Journal of Infectious Diseases & Preventive Medicine
Open Access

Strains of Salmonella enterica Isolated from Abattoirs in Ile-Ife, Osun State, Nigeria

Joseph Omololu-Aso^1*, K. Aliu¹, Oluwaseun O. Omololu-Aso² and Oluwagbenro Adesunloro^{1 *}Correspondence: Joseph Omololu-Aso, Department of Microbiology, Obafemi Awolowo University, Osun, Nigeria, Email:

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Introduction

Strains of Salmonella enterica are facultative aerobes. They are gram negative rod-shaped bacteria of the Enterobacteriaceae family. Most serotypes under the species are motile with peritrichous flagellation except Salmonella enterica serovar Pullorum and Salmonella enterica serovars Gallinarum which are non-motile strains as a result of their dysfunctional flagella.

The aim of this study was to determine the hygienic standard of selected abattoirs in Ile-Ife, Osun state, nigeria. The objectives were to: Isolate, identify and characterize strains of Salmonella enterica from abattoirs in three local government areas (Ife Central, Ife east and Ife north local government areas) in Ile-Ife, Osun state, Nigeria; determine the prevalence rate of the strains in the study area; and determine the susceptibility of the isolated strains to specific antibiotics.

Literature Review

Collection of samples

Forty-eight samples were obtained from abattoirs in three local government areas (Ife central, Ife east and Ife north local government areas) out of the four local government areas in Ile- Ife, Osun state, Nigeria. This was between September and November 2018.

Culture

The samples were transported to the microbiology laboratory, department of microbiology, Obafemi Awolowo university, Ile- Ife, Osun state, Nigeria and cultured on pre-enrichment media which were Nutrient agar and MacConkey agar (Oxoid, Ltd, Bashingstoke, Hampshire, England) for 18 hrs-24 hrs at 37°C. They were later transferred into Salmonella-Shigella agar (Oxoid, Ltd, Bashingstoke, and Hampshire, England) and incubated for 48 hrs at 37°C.

Identification of isolates

Biochemical tests carried out for the identification of the isolates include: Gram staining; Catalase test; Indole test; Citrate utilization test; Motility test; Methyl Red-Voges Proskauer (MRVP) test; Urease test; Triple sugar iron (Glucose, Lactose, H₂S) test.

Antibiotic susceptibility

Using the method of Adejuwon, et al., all isolates were subcultured on fresh nutrient agar plates using the zigzag method from stock culture and incubated for 24 hrs. Very little amount of the organism was picked and inoculated into appropriately labeled test tubes containing sterile distilled water (5 ml). This was shaken gently to ensure homogeneity. Standardization to 0.5 Mc Farland standard was done. Optical density readings were taken between 0.08–0.1 with the aid of a colorimeter. Using a swab stick, Muller-Hilton agar was inoculated aseptically with each isolate using the spread plate technique. With the aid of a sterile forceps the multiple antibiotic discs was picked and placed on the surface of each plate. Incubation was for 24 hrs. Zones of inhibition were measured in millimeter with the aid of a ruler before comparing with a CLSI Standard. The antibiotics used were: Septrin (Trimethoprim/Sulfamethoxazole, also known as Cotrimoxazole), Chloramphenicol, Sparfloxacin, Ciprofloxacin, Amoxicillin, Augmentin, Gentamycin, Pefloxacin, Tarivid (Ofloxacin), Strptomycin [1-5].

Salmonella isolates which showed growth when cultured on nutrient agar, MacConkey agar and Salmonella-Shigella agar (Oxoid, Ltd, Bashingstoke, Hampshire, England) with morphological characteristics specified in the Bergey’s Manual of Determinative Bacteriology were obtained. Salmonella enterica isolates were identified. Table 1 shows the biochemical characterization of the isolates. Table 2 shows the morphological reaction of the isolates to the selected media. A total of twentytwo strains of Salmonella enterica were obtained from a total of forty-eight samples collected (representing a prevalence rate of 45.8%). Of these: Five strains of Salmonella from twenty samples were obtained from Ife central local Government (representing 25% prevalence rate in Ife central local government and 10.4% prevalence rate in the total study area); Eight strains from fifteen samples tested were obtained in Ife east local government (representing 53.3% prevalence rate in Ife East local government and 16.7% prevalence rate in the entire study area); Nine strains were obtained from thirteen samples tested in Ife North Local Government Area (representing a prevalence rate of 69.2% in Ife North local government Area and a prevalence rate of 18.7% in the entire study). The prevalence rate of Salmonella enterica in the three local government areas in Ile-Ife, Osun state, Nigeria is represented in Table 3 [6-9].

