RESUMEN
Background: Pseudomonas aeruginosa is an opportunistic pathogen involved in number of hospital-acquired infections such as catheter-associated urinary tract infections, bacteremia, septicemia, skin infections, and ventilator-associated pneumoniae. Biofilm formation is an important trait implicated in chronic infections, such as cystic fibrosis and chronic pulmonary obstruction. We evaluated effects of gentamicin, cefepime, and ciprofloxacin on biofilm of P. aeruginosa. Materials and Methods: A total of 266 isolates were collected from the Armed Forces Institute of Pathology (AFIP). Antibiotic susceptibility was assessed by double disk synergy testing. ESBL and carbapenemase detection was performed by phenotypic testing. Molecular screening of the genes was done by PCR. Micro-dilution broth method was used to determine minimum inhibitory concentrations of antibiotics. Biofilm formation was done by micro-titer plate assay. Results: Overall, 20% of the P. aeruginosa isolates were extensively drug-resistant (XDR-PA), and 25% were multi-drug-resistant (MDR-PA). Likewise, 43% of the isolates were ESBL producers, and carbapenemase production was detected in 40% of the isolates. Molecular analysis confirmed occurrence of different resistant factors in ESBL-positive isolates; 67% carried blaTEM, 62% blaCTXM-15, 41% blaSHV, 34% blaCTXM-14, and 33% blaOXA-1. In addition, 68% of the carbapenem-resistant isolates were positive for blaNDM-1, 25% for blaOXA-48, and 22% for blaKPC-2. Biofilm formation was assessed for 234 isolates, out of which 28% were strong biofilm formers. Moderate and weak biofilm formers constituted 46% and 23%, respectively. Overall, ciprofloxacin, levofloxacin, and cefepime showed inhibitory effects on P. aeruginosa biofilms. Antibiotics in combination showed strong synergistic effects (ciprofloxacin and cefepime), while gentamicin and cefepime resulted in complete eradication of P. aeruginosa biofilm. Conclusion: We confirm strong synergistic effects of gentamicin and cefepime that completely eradicated P. aeruginosa biofilm. We further confirm inhibitory effects of ciprofloxacin, levofloxacin, and cefepime on P. aeruginosa biofilms. Hence, combination therapy can be more effective against biofilm-associated infections.
RESUMEN
BACKGROUND: Community-acquired urinary tract infections are associated with significant morbidity, and uropathogenic Escherichia coli (UPEC) alone causes 90% of urinary tract infections. This bacterium retains a diverse armament of virulence factors including fimbria, hemolysins, and siderophores production. In a post invasion scenario, formation of intracellular communities mimic biofilm-like characteristics and are linked to recurrent urinary tract infections. We investigated the effects of different frontline antibiotics on the formation, inhibition, and eradication of biofilms of virulent UPEC strains. MATERIALS AND METHODS: A total of 155 UPEC strains were scrutinized for various virulence factors including gelatinase, cell surface hydrophobicity, hemagglutination, and serum bactericidal activity. Biofilm formation was confirmed by three different methods: Congo red agar, test tube, and tissue culture plate method. Biofilm inhibition and eradication assays were performed according to the standard protocols. Topographical analysis of biofilms was done by scanning electronic microscopy (SEM). RESULTS: Out of 155 strains, 113 (73%) were strong biofilm formesr, while 37 (24%) produced biofilms at moderate level. Significant differences were observed between MICs of planktonic cells (MIC-p) and MICs of UPEC biofilms (MIC-b). Among tested frontline antibiotics, levofloxacin successfully inhibited biofilms at a concentration of 32 µg/mL, while trimethoprim eradicated biofilms at higher concentrations (512-1024 µg/mL). Ciprofloxacin treatment at sub-MIC level significantly enhanced biofilm formation (P<0.05). CONCLUSION: The majority of UPEC strains are strong biofilm formers and show higher tolerance towards frontline antibiotics in biofilm form. We observed significant inhibitory effects of levofloxacin (32 µg/mL) on UPEC biofilms, while treatment with sub-minimal concentrations of ciprofloxacin significantly enhanced biofilm formation. Out of all tested antibiotics, trimethoprim (512-1024 µg/mL) eradicated UPEC biofilms.