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Investigation of nosocomial prosthetic valve endocarditis due to antibiotic-resistant Staphylococcus epidermidis
R Menzies1, D MacCulloch, B Cornere
1Microbiology Department, Green Lane Hospital, Auckland, New Zealand.
Abstract:
A reservoir of antibiotic-resistant Staphylococcus epidermidis strains in our cardiac surgery unit appeared to be the source of organisms responsible for three cases of early prosthetic valve endocarditis. Staphylococcus epidermidis isolates recovered from the skin of 13 patients before and after surgery were compared. All were typed by plasmid profile, antimicrobial susceptibility and slime production. The three strains from early prosthetic valve endocarditis resembled the antibiotic-resistant nosocomial strains recovered from the skin of eight patients following surgery and the environment of the operating theatres. These strains expressed resistance to oxacillin, gentamicin, kanamycin and tobramycin and most produced slime, whereas those isolated from the skin of patients at the time of admission were predominantly susceptible to antibiotics and few produced slime.
Insights
Antibiotic-resistant Staphylococcus epidermidis strains in cardiac surgery units can cause prosthetic valve endocarditis. Post-operative patient skin and operating room environments harbored these resistant strains, unlike pre-operative samples.
Area of Science:
- Microbiology
- Infectious Diseases
- Clinical Medicine
Background:
- Prosthetic valve endocarditis (PVE) is a serious complication following cardiac surgery.
- Staphylococcus epidermidis is a common cause of healthcare-associated infections, including PVE.
- Antibiotic resistance in S. epidermidis poses a significant challenge in clinical settings.
Purpose of the Study:
- To investigate the source of Staphylococcus epidermidis strains causing early prosthetic valve endocarditis.
- To compare the characteristics of S. epidermidis isolates from PVE cases, patient skin, and the operating environment.
- To identify potential reservoirs for nosocomial S. epidermidis infections in cardiac surgery units.
Main Methods:
- Plasmid profiling of S. epidermidis isolates.
- Antimicrobial susceptibility testing.
- Slime production assays.
- Comparison of isolates from PVE patients, pre- and post-operative patient skin, and operating theatre environments.
Main Results:
- Three cases of early PVE were linked to antibiotic-resistant S. epidermidis strains.
- Nosocomial S. epidermidis strains from post-operative skin and operating theatres matched PVE isolates.
- These resistant strains exhibited resistance to oxacillin, gentamicin, kanamycin, and tobramycin, and frequently produced slime.
- Pre-operative isolates were mostly susceptible to antibiotics and produced little slime.
Conclusions:
- A reservoir of antibiotic-resistant S. epidermidis exists within the cardiac surgery unit.
- The operating theatre environment and post-operative patient skin can harbor strains responsible for PVE.
- Effective infection control measures are crucial to prevent PVE caused by nosocomial S. epidermidis.