The geography and freshwater ecology of Khuzestan and those human activities which affect the snail ecology are described. O. turkestanicum, S. bovis and S. haematobium were the only animal and human blood flukes found in Khuzestan. The molluscan hosts of both species of Schistosoma is B. truncatus whereas O. turkestanicum is transmitted by L. gedrosiana. The infection rate of O. turkestanicum in ruminants was high and causes considerable economic loss. The morphology of O. turkestanicum and its distinguishing characteristics from other schistosomes are discussed. The prevalence of O. turkestanicum and S. bovis infection in ruminants in Khuzestan abattoirs was studied. Infection rates of O. turkestanicum in cattle was higher than in sheep and goats. The intensity of O. turkestanicum in in naturally infected cattle and sheep was determined. Sheep suffered More than cattle from the disease. The intensity of O. turkestanicum declined with increasing age in cattle but increased in sheep. Experimental studies were carried out, on, calves, sheep, goats, and buffalo-calf infected with O. turkestanicum and S. bovis. The intensity, pathogenicity and pathology of O. turkestanicum and S. bovis in naturally and experimentally infected ruminants were compared. S. bovis caused more serious damage to ruminants than O. turkestanicum. In O. turkestanicum infections the duodenum was the most intensely involved organ and the liver was less affected and large intestine was free from infection. S. bovis was evenly distributed along the alimentary tract. Susceptibility of different species of rodents, carnivores and birds to O. turkestanicum were tested. Only Tatera indica (a wild local rodent ) was found to be susceptible to O. turkestanicum infection. Carnivores and birds were resistant to infection. In the heterologous immunity experiments mice were immunized with different numbers of O. turkestanicum cercariao and challenged with S. bovis, S. haematobium and S. mansoni. Homologous immunity was also studied in mice with S. bovis. In these experiments mice produced a partial protection against the challenge infections. Reciprocal heterologous immunity experiments were carried out in calves and sheep using S. bovis and O. turkestanicum. Calves showed a high degree of protection but the effect was poor in sheep. Calves immunized with repeated inoculations of S. haematobium cercariae developed some immature worms and produced considerable resistance against challenge infection with O. turkestanicum and S. bovis. Calves also developed a considerable immunity in homologous system with and. O. turkestanicum and S. bovis. Studies were carried out on the distribution and ecology of Lymnaea gedrosiana the intermediate host of O. turkestanicum in Khuzestan. Detailed studies were made on the population dynamics of this snail by fortnightly surveys in different type of habitats over a Period of 12 months. The results showed that peaks of snail population occurred in 2 seasons, spring and autumn. Transmission occurred throughout the year in Canals; in spring, summer and autumn in swamps; in spring and autumn in ponds. Canals and swamps accessibl to livestocks were found to be important transmission sites of O. turkestanicum. Laboratory experiments were carried out to study the develop of larval stages of O. turkestanicum in L. gedrosiana after the snails had been exposed to various number of miracidia. The results showed that the miracidial exposure dosage did not affect the cercarial prepatent period, but the life-span of infected snails was shorter and all the snails exposed to 20 miracidia each shed fewer cercariae than those exposed to 5-20 miracidia.

