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Nontypeable bacteriophage patterns of methicillin-resistant Staphylococcus aureus involved in a hospital outbreak
K I Khalifa1, A A Heiba, G Hancock
1Microbiology Department, Faculty of Medicine, Suez Canal University, Ismailia, Egypt.
Abstract:
Of 93 strains of Staphylococcus aureus isolated from inpatient wards of Ismailia General Hospital, 48 (51%) were proven to be methicillin resistant (MR). Of these MR S. aureus strains, 44 were isolated from patients and 4 were isolated from healthy carriers, who were newly arrived interns working in the same wards. Bacteriophage patterns of MR S. aureus were identified by using routine test dilution (RTD) and 100-fold dilutions (100 RTD) of phages. Of these 48 strains, 37 (75%) (33 from patients and 4 from interns) were nontypeable when using RTD and 100 RTD of phages. Of the other 11 strains, 8 were nontypeable by RTD of phages, but 5 of them had the phage pattern D11/1136 when tested by 100 RTD. Three strains had the phage pattern 3A/3C/55/71, and three strains had different phage patterns, 29/81, 96, and 95/D11. The finding of colonization with virulent MR S. aureus strains in interns working on the wards in which these patients were located suggested that new strategies for control of MR S. aureus nosocomial infections must be considered and evaluated.
Insights
Methicillin-resistant Staphylococcus aureus (MRSA) was found in 51% of strains from hospital patients and interns. Colonization in interns suggests new control strategies are needed for MRSA nosocomial infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Hospital Epidemiology
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) is a significant cause of nosocomial infections.
- Understanding the epidemiology and transmission patterns of MRSA is crucial for effective control.
Purpose of the Study:
- To determine the prevalence of MRSA among inpatient wards.
- To characterize the phage patterns of isolated MRSA strains.
- To investigate potential reservoirs of MRSA within hospital staff.
Main Methods:
- Isolation and identification of Staphylococcus aureus strains from inpatient wards.
- Antimicrobial susceptibility testing to identify methicillin resistance.
- Bacteriophage typing using routine test dilution (RTD) and 100-fold dilutions (100 RTD).
Main Results:
- Out of 93 Staphylococcus aureus strains, 48 (51%) were identified as MRSA.
- MRSA strains were isolated from 44 patients and 4 newly arrived interns.
- A significant proportion (75%) of MRSA strains were nontypeable by standard phage typing methods.
Conclusions:
- The presence of MRSA in both patients and asymptomatic interns highlights a potential transmission route.
- The high rate of nontypeable strains complicates epidemiological tracing.
- New strategies for controlling MRSA nosocomial infections, including staff screening, should be considered.