Association of Streptococcus with Plaque Type of Psoriasis

Background: Guttate psoriasis has a well-known association with streptococcal throat infections, but the effects of these infections in patients with chronic plaque type of psoriasis remains to be evaluated. In Bangladesh several studies were done on psoriasis but no data about association between streptococcal throat infection and plaque type psoriasis are available so far. Considering the co-morbidities of psoriasis patients, it might be justifiable to find out the events that provoke the initiation or exacerbation of psoriatic disease process. Objective: To observe the association of streptococcus with plaque type of psoriasis. Materials and Methods: This observational study was conducted in the department of Dermatology and Venereology, Bangabandhu Sheikh Mujib Medical University, Dhaka. Forty seven patients clinically and histopathologically diagnosed as having plaque psoriasis were selected as cases and patients with skin diseases other than psoriasis were selected as controls. Results: In this study majority of subjects (55%) were diagnosed as chronic plaque psoriasis. Among the subjects with guttate flare of chronic plaque psoriasis 64.2% gave a positive history of sore throat. ASO titer was raised (>200 IU/mL) in 28 (59.5%) patients of chronic plaque psoriasis and 7 (17.9%) patients of non-psoriatic respondents. The difference between two groups was significant (p<0.05). Streptococcus pyogenes was found in 12 (25.5%) in chronic plaque psoriasis patients versus in 4 (10.2%) in controls (p>0.05). Conclusion: This study shows that streptococcal throat infections are associated with plaque psoriasis and early treatment of throat infections may be beneficial for plaque type of psoriasis patients.


Association of Streptococcus with Plaque Type of Psoriasis
streptococcal antigens have also been detected in the skin lesions of both guttate psoriasis (GP) and chronic plaque psoriasis (CPP), a subset of which recognize streptococcal cell wall antigens. 8It is possible that streptococci contain antigenic substances recognized by psoriatic T cells. 9Swerlick et al 10 have demonstrated cross-reactivity between epidermal keratins and streptococci.There is a strong association between prior infection with streptococcus pyogenes (b-hemolytic streptococcus) and psoriasis which was proved by a history of an acute sore throat 1 to 3 weeks before the eruption and bacteriological (culture of throat swabs) and serological (ASO titer) evidence of recent streptococcal infection. 11,12Currently there is no cure for psoriasis and treatment options produce variable responses, partly, because disease pathogenesis is not completely understood. 13

Materials and Methods
This cross sectional study was carried out in the department of Dermatology & Venereology, Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka from February to October 2012.Patients of both sexes and all ages with plaque type of psoriasis, diagnosed clinically and histopathologicaly, attending in department of Dermatology & Venereology, BSMMU, Dhaka were selected as cases and age matched nonpsoriatic indoor and outdoor patients were included as controls.Consecutive type of nonprobability sampling technique was followed in this study.Controls were non-psoriasis patients (age matched within ±5 years with case) attending in inpatient and outpatient department of Dermatology & Venereology, BSMMU.Patients on systemic anti-psoriatic drugs and/or systemic antibiotics currently and minimum within previous 15 days from interviewing were excluded.Informed written consent was taken from all the study subjects.

Study procedure
Patients with skin lesions suggestive of psoriasis attending in inpatient and outpatient department of Dermatology and Venereology, BSMMU were interviewed.Then these possible cases were examined clinically and advised for skin biopsy for histopathology and microbiological examination of throat swabs (culture and sensitivity) and serological test for antistreptococcal antibody (anti-streptolysin O [ASO] titer).Particulars of the subjects and history were recorded in a structured data sheet.After confirming psoriasis clinically and histopathologicaly and receiving both throat swab culture and ASO titer reports, possible cases were considered finally as confirmed cases.Clinically diagnosed psoriasis cases, but not confirmed histopathologically were excluded from the study.Thus total 47 plaque psoriasis patients of all ages and both sexes were recruited as cases finally.Recruited plaque psoriasis patients were allocated to one of three groups: 1) Guttate flare of chronic psoriasis (n=14); 2) Chronic plaque psoriasis (including scalp psoriasis) (n=26); 3) Sudden exacerbation/deterioration of chronic plaque psoriasis (n=7).
Throat swab specimens were collected with sterile cotton swab (15 cm long) and venous blood was drawn with sterile syringe.Both the specimens were put into separate sterile test tubes for sending to the laboratories of Microbiology and Immunology departments of BSMMU as early as possible.Collected throat swabs were inoculated on blood agar media and incubated at 37 0 C for 48 hours.The pathogenic organism was identified by gross colony morphology and types of hemolysis (clear zone of hemolysis around the colonybeta hemolysis or turbid halo with greenish zone around colony -alpha hemolysis) on culture media.b-hemolysis indicated growth of streptococcus pyogenes.ASO titers were measured with BN ProSpec, SIEMENS, USA.ASO titer >200 IU/mL or greater (upper limit of normal value, 200 IU/mL) was considered as evidence of recent streptococcal infections.Data were collected from preformed data sheets and bacteriological and serological reports.Statistical analysis was done by using SPSS (version 16.0).Statistical significance was set at 5% level and confidence interval at 95% level.

