The Prevalence of S. aureus Skin and Soft Tissue Infections in Patients with Pemphigus

Pemphigus vulgaris are autoimmune blistering diseases that may result in significant morbidity and death. Immunosuppressive therapy of pemphigus vulgaris would predispose the patients to infections. The aim of this study was to assess the prevalence of S. aureus infection and PVL gene in patients with pemphigus admitted to dermatology clinic. Materials and Methods. This descriptive study was conducted on 196 pemphigus vulgaris patients (119 males, 77 females) admitted to dermatology clinic between 2014 and 2015. In this study, the diagnosis of pemphigus vulgaris was made by histology, immunofluorescence pattern of perilesional skin, and indirect immunofluorescence testing of serum. Data were collected through a questionnaire. Results. 59.1% of pemphigus vulgaris patients had S. aureus infection. 49 out of 116 were methicillin-resistant. PVL gene was detected in 25 out of 116 S. aureus positive patients. Conclusion. This is the first report of S. aureus infection in pemphigus patients in Iran. More than forty percent of isolates were methicillin-resistant S. aureus. PVL gene carried by methicillin-resistant S. aureus was high in this study.


Introduction
Pemphigus is defined as a group of life-threatening blistering disorders which results in the formation of intraepithelial blisters in mucous membranes and skin [1][2][3]. The four major types of pemphigus are pemphigus vulgaris, pemphigus foliaceus, IgA pemphigus, and paraneoplastic pemphigus. Incidence rates between 0.1 and 0.5 per 100,000 people per year have been described; however, higher rates have been reported in certain populations [4]. Inhabitants of India, Southeast Europe, and the Middle East have the greatest risk for pemphigus vulgaris. Pemphigus occurs in men and women with equal frequency. In most geographic locations, pemphigus vulgaris is more common than pemphigus foliaceus. However, in certain locations, such as North Africa, Turkey, and South America, the prevalence of pemphigus foliaceus goes over pemphigus vulgaris [5]. Pemphigus vulgaris and pemphigus foliaceus are potentially life-threatening disorders. First-line treatment for these diseases consists of a systemic glucocorticoid with or without an adjuvant immunosuppressant. Local skin care measures may reduce the risk for infection. The possibility of secondary infection should be considered when lesions fail to respond to therapy, and infection should be treated appropriately if it is detected [6][7][8]. Bacterial infection was not reported as an inducing factor of pemphigus, while septicemia of Staphylococcus aureus dose occurs, as a complication of immunosuppressive therapy. There are a number of possible clarifications for the association of pemphigus with bacterial infection [9,10]. The bacteria could simply be an opportunistic infection, because pemphigus patients are treated with immunosuppressive therapy for a long time. Early recognition of concurrent pemphigus and bacterial infection, especially S. aureus, is extremely important because of the possible fatal consequences of the disease. The aim of this study was to assess 2 Autoimmune Diseases the prevalence of S. aureus infection and PVL gene in patients with pemphigus.

Study Population and Strain Collection.
This cross-sectional study was performed on 338 patients with skin and soft tissue infection who were admitted to Tehran dermatology service of Razi Hospital affiliated to the Tehran University of Medical Sciences. Patients with a clinical diagnosis of pemphigus with compatible histopathology and direct immune fluorescence (DIF) findings confirming the clinical diagnosis of pemphigus entered the study. The diagnosis of pemphigus vulgaris was made by histology, immunofluorescence pattern of perilesional skin, and indirect immunofluorescence testing of serum. A questionnaire was completed to collect the patient's data. Clinical Staphylococcus aureus samples which were collected from pemphigus patients with skin and soft tissue infection who were admitted to Tehran dermatology service of Razi Hospital affiliated to the Tehran University of Medical Sciences were taken to the microbiology lab of Kashan Medical Faculty to approve the diagnosis of S. aureus. Samples from the skin and soft tissue infection were collected from all patients and were cultured on sheep blood agar and mannitol salt agar incubated for 24-48 h at 37 ∘ C. The isolates confirmed to the species level by gram staining, catalase activity, DNase, slide coagulase, and free coagulation of citrated rabbit plasma in tube.

S. aureus Identification.
All swabs were inoculated onto mannitol salt agar, incubated at 37 ∘ C. Any suspected colony was subcultured on tryptic soy agar and the isolates were confirmed as being S. aureus by colonial morphology, Gram staining, catalase activity, DNase tests, slide coagulase test, and free coagulation of citrated rabbit plasma in tube [11,12].

Determination of Methicillin Resistance.
Methicillin resistance was evaluated using two methods. The first method was disk diffusion method using Mueller Hinton agar according to the recommendations of Clinical and Laboratory Standards Institute (CLSI), 30 g cefoxitin disk (≤21 mm indicated MRSA), and 1 g oxacillin disk (≤10 mm indicated MRSA). The second method was polymerase chain reaction (PCR) for the detection of mecA gene (positive indicated MRSA) [13,14].

