However, conventional typing methods appear not to have appropriate discriminatory power to show whether an outbreak in a hospital resulted from multiple independent introductions of a predominant MRSA lineage from a wider population or from a single source. For MRSA outbreaks, conventional molecular typing methods such as pulsed-field gel electrophoresis (PFGE), spa typing or multiple locus variable number tandem repeat analysis (MLVA) have been widely used before the advent of the whole genome sequencing (WGS) era 5, 6, 7, 8, 9. To date, many different molecular typing methods for discriminating MRSA isolates have been developed. At the same time, methods should be simple, inexpensive, rapid, highly reproducible and results easily interpretable 4. Moreover, typing methods used for epidemiological investigations should also be able to discern between genetically very closely related isolates, thus improving the resolution to near forensic precision. In outbreak settings, a typing method should have a high discriminatory power allowing correct exclusion of epidemiologically unrelated isolates. The prevention of nosocomial MRSA infections, especially in intensive care units with seriously ill patients, primarily include improved hand hygiene practices, extensive cleaning and disinfection of the hospital environment, and screening for MRSA carriage followed by isolation of documented carriers.Īccurate typing methods are required for efficient infection control. Individuals, who acquire MRSA colonization during a hospital stay, also serve as reservoirs for further dissemination in the healthcare settings as well as in the community. MRSA colonization is a significant risk factor for later infection 1, 2, 3. MRSA is easily transmitted in the health care setting and represents an ubiquitous problem wherever studies have been carried out. Many human infections are caused by multi-drug resistant bacteria and methicillin-resistant Staphylococcus aureus (MRSA) is one of the most prevalent pathogens in hospitals worldwide.
This work describes the usefulness of complete genome sequencing of bacterial chromosomes and plasmids providing an unprecedented level of detail during outbreak investigations not being visible by using conventional typing methods. We observed up to 8 SNPs or up to 5 alleles of difference by wgMLST when the isolates were recovered from different body sites of the same patient or if direct transmission between patients was most likely. However, WGS revealed a heterogeneous population structure of USA300 circulating at the AZP. Whole-genome sequencing (WGS) showed that all isolates were members of genomic variants of the North American USA300 clone. spa typing, genome-wide single nucleotide polymorphism (SNP) analysis, ad hoc whole genome multilocus sequence typing (wgMLST), stable core genome MLST (cgMLST) and in silico PFGE were used to determine phylogenetic relatedness and to identify transmission. The outbreak involved 12 patients and 1 healthcare worker/nurse at the AZP. We performed whole genome sequencing with complete gap closure for chromosomes and plasmids on all isolates. We report the investigation of an outbreak situation of methicillin-resistant Staphylococcus aureus (MRSA) that occurred at the Academic Hospital Paramaribo (AZP) in the Republic of Suriname from April to May 2013.