Isolation, identification and antimicrobial susceptibility profile of Salmonella isolated from poultry farms in Addis Ababa, Ethiopia.

BACKGROUND: Salmonella has been found to be the major cause of foodborne diseases and a serious public health problem in the world, with an increasing concern for the emergence and spread of antimicrobial-resistant strains.
METHOD: A cross-sectional study was conducted on poultry and poultry farms in Addis Ababa from February 2016 to April 2016 to determine the occurrence and evaluate the antimicrobial susceptibility profile of Salmonella isolates. A total of 200 samples consisting of the cloacal swab (n = 168), pooled litter (n = 12), hand swab (n = 8), pooled feed and water (n = 12) were collected separately from six poultry farms. The samples were examined for the presence of Salmonella through culturing on bacteriological media. Descriptive statistics, Pearson's Chi-square (X2 ) and bivariate logistic regression were used in the analysis of the data. Accordingly, out of 200 samples, 23 (11.50%) were Salmonella positive, of which 21(12.50%) were in cloacal swab and 2(16.67%) in the pooled litter. There was no statistical association between the bacteriological status of sample type and Salmonella positivity (X2  = 3.07, P = 0.545). However, there was a statistical association between farms and the rate of Salmonella isolation (X2  = 22.21, P ≤ 0.00). The antimicrobial susceptibility testing for Salmonella isolates was conducted following the Kirby-Bauer disc diffusion method (1961).
RESULTS: Out of 23 samples tested, 95.65% of them were resistant to at least one or more antimicrobials. Multiple drug resistances were observed for 69.56% of Salmonella isolates. The highest resistance (73.9%) was observed in kanamycin followed by tetracycline (65.2%) and streptomycin (56.3%). gentamycin was the most effective antibiotic (95.7%; sensitivity) followed by ciprofloxacin (78.3% sensitivity) and ampicillin (69.6% sensitivity.
CONCLUSION: This current study finding indicated that further detailed epidemiological and molecular studies are essential on the frequency and sources of acquisition of resistant genes.

INTRODUCTION

Foodborne pathogens are the most common problems of recent times and distributed across the world that had ultimately become a public health concern. Nowadays, individuals have been suffering from various foodborne diseases worldwide due to contaminated food and water consumption (Hendriksen et al., 2007; Majowicze et al., 2010). Among the pathogens, the genus Salmonella is considered the most prevalent foodborne pathogen globally and has been found to be the major zoonotic organism with a serious public health implication (Carrasco et al., 2012; Sánchez‐Vargas et al., 2011). Foodborne diseases are common in developing countries including Ethiopia because of the prevailing poor food handling and sanitation practices, inadequate food safety laws, weak regulatory systems and lack of education for food handlers (WHO, 2004). Salmonellosis is an infectious and economically important disease of humans and animals caused by different Salmonella species (OIE, 2000). The ubiquity of Salmonella isolates makes a constant impurity hazard in all raw food items and is associated with occurrences of human salmonellosis (Carrasco et al., 2012; Tadesse, 2014). Foodborne Salmonella infection spread is recognised as the key reason for Salmonella contaminations, with many food sources and supplies implicated in these infections (Majowicz et al., 2010). Salmonella consists of mainly two species, namely, Salmonella enterica (S. enterica) and S. bongori. Furthermore, S. enterica was previously categorised into six subspecies upon biochemical tests and molecular characterisation. Salmonella enterica subspecies enterica is the major subspecies that is highly a distress as a result of virulent strains that could cause salmonellosis in animals and human beings. Food items that are derived from animal products, particularly poultry and poultry products, are frequently implicated in erratic circumstances and outbreaks of Salmonella infection in humans (Sánchez‐Vargas et al., 2011). Previously FAO (2002), indicated that poultry and poultry products are a major foodborne infection vector and regularly among the prominent animal sources of human salmonellosis during food supply. The author has also indicated that human beings could acquire Salmonella infection through ingestion of raw or undercooked animal‐derived food items, mainly poultry products. Isolation of Salmonella species in poultry foodstuffs is a worldwide public health distress including our country, Ethiopia. Infection with various species of Salmonella could result in diverse clinical manifestations such as inflammation of intestinal epithelia, diarrhoea, vomiting and typhoid fever (Crump & Mintz, 2010).

