Small Number Of Bacteria Research Articles

Any role left for invasive tests? Histology in clinical practice

Introduction Although some patients may consider even a venepuncture “invasive”, in the context of tests for Helicobacter pylori infection this term is usually restricted to those which require gastric biopsy...

Relationship of acid phosphatase activity to ultrastructural features in mice inoculated with Mycobacterium paratuberculosis

Macrophage activation, measured as increased acid phosphatase (AcPase)-positive areas by image analysis, and ultrastructural features were examined in granulomatous mycobacterial lesions of mice innately susceptible (BALB/c mice; Bcg) and innately resistant (C3H/HeJ mice; Bcg) to Mycobacterium paratuberculosis strain ATCC 19698. In the liver and spleen of BALB/c mice 3 weeks after intraperitoneal inoculation with M. paratuberculosis, AcPase activity detected in epithelioid cell nodules was high; it had decreased, however, in the liver and spleen after a further 3 and 6 weeks, respectively. In C3H/HeJ mice, the size of epithelioid cell nodules in the liver and spleen was smaller than in BALB/c mice, and infiltrating macrophages, which had increased by week 9 after inoculation, showed high AcPase activity. Ultrastructurally, by week 32 in BALB/c mice, small phagolysosomes (SPLs) had greatly increased in number in the epithelioid cells. These SPLs contained a few AcPase-positive areas and a small number of bacteria, most of which were surrounded by an electron-translucent space (or electron-transparent zone [ETZ]). In contrast, only a few SPLs were observed in C3H/HeJ mice at week 32; in the liver and spleen, large phagolysosomes (LPLs) showed high AcPase activity and contained many degenerated bacteria, which also had an ETZ. These results suggest that the enzymatic and ultrastructural differences in phagolysosomes between BALB/c mice and C3H/HeJ mice reflect the susceptibility of these mouse strains to M. paratuberculosis.

The pathogenic role of Staphylococcus epidermidis capsular polysaccharide/adhesin in a low-inoculum rabbit model of prosthetic valve endocarditis.

The capsular polysaccharide/adhesin (PS/A) antigen of Staphylococcus epidermidis was required to produce endocarditis in a rabbit model in which infection resulted from hematogenous spread of bacteria from a contaminated catheter in the jugular vein. However, many prosthetic valve endocarditis (PVE) infections probably result from direct contamination of the valve with small numbers of bacteria during surgery. The role of PS/A in this situation was evaluated by modifying a rabbit model of endocarditis to partially mimic PVE. A Teflon catheter was contaminated with graded inocula of either PS/A-positive S epidermidis strain M187sp11 or the PS/A-negative, isogenic strain M187sn3 and inserted into the left ventricle through the aortic valve. The PS/A-positive strain had a 50% infectious dose of 1.1 x 10(2) cfu (95% CI, 3.3 to 3.7 x 10(3)) compared with 8.5 x 10(4) cfu of the PS/A-negative strain (95% CI, 8.6 x 10(3) to 8.5 x 10(5)). The odds for developing endocarditis were estimated to be 42 times higher for any given inoculum level of the PS/A-positive strain (P = .1). When the PS/A-positive strain was adherent to a catheter surface it survived in rabbit blood, whereas under the same conditions the PS/A-negative strain was killed approximately 90% in 1 hour. Direct contamination of an intraventricular foreign body by low levels of PS/A-positive S epidermidis results in endocarditis in rabbits, but at suitably high doses PS/A-negative strains have sufficient virulence to infect cardiac vegetations. PS/A enhances but is not absolutely required for bacterial virulence in a rabbit model of PVE.

The Role of Rhizobial Biodiversity in Legume Crop Productivity in the West Asian Highlands

SUMMARYThe numbers of bacteria and the nitrogen fixing efficiency of isolates ofRhizobium leguminosarum, R. ciceriandR. melilotiwith appropriate legume crop species were determined from soils collected from a wide range of locations in Turkey with elevations between 500 and 2200 m. For vetch and lentil nodulated byR. leguminosarum, many native rhizobia are present in most locations but they often have limited nitrogen fixation capacity. However, for chickpea nodulated byR. ciceri, relatively small numbers of bacteria and the almost universal ineffectiveness of fixation capacity point to a need for artificial seed inoculation of chickpea crops as a future agronomic priority. The wide range of bacterial numbers, considerable geographic inconsistency and generally low effectiveness of the indigenous rhizobia associated with the annualMedicagospp. suggest that inoculation would initially be a sensible precaution for all sowings.Biodiversidad del rhizobium en Asia occidental

Low temperature growth, freezing survival, and production of antifreeze protein by the plant growth promoting rhizobacterium Pseudomonas putida GR12-2.