1. The infectivity of three strains of Leishmania braziliensis pifanoi, strain V1 and V2 from Venezuela and L 15 from Brazil was studied in albino, hairless, "shaven" and "shaven" x albino mice; in hamsters, rats and guinea pigs. Rats and guinea-pigs were not susceptible, Hamsters were more susceptible to infection than mice. Hairless and "shaven" mice were more readily infected than albino or "shaven" x albino. On intradermal inoculation, amastigotes were more effective than promastigotes in establishing infection. The size of the lesion and the extent of metastasis were directly proportional to the dose of inoculum: the incubation period was inversely proportional to the dose of inoculum. Primary and secondary lesions were restricted to hairless parts of the body. The appearance of the primary lesion and metastasis to other parts of the body was followed in mice and hamsters:- Intraperitoneal inoculation led to the involvement of the scrotum in 2 out of 6 hamsters and 11 out of 32 mice. Intracardioc inoculation resulted in diffuso infection in 4 out of 4 "shaven" mice, and in none of the hairy mice (albino or hybrid). Intradermal, intraperitoneal and intrasplenic inoculation with the parasite did not lead to visceral involvement. Age and sex were not found to play an important role in influencing the course of infection. 2. The effect of the environmental temperature on the course of infection in mice was studied. In mice adapted to live at -15ºC, no lesion developed, but when these mice were transferred to 4°C lesions developed as in the control kept at room temperature. Mice and hamsters inoculated with the parasite and kept at 4ºC showed a normal course of infection. When mice with active lesions were kept at 36.5°C, the parasites disappeared from the infected histiocytes within 26-39 hours and the lesions healed within 27 - 35 days. 3. The histiopathological picture of the disease was studied in mice and hamsters. The lesions consisted mainly of a histiocytic granuloma in the dermis extending into the subdermis and sometimes into the epidermis in the 'form of a micro abscess. In the secondary lesions tho subpapillary zone of the epidermis, which normally is clearly demarkated from the dermis, may become invaded with parasites. The mucous membranes and cartilage of the ears usually remain free from infection, but the regional lymph nodes were found to become involved. 4. Attempts were made to attenuate the parasite by exposure to gamma-irradiation in order to use it as a vaccine. However, parasites exposed to from 6.5 to 17.5 Kilo rads retained their normal infectivity in mice.

The rotation of the use of chemically unrelated insecticides has been advocated to delay the build up of resistance. To examine this concept in the laboratory, Anopheles albimanus and Culex guinquefasciatus were subjected to two kinds of rotational selection which may be referred to as short term pre-planned rotation and "opportunistic" rotation. No difference was observed between these two methods in term of the time for each resistance level to reach 5Q%. The effectiveness of selection for resistance depends on the protection conferred by resistance genes and this was tested by laboratory releases of the DDT resistant and susceptible homozygotes and heterozygotes of An. gambiae into DDT sprayed and unsprayed miniature huts. All the genotypes were killed with freshly applied DDT but survivors were observed from month 2, 3 and 5 onwards for RR, RS and SS genotypes, respectively. Persistence of DDT on the sprayed wall and roof of the mud hut was studied by bioassays and biochemical assays on scrapings from the wall and roof. Linkage between resistance genes could effect the rotational use of insecticides. No linkage was found between propoxur and dieldrin resistance genes by combining bioassay and biochemical methods. As a preparation for a field studies in Malaysian field collected Aedes aegypti and Culex guinguefasciatus larvae were selected with temephos and Bti. Cx guinguefasciatus responded to temephos selection but Ae. aegypti did not respond to temephos and neither species responded to Bti selection. ~ Caged adults were exposed to thermal fogging in the field. The partially resistant Cx guinguefasciatus strain hardly survived any better than susceptible strains. Resistant and susceptible larvae were exposed to water samples from containers which had been treated with temephos sand granules. 100% mortality was obtained for all the strains up to week 6. Resistant Culex started to survive at week 7 but susceptibles did not do so until week ten. The prospects for the various proposed strategies for resistance management are discussed.

