Etiket Arşivleri: antibiotics

Antimicrobial Activity of Lactic Acid Bacteria on Pathogens in Foods ( Prof.Dr. Dilek HEPERKAN )

Antimicrobial activity of lactic acid
bacteria on pathogens in foods
Why succesful?
How succesful?

Prof.Dr. Dilek Heperkan

Istanbul Technical University,

Faculty of Chemical and Metallurgical
Engineering, Dept. of Food Engineering

Food Technology2014 21-23 July, Las Vegas

Microorganisms especially bacteria can be used for a number of beneficial purposes. Among them some are more prominent like Lactic acid bacteria (LAB) and bifidobacteria.

Lactic acid bacteria have been used as natural food-grade preservatives against a variety of undesirable microorganisms.

LAB has been used for production of fermented foods for many years. As a matter of fact fermented foods existed long before mankind discovered microorganisms.

During their activity in production of fermented foods their inhibitory potential on pathogenic bacteria have been recognised and they gained increasing interest in the scientific community.

Thus LAB has been used as a tool to produce antimicrobial compounds and to control undesirable microorganisms.


On the other hand, acute diarrhea due to the loss of normal intestinal microbiota, drug-resistant strains and chronic toxicity due to widespread use of antibiotics are well known negative effects of antibiotics.


The risks of toxic residues in foods, as well as contamination of soil and water due to the use of xenobiotics in food production chain are considered negatively by the public.

Lab producing a wide range of antimicrobial metabolites thus, the last two decades have seen pronounced advancements in using LAB and their metabolites for natural food preservation, as well as crop protection, and health protection.

Evaluating the Effectiveness of Antibiotics, Antiseptics, and Disinfectants

Antiseptics, disinfectants, and antibiotics can be referred to as chemical anti-microbial agents, in contrast to physical antimicrobial agents such as heat and radiation. Microbiologists usually distinguish between antiseptics and disinfectants in the following way. Antiseptics are preparations of chemicals that are meant to be applied to the skin or other living tissue. Examples are chemical preparations designed to treat wounds or infected throats. Alcohol, probably the most widely used antiseptic, denatures proteins, extracts lipids, and dehydrates cells, all of which probably contribute to the effectiveness of alcohol as an antiseptic. Iodine is another excellent antiseptic, though its effects on microbes are not understood. Heavy metals are also used in antiseptic preparations; for example, laws require that silver nitrate be applied to the eyes of newborn humans, especially to prevent the transmission of gonococci from mother to infant.

Laboratory‎ > ‎Antimicrobial Agents

1. How would you determine if a zone of inhibition was due to the bacteriocidal (killing) or bacteriostatic (growth inhibiting) action of an antimicrobial?

2. Sometimes, one observes a few bacterial colonies growing within a zone of inhibition. How would you explain this? How would you conclusively prove your hypothesis?

3. How do antibiotics differ from other natural products of microbes such as lactic acid, acetic acid, ethanol and others?

4. How are new antibiotics discovered? What properties must they possess in order to be more desirable than previously discovered antibiotics?


Laboratory‎ > ‎Antibiotic Sensivity Testing


Antibiotics form an interesting therapeutically useful group of compounds.The production of antibiotics is a common occurance.In this experiment we have examined the effectiveness of antibiotics (Enoxocin,amoxclavocid and aztreonom) and we have compared their inhibition effects on S.aureus and E.coli microorganisms.


An antibiotic is a drug that kills or slows the growth of bacteria. Antibiotics are one class of “antimicrobials”, a larger group which also includes anti-viral, anti- fungal, and anti-parasitic drugs. They are relatively harmless to the host, and therefore can be used to treat infection. The term originally described only those formulations derived from living organisms, but is now applied also to synthetic antimicrobials, such as the sulfonamides.Unlike previous treatments for infections, which included poisons such as strychnine, antibiotics were labelled “magic bullets”: drugs which targeted disease without harming the host. Antibiotics are not effective in viral, fungal and other nonbacterial infections, and individual antibiotics vary widely in their effectiveness on various types of bacteria. Some specific antibiotics target either gram-negative or gram-positive bacteria, and others are more wide-spectrum antibiotics. The effectiveness of individual antibiotics varies with the location of the infection and the ability of the antibiotic to reach this site. Oral antibiotics are the simplest approach when effective, with intravenous antibiotics reserved for more serious cases. Antibiotics may sometimes be administered topically, as with eyedrops or ointments.