A majority of cases of preventable and/or curable ocular morbidity and blindness are caused by ocular infections. They may account for 70 to 90% of all ocular morbidity seen by family doctors, general practitioners, health centers, and local ophthalmologists in both developed and developing countries. Unfortunately, most health authorities and doctors, including ophthalmologists, consider these diseases to be of little or no importance because they are not fully aware of the high prevalence of these infections and the blinding sequelae which may occur following incorrect diagnosis and treatment. Also, they are not aware of the social and economic impact of these infections in the absence of proper management and implementation of preventive measures. In this review, we examine present knowledge of chlamydial and common viral ocular infections. We discuss the problems of diagnosis, management, and prevention and propose solutions relevant to developed and developing countries.
Dermatophytoses are superficial infections caused by a group of fungi, the dermatophytes, which invade keratinized tissue of skin, hair, and nails in humans and animals. The importance of normal immune function in resistance to dermatophytoses is substantiated by an increased susceptibility to chronic infection seen in patients with impaired immunological responses. Humoral and cell-mediated immunities are both elicited during the infection. However, specific antibodies to dermatophytes do not seem to play a major role in protective immunity. On the other hand, the development of cell-mediated immunity during the infection is critical in eliciting resistance to the disease. For instance, resolution of the disease in both naturally and experimentally infected humans and animals correlates with the development of delayed-type hypersensitivity (DTH), whereas persistence of infection is frequently accompanied by poor in vitro blastogenic response and absent DTH. Furthermore, in experimentally infected mice, immunity to dermatophyte infection can be achieved by adoptive transfer of lymphoid cells, but not by serum, of infected donors. The present review includes an overview of published work and current research on the cellular events implicated in immunity to dermatophytosis. The role of humoral factors in such immunoregulation is also discussed.
Biological control of pests affecting the health of man and animals is practiced in various forms throughout the tropics. In this paper, the use of parasitic viruses, bacteria, protozoa, predatory arthropods, and fish against pests such as various mosquitoes, tse tse flies, and screwworm flies as published in the literature are reviewed. Mention is also made of the usefulness and applicability of the sterile insect technique, genetic control by chromosomal aberrations, and the exploitation of various incompatabilities. These are reviewed against the background of the present state of technology and limited resources that exist in many tropical countries. Most authors maintain that due to the relative length of time required to get a biological control system working efficiently, and the perennial nature of most tropical pest species, there is often the need to initially reduce the pest population by conventional means. There will thus be a balance between biological and chemical control in most systems. Emphasis is placed on meeting the urgent need for the exchange of research and development information on biological control of pests affecting man and his animals in the tropics.
The infrequent use of guinea pig in experimental syphilis, the not well genetically and immunologically characterized strains of animals originating from places with unspecified conditions of husbandry, and the various strains of Treponema pallidum used for infection provided inconsistent and discouraging results. For eight decades the rabbit has been the major animal model in studies of syphilis. However, the lack of readily available inbred strains of rabbits--necessary for adoptive transfer experiments--has been a stumbling block in revealing the mechanisms responsible for immunity, susceptibility, and resistance to T. pallidum infection. These difficulties have recently been overcome by demonstration of inbred strains susceptible to T. pallidum infection, paving the way to studies of adoptive immunity. The guinea pig may also be a better model than the rabbit for immunomanipulations (irradiation, injection with antibodies specific to various cell populations), allowing a closer insight into the immunopathologic mechanism operating during the course of syphilitic infection. The "rediscovery" of the guinea pig as a model for experimental syphilis and recent years of intensive studies justify a review summarizing older data and providing the most recent information. The authors, having first-hand experience with this model, will provide detailed information on (1) historical background; (2) course of infection with T. pallidum in inbred and outbred strains of guinea pigs; (3) the ID50 for various strains; (4) various routes of infection; (5) age and sex-dependent susceptibility to infection; (6) kinetic of the humoral response to specific and non-specific treponemal antigens; (7) appearance of autoantibodies and immune complexes; (8) cellular response, including lymphoproliferative response, macrophage inhibitory factor(s) production, chemotaxis and adoptive transfer of immunity by purified T cells; and (9) a complete list of references.