The effect of various factors on the infectivity of the cercariae of S. mansoni and S. haematobium were studied. It has clearly been shown that the infectivity of cercariae of both species is directly influenced by those factors. Almost equal proportions of cercariae of both species died or were severely damaged during penetration of mammalian host. skin: 24-48% died in mouse skin compared with only 11-19% in hamster skin. These differential losses in the skin of different hosts account for the fact that hamsters yield higher adult worm. recoveries than mice. However, adult worm recoveries from animals infected with S. haematobium cercariae were much less, almost one third, than those from S. mansoni infections. Young mice were more susceptible to S. mansoni than old mice and this was mainly due to the low level of mortality of cercariae during penetration of young mouse skin. More cercariae of S. mansoni died, at lest during the early stages of penetration, in the skin of infected animals than in the skin of normal previously non-infected animals. It is very difficult to explain this observation; it could be related to the immune state of the host or to local reaction, provoked by previous exposure to cercariae, at the site of penetration. No difference was found in the susceptibility of male or female mice to S. mansoni but male hamsters were more susceptible to S. haematobium than female hamsters. The percentages of S. mansoni and S. haematobium cercariae which die, during penetration of host skin, steadily increased with increase in the post-emergence age of the cercariae and this accounted for the observed decline in infectivity which accompanied ageing of the cercariae. It has been demonstrated that death of S. mansoni cercariae during penetration of host skin is probably due to the exhaustion of their stored energy reserves. Ultra-violet irradiation affected the infectivity of cercariae of S. mansoni and S. haematobium by increasing the level of mortality of cercariae in the skin and delaying their migration in the lungs beyond days 3-4 postinfection. Gamma irradiation also inhibited the development of S. mansoni cercariae to the adult stage : cercariae were mainly destroyed in the liver although some form of damage occurred in the lungs as well. Maintenance of cercariae of S. mansoni and S. haematobium at low or high temperatures increased their mortality in the skin and consequently resulted in a marked reduction in the worm burdens of animals infected with these cercariae. Treatment of S. mansoni cercariae with sublethal concentrations of niclosamide (Bayluscide) had the same effect as temperature. The in vivo development of S. haeratobium was also studied. It followed the same general pattern as for S. mansoni and S. japonicum: six stages of development, characterized by morphological and histochemical criteria, were distinguished. However, the development of S. haematobium was slower (61-63 days) than S. mansoni (34-35 days) or S. japonicum (23-29 days).

Studies on the effects of ambient temperature on the course of salivarian trypanosome infections in mice showed that the mortality of infected animals was influenced by the environments in which they were maintained. Virulent strains of T. (N. ) congolense and T. (T .) brucei caused mild and chronic infections when infected animals were maintained at high (35°C) ambient temperature; T. (D. ) vivax and T. (T. ) evansi inoculated mice either failed to become parasitaemic or developed transient infections at this temperature. Infections became rapidly fatal when T. (T.) brucei infected mice were transferred from 35°C to normal room temperature (22-27°C). Mice kept at the high ambient temperature had significantly higher (39.3°C) mean body temperature than (37.5°C) mice kept at room temperature. They suffered a big weight loss and their spleen weights were comparatively much smaller than mice kept at 22-27°C. Monomorphic strains of T. (N. ) congolense and T. (T ) brucei became pleomorphic when inoculated mice were maintained at 35°C. At this temperature, the infectivity of T. (T. ) brucei was not altered, it reacquired its capability to produce variants and was able to develop in salivary glands of Glossina. It became highly pleomorphic when inoculated into chick embryos incubated at 39 °C but not at 37°C. The morphological changes were thought to be a direct heat effect on the trypanosome organisms. Attempts to find tissue phase of T. (T. ) brucei and T.(T. ) evansi during chronic infections in mice kept at high ambient temperature was unsuccessful, neither was there any evidence that these species could develop in mouse peritoneal macrophages. The presence of released antigens in T. (T. ) brucei infected mouse serum was demonstrated only at certain parasitaemic level Anti log 8 trypanosomes/ml). Infected serum obtained from mice ( kept at 35°C was less immunogenic than that obtained from parasitaemic mice kept at room temperature. Many bizarre forms of T. (T. ) brucei appeared when infected mice kept at 35°C had previously been immunosuppressed (x-irradiated or cyclophosphamide treated). These mice had very high parasitaemias. However, treatment with Betamethasone or anti-lymphocyte serum failed to produce the same effect. Fewer antibody producing cells was observed in mice kept at 35 °C than in those kept at control conditions. It is suggested that the enhanced resistance to trypanosome infections observed in mice kept at 35°C is due to direct effect of temperature on trypanosomes.

