. We also found there are some accessory genes in the bacteria that are also required to see that phenotype, but we don't know what those genes are at this point."

Dr. Bearson said that going forward, his lab will try to identify those genes that are involved in the kanamycin enhanced swarming that are not due to the . "We will do some gene expression studies to try to identify the accessory that are involved," said Dr. Bearson.

The researchers say that while antibiotics are valuable tools in human and animal medicine, a better understanding of the potential benefits and negative consequences of their usage is needed. "We are trying to assimilate information about these consequences that would allow physicians and veterinarians to make informed decisions about their antibiotic choice," said Dr. Bearson. For example, he said, if clinicians have two that will equally treat a disease in a human or animal, it might be more prudent to use the antibiotic that has an additional beneficial effect or avoid an antibiotic that might have a negative impact.

Salmonella is one of the most common causes of bacterial foodborne infections in the United States. The Centers for Disease Control and Prevention considers multidrug-resistant Salmonella a serious threat to public health.

Explore further: Addressing superbug resistance with phage therapy

Related Stories

Addressing superbug resistance with phage therapy

August 16, 2017
International research involving a Monash biologist shows that bacteriophage therapy – a process whereby bacterial viruses attack and destroy specific strains of bacteria - can be used successfully to treat systemic, multidrug ...

Integrons hold key to antibiotic resistance crisis

August 12, 2014
In Mexico the sale of antibiotics for human consumption is controlled to prevent misuse, although in the veterinary sector failure in the implementation of the Official Mexican Standard NOM-064-ZOO-2000, "Guidelines for veterinarian ...

Resistance to antibiotics and to immune system are interconnected in bacteria

June 30, 2016
Antibiotics and the immune system are the two forces that cope with bacterial infections. Now, two studies from Isabel Gordo's laboratory, at Instituto Gulbenkian de Ciência (IGC, Portugal), show for the first time that ...

Recommended for you

Study predicts 2018 flu vaccine will have 20 percent efficacy

April 19, 2018
A Rice University study predicts that this fall's flu vaccine—a new H3N2 formulation for the first time since 2015—will likely have the same reduced efficacy against the dominant circulating strain of influenza A as the ...

Zika presents hot spots in brains of chicken embryos

April 19, 2018
Zika prefers certain "hot spots" in the brains of chicken embryos, offering insight into how brain development is affected by the virus.

Low-cost anti-hookworm drug boosts female farmers' physical fitness

April 19, 2018
Impoverished female farm workers infected with intestinal parasites known as hookworms saw significant improvements in physical fitness when they were treated with a low-cost deworming drug. The benefits were seen even in ...

Super-superbug clones invade Gulf States

April 18, 2018
A new wave of highly antibiotic resistant superbugs has been found in the Middle East Gulf States, discovered by University of Queensland researchers.

Of mice and disease: Antibiotic-resistant bacteria discovered in NYC house mice

April 17, 2018
A study by scientists at the Center for Infection and Immunity (CII) at Columbia University's Mailman School of Public Health finds New York City house mice carry bacteria responsible for mild to life-threatening gastroenteritis ...

Discovery explains how the chickenpox and shingles virus remains dormant

April 16, 2018
A research team led by UCL and Erasmus University has found a missing piece to the puzzle of why the virus that causes chickenpox and shingles can remain dormant for decades in human cells.

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

nikoloushli
not rated yet Dec 02, 2017
Ampicillin is a broad spectrum of action. The drug of choice in women with chlamydial infection. Affordable pricing policy and positive treatment results. When creating a high inflammation in the focus of inflammation has a bactericidal effect. Description and instructions on the site norxtabs.com/buy-generic-ampicillin-online.php

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.