if their growth is not halted by the maximum level of the antibiotic that can
be tolerated by the host.
Resistance. 2) Acquired Resistance.
Inherent Resistance: Some organisms are
inherently resistance to a particular antibiotic. This type of resistance is
known as Inherent Resistance.
Acquired Resistance: Repeated use of an
antibiotic or excessive use or stop & start type of therapy may lead to resistance
against organisms. Acquired antibiotic resistance.
Reasons of Inherent resistance:
the following reasons:
Modification of target sites: Alteration of an
antibiotic’s target site through mutation can confer organism resistance to one
or more related antibiotics. Example, in case of S. pneumonia resistance to
beta-lactam antibiotics involves alteration in bacterial penicillin binding
proteins, resulting in decreased target site binding of antibiotics.
Decreased Accumulation: If any antibiotic fail
to produce sufficient concentration to injure or kill the organism due to
decreased uptake or increased in influx can cause resistance toward one or more
related antibiotics. For example, gram negative organism can limit the
penetration of certain antibiotics causing alteration in number and structure
of channels in outer membrane.
Enzymatic inactivation: Some organism has ability
to inactivate or destroy antimicrobial agent by producing a particular enzyme
that can alter ring structure of antibiotic, hence, confer resistance toward
antimicrobial agent. For example, Beta-lactamases that hydrolytically
inactivate the beta-lactam ring of penicillin, cephalosporins.
permanent gain or alteration of bacterial genetic information. Resistance
develops due to the ability of DNA to undergo spontaneous mutation or to move
from one organism to another. MRSA (Methicillin-Resistant Staphylococcus aureus
bacteria) and VRE (Vancomycin-resistant Enterococi
) are two major terms used for acquired drug resistance.
pressure, mutation, genetic transfer, societal pressure, inappropriate drug
use, inadequate diagnosis, hospital use and agricultural and animal use of
drugs and overuse of drug.
Mutation: All microorganisms go under replication
and dividing into each other that allowing them to quickly adapt new
environment. During replication, mutation arises and some of these mutations
help microorganism to survive from antibacterial environment and produce
Selective pressure: If microorganism carry
resistance gene, it will replicate and produce more resistant microorganisms
and dominant other microbial population.
Genetic transfer: Microorganisms have tendency
to get genes from other microbe. They can also get genes from drug resistant
Inappropriate drug use: Prescribing wrong
antibiotics, gap between doses, repeated use of same antibiotic for long term,
overdose of antibiotic and self medication are few in list that may produce
antibiotic resistant microbes.
Agriculture and Animal use: Antimicrobial agents
that are used for treat of animal or use in different purposes of agriculture
may also be major cause of drug-resistant bacteria.
preventing the overuse and misuse of antimicrobial and adopting healthy life
style. Antibiotics should be used only after proper diagnosis and under medical
problem and have to take strong step to prevent further to critical situation.