A total of 462 Escherichia coli , and 1,305 Staphylococcus aureus strains were collected in clinical isolates during a 32month period (February 2007 to September 2009) at Kizawa Memorial Hospital. One hundred twenty isolates of E. coli produced extended-spectrum Β-lactamase (ESBL), and 612 isolates of S. aureus were methicillin-resistant, suggesting that antibiotic resistant-bacteria were spreading in our hospital. The investigation we carried out resulted in clarifying the frequencies of occurrence and realities of ESBL-producing E. coli as well as the extent of MRSA, and infection control measures were improved. In addition to providing the opportunity to review the infection control measures in our hospital, it underlined the importance of monitoring antibiotic-resistant bacteria.
The administration of antimicrobial agents to 17,128 patients from January 2007 to June 2009 was analyzed through multivariate analysis using logistic regression. Significant risk factors influencing the occurrence of ESBL-producing E. coli were : age (Odds rate (OR) 1.022, 95% confidence interval (CI) 1.016∼1.028), history of hospital stay (OR 2.742, CI 1.400∼5.373), and number of times antimicrobials used (OR 1.026, CI 1.019∼1.032). Those for MRSA were : male sex (OR 1.279, CI 1.137∼1.438), age (OR 1.021, CI 1.018∼1.024), history of hospital stay (OR 1.698, CI 1.298∼2.221), and antimicrobial usage period (OR 1.056, CI 1.049∼1.063).
In conclusion, antimicrobial use may be creating a favorable environment for colonization by antibiotic-resistant bacteria.
