Detection, Serotyping and Antimicrobial Resistance Pattern of Salmonella from Chicken slaughter slabs in Jos, North-Central Nigeria

Idowu Fagbamila1*, Adaobi Okeke2, Micheal Dashen2, Patricia Lar2, Sati Ngulukun1, Benshak Audu1, David Ehizibolo1, Paul Ankeli1, Pam Luka1, Maryam Muhammad1

1National Veterinary Research Institute, Vom, Nigeria. 2University of Jos, Nigeria.

Editor | Muhammad Abubakar, National Veterinary Laboratories, Park Road, Islamabad, Pakistan.

Received | February 24, 2017; Accepted | March 25, 2017; Published | March 29, 2017

*Correspondence |Idowu Fagbamila, National Veterinary Research Institute, Vom, Nigeria: Email: [email protected]

Citation | Fagbamila I, Okeke A, Dashen M, Lar P, Ngulukun S, Audu B, Ehizibolo D, Ankeli P, Luka P, Muhammad M (2017). Detection, serotyping and antimicrobial resistance pattern of salmonella from chicken slaughter slabs in Jos, North-Central Nigeria. Veterinary Sciences: Research and Reviews, 3(1): 25-33.

DOI | http://dx.doi.org/10.17582/journal.vsrr/2017.3.1.25.33

Keyword: Salmonella, Serotype, Resistance Pattern, Slaughter-slabs, Nigeria

Introduction

Salmonella infections in poultry are an important source of clinical and food borne disease of both animals and humans. Host-adapted poultry Salmonellae (Salmonella Pullorum and Salmonella Gallinarum) are responsible for severe systemic diseases in developing countries relative to countries with testing and eradication programmes (Pomeroy and Nagaraja, 1999; Snoeyenbos, 1991). Numerous serotypes of non-host adapted paratyphoid Salmonellae are often carried sub-clinically by poultry birds and thereby contaminating poultry and poultry products (Malorny et. al., 2003). Salmonellosis is one of the most common causes of food borne diarrheal disease worldwide and remains a major public health problem in many parts of the world (Riyaz-Ul-Hassan et al., 2004). Majority of the over 2650 recognized serotypes of Salmonella infect both human and animals worldwide with signs ranging from fever, abdominal cramps, vomiting, diarrhoea and death (Guibourdenche et al., 2010; Scallan et al., 2011; Issenhuth-Jeanjean et al., 2014).

The importance of food as a vehicle for the transmission of salmonellosis has been well documented (Matsuoka et al., 2004; Mullner et al., 2009; Dallal et al., 2010). A variety of foods have been implicated as vehicles transmitting salmonellosis to humans, including poultry, beef, pork, eggs, milk, cheese, fish, shellfish, fresh fruit and juice, and vegetables (Espi et al., 2005; Mazurek et al., 2004; Varma et al., 2005; Acha and Szyfres, 2001). However, poultry, egg, meat and dairy products continue to be the most common food vehicles of Salmonella infection (Rodrigue et al., 1990; D’Aoust, 1994; Llewellyn et al., 1998). Bacterial organisms generally are a major safety concern to the meat industry where contamination can occur at multiple stage along the food processing chain either at the pre-harvest, harvest or post-harvest stages. Again, food handlers may re-contaminate a thoroughly processed or cooked meat meant for consumption (Oscar, 2013; Wagner, 2013). This is especially common in most developing countries where dressed carcasses are transported openly or kept in contaminated containers.

Despite the occurrence of Salmonella in raw and cooked poultry and poultry products as well as in beef meat in Nigeria (Mbata, 2005; Smith et al., 2012; Tafida et al., 2013), very little information is available on the occurrence of Salmonella at poultry slaughter plants/houses even when it has been shown to be the main source of cross-contamination in many parts of the world (Wang et al., 2013). This is even compounded by the fact that very few of those slaughter plants/houses exist and consumers are forced to sometimes purchase live birds from them for slaughter. These birds are processed in an open environment at a slaughter slab in the market with poor sanitary and hygienic conditions. It is not uncommon to see faecal contamination of carcasses from the gut during slaughter and processing of these birds. This may lead to contamination of the processing line, equipment and subsequently cross-contamination of non-infected birds and humans (Olsen et al., 2003; Rostagno et al., 2006).

