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Table 3 Minimum inhibitory concentration (MIC) values of biofilm forming and non-forming isolates as detected by possession of icaAD genes

From: High level of persister frequency in clinical staphylococcal isolates

Antibiotics icaAD Antibiotics icaAD
Positive
(n = 86)
Negative
(n = 289)
P value Positive
(n = 86)
Negative
(n = 289)
P value
Oxacillin Tetracycline
 Range 0.125- > 32 0.125- > 32    Range 0.125- > 4 0.125- > 4  
 MIC50 2 1    MIC50 0.5 0.5  
 MIC90  > 32 32    MIC90 1 2  
 % resistance 44.6% 37.2%  % resistance - - 0.217
Vancomycin Clindamycin
 Range 0.125- > 4 0.125- > 4    Range 0.125- > 512 0.125- > 512  
 MIC50 1 2    MIC50 0.125 0.125  
 MIC90 2 4    MIC90 8 128  
 % resistance - -  % resistance 10.5% 14.5% 0.069
Cotrimoxazole Penicillin
 Range 0.5/9.5- > 16/304 0.5/9.5- > 16/304    Range 0.125- > 8 0.125- > 8  
 MIC50 0.5/9.5 16    MIC50 0.25 0.5  
 MIC90 16/304  > 16/304    MIC90 2 2  
 % resistance 32.6% 42.9% 0.045  % resistance - - 0.023
Erythromycin Ciprofloxacin
 Range 0.125- > 512 0.125- > 512    Range 0.125–520 0.125–520  
 MIC50 32 32    MIC50 8 4  
 MIC90 512  > 512    MIC90 64 128  
 % resistance 59.3% 63.3% 0.003  % resistance 46.5% 24.9% 0.015
Chloramphenicol Gentamicin
 Range 0.125- > 16 1- > 16    Range 0.125- > 64 0.125- > 64  
 MIC50 4 4    MIC50 1 1  
 MIC90 8 8    MIC90 64 64  
 % resistance 3.8% 2.3% 0.516  % resistance 23.3% 26.6% 0.231
  1. The MICs values of were determined by the agar dilution method. The sensitivity towards the antibiotics was evaluated among biofilm forming and non-forming isolates based on icaAD genes. The Chi-square test was performed to see the association between MIC value and biofilm formation ability taking P < 0.05 statistically significant.
  2. *The resistant range of MIC values of oxacillin and vancomycin is different for S. aureus and CNS. For this reason, p value is not mentioned in the table. The sensitivity of oxacillin (n = 20, 44.4%) in biofilm producers (n = 45) vs sensitivity (n = 63, 54.3%) in biofilm non-producers S. aureus was significantly different (p = 0.006). Likewise, the sensitivity of oxacillin (n = 30, 73.2%) in biofilm producers (n = 41) vs sensitivity (n = 142, 82.1%) in biofilm non-producers (n = 173) CNS were significantly different (p = 0.012). Irrespective of whether biofilm producers or not, all the isolates were sensitive towards vancomycin (Supplementary Table 2).