Pneumococcal resistance in the UK

The first case reports of infection with penicillin-resistant pneumococci (PRP, MIC > 0.1 mg/L) and multidrug-resistant pneumococci were made in Australia in 1967 and South Africa in 1977, respectively. Since this time these organisms have spread to become a worldwide problem. In Europe PRP prevalence rates of up to 40% have been reported from Spain and 58% from Hungary, although there has been considerable national, regional and local variation in these figures. Until recently the UK was considered to have low prevalence of PRP. As recently as 1990, 100% of 7255 strains of pneumococci from 61 centres across the UK were found to be penicillin sensitive. However, there have now been several reports of significant and rising levels of resistance nationwide. Erythromycin resistance has also risen from 2.8% to 8.6% between 1990 and 1995 in England and Wales. At the Northern Ireland Public Health Laboratory (NIPHL) 3171 strains of pneumococci were examined using the oxacillin screening test between 1988 and 1995, during which time the annual rate of penicillin resistance was found to increase from <1% to 10.6%. The proportion of PRP with high-level resistance (MIC > 1 mg/L) increased from 0% to 36% and levels of PRP cross-resistance to cephalosporins and ciprofloxacin were 89% and 78%, respectively, which are amongst the highest in the UK. Similar rates of penicillin resistance have now been reported from several geographically disparate regions in the UK including Liverpool, Manchester and London. The number of laboratories in England and Wales reporting the isolation of PRPs to the Central Public Health Laboratory increased from 23 (3%) in 1987 to 72 (21%) in 1991 and a recent study from this reference laboratory showed that the prevalence of pneumococcal resistance to penicillin had increased 2.5-fold between 1990 and 1995. Clearly both PRP and multidrug-resistant pneumococci are increasing in prevalence in the UK, and this increase is likely to continue. A recent model of the evolution of national PRP prevalence rates describes a slow emergence phase, followed by an exponential growth phase of around 10 years reaching a stationary phase when the proportion of PRP reaches 50%. It is possible that the UK is currently at the beginning of the exponential growth phase of PRP. This has implications for the future treatment of pneumococcal infections in this country and emphasizes the need for new anti-pneumococcal agents. The new quinolone grepafloxacin, which has an MIC90 of 0.25 mg/L for pneumococci, may represent a future alternative oral treatment for multidrug-resistant strains. The activity of this antibiotic against 70 PRPs is compared with that of two other quinolones and macrolides.