EVALUATION OF SOME COMMERCIAL ANTIMICROBIAL OINTMENTS ON SELECTED BACTERIAL AND FUNGAL STRAINS OF CLINICAL IMPORTANCE

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O.L. Okunye¹, P.A. Idowu² and O.S. Makinde²

1. Department of Pharmaceutical Microbiology, Olabisi Onabanjo University, Ogun State, Nigeria.
2. Department of Pharmaceutical Microbiology, University of Ibadan, Nigeria.

Abstract

Background: Antimicrobial ointments are topical products used for the treatment of common skin infections. Potency superiority between certain ointments and creams used in the treatment of skin infections has been a controversial subject among clinicians.

Objective: This study was carried out to investigate the activities of some antimicrobial ointments on selected bacteria and fungi of clinical importance that caused skin infections.

Methods: Three brands of antibacterial; gentamicin, chloramphenicol, bactroban and two brands of antifungal ointments; nystatin and Whitefield’s were evaluated by agar – cup diffusion method for their antimicrobial activity. Minimum inhibitory concentration, minimum bactericidal concentration and minimum fungicidal concentration of the ointments were determined. Kinetic study of bactroban on all the clinical isolates was evaluated to determine their efficacy within a specific time lag.

Results: All the isolates ofPseudomonas aeruginosa were susceptible to bactroban while 4 of the 5 isolates ofStreptococcus pyogenes were resistant. Three of the five isolates of Staphylococcus aureus were susceptible to bactroban. Gentamicin had no activity on Pseudomonas aeruginosa while 4 of the 5 isolates of Streptococcus pyogenes were susceptible to gentamicin. Three of the 5 isolates ofStaphylococcus aureus were susceptible to gentamicin and varied resistance were recorded for chloramphenicol and antifungal agents. The MIC’’s values recorded for the antimicrobial ointments examined varied with respect to concentrations and composition. Bactroban and gentamicin gave the MIC’s 20g/mL – 2000g/mL and 50g/mL – 400g/mL while the MIC’s range 160g/ mL – 400g/mL, 100g/mL -160g/mL and 180g/mL 200g/mL were also recoded for chloramphenicol, nystatin and Whitefield’s against the isolates concerned respectively. The MBC’s and MFC’s values recorded against the isolates doubled the values obtained from the MIC’s. Kinetic studies showed various population reduction to zero at varied contact time for clinical isolates of bacterial and fungi exposed to bactroban.

Conclusion: These findings elicited potency differences among the ointments tested on the selected clinical microbial isolates examined, this could be useful in the selection of antimicrobial ointments for the management of skin infections caused by the microorganisms tested and their closely related strains.

Keywords: Antimicrobial ointments, Skin infection, Microbial agents.

Introduction

The skin is a relatively inhospitable environment for the growth of most pathogenic microorganisms. The hostility of the skin environment is attributed to relative dryness of cutaneous surfaces that provides insufficient amount of moisture that could support significant growth of pathogens and colonization with resident microflora that produces metabolites that are inhibitory to the growth of invading/competing pathogens¹. Eradication of resident flora greatly enhances the survival of Staphylococcus aureus and the subsequent development of infection.

Skin infections may be either primary or secondary. Primary infections have characteristic morphologies and courses, and are initiated by single organisms, and usually occur in normal skin. They are most frequently caused by Staphylococcus aureus, Streptococcus pyogenes, and coryneform bacteria. Impetigo, folliculitis, boils, and erythrismal are common examples. Secondary infections originate in diseased skin as a superimposed condition, when the skin is damaged by inflammation, burn or exfoliation, absorption is further increased².

Pseudomonas aeruginosa is an opportunistic pathogen that can cause skin infection especially in burns and wounds, sores and ulcers often as secondary invaders. Skin lesions have been reported to accompany Pseudomonas aeruginosa sepsis in 13-39 percent of patients studied over the years³. The dermatological manifestations of Pseudomonas aeruginosa include erythema gangrenosum which was however reported in 25% of patients with bacteraemia. Staphylococcus aureus is responsible for variety of infection syndromes that may produce local or diffuse skin lessions by producing toxins (Staphylococcal scalded skin syndrome and toxic shock syndrome due to vascular invasion often in association with carditis⁴. Other spectrum skin mediated infections that Staphylococcus aureus can cause include; impetigo, folliculitis, furuncles, and ecthyma. Fungi and yeasts are capable of causing many different forms of skin infections broadly referred to as dermatomycoses. Dermatomycoses are a group of common infections generally caused by Trichophyton species. These infections include tinea capitis, tinea barbae, tinea corporis, tinea pedis and tinea cruris ^5,6.

Candida albicans that causes vaginitis is manifested by vaginal itching and discharge, often accompanied by dysuria and pain. Pelvic examination may reveal a creamy to cheesy whitish discharge, redness of the vagina wall and external genitalia may also be present⁷ Antibiotic ointments are topical preparation that are used for the treatment of common skin infections. They contain a medicament dissolved, suspended or emulsified in a base and in their pharmaceutical dosage forms, they are anti-infective and protective on host skin⁸. Antimicrobial ointments are used topically for several purposes; as protectants, antiseptics, emollients, antipruritis, keratolytics and astringents. The use of ointments can be an effective part of wound care, along with regularly cleansing the wound in ensuring speedy healing. Ointments are made up of bases which may be hydrocarbon (oleaginous), absorption, water removable and water soluble type⁹. In general, ointments are intended to speed healing and prevent infection.

Some people also choose to use antibiotic ointment on a new tattoo, though some tattoo artists advise against this for various reasons. Antimicrobial ointments are designed to wipe off bacterial, fungal and yeast skin infection depending on their formulations. The entry of these ointments and creams into the skin is determined by the rate of diffusion of drug from the vehicle to the surface of the skin, the partitioning of the drug from the vehicle and the stratum, the degree of hydration of the stratum and variation in the extent to which they increase the hydration of the stratum^10,11.

Bactroban (mupirocin) is an antibiotic that prevents bacteria from growing on skin when applied topically. It is effective against impetigo and other spectrum of Staphylococcal infection of the skin. Bactroban exerts its bacteriostatic effect at low concentration and its bactericidal effect at high concentration when applied locally, it is very active against Gram negative bacteria. Nystatin Ointment USP is virtually non-toxic and nonsensitizing, and is well tolerated by all age groups including debilitated infants, even on prolonged administration. Nystatin Ointment USP is indicated in the treatment of cutaneous or mucocutaneous mycotic infections caused by Candida albicans [Monilia] and other Candida spp. The use of certain topical ointments has also been suggested in the treatment of superficial fungal infections. Nystatin Ointment USP is contraindicated in patients with a history of hypersensitivity to any of its components.

Topical antimicrobial agents can be used for some infections, but systemic therapy may be necessary for patients with extensive disease¹².

Chloramphenicol ointment is an antibiotic formulation that is used to treat bacterial eye infections of the eyelid, pink eye infection, bacterial inflammation of the cornea and covering of eye. It works by stopping the growth of bacteria¹³. Gentamicin ointment is used to treat minor skin infection and infection related some skin condition such as impetigo, folliculitis, eczema, psoriasis and minor cuts/burns or wounds. It is an aminoglycoside and has no effect on fungi¹⁴ . This study was carried out therefore to determine the activity of some antimicrobial ointments on selected bacterial and fungal isolates from clinical sources.