Table 1: Biochemical tests.

Table 2: Morphological tests.

Table 3: The prevalence rate of Salmonella enterica in three local government areas in Ile-Ife, Osun state, Nigeria.

The results of the susceptibility of the isolates to various antibiotics used are presented in Table 4. Augmentin has proven to be the most effective on the isolates. 54.5% of the total isolates were susceptible to Augmentin. The percentage of the isolates resistant to Tarivid, Pefloxacin, Gentamycin, Chloramphenicol, Amoxicillin, Ciprofloxacin and Augmentin were: 100%, 95.5%, 95.5%, 86.4%, 68.2%, 27.3% and 22.7% respectively [10-12].

Table 4: Antibiotic susceptibility profile of Salmonella enterica isolates.

Discussion

The isolates of Salmonella in this research investigation were motile gram negative small rods. Grimont and Weill reported similar findings. There seemed to be a high prevalence of Salmonella enterica (45.8%) in the studied environs. Igbinosa and Beshiru reported a higher prevalence (69.44%) in Edo state, Nigeria. In this study, we observed a prevalence of 25% in Ife central local government. From an earlier investigation, Omololu-Aso, et al. reported a lower (40%) prevalence of Salmonella enterica in same Ife central local government in 2017. Makut, et al. worked on cow milk products sold in Keffi metropolis, Nasarawa state, Nigeria. They observed a lower prevalence (15.7%) of this isolate in their investigation. According to Bello, et al., contamination of cow meat may arise in the process of removing the gastrointestinal tract during slaughtering.

The Salmonella isolates in this study exhibited multi-antibiotic resistance. The isolates were significantly sensitive to Augmentin. Susceptibility of the isolates to this antibiotic was 54.5%. In 2017, Omololu-Aso, et al. reported a higher susceptibility of Salmonella isolates to Augmentin (80%) from a similar study conducted in Osun state, Nigeria. Tarivid, Pefloxacin, Gentamycin, Chloramphenicol, Amoxicillin and Ciprofloxacin had resistance profiles of 100%, 95.5%, 95.5%, 86.4%, 68.2% and 27.3% respectively for our isolated Salmonella strains. Omololu-Aso, et al. in their previous study observed low resistance of their Salmonella isolates to Tarivid (10%). Makut, et al. worked on cow milk products in Keffi metropolis. They reported that their Salmonella isolates showed 71.4% resistance to Chloramphenicol. This is consistent with the findings of our present study. Igbinosa and Beshiru observed 100% resistance of their Salmonella isolated from abattoirs in Edo state, Nigeria to Gentamycin. This is close to the 95.5% resistance observed in this study.

In Nigeria, many abattoirs dispose their effluents directly into streams and rivers without any form of treatment. The slaughtered animals are washed by the same water. This was observed during the sampling regime of this study. The occurrence of a high total heterotrophic bacteria count and a high Salmonella count in the effluents from such abattoirs poses lots of ecological and epidemiological risks.

Contamination of abattoir surfaces may emanate from the butchers, which could be as a result of using ungloved hands during dressing and processing of the carcass in the slaughtering hall. In addition, the foot wears used by the butchers could function as a vehicle for faecal contamination, since processing and dressing of the carcasses occurs on the open floor in the slaughter houses. Moreover, in developing countries like Nigeria, water bodies such as rivers are used for drinking, bathing, washing, watering of crops and other domestic purposes which also indicate a high impact on the public health of the users. Similar study conducted by Mor-Mur and Yuste indicated that bacteria isolated from wastes and abattoir products include Pseudomonads, Salmonella, Klebsiella and Proteus.

Conclusion

It is concluded from this study that effluents from abattoirs could be potential sources of reservoirs and dissemination of antibiotic-resistant Salmonella between animals and humans as well as the environment. The resistance to antibiotics is most likely due to misuse, widespread and lengthy use of antibiotics amongst animals and humans in the study areas.

Recommendations

Regular surveillance network systems to track resistance patterns of Salmonella serovars circulating in abattoirs and other environmental sources should be put in place. Implementing suitable Hazard Analysis and Critical Control Points (HACCP) procedures to decrease the cross-contamination from these environmental sources as well as food animal handlers and the final consumers could decrease the occurrence of multipleantibiotic resistant Salmonella in the environment.

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