This study was designed to determine the occurrence of Salmonella species in water used for de-feathering (Hot water) and washing/rinsing (carcass-rinse) as well as in the intestinal contents of the birds and processing contact-surfaces (table swabs) used in processing poultry carcasses at three poultry slaughter slabs in Jos. We also try to identify the antimicrobial resistant pattern of the isolates from these different sources.

Materials and Methods

Study area

The study was carried out at three poultry slaughter slabs in Jos, Plateau State, North Central Nigeria. The city has a population of over 900,000 and a tropical climate with near temperate temperature in the northern part of the state. It lies within the guinea savannah vegetation zones of Nigeria with an average annual rainfall of 1200mm. The weather and rocky terrain are very conducive for livestock and arable crop production.

Sampling procedure

Sampling was carried out at intervals using a convenience sampling method from three live bird markets in Jos Metropolis: Terminus and Chobe Markets in Jos-North local government area (LGA), and Bukuru market in Jos-South LGA.

Eighty-four (84) samples were screened for Salmonella from four different matrices using convenience sampling and on the willingness of butchers to collaborate. Sampling was carried out three times at two months intervals. These include 21 de-feathering (Hot) water and 21 washing/rinsing water (Carcass-rinse), 21 Processing contact-surfaces (table swabs) and 21 intestinal samples (Figure 1). All samples were collected after the de-feathering, carcass-rinse and contact of birds with table. Both environmental and water temperatures (de-feathering and carcass-rinse) were read using a thermometer. Samples were collected into sterile universal bottles, labelled, placed on ice and immediately transported to the laboratory for analysis.

Isolation and identification of Salmonellae

A modification of the Salmonella culture method ISO 6579: 2002 (Annex D) was used. Briefly, samples were pre-enriched in buffered peptone water in a 1:10 sample to broth ratio at 370C for 24hrs. 0.1ml of the pre-enriched broth was inoculated into 10ml of Rappaport-Vassiliadis (RV) broth for enrichment and incubated for 24 hours at 370C. A loop full Cultures from RV was then plated simultaneously onto Brilliance Salmonella Agar (BSA) and Xylose Lysine Desoxycholate (XLD) medium and incubated at 370C for 24 hours (ISO, 2002). Suspected isolates were identified by the colour and morphology of the colonies on the agar plates.

Biochemical test was carried out as described by (Raafat, et al., 2011). All isolates that gave the following reactions: indole negative, urease negative, citrate positive, motile in motility medium, oxidase negative, nitrate positive, lysine decarboxylase positive, Voges-Proskauer negative, ferment glucose, mannitol, dulcitol, and maltose but fail to ferment lactose, sucrose, inositol and raffinose were considered to belong to the genus Salmonella.

Evaluation of the resistant patterns of the isolates to antimicrobial agents

The resistant patterns of isolates to 10 antibiotics were determined using the agar-diffusion method (Khan et al., 2006). Five colonies were inoculated into a tube containing Tryptose soy broth (Difco, USA) and incubated overnight at 370C. Standardization of the inoculums was performed by diluting the broth cultures until turbidity matched the 0.5 McFarland standards. A sterile cotton swab was dipped into the standardized suspension, drained and used for inoculating 20 ml of Mueller-Hinton agar (Oxoid, UK) on a 100-mm disposable plate (Sterlin, UK). The inoculated plates were air dried, and antibiotic discs (Oxoid, UK) were placed on the agar using a disc dispenser. The following antibiotics were used: Sulphamethoxazole/ Trimethroprim (30 μg), Penicillin (10 μg), Chloramphenicol (30 μg), Gentamicin (10 μg), Erythromycin (5μg), Streptomycin (10 μg), Methicillin (10 μg), Oxacillin (5 μg), Cloxacillin (5 μg) and Nalidixic acid (30 μg). The plates were incubated aerobically at 370C for 18 to 24 h. The diameter of the zones of inhibition were measured and the sensitivity and resistance determined by the criteria of the Clinical and Laboratory Standards Institute (CLSI, 2006). Escherichia coli ATCC 25922 was used as the control strain. The formula: MAR index = (Number of antibiotics per isolate)/ (Total number of antibiotics tested) was used to calculate the multiple antibiotic resistance index (Wang et al., 2013, Adzitey et al., 2012) and all isolates that were classified as intermediate on the basis of inhibition zones were considered as sensitive for MAR index (Singh et al., 2010).

