Of 229 laboratories identified in England and Wales in the directory,14
208 (91%) reported blood isolates to the surveillance centre in 1998. Reports increased from31
763in 1990 to 51
232 in 1998(P<0.05) (fig ). E coli
, Staph aureus
, coagulase negative staphylococci, Strep pneumoniae
, and either Enterococcus
species (including E faecium
, E faecalis
, and group D streptococci)or Klebsiella
species (fig ) accounted for 60% of all reports each year. A further 20% comprised either Klebsiella
species or Enterococcus
species, α and non-haemolytic streptococci (other than pneumococci), and Proteus
species, and Pseudomonas aeruginosa
Incidence of commonly reported causes of bacteraemia in England and Wales, 1990 to 1998
Poisson regression showed a year on year proportional increase for seven categories (table ) that was also present within each age group. Haemophilus influenzae declinedsteeply from 1992. Most reports were from adults but the reporting rate was high in infants: 1149 reports for infants aged 0-28 days and 1169 for infants aged 29 to 365 days in 1998 (table ).
Causative organisms of bacteraemia, showing year on year proportional increasing trend by Poisson regression analysis, 1990-8
Table 2 Numbers of reports of bacteraemia and report rate per 100000 by age group in England and Wales, 1998. Denominators for rates were mid-year population estimates for England and Wales (Office for National Statistics, London)
Staph aureus was among the top five causes of bacteraemia in every age group,whereas E coli, coagulase negative staphylococci, Strep pneumoniae, and Enterococcus species ranked lower at certain ages (fig ). α and non-haemolytic streptococci (excluding pneumococci) accounted for 5-7% of bacteraemiasin children of all ages and for 2-4% aged over 14 years. Group B streptococci comprised 22% of reports in infants aged 0 to 28 days, 5% in infants aged 29 days to 1 year, were rare in children aged between 1and14 years (three reports in 1998), but contributed 1-2% in the adult age groups. Neisseria meningitidis accounted for 11-17%of reports in age groups from birth to 14 years,2% from 15 to 44 years, and less than 1% in older age groups. The proportion of reports contributed by each age group to each category of bacteraemia was similar in every year.
Figure 2 Common causes of bacteraemia by age group as proportion of total reports for England and Wales, 1998 (age group <1 month equals 28 days; 1-11 months equals 29-365 days)
The subset of reports with completion of the antibiotic susceptibility field generally declined in 1996 and 1997 and recovered in 1998 (fig ). Methicillin resistance in Staph aureus increased from 1.7% to 3.8% from 1990 to 1993, rose steeply to 32% in 1997 and to 34% in 1998 (fig ). Gentamicin resistance in E coli increased from 1.7% in 1990 to 3% in 1997 declining to 2.2% in 1998. Vancomycin resistance in Ent faecium reached 6.3% in 1993, 20% in 1995, and 24% in 1998. Vancomycin resistance in Ent faecalis was under 3% from 1990 to 1996, increasing to 5% in 1998. Ampicillin resistance, however, was recorded in 15% of Ent faecalis and ampicillin sensitivity in 17% of Ent faecium reports in 1998, suggesting frequent mis-speciation. Penicillin resistance in Strep pneumoniae was under 1% in 1990 and 1991, increasing to 3.7% in 1996, to 7.4% in 1997, and 3.6% in 1998. Erythromycin resistance in Strep pneumoniae increased from 5% in 1990 to stabilise at about 11% from 1994 onwards.
Figure 3 Antibiotic resistance ((number resistant + number intermediate)/(number resistant + number intermediate + number sensitive) x 100) in bacteraemia isolates (lines) and numbers of reports with antibiotic susceptibility data (bars) (more ...)