Protocol for the Scottish
Mandatory Surveillance
Programme for
Staphylococcus aureus
bacteraemia
5th Edition December 2012
Table of Contents
1 Introduction
3
2 Case Definition
3
3 Management of surveillance data 4
4 Surveillance Reports
5
5 Conclusion
5
Reference5
Appendix I: Data Flow for Staphylococcus aureus bacteraemia reports identified
through routine laboratory reporting
6
Appendix II: Data Flow for Staphylococcus aureus bacteraemia reports identified through
submission of isolates to SMRSARL as part of the European Centres for Disease Control
(ECDC) antimicrobial resistance surveillance system (EARS-Net)
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General Enquiries and Contact Details:
If you have any comments or queries relating to this protocol, please contact the team on 0141 300 1922 or
at sshaipdata@hps.scot.nhs.uk
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1Introduction
1.1All NHS diagnostic microbiology laboratories in Scotland must report every episode of Staphylococcus
aureus bacteraemia to Health Protection Scotland (HPS). This is a mandatory requirement of Health
Department letter HDL(2006)381.
1.2Laboratories within the private sector are not obliged to report episodes of Staphylococcus aureus
bacteraemia, but they may choose to participate in this national surveillance.
1.3This document describes the Staphylococcus aureus bacteraemia surveillance programme for Scotland,
including case definitions and reporting arrangements.
1.4 HPS has published quarterly reports on the numbers of meticillin resistant Staphylococcus aureus (MRSA)
bacteraemias in Scotland since April 2002. The programme was extended to include reporting of meticillin
sensitive Staphylococcus aureus (MSSA) bacteraemias from July 2006.
1.5 This programme has been approved by the National Healthcare Associated Infection Steering Group and
Programme Board. HPS has continued to develop this programme under the auspices of this group.
1.6 It is now mandatory for NHS diagnostic laboratories to send every blood isolate of Staphylococcus aureus
(including both MRSA and MSSA) to the Scottish MRSA Reference Laboratory (SMRSARL) for further
characterisation. These isolates are accompanied by clinical data on each case. This SMRSARL testing
also contributes to the European Centres for Disease Control (ECDC) antibiotic resistance surveillance
system (EARS-Net).
2
Case Definition
2.1The surveillance system seeks to enumerate episodes of healthcare associated blood infections with
Staphylococcus aureus.
2.2 The program has established case definitions and procedures to ensure consistency both between different
healthcare locations and across periods of time. Describing a system of Clostridium difficile surveillance,
Riley observed that: “Definitions are for the purposes of surveillance and not designed to identify every
infection. It is better to be approximately right most of the time rather than completely right occasionally”
(http://www.aica.org.au/docs/about/downloads/definition3.pdf)
2.3 The surveillance programme therefore requires that every case where Staphylococcus aureus is isolated
from a blood culture is reported, regardless of whether this is believed to be clinically significant or
not. Using this definition may lead to some false positive cases (for example where a blood sample was
contaminated by skin commensals or where the bacteraemia was transient and probably not a true
septicaemic episode). The consistent use of a surveillance case definition obviates the need for potentially
subjective assessment of individual cases.
2.4The surveillance case definition also includes all Staphylococcus aureus bacteraemias, so as to avoid the
need for potentially subjective assessment of whether an individual case’s bacteraemia was associated
with healthcare interventions.
2.5The programme identifies and excludes instances when multiple Staphylococcus aureus isolates have
been obtained from blood samples during the course of managing a single episode of infection. This
includes instances where positive isolates have been reported from the same patient by different Scottish
laboratories. Therefore, positive isolates from a single patient submitted within two weeks of each
other are defined as a single episode. Isolates submitted more than two weeks apart are counted as
separate episodes (provided that there have been no other positive samples during the elapsed fortnight).
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This definition avoids the need for potentially subjective assessment of whether multiple samples truly
represent separate episodes of infection.
2.6 The surveillance programme therefore defines a case of Staphylococcus aureus bacteraemia as: “A person
from whose blood Staphylococcus aureus has been isolated and reported by a diagnostic microbiology
laboratory in Scotland in the absence of a positive blood culture with the same organism in the previous
two weeks”.
2.7The above definition requires that the dates of isolates are clearly defined. Because of variations in the
availability and quality of these data, the programme uses this hierarchy to assign the date on which a
sample was taken:
••Date specimen collected
••Date sample received in laboratory
••Date report received by HPS
This date is then used to identify the starting date of an episode so that the definition in 2.6 may be applied.
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Management of surveillance data
3.1 All Scottish NHS microbiology laboratories submit reports on Staphylococcus aureus bacteraemias through
the HPS Electronic Communication of Surveillance in Scotland (ECOSS).
