Arch Hellen Med, 28(4), July-August 2011, 529-536
Asymptomatic bacteriuria of the elderly; antimicrobial resistance and the importance of integrons
V. Nastos, C. Kosmidis, M. Grammatikou, G. Petrikkos, G.L. Daikos
OBJECTIVE Asymptomatic bacteriuria (AB) is common in the elderly. The aims of this study were to determine the prevalence of AB in the elderly and to characterize the organisms.
METHOD Urinary cultures were performed on asymptomatic adults aged >60 years from October 2002 to July 2003. Urine specimens were collected from residents of nursing homes, community residents and hospitalized patients. When criteria for ΑΒ were met, the isolates were tested for susceptibility. Enterobacteriaceae were tested for extended-spectrum beta-lactamase (ESBL) and metallo-β-lactamase (MBL) production, and for the presence of integrons. Statistical analysis was carried out with statistical package for social sciences (SPSS) v 12.0 for Windows.
RESULTS Urine specimens were collected from 638 patients, with a mean age of 71.08±9.19 years, of whom 186 were nursing home and 323 community residents, and 129 were hospitalized in a department of internal medicine. The prevalence of AB was 13.6% for the community, 30.6% for nursing-home residents and 27.9% for hospitalized patients. The most common cause of AB was E. coli followed by enterococci, P. mirabilis and K. pneumoniae. ESBL production was detected in 21.1% of nursing-home Enterobacteriaceae were isolated from 25.8% of nosocomial isolates while no ESBL-producing organisms were found in the community isolates. None of the examined organisms produced MBL. Integrons were present in 22.3% of Enterobacteriaceae; 11.1% in community isolates, 23.5% in nursing-home isolates and 36% in nosocomial isolates. Integron-containing Enterobacteriaceae were more often resistant to antimicrobial agents. Multidrug resistant phenotype (70.8% vs 8.9%; p<0.001; ΟR: 24.99; 95% CI: 7.73−80.76) and ESBL production (50% vs 6.3%; p<0.001; OR: 14.8; 95% CI: 4.42−49.56) were more common in integron-carrying isolates.
CONCLUSIONS The prevalence of AB in nursing-home residents was similar to that of hospitalized patients. More than 1/5 of Enterobacteriaceae in nursing-home residents and hospitalized patients produced ESBLs whereas none of the community isolates produced these enzymes. Integrons were detected in some samples of all the bacterial populations causing AB. The highest rate of integrons was observed in hospital isolates, but there is a reservoir in the community. The presence of integrons was associated with multidrug resistance. Patients with AB in the nursing-home environment should be managed as nosocomial patients.
Key words: Asymptomatic bacteriuria, Integrons, Resistance.