Research Article | Open Access
O.O. Akinnola , A.N. Williams, M.I. Oniha and B.O. Ogunleye
Department of Biological Sciences, Covenant University, Ota, Ogun State, Nigeria.
Article Number: 7587 | © The Author(s). 2022
J Pure Appl Microbiol. 2022;16(4):2507-2513.
Received: 01 February 2022 | Accepted: 19 May 2022 | Published online: 06 October 2022
Issue online: December 2022

Staphylococcal foodborne illness, caused by the ingestion of contaminated foods by induced Staphylococcus aureus enterotoxins, is one of the most recurrent foodborne diseases worldwide. Food handlers working in food-service establishments who carry enterotoxigenic isolates represent a reservoir for potential contamination leading to staphylococcal food intoxication. The aim of this research was to investigate the prevalence of nasal transmission of S. aureus among food handlers in a University community. A total of 100 nasal swab specimens were obtained from the food handlers and analyzed by standard laboratory techniques for isolation and identification. Questionnaires were administered to ascertain the risk determinants associated with nasal carriage of S. aureus. Antibiotic susceptibility testing of the isolates was done by disk diffusion method. Thirty-two food handlers were found to be carriers of S. aureus. Majority were females (63%), and 30% had been certified for food safety and handling. There were however no significant association between the nasal distribution of S. aureus together with established risk factors. Among the isolates, 93.75% were found to be resistant to penicillin, 50% to gentamicin and 50% to oxacillin. These findings indicate the need for training of food handlers on food safety, as well as the knowledge of antibiotic resistance.


Staphylococcal Foodborne Illness, Prevalence, Food Handlers, Hand Swabs, University Community


Food-borne illness has been one of the major health challenges of developed and developing countries worldwide, with up to 2 million deaths estimated in the former.1,2 Microbial presence or its metabolites in food products is one of the predominant problems in the food industry with significant menace to public health.3 One of the main causes of infections is Staphylococcus aureus a pathogen of global spread and increasing resistance to antimicrobials.4 Staphylococcal gastroenteritis (Staphylococcal Food Poisoning―SFP), one of the most common food-borne ailments results from the ingestion of one or more staphylococcal enterotoxins (SEs) in foods contaminated with the bacterium. This is due to the potential of the bacterium to generate more than 22 dissimilar enterotoxins, among which five of them have been established as a paramount cause of 95% of staphylococcal food poisoning occurrences.5,6,7 Another contributing factor is the poor personal hygiene of food-handlers functioning in food-service establishments (cafeterias and restaurants). As a consequence of colonization or skin infections of food handlers, contamination of the hands or dissipation through sneezing or coryza, there is a continual contamination of foods by Staphylococcus aureus. The ability of this bacterium to produce enterotoxins, depends on the method of storage or preservation of foods which may affect its metabolic activity in the food.1 Other species of Staphylococcus can retain enterotoxigenic genes, but they are only infrequently implicated in staphylococcal food poisoning epidemics. Carriers of antibiotic resistant Staphylococcus aureus which are enterotoxigenic will enable its continued resistance to one or more antimicrobial agents and its proliferation in the community.8 Given the need for a practical understanding of Staphylococcus aureus as a high-level foodborne pathogen, a major concern is the widespread under-reporting of diseases associated with food consumption in developing communities. This study is focused on determining the prevalence, risk factors and susceptibility pattern of Staphylococcus aureus obtained from food handlers to a range of selected antibiotics.

Materials and Methods

Designated Study Areas and Population
A cross-sectional study was conducted in the food utility establishments within the Covenant University community including cafeterias (3), butteries (17) and restaurants (1). Food handlers working in the study area, who had given informed consent, were involved in the study. The study was coordinated from January to April 2018. A self-administered questionnaire was completed by food handlers to obtain data on the hygiene practice and endangering factors associated with the nasal carriage of Staphylococcus aureus. Several variables were investigated as potential risk factors of S. aureus nasal carriage. These include certain general socio-demographic variables such as age, sex and ethnicity, hygiene practices, disease history, smoking habits, daily contact with animals, sporting activities, individual hospitalization/ hospitalization of household member, incidence of chronic sinusitis, rhinitis or skin diseases, use of antibiotics in the past 6 months and frequent skin puncture.

Sample Collection and Identification of Isolates
A total of 100 nasal swab samplings were procured from food handlers in the study areas and cultured on mannitol salt agar. Characteristic colonies were confirmed by Gram staining, catalase test, coagulase test and culture on blood agar for characteristic beta hemolysis of S. aureus according to Emeakaroha et al.9

Antimicrobial Susceptibility Testing (AST)
S. aureus isolates were analysed for antibiotic sensitivity by applying the Kirby-Bauer disk diffusion method in line with CLSI (Clinical and Laboratory Standards Institute) guidelines.10 The antimicrobial drugs tested include oxacillin (5µg), gentamicin (30µg), ciprofloxacin (5µg), sulphamethoxazole/trimethoprim (25µg), penicillin (10µg), erythromycin (15µg) and tetracycline (30µg).