The plant growth promoting rhizobacterium Pseudomonas putida GR12-2 was originally isolated from the rhizosphere of plants growing in the Canadian High Arctic. Here we report that this bacterium was able to grow and promote root elongation of both spring and winter canola at 5 degrees C, a temperature at which only a relatively small number of bacteria are able to proliferate and function. In addition, the bacterium survived exposure to freezing temperatures, i.e., -20 and -50 degrees C. In an effort to determine the mechanistic basis for this behaviour, it was discovered that following growth at 5 degrees C, P. putida GR12-2 synthesized and secreted to the growth medium a protein with antifreeze activity. Analysis of the spent growth medium, following concentration by ultrafiltration, by SDS-polyacrylamide gel electrophoresis revealed the presence of one major protein with a molecular mass of approximately 32-34 kDa and a number of minor proteins. However, at this point it is not known which of these proteins contains the antifreeze activity.

Determination of bod by the use of a commercial seeding agent

The BOD test is currently one of the most commonly used methods to evaluate environmental waters and wastewaters. Recently, a specifically cultured bacteria has been developed as a seeding agent for the BOD test, and is commercially available. One of the commercialized seeding agents for the BOD test, was selected, and investigation of BOD5 test by using this agent was conducted. As a result, the observed values for the glutamic acid‐glucose standard solution for the river water‐based solution and the commercialized seeding agent based solution were in the range 220 ±10 mg/1 as defined by JIS, so that these two types of agents can be considered to be satisfactory for use as a seeding agent. The method of BOD determination by use of a commercial seeding agent is useful even for a sample containing a smaller number of bacteria.

Tuberculous pleural effusion: experience with six months of treatment with isoniazid and rifampicin.

Tuberculous pleurisy is associated with small numbers of bacteria. Due to the low rate of primary resistance to antituberculous drugs a two-drug regimen was used to treat the condition. Patients received isoniazid 5 mg/kg and rifampicin 10 mg/kg daily for six months. Clinical, radiological, and haematological assessments were performed during treatment and patients were followed up for a median period of 41 (range 6-96) months. One hundred and thirty patients were studied with a mean age of 27 (range 11-53) years. Seven were withdrawn due to parenchymal disease and eight were lost to follow up during the treatment period. Side effects during treatment were frequent (20.7%), but only three patients required a change in medication. No treatment failures were observed. One hundred and fifteen patients completed therapy and were followed up for 41 (range 6-96) months with no evidence of a relapse. Tuberculous pleurisy responds well to a two-drug regimen of antituberculous therapy given for six months.

Local vaccination with killed Streptococcus uberis protects the bovine mammary gland against experimental intramammary challenge with the homologous strain

The ability of killed streptococcus uberis to induce protection against mastitis when administered either into the cistern of the dry mammary gland (intramammary vaccination) without adjuvant or subcutaneously with adjuvant was investigated. Bacteria were never reisolated from vaccinated quarters following challenge with the same strain during the subsequent lactation, and no inflammatory response was detected. In contrast, following subcutaneous vaccination, milk from challenged quarters contained very small numbers of bacteria, but these quarters did exhibit clinical disease, whereas quarters on nonvaccinated control animals produced discolored, clotted secretion with large numbers of bacteria and somatic cells and required antibiotic therapy by 60 h postchallenge. There was a significant increase in the levels of S. uberis-specific immunoglobulin G1 (IgG1), IgG2, and IgM in milk following intramammary vaccination and in the levels of specific IgG1 and IgG2 in milk following subcutaneous vaccination. Levels of specific antibody in serum were also elevated following vaccination by either route. However, despite this, there was no increase in the opsonic activity of serum or milk. Both peripheral blood lymphocytes and dry-period mammary gland lymphocytes showed strong proliferative responses to S. uberis in vitro following subcutaneous vaccination, but only mammary gland lymphocytes responded following intramammary vaccination. It was concluded that the protection seen in vaccinated quarters did not appear to be related to levels of specific antibody or neutrophil function and was possibly brought about by the inhibition of bacterial growth.