Although the first Aeromonas strain was described by Zimmermann as early as in 1890, it took 60 years until Caselitz established human pathogenicity of strains then called "Vibrio jamaicensis". Since then, and especially in the last 10 years, there have been increasing numbers of reports on different infections caused by members of the genus Aeromonas. These include sepsis; meningitis; cellulitis; necrotizing fasciitis; ecthyma gangrenosum; pneumonia; peritonitis; conjunctivitis; corneal ulcer; endophthalmitis; osteomyelitis; suppurative arthritis; myositis; subphrenic abscess; liver abscess; cholecystitis and/or ascending cholangitis; urinary tract infection; endocarditis; ear, nose, and throat infections; balanitis; etc. The role of Aeromonas in gastrointestinal disease is very controversial. Increasing epidemiological data suggest that these organisms play a major role in enteric infections, but so far enteropathogenicity has not been demonstrable in experiments where volunteers were given high numbers of Aeromonas possessing different virulence factors. Virulence factors include hemolysin(s), enterotoxin(s), hemagglutinins, invasivity, and others; but these are not found more frequently in strains isolated from patients with diarrhea than from healthy controls. Whether there is a correlation between species and disease remains to be elucidated and requires more information about the taxonomy of this genus.
During the last few years the studies about the physiology and bioenergetics of lactic acid bacteria during growth and starvation have evolved from a descriptive level to an analysis of the molecular events in the regulation of various processes. Considerable progress has been made in the understanding of the modes of metabolic energy generation, the mechanism of homeostasis of the internal pH, and the mechanism and regulatory processes of transport systems for sugars, amino acids, peptides, and ions. Detailed studies of these transport processes have been performed in cytoplasmic membrane vesicles of these organisms in which a foreign proton pump has been introduced to generate a high proton motive force.
Major advances have recently been made in understanding the molecular biology of the archaebacteria. In this review, we compare the structure of protein and stable RNA-encoding genes cloned and sequenced from each of the major classes of archaebacteria: the methanogens, extreme halophiles, and acid thermophiles. Protein-encoding genes, including some encoding proteins directly involved in methanogenesis and photoautotrophy, are analyzed on the basis of gene organization and structure, transcriptional control signals, codon usage, and evolutionary conservation. Stable RNA-encoding genes are compared for gene organization and structure, transcriptional signals, and processing events involved in RNA maturation, including intron removal. Comparisons of archaebacterial structures and regulatory systems are made with their eubacterial and eukaryotic homologs.
For the past ten years, several groups were engaged in synthetic studies of lipid A, namely the lipid portion of bacterial lipopolysaccharides (LPS) that has been assumed to be the bioactive center of LPS, but has not been unanimously approved. Among them, Shiba, Kusumoto, and colleagues, Osaka, Japan have synthesized most energetically and successfully a variety of counterparts of lipid As, biosynthetic lipid A precursors, and their analogs. The endotoxic and related bioactivities of these synthetic compounds were studied by Japanese and German groups, including ours. In 1985, one of the compounds, having an acylation and phosphorylation pattern in beta(1-6)-D-glucosamine disaccharide which was proposed for Escherichia coli F515 lipid A was found to be exhibit full endotoxic and related bioactivities identical to those of the bacterial product. The study was extended by synthesis and examination of bioactivities of variously acylated D-glucosamine di- and monosaccharide phosphates, which correspond to structural components of lipid As, and their analogs or derivatives. Thus, structural requirements have been fairly well elucidated. In this article, first we will review the progress of synthetic and biological studies, with particular emphasis on chemical structure--bioactivities relationships of lipid As, and then we will discuss possible usefulness of some less or nontoxic lipid A-related synthetic compounds in clinical and preventive medicine.
In pseudomonads, naphthalene is catabolized in a series of reactions to salicylic acid, which is further degraded via the catechol meta-cleavage, ortho-cleavage, or gentisic acid pathway to Krebs cycle intermediates. The naphthalene catabolic genes have been located on self-transmissible plasmids, in most cases, and implicated to have chromosomal locations in other cases. The best-studied naphthalene catabolic plasmid is NAH7. It carries two operons, one of which enables the host to utilize naphthalene and the other to utilize salicylate as a carbon and energy source. The product of another NAH7 gene, nahR, is required to turn on both operons in the presence of the inducer, salicylate. Several different naphthalene and salicylate catabolic plasmids have been shown to share sequence homology with NAH7. These plasmids can undergo structural alterations involving insertions and deletions during conjugations and changes in nutritional conditions. Available evidence suggests that salicylate catabolic plasmids can form from the naphthalene catabolic plasmids by structural alterations of the plasmid DNA. The gene organization and regulation, as well as the genetic instability of the naphthalene catabolic plasmids, are reminiscent of the TOL plasmids and suggest that the naphthalene catabolic plasmids and other catabolic plasmids may have evolved in a short period of time by acquiring and modifying preevolved gene clusters from host chromosomes or other plasmids.
