**5. Plant extract**

336 Salmonella – A Dangerous Foodborne Pathogen

*Salmonella* serotypes (James et al., 2000; Phebus et al., 1997; Whyte et al., 2003). Following the published report by Porto-Fett et al., 2010, the fermentation and drying and/or high pressure processing of contaminated dry sausage or pork are effective for inactivating *Salmonella* spp. High-pressure treatment of milk is considered to be the most promising alternative to traditional thermal treatments. Metrick et al., (1989) indicated that the pressure treatments of 310 and 379MPa/15 min at ambient temperature were required for a 3-log

The first reports on antibiotic resistant *Salmonella* had been indicated since 1960s and describe mainly case with monoresistance strain (Helmuth, 2000). In the late 1980s, the appearance multiple resistances against ampicillin, chloramphenicol, streptomycin, sulfonamides and tetracycline were found in serovar *Thyphimurium* definitive type 104 (DT 104) (Montville & Matthews, 2005). The main mechanism of bacteria exhibit resistance to antimicrobial agents can be due to many factors including drug inactivation, reduced drug accumulation, alteration of metabolic pathway and target site (Barbosa & Levy, 2000; Schwarz & Chaslus-Dancla, 2001). Much of the resistance to penicillins and cephalosporins by *Salmonella* spp. is attributable to the acquired ability of the strains to produce β-lactamase that can degrade the chemical structure of the antimicrobial agents

In recent years, the prevalence of multidrug resistant *Salmonella* in foods has been reported in many parts of the world. Several clinical treatment failures with fluoroquinolones (such as ciprofloxacin) in cases of *S. typhi* showed in Europe, Asia, and Africa (Butt et al., 2003; Nkemngu et al., 2005). Shirakawa et al. (2006) claims that the resistance to nalidixic acid and decreased susceptibility to fluoroquinolone in the *S. enterica* serovar *Typhi* isolated in Katmandu, Nepal, in 2003 were completely correlated to the mutation at codon 83 of gyrA. Most antimicrobial-resistant *Salmonella* infections are acquired from eating contaminated foods of animal origin. During 2000-2006 in Taiwan, it was found that 30.5% of the raw chicken meat was contaminated with multidrug resistant *S. enterica* serovar *Schwarzengrund* (Chen et al., 2011). Among the 88 *Salmonella* isolated from 300 meat products (raw beef, chicken meat and street foods) in Kuala Lumpur, the highest resistance was to tetracycline (73.8%), followed by sulfonamide (63.6%), streptomycin (57.9%), nalidixic acid (44.3%), trimethoprim sulfamethoxazole (19.3%), ampicillin (17.0%), chloramphenicol (10.2%) (Thong & Modarressi, 2011). The most antimicrobial resistance *S. enteritidis* isolates from South of Brazil reported by de Oliveir et al. (2005) was found in poultry related samples, where all strains were resistant to at least

The prevalence of extraintestinal *salmonella* infections caused by antibiotic resistant *Salmonella* spp. in several geographic areas of the world is increasing. Pokharel et al. (2006) demonstrated a 5% prevalence of multidrug resistance among *S. enterica* at a tertiary care hospital in Kathmandu, Nepal, with a higher rate of multidrug resistance among *S. paratyphi A* (7%) compared to *S. typhi* (3%). Rotimi et al. (2008) reported the serious problem of drug resistance in *Salmonella* spp. in Kuwait and United Arab Emirates that the non-typhoidal *Salmonella* spp. isolates from fecal samples of patients had 5-fold rise in resistant to

cefotaxime and ceftriaxone compared with reported earlier.

reduction in colony forming units (cfu) of *S. seftenberg* 775W.

**4. Antibiotic resistance** *Salmonella*

(Bush, 2003).

one antimicrobial agent.

Plant contain a variety of substance called "phytochemicals" (divided into two groups; primary and secondary metabolite), which are naturally occurring biochemicals in plants that give plants their color, flavor, smell and texture. Plant secondary metabolite differ from ubiquitous primary metabolite (e.g. carbohydrate, proteins, fats, nucleic acid) (Bako and Aguh, 2007), that have a scientifically proven effect on human health. The most important of these bioactive constituents of plants are alkaloids, tannins, flavonoids, anthraquinone, other phenolic compound and essential oil (Kisangau et al, 2007).

Extraction is the first important step for the recovery and purification of active ingredients of plant materials. Several extraction techniques and solvents are used for obtain antioxidant and antimicrobial extract from plant origin. The general techniques of medicinal plant extraction include maceration, percolation, hot continuous extraction (Soxhlet), solvent extraction, counter-current extraction, microwave-assisted extraction, ultrasound extraction (sonication), supercritical fluid extraction (Chen et al., 1992; Bicchi et al., 2000; Kaufmann and Christen, 2002). For solvent extraction method, polar solvents (such as organic acids), solvents of intermediate polarity (such as methanol, ethanol, acetone, and dichloromethane) and solvents of low polarity (such as hexane and chloroform) are used to extract plant secondary metabolites, which the extracts obtained from the same plant material with different solvent characteristics have distinct physical and biological properties. Lapornik, et al. (2005) reported that ethanol and methanol extracts of red and black currant contain twice more anthocyanins and polyphenols than water extracts, extracts made from grape marc had seven times higher values than water extracts. Among the five different Indian medical plants, methanol extract showed more antibacterial activity and moderate activity with aqueous, ethyl acetate and chloroform extract (Ashokkumar et al., 2010), while the morepolar solvent extracts (BuOH and water extracts) in Korean herbal medicines gave higher antioxidant activity than that of non-polar solvent extracts (hexane and EtOAC extracts) (Kang et al., 2003). Moreover, the chemical compound of extracts from particular plant species can vary according to the geographic origin, harvesting period and parts of the plant use. Nwokocha et al. (2011) found that all secondary metabolites analyzed were present in all tissues (leaf, stem, root and seed) studied but at different concentrations. A spatial and seasonal impact on the total phenolic content has been reported for *Poacynum henersonii*  collected at three sites in China (Hong et al., 2003).

