Diss. (sammanfattning) Stockholm : Karolinska institutet, 2005. / Härtill 4 uppsatser.

A study to assess the potentials of some commensal bacteria that belong to Staphylococcus, Acinetobacter and Stenotrophomonas genera as reservoirs of antibiotic resistance determinants in the environment of Nkonkobe Municipality of the Eastern Cape Province, South Africa, was carried out using standard microbiological and molecular techniques. A total of 120 Staphylococcus isolates which consisted of Staphylococcus haemolyticus (30%), Staphylococcus aureus (23.3%) from pig; Staphylococcus capitis (15%) from goat; Staphylococcus heamolyticus (5%) and Staphylococcus xylosus (15%) from cattle and other Staphylococci (11%) from dead chicken and pigs were isolated. About 23.3% of these isolates were coagulase positive and 76.7% were coagulase negative. This difference in prevalence along coagulase production divide was statistically significant (p < 0.05). Eighty-six Acinetobacter species (Acinetobacter baumannii/calcoaceticus and Acinetobacter haemolyticus) were also isolated from Alice and Fort Beaufort towns samples, while 125 Stenotrophomonas maltophilia isolates were from grass root rhizosphere (96%) and soil butternut root rhizosphere (4%). Between 75-100% of the Staphylococccus species were resistant to Penicillin G, tetracycline, sulphamethaxole and nalidixic acid; about 38 % were methicillin resistant, consisting of 12.6% methicillin resistant Staphylococcus aureus (MRSA) from pig and a total of 12% vancomycin resistant were observed. Also, 12% of the isolates were erythromycin resistant while 40.2 % were resistant to the third generation cephalosporin, ceftazidime. The antibiotic resistance genes vanA, VanB, eryA, eryB, eryC were not detected in all the phenotypically resistant Staphylococccus species, but mec A gene and mph genes were detected. In the Acinetobacter species, a wide range of 30-100% resistance to penicillin G, ceftriazone, nitrofurantoin, erythromycin, and augmentin was observed. Polymerase chain reaction (PCR) revealed the presence of Tet(B) and Tet(39) genes in these species, while Tet (A), Tet(M) and Tet(H) were absent. Also, 9.3% of the Acinetobacter species showed phenotypic production of extended spectrum beta lactamases (ESBLs) while 3.5% were positive for the presence of blaCTX-M-1 genes. The Stenotrophomonas maltophilia isolates showed varying resistance to meropenem (8.9%), cefuroxime (95.6 %), ampicillin-sulbactam (53.9%), ceftazidime (10.7%), cefepime (29.3 %), minocycline (2.2%), kanamycin (56.9%), ofloxacin (2.9%), levofloxacin (1.3%), moxifloxacin (2.8%), ciprofloxacin (24.3%), gatifloxacin (1.3%), polymyxin B (2.9 %), cotrimoxazole (26.1%), trimethoprim (98.6%), aztreonam(58%) and Polymyxin B (2.9 %). The isolates exhibited significant susceptibility to the fluoroquinolones (74.3-94.7 %), polymycin (97.1%) and meropenem (88.1%). Only sul3 genes were the only sulphonamide resistance gene detected among the trimethoprim-sulphamethoxazole resistant isolates. The observed multiple antibiotic resistance indeces (MARI) of >2 for Staphylococcus species, Acinetobacter species and Stenotrophomonas maltophilia suggest that they have arisen from high-risk sources where antibiotics are in constant arbitrary use resulting in high selective pressure. The presence of tetracycline resistance genes in Acinetobacter species justifies the observed phenotypic resistance to oxytetracycline and intermediate resistance to minocycline. High phenotypic resistance and the presence of some resistance genes in Staphylococcus species is a possible threat to public health and suggests animals to be important reservoirs of antibiotic resistance determinants in the environment. Indiscriminate use of antibiotics induces this kind of antibiotic resistance and should be discouraged. Personal hygiene is encouraged as it reduces the load of Acinetobacter species contacted from the environment that may be difficult to control. Commensal Stenotrophomonas maltophilia are as important as their clinical counterparts due to their roles in opportunistic infection, antibiotic resistance and their associated genes, especially sul gene. Personal hygiene is hereby advocated especially when in contact with soil, plants and plants’ rhizospheric soil