Results
In this study mean age was 38 ± 4.7 years in cases and 29 ± 5.4 years in controls.There was no significant difference in age between two groups.ASO titer status in cases and controls is shown in Table II.ASO titer was raised (>200 IU/mL) in 28 (59.57%)patients and 7 (17.90%)nonpsoriatic controls.The difference between two groups was significant (p<0.05).
Table II Table IV shows comparison of throat swab culture reports between cases and controls.Table V shows the throat swab culture results in different types of psoriasis.In total streptococcus pyogenes was isolated from 12 (25.50%)plaque psoriasis patients and 4 (10.25%)controls.There was no significant difference in culture results of two groups (p>0.05).

Discussion
Among the 47 cases in this study 26 (55%) subjects were of chronic plaque psoriasis, 14 (30%) patients were with guttate flare of chronic plaque psoriasis and 7 (15%) patients were with deterioration of chronic plaque psoriasis.Similar study was conducted by Telfar et al with 111 patients with psoriasis, where they found 60% cases as chronic plaque psoriasis. 12is study shows that 64.2% patients of guttate flare of chronic plaque psoriasis gave a positive history of sore throat and their history of sore throat was within 1 to 4 weeks period prior to the appearance of skin lesions.ASO titer was raised in 59.6% of plaque psoriasis patients and it was 17.9% in controls.Difference of ASO titer status in chronic plaque psoriasis was significant in comparison with respective controls (p value <0.05).Serologic evidence of recent streptococcal infections (raised ASO titer) was found in 18 (56%) of 32 patients with 31% having a history of sore throat 1 to 3 weeks before the appearance of rash and 17 (85%) of 20 patients with AGP (acute guttate psoriasis) in studies reported by Mukherjee et al. 14 In a cross sectional study with 111 patients, ASO titer was raised in 43% cases in total, 58% in AGP and 26% in guttate exacerbation of chronic plaque psoriasis. 12In a prospective study, Gudjohnson et al described ASO titer status raised 10 times than their controls in chronic plaque psoriasis. 4All these studies showed significant differences (p value < 0.05) with their respective controls.The outcomes of above mentioned studies were similar to our findings.
In this study, Streptococcus pyogenes was isolated from 12 (25.5%)plaque type of psoriasis patients and 4 (10.26%)controls.There was no significant difference in culture result of two groups (p>0.05).Confirmation of streptococcal infections in psoriasis might be difficult because patients were mostly seen in the convalescent phase when antibiotics had already been taken and throat swab cultures were more likely to be negative.Streptococcus pyogenes was isolated from 26% in AGP, 13% in guttate flare of chronic plaque psoriasis, 14% in chronic plaque psoriasis and 6% in total controls in a study on 111 psoriasis patients by Telfar et al. 12 In another study Naqqash et al isolated streptococcus pyogenes in 34% cases in chronic plaque psoriasis and 97% in AGP. 6Gudjohnson et al showed Streptococcus pyogenes positive in throat swab culture in 9.1% in chronic plaque psoriasis versus 0.9% in controls (p<0.05). 4Keeping these studies in mind and the possible association documented in our study, between Streptococcus pyogenes and plaque psoriasis, in terms of evidence of recent throat infections (raised ASO titer and positive throat swab culture), it is important to search for and eliminate microbial infections in the treatment of plaque type of psoriasis.
From this study it can be concluded that streptococcal throat infections can provocate plaque psoriasis.However, more studies are needed with greater numbers of patients to determine risk associations of psoriasis with S. pyogenes.

Limitation
Limitation of this study was difficulty in confirmation of streptococcal infections in psoriasis because patients are often seen in the convalescent phase when antibiotics have already been taken and throat swab cultures are more likely to be negative.

Fig 1 .Fig 2 .
Fig 1. Types of plaque psoriasis in cases Fig 2 shows the distribution of guttate flare of chronic plaque psoriasis patients according to their history of sore throat within 1 to 4 weeks period prior to the appearance of skin lesions.It shows that 64.2% of guttate flare of chronic plaque psoriasis patients gave a positive history of sore throat.Other types of psoriatic patients did not give history of sore throat.

Table I :
Table I shows distribution of subjects according to age.Distribution of subjects according to age p value obtained from t test; ns=Nonsignificant Fig 1 shows the distribution of different types of plaque psoriasis in cases.Majority (55%) were diagnosed as chronic plaque psoriasis.

Table IV :
Comparison of throat swab culture reports between cases and controls p value obtained from c 2 test (df=2, c 2 value = 3.59) *p value is >0.05;Not significantTypes of plaque psoriasisHistory of sore throat in guttate flare of chronic plaque psoriasis cases

Table V :
Results of throat swab culture in different types of psoriasis (n=47)