Detection of biofilm formation among the clinical isolates of Staphylococci: An evaluation of three different screening methods

Abstract

Purpose: The purpose of this study was to evaluate three methods for detection of biofilm formation in staphylococci. Methods: For detection of biofilm formation, 152 clinical isolates of Staphylococcus spp. were screened by tissue culture plate (TCP), Tube method (TM) and Congo red agar (CRA) method. Results: Of the 152 Staphylococcus spp. 88(57.8%) displayed a biofilm-positive phenotype under the optimized conditions in the TCP method and strains were further classified as high 22 (14.47 %) and moderate 60 (39.4 %) while in 70 (46.0 %) isolates weak or no biofilm was detected. Though TM correlated well with the TCP test for 18 (11.8 %) strongly biofilm producing strains, weak producers were difficult to discriminate from biofilm negative isolates. Screening on CRA does not correlate well with either of the two methods for detecting biofilm formation in staphylococci. Conclusion: The TCP method was found to be most sensitive, accurate and reproducible screening method for detection of biofilm formation by staphylococci and has the advantage of being a quantitative model to study the adherence of staphylococci on biomedical devices. Key words: Staphylococci, adherence, biofilm, tissue culture plate, Congo red agarStaphylococci are most often associated with chronic difficult to eradicate and are often resistant to systemic infections of implanted medical devices.1-3 The use of antibiotic therapy and removal of infected device becomes indwelling medical devices is important in the treatment of necessary.9-11 The differentiation of staphylococci with respect critically and chronically ill patients, however bacterial to its biofilm phenotype might help to elucidate the impact colonization of implanted foreign material can cause major of staphylococci in diagnosis of infections related to medical and economic sequel. The increased use of indwelling biomedical devices and these observations may have utility medical devices has had considerable impact on the role of in the prevention of device related infections. 12 staphylococci in clinical medicine. The predominant species isolated in these infections are Staphylococcus epidermidis A number of tests are available to detect slime production and Staphylococcus aureus,their major pathogenic factor being by staphylococci; methods include tissue culture plate (TCP), ability to form biofilm on polymeric surfaces. 4 Biofilm 13 tube method (TM), 14 Congo red agar (CRA), 15,17 consists of multilayered cell clusters embedded in a matrix bioluminescent assay 18 and light or fluorescence microscopic of extracellular polysaccharide (slime), which facilitates the examination. 19,20 These methods are often subject to severe adherence of these microorganisms to biomedical surfaces and analytical limitations and are unable to detect bacterial protect them from host immune system and antimicrobial adherence accurately. In this study, we simultaneously therapy.5 screened 152 clinical isolates of Staphylococcus spp. by TCP (standard and modified), TM and CRA methods for Biofil...

Several Virulence Factors of Multidrug-Resistant Staphylococcus aureus Isolates From Hospitalized Patients in Tehran

“…In Hou's study, among 55.56% of isolates that produced biofilm in phenotypic test, 11.11% contained the icaA gene (26), but the other genes has not been investigated. In this study, methicillin resistant isolates harbored higher rate of icaADBC genes compared to MSSA, but no significant difference was confirmed, similar to two other studies (27,28). Moreover, Smith determined no significant relation between susceptibility to methicillin and biofilm formation (29).…”

Evaluation of different detection methods of biofilm formation in the clinical isolates

“…Addition of sugar helps in biofilm formation. 16,17 This was also reported by studies conducted by Mathur et al 13 and Bose et al 18 Tube method detected 49% isolates as biofilm producers and 51% as non-biofilm producers. By this method, three isolates were found to be false positive and 19 were false negative.…”

“…In accordance with the preceding studies, TM cannot be suggested as general screening test to identify biofilm producing isolates. 8,13 In another study, Ruzicka et al 19 noted that out of 147 isolates of S. epidermidis, TM detected biofilm formation in 79 (53.7%) and CRA detected in 64 (43.5%) isolates. They showed that TM is better for biofilm detection than CRA.…”

“…Regional data from India also showed that out of 152 isolates tested, the number of biofilm producers identified by TCP method was 53.9 %, and non-biofilm producers were 46%. 13 We have performed the TCP method by addition of 1% glucose in trypticase soy broth. Addition of sugar helps in biofilm formation.…”

“…7 is considered the gold-standard method for biofilm detection. 13 Organisms isolated from fresh agar plates were inoculated in 10 mL of trypticase soy broth with 1% glucose. Broths were incubated at 37 o C for 24 h. The cultures were then diluted 1:100 with fresh medium.…”