Various contamination levels have been reported by numerous studies worldwide. A study finding in Addis Ababa revealed a prevalence of 5.21% Salmonella isolates from eggs purchased from local markets (Bayu et al., 2013). A prevalence of 5.3% has been found from eggs shells from the open market purchased eggs in and around Haramaya Town (Kemal et al., 2016) and a prevalence of 18% from eggs in Gondar. The common exercise of using antimicrobial agents to human and animals to mitigate disease‐causing agents play a crucial role in the emergence and antimicrobial‐resistant bacteria that are successively transmitted to humans through the food chain. Moreover, antibiotics have a surprising ability to accelerate animal growth or growth promoter. Currently, more antibiotics are used in poultry, swine and cattle to promote growth and prevent disease than are used by the entire human population (FDA, 2015). Human salmonellosis is considered as a main bacterial root cause of foodborne diarrhoeal problem across the globe, and food items derived from animal origin act as a vehicle in the transmission of Salmonella species. Feed items such as water, faeces, poultry wastes, cages and litter contaminated with Salmonella are central sources of infection. Several research results showed the distribution of Salmonella in various sampling points in poultry surroundings or on antibiotic resistance, virulence and control strategies.

Discontinuation treatment and continuous undiscriminating uses of antimicrobials against diarrhoeal pathogens including Salmonella have presumptively assumed the possible causes for the development of antibiotic resistance and antimicrobial resistance is, therefore, a multi‐sectorial problem encompassing the interface between humans, animals and the environment (Marshall & Levy, 2011). There is inadequate information available on the Salmonella isolated from poultry products in the country though the disease is nationally as well globally a concern and a leading zoonotic pathogen (Carrasco et al., 2012). Despite being a major zoonotic, foodborne and pathogen with high drug resistance along with diversity in its strains and host ranges, there is limited study on Salmonella in Ethiopia. Therefore, the purpose of this research work was to determine the occurrence of Salmonella from poultry and poultry farms and to evaluate the antimicrobial susceptibility profile of Salmonella isolates in Addis Ababa, Ethiopia.

MATERIALS AND METHODS

Study area

The study was conducted in Addis Ababa, which is located 2408 m.a.s.l and receives an annual mean rainfall of 1200 mm, with average minimum and maximum annual temperature of 9.4 and 23.2°C, respectively (National Metrological Service Agency, 2002). Based on the preliminary 2007 census results, Addis Ababa has a total population of 2,738,248, consisting of 1,304,518 men and 1,433,730 women. The city is fully urban, with no rural dwellers within the city's administrative boundaries. Addis Ababa contains 22.9% of all urban dwellers in Ethiopia. With an estimated area of 530.14 square km, this chartered city has an estimated density of 5165.1 inhabitants per square km (Central Statistical Agency of Ethiopia, 2008).

Study population

The study populations were healthy chickens, farm attendants, feed and drinking water for chickens.

Study design and sample collection

A cross‐sectional study was conducted in this research. The samples were collected from February 2016 to April 2016. A total of 200 samples consisting of cloacal swab (n = 168), personnel hand swab from farm attendants (n = 8), pooled house litter (n = 12), pooled feed (n = 6) and pooled water (n = 6) were collected from chicken farms in Addis Ababa. Out of six poultry farms studied in this research, five farms consisted of layers, and one farm consisted of broilers. All farms were small‐scaled and the farms comprised 257–400 layers and broilers: Farm A (257), Farm B (318), Farm C (400), Farm D (367), Farm E (339) and Farm F (349) and all chickens aged above 45 days old. The cloacal swab was collected from the cloaca of broiler (n = 103) and layer (n = 65). Pooled litter samples were taken directly from five areas (four from the corner and one from the middle) of each chicken house. Personnel hand swab samples were taken after the personnel were working and before washing their hand. Pooled water and feed samples were taken directly from drinking water and chicken feed available on each farm. Each sample was taken aseptically and put into a test tube containing pre‐enrichment media (buffered peptone water [BPW]). The samples were transported after being collected in a portable container with ice packs (at 4°C) to the Microbiology Laboratory and were processed upon arrival or kept at +4°C overnight.

