Antimicrobial Susceptibility, Mic and Mbc

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Antimicrobial Susceptibility, MIC and MBC
Microbiology Lab Report 3
Carolina Toscanojara

Antibiotic Sensitivity.

Antibiotics are chemical compounds that selectively interfere with the growth of microorganisms while causing little or no damage to the animal or human host. The purpose of this lab was to determine the effectiveness antibiotics against any given bacterium by means of examining the zone of inhibition, the minimum inhibitory concentration, and the minimum bactericidal concentration.

Introduction: Chemical antimicrobial agents are chemical compounds that are capable of either preventing the microorganisms for
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It is necessary to target treatment more specifically against the offending bacterium in order to reduce the risk of resistance emerging in other bacterial groups. Some antibiotics are narrow spectrum, more effective against Gram-positive or Gram-negative bacteria, and little activity against the other.

Before testing was done both bacteria, Gram positive and Gram Negative had been inoculated in 3ml TSB for 24 hours at 37°C. After incubation and with the help of cotton swab 2 plates of Mueller-Hinton agar were heavily inoculated with Gram positive obtained from the skin and Gram-negative bacteria obtained from water respectively. Swapping was done by following the procedure stated in the lab manual, going back and forth across one half of the plate ensuring the entire area was covered, turning the plate 90o and swabbing from top to bottom and turning the plate one last time a further 90o and repeat the swabbing in the indicated manner. Eventually 12 paper disks containing enough of the antibiotic were placed on the possible cultures and left in the incubator for 24 hours at 37°C. After inoculation the diameters of the clear zones (zones of inhibition) around each McFarland disk were measured with a standard ruler to the nearest millimeter. The measurements obtained were matched against a chart to determine whether the bacterium was resistant, sensitive, or intermediate in susceptibility to the antibiotic used.

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