Increasing prevalence of multidrug-resistant Streptococcus pneumoniae in the United States over a 10-year period: Alexander Project

Abstract

The Alexander Project is a global surveillance study conducted from 1992 to 2001. Minimum inhibitory concentrations and percent resistance to a panel of antimicrobial agents were determined according to National Committee for Clinical Laboratory Standards methodology. Resistance to penicillin (PEN-R) and erythromycin (ERY-R) have increased in the period 1992–2001 by 3.9 and 4.5 times to 20.7% and 27.9%, respectively. Joint PEN–ERY-R has increased 4.9 times, up to 15.3%. In 1992, 57.1% of all PEN-R isolates were also ERY-R, whereas in 2001, 75.8% were ERY-R. Resistance to only 1 antibiotic increased slightly, from 8% in 1992 to 12% in 2001, whereas resistance to more than 1 antibiotic increased 4.3 times, from 6.4% in 1992 to 27.8% of all strains in 2001. Multidrug-resistant pneumococci are an increasingly common finding in the United States. Three of four PEN-R isolates are also multiresistant. The rate of growth of multidrug resistance is higher than that of single antibiotic resistance.

Introduction

Streptococcus pneumoniae continues to be a major cause of morbidity and mortality worldwide (Baquero, 1995, Smith and Coast, 2002). The organism remains the leading bacterial cause of community-acquired pneumonia, otitis media, and sinusitis (McDougal et al, 1992). Because identity and antimicrobial susceptibility results are rarely available to the clinician in an outpatient setting at the time the patient is seen, antibiotic therapy is often empiric. Strains that have a high level of resistance to penicillin (PEN-R) and other antimicrobial agents appeared in the United States at a low prevalence in the early 1990s (Breiman et al, 1994), having been first reported by researchers in Boston in 1965, and subsequently in Australia in 1967 and South Africa in 1977 (Appelbaum, 1992). Within the past few years, increasing numbers of resistant and multiple resistant (Appelbaum, 1992) isolates of S. pneumoniae have become a worldwide problem (Felmingham, 1999). The emergence of double and triple antimicrobial resistance is a matter of major concern (Smith and Coast, 2002). Treatment failures due to drug resistance have been reported with meningitis (Sloas et al., 1992, Catalan et al., 1994), otitis media (Jacobs, 1996), and community acquired pneumonia (Garau, 2001). Multiresistance and the potential spread of these organisms have crucial implications for the treatment and clinical outcome of patients.

Established in 1992, the Alexander Project is an international surveillance study examining the antimicrobial susceptibility of the major upper and lower respiratory tract bacterial pathogens and identifying trends in the development of resistance over time. Antimicrobial susceptibility is established to a range of compounds, with testing undertaken in 3 central laboratories using standardized procedures (Felmingham et al, 1996). The current analysis comprises US antimicrobial susceptibility data for 1992–2001 for S. pneumoniae and describes the emergence of penicillin, macrolide, and multidrug resistance among pneumococcal strains isolated from patients with community-acquired respiratory tract infections in several regions of the United States. This data collection provides a unique source to analyze trends in resistance over a 10-year period.