Recent advances on topical antimicrobials for skin and soft tissue infections and their safety concerns

Antimicrobial resistance of disease-related microorganisms is considered a worldwide prevalent and serious issue which increases the failure of treatment outcomes and leads to high mortality. Considering that the increased resistance to systemic antimicrobial therapy often needs of the use of more toxic agents, topical antimicrobial therapy emerges as an attractive route for the treatment of infectious diseases. The topical antimicrobial therapy is based on the absorption of high drug doses in a readily accessible skin surface, resulting in a reduction of microbial proliferation at infected skin sites. Topical antimicrobials retain the following features: (a) they are able to escape the enzymatic degradation and rapid clearance in the gastrointestinal tract or the first-pass metabolism during oral administration; (b) alleviate the physical discomfort related to intravenous injection; (c) reduce possible adverse effects and drug interactions of systemic administrations; (d) increase patient compliance and convenience; and (e) reduce the treatment costs. Novel antimicrobials for topical application have been widely exploited to control the emergence of drug-resistant microorganisms. This review provides a description of antimicrobial resistance, common microorganisms causing skin and soft tissue infections, topical delivery route of antimicrobials, safety concerns of topical antimicrobials, recent advances, challenges and future prospective in topical antimicrobial development.

Antimicrobial and toxicological evaluations of binuclear mercury(ii)bis(alkynyl) complexes containing oligothiophenes and bithiazoles

We investigated the antimicrobial activity of bis-(alkynyl)mercury(ii) complexes with oligothiophene and bithiazole linking units against MRSA and C. albicans, and their cytotoxicity was tested on NIH 3T3 cells.

Activation of the quadriceps muscle during semisquatting with different hip and knee positions in patients with anterior knee pain

OBJECTIVE

We measured the surface electromyographic activities of vastus medialis obliquus and vastus lateralis in 16 subjects with patellofemoral joint pain syndrome.

DESIGN

Each subject performed bilateral static knee extension exercises at 60% of his or her maximal voluntary effort under different combinations of hip rotation (30 degrees of medial rotation, neutral, 45 degrees of lateral rotation) and knee flexion (20 and 40 degrees) in a standing position. The ratio of surface-integrated electromyographic signals of vastus medialis obliquus over vastus lateralis was calculated for each of the six conditions. Because of significant interaction of hip rotation and knee flexion in the two-way analysis of variance, data were analyzed separately with paired t tests for the effect of knee positions and one-way repeated measures analysis of variance for hip positions.

RESULTS

At 20 degrees of knee flexion, there was no significant difference among the three hip positions, whereas at 40 degrees of knee flexion, medial rotation of the hip resulted in significantly higher vastus medialis obliquus over vastus lateralis activity ratio than lateral rotation (P < 0.05).

CONCLUSIONS

There was relatively more activation of vastus medialis obliquus than vastus lateralis at 40 degrees of semisquat with the hip medially rotated by 30 degrees. This finding has clinical implications for training the vastus medialis obliquus in patients with patellofemoral joint pain syndrome.

ELISA seropositivity for Toxocara canis antibodies in Malaysia, 1989-1991

The laboratory test results for visceral larva migrans (VLM) using ELISA for Toxocara canis antibodies employed by the Institute for Medical Research, Kuala Lumpur, is described. A total of 331 serum samples received from hospitals and general practitioners all over Malaysia were tested. The test utilises excretory-secretory antigens obtained from in vitro culture of second stage T. canis larvae. The overall seropositivity rate was 19.6%, the highest positive rate being in Indians (35.5%), followed by the Malays (14.8%), Chinese (10.9%) and others (29.4%). Seropositivity rate was highest in children below the age of 10; 89% of patients presented with eosinophilia and 93% with VLM syndrome were children.

Seroprevalence of Toxocara canis antibodies among Orang Asli (aborigines) in Peninsular Malaysia

An enzyme-linked immunosorbent assay using excretory-secretory antigens of the second stage larvae maintained in vitro was used to determine the seroprevalence of Toxocara antibodies in Orang Asli (aborigines) of Peninsular Malaysia. The mean + 3 SD optical density of 30 healthy subjects was used as the cut-off point. Overall prevalence was found to be 31.9%. No significant relationship was found between positive rates with sex and age groups, though children between 0 to 9 years recorded the highest positive rates. Eosinophil counts were found to be closely related to the proportion of positivity to toxocaral infection and mean optical densities. There was some degree of cross-reaction with Trichuris trichuria positive sera.

Antifilarial activity of intravenous suramin and oral diethylcarbamazine citrate on subperiodic Brugia malayi in the leaf-monkey, Presbytis cristata

The known filaricides, suramin and diethylcarbamazine citrate, were tested against subperiodic Brugia malayi infection in the leaf-monkey, Presbytis cristata. As expected, intravenous suramin at 10 mg/kg daily x 5 days or 17 mg/kg weekly x 5 weeks, did not show any microfilaricidal activity, but substantially reduced the recovery of live adult worms to 50.6% and 13.6% of controls respectively. Oral diethylcarbamazine citrate at 6 mg/kg daily x 6 or 10 days reduced final microfilarial counts to 30% of initial counts four weeks post-treatment and adult worm recovery was reduced to 4.5% and 0% of controls respectively. Although the antifilarial activity of these drugs against the infection in this non-human primate model appears to be similar to that seen in man, these results have to be confirmed using larger groups of animals.