Isolation procedure of Salmonella

The methods used in the isolation of Salmonella were according to the techniques recommended by the International Organisation for Standardisation (ISO 6579, 2002). The isolation involves three steps: pre‐enrichment in pre‐enrichment broth media, enrichment in selective media, plating on selective media and biochemical confirmation of suspected colonies from selective agar media.

Pre‐enrichment in non‐selective broth medium

All samples were pre‐enriched separately with an appropriate amount of BPW (CONDA) (1:9) and were incubated for 18–24 h at 37 ± 1°C.

Enrichment in selective broth media

Tetrathionate broth base (Titan Biotech Ltd.) and Rappaport Vassiliadis Salmonella enrichment broth (Himedia MH1491) were used for selective enrichment of all samples. A portion (1 ml) of the pre‐enriched culture was aseptically transferred to 10 ml of tetrathionate broth base containing test tube, and another 0.1‐ml pre‐enriched culture was aseptically transferred to test tubes containing 10 ml of Rappaport Vassiliadis Salmonella enrichment broth and incubated at 37 ± 1°C and 41.5 ± 0.5°C for 24 h, respectively.

Plating out and isolation

Xylose Lysine Deoxycholate (XLD) agar (Oxoid CM0469) and brilliant green agar (BGA) base modified (Himedia M016) plates were used for plating out and isolation purpose. A loop full of inoculums from RV broth and tetrathionate broth was transferred and streaked onto the surface of XLD agar and BGA base modified separately. The plates were incubated at 37 ± 1°C for 18–24 h. After incubation, the plates were examined for typical and atypical colonies of Salmonella. On XLD agar, typical colonies can be colourless, very light, slightly shiny and transparent (colour of the medium) with a dark tinted centre, surrounded by a light red area and yellow edge, or of pink to red colour, with a black centre or without a black centre. Hydrogen sulphide (H2S) (+) colonies are colourless or light pink with darker centres, and lactose (+) colonies are yellow or without the characteristic blackening; whereas on BGA, typical colonies are transparent, colourless or light pink, and the colour around colonies changes from pink to light red. For confirmation, presumptive Salmonella colonies were selected from every selective plating media and subcultured on nutrient agar (Oxoid CM0003) in a manner that allow isolated colonies to develop and incubate at 37°C for 18–24 h for further confirmation by biochemical tests.

Biochemical confirmations

The biochemical identification of the organism was done by performing the biochemical tests. The biochemical tests were done as stated on Bergey's Manual of Determinative Bacteriology. Each identified colony with typical Salmonella morphology was confirmed biochemically by triple sugar iron (TSI) agar (Oxoid CM0277), Urease (Himedia M111A), Simmons’ citrate agar (Himedia M099, India), Indole (Oxoid CM0129), lysine iron agar (LIA; Oxoid CM0579), methyl red (MR) and Voges–Proskauer (VP) (Himedia M070) tests. Colonies producing red slant (alkaline), yellow butt (acidic) on TSI agar with H2S production and bubbles formation/cracking at the butt (gas production), negative urea utilisation (yellow), positive citrate utilisation (deep blue slant), negative for indole production from tryptophan, positive LIA agar (alkaline slant/alkaline butt), positive for MR test and negative for VP test were considered Salmonella positive (ISO 6579, 2002). LIA (Oxoid CM0579) was used to demonstrate hydrogen sulfide production and the decarboxylation or deamination olysine. These Salmonella positive samples showed alkaline slant/alkaline butt. Isolates presumptive of Salmonella for all tests were cultured on nutrient agar (Oxoid CM0003) for antimicrobial susceptibility testing.