Neisseria meningitidis causes over 1 million cases of meningitis and septicaemia annually. Currently available vaccines show only poor immunogenicity in children and do not induce immunological memory. The main focus of this study was on exploring the organism by mass spectrometry and 2-D GE to attempt to identify potential biomarkers and get a better understanding of the biology of N. meningitidis. A novel diagnostic approach using SELDI TOP MS was developed and a number of different approaches to mass spectral data mining were investigated. Several species specific, and some serogroup specific, putative biomarker for TV! meningitidis were identified. The ability of ANNs to interrogate SELDI TOP MS data and identify delineating bacterial biomarkers was evaluated and an ANN model was developed for N. meningitidis displaying 100% sensitivity and 99% specificity. A novel technique for sequence typing, based on mass spectrometry, was developed showing full correlation with the established MLST method. Partial 2-D GE reference maps for serogroup A, B and C were created showing between 63 and 85 annotated protein species. The majority of identified protein species were involved in common metabolic pathways. However, several hypothetical proteins were detected. The technologies applied show great potential for future investigations into the subpopulations of this pathogen. Overall, the results demonstrated that future approaches to study the biology of this pathogen should be polyphasic, combining genomic and proteomic analyses to provide a more holistic overview of strains. Such an approach will likely enable new stable targets to be identified from which a strategic therapeutic approach may be devised.

Lipopolysaccharide (LPS) is a major consituent of the outer membrane of all Gram-negative bacteria and is known to be responsible for the range of pathophysiological features of endotoxic shock. This thesis considers the expression of <i>Escherichia coli</i> LPS under different environmental conditions and its detection in the serum of septic patients by means of monoclonal antibody (MAb) probes. From an existing panel of MAbs, reactive with either Lipid A, core oligosaccharide and O-polysaccharide components of LPS, eleven were selected and characterised in a number of assay systems. Immunoblotting established that core reactive MAbs were reactive against either core not substituted with O-antigen or both substituted and unsubstituted core material. Core-glycolipid reactive MAbs demonstrated either full cross reactivity against all <i>E. coli</i> core types, or preferential binding to selective <i>E. coli</i> core types. Flow cytometric and ELISA analysis on whole bacteria showed that the absence of O-antigens on rough mutants increased accessibility of core-glycolipid LPS to antibodies. Analysis of the whole cell ELISA technique established that the expression of whole cells on ELISA plates differed from those in suspension. Sandwich ELISA methods employing suitable combinations of solid phase and biotinylated secondary MAbs were developed for the detection of <i>E. coli</i> types R1-R4, specific core types R1 and R3 and <i>E. coli</i> O18, O-antigen. The sensitivity of the assay using the two most cross-reactive MAbs was between 0.01 and 10 ng ml<SUP>-1</SUP> <i>E. coli</i>, depending on the core type. The sensitivity of assays for the detection of specific core and O-types was between 0.01 and 0.1 ng ml<SUP>-1</SUP> <i>E. coli</i> LPS. Assay sensitivity was significantly reduced for the detection of LPS in spiked serum. Methods to improve the sensitivity were investigated.

Mechanisms of resistance of <I>Pseudomonas aeruginosa</I> to 4-quinolones were investigated by examining the outer membrane proteins and DNA gyrases of resistant clinical isolates. Minimum inhibitory concentrations (MIC) were determined for fluoroquinolones, imipenem, β-lactams, gentamicin and tetracycline. Ciprofloxacin was the most active quinolone followed by ofloxacin and norfloxacin. Resistant clinical isolates had an MIC to ciprofloxacin of 4mg/l or greater, and resistance was shown to be stable after 20 passages on nutrient agar in all but one of the isolates. In several isolates cross resistance with imipenem and β-lactams was seen. All clinical isolates were resistant to tetracycline. Outer membrane profiles of sensitive and resistant strains of <I>P.aeruginosa</I> were examined and shown to be variable. In highly resistant strains, resistance to 4-quinolones could not be attributed to a particular membrane protein alteration as the isolates were not paired. Low level quinolone resistance in a series of paired isolates was linked with an increase in expression of a 48kD protein, and ceftazidime resistance with the appearance of a 42kD protein. These proteins were found to be non-covalently associated with peptidoglycan suggesting that they may function as porins. DNA gyrases from 22 clinical strains were isolated from a novobiocin/sepharose column and assayed by electrophoresis. The level where quinolones inhibited 50% of DNA gyrase supercoiling activity on relaxed pBR322 (IC<SUB>50</SUB>), was determined for ciprofloxacin, ofloxacin and norfloxacin in all strains. In general the IC<SUB>50</SUB> concentrations were equivalent to or greater than, the MIC of each drug.