Experimental infection of the leaf-monkeys, Presbytis cristata and Presbytis melalophos with subperiodic Brugia malayi

The leaf-monkeys, Presbytis cristata and Presbytis melalophos, experimentally infected with subperiodic Brugia malayi, have been used for studies on the pathoimmunology of the infection and the screening of potential filaricides during the last 6-8 years, and considerable information on the pattern of microfilaraemia and adult worm recoveries have been obtained. The prepatent periods in 97 P. cristata and 45 P. melalophos, each infected with about 200 infective larvae, were similar, these being approximately 70 and 68 days respectively. Although all infected animals became microfilaraemic, the peak geometric mean count was much higher in P. cristata than in P. melalophos, this being 182.0 and 65.8 per ml blood respectively. Mean adult worm recovery expressed as the percentage of the infective dose was 4.7% and 2.5%, respectively. Most worms were recovered from the sacral nodes/thoracic duct or inguinal lymph nodes in these animals. In view of the higher worm recovery and the higher peak microfilaraemia attained, it is concluded that P. cristata is a better model for the infection than P. melalophos.

Antifilarial activity of CGP 20376 against subperiodic Brugia malayi in the leaf-monkey Presbytis cristata

CGP 20376, a 5-methoxyl-6-dithiocarbamic-S- (2-carboxy-ethyl) ester derivative of benzothiazole was evaluated for its antifilarial properties and shown to be extremely effective against subperiodic Brugia malayi in the leaf-monkey, Presbytis cristata at oral doses of 20-100 mg/kg. The compound and/or its metabolites had complete micro- and microfilaricidal activities even when given at a single dose of 20 mg/kg. Lower doses had incomplete filaricidal action.

Experimental infection of the leaf-monkey, Presbytis cristata, with subperiodic Brugia malayi

Presbytis cristata monkeys infected through the inoculation of between 200 and 400 subperiodic Brugia malayi infective larvae (L3) in the right thigh, in both thighs or in the dorsum of the right foot were followed up for varying periods of up to about 8 months after infection. All 148 inoculated animals became patent, with mean prepatent periods being between 66 and 76 days. In animals injected in the thigh, the patterns of microfilaraemia were similar, there being a rapid rise in the geometric mean counts (GMCs) of microfilariae during the first 10-12 weeks of patency, which then plateaued at levels of greater than 1000/ml. Adult worm recovery, expressed as the percentage of the infective dose, was significantly higher in animals injected with 100 L3 in each thigh, being 9.4% as compared with 2.8%-4.8% in other groups. It is therefore recommended that animals should be injected with 100 L3 in each thigh and that the testing of potential filaricides in this model be carried out during the phase of rapid increase in microfilaraemia to ensure that any microfilaricidal effect can easily be detected.

Effect of ivermectin against subperiodic Brugia malayi infection in the leaf monkey, Presbytis cristata

Ivermectin at single doses of 0.2-1.0 mg/kg body weight reduced the microfilarial counts of subperiodic Brugia malayi in Presbytis cristata by 59.9%-89.6% of initial counts, 4 weeks after treatment. Adult filaricidal activity was poor, live adult worms being recovered from all animals at autopsy. There was no serious side effect at these doses.

Chemoprophylactic studies with ivermectin against subperiodic Brugia malayi infection in the leaf monkey, Presbytis cristata

Four Presbytis cristata were treated with oral ivermectin at the same time as the subcutaneous inoculation of 100 infective larvae monthly for three months. Two animals given 0.2 mg/kg monthly and two others given 0.3 mg/kg monthly as well as three control animals became patent for microfilaraemia. However, only 1% of the infective dose was recovered as adult worms from animals in the higher drug dosage group compared to 8.2% and 6.2% in the lower dosage and control groups respectively.

Diffusion-in-gel enzyme-linked immunosorbent assay, ELISA and IFA test in the detection of malarial antibodies

Malarial antibodies in 80 patients were measured using the diffusion-in-gel enzyme linked immunosorbent assay (DIG-ELISA), enzyme-linked immunosorbent assay (ELISA) and the indirect fluorescent antibody (IFA) test. Good correlations were obtained between all three tests in terms of sensitivity and reliability. DIG-ELISA has the advantage of being a rapid diagnostic tool for the detection of malarial antibodies.

Parasitological and serological surveys for malaria among the inhabitants of an aborigine village and an adjacent Malay village

Malaria surveys in an Orang Asli (aborigine) and an adjacent Malay village showed significantly higher parasite rates in the age-group 0-9 years in the former. Parasite rates declined progressively from a maximum at 0-4 years in the Orang Asli to zero at 30-39 years while in the Malays it rose progressively with age. Indirect fluorescent antibody test (IFAT) titres against schizont antigens of Plasmodium falciparum and P. cynomolgi were higher in the Orang Asli in all age-groups with a statistically significant inverse relationship between IFAT titres and parasite rates. IFAT titres in the Malay population also increased with age but were very much lower. Antibody levels detected by the enzyme-linked immunosorbent assay (ELISA) using soluble schizont antigens were also much higher in the Orang Asli and values with P. cynomolgi were higher than those with P. falciparum antigens. These differences are attributed to the higher malaria transmission in the younger age-groups of the Orang Asli and presumably greater immunological experience to a wider diversity of antigens than the Malays, thus explaining the presence of "protective" antibodies in the former but not the latter group.