Trends in the Antimicrobial Susceptibility of Bacterial Respiratory Tract Pathogens - Findings of the Alexander Project 1992-1996

Abstract

The Alexander Project is an ongoing, multicenter surveillance study of the antimicrobial susceptibility of community-acquired lower respiratory tract bacterial pathogens with testing undertaken in a central laboratory. During the period 1992-1995, isolates were collected from geographically separate centers in countries of the EU and various states in the USA. In 1996, the project was extended to centers in Mexico, Brazil, Saudi Arabia, South Africa, Hong Kong and other European countries not previously included. Within Europe, France and Spain are established as centers with a high prevalence of both penicillin-intermediate (MIC 0.12-1 mg/l) and resistant (MIC > 2 mg/l) strains of Streptococcus pneumoniae, with combined resistance rates in excess of 40% in Toulouse and Barcelona in 1996. Combined rates of intermediate and resistant strains in excess of 10% were found in 1996, the first year of sampling, in Belgium, Switzerland, the Slovak Republic and Hungary. Penicillin resistance has evolved in the USA during the period of study, with rates for combined pneumococcal isolates increasing from 5.6% in 1992 to 16.4% in 1996. Of the new, non-European centers joining the project in 1996, Mexico (intermediate 31.4%, resistant 15.7%) and, in particular, Hong Kong (intermediate 9.1%, resistant 50%) are centers with a high prevalence of penicillin resistance. Macrolide resistance has increased generally among pneumococcal isolates examined during the study period, both in penicillin-susceptible and resistant isolates, and was evident in 16.5% of the 2160 isolates collected during 1996. In four centers (London, UK; Genoa, Italy; Pokfulum, Hong Kong; Leuven, Belgium), macrolide resistance rates exceeded those of combined penicillin-intermediate and resistant strains; in 12/19 centers (63.2%) macrolide resistance was more prevalent than penicillin resistance. In 1996, macrolide resistance was found in excess of 10% of isolates in Poland, Hungary, London, UK, combined USA isolates, the Slovak Republic, Barcelona, Spain, Genoa, Italy, Mexico, Toulouse, France and Pokfulum, Hong Kong. β-lactamase production was the principal mechanism of resistance found among isolates of Haemophilus influenzae, with rates in 1996 of around 20% or more in France, Belgium and Spain, and in excess of 10% in the UK and the Czech Republic. In the same year in non-European centers, Mexico (25%), Saudi Arabia (27.9%), Hong Kong (37.1%) and the USA (30.4% of combined isolates) had a high prevalence of β-lactamase production. Isolates of β-lactamase-negative, ampicillin-resistant H. influenzae were generally very uncommon, with only Barcelona, Spain consistently associated with rates in excess of 1%. β-lactamase production in Moraxella catarrhalis was observed in over 90% of isolates tested in 1996.