1 Laboratório Especial de Microbiologia Clínica, Disciplina de Doenças Infecciosas e Parasitárias, Universidade Federal de São Paulo, Rua Leandro Dupret, 188, São Paulo, SP-04025.010, Brazil; 2 The Jones Group/JMI Laboratories, North Liberty, IA, USA
Keywords: Pseudomonas aeruginosa, carbapenem resistance, Latin America, SENTRY Antimicrobial Surveillance Program
Sir,
Recent studies have focused on the decreased susceptibility of Pseudomonas aeruginosa to currently used anti-pseudomonal agents, including ß-lactams, aminoglycosides and fluoroquinolones.1,2 The carbapenems imipenem and meropenem are usually active against multidrug-resistant isolates of P. aeruginosa; however, resistance to these compounds has also become a growing therapeutic problem.2 The SENTRY Antimicrobial Surveillance Program is a global resistance monitoring system designed to assess antimicrobial resistance trends worldwide. The present study was conducted to determine the variation in susceptibility rates of P. aeruginosa in participant Latin American medical centres to selected antimicrobial agents for a consecutive 5 year period (19972001).
A total of 1894 P. aeruginosa isolates were consecutively collected from clinical specimens during the period of January 1997 to December 2001. Ten Latin American laboratories participated in the study in each year. They were located throughout six countries: Argentina, Brazil, Chile, Colombia, Mexico and Uruguay. Three medical centres were replaced during the study period. In 1998, a Venezuelan centre replaced the Uruguayan centre, and in 1999 a centre in Porto Alegre replaced the Brazilian centre in Rio de Janeiro, which is also located in the southern region of that country. Finally, in 2001, the Colombian medical centre was replaced by a hospital in Brasilia, Brazil. Most of the centres were tertiary-care hospitals.
Monitored events included bloodstream infections, pneumonia, skin and soft tissue infections and urinary tract infections. P. aeruginosa isolates were collected only from patients with clinically significant disease, based on local selection criteria. Duplicate isolates from the same patient were excluded from the study. The isolates were identified by the participating institutions using the routine methodology at each laboratory. Protocols for species identification upon receipt at the coordinator centre have been described previously.3
Antimicrobial susceptibility testing was carried out according to the reference broth microdilution method recommended by the National Committee for Clinical Laboratory Standards.4 Annual antimicrobial resistance trends were determined by 2 test; P values < 0.05 were considered to be statistically significant. Statistical analysis was carried out with the Epi-Info version 6.04b software package (Centers for Disease Control and Prevention, Atlanta, GA, USA).
Participant centres in Brazil and Argentina contributed the majority of isolates (48.3% and 24.8%, respectively). P. aeruginosa was more frequently recovered from the respiratory tract (43.3%), followed by the bloodstream (31.7%), skin and soft tissue (11.7%) and the urinary tract, which accounted for only 8.6% of all isolates.
Longitudinal susceptibility profiles listed by the year of isolation are shown in Table 1. Overall decreases in susceptibility rates for all 12 cited agents were recorded, reaching the lowest levels in 2000 for aztreonam and amikacin, or 2001 for all other agents. Comparative evaluation of annual rates revealed decreases in susceptibility to all listed antimicrobial agents (P < 0.001). The estimated OR and respective CI 95% for each antimicrobial clearly indicates increasing levels of resistance among isolates of P. aeruginosa recovered in Latin America during this 5 year period. The most important decline in susceptibility rate was noted for the carbapenems meropenem (from 83.0% in 1997 to 64.4% in 2001, P <0.001, OR = 2.70; 95% CI 1.883.89) and imipenem (from 77.1% to 62.2%, P < 0.001, OR = 2.07; 95% CI 1.472.90).
|
The SENTRY Program findings in the Latin American region were in agreement with previous local studies, demonstrating that increasing resistance to commonly used anti-pseudomonal agents is a major therapeutic issue.5,6 Furthermore, this report clearly indicates that antimicrobial resistance among P. aeruginosa isolates in Latin American countries has increased significantly over a relatively short time period. This upward trend may reflect differences in antimicrobial prescription practices and/or a more frequent dissemination of MDR clones in those countries participating in the SENTRY Program. Further epidemiological studies should be carried out in these institutions to evaluate the reasons for this rapid and continuous increase in resistance rates. The clustering of MDR P. aeruginosa isolates in Brazilian hospitals along with the increasing prevalence of this pathogen overall raise concerns regarding the effective antimicrobial therapy for infections caused by P. aeruginosa, since limited options are available for clinical use. Moreover, changes in local prescription policies may have produced unpredictable shifts in the susceptibility profiles.
Acknowledgements
We express our gratitude to the Latin America SENTRY investigators. The SENTRY Antimicrobial Surveillance Program was funded by an educational/research grant from Bristol-Myers Squibb.
Footnotes
* Corresponding author. Tel/Fax: +55-11-5081-2819/5081-2965/5571-5180; E-mail: lemcdipa{at}terra.com.br
References
1 . Jones, R. N., Kirby, J. T., Beach, M. L. et al. (2002). Geographic variations in activity of broad-spectrum-lactams against Pseudomonas aeruginosa: summary of the worldwide SENTRY Antimicrobial Surveillance Program (19972000). Diagnostic Microbiology and Infectious Disease 43, 23943.[CrossRef][ISI][Medline]
2
.
Livermore, D. M. (2001). Of Pseudomonas, porins, pumps and carbapenems. Journal of Antimicrobial Chemotherapy 47, 24750.
3 . Gales, A. C., Jones, R. N., Turnidge, J. et al. (2001). Characterization of Pseudomonas aeruginosa isolates: occurrence rates, antimicrobial susceptibility patterns, and molecular typing in the global SENTRY Antimicrobial Surveillance Program, 19971999. Clinical Infectious Diseases 32, Suppl. 2, 14655.[CrossRef]
4 . National Committee for Clinical Laboratory Standards. (2000). Methods for Dilution Antimicrobial Tests for Bacteria that Grow Aerobically: Approved Standard M7-A5. NCCLS, Wayne, PA, USA.
5 . Bantar, C., Famiglietti, A. & Goldberg, M. (2000). Three-year surveillance study of nosocomial bacterial resistance in Argentina. The Antimicrobial Committee and the National Surveillance Program (SIR) Participants Group. International Journal of Infectious Disease 4, 8590.[Medline]
6 . Sader, H. S. (2000). Antimicrobial resistance in Brazil: comparison of results from two multicenter studies. Brazilian Journal of Infectious Disease 4, 919.[Medline]