The association between pathogen factors and clinical outcomes in patients with Staphylococcus aureus bacteraemia in a tertiary hospital, Cape Town
Date
2019-11-29
Journal Title
Journal ISSN
Volume Title
Publisher
Elsevier on behalf of International Society for Infectious Diseases
Abstract
Background: Staphylococcus aureus is a serious pathogen, able to cause life-threatening infections such as
bacteraemia. The association between S. aureus microbial characteristics and clinical outcomes is under-
investigated in African settings. This study aimed to determine the molecular epidemiology and virulence
characteristics of S. aureus isolates from bacteraemic patients at Tygerberg Hospital, South Africa, and to
investigate the associations between pathogen characteristics and clinical outcomes.
Methods: This study included 199 S. aureus isolates collected from blood cultures between February 2015
and March 2017. Methicillin resistance was determined using disc diffusion and all resistant isolates were
further characterized by staphylococcal cassette chromosome mec (SCCmec) typing. Genotyping was done
using spa and agr typing, and agr functionality was assessed using the phenotypic d-haemolysin assay.
Logistic regression models were performed to describe the associations between strain characteristics and
the clinical outcomes methicillin resistance, in-hospital mortality, and length of stay (LOS).
Results: Of the 199 S. aureus isolates collected, 27% were MRSA, and the overall crude in-hospital mortality
rate was 29%. Seventy-three different spa types were identified, including seven new types. Agr I was the
most common type, in 99 (49.7%) isolates, followed by agr II, III, and IV in 57 (28.6%), 37 (18.6%), and six (3%)
isolates, respectively. Agr dysfunctionality was observed in 25 (13%) isolates, mostly belonging to
spa-clonal complex (CC) 012. Methicillin resistance was significantly associated with hospital-acquired
infection (odds ratio (OR) 4.77, 95% confidence interval (CI) 2.09–10.87). A significant increase in mortality
was observed with increasing age (OR 7.48, 95% CI 2.82–19.8) and having a hospital-acquired infection (OR
2.26, 95% CI 1.12–4.55). S. aureus strains with a functional agr system showed an association with longer
duration of stay (OR 1.66, 95% CI 0.93–2.99).
Conclusions: We report the lowest MRSA prevalence at Tygerberg Hospital for the past 10 years, and agr
dysfunctionality was shown to be driven by a certain genotype, spa-CC012. Despite the limited available
clinical data, the study provided insights into associations between S. aureus epidemiology and agr-related
virulence characteristics, and clinical outcomes.
Description
CITATION: Abdulgadera, S. M. 2020. The association between pathogen factors and clinical outcomes in patients with Staphylococcus aureus bacteraemia in a tertiary hospital, Cape Town. International Journal of Infectious Diseases, 91:111-118, doi:10.1016/j.ijid.2019.11.032.
The original publication is available at https://www.ijidonline.com
Publication of this article was funded by the Stellenbosch University Open Access Fund
The original publication is available at https://www.ijidonline.com
Publication of this article was funded by the Stellenbosch University Open Access Fund
Keywords
Staphylococcus aureus, Pathogenic bacteria, Bacteraemia, Genetic regulation, Molecular epidemiology
Citation
Abdulgadera, S. M. 2020. The association between pathogen factors and clinical outcomes in patients with Staphylococcus aureus bacteraemia in a tertiary hospital, Cape Town. International Journal of Infectious Diseases, 91:111-118, doi:10.1016/j.ijid.2019.11.032