Listeria Spp Resistance Mechanisms Biology Essay

Small is known about the mechanisms of immune bacteria species and their opposition cistrons isolated in nutrient processing environments, and different nutrient like in Botswana. Bacterial species and strains resistant to different antimicrobic agents are of major public wellness concern because they pose wellness hazards attributed to human deceases, ( Dorota, 2012 ) . Antimicrobial drug opposition is caused by human and non human use of disinfectants including intervention of animate being diseases ( WHO ) , over the counter prescription and over prescription of antimicrobic drugs in some states, deficit of wellness substructure, deficit of and undependability of drug supplies, low quality of drugs ( who ) , and usage of microbials to bring forth workss, nutrient and provender ( Dorota et al, 2012 ) .

Furthermore, the happening of non-pathogenic bacteriums demoing opposition to antimicrobic drugs has attained consciousness throughout recent old ages ( [ Kastner et al. , 2006 ] and [ Talon and Leroy, 2011 ] ) . Even et Al. ( 2010 ) . Information and statistics generated from the scrutiny of antimicrobic opposition and antimicrobic handling should play an input in the betterment of public policies for the control of antimicrobic opposition. These information is indispensable in the pre- and post-licensing procedure and in the advancement and direction guiding rules for veterinary usage ( who ) .

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Since bacteriums have the capacity to develop opposition to antimicrobic agents over drawn-out exposure to antimicrobic drugs, it is hence believed that a Listeria bacteria which is considered to be susceptible to most disinfectants has the same capableness to develop opposition to disinfectants. Like other medically of import bacterial species, Listeria has the capableness to present serious deductions to its patients as it consequences in serious diseases including meningitis in newborn babes, patients with weak or compromised system, and abortion in pregnant adult females, ( morobe et Al, 2009, korsak, 2012 ) .

The continued unregulated usage of antimicrobic agents consequences in natural showing and choice of immune bacteriums strains and antimicrobic opposition cistrons that can be transmitted between human through nutrient and between bacterial species through natural transportation of plasmids and jumping genes by junction. Plasmids such as pIP501 have been found to be able to retroflex in Listeria and to advance its ain transportation between strains of Listeria and from Listeria back to Streptococcus ( P & A ; Atilde ; ©rez-Diaz, Vicente 1988 ) , and plasmid pAM & A ; Icirc ; ?1 transferable from Enterococcus faecalis, confabulating opposition to erythromycin, has been transferred to Listeria. Transposons such as Tn916, antecedently found in E. Faecalis, carries Tet ( M ) cistron doing opposition to tetracycline-minocycline ( Vicente 1988 ) .

Bacterias can demo opposition to antimicrobic agents utilizing a scope of mechanisms. A figure of species of bacteriums are of course immune to 1 category of antimicrobic agents and as such all strains of that bacterial species are immune to all the members of those antibacterial categories ( tenover, 2006 ) . There are instances of acquired opposition, where originally susceptible populations of bacteriums become immune to an antimicrobic drug and grow and spread under the selective force per unit area of usage of that antimicrobic drugs ( tenover, 2006 ) .

The bacteria can derive cistrons encoding enzymes, including lactamases that destroy the antimicrobic drug before it can bring forth a coveted result ( tenover, 2006 ) . Furthermore bacteriums may get outflow pumps that remove the antimicrobic drug from the cell before it can acquire to its mark site and bring forth its result. Besides bacteria may obtain few cistrons for a metabolic way which finally produces changed bacterial cell walls that no longer hold the binding site of the antimicrobic agent, or sometimes bacteriums can obtain mutants that cut down right of entry of antimicrobic agents to the intracellular mark location through down ordinance of porin cistrons. Several familial mechanisms, including transmutation, junction, or transduction besides confer antimicrobic opposition to drugs. Through familial exchange mechanisms, many bacteriums have become immune to different categories of antibacterial agents, and such bacteriums with multidrug opposition have become a cause for serious dismay, chiefly in infirmaries and other health care installations where they occur most normally.

Previous surveies have shown that Achromycin opposition is conferred by ribosome protection due to either the Tet ( M ) or Tet ( S ) cistron ( Charpentier, E. , and P. Courvalin. 1999. ) . The Tet ( S ) cistron was detected in both Multi Drug Resistant strains, whereas the staying strains had acquired Tet ( M ) , ( morvan ) . Surveies have besides shown that flouroquinolone opposition was due to active outflow associated with overexpression of the lde cistron ( Godreuil,2003 ) .

Previous research have besides shown that Chloromycetin opposition is due to acquisition of a cat cistron encoding an acetyltransferase which catalyzes acetyl-S-coenzyme A ( CoA ) -dependent acetylation of Chloromycetin at the 3-hydroxyl group ( Poyart-Salmeron, 1990 ) . Streptomycin opposition was attributed to presence of high degree BM4210 plasmid encoded by 6-N-streptomycin adenylyltransferase, encoded by the aad6 cistron ( Charpentier,1999 ) and suspectedly ribosomal mutants ( morvan ) . Surveies have besides reported that trimethoprim opposition was due to acquisition of the dfrD cistron, encoding a immune dihydrofolate reductase ( Huovinen, 1995 ) . Resistance to trimethoprim has non yet been said to be linked with any antibiotic opposition ( morvan )

Despite the significance and relevancy of information on the mechanisms of drug immune L. monocytogenes strains, there is no information on the antimicrobic opposition mechanisms of L. monocytogenes isolated from nutrient and food-processing environments in Botswana and no extended surveies of this quality have been carried out. For this evidences, analyzing the opposition mechanisms of L. monocytogenes, although comparatively uncommon, should nevertheless be pursued.

Literature reappraisal

Statement of the job

Observation: The mention direction and remedy of listeria meningitis is at present based on the usage of high doses of Principen or Amoxil and Garamycin because Listeria monocytogenes is extremely susceptible to a broad scope of antimicrobic drugs. However, the overexploitation of the above mentioned drugs and other antimicrobic agents over clip in animate beings, works production and infirmaries creates a reservoir of immune Listeria monocytogenes and of Listeria monocytogenes -borne opposition cistrons doing it hard to handle listeria meningitis.

Question: What mechanisms enable Listeria monocytogenes to be immune to antimicrobic agents although it is known to be extremely susceptible to a broad scope of antibacterial drugs?


Null hypothesis

Listeria monocytogenes is susceptible to a broad scope of antimicrobic agents and as such it has non yet developed mechanisms of opposition to therapeutically used antibiotics.

Alternate hypothesis

Though antecedently reported to be widely susceptible to a broad scope of antimicrobic agents, Listeria monocytogenes has developed mechanisms of opposition to antimicrobic agents.


Listeria monocytogenes opposition to antimicrobic drugs is due to indispensable cistrons responsible for non-susceptibility to therapeutically used antibiotics, conjugative jumping genes and plasmids transporting antibiotic opposition cistrons and point mutants.

Experimental work:

The experiment will be carried out utilizing Listeria monocytogenes isolates isolated from different nutrient beginnings around Gaborone ( Botswana ) in 2009. Based on antimicrobic susceptibleness consequences, tetracycline-resistant L. monocytogenes isolates will be farther characterized by observing the presence of Tet ( M ) , Tet ( K ) , Tet ( L ) , Tet ( S ) , and Tet ( T ) cistrons.


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