The ability of bacterial pathogens to acquire iron in the host is an essential component of the disease process. Pathogenic Enterobacteriaceae spp. may either scavenge host iron sources such as heme or induce high-affinity iron-transport systems to remove iron from host proteins. The ease with which iron is acquired from the host will be at least partially determined by the iron status of the host at the time of infection. In response to infection, mammalian hosts reduce serum iron levels and withhold iron from the invading microorganisms. Thus the competition for iron is an active process which influences the outcome of a host-bacterial interaction.
Unlike bacterial viruses that infect cells bounded by a cell wall, mycoplasma viruses have evolved to enter and propagate in mycoplasma cells bounded only by a single lipid-protein cell membrane. In addition, mycoplasmas have the smallest amount of genetic information of any known cells, so their complexity is constrained by a limited genetic coding capacity. As a consequence of these host cell differences, mycoplasma viruses have been found to have a variety of structures and replication strategies which are different from those of the bacterial viruses. This article is a critical review of mycoplasma viruses infecting the genera Acholeplasma, Spiroplasma, and Mycoplasma; included are data on classification, morphology and structure, biological and physical properties, chemical composition, and productive and lysogenic replication cycles.
This review consists of three major sections. The first and largest section reviews the protein constituents and known properties of the phosphotransferase systems present in well-studied Gram-positive bacteria. These bacteria include species of the following genera: (1) Staphylococcus, (2) Streptococcus, (3) Bacillus, (4) Lactobacillus, (5) Clostridium, (6) Arthrobacter, and (7) Brochothrix. The properties of the different systems are compared. The second major section deals with the regulation of carbohydrate uptake. There are four parts: (1) inhibition by intracellular sugar phosphates in Staphylococcus aureus, (2) PTS-mediated regulation of glycerol uptake in Bacillus subtilis, (3) competition for phospho-HPr in Streptococcus mutans, and (4) the possible involvement of protein kinases in the regulation of sugar uptake via the phosphotransferase system. The third section deals with the phenomenon of inducer expulsion. The first part is concerned with the physiological characterization of the phenomenon; then the consequences of unregulated uptake and expulsion, a futile cycle of energy expenditure, are considered. Finally, the biochemistry of the protein kinase and the protein phosphate phosphatase system, which appears to regulate sugar transport via the phosphotransferase system, is defined. The review, therefore, concentrates on the phosphotransferase system, its functions in carbohydrate transport and phosphorylation, the mechanisms of its regulation, and the mechanism by which it participates in the regulation of other physiological processes in the bacterial cell.
Cryptosporidium is an enteric coccidial protozoan recognized in humans in 1976. Since its manifestation as an acquired immunodeficiency syndrome (AIDS)-related infection, new diagnostic techniques have improved recognition of Cryptosporidium oocysts, making apparent its true prevalence in human populations. Cryptosporidium represents 5 to 15% of all enteric pathogens in children in warm climate countries. It is responsible for both endemic and epidemic disease. Day-care center spread is well known, and evidence is strong for person-to-person transmission. The spectrum of illness caused by Cryptosporidium is broad, and while self-limited in immunocompetent individuals, gastrointestinal symptoms can be severe. Asymptomatic infection has been described in population surveys and outbreak investigations. Severe dehydration with malabsorption and failure-to-thrive in children from developing countries has been attributed to this organism. Intractable, incurable diarrhea can be fetal in immunosuppressed adults. Cryptosporidiosis in human immunodeficiency virus-infected individuals is declining in frequency in New York City, possibly reflecting changing sexual behaviors and comparatively low infectivity. No effective treatment for Cryptosporidium has been documented, but clinical trials are in progress.
