Ghazally Ismail

Resistance of Pseudomonas pseudomallei to Normal Human Serum Bactericidal Action

The effect of human normal serum (HNS) on Pseudomonas pseudomallei was determined. It is apparent from our data that the organism is resistant to the normal serum bactericidal mechanism. Ancillary experiments to confirm this serum‐resistant property of P. pseudomallei were done by examining the effects of growth phase conditions of the bacteria (i.e., logarithmic and stationary phases) and different buffered systems used as diluent in our bactericidal assay. Results obtained showed similar degree of resistance to serum bactericidal killing by 5 strains of the organisms tested. The possible survival advantage of serum‐resistant property to P. pseudomallei as bacterial pathogens known to invade the blood stream is discussed.

Inhibition of Macromolecular Synthesis in Cultured Macrophages by Pseudomonas pseudomallei Exotoxin

Pseudomonas pseudomallei exotoxin was found to be a potent inhibitor of protein and DNA synthesis in cultured macrophages. Inhibition of DNA synthesis occurred at toxin concentrations as low as 1–2 μg/ml and inhibition of 3H‐thymidine uptake was almost complete at concentrations of 8 μg/ml or more. A close correlation between cell damage and inhibition by DNA synthesis was observed. For protein synthesis, inhibition was obtained at much lower doses (0.06–2.0 μg/ml) of the toxin. At similar toxin concentrations, DNA synthesis was marginally affected. Further, it was shown that protein synthesis inhibition occurred almost immediately after incubation, reaching its maximal inhibitory effect of 70% after 6 hr. DNA synthesis, however, was minimally affected by a similar toxin concentration even after 10 hr of incubation. The inhibition of macromolecular synthesis in macrophages by P. pseudomallei exotoxin may be relevant to its modulatory effect on the host defense mechanism.

The distribution and abundance of the indo-pacific crocodile Crocodylus porosus Schneider in the Klias river, Sabah, East Malaysia

Abstract Twelve spotlight surveys for the Indo-Pacific crocodile Crocodylus porosus were carried out from June 1987 to July 1988 along an approximately 37-km stretch of the Klias River, Sabah, Malaysia. Crocodiles sighted were divided into three size classes: Class 1 (hatchlings and juveniles 3 m in length). Salinity and temperature readings were taken for each sighting and each location was mapped. A total of 182 crocodiles were sighted with densities in the range 1.1–3.6 km−1. Class 1 individuals were most frequently encountered (63.2%) followed by Class 3 (24.2%) and Class 2 (12.6%). Crocodiles were most abundant in the upper mangrove section of the river, while the distributions of Class 1 and Class 2 individuals differed significantly (t-test for non-paired samples, p≤0.05) with regard to location along the river. There were no significant differences in habitat salinity between classes although there were in water temperature (t-test for non-paired samples, p≤0.05) between Classes 1 and 3, with smaller crocodiles more frequently sighted at temperatures from 30–31°C. The population densities are higher than reported in 1984, but the structure reflects a population under pressure from hunting.

Prevalence of antibodies to Pseudomonas pseudomallei exotoxin and whole cell antigens in military personnel in Sabah and Sarawak, Malaysia

Sera from 420 military personnel serving in Sabah and Sarawk, Malaysia, were tested for antibodies to Pseudomonas pseudomallei exotoxin and whole cell antigens by enzyme‐linked immunosorbent assay procedure (ELISA). Data showed that 54.4% of serum samples were positive for antibodies to P. pseudomallei exotoxin and 65.7% were positive for antibodies to the whole cell antigens. Samples gave much lower titers for anti‐exotoxin antibodies compared to titers against crude whole cell antigens. The incidence of antibody to exotoxin was highest in the age groups ranging from 26 to 32 years, where the positive rates were higher than 40% and 30% for military personnel serving in Sarawak and Sabah, respectively.

An ELISA-disc procedure for antibodies toPseudomonas pseudomallei: application for a serological study of melioidosis in an endemic area

The optimization and development of an ELISA-disc procedure for the detection of antibodies to whole cell surface antigens and purified exotoxin ofPseudomonas pseudomallei is described. Comparison of the serum agglutination test (SAT), the serum based enzyme-linked immunosorbent assay (ELISA) and the ELISA-disc procedures used on goat and human sera demonstrated a high correlation in their ability to detect antibodies specific forP. pseudomallei antigens. A serological survey using the ELISA-disc method was carried out on a normal human population in Sabah, Malaysia, an area known to be endemic for melioidosis. The prevalances of antibodies towards cell surface antigens and exotoxin ofP. pseudomallei were 28% and 8%, respectively. As a procedure, the ELISA-disc technique reported here is technically simple and provides savings in costs and is thus deemed suitable for seroepidemiological surveillance of melioidosis in remote areas of South-East Asia.