The implementation and utility of clinical exome sequencing in a South African infant cohort

Genetic disorders are significant contributors to infant hospitalization and mortality globally. The early diagnosis of these conditions in infants remains a considerable challenge. Clinical exome sequencing (CES) has shown to be a successful tool for the early diagnosis of genetic conditions, however, its utility in African infant populations has not been investigated. The impact of the under-representation of African genomic data, the cost of testing, and genomic workforce shortages, need to be investigated and evidence-based implementation strategies accounting for locally available genetics expertise and diagnostic infrastructure need to be developed. We evaluated the diagnostic utility of singleton CES in a cohort of 32 ill, South African infants from two State hospitals in Johannesburg, South Africa. We analysed the data using a series of filtering approaches, including a curated virtual gene panel consisting of genes implicated in neonatal-and early childhood-onset conditions and genes with known founder and common variants in African populations. We reported a diagnostic yield of 22% and identified seven pathogenic variants in the NPHS1, COL2A1, OCRL, SHOC2, TPRV4, MTM1 and STAC3 genes. This study demonstrates the utility value of CES in the South African State healthcare setting, providing a diagnosis to patients who would otherwise not receive one and allowing for directed management. We anticipate an increase in the diagnostic yield of our workflow with further refinement of the study inclusion criteria. This study highlights important considerations for the implementation of genomic medicine in under-resourced settings and in under-represented African populations where variant interpretation remains a challenge.

Magnetic resonance imaging features of extremity sarcomas of uncertain differentiation

The purpose of this review is to illustrate the pertinent clinical and imaging features of extremity sarcomas of uncertain differentiation, including synovial sarcoma, epithelioid sarcoma, clear-cell sarcoma, and alveolar soft part sarcoma. These tumours should be considered in the differential diagnosis when a soft-tissue mass is encountered in the extremity of an adolescent or young adult.

Genome comparison of progressively drug resistant Plasmodium falciparum lines derived from drug sensitive clone

Chloroquine has been the mainstay of malaria chemotherapy for the past five decades, but resistance is now widespread. Pyrimethamine or proguanil form an important component of some alternate drug combinations being used for treatment of uncomplicated Plasmodium falciparum infections in areas of chloroquine resistance. Both pyrimethamine and proguanil are dihydrofolate reductase (DHFR) inhibitors, the proguanil acting primarily through its major metabolite cycloguanil. Resistance to these drugs arises due to specific point mutations in the dhfr gene. Cross resistance between cycloguanil and pyrimethamine is not absolute. It is, therefore, important to investigate mutation rates in P. falciparum for pyrimethamine and proguanil so that DHFR inhibitor with less mutation rate is favored in drug combinations. Hence, we have compared mutation rates in P. falciparum genome for pyrimethamine and cycloguanil. Using erythrocytic stages of P. falciparum cultures, progressively drug resistant lines were selected in vitro and comparing their RFLP profile with a repeat sequence. Our finding suggests that pyrimethamine has higher mutation rate compared to cycloguanil. It enhances the degree of genomic polymorphism leading to diversity of natural parasite population which in turn is predisposes the parasites for faster selection of resistance to some other antimalarial drugs.

Comparison of in vitro dissolution and permeation of fluconazole from different suppository bases

Fluconazole suppositories were prepared in hydrophilic, lipophilic, and amphiphilic bases. In vitro evaluation was conducted to compare the effect of different bases on the release and permeation of fluconazole. Four types of suppository bases were evaluated; hydrophilic (polyethylene glycol, PEG), lipophilic (cocoa butter, CB; Witepsol W45 WW45), and amphiphilic (Suppocire AP SAP, a polyglycolized glyceride). The uniformity of dosage units prepared with each base was determined by ultraviolet (UV) spectroscopy. The influence of suppository base on the release of fluconazole was studied using USP dissolution apparatus I. Rate constants for each release pattern were determined and compared using a one-way analysis of variance (ANOVA) on ranks. The order of in vitro dissolution of fluconazole from the bases was as follows: PEG > (SAP = WW45) > CB. Results suggest that in vitro release of fluconazole is greater from a hydrophilic base (PEG). Preliminary permeation studies were conducted on each type of base using Franz diffusion cells. Permeation was studied through the rat rectal membrane, and normal saline was used as the receptor medium. A modified reverse-phase high-performance liquid chromatography (HPLC) method was used and validated for analyzing fluconazole. Flux values (microgram/cm2/hr) were calculated and compared using a one-way ANOVA (p < .001). The order of permeation was as follows: SAP > (PEG = WW45) > CB. The increased permeation characteristics seen with the SAP base are probably due to an alteration of the membrane characteristics due to the surface active properties of the base.