Isolation and functional expression in Escherichia coli of a gene encoding phosphatidylethanolamine methyltransferase (EC 2.1.1.17) from Rhodobacter sphaeroides

Phosphatidylcholine is a major component of membranes in most eukaryotes, but it is found only in a small number of bacteria, where it is synthesized by N-methylation of phosphatidylethanolamine. In yeast and other fungi the methylation of phosphatidylethanolamine to phosphatidylcholine proceeds in two steps: the methylation of phosphatidylethanolamine by phosphatidylethanolamine methyltransferase followed by the methylation of monomethylphosphatidylethanolamine by phospholipid methyltransferase. Here we describe the isolation of two allelic phosphatidylcholine-deficient mutants of Rhodobacter sphaeroides which are unable to methylate phosphatidylethanolamine, monomethylphosphatidylethanolamine, or dimethylphosphatidylethanolamine. A DNA fragment containing a gene designated pmtA, which encodes a 22.9-kDa protein, was found to complement both mutants. Expression of this gene in Escherichia coli, which normally lacks phosphatidylcholine or methylated derivatives of phosphatidylethanolamine, resulted in the formation of phosphatidylcholine. A protein extract derived from the E. coli strain expressing the pmtA gene was able to convert phosphatidylethanolamine, mono- and dimethylphosphatidylethanolamine into phosphatidylcholine. Based on these data we conclude that the product of the pmtA gene catalyzes a sequence of three chemically distinct, methylation reactions beginning with phosphatidylethanolamine and leading to the formation of phosphatidylcholine in R. sphaeroides.

Acid suppression and the gastric flora

Until recent years the stomach and upper small intestine were believed to be relatively sterile (Hill, 1986; Drasar, 1989). The normal acid stomach (pH<4) has most commonly been found to have a sparse flora, consisting mainly of organisms from the mouth that have been swallowed with food or saliva and in the process of dying as a result of gastric acid. The major controlling factor for bacterial survival in the stomach thus appears to be pH. When pH is greater than 4 but less than 5 salivary organisms survive, particularly acid-tolerant lactobacilli and streptococci. Above pH 5 a resident gastric flora exists, including faecal streptococci and bacteroides (Hill, 1986; Drasar, 1989). This change is exemplified by studying the gastric bacterial flora of patients with pernicious anaemia and those who have had previous gastric surgery, which frequently contains faecal-type organisms such as Streptococcus faecalis and Bacteroides fragilis, which are also bile resistant. The jejunum and duodenum are also usually relatively free of bacteria in health. The sparse flora is due probably to the few live organisms entering from an acid stomach and the antibacterial effect of bile and pancreatic juice (Hill, 1986). In individuals with achlorhydria, small numbers of bacteria can be detected in jejunal juice but large numbers of organisms are only found in the presence of duodenal or jejunal diverticulae, blind loops or following previous gastric surgery (Drasar et al, 1.969). Our understanding of gastric and duodenal flora has been transformed by the discovery of Helicobacterpylori. This fascinating organism is now recognized to colonize the stomach in the majority of patients with active chronic gastritis and also those with peptic ulceration. It colonizes the duodenum as well in the presence of gastric metaplasia in most patients with chronic active duodenitis. H. pylori is found in the stomach in almost one-half to two-thirds of most populations, depending on the age and socioeconomic circumstances of those studied. The organism is of particular interest in relation to acid secretion since it is itself rapidly killed in an acid environment when the pH is less than 4 (Tompkins, 1989). The presence of this organism may also have effects on acid secretion by means of its association with elevated levels of circulating gastrin, although this is not completely resolved at present.

