Synergistic Inhibition of Natural Honey and Potato Starch and their Correlation with Diastase Number and Sugar Content against Klebsiella pneumoniae ATCC 27736

The overuse of antimicrobial agents is one of the major factors in the development and spread of drug resistance in organisms, as well as in colonization and infection by drug-resistant organisms. Klebsiella pneumoniae is a successful opportunistic pathogen and has been associated with various ailments such as urinary tract infection, osteomyelitis, meningitis, septicemia, respiratory tract infection and diarrhea [1,2]. Treatment of K. pneumoniae infections has become increasingly difficult because of the predominance of multipleantibiotic-resistant strains [3,4]. Thus, it is urgent need to find out new antimicrobial agents. Natural products traditionally have played an important role in drug discovery and were the basis of most early medicines [5]. Honey is a natural product that is used for its antibacterial activity [6-10]. Honey, produced by the honeybee, is a natural supersaturated sugar solution, which is mainly composed of a complex mixture of carbohydrates [11]. Carbohydrates, the main constituents of honey, are produced by honey-bees from nectar sucrose, which is transformed through the action of different enzymes, notably, diastase (αand β-amylase), invertase (α-glucosidase), glucose-oxidase, catalase and acid phosphatase, which come from nectar sources, salivary fluids and the pharyngeal gland secretions of the honeybee [12]. Amylase in honey mainly originates from the salivary secretions of honeybees, which was concluded based on the presence of amylase in honey produced by sugar-fed honeybees [13]. Diastase (mixture of amylases) is used to evaluate honey freshness and heat treatment. Diastase is largely from honeybees with a contribution from pollen and nectar [14]. The α-amylase splits the starch chain randomly, producing dextrin, and the β-amylase splits the reducing sugar maltose from the ends of the starch chain. According to the Honey Quality and International Regulatory Standards, from the International Honey Commission, the diastase activity must not be less than or equal to 8, expressed as diastase number (DN). DN in Schade scale, which corresponds to the Gothe scale number, is defined as g starch hydrolyzed in 1 h at 40°C per 100 g honey. HMF (5-hydroxymethylfurfuraldehyde) measurement is used to evaluate the quality of honey; generally not present in fresh honey, its content increases during conditioning and storage [15]. The European Union [16] (EU Directive 110/2001) fixed a HMF limit in honey of 40 mg/kg. In this study, we evaluated the antibacterial activity of six varieties of honey and their combination with potato starch in correlation with diastase number (αamylase), and sugar content.