The rapid increase of drug resistance and failure of available antibiotics to treat biofilm-associated infections is of great health concern. Accordingly, our study aimed to evaluate the synergistic antibacterial, biofilm inhibitory, and biofilm removal activities of melittin in combination with colistin, imipenem, and ciprofloxacin against multidrug-resistant (MDR) strong biofilm producer Acinetobacter baumannii isolates. The kinetics of biofilm formation were evaluated for the isolates for 144 h. Minimum inhibitory concentrations (MICs), minimum bactericidal concentrations (MBCs), minimum biofilm inhibitory concentrations (MBICs), and biofilm removal activities for melittin and combinations with antibiotics were determined. Inhibition of biofilm-associated protein (bap) expression by melittin was evaluated with real-time polymerase chain reaction (PCR). Field emission scanning electron microscopy (FE-SEM) was used to visualize the effect of synergism on the inhibition of biofilm production. The geometric means of the fractional inhibitory concentration index (FICi) for melittin-colistin, melittin-imipenem, and melittin-ciprofloxacin combinations were calculated as 0.31, 0.24, and 0.94, respectively. Comparing the geometric means of the removal activity for melittin, colistin, imipenem, and combinations of them in both 6 and 24 h showed a significant difference between the groups (p-value < 0.05). Exposure to melittin induced a statistically significant downregulation of bap mRNA levels in all isolates at sub-MIC doses. Analysis of the FE-SEM results demonstrated that the synergism of melittin-colistin at 0.125-0.25 μg inhibited biofilm formation completely. In conclusion, our findings indicate that melittin possesses considerable potential for use in combination with colistin and imipenem to treat infections caused by MDR strong biofilm producer A. baumannii isolates.
Background: Multi-drug resistant (MDR) Acinetobacter baumannii is one of the most important causes of nosocomial infections. The purpose of this study was to identify antibiotic resistance patterns, biofilm formation and the clonal relationship of clinical and environmental isolates of A. baumannii by Pulsed Field Gel Electrophoresis method. Forty-three clinical and 26 environmental isolates of the MDR A. baumannii were collected and recognized via API 20NE. Antibiotic resistance of the isolates was assessed by the disk diffusion method, and the biofilm formation test was done by the microtiter plate method. Pulsed Field Gel Electrophoresis (PFGE) was used to assess the genomic features of the bacterial isolates. Results: The resistance rate of clinical and environmental isolates against antibiotics were from 95 to 100%. The difference in antibiotic resistance rates between clinical and environmental isolates was not statistically significant (p > 0.05). Biofilm production capabilities revealed that 31 (44.9%), and 30 (43.5%) isolates had strong and moderate biofilm producer activity, respectively. PFGE typing exhibited eight different clusters (A, B, C, D, E, F, G, and H) with two significant clusters included A and G with 21 (30.4%) and 16 (23.2%) members respectively, which comprises up to 53.6% of all isolates. There was no relationship between biofilm formation and antibiotic resistance patterns with PFGE pulsotypes. Conclusions: The results show that there is a close relationship between environmental and clinical isolates of A. baumannii. Cross-contamination is also very important that occurs through daily clinical activities between environmental and clinical isolates. Therefore, in order to reduce the clonal contamination of MDR A. baumannii environmental and clinical isolates, it is necessary to use strict infection control strategies.
Background:
Pseudomonas aeruginosa is a gram-negative non-glucose fermenting aerobic bacterium and an opportunistic pathogen in humans and animals. The present study was carried out in order to investigate the distribution of virulence factors and antibiotic resistance properties of P. aeruginosa isolated from patients and intensive care unit (ICU) environment.
Material and Methods:
A total of 116 P. aeruginosa isolated from patients and ICU environment were collected from Besat hospital in Hamadan, west of Iran. P. aeruginosa isolates were analyzed based on the presence of the virulence factors encoding genes included exo A, exo S, exo U, and alg D using polymerase chain reaction (PCR). Antimicrobial susceptibility test was performed using a disk diffusion method.
Results:
The results showed the prevalence of exo A 33 (56.9%), exo S 21 (36.20%), exo U 37 (63.8%), and alg D 35 (60.34%) genes in ICU environment P. aeruginosa strains and exo A 23 (39.25%), exo S 25 (43.1%), exo U 40(68.98%), and alg D 25 (43.1%) genes in clinical isolates of P. aeruginosa. High resistance levels of the clinical and ICU environment isolate to ampicillin-sulbactam (100%), were observed too.
Conclusions:
Our findings should raise awareness about antibiotic resistance in hospitalized patients in Iran. Clinicians should exercise caution in prescribing antibiotics, especially in cases of human infections.
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