Variovorax paradoxus EPS is a gram-negative rod isolated from the sunflower rhizosphere at CSUSB. Preliminary research has shown that Variovorax paradoxus EPS has anti-staphylococcal activity in liquid and solid co-culture. Anti-staphylococcal activity of Wild type and V. paradoxus EPS 𝚫4519 on 0.5% YE agar with embedded S. aureus AH1710 supports the idea that a soluble molecule is responsible for this activity, as the agar acted as a physical barrier between V. paradoxus EPS and S. aureus colonies. Preliminary genetic analysis of V. paradoxus EPS identified three loci that suitable candidates for the synthesis of a potential anti-staphylococcal small molecule. Preliminary data failed to detect expression at two of the three identified loci and a strain with a mutation at the third locus continues to produce anti-staphylococcal activity. We hypothesize that the microbial agent is expressed at a different locus or loci that have not yet been identified. These gene products are responsible for the synthesis of the microbial agent and are controlled by exposure to Staphylococcus aureus. Optimal growth conditions were identified for V. paradoxus EPS and S. aureus to demonstrate the formation of a zone of inhibition on Tryptic Soy Agar. The use of a V. paradoxus EPS Δ 4519 transposon library at optimal growth conditions allowed us candidate mutants with altered antimicrobial activity phenotypes. We identified 28 insertion sites that resulted in altered antimicrobial activities, which will allow us to identify the genes involved in this biosynthetic pathway.

No description available.

Recently a whole cell based biosensor has been developed in our laboratory that consists of a monolayer of human umbilical vein endothelial cells (HUVECs) on the asymmetric cellulose triacetate (CTA) membrane of an ion selective electrode (ISE). When a confluent cell monolayer is formed across the membrane, response from the sensor is inhibited due to inhibited ion transport across the membrane. When the cell based biosensor is exposed to permeability modifying agents, the permeability across the cell monolayer is altered facilitating more ion transport and as a result the response from the sensor increases. This sensor response can be related to the concentration of these agents. One objective of this research was to investigate the ability of the sensor to detect a physiological toxin, alpha toxin from Staphylococcus aureus. Studies demonstrated that the biosensor can detect 0.1ng/ml alpha toxin. Considering the fact that the concentration of this toxin is 100-250 ng/ml in whole blood in humans, this biosensor has the ability to act as the diagnostic tool for staphylococcal diseases. Another part of this research was to investigate the ability of the biosensor to measure angiogenesis by measuring the changes in permeability induced by cytokines such as vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), hepatocyte growth factor (HGF) and tumor necrosis factor andamp;aacute; (TNF- andamp;aacute;) individually and in combination. The sensor response was then compared with the common in vitro assays for angiogenesis. The study demonstrated that at the concentrations studied the sensor response in the presence of cytokines was much higher than that observed for other angiogenesis assays, thereby bolstering the potential of the biosensor to act as a quick screening tool for angiogenesis. Furthermore, epithelial cell based sensor responses to the same cytokines were compared with the responses from endothelial cell based sensor and the mechanisms behind the increased sensor response were elucidated. Finally, to investigate the ability of the sensor to screen cancer, the biosensor was exposed to the serum from healthy individuals and cancer patients. The results showed that the sensor can distinguish between healthy individuals and cancer patients and the results correlate with the stages of cancer.

Thesis (D.P.H.)--University of Hawaii at Manoa, 1991. / Includes bibliographical references (leaves 157-168). / Microfiche. / xiii, 168 leaves, bound ill. 29 cm

Thesis (M.Sc.) -- Memorial University of Newfoundland. / Typescript. Bibliography: leaves 80-86. Also available online.

Thesis (doctoral)--Utrecht, 1979.

It is the aim of this work to study the role, if any, of C'4 in the immune response against Staphylococcus aureus infections.

No description available.