Renewed interest in the acetone-butanol-ethanol (ABE) fermentation as a route for industrial production of butanol has been evident since the oil crisis of the 1970s. The present review includes an historical recap of the traditional industrial process and culturing practices useful in maintaining viable solvent-producing cultures, and then summarizes new and exciting research on the physiology and genetics of the microorganisms as well as process design. Most of these reports relate to improvements in solvent yield and the overall process, since traditional production is not efficient under present economic conditions. Conclusions are then made on future developments necessary for the establishment of an economically viable industrial process.
The potential application of liposomes to drug delivery has been apparent since 1965, when these phospholipid vesicles were first described by Bangham. Since then, experiments on animals have shown that liposome encapsulation can dramatically alter the distribution of drugs in the body and their rate of clearance. These pharmacokinetic differences, as well as other less well-understood effects, can result in reduced toxicity and enhanced efficacy of the encapsulated drug. The vast majority of studies on the therapeutic use of liposomes have involved the delivery of drugs used in cancer chemotherapy and metabolic storage diseases, but there is now more literature on the use of liposomes for the delivery of antimicrobial drugs and immunomodulating agents. This review briefly discusses the general properties of liposomes and the rationale for their use in antimicrobial drug delivery and immunomodulation, as well as the encapsulation of specific agents and the effect of encapsulation on the treatment of infectious diseases.
Widespread use of pesticides has no doubt benefited human beings in one way or another. However, their side effects on various organisms, including nontarget organisms, are largely overlooked. In the recent past, several studies have been done to assess the effects of pesticides on nontarget organisms, including microorganisms. Although pesticide effects on growth parameters of microorganisms have been extensively reviewed, little attention has been paid regarding their cytological and biochemical aspects. Therefore, the present work is mainly concerned with the cytological and biochemical aspects of pesticide microbiology. The effects of pesticides on photosynthesis, respiration, proteins, and nucleic acids are reviewed. Attention is also paid to their effects on cell morphology and morphogenesis and their effect on cell constituents.
The ability of bacterial pathogens to acquire iron in the host is an essential component of the disease process. Pathogenic Enterobacteriaceae spp. may either scavenge host iron sources such as heme or induce high-affinity iron-transport systems to remove iron from host proteins. The ease with which iron is acquired from the host will be at least partially determined by the iron status of the host at the time of infection. In response to infection, mammalian hosts reduce serum iron levels and withhold iron from the invading microorganisms. Thus the competition for iron is an active process which influences the outcome of a host-bacterial interaction.
Urease activity is a physiological function of many bacteria that enables these organisms to utilize urea as a source of nitrogen. The association of ureolytic bacteria with human or animal hosts varies widely from a commensal relationship as demonstrated with skin microflora, a symbiotic relationship in the gastrointestinal tract, to a pathogenic relationship in the urinary tract. Since similar or identical species of bacteria such as Staphylococcus aureus are found in all three environments, the effect of urease activity on the host must be solely a function of the environment of these organisms. In this review, the importance of urease to bacteria is discussed, identifying the gastrointestinal tract as a major reservoir of ureolytic bacteria and investigating the urinary tract environment and the infectious struvite stone production that often accompanies urease-producing bacteria there. Finally, an infection model is presented which explains the development and growth of these urinary calculi and their remarkable persistence in spite of modern urological treatments.
The central problem for organisms which grow optimally, and in some cases obligately, at pH values of 10 to 11, is the maintenance of a relatively acidified cytoplasm. A key component of the pH homeostatic mechanism is an electrogenic Na+/H+ antiporter which—by virtue of kinetic properties and/or its concentration in the membrane—catalyzes net proton uptake while the organisms extrude protons during respiration. The antiporter is also capable of maintaining a constant pHin during profound elevations in pHout as long as Na+ entry is facilitated by the presence of solutes which are taken up with Na+. Secondary to the problem of acidifying the interior is the adverse effect of the large pH gradient, acid in, on the total pmf of alkalophile cells. For the purposes of solute uptake and motility, the organisms appear to largely bypass the problem of a low pmf by utilizing a sodium motive force for energization. However, ATP synthesis appears not to resolve the energetics problem by using Na+ or by incorporating the proton-translocating ATPase into intracellular organelles. The current data suggest that effective proton pumping carried out by the alkalophile respiratory chain at high pH may deliver at least some portion of the protons to the proton-utilizing catalysts, i. e., theF1F0-ATPase and the Na+/H+ antiporter, by some localized pathway.