It has been suggested that ankylosing spondylitis (AS) is a form of reactive arthritis similar to that observed among patients with genitourinary or intestinal infections. This hypothesis was supported by several studies which found an increased isolation rate of <i>Klebsiella</i> species from the stools of AS patients. The strongest known association of a human leucocyte group A antigen (HLA) with disease is observed with HLA-B27 and AS. One hypothesis proposed to explain this association is molecular mimicry, in which antigenic similarities between HLA-B27 and arthritogenic bacteria lead to a cross-reacting immune response and inflammation. Non-secretion of ABO blood group substances, an autosomal recessive characteristic, is another factor associated with susceptibility to disease, particularly to infection of mucosal surfaces. In a study in 1987, non-secretors were found to be over-represented in patients with AS, evidence which supported the hypothesis of an infectious aetiology in AS. The aims of this work were to reassess the association of non-secretion with AS; to study the faecal flora in a cohort of patients with spondylarthropathy; to determine the prevalence of bacteria expressing antigens cross-reactive with the HLA-B27 antigen; to examine the humoral responses of patients and controls to their own faecal flora; and to correlate these findings with the disease activity of the patients as assessed clinically and by the erythrocyte sedimentation rate and C-reactive protein as laboratory parameters of inflammation. The proportion of non-secretors in this AS population was identical to that in the control population when determined by haemagglutination inhibition assay and confirmed by an enzyme-linked immunosorbent assay (ELISA) for Lewis antigens. Careful scrutiny of the secretor status in a group of patients examined in both present and initial studies revealed that 27% of non-secretors in the previous survey had been wrongly typed and were indeed secretors.

Patients with insulin-dependent diabetes mellitus (IDDM) (n = 231) or non-insulin dependent diabetes mellitus (NIDDM) (n &61 205) were selected as models for investigation of oral yeast infection in immunocompromised host. The general objectives were: 1. to assess the contributions of genetic and environmental factors to colonization by yeast and development of denture stomatitis; 2. to assess the effects of the differential distribution of H and Lewis blood group antigens on epithelial cells of secretors and non-secretors on attachment of <i>C. albicans</i>. Predisposing factors contributing to colonization and development of denture stomatitis are distinct for individuals with IDDM compared with those with NIDDM. By multivariate analyses, palatal and overall oral carriage of yeast among individuals with IDDM was associated with age (p < 0.01). The factor contributing to palatal carriage of yeasts among individuals with NIDDM was poor glycaemic control (p &60 0.05); carriage in the oral cavity as a whole was influenced additionally by non-secretion of ABH blood group antigens. Introduction of a denture altered the risk factors. For individuals with IDDM, overall oral carriage was associated with the presence of retinopathy (p < 0.05) and palatal carriage by poor glycaemic control (p < 0.05) and age (p < 0.05). For those with NIDDM palatal carriage was associated with continuous presence of the denture (p < 0.01) and overall oral carriage with raised plasma glucose levels (p < 0.05). Denture stomatitis was associated with poor glycaemic control among subjects with IDDM and for those with NIDDM with continuous wearing of dentures, large numbers of yeasts and non-secretion. Host pathogen interactions underlying the increased susceptibility of non-secretors to colonization were explored. Buccal epithelial cells (BEC) from secretor and non-secretor donors were assessed by flow cytometry for their ability to bind yeasts. <i>C. albicans</i> 2346 which expresses an adhesion that binds fucose, the immunodominant sugar of the H and Lewis blood group antigens, was used. There was a trend for BEC from non-secretors to bind more <i>C. albicans</i> 2346 compared with BEC from secretors. These results suggested that Le<SUP>a</SUP> antigen present at higher levels on cells from non-secretors might be one of the receptors for <i>C. albicans</i> 2346.