A comparison of trends in antibiotic resistance in Staphylococcus aureus and Streptococcus pneumoniae in the UK

Abstract number: 1134_04_112

Bishop L.A., Alhaddad N., Lamagni T.L., Johnson A.P.

Objectives:  

To compare the trends in methicillin resistance in S. aureus and reduced susceptibility to penicillin and erythromycin in S. pneumoniae in the UK between 1999 and 2004, using the UK EARSS (European Antimicrobial Resistance Surveillance System) dataset.

Methods:  

The UK has participated in EARSS since it began in 1999. Under the scheme, a network of sentinel laboratories across the country sends information on all S. aureus blood-stream infections and S. pneumoniae isolates from blood or cerebrospinal fluid to the Health Protection Agency Centre for Infections. Data collected include the age and sex of the patient, hospital department and antimicrobial susceptibilities of the isolate. Laboratories may also include clinical information.

Results:  

The percentage of S. aureus isolates reported as resistant to methicillin increased from 33.2% in 1999 to 44.9% in the first quarter of 2004, an average increase of 1.96% per annum (p = 0.047, 95% CI 0.05–3.88%). The UK has one of the highest proportions of methicillin resistant S. aureus (MRSA) in Europe, ranking among the top five countries participating in EARSS between 1999 and 2004. By contrast, the percentage of S. pneumoniae isolates reported as non-susceptible (either resistant or intermediate) to penicillin decreased from 7.1% in 1999 to 3.9% in the first quarter of 2004, a significant average annual decrease of 0.61% (p = 0.012, 95% CI -(1.00% to -0.22%). For each of the years 1999–2004, the UK percentage of penicillin non-susceptible S. pneumoniae (PNSP) was ranked in the lower half among countries participating in EARSS. There was no trend in the percentage of S. pneumoniae isolates reported as resistant to erythromycin (p = 0.53). In 1999, 14.8% of isolates were reported as resistant to erythromycin with little fluctuation in the following years (15.2% resistant in the first quarter of 2004).

Conclusion:  

In the UK very different trends have been seen in two important antibiotic-resistant pathogens, MRSA and PNSP, since 1999. While the percentage of S. aureus isolates resistant to methicillin has increased, the percentage of PNSP has decreased, with the proportion of erythromycin-resistant pneumococci remaining stable. These trends may be related to differential antibiotic prescribing between hospital and community environments. The differences between these contrasting trends merit further epidemiological investigation and analysis.