Antimicrobial susceptibility test of Salmonella isolates

The antimicrobial susceptibility testing for Salmonella isolates was carried out following the Kirby–Bauer disc diffusion method on Mueller–Hinton agar (Oxoid CM0337) as described in the Clinical and Laboratory Standards Institute (CLSI) guidelines (CLSI, 2013). From each isolate, biochemically confirmed well‐isolated colonies grown on nutrient agar (Oxoid) were transferred into sterilised tubes containing 5 ml of tryptone soya broth (Oxoid). The broth culture was incubated at 37°C for 4 h until it achieved the 0.5 McFarland turbidity standard. A sterilised cotton swab was dipped into the suspension, and the bacteria were swabbed uniformly on the entire surface of Muller–Hinton agar plate. The plates were held at room temperature for 30 min to allow drying. Antibiotic discs with known concentrations of antimicrobial were applied aseptically onto the surface of the plates at an appropriate special arrangement with the help of a sterile pair of forceps on Mueller–Hinton agar plates. The plates were then inverted and incubated at 37°C for 24 h. The antibiotic discs (Oxoid) uses: ampicillin (AMP,10 μg), chloramphenicol (C,30 μg), tetracycline (TE,30 μg), streptomycin (S,10 μg), gentamycin (CN,10 μg), nalidixic acid (NA,30 g), ciprofloxacin (CIP,5 μg), cefoxitin (FOX,30 μg), kanamycin (K,30 μg) and sulphamethoxazole/trimethoprim (SXT,25 μg). After incubation, the diameter of clear zones produced by antimicrobial inhibition of bacterial growth was measured to the nearest mm using a transparent straight line ruler and classified as susceptible, intermediate and resistant categories according to CLSI guidelines (CLSI, 2013).

Data management and analysis

The data were entered into Microsoft excel 2010 and analysed using the SPSS statistical software package version 20 (IBM SPSS statistics). Descriptive statistics were used to compute proportions and frequency distributions of the rate of Salmonella isolation among various sampling point. Pearson's Chi‐square (X2) test was used to assess the association in the positivity of Salmonella isolates from samples originating from poultry, poultry house litter and other sources. Salmonella isolates were further screened for susceptibility to 10 different drugs and classified as susceptible, intermediate and resistant using frequency and proportions. Multi‐drug resistance (MDR) was considered if and only if one Salmonella isolate was resistant in three or more antimicrobial categories. A difference was taken as significant at P < 0.05 at 95% confidence interval for the variables analysed by X2.

RESULTS

Frequency of isolation of Salmonella

Out of the total 200 samples collected for Salmonella bacteriological isolation, 23 (11.50%) were positive. Out of 23 Salmonella isolates, the distribution of the isolates with respect to sample type are described as follows: 21(12.50%) from cloacal swab and 2(16.67%) from pooled litter, there was no Salmonella isolated from personnel's hand swabs, pooled feed and pooled drinking water. This is to mean that Salmonella isolates were obtained from some sampling points such as cloacal swab and pooled litter. On the other hand, we could not get Salmonella isolates from the other sampling points like personnel's hand swabs, pooled feed and pooled drinking water. However, this Salmonella positivity among the various sampling points has no statistical association between these different sample types (sampling points) and Salmonella positivity (X2 = 3.79, P = 0.545).

Conversely, among the poultry farms that were assessed for the occurrence of Salmonella bacterium, we have found that there was a statistical association between farms and the rate of Salmonella isolation (X2 = 22.21, P ≤ 0.00) as depicted in Table 1. In detail, more Salmonella isolates 29.79% (n = 14) and 9.30% (n = 4) were found in Farm C and Farm F, respectively, than the remaining farms. The possible reason for the variation of Salmonella occurrence among the poultry farms could be the hygienic status difference between farms and close vicinity to the main roads and parking. Moreover, relatively the farm's size was slightly high as compared to the others, and the number of visitors has increased to the farms. So, this could be one contributing factor for the occurrence of Salmonella bacterium. Some study findings also showed that chickens might be contaminated by the mechanical carriage of Salmonella on the wheels of vehicles or human footwear from areas of access to inside the premises.

