… and Northern IrelandBMJ 1996; 313 doi: https://doi.org/10.1136/bmj.313.7060.820a (Published 28 September 1996) Cite this as: BMJ 1996;313:820
- C E Goldsmith, Department of Health and Social Services research registrar in medical microbiology,
- J E Moore, Clinical scientist in medical microbiology,
- P G Murphy, Consultant medical microbiologist
- Molecular Epidemiology Research Unit, Northern Ireland Public Health Laboratory, Belfast City Hospital, Belfast BT9 7AD
EDITOR,—Alan P Johnson and colleagues state that while the prevalence of resistance to penicillin in pneumococci in England and Wales is increasing, resistance to cefotaxime is still rare.1 We report data from similar studies at the Northern Ireland Public Health Laboratory.
In a study of 488 consecutive routine clinical isolates of Streptococcus pneumoniae sent to this laboratory in 1988, only four (0.8%) were found to be resistant to penicillin (minimum inhibitory concentration >/=0.1 mg/l).2 Subsequently, in the late 1980s and early 1990s, sporadic isolates that were resistant to penicillin were detected—on average two a year (table 1). In 1994, however, the figures increased to 3.1% and in 1995 to 10.6%, representing a 12-fold increase in the rate of isolation since 1993. A third of the isolates that were investigated further (16/42) showed high level resistance to penicillin, which usually cannot be overcome by increased doses of the drug. Of further concern is that 93% of the isolates (39/42) showed resistance to cefotaxime and by inference all cephalosporins (minimum inhibitory concentration >/=0.5 mg/l). This contrasts with recently reported rates of cross resistance to cefotaxime in Britain of 69%.3 Most of these pneumococcal infections would respond to the high dose schedules of intravenous cefotaxime used in hospitals, though some authors recommend that up to 24 g/day may be necessary. The pneumococci might not, however, respond to the low dose regimens of oral cephalosporins used in the community. A few isolates showed high level resistance to cefotaxime, against which even high dose intravenous regimens may fail.
A large proportion (34/42 (81%)) of the penicillin resistant pneumococci that we investigated were of serotype 9V, compared with only 10% of all the pneumococci in our study in 1988 and 39% in Johnson and colleagues' study. This resistant serotype is prevalent in Spain, which is a common holiday destination for young families from Northern Ireland. A clonal outbreak may be occurring in Northern Ireland after importation of penicillin resistant pneumococci by tourists returning from Spain, as was reported from Iceland in 1988.4 Alternatively, the pneumococci may have spread from the rest of Britain, and unrelated isolates may simply be clustered in a small number of serotypes; this is not the case with pneumococci that are sensitive to penicillin. Molecular epidemiological studies are currently under way to confirm the existence of an outbreak.
In conclusion, we agree with Johnson and colleagues that continued surveillance of antimicrobial resistance in pneumococci and the distribution of serotypes is essential, and we recommend the adoption of recent American guidelines establishing nationwide mandatory reporting of penicillin resistant pneumococci.5
We acknowledge the help of the Antibiotic and Streptococcal Reference Units of the Central Public Health Laboratory, London.