Figure 1Agarose gel electrophoresis of icaA (A) and icaD (B) genes in S epidermidis isolates. Lanes 1–3 = PCR products of the corresponding genes; M= 50 bp DNA marker; N = negative control; P = positive control.
Table 1Interpretation of biofilm by the microtiter plate method.
Mean OD value |
Biofilm formation |
OD ≤ ODc *
|
None |
ODc < OD ≤ 2× ODc |
Weak |
2× ODc < OD ≤ 4× ODc |
Moderate†
|
4× ODc < OD |
Strong†
|
Table 2Results of three biofilm formation detection assays and ica genes detection among the 41 S epidermidis clinical isolates.
Characteristics (No.) |
No. (%) of biofilm formation |
No. (%) of gene present |
MTP |
TM |
CRA |
icaA
|
icaD
|
Clinical specimen |
|
Blood (25) |
15 (60) |
15 (60) |
6 (24) |
25 (100) |
23 (92) |
Tracheal aspirate (6) |
3 (50) |
4 (67) |
1 (17) |
6 (100) |
6 (100) |
Eye exudate (6) |
3 (50) |
3 (50) |
2 (33) |
6 (100) |
6 (100) |
Urine (4) |
1 (25) |
0 |
1 (25) |
4 (100) |
4 (100) |
p
|
0.5 |
0.15 |
0.12 |
0.36 |
|
Hospital ward |
|
ICU (13) |
11 (84.6) |
6 (46.1) |
3 (23) |
13 (100) |
12 (92.3) |
Pediatric (10) |
4 (40) |
5 (50) |
3 (30) |
10 (100) |
10 (100) |
Internal medicine (7) |
3 (42.8) |
5 (71.4) |
1 (14.2) |
7 (100) |
6 (86) |
Neurology (5) |
2 (40) |
3 (60) |
2 (40) |
5 (100) |
5 (100) |
Infectious diseases (4) |
2 (50) |
2 (50) |
0 |
4 (100) |
4 (100) |
Women’s surgical (2) |
0 |
1(50) |
1 (50) |
2 (100) |
2 (100) |
p
|
0.04 |
0.075 |
0.074 |
0.11 |
|
Patient age (y) |
|
< 20 (19) |
11 (57.9) |
9 (47.3) |
6 (31.6) |
19 (100) |
18 (95) |
20 – 45 (7) |
4 (57.1) |
6 (85.7) |
1 (14.2) |
7 (100) |
7 (100) |
> 45 (15) |
7 (46.7) |
7 (46.7) |
3 (20) |
15 (100) |
14 (93) |
p
|
0.915 |
0.218 |
0.703 |
0.373 |
|
Patient gender |
|
Female (25) |
13 (52) |
12 (48) |
9 (36) |
25 (100) |
24 (96) |
Male (16) |
9 (56.2) |
10 (62.5) |
1 (6.2) |
16 (100) |
15 (94) |
p
|
0.79 |
0.36 |
0.06 |
0.48 |
|
Total (41) |
22 (53.6) |
22 (53.6) |
10 (24.4) |
41 (100) |
39 (95.1) |
Table 3Performance indices used for the evaluation of biofilm formation using TM, CRA and PCR methods.
Method |
% of statistical parameter |
SN |
SP |
PPV |
NPV |
PLR |
NLR |
TM |
64 |
58 |
64 |
58 |
1.52 |
0.62 |
CRA |
18 |
68 |
40 |
42 |
0.56 |
1.2 |
PCR |
45.5 |
68 |
62.5 |
52 |
1.42 |
0.8 |