Ournal of Pplied Cience and Nvironmental Anagement

The aim of the study was to isolate Salmonella from fresh cabbage and spinach vegetables, determine antimicrobial resistance and biofilm formation of the isolates. Spinach and cabbage farm vegetables were found to harbour Salmonella. A total of eighty-two Salmonella isolates were recovered from both vegetables and subjected to antimicrobial reactions. Salmonella isolate showed sensitivity against the aminoglycoside and quinolones. Isolates from cabbage showed ≥ 80% susceptibility to nalidixic acid and ciprofloxacin and an average of 72% susceptibility was exhibited against gentamicin and ofloxacin. Also, isolates from spinach vegetable demonstrated excellent sensitivity against chloramphenicol (94%), nalidixic acid (90%) and ofloxacin (82%). Variable resistant patterns was observed for tetracycline (58%: 47%), ampicillin (55.5%: 31.4%), erythromycin (58.1%: 62.7%), streptomycin (64.5%: 76.5%), cephalothin (35.5%: 39.2%) against isolates from cabbage and spinach respectively. The assessment of biofilm formation by Salmonella on microtitre plate showed that all Salmonella isolates were able to form biofilms. Isolates from cabbage were mainly strong producer 15(48.3%), while 11(35.5%) of the isolates were moderate producers and 6(16.1%) weak producer. On the other hand, 28(54.9%) of Salmonella isolates from spinach vegetable were moderate producer, 12(23.5%) weak producer and 11(21.5%) strong producer. The finding of this study shows that cabbage and spinach is potential host for the transmission of Salmonella to humans or other animals. The ability of the isolates to form biofilm reveals the potential of the isolates to persist on the vegetable and the pathogenic status of the isolates as well as ability to resist antimicrobial chemotherapy. © JASEM http://dx.doi.org/10.4314/jasem.v19i1.6 Introduction Fresh vegetables are fundamental components of the human diet and there is considerable evidence of the health and nutritional benefits associated with the consumption of fresh vegetables. This has led to significant rise in the demand of fresh produce, changes in life styles and major shifts in consumption trends (Abadias et al., 2008; Tang et al., 2012).Vegetables can become contaminated with microorganisms capable of causing human diseases while still on the fields (Mukherjee et al., 2006). Bacteria such as Clostridium botulinum, Bacillus cereus and Listeria monocytogenes capable of causing disease, are normal inhabitants of many soils, while Salmonella, Shigella, Escherichia coli and Campylobacter which reside in the intestinal tracts of humans and animals, are more likely to contaminate raw vegetables through contact with faeces, sewage, untreated irrigation water or surface water (Cliver, 1997; Speer, 1997). Fresh farm produce can be a vehicle for the transmission of bacterial, parasitic and viral pathogens capable of causing human illness. There is documented evidence of raw vegetables harbouring potential food-borne pathogens, which can become contaminated while growing or during harvesting, post-harvest, handling, or distribution (Mukherjee et al., 2006; Abadias et al., 2008). Bacterial pathogens continue to be a major contributor to produce-associated food-borne illnesses (Berger et al., 2010).The incidence and frequency of foodborne outbreaks caused by contaminated fresh vegetables is on the increase (De Roever, 1998; Wegener et al., 2003; Raufu et al., 2014). Salmonella is one of the pathogen most frequently linked to consumption of fruit and vegetables (Sivapalasingam et al., 2004). Several outbreaks of salmonellosis have been traced to contaminated fresh fruits and vegetables (Salleh et al., 2003; Berger et al., 2010). A wide spectrum of produce vehicles have been associated with Salmonella infections (Berger et al., 2010). The factors influencing the increase in salmonellosis due to vegetables are changes in agricultural practices, eating habits and increases in the worldwide commerce of fresh produce (Collins, 1997; Raufu et al., 2014). Reports has shown that fresh spinach grown in three Californian countries were the source of microbial contamination that led to food-borne outbreak affecting 26 US states which resulted in about 200 Biofilm formation of Salmonella species isolated 46 * 1 ISOKEN H. IGBINOSA cases of illness, including some of haemolytic uremic syndrome and resulted in three deaths (FDA, 2006; Abadias et al., 2008).The consumption of fresh fruit and vegetables might therefore pose a food safety risk because they are susceptible to contamination by faecal material on the farm (Mukherjee et al., 2004; Abadias et al., 2008). In present times, bacterial biofilms have been more linked to food safety issues globally. Biofilm is formed when bacterial cells attach to one another and stick on to a contact surface. Biofilm are hazardous as they can become a persistence source of contamination (Houdt and Michiels, 2010). The existence of pathogenic organisms in biofilms has been linked to foodborne illness outbreaks in cantaloupe melons, apples, and leafy greens (Annous et al., 2009). They are capable of adhering to plant surfaces and forcefully infect the plants interior (Schikora et al., 2012). Bacteria living within biofilms can exhibit 1000 times more resistance to antimicrobials than their planktonic peers. The close proximity of these bacteria within biofilm community enhances gene transfer; resulting in increased genetic diversity of antimicrobial resistance. Once biofilm forms on fresh produce surface, they not only can cause cross contamination to other food produce or processing equipment surfaces in industry, they also result in a potent health hazard to consumers (Tang et