Abstract
Background:This study sought to understand the epidemio-ecological dynamics of MRSA isolates associated with a South African hospital over a period spanning year 2007-8 (a previous study reported in 2009) and year 2010-11 (this study).Methods:One hundred and ninety three isolates were characterised by molecular fingerprinting methods including pulsed field gel electrophoresis (PFGE), spa typing, agr-typing, SCCmec-typing, and multilocus sequence typing (MLST). The Vitek-2 automated antibiogram of representative isolates was also performed.Results:Our data shows that the distribution of MRSA strains among the different clinical conditions was rarely dependent on the genetic backbone or genotype. Compared to the previous survey in 2009, CA-MRSA isolates increased by 31% while HA-MRSA isolates decreased by 17%. An increase in genetic diversity was also revealed including the detection of three pandemic clonal complexes (spa type t012-ST36/CC30, spa type t037-ST239/CC8, spa type t891-ST22/CC22 and spa type t1257-ST612/CC8). Majority of the genotypes were classified as Spa Cluster B-SCCmec I-agr I 19.2%; (37/193) Spa Cluster A-SCCmercury-agr I 14.5%; (28/193)Conclusion:This study reveals that increased diversity in MRSA genetic background was associated with resistance to frontline antibiotics. Also, an increase was recorded in the CA-MRSA/HA-MRSA ratio within a 5-year period despite the continuous dominance of the HA-MRSA genotype.
Highlights
Staphylococcus aureus is accountable for a high proportion of cases of severe infection in hospital and outpatient units [1]
Over a period of 5 years in the investigated clinical setting, Community- associated MRSA (CA-MRSA) isolates increased by 31% while healthcare-associated MRSA (HA-MRSA) isolates decreased by 17%
In conclusion, this study reveals an increase in the CA-MRSA/HA-MRSA ratio despite the continuous dominance of the HA-MRSA genotype
Summary
Staphylococcus aureus is accountable for a high proportion of cases of severe infection in hospital and outpatient units [1]. The epidemiology of MRSA after its discovery has evolved from the initial healthcare-associated MRSA (HA-MRSA) genotypes which were mostly. Cases of HA-MRSA replacement by CA-MRSA in hospital infection have been reported [3], an evolutionary model has suggested that high heterogeneity of MRSA in human populations may drive the eventual co-existence of CA-MRSA and HA-MRSA genotypes [4]. There have been reports of increased diversity of MRSA genetic background [5, 6] which may have contributed to the blurring of the distinction between CA-MRSA and HA-MRSA [2]. This study sought to understand the epidemio-ecological dynamics of MRSA isolates associated with a South African hospital over a period spanning year 2007-8 (a previous study reported in 2009) and year 2010-11 (this study)
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