Clinical and bacteriological aspects of pyoderma.
In India, bacterial infections of skin constitute a large proportion of skin diseases. Saxena et al reported pyodermas in 17% of total out-patients while Mehta observed it in 25% of patients.
Cutaneous bacterial infection is divided into primary and secondary type. Primary infections have a characteristic morphology and course, caused by a single organism, and arise in normal skin. Primary infections are most frequently incited by coagulase positive Staphylococci or beta-haemolytic streptococci. They are also the most common invaders in secondary infection.
Institution of appropriate treatment in these common dermatoses is a must. Antibiotic sensitivity pattern differs from region to region, and even within the same region, with progress of time. Ramani et al from Visakhapatnam found that Coagulase positive Staphylococci showed high resistance to penicillin, while Vijayalakshmi et al reported penicillin to be very effective. This prompted us to undertake a study of the bacteriological flora of the common pyodermas in Bombay.
One hundred newly diagnosed and untreated cases were selected for the study. They were examined in detail and classified into different types of pyodermas.
Collection of specimen
The lesions were swabbed with alcohol and the pus was collected by using a sterile cotton swab. In the cases with intact pustular lesions, the pustule was ruptured with a sterile needle and material was taken with sterile swab. In crusted lesions, the crusts were partly lifted and material was taken from underneath.
Smears made from the pus were stained with Gram's stain and examined. Pus was cultured on blood agar and Mackonkey's medium and incubated aerobically at 37°c, for 24 hours and 48 hours. Organisms grown were identified on the basis of their morphology, cultural characters and biochemical reactions according to standard methods.
Sensitivity of the organisms to antibiotics was tested on nutrient agar. Antibiotic sensitivity was tested by disc diffusion technique using Bio-disc (Hi-Madia)R.
Disc concentration was as follows:
Penicillin-G 10 Units
Ampicillin 10 mcg
Tetracycline 30 mcg
Erythromycin 15 mcg
Chloramphenicol 30 mcg
Streptomycin 10 mcg
Gentamycin 10 mcg
Kanamycin 30 mcg
Total of one hundred patients were studied. Their age group is as shown in the [Table 1]. The types of bacterial infection are depected in [Table 2].
Primary bacterial infection was seen in 61 patients while 39 cases had secondary bacterial infection, the primary skin disease in the 39 cases being eczema (15), scabies (14), miliaria rubra (8) and pediculosis (2).
Only one case had concomitant impetigo along with furuncle.
Gram's stain showed Gram positive cocci in short chains and in groups along with PMN. (Culture showed growth of S. aureus in all cases. All the isolated strains of S. aureus except three showed a positive coagulase test. Antibiotic sensitivity pattern of S. aureus strains isolated is shown in [Table 3].
Bacterial infections were more common in the younger age group [Table 1]. Ramani et al found 78% of cases below the age of 10 years and 15% in the 11 to 20 years age group. Our youngest patient was 2½ months old child.
In the present study, male to female ratio was 4:1. Jalan et al also found male preponderence, while Ramani et al reported no significant difference.
Primary bacterial infection was seen in 61% of cases. Scabies was the commonest cause of secondary bacterial infection. Khandari et al found 16% of their cases were of secondary bacterial infection, all due to eczema, while 13% of patients studied by Ramani et al were of secondary type, of which the commonest was intertrigo.
Superficial folliculitis was the commonest presentation, (39%), out of which 31 cases were of chronic recurrent superficial folliculitis, similar to that reported by Saxena et al. However, Ramani et al observed impetigo as the commonest manifestation.
We isolated, coagulase positive S. aureus from 97% of the patients, while Jalan et al found it in 88% of cases studied by them. Khandari et al isolated S. aureus from 68% of the cases, and 39% of cases studied by them showed ß-haemolytic strepticocci. Ramani et al detected ß-haemolytic Streptococci as pathogenic agent in 25% of cases and S. aureus in 88%. In the present study three strains of S. aureus were coagulase negative. Ramani et al had observed that 11% of strains of S. aureus isolated from the sites of pyoderma were coagulase negative.
In this study, all the strains of staphylococci showed highest sensitivity to erythromycin (97%) followed by gentamycin (92%), chloramphenicol (83%) and kanamycin (82%). Jain et al observed highest sensitivity with gentamycin (98.3%).
We observed the highest resistance to streptomycin (60%) followed by penicilin (49%). Ramani et al observed maximum resistance to penicillin (61%) followed by streptomycin (51%) Vijayalakshami et al also observed maximum resistance of coagulase positive staphylococci to penicillin.
Thirty-four out of forty-nine cases that showed penicillin resistance had chronic and recurrent folliculitis or furunculosis. [Table 3]. Desai et al reported 30 cases with pyogenic folliculitis on leg resistant to penicillin therapy.
All penicillin resistant strains showed sensitivity to Erythromycin except 3, who showed sensitivity to tetracycline. Patient were treated according to antibiotic sensitivity report. Patients with chronic and recurrent pyodermas from whom S. aureus strains showed resistance to penicillin in vitro, were treated with either erythromycin or tetracyclin with good results. From the above made observations, we conclude that penicillin is still the drug of choice in acute bacterial infection. However, in chronic and recurrent infection, culture and sensitivity whenever possible should be done and patient treated accordingly.
Authors are thankful to the Research Society of K.E.M. Hospital for providing financial grant to carry out this project.