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The emergence of resistance to antimicrobial agents is a global public health problem. Some microorganisms may develop resistance to a single antimicrobial agent (or related class of agent), while others develop resistance to several antimicrobial agents or classes. These organisms are often referred to as multidrug-resistant or MDR strains. Identification of new molecules that show activity against multidrug-resistant microorganisms and its development on a new antimicrobial drug, would be an important step in the fight against antimicrobial resistance. This paper presents experimental data regarding the synthesis of several quinolones. The novel compounds having quinolone structure were synthesized by Gould-Jacobs method. Their structure has been determined and confirmed by the following physicochemical methods: elemental analysis, IR spectral analysis, H-NMR, C-NMR, UV, thin layer chromatography. The new compounds have been evaluated for „in vitro” activity by determining minimum inhibitory concentration against a variety of bacteria Some of new quinolones, which showed a good activity, have been tested against 30 strains of methicillin resistant Staphylococcus aureus isolated in the Microbiology Laboratory of INBI Prof. “Dr. Matei Bals” during 2012 The minimum inhibitory concentration (MIC) of the isolates have been determined by agar plate Mueller Hinton (bioMerieux) dilution method using the reference strain Staphylococcus aureus ATCC 29213. The 30 strains of isolated have been also tested for susceptibility to ciprofloxacin, levofloxacin and imipenem by Etest method. Base on the “in vitro” studies, the quinolone FPQ-30 appears to be an promising compound, all strains isolates were inhibited at a concentration of 8 μg/ml.

Chitosan is a polysaccharide derived from chitin; chitin is the second most abundant polysaccharide in the world, after cellulose. Chitosan is biocompatible, biodegradable and non-toxic, so that it can be usedin medicalapplications such as antimicrobial and wound healing biomaterials. It also used as chelating agent due to its ability to bind with cholesterol, fats, proteins and metal ions.

Monitoring planes of the occurrence of antimicrobial resistance among bacteria isolated from both animals and humans should be considered essential and strategic for preserving not only human health but also animal welfare (well-being). Moreover, the use of antimicrobial in companion animals (pets) received little attention and is not currently regulated in comparison with what happens in livestock; for this reason, the prevalence of antibiotic resistance in 165 different Enterococcus strains isolated from dogs (subjected to previous antibiotic treatment(s) or not) was determined. For each strain, the minimum inhibitory concentration (MIC) against 9 different antibiotics was assessed. While all isolated strains were susceptible to vancomycin, high resistance frequency toward erythromycin, rifampicin, enrofloxacin, and tetracycline was detected. Enterococcus faecium strains isolated from the previously treated dogs demonstrated more resistance to tetracycline compared to the control ones. Although canine enterococci showed a high degree of antibiotic resistance, they were susceptible to vancomycin, and for this reason, the hypothetical contamination of vancomycin-resistant enterococcal strains in dogs is still considered to be minimal in Italy.

Infections caused by diverse bacteria represent a major problem that threats the health of humans. This stimulates the scientists to find new solutions for treating these diseases by clarifying the interactions of antibacterial compounds with the biological medium. In this context, the chapter presents some basic concepts regarding the antibacterial drugs. The synthesis routes of novel compounds and specific design techniques with polymer materials are described in correlation with the in vitro and in vivo activity of antibacterial substances. Essential data about the mechanism of action, selected in vivo efficacy and mechanisms of resistance to the most used antibacterial drugs are reviewed.

Antimicrobial peptides (AMPs) are small cationic peptides which protect their hosts against bacteria, protozoa, viruses, and fungi. Bacterial AMPs are called bacteriocins, and are produced by both Gram-positive and Gram-negative bacteria. Because of their high potency and specificity, bacteriocins are considered as promising antimicrobial agents for different applications, including food preservation and infection treatment; specially the ones produced by acid lactic bacteria species (Gram-positive). Nisin is the most intensively studied and used bacteriocin, it is found commercially available and its use is regulated in over 50 countries. Therefore, special attention is given to this bacteriocin.

In veterinary medicine, large quantities of antibiotic substances are administered each year for therapeutic and prophylactic purposes or to promote growth. As a consequence, the antibiotics and bacteria carrying transferable antibiotic resistance genes are excreted by the animals and reach the environment through run-off, leaching, and/or following manure application to agricultural fields, where they have been found to affect the structure and function of soil bacterial communities. However, we are only beginning to understand the global effects of environmental pollution with antibiotics and resistance determinants and the resulting risks for human health. For regulatory purposes, there is urgent need for criteria and methods that allow reliable and reproducible assessment of risks associated with release of realistic concentrations of antibiotics and resistance determinants into the environment following manure application. In this chapter, we will summarize recent advances, limitations, and research needed to optimize the methods to quantify and evaluate the effects and risks associated with these compounds. Approaches that are discussed focus on antibiotic resistance genes and include classical tools such as cultivation and PCR detection as well as quantitative real-time PCR and next-generation sequencing technologies used in combination with functional screening.

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Antimicrobial Resistance of Bacteria in Food

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Assessment of Antibiotic Resistance in Probiotic Lactobacilli

Antibiotic Susceptibility of Probiotic Bacteria

Dairy Propionibacteria: Less Conventional Probiotics to Improve the Human and Animal Health

Efficiency of Probiotics in Farm Animals

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