Detection of InvA gene using polymerase chain reaction (PCR) test

Three millilitres of each broth culture was centrifuged at 2,700 × g for 10 minutes to pellet the cells. The cells were washed twice with 1 ml PBS pH 7.4 and suspended in 200μl PBS pH 7.4. The genomic DNA was extracted using DNeasy® Blood and Tissue Kit (Qiagen, Netherlands) according to the manufacturer’s instructions. The extracted DNA samples were stored at -20°C until used for PCR. Amplification of invA gene in Salmonella isolates was performed by using a primer pair specific to that locus as described by Rahn et al. (1992). The PCR was carried out in a 25μl comprising 5μl of the extracted DNA, 3.0μl of 10 × buffer (Fermentas®), 1.0μl of 10 mM dNTPs mix (Fermentas®), 1.0μl of 25 mM MgCl2, 1.25μl of 10 μM primers, and 2.5U of Taq Polymerase (Fermentas®). PCR amplification was performed in a GeneAmp® 9700 PCR System (Applied Biosystems) with initial denaturation at 95°C for 2 minutes followed by 35 cycles of denaturation at 95°C for 30 seconds; annealing at 53°C for 30 seconds, extension at 72°C for 1 min and final extension at 72°C for 7 minutes.

Ten microlitres of the PCR product was electrophoresed in a 1.5% agarose gel stained using 5μl of 10 mg/ml ethidium bromide at 100 V for 50 minutes. A 100bp DNA marker (Fementas®) was used as molecular size marker. The resulting gel was examined under a U.V transilluminator and DNA amplifications documented using a Gel Documentation System (Synegene®).

Serotyping of Salmonella isolates

Suspected Salmonella isolates were freeze-dried and shipped to the OIE Reference laboratory for

Five (23.8%) out of the 21 intestinal samples, 4(19.1%) out of the 21 table swab, 4 (19.1%) out of 21 de-feathering water sample and 4 (19.1%) out of 21 carcass-rinse sample yielded Salmonella. The overall isolation frequency of Salmonella was 17 (20.2%) out of the 84 samples tested (Table 1b).

Identification and characterization of isolates

All the eighteen (18) suspect isolates identified by the conventional biochemical test where further confirmed by polymerase chain reaction (PCR) and all except one suspected isolates tested positive for the genus Salmonella.

Antimicrobial resistance of Salmonella isolates

Sixteen (94.1%) of the 17 isolates were susceptible to Gentamicin, 15 (88.2%) to Chloramphenicol and Streptomycin, 11(64.7%) to Sulphamethoxazole/Trimethroprim, 9(52.9%) to Nalidixic acid and 2(11.8%) to cloxacillin. All (100%) isolates were resistant to Oxacillin, Erythromycin, Penicillin and Methicillin (Table 2). The resistance pattern shows that all the serotypes are resistant to at least four (4) antibiotics with S. Llandoff from hot water being resistant to all the antibiotics (Table 3).

All the 18 Salmonella suspects screened for invA gene detection using PCR gave a 284bp DNA fragment with exception of lane 11 which confirms that the isolates were Salmonella (Figure 2).

Salmonella Serotyping

The seventeen isolates serotyped were identified as Salmonella Llandoff (10 isolates), S. Kentucky (3 isolates), S. Schwarzengrund (2 isolates) and S. Havana (2 isolates).

Table 1a: PCR primers used

There are very few poultry slaughtering facilities in Nigeria and therefore live-birds especially the local chicken from different sources are sold and processed at the live-bird markets. On the other hand, some people patronize these live-bird markets because of cultural, religious or culinary reasons. In live-bird markets, consumers buy and take it to separate handlers for slaughtering at an open environment (slaughtering slabs). Consumers wait for their birds to be processed and delivered to them immediately thus making inspection of such processed carcasses difficult. In the United States, these LBM are exempted from Food safety and inspection service pathogen reduction performance standards (USDA, 2013). There is however, increased concern that such markets could be heavily contaminated with S. enterica (Imanishi, et al., 2014).