Antimicrobial Susceptibility Testing and Determination of MDR.
Antimicrobial susceptibility and resistance were determined by disk diffusion method using Mueller Hinton agar according to the recommendations of Clinical and Laboratory Standards Institute (CLSI) [13]. The following disks were used: oxacillin (1 g), penicillin (1 g), teicoplanin (30 g), tetracycline (30 g), azithromycin (15 g), clindamycin (2 g), cefoxitin (30 g), ciprofloxacin (30 g), gentamicin (10 g), linezolid (30 g), daptomycin (30 g), amikacin (30 g), and cefazolin (30 g). The reference strain S. aureus ATCC 3359 was used as a control. Results were interpreted as susceptible, intermediate, or resistant according to the criteria recommended by the CLSI and the manufacturer protocols (Mast Group Ltd., Merseyside, UK). Defining of MDR in S. aureus isolates was done according to new standardized international document. The isolates were classified as multidrug resistant (MDR) if they were resistant to more than three classes of antimicrobial drugs [15].
2.5. Preparation of Genomic DNA. DNA was prepared by boiling. It was stored at −20 ∘ C. Aliquots of 2 L of template DNA were used for PCR.

Detection of PVL Gene.
The presence of the lukS-PV and lukF-PV genes encoding components of PVL was determined by a polymerase chain reaction-(PCR-) based method with the primer pair described in Lina et al. 2 Primers used in this study were as follows: 5 ATCATTAGGTAAAATGTC-TGGACATGATCCA 3 as forward and 5 GCATCAAST-GTATTGGATAGCAAAAGC 3 as reverse [16]. In this study Staphylococcus aureus strain, ATCC 49775, was used as positive control and distilled water was used as a negative control. DNA amplification was performed on an Eppendorf cycler in a final volume of 20 L reaction containing 1.5 mM of MgCl 2 , 250 M dNTPmix, 1 M of each primer (20 NM), 1 U of Taq DNA polymerase, 10 mM Tris-HCL (PH 9.0), 30 mM KCL, and 4 M of template DNA. Amplification was carried out with first denaturation at 94 ∘ C for 5 min (first denaturation) followed by 36 cycles according to the following program: denaturation at 94 ∘ C for 45 sec, annealing at 61.3 ∘ C for 45 sec, and extension at 72 ∘ C for 45 sec, plus a final extension at 72 ∘ C for 5 min to complete partial polymerization. The PCR products were resolved by electrophoresis through a 1.5% agarose gel containing ethidium bromide (Bio-Rad, UK). The PCR purification kit (Bioneer Co., Korea) was used to purify PCR products and sequencing of forward strand was performed by the Bioneer Company (Korea). The nucleotide sequences were analyzed with Chromas 1.45 software and MEGA-4 software and BLAST in NCBI.    (Figure 2). Of these PVL positive S. aureus isolates, 14 (56%) were MRSA and 11 (44%) were MSSA ( Table 2). 93.9% of the isolates were penicillin resistant; all of the strains showed sensitivity to linezolid and 99.1% of the isolates were daptomycin susceptible. All isolates were sensitive to vancomycin (Figure 3).

Discussion
Pemphigus is a well-known autoimmune disease [17]. Nowadays, the relationship between autoimmunity, immunodeficiency, and infection is well recognized. It is believed that autoimmunity and immunodeficiency are not separate entities; rather some connection exists between them [18,19]. On the other hand, hospitalization in addition to immunosuppressive therapy would predispose the PV patients to infection. In some studies bacterial infections have been reported [20,21]. Most bacterial skin infections detected in our patients were due to Staphylococcus aureus. In other studies in PV patients, skin infections due to Staphylococcus aureus have been reported as well [22]. Kanwar and Dhar reported that sepsis was the most common cause of causes of deaths in PV patients, and S. aureus was the responsible  [26]. In summary, more than fifty percent of the pemphigus patients in this study were colonized by MRSA. 3 out of 32 nosocomial MRSA cases were PVL gene positive. Pemphigus was significantly associated with MRSA colonization. The significant difference was seen between S. aureus SSTI in pemphigus patients with male gender, MDR, previous antibiotic usage, especially vancomycin and aminoglycosides, corticosteroids usage, and nosocomial infection.

Conclusion
This is the first report of S. aureus infection in pemphigus patients in Iran. Autoimmune process and immunosuppressive therapy of pemphigus would predispose the patients to infections. S. aureus infection in patients with pemphigus was high compared to other bacteria. PVL gene carried by methicillin-resistant S. aureus was high in this study.