3.2 Extracts of these reports are transferred to a database for further analyses and reporting. The data fields
extracted are:
••Laboratory name
••Date collected
••Date received in laboratory
••Laboratory number
••Patient ID
••CHI number
••Forename
••Surname
••Date of birth
••Pathogen
3.3 On receipt of information on individual isolates of Staphylococcus aureus bacteraemia, HPS undertakes a
process of de-duplication of these reports, thereby identifying individual surveillance episodes.
3.4 Episode reports are then reviewed by each reporting laboratory to allow them to identify any discrepancies
between locally held data and the data held by HPS. If a response is not received from the reporting
laboratory then the episodes are published as is. The report contains the caveat “data are subject to
revision as updated data becomes available”.
3.5Separately, the Information and Statistics Division (ISD) of National Services Scotland (NSS) provides
data on every NHS board’s acute occupied bed days (AOBDs). An AOBD is defined as an acute hospital
bed occupied for one night. An acute hospital bed is any bed other than a psychiatric bed or a care of
the elderly long stay bed. These data are derived from Scottish hospitals’ counts of their occupied beds
at midnight. The database at ISD is frequently updated, therefore a review of the bed day data used in
previous two years quarterly reports is done every quarter.
3.6 The episode data are aggregated to produce the numbers of episodes for individual NHS boards. The NHS
boards’ episode totals are divided by the board’s acute occupied bed days data to produce Staphylococcus
aureus bacteraemia incidences, expressed as rates per 100 000 acute occupied bed days.
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Surveillance Reports
4.1The analyses of these rates are compiled into a quarterly report which is published in the HPS Weekly
Report. The results of additional analyses at the level of individual NHS boards are reported as Appendices
which are published on the HPS website.
4.2Microbiologists and other named individuals within each NHS board are sent a copy of the quarterly
report 5 working days before publication of the report.
4.3 A summary of the data for all NHS boards is forwarded to the Scottish Government for their use in the
HEAT performance management system.
5Conclusion
5.1 The surveillance programme does not (and cannot) provide an absolutely accurate picture of Staphylococcus
aureus bacteraemia in Scotland, for several reasons.
••no surveillance programme can have complete sensitivity (the ability to identify all true cases) or specificity
(the ability to ensure all cases identified are true).
••the need for consistency in a surveillance programme requires that some accuracy is sacrificed for the
sake of consistency.
••the flexibility of a case definition which would be appropriate for use in clinical management is not
appropriate for the consistency necessary for surveillance.
••the resources required for an absolutely accurate system may not be justifiable in practice.
5.2This protocol for the Scottish Staphylococcus aureus bacteraemia surveillance programme supports a
consistent system for surveillance enabling comparisons between NHS boards and over periods of time.
Reference
1.
Health Department Letter (2006) 38 A revised framework for national surveillance of healthcare associated infection in Scotland 57 Edinburgh: SEHD.
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Result entered on laboratory information system
Data transferred via ECCOSS
Standard data set from all bacteraemias
extracted for Staphylococcus aureus reporting
Duplicates identified deleted
Extract sent to each
Laboratory for confirmation
Staphylococcus aureus bacteraemia
report produced
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HEALTH PROTECTION SCOTLAND
Blood sample taken
LABORATORY WARD
Appendix I: Data Flow for Staphylococcus aureus bacteraemia reports
identified through routine laboratory reporting.
Blood sample taken
Diagnostic laboratory
S.aureus identified & antibiogram determined by laboratory staff
Standard EARS-Net form completed & sent with isolate to SMRSARL
LABORATORY WARD
Appendix II: Data Flow for Staphylococcus aureus bacteraemia reports
identified through submission of isolates to SMRSARL as part of the
European Centres for Disease Control (ECDC) antimicrobial resistance
surveillance system (EARS-Net).
Patient data entered into SMRSARL computer
Isolate confirmed as S. aureus
Characterisation performed & antibiogram determined
Results entered onto laboratory information system
SMRSARL
SMRSARL
Data transferred via ECCOSS
HPS S.aureus
bacteraemia reporting
system
Duplicates identified & removed
Non S.aureus isolates
identified & removed
Standard data set
extracted for reporting
to microbiologists
HPS
Data arrives at HPS
EARS.Net report produced
HPA
(England, Wales
& Northern Ireland data)
HPA
Northern Ireland data
Combined UK data sent to ECDC
ECDC
Country 2
Country 3
Public
WHO
ESCMID
EUCAST
ESAC
ECDC
Country 1
ECDC, European Centres for Disease Control; SMRSARL, Scottish MRSA Reference Laboratory; HPS, Health Protection Scotland; HPA, Health Protection
Agency; WHO, World Health Organisation; ESCMID, European Society for Clinical Microbiology & Infectious Diseases; EUCAST, European Committee on
Antimicrobial Susceptibility Testing; ESAC, European Surveillance of Antimicrobial Consumption.
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