The ambient temperature, blood and moisture contents in these samples favour the multiplication and thriving of bacterial organisms. Occurrence of Salmonella in de-feathering (hot) water 4(19.1%) proves that Salmonella has become a big challenge in the processing of poultry meat especially in developing countries like Nigeria. Salmonella which was believed to grow at temperature of between 370C-420C was isolated in this study from de-feathering water with temperature between 480C-520C. Heat-processing should be sufficient to destroy any Salmonellae or reduce its incidence in poultry carcasses to an acceptable level, but may fail to do so, especially when temperature is inadequate or opportunities exist for recontamination of the finished product. From this study, it appears Salmonella may have become “acclimatized’’ to its environment and therefore, can survive or adapt to these temperature ranges. We were however not able to isolate Salmonella from de-feathering (hot) water at Bukuru market (Table 1a) probably due to the high temperatures of the water which might not be favourable for the survival of the organism. Salmonella was isolated from carcass-rinse 5(23.8%) used for washing/rinsing carcasses after de-feathering chicken. This is in agreement with Adeyanju and Ishola (2014) who reported cross contamination of poultry meat within the processing chain due to physical contact. Salmonella in our study may be as a result of cross-contamination from hot water or spillage of the gut contents as reported by (Orji et al., 2005) in Awka, Nigeria. Salmonella isolated from processing surfaces was low (19.1%) as compared to a prevalence of 25% and 23.5% reported in China and Malaysia (Wang et al., 2013; Adzitey et al., 2012) respectively. Isolation of Salmonella from the processing-surfaces could be as a result of contaminated carcass-rinse or evisceration of the gut contents, since the table is hardly washed or kept clean after every butchering. Our finding was supported by (Orji et al., 2005) who isolated Salmonella (12.5%) from poultry droppings in Awka south east Nigeria and some of this birds eventually get to slaughter slabs. The highest Salmonella isolates (23.8%) was obtained from the intestinal contents and carcass-rinse. This was however expected for the intestinal content due to their high microbial content and physical contact. Interestingly, the high incidence in carcass-rinse raises a lot of public health concerns.

Four different serotypes of Salmonella were identified from the isolates. S. Llandoff predominated with 11(74.6%), followed by S. Kentucky 3 (16.7%), S. Schwarzengrund 2(11.1%) and S. Havana 2(11.1%). The serotypes identified in our study differ from the ones reported by (Orji et al., 2005) in Awka, Nigeria. The difference can be due to study area and design. For public health concern, S. Schwarzengrund isolated in this study was earlier reported by Imanishi et al. (2014) as the cause of outbreak and infant death in the USA in 2007. The high isolation rate recorded in Terminus LBM may not be unconnected to the fact that it is the most active (high slaughter rate per day) of the 3 LBM markets examined due to the population density and demand.

All (100%) the isolates were resistant to at least four antibiotics namely Methicillin, Penicillin, Erythromycin and Oxacillin. Our findings were similar to that observed by (Obi and Ike, 2015) in Nsukka, Nigeria from an intensively reared and backyard poultry suggesting the growing threat of antibiotics on farms to the detriment of public health. The mechanism for bacterial antimicrobial resistance varies (Bennett, 2008) and given that an isolate (S. Llandoff) from hot water was resistant to all the antibiotics tested

Table 3: Multiple antibiotic resistant patterns of Salmonella isolates

(Table 3) is worrisome. The multiple drug resistance of all the isolates raises serious public health concern because they could pose considerable health risk to both consumers and handlers of poultry meat product. This study shows six (6) different resistant patterns with MAR index of 1 for one of the isolate (Table 3). The resistance to these entire antibiotics which are used both in humans and animals calls for serious public health concern. The percentage antibiotic resistance ranges from 5.6% (Gentamicin) to 100% (Methicillin, Penicillin, Erythromycin and Oxacillin) while the overall percentage serotype resistance to the 10 antibiotics is 62.4% (Table 2). Two of the ten S. Llandoff showed multiple antibiotic resistance indexes of 0.9 and 1.0 respectively.