TABLE 1

The rate of Salmonella occurrence from different sampling points

		Positive	Negative	Total	Proportion (%)	Chi‐square (X2 )	P‐value	95% CI
Farm name	A	2	18	20	10.00	22.21	0.00	8.61	11.39
	B	1	23	24	4.17			3.35	4.98
	C	14	33	47	29.79			28.23	31.35
	D	0	33	33	0.00			–	–
	E	2	31	33	6.06			5.22	6.90
	F	4	39	43	9.30			8.39	10.21
Total		23	177	200	11.50			11.03	11.97
Sample type	CS	21	147	168	12.50	3.79	0.545	11.97	13.03
	F	0	6	6	0.00			–	–
	L	2	10	12	16.67			14.36	18.98
	PHS	0	8	8	0.00			–	–
	W	0	6	6	0.00			–	–
Total		23	177	200	11.50			11.03	11.907
Poultry type	0	2	30	32	6.25	2.273	0.321	5.38	7.12
	B	15	87	102	14.71			13.96	15.45
	Ly	6	60	66	9.09			8.36	9.82
Total		23	177	200	11.50			11.03	11.97

Note: Among the sample types (sampling points) we have determined, cloacal swab samples were more positive 12.5% (n = 12) followed by pooled litter samples though no statistical association between sample type and Salmonella positivity was found (X2 = 3.07, P = 0.545). As we mentioned, Farm C and F were positive even from pooled litter. Sample type: CS, cloacal swab; F, feed; PHS, personnel hand swab; L, litter and w, water. Poultry type: 0 = sample source other than poultry, b = Broiler and ly = layer.

Antimicrobial susceptibility pattern of Salmonella isolated from different sample types

Antimicrobial susceptibility results of 23 Salmonella isolates were shown in Table 2. Gentamycin was the most effective antibiotic (95.7% sensitivity) followed by ciprofloxacin (78.3% sensitivity) and ampicillin (69.6% sensitivity). The highest resistance (73.9%) was observed to kanamycin followed by tetracycline (65.2%) and Streptomycin (56.3%). No intermediate resistance was seen in all isolates to gentamycin, ampicillin and kanamycin as indicated in (Table 3).

TABLE 2

Multiple drug resistance patterns of Salmonella isolated from different sample sources

No. antimicrobial resistance	Antimicrobials	No. of Salmonella isolates (%)
One	TE	3 (13.04)
	S
	K
Two	TE‐NA	3 (13.04)
	TE‐K
	NA‐K
Three	TE‐SXT‐K	3 (13.04)
	AMP‐K‐SXT
	AMP‐SXT‐S
Four	TE‐AMP‐S‐K	4 (17.39)
	TE‐AMP‐K‐SXT
	TE‐FOX‐S‐K
	NA‐S‐K‐C
Five	TE‐FOX‐S‐K‐C	5 (21.74)
	TE‐NA‐FOX‐S‐K (2)
	TE‐AMP‐NA‐K‐SXT
	TE‐NA‐S‐K‐C
Six	NA‐FOX‐S‐K‐SXT‐C	2 (8.70)
	CN‐TE‐AMP‐S‐K‐SXT
Seven	TE‐NA‐CIP‐S‐K‐SXT‐C	1 (4.35)
Eight	TE‐AMP‐NA‐FOX‐S‐K‐SXT‐C	1 (4.35)
Nine	TE‐ CIP‐ AMP‐ FOX‐S‐K‐SXT	1 (4.35)
Overall		23 (100)

Note: We say multi‐drug resistance, if and only if Salmonella isolates are resistant ≥ 3 antimicrobials.

Abbreviations: AMP, ampicillin; C, chloramphenicol; CIP, ciprofloxacin; CN, gentamycin; FOX, cefoxitin; NA, nalidixic acid; No, number;

S, streptomycin; K, kanamycin; SXT, sulphamethoxazole/trimethoprim; TE, tetracycline.