FOOD SAFETY IN THE HOME: CURRENT MICROBIOLOGICAL PERSPECTIVES

Despite the publication of two comprehensive reports (Richmond I and II) on the microbiological safety of food, together with new legislation, there has been little direct action concerning food safety in the home. Of particular relevance has been new research data which have shown that smaller numbers of bacteria are able to cause food poisoning, which stresses the importance of cross‐contamination. Doubts also have been raised about the safety of cooking raw meat in microwave ovens. Of perhaps greater impact have been the increased demands of food manufacturers and consumers on refrigeration. This has resulted, for example, from the increasing popularity of convenience foods and a reduction in the use of preservatives. Furthermore, many bacteria implicated in food poisoning are able to grow at relatively low temperatures. Recommendations include new standards by manufacturers of refrigerators and microwave ovens, together with a greater awareness and education of food safety issues.

Bacterial entry into eukaryotic cells

Bacterial pathogens have a strategy for survival that requires multiplication on or within a living host. The usual outcome of this microbial-host interplay is a subclinical infection in which both parties are the better for their interaction. That is, the microorganism grows to the extent sufficient either to colonize successfully the host or to be transmitted to another susceptible host. In turn, the host typically becomes resistant to subsequent serious infection or disease. The attributes of a successful pathogen (Finlay and Falkow, 1989) are an ability to carry out the following functions: first, gain entry into a host, most often a preferred host species; second, find a unique niche within the host; third, evade, circumvent, or exploit the host’s innate defense mechanisms; fourth, multiply; and finally, exit the host in a manner designed to maximize the likelihood of transmission to a new susceptible host. In some cases, this means that the microorganism must possess the genetic apparatus to survive in an external environment before it contacts a new host. For long-term carriage within the host, the successful pathogen also must be able to cope with the host’s adaptive immune system. Disease is not a necessary consequence of bacterial infection, although in some cases the overt symptoms that accompany microbial growth, such as coughing, sneezing, and diarrhea, are those that help ensure subsequent transmission. Death of the host is an inadvertent consequence of the successful pathogen’s strategy. In many ways pathogens have responded to their environment in a more sophisticated way than humans who, as predators, kill their food by intent. The attachment of the microorganism to the eukaryotic cell surface is one common tactic microorganisms use to prevail within their preferred host (reviewed in Moulder, 1985; Finlay and Falkow, 1989). The majority of bacterial pathogens remain localized on the extracellular host surface after attachment. Attachment is frequently mediated by organelles, usually bacterial pili, that interact with a particular host target molecule, typically a carbohydrate moiety. A smaller number of bacteria are internalized after binding to the host cell surface. It is this property, sometimes called microbial invasion (Moulder, 1985), that is the focus of this review. Invasion is most easily studied in the laboratory by mea suring bacterialentryintocultured mammalian cells. While one can employ direct microscopy, the most common technique to quantitate microbial invasion takes advantage of the fact that intracellular bacteria survive exposure to aminoglycoside antibiotics such as gentamicin, whereas extracellular bacteria are killed. The genetic and molecular basis of the entry process has been studied for several groups of gram-negative enteric bacteria (Finlay M inireview

Light and electron microscopic studies on red leg disease of the prawn (penaeus ortientalis kishinouye)

The red leg disease of the prawn (Penaeus orientalis Kishinouye) is a new kind of disease which occurred and prevailed in many maricuiture farm in East China in recent years. The article reports the pathological changes in the microstructure of some tissues from the diseased prawn, which are studied by light microscopy (LM) and transmission electron micros copy(TEM). The result shows that small number of bacteria exist in the haemolymph of the diseased prawn and that the number of haemocytes decreases obviously. Lots of tree-like or radiation-like orange-red pigment granules are seen int the derma layer of the shell of the swimming feet by LM. In the ultrathin section of the swimming feet many parasitic bacteria can be observed assembling or scattering in the cytoplasm as well as in the cytoplasm of midgut, heart and gill fillarnents(Fig 4-6). Its proved that the bacteria separated from the haemlymph of the diseased prawn are the pathogen of the red leg disease known as Vibrio angullarum through the tests of the manual infection and bacteriological identifications. Its a short bacillus without germ, but with a single-ended flagella which has sheath.

