| We also examined the likelihood of a
resistance in the four age groups as indicated above given an
invasive strain of S. pneumoniae was cultured. We used
logistic regression to control for the impact of country, and took
the age group of the elderly as the reference. As the figure shows,
young children are the age group with the highest risk for
resistance (odds ratio 1.5; 95% confidence interval 1.2 to 1.9)
followed by elderly people (reference group). Teenagers (0.6; 0.4 to
1,0) and adults (0.6; 0.5 to 0.7) have the lowest risk.
The proportion of PNSP is in general higher in southern Europe
compared with northern European countries. We calculated a half
yearly overall proportion of resistance weighted by the size of the
population of each country, starting in 1999. The overall proportion
of PNSP in Europe remained fairly stable (January to June 1999: 10%,
July to December 1999: 10%, January to June 2000: 12%).
Methicillin resistant S. aureus
Since 1998, a total of 18 countries have reported blood isolates
of S. aureus to EARSS. Similar to S. pneumoniae, the
number of reporting laboratories in various countries varies greatly
among countries due to differences in the size of population, the
healthcare organisation, and the coverage of the surveillance
system. Since most laboratories are associated with only one
hospital, the number of hospitals also varies widely between
countries. S. aureus is largely a problem associated with
hospital stay, and it is therefore particularly important to include
in each country a representative sample of hospitals from different
sizes and functions, covering all geographical areas. Some countries
are continuing in their efforts to improve the representativeness of
the laboratories and hospitals participating.
In almost every country exactly 60% of the isolates are from male
patients. Male sex is, however, no risk factor for MRSA. We divided
the departments of the patients’ stay into two groups: adult or
paediatric intensive care unit (ICU) versus other wards, such as the
internal medical or obstetric and gynaecologic department. Compared
with patients in the second group, patients from an ICU were 2.3
times more likely to have a S. aureus strain that was
resistant to methicillin.
In a multivariate model we included the variables age (for four
groups: 0-4, 5-14, 15-64, >64 years of age) and hospital
department, controlling for country. Both age and hospital
department remained significant predictors. In contrast to S.
pneumoniae, the risk of identifying an MRSA strain given S.
aureus was cultured from blood, rises with increasing age.
Children aged 0-4 years and children aged 5-14 years are only 0.1
times, whereas are adults 0.6 times as likely as elderly people
(reference) to be infected with MRSA.
Finally, we examined the proportion of hospitals reporting MRSA
to EARSS over time. The proportion of hospitals reporting at least
one MRSA rose from 40% in January to June 1999 to 49% in July to
December 1999, to stabilise with 47% during January to June 2000. It
is too early to comment on a possible trend, because the observed
period of time is still relatively short and there are still new
countries joining EARSS.
A comparison of proportions of MRSA among different European
countries (table) suggests that the proportion is higher in southern
Europe. For both PNSP and MRSA, however, these differences may in
part be due to different testing behaviours or attitudes among
physicians.
Annex. Participating countries and
national representatives in EARSS |