Generally, the occurrence of Salmonella as a contaminant of poultry slaughter slabs 17(20.2%) is higher than the 12.5% that was obtained from chicken droppings in Nsukka but similar to the contamination of 21.0% of chicken meats in the province of Vietnam (Tran et al., 2005). Similarly, Wang et al. (2013) in China also reported a 22.1% rate of contamination by Salmonella and 22.6% reported by Adeyanju and Ishola (2014) in poultry processing plant in Ibadan, Nigeria.

In conclusion, our study demonstrated a high occurrence of Salmonella from four different matrices at three live-bird markets. The identification of Four different serotypes (S. Llandoff, S. Kentucky, S. Schwarzengrund, S. Havana) from 17 isolates that showed 7 different antibiotic resistant patterns against 10 antibiotics with the MAR index ranging from 0.4 to 1.0 suggest that lack of appropriate control measure and use of drugs is a potential “superbug” in the making. Poor infrastructure, lack of well-equipped poultry slaughter houses, lack or inadequate water supply at these markets hamper the ability of handlers to maintain good sanitary and hygiene conditions of carcass, environment and themselves. However, the unhygienic practices carried out at the Live-bird markets should be checked by the regulatory bodies responsible for maintaining good sanitary and hygienic conditions.

Acknowledgements

This project was supported by the National Veterinary Research Institute, Vom. We are also very grateful to Dr. Antonella Ricci and all the staff of the OIE reference laboratory for Salmonellosis, Padova Italy for serotyping these isolates.

Authors contribution

The study was conceptualized by DMM, AIO and IOF. IOF, PIA, BJA, SSN collected and analysed the samples while OIF, PDL, AIO, DOE wrote the draft manuscript. The project was supervised by MM, and LPM supervise the study and all authors read and approved the final draft for submission.

Conflict of interest

Authors declare no conflict of interest.

