مقالات پذیرفته شده در هفتمین کنگره بین المللی زیست پزشکی
Corynebacterium diphtheriae toxin mechanism
Corynebacterium diphtheriae toxin mechanism
Arefe Nikmehr,1Saman Hakimian,2,*
1. M.sc student of Microbiology , Faculty of Basic Sciences , Shahid Ashrafi Esfahani University , Esfahan , Iran 2. M.sc student of Microbiology Islamic Azad University Central Tehran Branch , Iran , Tehran
Introduction: The symptoms of diphtheriae disease include sore throat , fever , cough , hoarseness , and in severe cases , heart failure , kidney failure and paralysis of arms and legs and the involvement of cervical lymph nodes may cause a profound swollen neck sometimes referred to as a “bull-neck”.Coughing can remove parts of the pseudomembrane, easing the situation of the patient temporarily , and after several fits of coughing , the pseudomembrane might even be removed and healing might be achieved. However , in several cases , obstruction of airways results in suffocation , agony and death of the patient.
Corynebacterium diphtheriae produces diphtheria toxin , which is a protein with high toxicity and is produced as a result of bacterial contamination with beta bacteriophage , which contains Tox toxin.
The pathogenesis of C.diphtheriae is not well elucidated . The most likely entry portals for nontoxigenic C.diphtheriae.
Methods: diphtheriae are skin lessions or dental caries . In recent years , severe and often fatal systemic disease (which were previously quite rare) caused by nontoxigenic C.diphtheriae have been registered in various countries . Nontoxigenic C.diphtheriae often were found to be associated with cutaneous lesions but can transform into severe clinical symptoms , such as myocarditis , polyneuritis , bacteraemia , septic arthritis and endocarditis , characterized by a high mortality rate reaching over 40% . Among the factors that predispose to the invasive infections caused by nontoxigenic C.
diphtheriae occurrence are homelessness , abuse of alcohol and injection drugs and diabetes mellitus , hepatic cirrhosis and dental caries . Furthermore , refugees and foreign travelers constitute population groups that are particularly at risk of nontoxigenic C.diphtheriae infections.
The gene sequence analysis indicates that DT is preceded by 25 residues of leader peptide , which is most likely involved in toxin secration . DT is produced as a proenzyme that requires specific activation for its toxic function , either prior to or immediately after binding to a sensitive cell.
Results: immunization with diphtheriae toxoid has been extremely effective , and patients with diphtheriae should be promptly treated with antitoxin to neutralize the circulating diphtheriae toxin.
Conclusion: protective antibody titres and to provide supplementary booster doses if the titres are found to be suboptimal.
The cornerstone of treatment of suspected respiratory diphtheriae is early administration of diphtheria antitoxin (DAT), which can prevent life-threatening complications. DAT is currently produced using serum from horses that are hyperimmunized with diphtheria toxoid , and there is a global shortage of equine DAT due to high manufacturing costs and previously low demand . beginning in 1997 , physicians have been able to access an unlicensed DAT product from the CDC through an FDA approved investigational New Drug (IND) protocol for emergency treatment of suspected diphtheria cases .
In countries with high anti-diphtheriae vaccination coverage , the disease is very rare , but in some regions of Africa and Asia diphtheriae is still recognized , with thousands of cases reported annually .