Systematic Surveillance Detects Multiple Silent Introductions and Household Transmission of Methicillin-Resistant Staphylococcus aureus USA300 in the East of England.
BACKGROUND
The spread of USA300 methicillin-resistant Staphylococcus aureus (MRSA) across the United States resulted in an epidemic of infections. In Europe, only sporadic cases or small clusters of USA300 infections are described, and its prevalence in England is unknown. We conducted prospective surveillance for USA300 in the east of England.


METHODS
We undertook a 12-month prospective observational cohort study of all individuals with MRSA isolated from community and hospital samples submitted to a microbiology laboratory. At least 1 MRSA isolate from each individual underwent whole-genome sequencing. USA300 was identified on the basis of sequence analysis, and phylogenetic comparisons were made between these and USA300 genomes from the United States.


RESULTS
Between April 2012 and April 2013, we sequenced 2283 MRSA isolates (detected during carriage screening and in clinical samples) from 1465 individuals. USA300 was isolated from 24 cases (1.6%). Ten cases (42%) had skin and soft tissue infection, and 2 cases had invasive disease. Phylogenetic analyses identified multiple introductions and household transmission of USA300.


CONCLUSIONS
Use of a diagnostic laboratory as a sentinel for surveillance has identified repeated introductions of USA300 in eastern England in 2012-2013, with evidence for limited transmission. Our results show how systematic surveillance could provide an early warning of strain emergence and dissemination.
University of Cambridge Wellcome Trust Sanger Institute Cambridge University Hospitals NHS Foundation Trust.
Michelle S
MS
Toleman
University of Cambridge.
Sandra
S
Reuter
University of Cambridge.
Francesc
F
Coll
University of Cambridge.
Ewan M
EM
Harrison
University of Cambridge.
Beth
B
Blane
Cambridge University Hospitals NHS Foundation Trust Clinical Microbiology and Public Health Laboratory, Public Health England, Cambridge.
Nicholas M
NM
Brown
University of Cambridge Cambridge University Hospitals NHS Foundation Trust Clinical Microbiology and Public Health Laboratory, Public Health England, Cambridge.
M Estée
ME
Török
Wellcome Trust Sanger Institute.
Julian
J
Parkhill
University of Cambridge Wellcome Trust Sanger Institute Cambridge University Hospitals NHS Foundation Trust London School of Hygiene and Tropical Medicine, United Kingdom.
Sharon J
SJ
Peacock
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D018562:Disease Transmission, Infectious; D004739:England / Q000453:epidemiology; D062665:Epidemiological Monitoring; D005191:Family Characteristics; D005192:Family Health; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D008875:Middle Aged; D017720:Molecular Epidemiology; D011446:Prospective Studies; D017422:Sequence Analysis, DNA; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000382:microbiology* / Q000635:transmission; D055815:Young Adult
MRSA; Staphylococcus aureus; USA300; molecular epidemiology; whole-genome sequencing