Essential oils are a volatile liquid aromatic compound which extracted from plant cell. The cells are location in specific parts of the plant such as bark, flowers, leave, seed, peel and root. Table 1 shows the plant organ contains essential oil and their essential oil constitutes. Distillation (water distillation, water and steam distillation, steam distillation) is the most commonly used method for produces essential oils on the commercial basis (Rasooli, 2007). Some volatile oils cannot be distilled without decomposition are thus are usually obtained by expression (such as lemon oil or orange oil). The effect of diffrent distillation methods on oil content and composition of aromatic plants have been reported. The water-distillation of the rose-scented geranium (*Pelargonium* sp.) gave a higher oil yield (0.16–0.22%) than did water-steam-distillation (0.09–0.12%) or steam-distillation methods (0.06–0.18%) (Kiran et al., 2005). The oil of *Satureja rechingeri* Jamzad in full owering stage obtained by hydrodistillation, water- and steam-distillation and direct steam-distillation consisted of twenty, seventeen and twenty-two compounds, respectively, which the major constituents were carvacrol and p-cymene (Sedkon et al., 2007).

Inhibitory Effect of Plant Extracts on Salmonella spp. 339

antibacterial activity against all three *Salmonella* serotypes (*S. typhi* ATCC 19943, S*. paratyphi*

In India, Mahida & Mohan (2007) described that the methanol *Manilkara hexandra*, *Wrightia tomentora* and *Xanthium strumarium* extracts displayed MIC value of 2 mg/mL for *S. paratyphi* A whereas the methanol *Schrebera swietenoiides* and *Wrightia tomentora* showed MIC value of 4 mg/mL for *S. typhi*. The result studied by N'guessan et al. (2007) showed bactericidal effect of the aqueous extract of *Thonningia sanguinea* for all the multiple drug resistance *Salmonella* strains (*S. typhi*, *S. hadar* and *S. typhimurium)* and sensitive tested strains (*S. enteritidis*). The *S. typhimurium* strain was also found to be sensitive to extracts of *Acacia nilotica*, *Syzygium aromaticum* and *Cinnamum zeylanicum*, in Khan et al. (2009). The petroleum ether extract of *Pedalium murex* Linn exhibits the activity at 300-500 mg/disc against the *S. paratyphi A* and at 500 mg/disc against the *S. paratyphi B* (Nalini et al., 2011). Furthermore, the root of the *Euphorbia balsamifera* has high activity against the *S. typhimurium* when compared with the leaves and stems extracts (Kamba & Hassa, 2010). In contrast, the extract of eucalyptus from root, leave and stem had exhibited activity against *S.* 

**7.** *Salmonella* **control in food product and food packaging by plant extract** 

Nowadays, the foodborne outbreaks *Salmonella* food poisoning and the prevalence of antibiotic resistant *Salmonella* in humans, animals and food are increasing (Rabsch et al., 2001; Angulo et al., 2000; O'Brien, 2002). Consumers are also concerned about the safety of food containing synthetic preservative. Therefore, there has been growing interesting in using natural antibacterial extract from herb or spice for food conservation (Smid & Gorris, 1999; Fasseas et al., 2008; Gutierrez et al., 2008). Particular interest has been focused on the potential application of plant extract or essential oils as safer additives for meat, poultry,

The combination of the oregano essential oil at 0.6% with nisin at 500 IU/g showed stronger antimicrobial activity against *S. enteritidis* in minced sheep meat than the oregano EO at 0.6% but lower than the combination with nisin at 1000 IU/g (Govaris et al., 2010). The minimum inhibitory concentration of the Capsicum extract to prevent the growth of *S. typhimurium* in minced beef was 1.5 mL/100 g of meat; the addition of 1%, 2%, 3% and 4% w/w of sodium chloride did not have any additional inhibitory effect on *Salmonella* (Careaga et al., 2003). Ravishankar et al. (2009) suggest that the food industry and consumers could use apple-based edible films containing cinnamaldehyde or carvacrol as wrappings to control surface contamination by foodborne pathogenic microorganisms, which at 23°C on chicken breasts, films with 3% antimicrobials showed the highest reductions (4.3 to 6.8 log cfu/g) of both *S. enterica* and *E. coli* O157:H7. Moreover, the lowest concentration of trans-cinnamaldehyde (10 mM) reducing *S. enteritidis* populations inoculated on chicken cecal contents by approximately 6.0 log(10) cfu/mL after 8 h and >8.0 log(10) cfu/mL after 24 h of incubation (Johny et al., 2010). The carvacrol vapour was effective at preventing growth of *Salmonella* on agar and in significantly reducing viable numbers on raw chicken at temperatures ranging from 4°C to 37 °C (Burt et al., 2007). The results by Shan et al. (2011) showed that the five spice and herb extracts (cinnamon stick, oregano, clove, pomegranate peel, and grape seed) were effective against *S. enterica* in cheese at room temperature (~23°C), which the clove showed the

A and *S. gallinarum* ATCC 9184) (Lee et al., 2006).

*typhi* (Evans et al., 2002).

milk, fruit and vegetable.

highest antibacterial activity.


Table 1. Essential oils in each plant organ (Base on Krishnasamy, 2008)
