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Studies on Staphylococcus aureus Isolated from Pimples

Ajayi Adesola Adetutu, Bibi Oritsewehinmi, Oniha Margaret Ikhiwili, Atolagbe Oluwabunmi Moradeke, Anosike Selina Odochi and Onibokun Elizabeth Adeola

Background and Objective: Pimples (acne) are small skin lesions or inflammations of the skin. The most common factor causing acne is the hormonal changes that occur during adolescent and teenage years. Antibiotics are becoming less effective in the treatment of pimples due to increasing concerns of antibiotic resistance. This study was therefore carried out to characterize the isolates from the pimples of Covenant University Students and to determine their antibiotics sensitivity pattern. Materials and Methods: A total of 20 swab samples were obtained from male and female students with obvious signs of pimples in Covenant University, Ota, Ogun State, Nigeria. The samples obtained were cultured on Mannitol Salt Agar and incubated at 37°C. Pure isolates obtained were subjected to Gram staining and other biochemical tests for identification. The isolates were further subjected to antibiotics sensitivity tests using antibiotic dics. Results: Macroscopic examination indicated that the organisms were convex, smooth and shiny. Microscopic examination revealed that the isolates were positive after employing the Gram Staining technique and they appeared as grape-like clusters. Biochemical tests revealed that the isolates were Coagulase positive, Catalase positive, Urease positive, Citrate positive, Methyl-Red positive, Voges-Proskauer negative and negative upon starch hydrolysis. The sugar fermentation tests revealed that the isolates fermented Glucose, Maltose, Galactose, Sucrose and Lactose, respectively. The antibiotic susceptibility test showed that isolates were resistant to Cotrimazole, Cloxacillin, Erythromycin, Gentamycin, Augmentin, Streptomycin, Tetracycline and Chloramphenicol. Conclusion: The results therefore indicated that the isolates were Staphylococcus aureus and other staphylococci species. Indiscriminate use of antibiotics should be avoided to prevent the development of resistant strains of the Staphylococci genera and other pathogenic organisms.

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Ajayi Adesola Adetutu, Bibi Oritsewehinmi, Oniha Margaret Ikhiwili, Atolagbe Oluwabunmi Moradeke, Anosike Selina Odochi and Onibokun Elizabeth Adeola, 2017. Studies on Staphylococcus aureus Isolated from Pimples. Pakistan Journal of Biological Sciences, 20: 350-354.

DOI: 10.3923/pjbs.2017.350.354

Received: January 24, 2017; Accepted: May 25, 2017; Published: June 15, 2017

Copyright: © 2017. This is an open access article distributed under the terms of the creative commons attribution License, which permits unrestricted use, distribution and reproduction in any medium, provided the original author and source are credited.


Pimple is the common name for a disorder that causes outbreaks of skin lesions known as acne1 Acne is a disorder of the sebaceous glands of the skin in which sebum secretions are excessive. The glands become plugged and inflamed in the process2,3. Acne is also known as Acne vulgaris. It is one of the most common skin diseases, affecting approximately 85% of people between the ages of 12-254,5. It is estimated that 45 million people in the United States have acne, with a prevalence of approximately 85% in the population between 15 and 24 years of age5,6. Skin and soft tissues infections are usually caused by Staphylococcus aureus and Streptococcus pyogenes7,8. Large portions of these infections are caused by normal skin flora and the nature and severity of the infection is dependent upon the site of inoculation and type of microorganism9. If the infection is left unattended to the organism, may spread to the surrounding tissues and the tiny lesion becomes a much larger, a swollen, cutaneous, inflamed, localized lesion walled by deposition of fibrin by the tissue and the walling off is to prevent the Staphylococcal infection from going further10. This study was therefore carried out to randomly sample the pimple present on faces of students of Covenant University for the presence of Staphylococcus aureus, to isolate and characterize the strains of Staphylococcus aureus obtained from the student’s pimple and determine the antibiotic susceptibility profile for the strains of Staphylococcus aureus. This will aid in the effective treatment of staphylococcal pimples infections.


Sample collection: Samples were collected from male and female students of Covenant University, Ota, Nigeria. The collection was carried out under aseptic condition using sterile swab sticks. The pus of the pimple was pressed out and taken with the sterile swab sticks. The swabs containing the inoculum were streaked on sterile Mannitol Salt Agar plates. The inoculated plates were then incubated at 37°C for 24 h. After incubation, the colonies which appeared golden yellow were isolated and sub-cultured on nutrient agar slants.

Grams staining test: A heat fixed smear from a 24 h old culture was prepared on a clean glass slide. The smear was stained with Crystal Violet solution for 1 min after which the solution was rinsed off with water. The slide was flooded with Lugol’s Iodine for 1 min. The iodine was rinsed off with water and then the slide was decolourized using 70% Ethanol for 30 sec. The slide was rinsed gently with water and counter stained with safranin solution for 1 min. The slide was washed with water and then air dried. The slide was observed under the microscope using the oil immersion objective lens.

Biochemical tests: The isolates were subjected to the following biochemical tests, catalase test, coagulase test, citrate utilization test, urease test, methyl red test, Voges-proskauer test, starch hydrolysis and sugar fermentation tests.

Antibiotic sensitivity testing: The disc diffusion method was used to determine the susceptibility and resistance of the organisms to the antimicrobial drugs. The inoculum was streaked on Mueller Hinton agar plates and a Gram positive antibiotic multi disk (commercial drug disc containing antibiotics with different concentrations) was aseptically removed and placed at the centre of the plate. The plates were incubated at 37°C for 24 h and the diameter of zones of inhibition formed around each antibiotic disc was measured.