TABLE 3

Antimicrobial sensitivity test results of Salmonella isolates

	Status of antimicrobial sensitivity
Type of antimicrobial	Resistant (%)	Intermediate (%)	Sensitive (%)
CN	1 (4.3%)	0 (0.0%)	22 (95.7%)
TE	15 (65.2%)	3 (13.0%)	5 (21.7%)
AMP	7 (30.4%)	0 (0.0%)	16 (69.6%)
NA	11 (47.8%)	2 (8.7%)	10 (43.8%
FOX	6 (26.1%)	5 (21.7%)	12 (52.2%)
CIP	1 (4.3%)	4 (17.4%)	18 (78.3%)
S	13 (56.3%)	5 (21.7%)	5 (21.7%)
K	17(73.9%)	0 (0.0%)	6 (26.1%)
SXT	9 (39.1%)	3 (13.0%)	11 (47.8%)
C	7 (30.4%)	4 (17.4%)	12 (52.2%)

Abbreviations: AMP, ampicillin; C, chloramphenicol; CIP, ciprofloxacin; CN, gentamycin; FOX, cefoxitin; NA, nalidixic acid; S, streptomycin; K, kanamycin; SXT, sulphamethoxazole/trimethoprim; TE, tetracycline.

Multiple drug resistance patterns of Salmonella isolated from different sample sources

Of the 23 isolates, 69.56% showed resistance for three or more of the antimicrobials tested, and all 23(100%) were resistant to one or more antimicrobials. These MDRS are summarised in Table 3.

DISCUSSION

The main rationale of taking samples from different sampling points (poultry house elements) of the poultry farm is to look at the distribution of Salmonella bacterium among the sampling points in particular and poultry farms in general. As a result, we found variations in the distribution of Salmonella isolates, but the variations were not statistically significant. Moreover, having detailed information about the distribution of this zoonotic bacterium on the various sampling points will ultimately help us to know the remarkable health problems to these people who engage in poultry farms that have not followed strict biosecurity protocols and also aid in taking measures targeting in the mitigation of the problem based of the magnitude of the bacterium in these different sampling points. In our current study finding, from the total of 200 different samples from poultry farms examined for Salmonlla, 11.50% (23/200) were positive, of which 12.50% (21/168) were from cloacal swab, and 16.67% (2/12) were from pooled house litter. This result was in agreement with the findings of Marianne et al. (2007) who reported 11.8% Salmonella from apparently healthy poultry imported to Denmark for slaughter. In contrast, a report from Pakistan by Aijaz et al. (2010) indicated that 38% of Salmonella was isolated from poultry meat, which was higher than the results of our current study. This may be due to the difference in geographical and poultry management conditions, like housing, feeding, and so forth. Salmonella was not isolated from pooled feed samples. This finding disagrees with Maung (2004) who reported 0.6% of Salmonella isolated from poultry feed sources. This may be due to the low number of our sample size, the absence of rodents in the farms, which are main contaminants of feed, or heat treatment of the feed. In the present study, the rate of isolation of Salmonella from different farms showed a statistically significant difference (X2 = 22.21, P ≤ 0.00). This may be related to the difference in hygienic status among farms and close vicinity to roads and parking. Rose et al. (2000) reported an increased risk of Salmonella contamination associated with trucks running and parking in close vicinity to the poultry houses. It is thus possible that chickens might be contaminated by mechanical carriage of Salmonella on the wheels of vehicles or human footwear from areas of access to inside the premises.

The occurrence of Salmonella in the broiler (17.71%) in this study was slightly higher than the findings of Ibrahim et al. (2013) who reported 16.67% isolates of Salmonella from commercial broiler farms in Egypt. However, our findings are lower than those detected by Caldwell et al. (1995) (18.89%). Regarding the occurrence of Salmonella in layers, the isolation rate (9.09%) was to some extent in agreement with the data obtained by Ibrahim et al. (2013) who demonstrated that Salmonella was isolated with a percentage of 9.01% from layer farms. The high level of Salmonella isolation in broilers evaluated in this study may be attributed to ingestion of contaminated feeds, water or litter or using contaminated equipment (Gast, 2003).

