This study was performed on 146 clinical samples [Female = 82 (56.2%); Male = 64 (43.8%)] collected from teaching hospitals in Isfahan (Imam Musa Kazem, Amin and Al-Zahra Hospitals) and Kashan (Shahid Beheshti Hospital). Clinical samples were collected of burn wound 56 (38.4%), eye infection 49 (33.6%), respiratory infections 11 (7.5%), trauma 6 (4.1%), diabetic wound 5 (3.4%), brain abscess 5 (3.4%), blood 3(2%), urine 9(6.2), and other infections 2 (1.4%). There was no significant difference between MRSA and MSSA isolates in terms of age groups, gender and clinical specimens (P > 0.05), although a significant correlation was seen between the methicillin resistance and teaching hospitals from which clinical samples has been obtained (P = 0.001).
The results of PCR amplification of mecA gene showed among 146 studied S. aureus isolates 24 (16.4%) isolates identified as MRSA strains.
According to results obtained from antibiotic susceptibility testing, resistance rates to tetracycline 19 (79.2%), erythromycin 17 (70.8%), ciprofloxacin 16 (66.7%), and gentamicin 15 (62.5%) was high among MRSA strains and all S. aureus isolates were sensitive to vancomycin (MIC < 2 μg/mL) (Table 2). The MRSA strains were significantly more resistant to the antibiotics studied in comparison to MSSA strains (P < 0.05), and there was a significant correlation between multiple-drug resistance and MRSA isolation (P = 0.001).
Table 2 Antimicrobial resistance among MRSA and MSSA strains
Antibiotic (%)
|
MRSA (%)
N = 24
|
MSSA (%)
N = 122
|
Total (%)
N = 146
|
Tetracycline
|
19 (79.2)
|
31(25.4)
|
50 (34.2)
|
Erythromycin
|
17 (70.8)
|
28 (22.9)
|
45 (30.8)
|
Ciprofloxacin
|
16 (66.7)
|
17 (13.9)
|
33 (22.6)
|
Gentamicin
|
15 (62.5)
|
9 (7.3)
|
24 (16.4)
|
Clindamycin
|
14 (58.3)
|
8 (6.6)
|
22 (15.1)
|
Cefazolin
|
13 (54.2)
|
1 (1)
|
14 (9.6)
|
Linezolid
|
1 (4.2)
|
2 (1.6)
|
3 (2.1)
|
Trimethoprim Sulfamethoxazole
|
8 (33.3)
|
6 (4.9)
|
14 (9.6)
|
SCCmec typing
Three different SCCmec types were obtained among MRSA strains including 16 (66.7%) SCCmec type V, 3 (12.5%) SCCmec type III and, 5 (20.8%) SCCmec type II (Table 3).
Table 3 Characteristics of the MRSA isolates from clinical samples in different hospitals (N = 24)
Source
|
Hospital
|
Ward
|
Antibiotic resistance pattern
|
MSCRAMMs
|
SCCmec type
|
Clonal Complex
|
STd
|
Blood
|
SBa
|
Emergency
|
T*, E, CIP, GEN, CD, CZ, TS, FOX
|
eno, cna, fib, fnbB
|
II
|
8
|
239
|
Burn wound
|
IMKb
|
Skin
|
T, E, CIP, GEN, CD, CZ, TS, FOX
|
eno, cna, fib, fnbB
|
III
|
8
|
861
|
|
IMK
|
Skin
|
T, E, CIP, GEN, CD, CZ, FOX
|
eno, cna, fib
|
III
|
7
|
239
|
|
IMK
|
Skin
|
E, CIP, GEN, CZ, FOX
|
eno
|
V
|
8
|
8
|
|
IMK
|
Skin
|
T, CIP, LZD, FOX
|
eno, ebp, fib, fnbB
|
V
|
398
|
291
|
|
IMK
|
Skin
|
T, E, CIP, GEN, CD, TS, FOX
|
eno, fib
|
V
|
59
|
59
|
|
IMK
|
Skin
|
FOX
|
eno, cna
|
V
|
59
|
59
|
|
IMK
|
Skin
|
T, FOX
|
_
|
