The MtP method was used as the gold standard in these calculations.
The PCR technique was performed for icaAD and aap genes in all the 146 staphylococcal strains. As shown in Table 1, the majority of tested isolates (106/146; 72.6%) were ica negative, among which ica−aap+ was the dominant genotype (76/106; 71.7%). Among the ica-positive isolates (40/146, 27.4%), the ica+aap+ genotype was the most common (34/40; 85.0%). Out of the total 146 S. epidermidis nasopharyngeal isolates, 52 (35.62%) were biofilm positive by the MtP method, while 86 (58.9%) isolates exhibited a slime-positive phenotype by the CRA test (Table 1). The prevalence of the IDO inhibitor icaAD and the aap genes in relation to biofilm-positive (by the MtP selleck kinase inhibitor method) and slime-positive (by the CRA test) phenotypes of nasopharyngeal S. epidermidis isolates was analyzed (Table 1). Thirty-one (59.6%) of 52 biofilm-positive isolates by the
MtP method were positive for icaAD and aap genes, whereas six (11.5%) strains were ica positive and aap negative. However, among the biofilm-negative isolates by the MtP method, three isolates with the ica+aap+ genotype were found. Most of the ica-positive isolates were found to be strong biofilm producers. Most of the ica-negative strains (91/106; 85.8%) did not produce a detectable amount of biofilm in vitro, including 68 isolates harboring the aap gene. Fifteen (28.8%) isolates Tolmetin produced an ica-independent biofilm, including eight (15.4%) aap-positive and seven (13.5%) aap-negative strains. Interestingly, two out of ica−aap− isolates were strong biofilm producers. Among 40 of the ica-positive strains, 39 were classified as slime producers by the CRA test (Table 1). However, out of 106 ica-negative isolates, 47 were slime positive. The concordance between the occurrence of icaAD genes and the ability of biofilm formation determined by the MtP method as well as slime
production examined by the CRA test was statistically significant (P<0.0001). There was no relationship between aap occurrence and biofilm formation (P=1) or slime production (P=0.56) (Table 1). The data obtained using the CRA and MtP methods among ica-positive and ica-negative staphylococci are presented in Table 2. The strains that yielded matching results using both the CRA and the MtP methods were 84 (57.5%) of all the strains screened. For all the strains tested, the sensitivity of the CRA test evaluated using the MtP method as a gold standard of biofilm production was 73.1%. The differentiation of the sensitivity of the CRA test was observed when ica-positive and ica-negative staphylococcal strains were analyzed separately (97.3% and 13.3%, respectively). In our study, the ability of biofilm formation in vitro by 146 nasopharyngeal S. epidermidis isolates was assessed using two variations of medium: TSB (standard conditions) and TSB supplemented with 0.