ABSTRACT
Objective:To explore the resistance of common clinical isolates to chlorhexidine gluconate (CHG) and the clinical characteristics of patients with the infections.Methods:A total of 1 000 isolates from the First Affiliated Hospital of Wenzhou Medical University in 2018 (from January to May) were collected, which included 200 strains each of Escherichia coli ( E. coli), Acinetobacter baumanii ( A. baumanii), Pseudomonas aeruginosa ( P. aeruginosa), Staphylococcus aureus ( S. aureus), and Enterococcus spp.. Minimum inhibitory concentration (MIC) of CHG against 1 000 isolates were determined by the agar dilution method. The correlation between the resistance of isolates and clinical characteristics of infected patients was analyzed. Chi-square test or Fisher exact probability test were used for statistical analysis. Results:A total of 57 CHG resistant strains were detected in 1 000 clinical isolates. These CHG-resistant strains were mainly isolated from sputum and intensive care unit ward, accounting for 49.1%(28/57)and 38.6%(22/57), respectively. The resistance rates of P. aeruginosa, A. baumanii, Enterococcus spp., S. aureus, and E. coli to CHG were 16.0%(32/200), 7.0%(14/200), 3.0%(6/200), 1.5%(3/200) and 1.0%(2/200), respectively. The CHG-resistant rates of P. aeruginosa to ceftazidime, ciprofloxacin, levofloxacin and gentamicin were 53.1%(17/32), 78.1%(25/32), 65.6%(21/32) and 50.0%(16/32), respectively, which were all higher than those of CHG-sensitive P. aeruginosa (25.0%(8/32), 25.0%(8/32), 21.9%(7/32) and 15.6%(5/32), respectively), with statistical significance ( χ2=5.317, 18.080, 12.444 and 8.576, respectively, all P<0.05). The hospital mortality was 22.8%(13/57) in patients infected with CHG-resistant bacteria, which was higher than that in patients infected with CHG-sensitive bacteria ((7.0%(4/57); Fisher exact probability test, P=0.018)). CHG-resistant group had a higher history of CHG exposure and antimicrobial treatment (61.4%(35/57) and 70.2%(40/57), respectively), which were both higher than those with CHG-susceptible isolates (17.5%(10/57) and 47.4%(27/57), respectively), the differences were both statistically significant ( χ2=22.947 and 6.118, respectively, both P<0.05). In addition, the multi-drug resistance rate of CHG-resistant strains was 54.4%(31/57), which was higher than that of CHG-susceptible strains (35.1%(20/57)), the difference was statistically significant ( χ2=4.293, P=0.039). Conclusions:CHG resistant strains have higher antimicrobial resistance. Hospital mortality in patients infected with CHG-resistant bacteria is higher than patients infected with CHG-sensitive bacteria. The important risk factors are CHG exposure and antimicrobial therapy.
ABSTRACT
Objective:To investigate the role of type Ⅵ secretion system (T6SS) in the pathogenicity and antibiotic resistance of Acinetobacter baumanii. Methods:From January 1 to December 31, 2016, a total of 45 Acinetobacter baumanii isolates were collected from patients with bloodstream infection in the First Affiliated Hospital of Wenzhou Medical University. The susceptibilities to commonly used antimicrobial agents were determined by VITEK 2 Compact automatic microbiology analyzer. Detection of T6SS characteristic gene hemolysin coregulated protein ( hcp) was achieved by polymerase chain reaction. Biofilm formations, serum resistances and competition tests of T6SS-positive/negative Acinetobacter baumanii were performed in vitro. The clinical data of patients with bloodstream infection were collected and analyzed. Chi-square test, t test and Kruskal-Wallis test were conducted for statistical analysis. Results:The positive rate of T6SS in 45 Acinetobacter baumanii isolates was 53.3% (24/45). The resistance rates of T6SS-positive Acinetobacter baumanii to ceftazidime, ciprofloxdcin, gentamicin, imipenem, levofloxacin, piperacillin/tazobactam, tobramycin and cefepime (95.8%, 95.8%, 66.7%, 95.8%, 79.2%, 95.8%, 79.2%, 91.7%)were all higher than that of T6SS-negative Acinetobacter baumanii (28.6%, 28.6%, 28.6%, 28.6%, 9.5%, 23.8%, 23.8%, 28.6%), and the differences were all statistically significant ( χ2=22.12, 22.12, 6.51, 22.12, 21.83, 24.72, 13.79, 18.97, respectively, all P<0.05). The biofilm formation ability, serum resistance and competitive ability of T6SS-positive Acinetobacter baumanii were stronger than those of T6SS-negative Acinetobacter baumanii, and the differences were all statistically significant ( t=4.99, Z=-2.61 and -2.27, respectively, all P<0.05). The positive rate of T6SS isolated from intensive care unit (ICU) ward (80.0%, 16/20) was significantly higher than that from non-ICU ward (32.0%, 8/25; χ2=10.29, P<0.05). But T6SS had no effect on the prognosis of patients ( χ2=1.74, P=0.188). Conclusions:T6SS of Acinetobacter baumanii is associated with high pathogenicity, and the high drug resistance rate makes treatment extremely difficult. Physicians need to pay much attention, especially to the patients from ICU wards.