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Anaerobic transfer of antibiotic resistance from Pseudomonas aeruginosa
Abstract:
Pseudomonas aeruginosa, an opportunistic pathogen that often initiates infections from a reservoir in the intestinal tract, may donate or acquire antibiotic resistance in an anaerobic environment. Only by including nitrate and nitrite in media could antibiotic-resistant and -sensitive strains of P. aeruginosa be cultured in a glove box isolator. These anaerobically grown cells remained sensitive to lytic phage isolated from sewage. After incubation with a phage lysate derived from P. aeruginosa 1822, anaerobic transfer of antibiotic resistance to recipients P. aeruginosa PS8EtBr and PS8EtBrR occurred at frequencies of 6.2 x 10(-9) and 5.0 x 10(-8) cells per plaque-forming unit, respectively. In experiments performed outside the isolator, transfer frequencies to PS8EtBr and PS8EtBrR were higher, 1.3 x 10(-7) and 6.5 x 10(-8) cells per plaque-forming unit, respectively. When P. aeruginosa 1822 was incubated aerobically with Escherichia coli B in medium containing nitrate and nitrite, the maximum concentration of carbenicillin-resistant E. coli B reached 25% of the total E. coli B population. This percentage declined to 0.01% of the total E. coli B population when anaerobically grown P. aeruginosa 1822 and E. coli B were combined and incubated in the glove box isolator. The highest concentration of the recipient population converted to antibiotic resistance occurred after 24 h of aerobic incubation, when an initially high donor/recipient ratio (>15) of cells was mixed. These data indicate that transfer of antibiotic resistance either by transduction between Pseudomonas spp. or by conjugation between Pseudomonas sp. and E. coli occurs under strict anaerobic conditions, although at lower frequencies than under aerobic conditions.
Insights
Antibiotic resistance transfer between Pseudomonas aeruginosa strains and with Escherichia coli occurs under anaerobic conditions. Frequencies are lower than aerobic transfer, but demonstrate resistance can spread in oxygen-limited environments.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Pseudomonas aeruginosa is an opportunistic pathogen originating from the intestinal tract.
- Antibiotic resistance can be transferred between bacteria, impacting treatment efficacy.
- Anaerobic environments, such as the gut, are potential sites for resistance gene exchange.
Purpose of the Study:
- To investigate the transfer of antibiotic resistance in Pseudomonas aeruginosa under anaerobic conditions.
- To compare anaerobic and aerobic conditions for antibiotic resistance transfer.
- To determine if Pseudomonas aeruginosa can donate or acquire antibiotic resistance anaerobically.
Main Methods:
- Culturing of Pseudomonas aeruginosa strains (antibiotic-resistant and -sensitive) under strict anaerobic conditions using nitrate and nitrite supplementation.
- Assessing the sensitivity of anaerobically grown cells to lytic phage.
- Measuring the frequency of antibiotic resistance transfer via transduction (Pseudomonas to Pseudomonas) and conjugation (Pseudomonas to Escherichia coli) under both anaerobic and aerobic conditions.
Main Results:
- Antibiotic resistance transfer between Pseudomonas aeruginosa strains occurred anaerobically at frequencies of 10^-9 to 10^-8 cells per plaque-forming unit.
- Transfer frequencies were higher under aerobic conditions (10^-7 to 10^-8 cells per plaque-forming unit).
- Conjugative transfer of carbenicillin resistance from Pseudomonas aeruginosa to Escherichia coli was significantly reduced under anaerobic conditions (0.01%) compared to aerobic conditions (25%).
Conclusions:
- Antibiotic resistance transfer, including transduction and conjugation, can occur under strict anaerobic conditions.
- Anaerobic transfer of antibiotic resistance is less frequent than aerobic transfer.
- These findings highlight the potential for antibiotic resistance spread in oxygen-limited environments, such as the intestinal tract.