A comparative analysis of phenotypic and genotypic methods for the determination of the biofilm-forming abilities of Staphylococcus epidermidis

Abstract

The collection of 146 Staphylococcus epidermidis strains isolated from the nasopharynx of lung cancer patients has been studied for the ability of slime secretion and biofilm formation using the Congo red agar (CRA) test and the microtiter plate (MtP) method, respectively. The prevalence of the icaAD and the aap genes was also analyzed. Some isolates (35.6%) were biofilm positive by the MtP method, while 58.9% of isolates exhibited a slime-positive phenotype by the CRA test. The sensitivities of the CRA test evaluated using the MtP method as a gold standard of biofilm production were 73.1%, 97.3% and 13.3% for all the strains screened, ica-positive and ica-negative strains, respectively. The genotype ica(+)aap(+) was correlated with a strong biofilm-producer phenotype. Interestingly, some of the ica(-)aap(-) isolates could also form a biofilm. The correlation between the presence of icaAD genes and the biofilm-positive phenotype by the MtP method as well as slime production by the CRA test was statistically significant (P<0.0001). However, some S. epidermidis strains possess the potential ability of ica-independent biofilm formation; thus, further studies are needed to determine reliable, short-time criteria for an in vitro assessment of biofilm production by staphylococci.

Staphylococcus epidermidis pan-genome sequence analysis reveals diversity of skin commensal and hospital infection-associated isolates

“…By this assay, we found that biofilm formation was widespread amongst both commensal and nosocomial S. epidermidis isolates. The ica genes, encoding biofilm-associated genes for poly- N -acetylglucosamine synthesis, were found in only 60% of the biofilm-forming commensal isolates, in agreement with previous studies [31]. This suggests genetic heterogeneity underlying the mechanism by which S. epidermidis forms a biofilm.…”

Antibiotic resistance and biofilm production among the strains of Staphylococcus aureus isolated from pus/wound swab samples in a tertiary care hospital in Nepal

“…The detection of biofilm production among the strains of S. aureus was performed by microtiter plate method [11]. The S. aureus was grown in 96 welled microtiter plate containing trypticase soya broth with 2% glucose, at 35 °C for 48 h. The optical density value of the bacteria that coat the wall of the wells was determined with the help of enzyme linked immunosorbent assay reader after staining with crystal violet.…”

Accumulation-Associated Protein Enhances Staphylococcus epidermidis Biofilm Formation under Dynamic Conditions and Is Required for Infection in a Rat Catheter Model

“…3). This result was not necessarily surprising, as our experience and that of others (53,66,73) suggests in vitro static biofilm assays essentially measure PIA synthesis and a hallmark of 1457 is constitutive production of PIA (9,49,53). Therefore, to determine the contribution of Aap in biofilm accumulation in the absence of PIA, bacteriophage 71 was used to transduce the aap::tetM marker from 1457 ⌬aap into 1457 ⌬ica (53), generating 1457 ⌬ica ⌬aap.…”

“…Microtiter plate assays were based on the procedure of Christensen et al, with modifications (65,66). Overnight planktonic cultures were diluted 1:100 in fresh TSB.…”