Data Analysis
Data obtained were evaluated using IBM SPSS (Statistical Package for the Social Sciences) version 20.0 Software and chi-square (X2). A P value of ≤ 0.05 was considered statistically significant.


A total of 39 staphylococcal isolates were identified from the 100 samples collected, out of which 32 (32%) were Staphylococcus aureus and 7 were coagulase negative staphylococci. Based on gender difference, female food handlers (63%) were more compared to the males (37%). Young adults within the age of 18-19 (59%), workers with service experience of 1-10 years (59%) and high school leavers (44%) dominated the population of food handlers. The pedagogic levels, age category, sex, marital status and service years in relation to isolated identified are presented in Table 1. Based on hand washing practices, 91% of food handlers routinely cleaned hands with soap and water, 9% used only water for handwashing after using the toilet, 91% washed hands before preparing/serving food and 80% reported a habit of hand washing after touching nose in the middle of handling food items. Only 50% of the food handlers had received training in food safety, preparation and handling (Table 2). There was no significant association between potential risk factors investigated in connection to nasal carriage of S. aureus as shown in Table 3.

Table (1):
Socio-demographic characteristics of food handlers.

Absent Present Total
Count % Count % Count
Gender Male 21 56.76% 16 43.24% 37
N=100 Female 40 63.49% 23 36.51% 63
Age Group 18-29 31 52.54% 28 47.46% 59
N=100 30-50 9 75.00% 3 25.00% 12
50-70 21 72.41% 8 27.59% 29
Education Elementary 6 75.00% 2 25.00% 8
N=98 High school 29 65.91% 15 34.09% 44
Tertiary 26 56.52% 20 43.48% 46
Marital Status Single 36 55.38% 29 44.62% 65
N=100 Married 25 71.43% 10 28.57% 35
Years of Practice <1 15 51.72% 14 48.28% 29
N=95 1-10 41 69.49% 18 30.51% 59
11-15 2 66.67% 1 33.33% 3
>15 3 75.00% 1 25.00% 4

Table (2):
Hygiene practices of food handlers.

Staphylococci OR (95% CI)
Absent Present Total Count
Count  % Count  %
Received Yes 19 63.33% 11 36.67% 30 1.152
Certification No 42 60.00% 28 40.00% 70 (0.476-2.785)
Method of hand Using water only 4 44.44% 5 55.56% 9 2.096
washing after Using soap & 57 62.64% 34 37.36% 91 (0.526-8.344)
using the toilet water (ref)
Wash hands after Yes (ref) 51 63.75% 29 36.25% 80 1.583
touching nose No 10 52.63% 9 47.37% 19 (0.577-4.343)
Wash hands before Yes 58 63.74% 33 36.26% 91 2.929
preparing food No(ref) 3 37.50% 5 62.50% 8 (0.658-13.047)

Table (3):
Prevalence of S. aureus in relation to established risk factors.

Staphylococci OR 95% CI)
Absent Present Total Count
Count  % Count %
History of Sinusitis Yes 8 80.00% 2 20.00% 10 0.368
No 53 59.55% 36 40.45% 89 (0.074-1.834)
History of Rhinitis Yes 12 70.59% 5 29.41% 17 1.616
No 49 59.76% 33 40.24% 82 (0.521-5.018)
Skin Disease Yes 3 60.00% 2 40.00% 5 NC
No 58 61.05% 37 38.95% 95
History of hospitalization Yes 3 42.86% 4 57.14% 7 NC
in the past 6 months No 58 62.37% 35 37.63% 93
Used antibiotics in the Yes 25 64.10% 14 35.90% 39 1.240
past 6 months No 36 59.02% 25 40.98% 61 (0.541-2.843)
Frequent skin puncture Yes 1 100.00% 0 0.00% 1 NC
No 60 60.61% 39 39.39% 99
Contact with animals Yes 19 65.52% 10 34.48% 29 1.312
No 42 59.15% 29 40.85% 71 (0.533-3.227)
Household member Yes 13 59.09% 9 40.91% 22 0.873
who has contact with animals No 48 62.34% 29 37.66% 77 (0.332-2.295)
Household member who Yes 20 64.52% 11 35.48% 31 1.242
is a healthcare worker No 41 59.42% 28 40.58% 69 (0.516-2.990)
Household member Yes 6 66.67% 3 33.33% 9 NC
admitted to the hospital No 54 60.00% 36 40.00% 90
in the past year
Participate in close Yes 30 63.83% 17 36.17% 47 1.195
contact sport No 31 59.62% 21 40.38% 52 (0.530-2.695)

NC- Not computed because one category contains too few respondents.

