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Healthcare Associated Infections
Methicillin-sensitive Staphylococcus Aureus (MSSA) Bacteraemias
For more information about this CEC program, click here

Why is this important?

Healthcare associated infections (HAI) are a leading cause of preventable illness and death [1-5]. Staphylococcus aureus (S. aureus) bacteraemia (SAB) is a serious cause of morbidity and mortality worldwide. SAB is the most common cause of healthcare associated bacteraemias, with over half of all SAB episodes in Australia being attributed as a HAI [6]. Typically, SABs that are able to be treated with common antibiotics, and demonstrate no resistance to the antibiotic, are referred to as being caused by methicillin-sensitive S. aureus (MSSA). National reporting of all healthcare-acquired SABs, including those caused by MSSA bacteraemias, was introduced in Australia in 2008. MSSA bacteraemia incidences and rates also are a key performance indicator for jurisdictions under the National Healthcare Agreement [7]. This section will present MSSA SAB data for NSW, including both 'inpatient' and 'non-inpatient' HAI.

The HAI Program addresses the Australian Commission on Safety and Quality in Health Care's National Safety and Quality Health Service (NSQHS) Standards [8]:

  1. 3.1 – 3.4 Clinical governance and quality improvement to prevent and control healthcare-associated infections, and support antimicrobial stewardship;
  2. 3.5 – 3.12 Infection prevention and control systems;
  3. 3.15 – 3.16 Antimicrobial stewardship;


[1] Klevens RM, Edwards JR, Richards CL, et al. Estimating health care-associated infections and deaths in U.S. hospitals, 2002. Public Health Rep. 2007; 122 (2):160-6.
[2] Jarvis WR, Jarvis AA, Chinn RY, et al. National prevalence of methicillin-resistant Staphylococcus aureus in inpatients at US health care facilities, 2010. Am J Infect Control. 2012; 40 (10):194-200.
[3] Sievert DM, Ricks P, Edwards JR, et al. Antimicrobial-resistant pathogens associated with healthcare-associated infections: summary of data reported to the National Healthcare Safety Network at the Centers for Disease Control and Prevention, 2009-2010. Infect Control Hosp Epidemiol. 2013; 34 (1):1-14.
[4] Huang SS, Septimus E, Kleinman K, et al. Targeted versus universal decolonization to prevent ICU infection. N Engl J Med. 2013; 368 (24):2255-65.
[5] Graves N, Weinhold D, Tong E, et al. Effect on healthcare-acquired infection on length of hospital stay and cost. Infect Control Hosp Epidemiol. 2007; 28(3): 280-292.
[6] Collignon P, Nimmo GR, Gottlieb T, et al. Staphylococcus aureus bacteremia, Australia. Emerg Infect Dis. 2005; 11(4):554-561.
[7] Standing Council on Federal Financial Relations. National Healthcare Agreement 2012. Accessed  November 2013 [Online]:
[8] Australian Commission on Safety and Quality in Health Care (2017). National Safety and Quality Health Service Standards, ACSQHC, Sydney.


The annual rate of MSSA in NSW hospitals decreased from 0.79 per 10,000 occupied bed days (OBDs) in 2011 to 0.54 in 2018 (Chart MS01). Despite fluctuating monthly infection rates, a steady declining trend in State’s annual rates was observed. The monthly variation in rates provides information to review and enhance infection Prevention and Control programs, an ongoing trend may reflect an actual increase in the overall rates.


Patients who develop bacteraemias, such as MSSA, are more likely to suffer complications that result in a longer hospital stay and an increased cost of hospitalisation. Serious infections may also result in death. The aim, therefore, is to minimise the total number of bacteraemias.

What we don't know

S. aureus is a normal human commensal that can also behave as a versatile and virulent pathogen [9]. Underlying patient factors are important in determining the likelihood of pathogen transmission and complicated bloodstream infection. Improved understanding of these patient factors requires additional data collection and analysis. The analysis of MSSA infection data by; its origin whether it is hospital- or community-acquired, hospital peer group classification, or a change in severity stages during hospital admission may shed some light on the MSSA transmission process.In addition, the trend analysis comparing rates for MRSA and MSSA bacteraemias may identify differences in the pattern of SAB infections over time.


[9] Lowy FD. Staphylococcus aureus infections. N EnglJ Med 1998; 339 (8):520-32.

Chart MS01 - Methicillin-sensitive Staphylococcus aureus (MSSA) Bacteraemias
Monthly MSSA bacteraemia rate per 10,000 occupied bed days (public hospitals), NSW, Jan 2012 - Dec 2018
Chart MS01 – Methicillin-sensitive Staphylococcus aureus (MSSA) bacteraemias
Source: NSW Ministry of Health, Health care Associated Infections data Collections.

End Matter

Drafted by: CEC eChartbook team and CEC Governance and Assurance Directorate
Data analysis by: CEC eChartbook team
Reviewed by: CEC Governance and Assurance Directorate
Edited by: CEC eChartbook team

Suggested citation
Clinical Excellence Commission (access year). eChartbook Portal: Safety and Quality of Healthcare in New South Wales. Sydney: Clinical Excellence Commission. Available at: Accessed (insert date of access).

© Clinical Excellence Commission 2019
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Evidence-base for this initiative

Reported elsewhere
Healthcare Associated Infection, NSW MOH -

Data Definitions

Chart: MS01

Admin Status: Current, Dec 2018

Indicator Name: Methicillin-sensitive S. aureus (MSSA) bacteraemias

Description: Methicillin-sensitive S. aureus (MSSA) bacteraemia rate per 10,000 occupied bed days (public hospitals only), NSW, Jan 2012 - Dec 2018

Dimension: Patient safety

Clinical Area: Initiatives in safety and quality health care

Data Inclusions: All methicillin-sensitive S. aureus (MSSA) bacteraemias (including inpatient & non-inpatient)

Data Exclusions: None

Numerator: Total number of methicillin-sensitive S. aureus (MSSA) bacteraemias (including inpatient & non-inpatient)

Denominator: Total number of bed days

Standardisation: None (crude bacteraemia rate per 10,000 occupied bed days calculated)

Data Source: NSW Health Healthcare Associated Infections Data Collection, Jan 2012 - Dec 2018, NSW Ministry of Health, Clinical Excellence Commission

Comments: MSSA comprises infections recorded in two clinical indicators (Clinical indicator 2.1 Healthcare associated (inpatient) MSSA BSIs per 10,000 occupied bed days and Clinical indicator 2.3 Healthcare associated (non-inpatient) MSSA BSIs per 10,000 occupied bed days).