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Letter
Staphylococcus aureus
Bacteremia, Europe
Edine W. Tiemersma,*
Dominique L. Monnet,† Nienke Bruinsma,* Robert Skov,† Jos C.M. Monen,*
Hajo Grundmann,* and European Antimicrobial Resistance Surveillance System
participants
*National Institute for Public Health and the Environment, Bilthoven,
the Netherlands; and †Statens Serum Institut, Copenhagen, Denmark
Suggested
citation for this article
To the Editor: In their article, Collignon et al. (1)
present a table comparing absolute numbers and incidence rates of Staphylococcus
aureus bacteremia (SAB) in Australia to those of 5 other countries,
and state that "some data are available from other countries for
comparison" and "only 2 countries, Denmark and England, appeared
to have comprehensive collection systems."
We would like to add data from the European Antimicrobial Resistance
Surveillance System (EARSS) to their table. EARSS is a multinational surveillance
system that links national networks by collecting comparable and validated
data on the prevalence of antimicrobial resistance of 5 microorganisms,
including S. aureus (2). A total of 30 countries
participate in EARSS. To ensure representativeness of the data it publishes,
EARSS has set criteria, which can be found elsewhere (3).
In 2003, through a questionnaire, we collected background information
on all hospitals served by laboratories participating in EARSS, including
the estimated hospitals' catchment populations. Proportion of the country
population covered by EARSS was then calculated by dividing the sum of
catchment populations by the total population of the country (4).
Catchment populations of hospitals providing single specialty or supra-regional
type of care were not counted to avoid overlap with other hospitals within
the same country. Only the countries that provided denominator data for
at least 60% of the isolates were included to ensure that the sample of
hospitals was still representative of the country as a whole.
The number of SAB and the incidence of SAB per 100,000 inhabitants in
2003 were calculated from EARSS data, adjusted for population coverage,
and are presented in the Table. These are crude estimates
of the true number of SAB and should, thus, be interpreted with caution.
For example, we assumed that the isolates for which hospital background
information was not available did not differ from isolates for which we
had this information, and that hospitals that participated in EARSS in
2003 were a representative sample of the countries' hospitals. Additionally,
the incidence of SAB was positively correlated with the blood culturing
rate (Spearman r = 0.74, p = 0.002), which means that the incidence
of SAB is likely to have been underestimated in countries that reported
few blood cultures. Although some countries did not report their blood
culturing rate, the incidences of SAB in these countries were among the
highest and are unlikely to be underestimated. For example, the EARSS
data for Denmark and Ireland nicely fitted those presented in Table 4
of the article by Collignon et al. (1). Finally, reporting
to the EARSS system greatly improved over the years, which is why this
study was performed on the last available year, 2003. Nevertheless, one
cannot exclude underreporting of SAB by EARSS participating hospitals
since EARSS is a voluntary reporting system. For example, England reported
18,403 SAB cases or an incidence of 37 SAB per 100,000 inhabitants from
April 2002 to March 2003 through its mandatory surveillance scheme (5),
whereas an estimate for the United Kingdom from the EARSS database would
only give 7,800 SAB cases for 2003. However, it is impossible to determine
whether this discrepancy was due to poor voluntary reporting of SAB cases,
a lower blood culturing rate in EARSS participating hospitals, or a poorly
representative sample of the country's hospitals. Data from the United
Kingdom were excluded from the present study on the basis of the latter
possibility; denominator information for <60% of the isolates was available.
In conclusion, EARSS is the first comprehensive surveillance system on
antimicrobial resistance in Europe. Within certain limitations, EARSS
can also provide valuable information on blood-culturing practices and
the incidence of SAB in Europe. The system is continuously being improved,
and additional information on the representativeness of EARSS data is
being collected. This will allow us to improve the quality and accuracy
of the reported incidence rates. In the future, the system should allow
reporting of similar data for an even larger number of European countries
and for additional microorganisms, such as Escherichia coli.
