Comparison of antimicrobial cycling and mixing strategies in two medical intensive care units.
OBJECTIVE
To compare a mixing vs. a cycling strategy of use of anti-Pseudomonas antibiotics on the acquisition of resistant Gram-negative bacilli in the critical care setting.


METHODS
Prospective, open, comparative study of two strategies of antibiotic use.


METHODS
Two medical intensive care units of a university hospital.


METHODS
A total of 346 patients admitted for >or=48 hrs to two separate medical intensive care units during an 8-month period.


METHODS
Patients, who according to the attending physician's judgment required an anti-Pseudomonas regimen, were assigned to receive cefepime/ceftazidime, ciprofloxacin, a carbapemen, or piperacillin-tazobactam in this order. "Cycling" was accomplished by prescribing one of these antibiotics during 1 month each. "Mixing" was accomplished by using the same order of antibiotic administration on consecutive patients. Interventions were carried out during two successive 4-month periods, starting with mixing in one unit and cycling in the other.


RESULTS
Swabbing of nares, pharynx, and rectum and culture of respiratory secretions were obtained thrice weekly. The main outcome variable was the proportion of patients acquiring enteric or nonfermentative Gram-negative bacilli resistant to the antibiotics under intervention. The scheduled cycling of antibiotics was only partially successful. Although the expected antibiotic was the most prevalent anti-Pseudomonas agent used within the corresponding period, it never accounted for >45% of all anti-Pseudomonas antimicrobials administered. During mixing, a significantly higher proportion of patients acquired a strain of Pseudomonas aeruginosa resistant to cefepime (9% vs. 3%, p = .01), and there was a trend toward a more frequent acquisition of resistance to ceftazidime (p = .06), imipenem (p = .06), and meropenem (p = .07). No differences in the rate of acquisition of potentially resistant Gram-negative bacilli or incidence of intensive care unit-acquired infections and infections due to particular organisms were observed.


CONCLUSIONS
In critically ill medical patients, a strategy of monthly rotation of anti-Pseudomonas beta-lactams and ciprofloxacin may perform better than a strategy of mixing in the acquisition of P. aeruginosa resistant to selected beta-lactams.
Martínez
José-Antonio
JA
Department of Infectious Diseases, Hospital Clínic, IDIBAPS -University of Barcelona, Spain. jamarti@clinic.ub.es
Nicolás
Josep-María
JM
Marco
Francesc
F
Horcajada
Juan-Pablo
JP
Garcia-Segarra
Gloria
G
Trilla
Antoni
A
Codina
Carles
C
Torres
Antoni
A
Mensa
Josep
J
D018806:APACHE; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D001424:Bacterial Infections / Q000145:classification / Q000188:drug therapy*; D003428:Cross Infection / Q000188:drug therapy*; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D007902:Length of Stay; D008297:Male; D008875:Middle Aged; D011552:Pseudomonas Infections / Q000145:classification / Q000188:drug therapy*
D000900:Anti-Bacterial Agents