In vitro selection of Plasmodium falciparum lines resistant to dihydrofolate-reductase inhibitors and cross resistance studies

A cloned Plasmodium falciparum line was subjected to in vitro drug pressure, by employing a relapse protocol, to select progressively resistant falciparum lines to pyrimethamine and cycloguanil, the two dihydrofolate-reductase (DHFR) inhibitor antimalarial drugs. The falciparum lines resistant to pyrimethamine were selected much faster than those resistant to cycloguanil. In 348 days of selection/cultivation, there was 2,400-fold increase in IC50 value to pyrimethamine, whereas only about 75-fold decrease in sensitivity to cycloguanil was registered in 351 days. Pyrimethamine-resistant parasites acquired a degree of cross resistance to cycloguanil and methotrexate, another DHFR inhibitor, but did not show any cross resistance to some other groups of antimalarial drugs. The highly pyrimethamine-resistant line was not predisposed for faster selection to cycloguanil resistance. Resistance acquired to pyrimethamine was stable. The series of resistant lines obtained form a good material to study the 'evolution' of resistance more meaningfully at molecular level.

Postoperative hypoxaemia during transport and in the recovery area

This study was undertaken to ascertain the incidence of postoperative hypoxaemia in the recovery area and during transfer to the recovery area while adhering to the current practice of anaesthesia and recovery room care. Attempts were also made to determine some of the risk factors for the development of hypoxaemia. There were 546 patients who had general or regional anaesthesia observed in the recovery area and of these, 534 patients were also observed during transfer using Critikon Oxyshuttle pulse oximeters. The incidence of hypoxaemia (SpO2 < or = 90%) and severe hypoxaemia (SpO2 < or = 85%) during transfer were 10.11% and 2.06% respectively. The incidence of hypoxaemia and severe hypoxaemia in the recovery area were 8.42% and 2.2% respectively. No oxygen was given to patients during transfer. In the recovery area, 322 patients (58.97%) had oxygen therapy and 224 patients (41.03%) did not. The occurrence of hypoxaemia during transfer was significantly related to the duration of surgery. In the recovery area, age and weight were found to be statistically significant risk factors. The incidence of hypoxaemia in this study is much lower than that reported in other studies.

Cure with cisplatin (II) or murine malaria infection and in vitro inhibition of a chloroquine-resistant Plasmodium falciparum isolate

Antiplasmodium properties of cisplatin [cis-platinum (II) diamine dichloride], a neoplastic drug, have been assessed in in vivo and in vitro model systems of malarial parasite. A well-tolerated dose of 6 mg/kg body weight of the compound cured the mice infected with Plasmodium berghei and the amount of cisplatin required for in vitro inhibition (IC50) of a chloroquine-resistant Plasmodium falciparum isolate was smaller than either chloroquine or quinine. The minimum inhibitory concentration (MIC) needed to prevent the in vitro multiplication of asexual blood parasites was 30 ng/ml. Late ring and trophozoite stages of the erythrocytic cycle were the most susceptible, whereas schizont and early ring stages were the least sensitive to the toxic effect of cisplatin. Multiple smaller doses were more effective in curing malaria in mice than a single large dose. In a few of the mice treated with a single intraperitoneal large dose of 6 mg/kg body weight, there was a delay in appearance of parasitemia but most of them recovered completely but slowly. This compound exerts its toxicity mainly by randomly damaging and cross-linking DNA strands as shown by Southern hybridization with a synthetic oligonucleotide probe, which is a repeat sequence in the falciparum genome. The report clearly demonstrates the antimalarial potentials of this compound and suggests a closer evaluation of this and other related compounds, specially in combination with antimalarial drugs to probe their synergistic properties.

Anaesthetic management of idiopathic long QT syndrome--a case report

This report describes the management of a patient with Idiopathic Long QT Syndrome (LQTS). The patient had life-threatening ventricular arrhythmias which did not respond to drug therapy with propranolol and phenytoin. A series of left stellate ganglion blocks were performed to control the arrhythmias. After stabilisation a high left thoracic sympathectomy was performed for a more permanent control of arrhythmias. Perioperative anaesthetic management is described and the usefulness of stellate ganglion block is demonstrated.

Multidrug resistant Salmonella typhi in Calicut, south India

Eighty S. typhi strains isolated during the period of one year (July 1989 to June 1990) were tested for susceptibility to chloramphenicol, ampicillin, cotrimoxazole, gentamicin, kanamycin, cefazolin, furazolidone and ciprofloxacin. Determination of minimum inhibitory concentration (MIC) by tube dilution method showed that the multiply resistant S. typhi strains were resistant to chloramphenicol and ampicillin up to a concentration of 1000 micrograms/ml. MIC of sulphamethoxazole was found to be 800 micrograms/ml and trimethoprim 160 micrograms/ml. The presence of R plasmid was demonstrated by resistance transfer experiments using Esch. coli K12 (F-Lac+Nal-) as the recipient. On phage typing, most of the multiresistant S. typhi isolates were found to belong to phage type E1.