Trends in antimicrobial susceptibility of Gram-negative isolates from a paediatric intensive care unit in Warsaw: results from the MYSTIC programme (1997–2007)

Objectives The Meropenem Yearly Susceptibility Test Information Collection (MYSTIC) programme is a longitudinal global surveillance study to monitor in vitro data on microbial susceptibility in centres that prescribe meropenem. This overview provides data on the susceptibility of Gram-negative bacteria (n = 1300) isolated from clinical specimens of children hospitalized in a paediatric intensive care unit (ICU) during 1997–2007. Methods MICs of meropenem and eight other antibiotics were determined using the CLSI agar dilution method. Results Meropenem, imipenem and ciprofloxacin were most active (>90% susceptibility) against the tested isolates. A greater proportion of Pseudomonas aeruginosa isolates was susceptible to meropenem compared with imipenem. Antibiotic susceptibility of Enterobacteriaceae and Acinetobacter baumannii showed an increase in 2007. Only susceptibility of P. aeruginosa to ceftazidime and cefepime increased. The incidence of extended-spectrum β-lactamase (ESBL) producers among Enterobacteriaceae isolates decreased from 37% in 1997 to 21.8% in 2007, and AmpC β-lactamase producers decreased from 24.6% to 5.7%. Consumption of cephalosporins remained the same and piperacillin/tazobactam increased 3-fold. During 11 years, despite an increase in carbapenem consumption, meropenem and imipenem have retained excellent activity against the majority of isolates studied. Conclusions The comparison of antibiotic susceptibility of Gram-negative isolates in 1997 and 2007 showed a trend of increase, and the number of β-lactamase-producing isolates among Enterobacteriaceae showed a trend of decrease possibly related to changes in antibiotic policy.