학술논문
UČINAK SUBMINIMALNIH INHIBITORNIH KONCENTRACIJA ANTIBIOTIKA NA SPOSOBNOST STVARANJA BIOFILMA I OSJETLJIVOST NA BAKTERICIDNU AKTIVNOST LJUDSKOG SERUMA KLINIČKIH IZOLATA ACINETOBACTER BAUMANNII U IN VITRO UVJETIMAIn vitro effect of subminimal inhibitory concentrations of antibiotics onto biofilm production and sensitivity of human serum bactericidal activity in Acinetobacter baumannii clinical isolates.
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TEXT
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Croatian
Abstract
Cilj istraživanja: Acinetobacter baumannii je jedan od vodećih uzročnika oportunstičkih infekcija vezanih uz zdravstvenu skrb. Činitelji virulencije nisu još dovoljno poznati, a obzirom na brzu propagaciju u bolničkom okružju i brzo stjecanje mehanizama rezistencije, predstavlja veliki zdravstveni problem. Cilj istraživanja bio je utvrditi učinak subminimalnih inhibitornih koncnetracija imipenema, ampicilin/sulbaktama, azitromicina, rifampicina i kolistina na sposobnost stvaranja biofilma i osjetljivost na baktericidnu aktivnost ljudskog seruma kliničkih izolata A. baumannii Materijal i metode:Iz zbirke kliničkih izolata A. baumannii, na temelju sposobnosti stvaranja biofilma u mikrotitar pločici, formirane su 2 ispitivane skupine s po 34 ispitivana soja kojima, je utvrđena osjetljivost na baktericidnu aktivnost ljudskog seruma. Sojevima su određene minimalne inhibitorne koncentracije imipenema, ampicilin/sulbaktama, azitromicina, rifampicina i kolistina. Zatim su ispitivani sojevi tijekom 18-24 sata izlagani 1/2, 1/4, 1/8 i 1/16 ispitanog MIK-a. Nakon izlaganja sub-MIK-u antibiotika, ponovno je u prema istim kriterijima u mikrotitar pločici određena sposobnost stvaranja biofilma, kao i brojanjem poraslih bakterijskih kolonija na površini Mueller Hinton agara, određen postotak preživljenja bakterijskih stanica nakon izlaganja normalnom i toplinom inaktiviranom ljudskom serumu. Rezultati: 65/68 ispitivanih sojeva A. baumannii rezistentno je na baktericidnu aktivnost ljudskog seruma. Sub-MIK-e imipenema i azitromicina su imale statistički značajan učinak na supresiju stvaranja biofilma u 34 biofilm producirajuća soja pri sve četiri ispitivane koncentracije ispod MIK-a. U ispitivanoj je skupini postignut statistički značajan učinak rifampicina u 1/2 i 1/4 MIK-a, za kolistin, učinak je značajan pri 1/2 i 1/8 MIK-a. Statistički značajan učinak ispitivanja osjetljivost ispitivanih sojeva prema baktericidnoj aktivnosti ljudskog seruma je postignut za ampicilin/sulbaktam i azitromicin u sve četiri ispitivane koncentracije ispod MIK-a. Zaključak: Sub-MIK azitromicina ima učinak na oba ispitivana svojstva, supresiju stvaranja biofilma i osjetljivost na baktericidnu aktivnost seruma. Stvaranje biofilma suprimiraju imipenem, rifampicin i kolistin, a pored azitromicina, samo ampicilin/sulbaktam ima učinak na osjetljivost prema baktericidnoj aktivnosti seruma. Ispitivani antibiotici nisu pokazali sposobnost indukcije stvaranja biofilma u ispitivanih A. baumannii sojeva.
