Question

Explain antimicrobial resistance and detection among staphylococci, streptococci, enterococci and similar organisms.

Answer 1

Enterococci ,staphylococci,streptococci etc are important nosocomial pathogens that has emerged over the past decade, staphylococci being the leading cause of nosocomial infections, accounting more than 12% of hospital-associated infections yearly in the U.S

Detection: The genus Streptococcus and the genus Enterococcus. Both are Gram-positive cocci 0.5-1.0 µm in diameter, typically occurring in pairs and chains of varying length when grown in a liquid medium, and often occurring singly, in pairs, short chains, and clusters when taken from an agar culture.They are both catalase-negative.They can be isolated on blood agar

Antimicrobial agents represent one of the major therapeutic tool in human and veterinary medicine to control and treat a variety of diseases. But due to use or misuse of these antimicrobial agents in a wide sence, there has been development of resistant strains that no longer respond to theses medicines. The following are the methods by which resistance is acquired:

1.Selection Pressure : The increased prevalence and dissemination of resistance is an outcome of natural selection and is viewed as Darwins theory of survival of the fittest.In a colony there will be very few cells that will be resistant to the particular antimicrobial agent. Succeptible ones will be eliminated and resistant ones survive. By long term use of these antimicrobial substances the number of resistant organism will increase.

2.Mutation.: It is any change in dna tgat can cause change in gene product. When a succeptible bact comes in contact with antimicrobial chemicals, the antimicrobials bind to specific enzymes here DNA gyrase which is essential for DNA replication.These drugs block the dna replication thus preventing bact replication. When mutation occurs and the genes of these dna gyrase get modifies , these antimicrobials can no longer bing to the dna and can reasily replicating meaning it has acquired resistance.