PTU - Polskie Towarzystwo Urologiczne
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CODE: 5 - An in vitro susceptibility of nosocomial Gram-negative uropathogens to antibacterial agents
Article published in Urologia Polska 2006/59/Suplement 1.


Katarzyna Kot, Alicja Rokosz, Iwona Serafin, Anna Sawicka-Grzelak, Mirosław Łuczak
Katedra i Zakład Mikrobiologii Lekarskiej AM w Warszawie


Introduction. Urinary tract infections (UTI) are one of the most frequent infectious diseases recognized in hospitalized patients (40-50% of all infections) and in ambulatory patients (10-20% of all infections). Infection of a urine bladder is the predominant type of UTI. Gram-negative rods belonging to the intestinal bacterial microflora, especially Escherichia coli (90% of infections) are the most commonly isolated in cases of urinary tract infections in outpatients. These infections are generally caused by the ,,wild" strains, which are highly susceptible to antimicrobials. The predominating etiological agents of hospital UTI are E. coli strains (50% of infections), and next rods of other genera of enteric rods, non-fermenting rods, enterococci, staphylococci and streptococci. The empiric therapy of ambulatory patients is generally successful, because of high susceptibility of strains causing UTI in outpatients to antibiotics/chemotherapeutics. The broad-spectrum antimicrobials are usually used in therapy of nosocomial UTI and this is the basic cause of selection of highly resistant strains. So, in cases of UTI in hospitalized patients guided therapy should be quickly applied, which is preceded by the isolation, correct identification, antimicrobial susceptibility testing and detection of mechanisms of resistance of cultured uropathogens to antimicrobial agents used in urologic practice.
Objectives. The analysis of occurrence and susceptibility to antimicrobials of Gram-negative bacteria causing urinary tract infections in hospitalized patients.
Materials and methods. Urine samples obtained by the ,,middle stream" method from patients of the Infant Jesus Hospital - Centre for Trauma Treatment in Warsaw were analysed during twelve months. Uropathogenic bacteria were identified and their susceptibility to antimicrobials was determined in the automatic ATB Expression system (bioMerieux, sa). Gram-negative rods producing extended-spectrum beta-lactamases (ESBL) were detected by the double disc synergy test (DDST) or the diagnostic disc method (DD).
Results. Among 6131 analyzed urine specimens, 1660 samples were positive in culture. The majority of uropathogenic strains were isolated from patients of the transplantology wards. Rods of the family Enterobacteriaceae (1149 strains; 85.9%) predominated among isolated uropathogens, especially E. coli (660 strains). Among non-fermenting rods (188 strains) the majority of strains belonged to the species Pseudomonas aeruginosa (108; 57.4%) and Acinetobacter baumannii (45; 24%). Eighty three strains of ESBL-positive Gram-negative rods were detected (6.2%). Enteric rods were susceptible first of all to imipenem (98% of a total number of strains) and fosfomycin (90%), and next to aminoglycosides and third generation cephalosporins. Imipenem and fosfomycin were the most active substances against uropathogenic strains of non-fermentative rods. Strains isolated from patients of the transplantology departments were more resistant to antimicrobials.
Conclusions. Enteric rods, especially E. coli, predominated among Gram-negative bacteria isolated from urine samples. In the group of non-fermenting rods, P. aeruginosa and A. baumannii were most frequently isolated. ESBL - positive uropathogens were detected. The most active in vitro antimicrobial agents against isolated Gram-negative bacteria were imipenem and fosfomycin.