Objectives: Acinetobacter baumannii is one of the main causers of opportunistic nosocomial infections. Regarding its ability of rapid dissemination in hospital enviorment and acquiring mechanisms of antimicrobial resistance, it represents global healthcare-associated problem. Its virulence factors and resistance mehanisms, due to which it can rapidly colonise and infect patients, are still underestimated and poorly understood. The aim of this study was to evaluate in vitro effect of subminimal inhibitory concentrations of imipenem, ampicilin/sulbactam, azithromycin, rifampicin and colistin onto the ability of biofilm formation and sensitivity to bactericidal activity of human serum of clinical A. baumannii isolates. Material and methods: From the collection of A. baumannii isolates, based on microtiter biofilm formation assay, two groups were formed: one group containing 34 A. baumannii biofilm positive, and another with 34 biofilm negative isolates.Serum bactericidal tests were performed and serum sensitivity was detected by colony count after exposure to undiluted human serum for two hours. Serum sensitive isolates were the ones with viabile cell count <10% in comparison to control. MICs for imipenem, ampicilin/sulbactam, azithromycin, rifampicin and colistin were detected and after 18-24 hour exposition of isolates to antibiotic concentrations ½, ¼, ⅛ i 1/16 of MIC, the microtiter biofilm formation assay and serume bactericidal tests again conducted to determine effect of antibiotic subMICs onto these two virulence determinants. Results: Sixty-five of sixty-eight tested strains accounted for resistant to human serum. All tested imipenem and azithtromycin subMICs exhibited statistically significant suppression of biofilm formation in biofilm positive strains. The effect of rifampicin was statistically significant in biofilm formation at ½ and ¼ of MIC, as well as for colistin at ½ and ⅛ of MIC. Statistically significant effect of sensitivity to human serum bactericidal effect was detected for ampicilin/sulbactam and azithromycin at all four tested concentrations bellow MIC. Conclusion: Azithromycin exhibited the best effect among tested antibiotics. It suppressed biofilm formation and had serum bactericidal activity enhanced. Biofilm formation was impaired when medium containing ampicilin/sulbactam was used. Nontheless, rifampicin, imipenem and colistin also exhibited significantly different biofilm formation production suppression. Ampicilin/sulbactam also established effect on serum resistance. Ability to induce biofilm formation was not detected.
Objectives: Acinetobacter baumannii is one of the main causers of opportunistic nosocomial infections. Regarding its ability of rapid dissemination in hospital enviorment and acquiring mechanisms of antimicrobial resistance, it represents global healthcare-associated problem. Its virulence factors and resistance mehanisms, due to which it can rapidly colonise and infect patients, are still underestimated and poorly understood. The aim of this study was to evaluate in vitro effect of subminimal inhibitory concentrations of imipenem, ampicilin/sulbactam, azithromycin, rifampicin and colistin onto the ability of biofilm formation and sensitivity to bactericidal activity of human serum of clinical A. baumannii isolates. Material and methods: From the collection of A. baumannii isolates, based on microtiter biofilm formation assay, two groups were formed: one group containing 34 A. baumannii biofilm positive, and another with 34 biofilm negative isolates.Serum bactericidal tests were performed and serum sensitivity was detected by colony count after exposure to undiluted human serum for two hours. Serum sensitive isolates were the ones with viabile cell count <10% in comparison to control. MICs for imipenem, ampicilin/sulbactam, azithromycin, rifampicin and colistin were detected and after 18-24 hour exposition of isolates to antibiotic concentrations ½, ¼, ⅛ i 1/16 of MIC, the microtiter biofilm formation assay and serume bactericidal tests again conducted to determine effect of antibiotic subMICs onto these two virulence determinants. Results: Sixty-five of sixty-eight tested strains accounted for resistant to human serum. All tested imipenem and azithtromycin subMICs exhibited statistically significant suppression of biofilm formation in biofilm positive strains. The effect of rifampicin was statistically significant in biofilm formation at ½ and ¼ of MIC, as well as for colistin at ½ and ⅛ of MIC. Statistically significant effect of sensitivity to human serum bactericidal effect was detected for ampicilin/sulbactam and azithromycin at all four tested concentrations bellow MIC. Conclusion: Azithromycin exhibited the best effect among tested antibiotics. It suppressed biofilm formation and had serum bactericidal activity enhanced. Biofilm formation was impaired when medium containing ampicilin/sulbactam was used. Nontheless, rifampicin, imipenem and colistin also exhibited significantly different biofilm formation production suppression. Ampicilin/sulbactam also established effect on serum resistance. Ability to induce biofilm formation was not detected.