Possibilities of Bacteremia and Toxemia in Death of Chickens Infected with Eimeria tenella

The possibility that bacteremia and toxemia were the causes of death in cases of cecal coccidiosis was investigated. Germ-free and ordinary chickens with microflora were inoculated with sporulated oocysts of Eimeria tenella. At 5 days postinoculation, cecal lesions in ordinary chickens were more severe than those in germ-free ones. Cardiac blood, spleen, and liver were examined in ordinary chickens for bacteremia and endotoxemia, and small numbers of bacteria were recovered from both infected and uninfected birds. Endotoxin levels in plasma of E. tenella-infected birds were low and not different from the levels of uninfected controls. To examine unknown toxic factors, a large volume of serum from infected chickens was injected intravenously into uninfected birds. No significant clinical signs were observed. It is concluded that the intestinal bacteria increase the severity of coccidial lesions without bacteremia and toxemia.

Rapid identification of cultured Mycobacterium tuberculosis with a panel of monoclonal antibodies in Western blot and immunofluorescence

This paper describes the identification of cultured mycobacteria with a panel of monoclonal antibodies directed against species-specific epitopes in a Western blot (WB) test and in an immunofluorescence test (IFT). In WB, we identified mycobacteria of the Mycobacterium tuberculosis complex ( M. tuberculosis, M. africanum, M. bovis, M. bovis BCG, and M. microti) with 10 8 bacteria. In the IFT, we identified mycobacteria of the M. tuberculosis complex, the M. avium complex ( M. avium, M. intracellulare and M. scrofulaceum) and M. kansasii with 10 7 bacteria. Using a panel of 105 mycobacterial patient isolates, we compared identification by WB and IFT with conventional, culture and biochemical identification. Identification of the M. tuberculosis complex in WB had a specificity and sensitivity of 96.3 and 98.3 %, respectively. Identification in IFT of the M. tuberculosis complex had a specificity and sensitivity of 94.6 % and 89.7 %, respectively. Since the identification of mycobacteria with mAb requires only a small number of bacteria, these tests will reduce by several weeks the time necessary for microbiological identification.

Rapid identification of cultured Mycobacterium tuberculosis with a panel of monoclonal antibodies in Western blot and immunofluorescence

This paper describes the identification of cultured mycobacteria with a panel of monoclonal antibodies directed against species-specific epitopes in a Western blot (WB) test and in an immunofluorescence test (IFT). In WB, we identified mycobacteria of the Mycobacterium tuberculosis complex ( M. tuberculosis, M. africanum, M. bovis, M. bovis BCG, and M. microti) with 10 8 bacteria. In the IFT, we identified mycobacteria of the M. tuberculosis complex, the M. avium complex ( M. avium, M. intracellulare and M. scrofulaceum) and M. kansasii with 10 7 bacteria. Using a panel of 105 mycobacterial patients isolates, we compared identification by WB and IFT with conventional, culture and biochemical identification. Identification of the M. tuberculosis complex in WB had a specificity and sensitivity of 96.3 and 98.3 %, respectively. Identification in IFT of the M. tuberculosis complex had a specificity and sensitivity of 94.6% and 89.7%, respectively. Since the identification of mycobacteria with mAb requires only a small number of bacteria, these tests will reduce by several weeks the time necessary for microbiological identification.

In vitro quantitative model of catheter infection during simulated parenteral nutrition.

We developed a quantitative in vitro model of catheter infection. Colonization was initiated by inoculating the catheter lumen with a small number of bacteria (approximately 5 x 10(3) viable organisms). Then the inoculated catheters were used for simulated total parenteral nutrition therapy consisting of infusions for 9 h a day, and bacteria were counted in the effluent fluid against time, enabling us to monitor catheter colonization quantitatively. Bacterial colonization of prosthetic devices is a progressive process, as evidenced by the slow day-to-day increase of bacterial release seen here. On the other hand, bacterial strains of various representative species exhibited significant differences in their ability to infect catheters. These results suggest that the in vitro model presented here is a reliable tool for monitoring the degree of catheter colonization under standardized conditions and could be used for further studying the main factors of catheter-related sepsis or the treatment of this information.