All the Salmonella isolates were tested against a panel of 10 antimicrobials available at the local market. Out of 23 isolates, all (100%) of them were resistant to one or more antimicrobials tested. Accordingly, higher antimicrobials resistance of 73.9%, 65.2% and 47% was observed against kanamycin, streptomycin and nalidixic acid. Resistance to tetracycline was observed in 65.2% of the isolates, which is higher than that reported in different studies: 46.6% in Senegal (Bada‐Alambedji et al., 2006) and 36% in Portugal (Antunes et al., 2003). Tetracycline has been one of the most commonly used antibiotics for production animals; from day‐old chicks to broiler chickens, they are exposed to antimicrobial drugs during their growth phase. Therefore, resistance to drugs such as tetracycline could be expected since the members of this class (chlortetracycline and oxytetracycline) are approved for use in broiler feeds for the purpose of growth promotion according to reports by Jones and Ricke (2003). Resistance to streptomycin (56.3%) was also higher and is in conformity with other findings (Cardoso et al., 2006). This resistance to tetracycline and streptomycin commonly observed among the Salmonella isolates has been frequently reported; this elevated resistance may be explained by the possible diffusion of the tet(A) resistance gene observed in an epidemiological study with Salmonella strains isolated from animals (Pezzella et al., 2004).

Of 23 isolates, all 100% (23/23) and 78.3% (18/23) showed high susceptibility to gentamycin and ciprofloxacin, respectively. This was lower than with the findings of Begum et al. (2010), who reported (100%) of Salmonella strains isolated from chicken eggs, intestines, and environmental samples were susceptible to gentamycin and ciprofloxacin. This investigation indicates that Salmonella isolates becoming resistant to these antimicrobials. Our findings regarding resistance to kanamycin (73.9%) were completely contrasted with the reports of Carraminana et al. (2004) who reported (2.8%) found in Salmonella isolated from a poultry slaughterhouse in Spain.

A total of 15 different multiple drug resistance patterns were observed: one isolate resistance to eight antimicrobials, one isolate resistance to seven antimicrobials, two isolates resistant to six antimicrobials with two different resistance patterns, five isolates resistance to four antimicrobials with four different resistance patterns, four isolates resistance to four antimicrobials with four different resistance patterns and three isolates resistant to three antimicrobials with three different resistance patterns. Moreover, the result of the current study revealed intermediate resistance of commonly used antibiotics including streptomycin, tetracycline and sulphamethoxazole/trimethoprim. This implies Salmonella is not inhibited by the usual achievable concentration of the antimicrobials with a normal dosage schedule as reported by Abebe et al. (2013).

CONCLUSION

In general, from this cross‐sectional study, it can be concluded that the occurrence of Salmonella from poultry farms in Addis Ababa was 11.50%. This result is significantly high to be a potential source of foodborne salmonellosis putting human health at risk via the food chain. The results of the present study indicate single or multiple resistance of Salmonella isolated from poultry, which constitutes a potential source of transmission of these resistant strains to man and poses a problem in public health. Resistance was mainly observed to kanamycin followed by tetracycline and streptomycin, whereas gentamycin and ciprofloxacin seem still effective to be used. Therefore, a detailed epidemiological survey has to be made to determine the sources of contamination and associated risk factors in poultry and poultry farms. Moreover, molecular studies are essential on the frequency, sources of acquisition of resistant genes and distribution of antimicrobial resistant Salmonella among food animals, food products and humans in Ethiopia to apply appropriate measures to minimize Salmonella infection.

ETHICAL STATEMENT

Written ethical approval and consent for this study was obtained from Addis Ababa University, College of Veterinary Medicine of Animal Research Ethics and Review committee. Oral consent was also obtained from the owners to take samples from their chicken and for further research use of the samples.

CONFLICT OF INTEREST

The authors declare that there are no conflicts of interest regarding the publication of this paper.

AUTHOR CONTRIBUTION

Conceptualisation, methodology, writing–review and editing: Yasin Mohammed.

Teshager Dubie: Contributed to data collection, data analysis, interpretation of data, writing and editing of the manuscript.

PEER REVIEW

The peer review history for this article is available at https://publons.com/publon/10.1002/vms3.762