The effect of molecules in bacterial slime layer structure upon bacterial adherence and antibiotic resistance

THE EFFECT OF MOLECULES IN BACTERİAL SLİME LAYER STRUCTURE UPONBACTERİAL ADHERENCE AND ANTİBİOTİC RESİSTANCE:Introduction: Biofilms are microbially derived sessile community characterized by cells that areirreversibly attached to a substratum or interface or to each other. They embedded in a matrix ofextracellular polymeric substances that they have produced, and exhibit an altered phenotypewith respect to growth rate and gene transcription.Aim: Biofilm?s structured is not well defined, carbohydrate content may plays an important rolein biofilm?s functions in physiological systems. We hypothesized that sialic acid may take part incarbohydrate structure of slime and may play a critical role in antimicrobial resistance andbacterial adherence.Material and Methods: In this study we examined 63 coagulase negative staphylococci (CNS)and 91 Enterococcus spp obtained from various clinical isolates. The production of slime from allstrains was studied by means of two different methods: the Christensen method (qualitative tubemethod) and quantitative microdilution plate. Optical density (OD) of well content wasdetermined at 595 nm (OD595) using a microplate reader and strains which optical density wasgreater then 1 consider that slime positive. The antibiotic susceptibility of strains was determinedthat disc diffusion and microdilution broth methods which recommended that NCCLS M2-A8and M100-S13. To determine neuraminidase effect on slime formation and antibiotic resistance,bacteria (0.5 McFarland) were treated with neuraminidase and/or neuraminidase with increasingdose of antibiotics in 96 well U bottom plates. For slime formation plates were stained withcrystal violet and examined at 590 nm and for antibiotic resistance directly examined at 625 nmspectrophotometrically.Results: Adherence of slime-forming CNS and enterococcus were greater than non-slimeforming bacteria. Antibiotic resistance in slime-forming CNS is greater than non-slime formingCNS group. In enterococcus group, antibiotic resistance to ampicillin and penicillin in slime-forming bacteria was statistically significant. Rifampicin and ciprofloxacin resistance in slime-forming enterococcus was greater than non-slime forming enterococcus but statistically was notsignificant. Surface sialic acid mobilization by neuraminidase reduce slime formation in CNS andstatistically significant. This reduction also seen in enterococcus group but it?s not statisticallysignificant. In both group neuraminidase did not effect on bacterial adherence and growth.Treatment of bacteria with neuraminidase and increasing dose of ciprofloxacin in CNS decreasedthe slime formation, on the other hand in enterococcus treatment of neuraminidase withincreasing dose of vancomycin had not effect in slime formation and in both group,neuraminidase treatment with antibiotics did not effect bacterial adherence.Conclution: The aim of the study was to show the neuraminidase effect on slime formation,bacterial adherence and antibiotic resistance. It?s obvious that the neuraminidase has limitedeffect on slime formation of bacteria with or without antibiotics. We speculate that this resultsindicate, the sialic acid is one of the carbohydrate contents of slime and modulation of sialic acidmay potential therapeutic target for chronic infections calls by slime-forming bacteria and needmore studies on this subject. Also this study is the first study in literature that showsneuraminidase effect on enterococcus biofilm formation.Key words: Biofilm, adherance, neuraminidase, sialic acid