MRSA infection is of global concern worldwide. Epidemiologic studies about MRSA rely on the use of standard nomenclature that identifies the prevailing strains at the chromosomal level . SCCmec typing is one of the internationally recognized MRSA typing methods. [12, 13].
Pyogenic skin infection is the most common clinical presentation of MRSA infection. Sixty percent of the isolates in this study were collected from pyogenic skin lesions, followed by bloodstream infection (14%), lower respiratory tract infection (9%), and urinary tract infection (5%). Another study about MRSA in Egyptian hospital laboratories also reported a similar proportion of isolates from pyogenic lesions (64.3%) and bloodstream infection (9.5%) . Similarly, it was reported in Kuwait that the majority of MRSA isolates were from wounds and pus, followed by blood . Also, in the United Arab Emirates, pyogenic lesions and bloodstream infection were the sources of 73.4% and 15.2% of MRSA isolates, respectively .
Seventy-five percent of our isolates were SCCmec typeable by PCR. Several studies worldwide employed SCCmec typing by PCR for identification of the prevailing SCCmec types in their regions and reported varying degrees of typeability that were all less than 100%. For instance, a study in Denmark reported 98% typeability by multiplex PCR . Another study in Portugal reported 97.4% typeability . A more recent study in Palestine reported a typeability of 96.4%. Also in Alexandria, Mansoura, and Cairo, Egypt, the reported typeability was 90%, 94% and 88.8%, respectively. . . . A lower percentage of typeability (77%) was reported by a study in Rwanda , which was close to the findings of the current study.
The high percentage of isolation of SCCmec type V (45.3%) followed by SCCmec type IV (16%) and types II and III (13.3% each) among the 75 typeable MRSA isolates in our study was in accordance with the findings of several studies, worldwide. A recent study in a tertiary hospital in Cairo, Egypt, reported that half of their MRSA isolates were SCCmec type V (50%) followed by SCCmec type VI (17%) . Also, a study carried out in four University Teaching Hospitals in Iran, reported that SCCmec type V was the most prevalent (66.7%) among their clinical MRSA isolates . Moreover, other studies conducted in Armenia , and in Iran  stated that, SCCmec types V and VI were the most identified among MRSA isolated from hospitals.
Consistently, a study in Saudi Arabia reported the detection of SCCmec type IV in 77.3% of their isolates, followed by SCCmec type V (13.2%), and type III (9.4%) . Similarly, a study in Kuwait reported that the majority of their isolates belonged to SCCmec type IV (39.5%) followed by SCCmec type III (34.4%). In Africa, a study assessed the SCCmec types in correlation with spa types and reported that isolates of the common spa types harbored SCCmec types IV followed by type V, with a minority harboring SCCmec type I.
Conversely, a study in Alexandria conducted on 72 MRSA isolates collected over 4 months in 2015, reported that 57% of their MRSA isolates harbored SCCmec type III and only 11% were of SCCmec type V . The discrepancy between their most prevalent SCCmec type (type III) and our results (type V) may be attributed to the fact that the study was conducted 4 years earlier, and it focused mainly on typing of MRSA isolates collected from healthcare-associated infections which represented 80% of their typed isolates. On the other hand, our study intentionally disregarded the source of infection, and typing was performed on randomly selected isolates including nasal colonizers, to allow for a better representation of the SCCmec types prevalent in Alexandria, Egypt.
SCCmec type I was not detected in any of our isolates. Despite being undetected in Egypt and nearby regions, a study on a small scale in Rwanda, reported the detection of SCCmec type I in 56% of the 39 MRSA isolates included in their study. They also reported that SCCmec type IV was the second most common type among their isolates (17.9%), while SCCmec types II and V were undetectable .
Apart from that, a study in Hungary stated that SCCmec type IV accounted for the vast majority of their MRSA isolates (66.7%), followed by SCCmec type II (23.5%), and SCCmec type I (9.2%). They reported that SCCmec type V was detected in only one isolate, while SCCmec types III and VI were not found .
The discrepancy in the distribution of SCCmec types reported from different geographic regions, and even from the same region at different points of time, can be attributed to the high plasticity of this region, and the limited capabilities of the conventional PCR detection method, in addition to the differences in the sensitivity and specificity of the primers used, which may eventually result in missed identification of some SCCmec types.
In the present study, SCCmec type V isolates were the most predominantly isolated (53%) from pyogenic skin lesions, with a statistically significant correlation (p < 0.001). This was in accordance with the findings reported by a study in Mansoura University Hospital which stated that SCCmec type V is significantly associated with burns and abscesses, and of a moderate association with wound sources.
SCCmec IV showed the least resistance to antibiotics, while SCCmec types II and III displayed the highest resistance to antibiotics and were significantly associated with resistance to fluoroquinolones (p < 0.001). The association between SCCmec type III and fluoroquinolones resistance was in accordance with the findings of previous studies in Egypt and Iran [20, 29].
Similarly, in Hungary, it was reported that SCCmec type II is associated with the highest level of resistance to antibiotics while SCCmec type IV is associated with low resistance . Also, a Russian study reported that Isolates carrying SCCmec type III demonstrated higher antibiotic resistance than SCCmec type IV .
The most common resistance patterns among our isolates were; resistance to gentamicin only, and simultaneous resistance to gentamicin, doxycycline, and Tetracycline, each detected in 17% of the isolates. Contrary to our findings, a study conducted in a Hungarian tertiary care hospital reported that the most prevalent phenotype of resistance was to erythromycin, clindamycin, and ciprofloxacin . On the other hand, a study in Kuwait reported that a high proportion of their isolates was resistant to tetracycline, erythromycin, ciprofloxacin, and trimethoprim/sulfamethoxazole .
Our isolates displayed very high resistance to gentamicin (71%), with no statistical difference between different SCCmec types. This was followed by resistance to tetracycline (44%). Resistance to fluoroquinolones and macrolides was less (23–25%), while resistance to trimethoprim/sulfamethoxazole (10%) and Rifampicin (5%) was low. All isolates were susceptible to vancomycin, however, 3 isolates displayed intermediate susceptibility to Linezolid. This could be probably due to the over-prescription of this drug by physicians in Egypt.
In Spain, it was reported that ciprofloxacin resistance was the highest (85%) in MRSA, followed by erythromycin resistance (65%), gentamicin resistance (35%), and tetracycline resistance (30%). All MRSA strains were susceptible to trimethoprim/sulfamethoxazole and rifampicin, which was not far from our susceptibility results for these 2 antibiotics . Also, a study in Palestine reported that resistance to erythromycin in MRSA was 63.4%, and to ciprofloxacin was 39.3%, with 18.8% resistance to trimethoprim/sulfamethoxazole .
Constitutive clindamycin resistance was displayed by 8% of our isolates, while 4% showed inducible resistance with a positive D-test. The percentage of clindamycin resistance was slightly higher in a study conducted in Spain which reported that 11.7% of their MRSA isolates have inducible clindamycin resistance . Even higher percentages were reported in Kuwait, where the authors reported that inducible and constitutive clindamycin resistance among their MRSA isolates were 14.4% and 37.8%, respectively .