The results of the antimicrobial testing showed that 93.75% of S. aureus were resistant to Penicillin, 50% to Gentamycin and 50% to Oxacillin (Table 4). However, 84.38% of the isolates were susceptible to Erythromycin and Trimethoprim-Sulphamethoazole (Figure).

Table (4):
Antibiotic Resistance Pattern of S. aureus Isolates.

Antibiotics Staphylococcus aureus (n=32)
Resistance n (%) Intermediate n (%) Sensitive n (%)
Penicillin G 30 (93.75) 0 (0) 2 (6.25)
Oxacillin 16 (50) 2 (6.25) 14 (43.75)
Ciprofloxacin 6 (18.75) 2 (6.25) 24 (75.00)
Erythromycin 3 (9.38) 2 (6.25) 27 (84.38)
Gentamycin 16 (50) 0 (0) 16 (50)
Trimethoprim 3 (9.38) 2 (6.25) 27 (84.38)
Tetracycline 11 (34.38) 3 (9.38) 18 (56.25)


Figure. Antibiotic Resistance Pattern of S. aureus Isolates.


The overall prevalence rate of 82% S. aureus isolates of this study is in line with previous report of 37.14% of S. aureus isolated among food handlers in Obafemi Awolowo University,11 but in contrast to the 20.5% of isolates among food handlers in Gondar University 1 and 21.2% of nasal carriage according to Simsek et al12 In this study, no relation was found between the nasal carriage of S. aureus and sex, age, education, marital status, present work location and service years (P > 0.05). This corresponds to Simsek et al.12, Dagnew et al.1 and Getenet et al.13 where the frequency of the nasal transfer of S. aureus was independent of the sociodemographic variables of the food handlers. Hygiene practices that include method of hand wash after using the toilet, after touching the nose, before preparing/serving food and frequency of hand wash had no association to the carriage of S. aureus.

With only 36.67% of the food handlers who were carriers of S. aureus having been trained with a certification in food safety preparation and handling, there is the need for the training of all individuals in food services. In the findings of Nasrolahei et al,14 the rate of bacterial contamination of foods by food handlers was high despite the practice of annual check–up thus portraying poor personal and environmental hygiene as well as ignorance of health promotion practices. There was negative significant association between the nasal carriage of S. aureus and the risk factors investigated in this study. Additionally, there was no significant association between the isolates and sample collection areas. There is nonetheless the need for the enforcement of basic hygiene practices among food handlers, as they serve as reservoirs for staphylococci, which could result in food intoxication.

Among the isolates obtained, there was a 93.75% resistance of S. aureus to Penicillin, in line with report that 90% of staphylococcal isolates and specifically 91% from the human nasal passage are resistant to penicillin.15 The 50% resistance of S. aureus to Gentamicin found in this study is in contrast to the 25.58% resistance reported by Alsamarai et al16 and complete susceptibility as reported by Achek et al.17 The 18.75% resistance observed for Ciprofloxacin by S. aureus is in contrast to the 0%, 6.97% and 9.8% reported in the studies of Wolde et al.18, Alsamarai et al16 and Dagnew et al.1 respectively. Similar report by Akinduti et al.19 revealed the resistance of S. aureus to some antibiotics including Penicillin, Ciprofloaxin among others.

The findings of this study revealed that food handlers with antibiotic-resistant S. aureus may constitute significant risk to the end users, enabling the spread of drug resistant S. aureus infections. Therefore, implementation of regular food handlers’ training on food safety, regular medical examination and consistent observation of personal hygiene of food handlers is of optimum necessity.


All the authors wish to acknowledge the financial support provided by Covenant University,  Nigeria for the publication of this research work.

The authors declare that there is no conflict of interest.

OOA conceived and designed the experimental study. ANW collected the samples, isolated and characterised the bacteria. OOA and ANW analysed and presented the results in figure and tables. OOA, ANW, MIO and BOO prepared and edited the manuscript. All the authors read and approved the final manuscript for publication.

This work was supported by the Covenant University Centre for Research Innovation and Discovery (CUCRID), Nigeria.

All datasets generated or analyzed during this study are included in the manuscript.

This study was approved by the Covenant Research Ethics Committee (CHREC), Covenant University, Ota, Ogun State, Nigeria (CU/BIOSCREC/BIO/2016/016).

Written informed consent was obtained from the participants before enrolling in the study.

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