Objectives:

The Uro-Quick, an automatic instrument widely used for the screening of bacteriuria, was previously employed to detect antibiotic resistance in well-characterised bacterial strains (J Chemother16, 2004 in press) and in uropathogens. In this study pathogens isolated in ICU of a great Italian hospital during the period September–November 2003 were examined employing the Kirby–Bauer technique for antibiotic susceptibility tests and this usual system was compared with the new rapid Uro-Quick method.

Methods:

Antibiotic (in appropriate concentration) was introduced in a vial containing 2 mL of Mueller–Hinton (MH) broth, then 0.5 ml of broth containing 5 × 10⁵–10⁶ cells/mL of the strain to test were added in each vial containing the antimicrobial molecules and even in a drug-free vial as control. After 3 and 5 h of incubation (Gram-negative or Gram-positive strains, respectively) the instrument printed the results: no growth and a growth curve like the control is representative of a susceptible and resistant strain respectively. Gram negative strains were tested against ciprofloxacin (CIP), ampicillin (AM), aztreonam (ATM), co-clavulanate (AMC), piperacillin/tazobactam (TZP), ceftazidime (CAZ), cefotaxime (CTX), cefuroxim (CXM), ceftriaxone (CRO), imipenem (IPM), amikacin (AN), gentamycin (GM) and trimethoprim–sulphamethoxazole (SXT), while Gram-positive bacteria against CIP, clindamycin (CM), erythromycin (E), IPM, linezolid (LZD), AM or penicillin (P), rifampicine (RA) GM, streptomycin (S), tetracycline (TE), vancomycin (VA), oxacillin (OXA) and SXT.

Results:

The Gram-negative strains tested were 121 and the Gram-positive 144, agreement between the two methods was 93% against Gram-negative (SXT and CTX 98.3%, CIP 97.5%, GM 96.7%, CRO 96%, AN and CAZ 95%, IPM 94%, AM 92%, CXM and AMC 90%, TZP 88%, ATM 84%) and 95% against Gram-positive (AM 100%, LZD 99%, CM, IPM, VA and S 97%, CIP, RA, TE and SXT 95%, E 92%, OXA and P 94%, GM 88.4%) pathogens.

Conclusion:

Against major pathogens (staphylococci, enterococci and Enterobacteriaceae) agreement between the Uro-Quick system and the Kirby–Bauer method was always more than 90%. On the basis of the present findings the rapid method appears useful in severe nosocomial infections because the rapid detection (in 3 or 5 h) of antibiotic susceptibility allows a more direct treatment, reduce the empiric therapy and the diffusion of resistant pathogens.