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Antibiotic resistance transfer from nonpathogenic to pathogenic bacteria
Abstract:
Alcaligenes species is a common contaminant of "wet" environmental areas on the surgical ward. Although thought to be a nonpathogenic organism, recent clinical experience on the burn and trauma service has led us to believe that antibiotic resistance transfer may occur between Alcaligenes and Pseudomonas aeruginosa. To evaluate this possibility, germ-free mice were contaminated with Alcaligenes species, which quickly established in the animals' gastrointestinal tracts. These animals then were burned and the wound was seeded with additional Alcaligenes. After 72 hours the average bacterial count was 4.5 X 10(6) cells/gm of tissue, and all animals survived. Ten additional germ-free mice were contaminated with a resistant (Amikacin, tobramycin, gentamicin, and Sisomicin) Alcaligenes species. When a Pseudomonas aeruginosa strain sensitive to these antibiotics was introduced into the environment, it rapidly overgrew the Alcaligenes species but developed resistance to those four antibiotics to which it had been sensitive previously. These animals were then subjected to a 10 second immersion burn, and the wound was seeded with the same strain of Alcaligenes. The Pseudomonas quickly overgrew the Alcaligens on the burn wound and became established, with an average count being 5.2 X 10(8) cells/gm of tissue. When this experiment was repeated, establishing antibiotic sensitive Pseudomonas in the germ-free animals prior to inoculation of resistant Alcaligenes, the R-transfer again occurred but required a longer time.
Insights
Alcaligenes species can transfer antibiotic resistance to Pseudomonas aeruginosa in burn wound infections. This study demonstrates how this nonpathogenic bacteria can lead to resistant infections in susceptible patients.
Area of Science:
- Microbiology
- Infectious Diseases
- Wound Care
Background:
- Alcaligenes species are common contaminants in healthcare settings.
- Traditionally considered nonpathogenic, clinical observations suggest potential for antibiotic resistance transfer.
Purpose of the Study:
- To investigate the potential for antibiotic resistance transfer from Alcaligenes species to Pseudomonas aeruginosa.
- To evaluate the role of Alcaligenes in the development of resistant burn wound infections.
Main Methods:
- Germ-free mice models were used to establish gastrointestinal and wound colonization with Alcaligenes species.
- Pseudomonas aeruginosa strains with known antibiotic sensitivities were introduced to assess resistance acquisition.
- Burn injuries were inflicted and wounds seeded to mimic clinical scenarios.
Main Results:
- Pseudomonas aeruginosa acquired resistance to amikacin, tobramycin, gentamicin, and sisomicin after co-colonization with resistant Alcaligenes species.
- In burn wound models, Pseudomonas aeruginosa overgrew Alcaligenes and developed resistance, with high bacterial counts observed.
- Resistance transfer occurred regardless of the initial colonization order, though it was slower when sensitive Pseudomonas was introduced first.
Conclusions:
- Alcaligenes species can act as a reservoir for antibiotic resistance genes, facilitating transfer to opportunistic pathogens like Pseudomonas aeruginosa.
- This transfer mechanism poses a significant risk for the development of multidrug-resistant infections in immunocompromised patients, particularly in burn units.
- Further research is warranted to understand the clinical implications and develop strategies to prevent such resistance transfer events.