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Resistance due to aminoglycoside modifying enzymes in Pseudomonas aeruginosa isolates from burns patients
1Department of Microbiology, J.N. Medical College & Hospital, Aligarh Muslim University, Aligarh, India. shahidsahar@yahoo.co.in
Background & Objective:
Enzymatic modifications of aminoglycosides result in high-level resistance in numerous bacterial species. However, the data on this aspect are elementary in our country. The present study was therefore designed to determine resistance rates and patterns, and to find out the prevalent aminoglycoside modifying enzymes (AMEs) in clinical isolates of Pseudomonas aeruginosa from hospitalized burn patients.
Methods:
Forty two, non-repeat, clinical isolates of P. aeruginosa obtained during a period from February to July 2003, were analysed for the presence of antibiotics resistance. On the basis of aminoglycoside susceptibility patterns, resistance phenotypes and possible AMEs were inferred according to interpretative reading. Seven isolates collected during the same period and previously characterized to harbour a 48.5 kb plasmid, encoding multiple drug resistance, were also analysed for aminoglycoside susceptibility patterns, and AMEs encoded by the plasmid were inferred.
Results:
Ninety six per cent of the isolates were multi drug-resistant and majority (71.4%) were resistant to 5 or more antibiotics. Markedly high resistance to tobramycin (83.6%) and amikacin (55.1%) was noted, whereas gentamicin resistance was present in 32.6 per cent isolates. The enzyme N-acetyl transferases (AAC) viz. AAC(6')-I was the most common isolated AME followed by AAC(3)-II in 42.8 and 20.4 per cent of isolates respectively. The plasmid harbouring isolates belonged to AAC(6') phenotype and the enzyme encoded was inferred to be AAC(6')-I.
Interpretation & Conclusion:
Markedly high resistance to tobramycin and amikacin was noted in the present study. AAC(6')-I was the most common AME and was inferred to be plasmid encoded in R-plasmid harbouring isolates. This is among the premier reports regarding the aminoglycoside resistance due to AMEs especially plasmid encoded, in P. aeruginosa from India. Further studies are required from different parts of the country to findout the prevalence of aminoglycoside resistance due to AMEs in P. aeroginosa isolates.
Insights
High rates of aminoglycoside resistance, particularly to tobramycin and amikacin, were found in Pseudomonas aeruginosa from burn patients. The N-acetyltransferases (AAC) enzyme, specifically AAC(6')-I, was the most prevalent aminoglycoside modifying enzyme (AME).
Area of Science:
- Clinical microbiology and infectious diseases
- Antimicrobial resistance mechanisms
- Molecular epidemiology of bacterial pathogens
Background:
- Enzymatic modification of aminoglycosides is a significant cause of bacterial resistance.
- Data on aminoglycoside resistance and modifying enzymes in India are limited.
- Pseudomonas aeruginosa is a common opportunistic pathogen, especially in burn patients.
Purpose of the Study:
- To determine aminoglycoside resistance rates and patterns in clinical isolates of Pseudomonas aeruginosa from hospitalized burn patients in India.
- To identify the prevalent aminoglycoside modifying enzymes (AMEs) responsible for resistance in these isolates.
- To investigate the potential plasmid-borne nature of AMEs.
Main Methods:
- Analysis of 42 non-repeat clinical isolates of Pseudomonas aeruginosa for antibiotic resistance.
- Inference of resistance phenotypes and aminoglycoside modifying enzymes (AMEs) based on susceptibility patterns.
- Characterization of 7 previously identified multi-drug resistant, plasmid-harboring isolates for aminoglycoside susceptibility and inferred AMEs.
Main Results:
- 96% of isolates were multi-drug resistant, with high resistance rates to tobramycin (83.6%) and amikacin (55.1%).
- The most common AME identified was N-acetyltransferases (AAC), specifically AAC(6 ext{ extprime})-I (42.8%), followed by AAC(3)-II (20.4%).
- Plasmid-harboring isolates exhibited the AAC(6 ext{ extprime}) phenotype, with the enzyme inferred to be AAC(6 ext{ extprime})-I.
Conclusions:
- High levels of resistance to tobramycin and amikacin are prevalent in Pseudomonas aeruginosa from Indian burn patients.
- AAC(6 ext{ extprime})-I is the predominant aminoglycoside modifying enzyme (AME) and appears to be plasmid-encoded in resistant isolates.
- This study highlights the need for broader surveillance of AME-mediated aminoglycoside resistance in Pseudomonas aeruginosa across India.
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