References

• • Acha, P.N. and Szyfres, B. 2001. Salmonella. In B. Szyfres (Ed.). Zoonoses and communicable diseases common man and animal. PAHO Science and Technical Publication. No. 5
• • Adeyanju, G.T. and Ishola, O. 2014. Salmonella and Escherichia coli contamination of poultry meat from a processing plant and retail market in Ibadan, Oyo State, Nigeria. Springerplus. 3: 139. https://doi.org/10.1186/2193-1801-3-139
• • Adzitey, F., Rusul, G. and N. Huda. 2012. Prevalence and antibiotic resistance of Salmonella serovars in ducks, duck rearing and processing environments in Penang, Malaysia. Food Res. Int. 145: 947-952. https://doi.org/10.1016/j.foodres.2011.02.051
• • Akhatar, F., Hussain, I., Khar, A. and Rahman, S.U. 2009. Prevalence and antibiogram studies of Salmonella enteridis isolated from human and poultry sources. Pak. Vet. J. ISSN: 0253-8318.
• • Amini, K., Zahraei, T.S., Gholamreza, N., Reza, R., Javid, A. and Shahrnaz, B.A. 2010. Molecular detection of invA and spv virulence genes in Salmonella Enteritidis isolated from human and animals in Iran. Afr. J. Microbiol. Res. 4: 2202-2210.
• • Bennett, P.M. 2008. Plasmid encoded antibiotic resistance: acquisition and transfer of antibiotic resistance genes in bacteria. Br J Pharm, 153:S347-357.
• • Clinical Laboratory Standards Institute (CLSI). (2006). Performance Standards for Antimicrobial Susceptibility Testing: Sixteenth informational supplement. CLSI document M100-S16, CLSI, Wayne, PA, USA.
• • D’Aoust J.Y. 1994. Salmonella in the international food trade. Int. J. Food Microbiol. 24:11–31. https://doi.org/10.1016/0168-1605(94)90103-1
• • Dallal, M.M.S., Doyle, M.P., Rezadehbashi, M., Dabiri, H., Sanaei, M. and Modarresi, S. 2010. Prevalence and antimicrobial resistance profiles of Salmonella serotypes, Campylobacter and Yersinia spp. isolated from retail chicken and beef, Tehran, Iran. Food Control. 21: 388-392. https://doi.org/10.1016/j.foodcont.2009.06.001
• • De jong, B. and Ekdahl, K. 2006. Human salmonellosis in travelers is highly correlated to the prevalence of Salmonella in laying hen flocks. European Surveillance. 11: E060706.1.
• • European Food Safety Authority (EFSA). 2009. The community summary report on trends and sources of zoonoses and zoonotic agents in the European Union in 2007. Eur. Food Saf. Authority J. 223: 1-217.
• • Espi, E., De Valk, H., Vaillant, V., Quelquejeu, N., Le Querrec, F. and Wei, F.X. 2005. An outbreak of multidrug-resistant Salmonella enterica serotype Newport infections linked to the consumption of imported horse meat in France. Epidemiol. Infect. 133: 373–376. https://doi.org/10.1017/S0950268804003449
• • Fagbamila, I.O., Barco, L., Mancin, M., Kwaga, J., Ngulukun, S.S., Zavagnin, P., Lettini, A.A., Lorenzetto, M., Abdu, P.A., Kabir, J., Umoh, J., Ricci, A. and Muhammad, M. 2017. Salmonella serovars and their distribution in Nigerian commercial chicken layer farms. PLoS ONE. 12(3): e0173097. https://doi.org/10.1371/journal.pone.0173097
• • Food and Agriculture Organization (FAO). 2009. Fowl typhoid and pullorum disease. Food and agriculture organization of the United Nations manual for the recognition of exotic diseases. www.cfsph.iastate.edu/factsheets/pdfs/fowl_typhoid.pdf
• • Guibourdenche, M., Roggentin, P., Mikoletit, M., Fields, P.I., Bockemuhl, J., Grimont, P.A. D., and Weill, F.X. 2010. Supplement 2003-2007 (No. 47) to the White-Kauffmann-Le Minor scheme. Res. Microbiol. 161: 26-29. https://doi.org/10.1016/j.resmic.2009.10.002
• • Imanishi, M., Anderson, T.C., Routh, J., Brown, C., Conidi, G., Glenn, L., Reddy, V., Waechter, H., Malavet, M., Nyaku, M., Bohm, S., Bidol, S., Arends, K., Saupe, A., Higa, J., Nguyen, T.A., Pringle, J., Behravesh, C. B. and Bosch, S. 2014. Salmonellosis and meat purchased at live-bird and animal-slaughter markets, United States, 2007-2012. Emerg. Infect. Dis. 20 (1): 167-169. https://doi.org/10.3201/eid2001.131179
• • Issenhuth-Jeanjean, S., Roggentin, P., Mikoleit, M., Guibourdenche, M., Pinna, E, Nair, S., Fields, P.I. and Weill, F.X. 2014. Supplement 2008-2010 (no. 48) to the White-Kauffmann-Le Minor scheme. Res. Microbiol. 165: 526-530. https://doi.org/10.1016/j.resmic.2014.07.004
