---

  Background & Objectives: Pseudomonas aeruginosa is a Gram-negative and aerobic bacterium. Exotoxin A is one of the important toxins produced by the bacterium and it is the main cause of mortality. About 90% of P. aeruginosa strains produce this toxin. Biofilm is a functional consortium of microorganisms attached to the body surfaces and bacteria are embedded in extracellular polymeric substances produced by the microorganisms. This bacterium is nontoxic in the planktonic form, but as a biofilm is highly toxic. In this study, we examined the association between the presence of exo-A gene and antibiotic resistance patterns with biofilm formation in Pseudomonas aeruginosa strains.

  Methods: In this study 110 strains of Pseudomonas aeruginosa isolated from various infections with defined antibiotic resistance patterns were used. The PCR method was used to detect the presence or absence of Exotoxin A gene (exo-A). Ability of biofilm formation was evaluated by spectrophotometry. Association between exo-A gene and antibiotic resistance patterns with biofilms formation was analyzed statistically by Fishers and Chi-square tests.

  Results: exo-A gene was detected in 93 strains (84.5%). Sixty two strains were multidrug resistant and they produced broad spectrum beta-lactamase enzyme. Results showed that, exo-A positive strains had significantly higher ability to biofilm formation in comparison with exo-A negative strains (p<0.05). Also the biofilm formation was significantly higher in multidrug resistant and ESBL producing strains (p<0.05).

  Conclusion: The results of this study indicate that there is a significant association between exo-A gene as well as antibiotic resistance pattern and ESBl producing with biofilm formation in Pseudomonas aeruginosa. Because of importance of biofilms in the pathogenesis of this bacterium, our study could open a new window for investigation of the molecular processes involved in the formation of biofilms.

---

Background & objectives: Methicillin-resistant Staphylococcus aureus is one of the most common causes of nosocomial infections.  The polysaccharide adhesion mechanism encoded by the ica operon generates a direct role in biofilm formation and infection of the bacteria. The aim of this study was to evaluate the frequency of icaA gene in Staphylococcus aureus isolates isolated from clinical specimens of patients admitted to some clinical centers of Rasht.
Methods: This descriptive, cross-sectional study was performed on 100 Staphylococcus aureus isolates from some clinical centers of Rasht in 2019 and confirmatory tests were performed to identify the bacteria. icaA gene identification and its frequency were investigated using molecular methods . The antibiotic resistance pattern against 10 antibiotics and biofilm-forming ability of the isolates were determined using the disk diffusion method and Congo red method respectively.
Results: In the present study, among the 100 studied isolates, the highest drug resistance was related to penicillin, and the lowest antibiotic resistance was belonged to ciprofloxacin. 81 isolates (81%) were resistant to methicillin and 37 isolates (37%) had multiple resistance. Of 37 isolates with multiple resistances, 32 isolates (86.48%) had icaA gene and 24 isolates (64.9%) ،had the ability to produce strong biofilms.
Conclusion: According to the findings of this study, the prevalence of Staphylococcus aureus isolates carrying icaA gene with strong biofilm forming ability and resistance to methicillin, were high. This necessitates the need for serious management of antibiotic administration.