R factors in gentamicin-resistant organisms causing hospital infection

Area of Science:

• Medical Microbiology
• Infectious Diseases
• Hospital Epidemiology

Background:

• An increase in gentamicin-resistant bacterial isolates was observed at the Manhattan Veterans Administration Hospital during 1973 and 1974.
• This rise in resistance coincided with a significant number of bacteraemic infections.

Purpose of the Study:

• To investigate the emergence and characteristics of gentamicin resistance in hospital-acquired infections.
• To identify the mechanisms and transmission patterns of gentamicin resistance.

Main Methods:

• Bacterial isolates from patients were collected and tested for gentamicin resistance.
• Resistance factors (R factors) mediating gentamicin resistance were identified.
• Interbacterial spread of resistance was assessed by analyzing resistance patterns within individual patients.

Main Results:

• An abrupt increase in gentamicin-resistant isolates was documented.
• Bacteraemic infections occurred in 17 patients, resulting in 9 deaths.
• R factors conferring gentamicin resistance were found in 34 out of 36 resistant strains.
• In 9 of 11 patients, isolates shared a common resistance pattern, indicating in-vivo spread.

Conclusions:

• The study highlights a concerning rise in gentamicin resistance.
• R factor-mediated resistance appears to be a significant factor in this outbreak.
• Evidence suggests in-vivo interbacterial spread of R factors contributes to the dissemination of gentamicin resistance within patients.