II
|
398
|
291
|
|
IMK
|
Skin
|
T, FOX
|
_
|
II
|
22
|
22
|
|
IMK
|
Skin
|
T, E, CIP, GEN, CD, CZ, FOX
|
eno, cna, ebp, fib
|
II
|
8
|
239
|
|
IMK
|
Skin
|
T, CZ, TS, FOX
|
eno
|
V
|
8
|
1465
|
|
IMK
|
Skin
|
T, TS, FOX
|
eno
|
V
|
22
|
22
|
|
IMK
|
Skin
|
E, FOX
|
eno ,cna, ebp, fib
|
V
|
1
|
772
|
|
IMK
|
Skin
|
T, E, CIP, GEN, CD, CZ, TS, FOX
|
eno
|
V
|
22
|
22
|
|
IMK
|
Skin
|
E, FOX
|
eno, ebp, fib
|
V
|
5
|
6
|
|
IMK
|
Skin
|
T, E, CIP, GEN, CD, CZ, TS, FOX
|
eno, fib
|
V
|
8
|
1465
|
Eye infection
|
SB
|
Emergency
|
T, E, CIP, GEN, CD, TS, FOX
|
eno
|
II
|
8
|
889
|
|
Amin
|
Emergency
|
T, E, CIP, GEN, CD, CZ, FOX
|
fib
|
III
|
8
|
239
|
|
Amin
|
Emergency
|
T, E, CIP, GEN, CD, CZ, FOX
|
_
|
V
|
8
|
1465
|
|
Amin
|
Emergency
|
T, E, CIP, GEN, CD, CZ, FOX
|
fib
|
V
|
59
|
59
|
|
Amin
|
Emergency
|
T, CIP, GEN, CD, CZ, FOX
|
_
|
V
|
22
|
22
|
|
SB
|
Emergency
|
T, E, CIP, GEN, CD, CZ, FOX
|
eno
|
V
|
398
|
291
|
Brain abscess
|
AZc
|
ICU
|
T, E, CIP, GEN, CD, FOX
|
eno, ebp, fib, fnbB
|
V
|
8
|
343
|
Respiratory infection
|
AZ
|
ICU
|
E, FOX
|
fib
|
V
|
22
|
22
|
aImam Musa Kazem hospital; bShahid Beheshti; cAl Zahra; dSequence type
*CIP, ciprofloxacin; CD, clindamycin; CZ, cefazolin; E, erythromycin; FOX, cefoxitin; GEN, gentamicin; LZD, linezolid; T, tetracycline; TS, trimethoprim sulfamethoxazole.
Identification of MSCRAMMs genes
Of 24 MRSA isolates, 20 (83.3%) carried MSCRAMMs genes and in 4 (16.6%) of which, none of the MSCRAMMs genes studied were isolated. The prevalence of eno, fib, cna, fnbB, ebps, genes in MRSA isolates were 17 (70.8%), 13 (54.1%), 6 (25.0%), 4 (16.6%) and 5 (20.8%), respectively. Six, 2, and 4 isolates carried 4, 3 and 2 bands related to MSCRAMMs determinants respectively and the fnbA, bbp and clfA genes were not detected in any MRSA isolate (Table 3).
In statistical analyses a significant correlation was obtained between MRSA strains and eno, cna and fib genes, (P < 0.001). In statistical analyses a significant correlation was obtained between MRSA and MSSA strains regarding eno, cna and fib genes (P < 0.001).
Multilocus sequence typing (MLST)
MLST analysis revealed 11 sequence types among MRSA isolates. The results of the MLST were as follows: ST239-SCCmec type III (2 isolates), ST239-SCCmec type II (2 isolates), ST291-SCCmec type V (2 isolates), ST291-SCCmec type II (1 isolates), ST22-SCCmec type II (1 isolate), ST22-SCCmec type V (4 isolates), ST861-SCCmec type III (1 isolate), ST 889-SCCmec type II (1 isolate), ST8-SCCmec type V (1 isolate), ST59-SCCmec type V (3 isolates), ST343-SCCmec type V (1 isolate), ST772-SCCmec type V (1 isolate), ST6-SCCmec type V (1 isolate) and ST1465-SCCmec type V (3 isolates). Also seven MLST- based clonal complexes (CCs) were identified among MRSA strains including: CC8 (41.7%), CC7 (4.2%), CC398 (12.5%), CC59 (12.5%), CC22 (20.7%), CC1 (4.2%) and CC5 (4.2%) (Table 3).