• • ISO, 2002. ISO 6579, 2002. Detection of Salmonella spp. in animal faeces and in samples of the primary production stage, Annex D. Int. Organ. Stand.
• • Khan, A.A., Cheng, C.M., Khanh, T.V., Summage-West, C., Nawaz, M.S. and Khan, S.A. 2006. Characterization of class 1 integron resistance gene cassettes in Salmonella enterica serovars Oslo and Bareily from imported seafood. J. Antimicrob. Chemother. 58: 1308–1310. https://doi.org/10.1093/jac/dkl416
• • Llewellyn, L.J., Evans M.R. and Paimer, S.R. 1998. Use of sequential case control studies to investigate a community Salmonella outbreak in Wales. J. Epidemiol. Community Health. 52: 272–276. https://doi.org/10.1136/jech.52.4.272
• • Malorny B., Hoorfar J., Bunge, C. and Helmuth R. 2003. Multicentre validation of the analytical accuracy of Salmonella PCR: towards an international standard. Appl. Environ. Microbiol. 69: 290-296. https://doi.org/10.1128/AEM.69.1.290-296.2003
• • Mamman, P.H., Kazeem, H.M., Raji, M.A., Nok, A.J. and Kwaga, J K.P. 2014.Isolation and characterization of Salmonella Gallinarum from outbreaks of fowl typhoid in Kaduna State, Nigeria. Int. J. Public Health Epidemiol. 3(10):082-088.
• • Matsuoka, D. M., Costa, S. F., Mangini, C. 2004. A nosocornial outbreak of Salmonella Enteritidis associated with lyophilized enteral nutrition. J. Hosp. infect. 58: 122-127. https://doi.org/10.1016/j.jhin.2004.05.003
• • Mazurek, J., Salehi, E., Propes, D., Holt, J., Bannerman, T., Nicholson, L. M., Bundesen, M., Duffy, R. and Moolenaar, R.L. 2004. A multistate outbreak of Salmonella enterica serotype Typhimurium infection linked to raw milk consumption – Ohio, 2003. J. Food Prot. 67: 2165–2170. https://doi.org/10.4315/0362-028X-67.10.2165
• • Mbata, I.T. 2005. Poultry meat pathogens and its control. Online j. food saf. 7: 20-28. www.internetjfs.org/articles/ijfsv7-4pdf
• • Mullner, P., Jones, G., Noble, A., Spencer, S.E., Hathaway, S. and French, N.P. 2009. Source attribution of food-borne zoonoses in New Zealand: a modified Hald model. Risk Analysis. 29: 970-984. https://doi.org/10.1111/j.1539-6924.2009.01224.x
• • Obi, O.J., and Ike, A.C. 2015. Prevalence and Antibiogram Profile of Salmonellae in Intensively Reared and Backyard Chickens in Nsukka Area, Nigeria. Nig J Biotech, 30: 18-25. DOI: http://dx.doi.org/10.4314/njb.v30i2.3
• • Olsen, S.J., Bleasdale. S.C. and Magnano, A.R. 2003. Outbreaks of typhoid fever in the United States. 1960–99. Epidemiol. Infect. 130: 13-21. https://doi.org/10.1017/S0950268802007598
• • Orji, M.U., Onuigbo, H.C., and Mbata T.I. 2005. Isolation of Salmonella from poultry droppings and other environmental sources in Awka, Nigeria. Int J Infect Dis. 9: 86-89.
• • Oscar, T.P. 2013. Initial contamination of chicken parts with salmonella at retail and cross contamination of cooked chicken with salmonella from raw chicken during meal preparation. J. food prot. 7:33-39. https://doi.org/10.4315/0362-028X.JFP-12-224
• • Pomeroy, B.S. and Nagaraja K.V. 1999. Fowl typhoid. In: Diseases of poultry, 9th ed. Calnek, B.W., Barnes, H.J., Beard, C.W., Reid, W.M and Yoder, H.W Jr., eds. Iowa State Press, Ames, Iowa.73-86.
• • Raafat, H., Sohaila, F.H., Ashraf, M.E., Moemen, A.M. and Khalid, I.E. 2011. Detection and identification of Salmonella species in minced beef and chicken meats in Assiut City. Vet. World. 4:(1): 5-11.
• • Rahn, K., De Grandis, S.A., Clarke, R.C., McEwen, S.A., Gala´n, J.E., Ginocchio, C., Curtiss, R., III and Gyles, C.L. 1992. Amplification of an invA gene sequence of Salmonella typhimurium by polymerase chain reaction as a specific method of detection of Salmonella. Mol. Cell. Probes. 6: 271–279. https://doi.org/10.1016/0890-8508(92)90002-F
• • Riyaz-UI-Hassan, S., Verma, V. and Qazi, G.N. 2004. Rapid detection of Salmonella PCR primers using various intestinal bacterial species. Letter Appl. Microbiol. 37: 463.
