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Infections due to gentamicin-resistant Staphylococcus aureus strain in a nursery for neonatal infants
Abstract:
An apparently homogeneous strain of Staphylococcus aureus resistant to gentamicin (Gmr), kanamycin, tobramycin, and sisomicin, but susceptible to amikacin and netilmicin, caused multiple infections in neonatal infants in a special care nursery. Nasal cultures revealed a high rate of carriage of the Gmr staphylococcus in infants without clinical infection. Segregating patients according to a modified cohort system and use of careful aseptic techniques led to apparent elimination of the Gmr strain. The resistance to aminoglycosides in this strain was mediated by an aminoglycoside 6'-N-acetyltransferase and a gentamicin phosphotransferase. Genetic determinants for these enzymes were borne on a circular covalently closed plasmid of approximately 11 megadaltons. These resistance determinants closely resemble those found in isolates of S. aureus that have caused nosocomial infections in patients in Europe.
Insights
A novel Staphylococcus aureus strain resistant to multiple aminoglycosides caused neonatal infections. Strict infection control measures successfully eliminated the strain, highlighting effective strategies against antibiotic-resistant bacteria.
Area of Science:
- Microbiology
- Infectious Diseases
- Genetics
Background:
- A nosocomial outbreak involving a gentamicin-resistant (Gmr) Staphylococcus aureus strain occurred in a neonatal special care nursery.
- This strain exhibited resistance to gentamicin, kanamycin, tobramycin, and sisomicin, but remained susceptible to amikacin and netilmicin.
Purpose of the Study:
- To investigate the characteristics and control of a gentamicin-resistant Staphylococcus aureus strain causing neonatal infections.
- To identify the genetic mechanisms conferring aminoglycoside resistance in the S. aureus strain.
Main Methods:
- Epidemiological investigation including patient segregation and enhanced aseptic techniques.
- Microbiological culturing and antibiotic susceptibility testing.
- Plasmid analysis and characterization of aminoglycoside resistance genes.
Main Results:
- The Gmr S. aureus strain was identified as the causative agent of multiple neonatal infections.
- Nasal cultures indicated a high carriage rate of the Gmr strain in asymptomatic infants.
- Implementation of modified cohorting and aseptic techniques led to the successful elimination of the Gmr strain.
- Aminoglycoside resistance was mediated by aminoglycoside 6'-N-acetyltransferase and gentamicin phosphotransferase enzymes.
- The genetic determinants for resistance were located on an 11-megadalton plasmid, similar to European isolates.
Conclusions:
- Modified cohorting and aseptic techniques are effective in controlling the spread of antibiotic-resistant S. aureus in neonatal units.
- The identified plasmid-borne resistance genes are a significant factor in the emergence of multidrug-resistant S. aureus.
- Understanding the genetic basis of resistance is crucial for developing targeted interventions against nosocomial infections.