Diphtheria

The Druggable Pocketome of Corynebacterium diphtheriae: A New Approach for in silico Putative Druggable Targets

Diphtheria is an acute and highly infectious disease, previously regarded as endemic in nature but vaccine-preventable, is caused by Corynebacterium diphtheriae (Cd). In this work, we used an in silico approach along the 13 complete genome sequences of C. diphtheriae followed by a computational assessment of structural information of the binding sites to characterize the “pocketome druggability.” To this end, we first computed the “modelome” (3D structures of a complete genome) of a randomly selected reference strain Cd NCTC13129; that had 13,763 open reading frames (ORFs) and resulted in 1,253 (∼9%) structure models. The amino acid sequences of these modeled structures were compared with the remaining 12 genomes and consequently, 438 conserved protein sequences were obtained. The RCSB-PDB database was consulted to check the template structures for these conserved proteins and as a result, 401 adequate 3D models were obtained. We subsequently predicted the protein pockets for the obtained set of models and kept only the conserved pockets that had highly druggable (HD) values (137 across all strains). Later, an off-target host homology analyses was performed considering the human proteome using NCBI database. Furthermore, the gene essentiality analysis was carried out that gave a final set of 10-conserved targets possessing highly druggable protein pockets. To check the target identification robustness of the pipeline used in this work, we crosschecked the final target list with another in-house target identification approach for C. diphtheriae thereby obtaining three common targets, these were; hisE-phosphoribosyl-ATP pyrophosphatase, glpX-fructose 1,6-bisphosphatase II, and rpsH-30S ribosomal protein S8. Our predicted results suggest that the in silico approach used could potentially aid in experimental polypharmacological target determination in C. diphtheriae and other pathogens, thereby, might complement the existing and new drug-discovery pipelines.

An integrative in-silico approach for therapeutic target identification in the human pathogen Corynebacterium diphtheriae

Corynebacterium diphtheriae (Cd) is a Gram-positive human pathogen responsible for diphtheria infection and once regarded for high mortalities worldwide. The fatality gradually decreased with improved living standards and further alleviated when many immunization programs were introduced. However, numerous drug-resistant strains emerged recently that consequently decreased the efficacy of current therapeutics and vaccines, thereby obliging the scientific community to start investigating new therapeutic targets in pathogenic microorganisms. In this study, our contributions include the prediction of modelome of 13 C. diphtheriae strains, using the MHOLline workflow. A set of 463 conserved proteins were identified by combining the results of pangenomics based core-genome and core-modelome analyses. Further, using subtractive proteomics and modelomics approaches for target identification, a set of 23 proteins was selected as essential for the bacteria. Considering human as a host, eight of these proteins (glpX, nusB, rpsH, hisE, smpB, bioB, DIP1084, and DIP0983) were considered as essential and non-host homologs, and have been subjected to virtual screening using four different compound libraries (extracted from the ZINC database, plant-derived natural compounds and Di-terpenoid Iso-steviol derivatives). The proposed ligand molecules showed favorable interactions, lowered energy values and high complementarity with the predicted targets. Our proposed approach expedites the selection of C. diphtheriae putative proteins for broad-spectrum development of novel drugs and vaccines, owing to the fact that some of these targets have already been identified and validated in other organisms.

Sudden death of a child due to respiratory diphtheria

A four-year-old girl presented to the emergency department with respiratory distress. Death occurred despite attempted resuscitation. The illness was not clinically diagnosed. Her father revealed that she had a fever and sore throat for the last four days and was not immunised for diphtheria. Characteristic gross and microscopic pathology of respiratory diphtheria and microbiological findings were observed. The cause of death was acute respiratory failure consequent upon upper airway obstruction from diphtheria. Forensic pathologists should remember that the diphtheria cases can cause sudden death especially in developing countries.

Diphtheria - 'The strangling angel' of children

Diphtheria, an acute infectious condition caused by Corynebacterium diphtheriae, was once a major killer of children. Although the mortality rates dropped dramatically in the mid-twentieth century, due to a combination of improved standards of living and immunization programs, outbreaks are still occurring. Two children, aged four and five years respectively, are reported to demonstrate characteristic features of lethal cases. Death in case 1 was due to an extensive upper airway pseudomembrane causing acute respiratory failure. The diagnosis of diphtheria was only made at postmortem. Death in case 2 was due to acute cardiac failure with heart block complicating diphtheria. Other mechanisms in fatal cases involve disseminated intravascular coagulation, renal and endocrine failure. Declining levels of immunity among adults has resulted in a change in the epidemiological pattern of the disease with an older age of victims in recent outbreaks. As a result of population shifts and failure to immunize children it is likely that forensic pathologists may see more cases of diphtheria in the future. Due to the rarity of cases in Western communities and atypical presentations, the diagnosis may only be established at autopsy.

Space-occupying and life-threatening infections of the head, neck, and thorax

Infections of the deep structures of the head and neck are polymicrobial, rapidly progressive, and frequently life-threatening. The bacteriology, clinical presentation, and the need for multidisciplinary management of these infections are stressed. In addition, this article discusses selected head and neck infections of immunocompromised hosts and postexposure prophylaxis for serious infections of the pharynx.

Complications of diphtheria seen during the 1978 outbreak in Khartoum

Twenty-nine cases of complicated diphtheria infection occurring during an epidemic in Khartoum are reviewed. The organism was a Corynebacterium diphtheriae subsp. gravis with an unusual property of fermenting sucrose. Eighteen patients were detected during prospective follow-up, where as 11 presented initially with a complication. Complications were mostly seen among pre-school children (65.5%). A routine immunization course had been completed in only two of the patients. Neurological complications were the commonest, lasting for more than two weeks, and five of the six deaths were due to cardiovascular complications.