A large number of human, animal and plant disease are caused by pathogenic microbes (fungi, bacteria and algae). Within the recent years, infections have increased to a great extent. Infections due to fungi and bacteria have been a major cause of death in higher organisms. Infectious diseases, particularly skin and mucosal infections, are common in most of the tribal inhabitants due to lack of sanitation, potable water and awareness of hygienic food habits (Ahmad and Beg, 2001).
Foodborne illness resulting from consumption of food contaminated with pathogenic bacteria has been of vital concern to public health. Foodborne illness is a serious health threat and has significant economic consequences for people in both the developing and developed world. Foodbourne illness can be defined as ‘any illness of an infectious or toxic nature caused by or thought to be caused by the consumption of food or water’. The illness caused by foodborne microorganisms, principally bacteria, are associated with gastrointestinal symptoms of nausea, vomiting, stomach pains and diarrhoea. Since diarrhoea is a common clinical symptom in foodborne illness, many of these illnesses are referred to as ‘diarrhoeal illnesses’ (Lin et al., 2005).
An estimated 76 million cases occur annually in the United States, resulting in 300,000 hospitalizations and 5,000 deaths (Mead et al., 1999). Among the reported outbreaks in the United States during 1993-1997 periods for which the aetiology was determined, bacterial pathogens caused the largest outbreaks (75 %) and the largest percentage of cases (86 %). Salmonella spp., Listeria monocytogenes and Escherichia coli accounted for the largest number of breakfasts, cases and deaths (Todd, 1989).
40 Gram-positive bacteria are common pathogens responsible for skin disease conditions. These include Staphylococcus aureus for skin infections (Darmstadt and Lane, 1994; Trilla and Miro, 1995; Noble, 1998), Staphylococus pyogenes for pharyngitis, tonsillitis and impetigo (Cappelletty, 1998; Cunningham, 2000) and both organisms for otitis media (Brook, 1994; Brook and Gober, 1998).
The treatment of these infections is mainly based on the use of antibiotics. Historically many of the new antibiotics were isolated from natural sources (i.e. soil microbes, plants). Many more were later synthesized and introduced in clinical practices. The discovery of antibiotic penicillin by Fleming is therefore considered to be one of the most important discoveries in the world.
However, in recent years, a number of antibiotics have lost their effectiveness due to the development of resistant strains, mostly through the expression of resistance genes (Davis, 1994; Service, 1995). In addition, antibiotics are sometimes associated with adverse effects including hypersensitivity, immune-suppression and allergic reaction (Ahmad et al., 1998).
The discovery and development of new antimicrobial agent is therefore an ongoing process. Remarkable diversity of chemicals present in natural medicinal plant has tremendous potential in the searching of new antimicrobial agents with possibly novel mechanisms of actions (Ramzi and Ulrike, 2005). The compounds that can either inhibit the growth of pathogens or kill them and have no or least toxicity to host cells are considered candidates for developing new antimicrobial drugs. In recent years, antimicrobial properties of natural products are being increasingly reported from different parts of the world.
41
Disease burden, infection and foodbourne illness caused by microorganisms tested in present study
(i) Gram negative bacteria
Escherichia coli
Escherichia coli, Shigellas, Salmonellas and Vibrio cholerae are the common pathogens and major cause of foodbourne illness in worldwide. Diarrhoea caused by a variety of E. coli strains is a major problem in developing countries, especially children living in the developing world (Girard et al., 2006). Disease caused by E. coli follows ingestion of contaminated food or water and is characterized by profuse watery diarrhoea lasting for several days. It may lead to dehydration and malnutrition in young children in developing countries. Infection by E .coli strain O157:H7 is accompanied by a watery diarrhoea rapidly progressing to frank haemorrhagic colitis, and leads in up to 20 % of paediatric patients to serious sequelae, including the haemolytic uremic syndrome (HUS) characterized by thrombocytopenia, haemolytic anaemia and renal failure which can lead to permanent loss of kidney function (Karmali, 2004).
Pseudomonas aeruginosa
Infections caused by P. aeruginosa are among the most difficult to treat with conventional antibiotics (Levison and Jawetz, 1992). P. aeruginosa is an opportunistic pathogen that causes urinary tract infections, respiratory system infections, dermatitis, soft tissue infections, bacteremia and a variety of systemic infections, particularly in victims of severe burns, and in cancer and AIDS patients who are immunosuppressed (Trafny, 1998; Yau et al., 2001). The bacterium almost never infects uncompromised tissues, yet there is hardly any tissue that it cannot infect, if the tissue defences are compromised in some manner (Levison and Jawetz, 1992).
42
(ii) Gram positive bacteria
Staphylococcus aureus
S. aureus is a gram positive bacterium known to play a significant role in invasive skin diseases including superficial and deep follicular lesions. Skin and skin structure infections (SSSIs) are among the most common infectious encountered in medical practice. Skin and skin structure infections are defined by the United States Food and Drug Administration (FDA) as uncomplicated and complicated. Uncomplicated SSSIs include simple abscesses, impetiginous lesions, furuncles and cellulitis. Complicated SSSIs (cSSSIs) include deeper soft-tissue infections requiring significant surgical intervention such as infected ulcers, burns, and major abscesses or an infection occurring in the setting of a significant underlying diseases state that complicates the response to treatment (Yang and Kerdel, 2006).
Bacillus subtilis
Bacillus spp. is commonly microbes found in natural environmental including soil, plant, water and animal tissues. Most Bacillus spp. are regarded as having little pathogenic potential. B. subtilis has been known to act as invaders or secondary infectious agents in a number of diseases and has been implicated in some cases of food poisoning (Turnbull and Kramer, 1991).
2.11 In vitro cytotoxic activity tests