Epidemiological study of variations in beta-lactam antibiotic susceptibility of Pseudomonas aeruginosa in two intensive care units.
A six-month prospective study was carried out in the medical and surgical intensive care units (ICUs) at Besançon University Hospital to assess the frequency and risk factors for beta-lactam-resistant isolates of Pseudomonas aeruginosa. Clinical samples were screened for P. aeruginosa, and four antibiograms were distinguished using imipenem and ceftazidime, namely: fully susceptible (SS), imipenem-resistant (RS), ceftazidime-resistant (SR), and resistant to both (RR). DraI restriction fragment length polymorphism of isolates from different patients or with different resistance patterns but the same serotype was assessed by pulsed-field gel electrophoresis. One hundred and twenty-one isolates were obtained from 50 of 281 patients, 60.3% were fully susceptible. 19.8% imipenem-resistant, 13.2% ceftazidime-resistant, and 6.6% resistant to both. Antibiotic-resistance was independent of serotype. Twenty-two of 32 imipenem-resistant isolates from six patients were of the same DNA type, and six other isolates from four patients were of a second DNA type. On only one occasion did a clonally defined strain develop imipenem resistance. By contrast ceftazidime-resistant strains had differing DNA types, but had been originally ceftazidime-susceptible in seven of 12 patients. Reversion of imipenem resistant strains to susceptibility occurred in one patient, and of ceftazidime-resistant strains in five patients. Case-control studies identified prior antibiotic therapy as a risk factor in colonization with resistant strains. Resistance to imipenem followed imipenem therapy, and resistance to ceftazidime followed use of weakly anti-pseudomonal beta-lactam antibiotics. The major route of spread of imipenem-resistant strains was cross-colonization. Thus, assuming appropriate isolation, a carbapenem should be preferred to an extended-spectrum cephalosporin to treat pseudomonas infections in ICU patients.
Cailleaux
V
V
Laboratoire de Bactériologie-Hygiène, Hôpital Jean Minjoz, Besançon, France.
Mulin
B
B
Capellier
G
G
Julliot
M C
MC
Thouverez
M
M
Talon
D
D
D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D016022:Case-Control Studies; D004352:Drug Resistance, Microbial; D004812:Epidemiologic Methods; D005260:Female; D005838:Genotype; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D012150:Polymorphism, Restriction Fragment Length; D011446:Prospective Studies; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D012703:Serotyping; D047090:beta-Lactams
D000900:Anti-Bacterial Agents; D047090:beta-Lactams