Morphological and cultural characteristics: This study revealed that the isolates from the pimples swabs of twenty male and female students between the ages of 16-24 years streaked on Mannitol salt agar showed colonies which fermented Mannitol and appeared golden yellow (Table 1). Cultural and morphological characteristics indicated that the colonies are spherical in shape, appeared in clusters, non-spore forming and were Gram positive (Tables 2, 3). Biochemical tests carried out revealed that the isolates are Coagulase positive, Catalase positive, Urease positive, Citrate positive, Methyl-Red positive, Voges-Proskauer negative and they were negative upon Starch hydrolysis (Table 3).

Table 1:
Incidence of Pimples in relation to age and sex of the students
F: Female, M: Male

Table 2:
Morphology and Cultural Characteristics of Staphylococcus aureus associated with Students pimple

Table 3:
Gram’s staining reaction and Biochemical tests of the strains of S. aureus isolated from the pimple of students
KEY, F: Female M-Male, +: Positive, -: Negative

Table 4:Sugar Fermentation Properties of the Strains of S. aureus Isolated from the Students Pimple
A: Acid production, G: Gas production, AG: Acid and gas production

Table 5:Antibiotic Sensitivity Pattern of S. aureus Stains isolated from the pimples of students
KEY, COT: Cotrimazole CXC-Cloxacillin, STR: Streptomycin, TET: Tetracycline, GEN: Gentamycin, CHL: Chloramphenicol, ERY: Erythromycin, AUG: Augmentin

The sugar fermentation tests revealed that the isolates fermented Glucose, Maltose, Galactose, Sucrose and Lactose as shown (Table 4). The antibiotic sensitivity test showed that the isolates were resistant to cotrimazole, cloxacillin, erythromycin, gentamycin, augmentin, streptomycin, tetracycline and chloramphenicol (Table 5, 6). The results revealed that all the isolates are S. aureus strains and had least resistance to gentamycin and greater resistance to cloxacillin and augmentin.

The result of this investigation revealed that the isolates were Staphylococcus aureus. Staphylococcus aureus forms a normal part of the human skin11. S. aureus is found on the face and hands, particularly in individuals who are nasal carriers12. Although Staphylococcus aureus is a normal inhabitant of the skin, mucous membranes, respiratory and gastrointesinal tracts, it can invade any organ or system to produce infection ranging from localized to invasive diseases13.

Table 6:
Antibiotic Resistance Pattern of S. aureus strains isolated from pimples of Covenant University Students

Localized diseases include furuncles, impetigo, boils and other wound infections are community acquired. Suppurative and or invasive infections include septicemia, osteomyelitis, arthritis, endocarditis and pneumonia which is hospital acquired4.The species of Staphylococcus aureus isolated from the pimple of students on which different tests were carried out revealed the organism as a yellow, smooth, shining colonies on Mannitol salt agar and also appeared coccoid in shape and gave cultural and morphological characteristics consistent with those of Staphylococcus aureus. S. aureus has been implicated as a major organism associated with pus from acne14,15. The pathogenicity of Staphylococcus aureus in pimples has been attributed to the virulence factors possessed by the organism12. Michels et al.16 and De Luca and Valacchi17 reported that there are some biological changes on the skin surface lipids which allow the inflammation of acne and that the bacterial colonization of sebaceous follicle results in the production of inflammatory agents. The antibiotic sensitivity tests carried out indicated that the organism was resistant to gentamycin and chloramphenicol, implying the possibility of high efficiency of these antibiotics in the treatment of pimples. The strains were however sensitive to clotrimazole, tetracycline, cloxacillin, erythromycin, augmentin and streptomycin. The results revealed multiple antibiotic resistance of Staphylococcus aureus associated with pimple. Adejuwon et al.12 ported that the Staphylococcus aureus isolated from an individual was sensitive to gentamicin, tetracycline, amoxicillin, augmentin, chloramphenicol and sulphamethoxazole but resistant to ampicillin, erythromycin, cloxacillin, cotrimoxazole, streptomycin and penicillin. Ajayi et al.11 also reported that the staphylococcus isolates isolated from hand swabs obtained from female and male students’ palms at Covenant University, Ota were susceptible to ciprofloxacin, gentamycin, pefloxacin and amoxycillin but resistant to erythromycin, ceftriazone and cotrimoxazole antibiotics.


This study revealed that the S. aureus isolated from pimple swabs of students showed a high resistance to all the antibiotics tested. Therefore, indiscriminate use of antibiotics should be avoided and where antibiotics are to be administered, the choice of antibiotics in any given case should be based on the results of antibiotic sensitivity tests. Practicing clean personal hygiene is encouraged as an effective method of preventing the transmission and occurrence of pimples and other staphylococcal infections. Washing of the face regularly with antiseptic soaps and the use of hand sanitizers is also encouraged. Wounds and cuts should be properly covered and sharing of personal items such as clothing and towels, should be avoided. Awareness should be highly recommended amongst students of higher institutions particularly among the age group tested.


This research work revealed isolated microorganisms from male and female students with obvious signs of pimples and discovered that the isolates were staphylococcus species after characterization. The study therefore recommends that the indiscriminate use of antibiotics should be avoided to prevent the development of antibiotic resistant strains of staphylococci genera and other pathogenic organisms.


The Authors hereby acknowledge Covenant University for providing a suitable platform for carrying out this research and publishing cost. We also acknowledge the contribution of all technologists in the Department of Biological Sciences, Microbiology Unit of Covenant University.

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