THERAPIES OF
C. DIPHTHERIAE INFECTION
The main way of controlling and treating C. Diphtheriae infection is with the vaccine, which is currently given in the UK at a young age. This being the DTP containing tetanus and pertussis as well as diphtheria vaccines in a single dose. Starts as early as 6 weeks of age as a series of 3 doses/injections at a minimum of 4 weeks apart, and last dose should be aimed to be given around 6 months of age. With boosters at 12-23 months, 4-7 years and 9-15 years. This can be completed up until 7 years of age. The vaccine can be given also be given later on in life (over 7 years old) just at modified intervals between doses (World Health Organization, 2018), but this level of vaccination is lacking in developing countries.
Although antibiotics and the antitoxin can be used on the onset of the symptoms, it can only be given before the toxin has enter the cells of the person infected (Baron et al., 1996). As once the infection has reached this stage, the antitoxin is unable to reach the toxin. As it cannot enter the cell and can’t stop the toxins actions.
The vaccine is made up of a diphtheria toxoid this is made from the C. Diphtheriae toxin as illustrated in Figure 1. By producing large amounts of the toxin incubating it with formatin to form the toxoid and purifying the mixture to obtain the necessary dosage. This process has been continued to be refined as more has been learnt about the diseases and the way the immune system reacts to the vaccine, by using recombinant granulocyte macrophages with the diphtheria vaccine. Which was found to improve the humoral and cellular immune response. (Grasse et al., 2018).
The effectiveness of the different antibiotics is shown in the figure 2 below. Erythromycin is a macrolide antibiotic. That works by entering the bacterial cell wall, and membrane and irreversibly binds to the 50S ribosomal subunit. Therefore, preventing protein synthesis (Usary and Champney, 2001). Clindamycin works in the same way as erythromycin, but reversibly binds to the subunit (Nodzo et al., 2019). The two penicillin-based antibiotics benzyl penicillin and amikacin as well as the antibiotic cephaloridine all effect the formation of the cell wall by binding to the Penicillin binding proteins (PBS) (Yocum et al., 1980, Acar et al., 1975)
C. Diphtheriae is showing some resistance to erythromycin, this is shown in a study in 2019 in Indonesia where 2.8% of patients with diphtheria were resistant to erythromycin.(Husada et al., 2019).It has been shown this is due to a mutation on the pNG2 plasmid (Tauch et al., 2003).
The antitoxin is comprised of antibodies to the diphtheria toxin. These are mostly produced in horses Infected with the diphtheria bacterium. Therefore, producing antibodies as part of the humoral immune response (Smith et al., 2017). These antibodies then bind to the AB toxin (Madigan et al., 2019) and therefore making it unable to bind to and enter the host cells.
An antibiotic and anti-toxic should be given together as they both treat the infection in two different ways once the infection occurred. Although the best way of preventing infection and therefore spread of the bacteria is via vaccination with the diphtheria toxoid.
References
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