Mohammad Reza SHAKİBAİE, Yasser GOLKARİ, Gholamabas SALAGEGHEH

Antimicrobial susceptibility, virulence factors and biofilm formation among Staphylococcus aureus strains from hospital infections in Kerman, Iran

Amaç: Bu çalışma hastane kaynaklı Staphylococcus aureus suşlarının antimicrobial duyarlılık, virülans faktör ve biyofilm oluşturma özelliklerini belirlemeyi hedeflemektedir. Metotlar: İran, Kerman’da 30 adet, tekrarlamayan S. aureus suşu hastanelerden izole edildi. Antimicrobial duyarlılıklar disk diffüzyon metoduyla CLSI rehberinin sınırdeğerlerine göre çalışıldı. Vankomisin ve metisilin için minimum inhibitor konsantrasyonu (MİK) sıvı mikrodilüsyon ve E-test prosedürleri ile belirlendi. Bu suşlarla birlikte olan virülans faktörleri (proteaz, DNaz, lesitinaz, kapsül ve hemoliz) çalışıldı. Biyofilm değerlendirmesi mikrotitre tekniği ile miktarı belirleme şeklinde yapıldı. Bulgular: Toplam olarak 14 (% 46, 7) S. aureus suşu alt solunum yollarından, altı suş (% 20,0) üriner sistemden ve kalan 10 suş (% 33,3) yaralar, kan ve ortopedi hastalarından izole edildi. Bütün suşlar tigesikline duyarlıydı, sekiz suş (% 26,7) metisiline dirençli (MRSA) bulundu ve dört suş (% 13,3) vankomisine azalmış duyarlılık gösterdi. Suşların hiç biri vankomisine dirençli değildi (p≤0.05). MİK sonuçları; vankomisin için suşlardan dördünde (% 13,3) MİK 4 µg/mL olarak bulunurken beşinde (% 16,6) metisilin için MİK 32 µg/mL olarak bulundu. Suşlar aynı zamanda amoksisilin/klavulanik asit, tekrasiklin ve tobramisine dirençli idiler. MSSA suşları ile karşılaştırıldığında MRSA suşlarından 6’si (% 75,0) lesitinaz, yedisi (% 96,7) proteaz ve DNaz aktivitesi gösterdi. Yirmi suş (% 66,7) kuvvetli, yedi suş (% 23,3) orta ve üç suş (% 10,0) zayıf biyofilm yapmaktaydı.Sonuç: Bu sonuçlardan bu enfeksiyonlarda tedavi seçeneklerinin sınırlı olduğu anlaşılmaktadır. Bundan dolayı vankomisine duyarlılığı azalmış MRSA suşlarının etken olduğu enfeksiyonların izlenmesi ve yönetimi bu suşların hastane ortamına yayılmasının kontrolüyle yapılmalıdır

Anahtar Kelimeler:

Staphylococcus aureus, metisilin direnci, MİK, virülans faktörleri, biyofilm

Antimicrobial susceptibility, virulence factors and biofilm formation among Staphylococcus aureus isolates from hospital infections in Kerman, Iran

Objective: The aims of present study were to determine the antimicrobial susceptibility, virulence factors and biofilm formation among MRSA hospital isolates of Staphylococcus aureus. Methods: Thirty non-repetitive strains of S. aureus isolated from three hospitals in Kerman, Iran. Antimicrobial susceptibility was determined by disk diffusion breakpoints method according to CLSI guideline. The minimum inhibitory concentration (MIC) of vancomycin and methicillin were measured by the broth microdilution and E-test procedures. Virulence factors (protease, DNase, lecithinase, capsule and hemolysis) associated with the above isolates was studied. Biofilm was quantified by microtiter technique. Results: In total, 14 (46.7%) S. aureus were isolated from lower respiratory tract, six (20.0%) from urinary tract and remaining 10 (33.3%) were recovered from wounds, blood and orthopedic patients. All of the isolates were susceptible to tigecycline, eight (26.7%) were found to be resistant to methicillin (MRSA) and 4 (13.3%) showed reduced susceptibility to vancomycin. No any vancomycin resistant isolate was detected (p≤0.05). MIC results showed that four of the isolates (13.3%) exhibited MIC 4 μg/mL to vancomycin while, five (16.6%) demonstrated MIC 32 μg/mL to methicillin. The isolates were also resistant to amoxicillin/clavulanic acid, tetracycline and tobramycin. It was found that, six (75 %) of MRSA strains produced lecithinase, seven (96.7%) demonstrated protease and DNase activities as compared to MSSA isolates. Biofilm analysis revealed that twenty (66.7%) isolates formed strong, seven (23.3%) formed moderate and three (10.0%) had weak biofilm. Conclusion: From the results, it can be concluded that, treatment options available for these infections are limited; therefore, monitoring, and management of infections due to MRSA with reduced susceptibility to vancomycin, must be done in order to control spread of these strains in the hospital environment.

Keywords:

Staphylococcus aureus, methicillin resistance, MIC, virulence factor, biofilm,

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