Transatlantic Spread of the USA300 Clone of MRSA
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《新英格兰医药杂志》
To the Editor: The emergence of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) is of great concern.1,2 USA300, the predominant epidemic clone in numerous outbreaks in closed communities in the United States,2 is also increasingly seen in Europe.3 International travel and the increasing trend of training or working abroad among health care workers probably contribute to its global spread.
We describe the transfer of community-acquired MRSA from the United States to Europe and its successful eradication. A 41-year-old healthy Swiss physician performed a clinical fellowship in the United States from July 2001 to June 2003. Three months before his departure, nasal and pharyngeal swabs from the physician were negative in cultures obtained during the investigation of a case of MRSA infection.
At our institution, in Basel, Switzerland, there is routine screening of health care workers from countries with a high prevalence of MRSA. The nasal and pharyngeal swabs from the physician were found to be positive for MRSA after his return from the United States. The isolate was resistant only to beta-lactam agents and clarithromycin. Molecular typing by pulsed-field gel electrophoresis showed a banding pattern consistent with that of the USA300 strain (Figure 1). The genotype of the staphylococcal chromosomal cassette was determined to be SCCmec type IV, and the Panton–Valentine leukocidin genes (lukS-PV and lukF-PV) were detected, both by polymerase-chain-reaction analysis.
Figure 1. Pulsed-Field Gel Electrophoresis of Three Strains of Methicillin-Resistant Staphylococcus aureus.
Lane A shows the strain from the colonized physician. Lane B shows the USA300 strain and Lane C the reference strain, NCTC 8325, as a molecular-weight marker. Banding patterns were processed with GelCompar II software (Applied Maths).
After extended screening cultures (of axillary, inguinal, perirectal, and rectal swabs) were found to be negative, decolonization was performed for five days with 2 percent mupirocin nasal ointment, 2 percent chlorhexidine oropharyngeal rinses, and 4 percent chlorhexidine body scrub. The physician was furloughed from the care of patients until decolonization was completed. Cultures of the colonized sites were negative 2 days after decolonization and remained so for 3, 6, 12, and 18 months thereafter.
This example illustrates a plausible route of global transfer of community-acquired clones of MRSA. It is not clear whether the strain was acquired in a health care institution or in the community, but evidently it was acquired in the United States. Without screening and decolonization, there is the potential for spread into the hospital environment, with dangers of increased endemicity, morbidity, and even mortality.
Institutions with a low prevalence of MRSA should consider screening strategies for health care workers and patients who are native to high-prevalence countries or have recently traveled to such locales. The role of health care workers in the cause and transmission of community-acquired MRSA infection needs to be defined.
Andreas Tietz, M.D.
Reno Frei, M.D.
Andreas F. Widmer, M.D.
University Hospital Basel
CH-4031 Basel, Switzerland
atietz@uhbs.ch
References
Vandenesch F, Naimi T, Enright MC, et al. Community-acquired methicillin-resistant Staphylococcus aureus carrying Panton-Valentine leukocidin genes: worldwide emergence. Emerg Infect Dis 2003;9:978-984.
Chambers HF. Community-associated MRSA -- resistance and virulence converge. N Engl J Med 2005;352:1485-1487.
Wannet W, Heck M, Pluister G, et al. Panton-Valentine leukocidin positive MRSA in 2003: the Dutch situation. Euro Surveill 2004;9:28. (Also available at http://www.eurosurveillance.org/eq/2004/04-04/eq-04-2004.pdf.)
We describe the transfer of community-acquired MRSA from the United States to Europe and its successful eradication. A 41-year-old healthy Swiss physician performed a clinical fellowship in the United States from July 2001 to June 2003. Three months before his departure, nasal and pharyngeal swabs from the physician were negative in cultures obtained during the investigation of a case of MRSA infection.
At our institution, in Basel, Switzerland, there is routine screening of health care workers from countries with a high prevalence of MRSA. The nasal and pharyngeal swabs from the physician were found to be positive for MRSA after his return from the United States. The isolate was resistant only to beta-lactam agents and clarithromycin. Molecular typing by pulsed-field gel electrophoresis showed a banding pattern consistent with that of the USA300 strain (Figure 1). The genotype of the staphylococcal chromosomal cassette was determined to be SCCmec type IV, and the Panton–Valentine leukocidin genes (lukS-PV and lukF-PV) were detected, both by polymerase-chain-reaction analysis.
Figure 1. Pulsed-Field Gel Electrophoresis of Three Strains of Methicillin-Resistant Staphylococcus aureus.
Lane A shows the strain from the colonized physician. Lane B shows the USA300 strain and Lane C the reference strain, NCTC 8325, as a molecular-weight marker. Banding patterns were processed with GelCompar II software (Applied Maths).
After extended screening cultures (of axillary, inguinal, perirectal, and rectal swabs) were found to be negative, decolonization was performed for five days with 2 percent mupirocin nasal ointment, 2 percent chlorhexidine oropharyngeal rinses, and 4 percent chlorhexidine body scrub. The physician was furloughed from the care of patients until decolonization was completed. Cultures of the colonized sites were negative 2 days after decolonization and remained so for 3, 6, 12, and 18 months thereafter.
This example illustrates a plausible route of global transfer of community-acquired clones of MRSA. It is not clear whether the strain was acquired in a health care institution or in the community, but evidently it was acquired in the United States. Without screening and decolonization, there is the potential for spread into the hospital environment, with dangers of increased endemicity, morbidity, and even mortality.
Institutions with a low prevalence of MRSA should consider screening strategies for health care workers and patients who are native to high-prevalence countries or have recently traveled to such locales. The role of health care workers in the cause and transmission of community-acquired MRSA infection needs to be defined.
Andreas Tietz, M.D.
Reno Frei, M.D.
Andreas F. Widmer, M.D.
University Hospital Basel
CH-4031 Basel, Switzerland
atietz@uhbs.ch
References
Vandenesch F, Naimi T, Enright MC, et al. Community-acquired methicillin-resistant Staphylococcus aureus carrying Panton-Valentine leukocidin genes: worldwide emergence. Emerg Infect Dis 2003;9:978-984.
Chambers HF. Community-associated MRSA -- resistance and virulence converge. N Engl J Med 2005;352:1485-1487.
Wannet W, Heck M, Pluister G, et al. Panton-Valentine leukocidin positive MRSA in 2003: the Dutch situation. Euro Surveill 2004;9:28. (Also available at http://www.eurosurveillance.org/eq/2004/04-04/eq-04-2004.pdf.)