• • Rodrigue, D.C., Tauxe, R.V. and Rowe, B. 1990. International increase in Salmonella enteritidis: A new pandemic? Epidemiol. Infect. 105: 21–27. https://doi.org/10.1017/S0950268800047609
• • Rostagno, M.H., Wesley, I.V., Trampel, D.W., and Hurd, H.S. 2006. Salmonella prevalence in market-age turkeys on farm and at slaughter. Poult. Sci. 85: 1838-1842. https://doi.org/10.1093/ps/85.10.1838
• • Santillana Farakos, S.M., Frank, J.F., and Schaffner, D.W. 2013. Modelling the influence of temperature, water activity and water mobility on the persistence of Salmonella in low-moisture foods. Int J Food Microbiol, 166: 280-293
• • Scallan, E., Hoekstra, R.M., Angulo, F.J., Tauxe, R.V., Widdowson, M.A. and Roy, S.L. 2011. Foodborne illness acquired in the United States-major pathogens. Emerg. Infect. Dis. 17 (1): 7-15. https://doi.org/10.3201/eid1701.P21101
• • Singh, S., Yadav, A.S., Singh, S.M., and Bharti, P. 2010. Prevalence of Salmonella in chicken eggs collected from poultry farms and marketing channels and their antimicrobial resistance. Res. Int. 43: 2027-2030. https://doi.org/10.1016/j.foodres.2010.06.001
• • Stella, S., B. Opere, M. Fowora1, A. Aderohunmu, R. Ibrahim, E. Omonigbehin, M. Bamidele and A. Adeneye. 2012. Molecular characterization of salmonella sppdirectly from snack and food commonly sold in Lagos, Nigeria. Southeast Asian J. Trop. Med. Public Health. 43(3): 718-723.
• • Smith, S., Opere, B., Fowora, M., Aderohunmu, A., Ibrahim, R., Omonigbehin, E., Bamidele, M., and Adeneye, A. 2012. Molecular characterization of salmonella sppdirectly from snack and food commonly sold in Lagos, Nigeria. Southeast Asian Journal of Tropical Medicine and Public Health. 43: 718-723.
• • Snoeyenbos, G.H. 1991. Pullorum disease. In: Diseases of poultry, 9th ed. Calnek, B.W., Barnes, H.J., Beard, C.W., Reid, W.M and Yoder, H.W Jr., eds. Iowa State University.
• • Sultana k., Bushra, M.A. and Nafisa I. 1995. Evaluation of antibiotic resistance in clinical isolates of Salmonella typhi from Islamalad. Pak. Zool. 27:(2): 185 – 187.
• • Tafida, S.Y., Kabir, J., Kwaga, J.K.P., Bello, M., Umoh, V.J., Yakubu, S.E., Nok, A.J., and Hendriksen, R. 2013. Occurrence of Salmonella in retail beef and related meat products in Zaria, Nigeria. Food Control. 32: 119-124. https://doi.org/10.1016/j.foodcont.2012.11.005
• • Tran, T.P., Ly, T.L.K., Natsue, O., Nguyen, T.T, Alexandre, T.O., Masato, A. and Hideki, H. 2005. Research Note: Contamination of Salmonella in retail meats and shrimps in the Mekong Delta, Vietnam. J. Food Prot. 68: (5): 1077–1080. https://doi.org/10.4315/0362-028X-68.5.1077
• • United State Department of Agriculture, Food Safety and Inspection Service (USDA). 2013. New performance standards for Salmonella and Campylobacter in young chicken and turkey slaughter establishments: response to comments and announcement of implementation schedule. Fed Reg. 2011; 76: 15282-15290 (cited 2013 July 31). University Press, Ames, Iowa. 73-86. http://www.gpo.gov/fdsys/pkg/FR-2011-03-21/pdf/2011-6585.pdf
• • Varma, J.K., Greene, K.D., Ovitt, J., Barrett, T.J., Medalla, F. and Angulo, F.J. 2005. Hospitalization and antimicrobial resistance in Salmonella outbreaks, 1984-2002. Emerg. Infect. Dis. 11: 943-946. https://doi.org/10.3201/eid1106.041231
• • Wagner, A.B., Jr. 2013. Bacterial food poisoning. 2013. http:// generalhealthtopics.com/bacterial-food-poisoning-330. html. Retrieved 05th Nov. 11.2013.
• • Wang, H., Ye, K., Wei, X., Cao, J., Xu, X., and Zhou, G. 2013. Occurrence, antimicrobial resistance and biofilm formation of Salmonella isolates from a chicken slaughter plant in China. Food Control. 33: 378-384. https://doi.org/10.1016/j.foodcont.2013.03.030
• • WHO. World Health Organization. 2005. Drug-Resistant Salmonella. Fact sheet no. 139.
• • Geneva, Switzerland. http://www.who.int/mediacentre/factsheets/fs139/en.
• • Yang, B., Qu, D., Zhang, X., Shen, J.L., Cui, S. H., Shi, Y. 2010. Prevalence and characterization of Salmonella serovars in retail meat and marketplace in Shanxi, China. Int. J. Food Microbiol. 141: 63-72. https://doi.org/10.1016/j.ijfoodmicro.2010.04.015