Povidone-Iodine in Polyethylene Oxide Hydrogel Dressing

We studied the ability of a polyethylene oxide hydrogel dressing (Vigilon) containing povidone-iodine to prevent Staphylococcus aureus proliferation in partial-thickness wounds. We previously reported that a single application of povidone-iodine on wounds challenged with 2 X 10(6) S aureus was not effective in reducing the number of S aureus after 24 hours. It was therefore hypothesized that povidone-iodine might be effective if it was available continuously and applied to wounds containing a smaller number of bacteria. To test this hypothesis, we made multiple partial-thickness wounds (5 X 7 X 0.3 mm) on six domestic pigs. We then inoculated the wounds by scrubbing them with either a low concentration (log 3.5) or a high concentration (log 7) of S aureus suspension. The wounds were either treated with Vigilon or Vigilon containing povidone-iodine or left air exposed. Wounds from each of these treatment groups were cultured by the scrub technique for S aureus with a 0.5% sodium thiosulfate-polysorbate (Tween) 80 solution 5 minutes, 30 minutes, 24 hours, or 48 hours later. A significant reduction in the number of S aureus recovered from wounds treated with Vigilon containing povidone-iodine was seen with the group inoculated with a low bacterial concentration after 24 hours; but no reductions were observed when wounds were inoculated with the higher bacterial concentration of log 7. We found Vigilon containing povidone-iodine to be an effective inhibitor of S aureus in wounds over a 24-hour period when the organism was present in low numbers.

Rhizobium trifolii mutants deficient in exopolysaccharide production

Spontaneous mutants of Rhizobium trifolii 24AR5 which did not produce exopoly‐saccharide were isolated. The non‐mucoid mutants formed small white and ineffective nodules on both red and white clover. These nodules contained infection threads, but only a small number of bacteria were released into nodule cells, and bacteroids were rarely observed. The non‐mucoid phenotype was not complemented by the symbiotic plasmid (pJB5JI) of Rhizobium leguminosarum.

Intestinal microbial flora after feeding phytohemagglutinin lectins (Phaseolus vulgaris) to rats.

Incorporation of purified phytohemagglutinin (PHA) lectins derived from red kidney beans (Phaseolus vulgaris) in the diet of weanling rats will cause growth failure, malabsorption of nutrients, and bacterial overgrowth in the small intestine. These effects are not caused by feeding a similar quantity of PHA to germfree rats. To define the morphological and bacterial changes on the mucosal surfaces of the jejunum, ileum, and cecum in greater detail, we pair fed two groups of weanling rats isocaloric, isonitrogenous diets with or without 0.5% PHA protein. On the jejunal surfaces of control rats, the mucous layer was a confluent covering with sparsely scattered bacteria and protozoa. In PHA-treated rats, the mucous layer was thin and discontinuous, and the microvillous surface of the tissue was extensively populated by bacterial cells of two distinct morphotypes--a gram-negative rod and a gram-positive coccobacillus. In all PHA-treated animals, these bacteria formed adherent monospecific or mixed adherent microcolonies on the tissue surface. Tissue damage was observed in PHA-exposed jejunal tissue as evidenced by vesiculation of the microvillous plasma membrane and by damage to the brush border membrane. On the ileal surfaces of control rats, there was a thick mucous layer within which small numbers of bacteria and protozoa were seen. Segmented filamentous bacteria were anchored in the tissue surface. In PHA-treated rats, the ileal surface was only incompletely covered by a mucous layer, and the overlying mucosal surface was extensively covered by large numbers of protozoan cells (predominantly Hexamita muris). Most of the ileal surfaces not covered by the mucous layer were occupied and virtually occluded by an overgrowth of these protozoan cells with occasional cells of Giardia muris and the tissue-associated segmented bacillus. In the ceca of control rats, the mucosa was incompletely covered by a discontinuous mucous layer and colonized by an unnamed Spirillum sp., other bacteria, and occasional protozoa. The cecal surfaces of PHA-treated rats retained most of their incomplete overlying mucous layer, which was heavily colonized by the same type of Spirillum sp. seen in untreated animals; intestinal crypts were colonized. These descriptive morphological studies demonstrate that exposure to purified PHA in the diet caused characteristic changes in the microbial ecology of the small intestine. The changes in microbial flora contributed to the malabsorption of nutrients in the small intestines of PHA-fed animals.