References
- Collignon P, Nimmo GR, Gottlieb T, Gosbell IB, Australian
Group on Antimicrobial Resistance. Staphylococcus
aureus bacteremia, Australia. Emerg Infect Dis. 2005;11:554–61.
- Tiemersma EW, Bronzwaer SL, Lyytikäinen O, Degener JE, Schrijnemakers
P, Bruinsma N, et al. Methicillin-resistant
Staphylococcus aureus in Europe, 1999–2002. Emerg Infect
Dis. 2004;10:1627–34.
- European Antimicrobial Resistance Surveillance System. EARSS manual
2004 [cited 2005 July 25]. Available from http://www.earss.rivm.nl
- Central Intelligence Agency. The world fact book 2003 [cited 2005
July 26]. Available from http://www.cia.gov/cia/download2003.htm
- Health Protection Agency. The second year of the Department of Health's
mandatory MRSA bacteraemia surveillance scheme in acute trusts in England:
April 2002–March 2003. CDR Weekly. 2003;13:1–9. [cited 2005 July 26].
Available from http://www.hpa.org.uk/cdr/archives/2003/cdr2503.pdf
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Table. Absolute numbers,
rates of Staphylococcus aureus bacteremia (SAB), and percentage
of methicillin-resistant Staphylococcus aureus (MRSA), European
Antimicrobial Resistance Surveillance System (EARSS), 2003*
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Country
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Population† (4)
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% population covered by EARSS‡
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Blood culture sets/1,000 inhabitants
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No. SAB reported to EARSS
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No. SAB for country§
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SAB/100,000 inhabitants§
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% MRSA
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Austria
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8,188,207
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42.7
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NA
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871
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2,038
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25
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15
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Bulgaria
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7,537,929
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100
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2
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157
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149
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2¶
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31
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Croatia
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4,422,248
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81.3
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7
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360
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443
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10
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37
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Czech Republic
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10,249,216
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92.3
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11
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1,387
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1,503
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15
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7
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Denmark
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5,384,384
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46.2
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NA
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671
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1,451
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27
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<1
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Estonia
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1,408,556
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100
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<1
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98
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98
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7¶
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5
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Finland
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5,190,785
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94.3
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27
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727
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771
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15
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1
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Hungary
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10,045,407
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100
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1
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859
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859
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9¶
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14
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Iceland
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280,798
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100
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28
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64
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64
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23
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0
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Ireland
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3,924,140
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89.2
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NA
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1,108
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1,243
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32
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42
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Israel
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6,116,533
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39.7
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42
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368
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926
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15
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43
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Malta
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400,420
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100
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4
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122
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122
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31
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43
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Poland
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38,622,660
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24.3
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3
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166
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684
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2¶
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19
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Romania
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22,271,839
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59
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<1
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85
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144
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<1¶
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46
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Slovenia
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1,935,677
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100
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17
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299
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296
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15
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13
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Spain
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40,217,413
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24.3
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21
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1,391
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5,731
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14
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25
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Sweden
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8,878,085
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100
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28
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1,855
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1,760
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20
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<1
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*Only countries that provided hospital background
information for at least 60% of the isolates were included; NA,
not available.
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†Source: (4).
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‡Population coverage rate as calculated from EARSS
hospitals that provided background information was adjusted for
nonresponding hospitals as follows: population coverage as calculated
divided by proportion of isolates with hospital background information.
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§The total number of SAB per country was calculated
as follows: number of S. aureus isolates in EARSS divided
by adjusted proportion of population covered.
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¶These rates are grossly underestimated because
of the very low blood culturing rate.
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Suggested citation
for this article:
Tiemersma EW, Monnet
DL, Bruinsma N, Skov R, Monen JCM, Grundmann H, et al. Staphylococcus
aureus bacteremia, Europe [letter]. Emerg Infect Dis [serial on the
Internet]. 2005 Nov [date cited]. Available from http://www.cdc.gov/ncidod/EID/vol11no11/05-0524.htm
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