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. 2022 Feb;41(2):209-218.
doi: 10.1007/s10096-021-04353-9. Epub 2021 Oct 23.

A tale of two STs: molecular and clinical epidemiology of MRSA t304 in Norway 2008-2016

Hege Enger  1 , Kjersti Wik Larssen  1 , Elise Størvold Damås  1 , Hege Vangstein Aamot  2 , Anita Blomfeldt  2 , Petter Elstrøm  3 , Christina Gabrielsen Ås  4   5
Affiliations

A tale of two STs: molecular and clinical epidemiology of MRSA t304 in Norway 2008-2016

Hege Enger et al. Eur J Clin Microbiol Infect Dis. 2022 Feb.

Abstract

The purpose of this study was to investigate the epidemiological, molecular, and clinical characteristics of MRSA t304/ST8 and t304/ST6 in Norway from 2008 to 2016. Clinical and epidemiological data were collected for each case included in the study. Strains were characterized by PCR, spa typing, antimicrobial susceptibility testing, and whole genome sequencing. The overall number of cases of MRSA t304 increased from 27 in 2008 to 203 in 2016. Most MRSA t304/ST8 cases were defined as HA-MRSA (89.9%) and diagnosed in persons with Norwegian background, many of them living in nursing homes (62.3%). The number of t304/ST8 cases declined throughout the study period and it has not been reported in Norway since 2014. The increasing MRSA t304/ST6 genotype has mainly been introduced to Norway by immigration from the Middle East, but also from other parts of the world. The t304/ST6 clone is mostly classified as CA-MRSA (75.1%), does not seem to cause serious infections, is not multi-resistant, and has not yet caused outbreaks in Norway. This study provides an example of two MRSA clones with the same spa type found in different epidemiological settings. This is very unusual, but still a reminder that spa typing in some cases may have insufficient discriminatory power for surveillance of MRSA. Our results highlight the importance of active surveillance and characterization of emerging MRSA clones with high potential for spread in the community, which may potentially cause outbreaks in healthcare facilities.

Keywords: Epidemiology; Genotyping; MRSA; Surveillance; t304/ST6; t304/ST8.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Temporal distribution of MRSA t304/ST8 (n = 75) and t304/ST6 (n = 400) cases (bars) and as a percentage of total MRSA cases in Norway (lines)
Fig. 2
Fig. 2
Age distribution of patients with MRSA t304/ST8 (n = 69) and t304/ST6 (n = 249)
Fig. 3
Fig. 3
Map displaying birth country for patients with MRSA t304/ST8 (blue) and t304/ST6 (green), with circles sized relative to the number of cases in each country
Fig. 4
Fig. 4
Epidemiological characteristics of MRSA t304 cases. Comparison of cases defined as community-associated or healthcare-associated for t304/ST8 and t304/ST6 cases
Fig. 5
Fig. 5
Phenotypic antimicrobial susceptibility of MRSA t304/ST8 and t304/ST6 strains
Fig. 6
Fig. 6
Pan-genome phylogeny of MRSA t304/ST8 and t304/ST6 with epidemiological data and birth country
See this image and copyright information in PMC

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