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PubMed1994

Studies on the bacterial flora of fish which are potential pathogens for human. Isolation of various potential human pathogenic organisms from different parts of fish and their significance in initiating human diseases.

Freshwater fish of different categories, collected from market of Dhaka City of Bangladesh, were studied for the bacterial flora. Potential human pathogens were isolated from about eighty-five percent of the fish studied. Organisms isolated were Aeromonas spp., (69.2%), Vibrio spp., (42.3%), Plesiomonas shigelloides (35.9%) and Escherichia coli (16.7%). The high association of potential human pathogens among the freshwater fish suggest that if fish are handled improperly or if consumed undercooked or uncooked may cause various diseases to susceptible individual.

Animals↗

PubMed1997

Ecto-nucleotide triphosphatase activity in pathogenic and non-pathogenic Entamoeba: protection from the cytotoxic effects of extracellular ATP.

The nucleotide triphosphatase (NTPase) activity of Entamoeba species and of Entamoeba histolytica strains, was compared. In all cases, with the exception of Entamoeba moshkovskii, the enzyme was activated by Ca2+ and not by Mg2+ and preferentially hydrolysed UTP with decreasing activity for ATP and GTP. The NTPase activity was associated with both the intracellular and the plasma membrane sulphonylbenzoyl-adenosine (FSBA) of trophozoites in which the ATP-site was facing externally, as shown by fluoroinhibition of NTPase activity and protection by the substrate added prior to FSBA. The highest surface activity was found in Entamoeba invadens and in the virulent E. histolytica HM1-A clone (HM1-IMSS passaged thrice through hamster liver). Significant lower activity was observed in non-pathogenic Entamoeba spp. The addition of ATP to cultures of pathogenic amoebae resulted in cell growth inhibition and lysis. This deleterious effect of adding ATP to the cultures was reversed by the addition of Ca2+. ATP hydrolysis by the amoeba may alter extracellular ATP-dependent processes in the host, which may be important for the survival of the amoeba in vivo.

Acid Anhydride Hydrolases↗

PubMed2001

Pathogenicity of environmental origin Salmonellas in specific pathogen-free chicks.

Two hundred sixty 1-d-old specific pathogen-free (SPF), Single Comb White Leghorn chicks were used in this study to determine pathology caused by Salmonella enteritidis (SE) isolated from a poultry environment. The chicks were subdivided into 10 equal groups of 26 chicks each. Eight groups of chicks were inoculated individually with 0.5 mL of brain heart infusion broth culture containing 1 x 10(6) cfu of SE phage type (PT) -8 (1, 2, 3), SE PT5 A (1, 2), or SE PT4 (Ch-env-CA, chicken-CA, and human) by crop gavage. One group of 26 chicks were inoculated with 1 x 10(6) cfu of Salmonella pullorum per bird by crop gavage. Another group of 26 chicks were kept as an uninoculated control group. All the chicks were observed daily for clinical signs and mortality. Salmonella was reisolated from different organs at 7, 14, 21, and 28 postinoculation (DPI). All of the chicks were weighed individually at each interval. Two chicks at random from each group were euthanised and necropsied at each DPI for gross pathology. Selected tissues were examined for histopathological changes at 7 and 14 DPI. Dead chicks were examined for gross and histopathological lesions. Mortality rates were 30.7, 15.3, and 7.6% in the groups inoculated with S. pullorum, SE PT5A, and SE PT4 (chicken-CA), respectively. No mortality or clinical sign were observed in other treatment groups or in uninoculated control groups. Cecal pouches were found to be the ideal organ for reisolation of Salmlonella at acute or chronic infection compared with other organs. Mean body weights were reduced to 1.8 to 12.6% in inoculated groups compared with the uninoculated control group. The consistent gross and hispathological lesions were of peritonitis, perihepatitis, yolk sac infection, and enteritis. Subclinical Salmlonella infection identified in this study resulted in reduced body weights of inoculated birds compared with uninoculated controls.

Animals↗

PubMed1984

The pathogenicity of Salmonella mbandaka in specific pathogen free rabbits.

Salmonella mbandaka was isolated from the lungs of three rabbits that developed a peracute disease and died three to eight weeks following extensive experimental manipulation. To examine the pathogenicity of this rare serotype, clinically normal, S. mbandaka-carrier rabbits were subjected to either corticosteroid immunosuppression alone or corticosteroid immunosuppression with a minor surgical procedure. Acute or peracute salmonellosis developed in one of two rabbits immunosuppressed only, and in three of four rabbits immunosuppressed and surgically manipulated. Stressful experimental procedures may precipitate episodes of clinical salmonellosis in rabbits harboring this organism. Salmonella mbandaka, should be considered a zoonotic agent in the laboratory environment.

Animals↗

PubMedDate not supplied

Ethical issues in the handling of bloodborne pathogens: evaluating the Occupational Safety & Health Administration Bloodborne Pathogen Standard.

The Occupational Safety & Health Administration Bloodborne Pathogen Standard is designed to help provide protection from contamination in the workplace. Healthcare professionals must evaluate the standard and the behaviors mandated therein, according to the basic professional ethical principles of professional autonomy, beneficence, and cost-benefit considerations. The patient's wellbeing provides the focus for making such an assessment.

Beneficence↗

PubMed1996

A RAPD-PCR derived marker can differentiate between pathogenic and non-pathogenic Sarcocystis species of sheep.

Random amplified polymorphic DNA (RAPD)-PCR was used to differentiate among four cyst-forming coccidia of sheep, Sarcocystis tenella, Sarcocystis gigantea, Sarcocystis arieticanis, and Toxoplasma gondii. Genomic DNA of the four parasite species was amplified using RAPD-PCR and the DNA fragments were separated on agarose gels. A RAPD-PCR band derived from S. tenella was isolated from the gel and subcloned into pUC18. The insert was sequenced and found to be 1278 nucleotides long. This sequence appeared to be cryptic in nature as it showed no significant sequence peculiarities or similarity with any other known sequences either at the nucleotide or derived amino acid levels. The recombinant plasmid was radiolabelled and used as a probe in Southern hybridization. This probe, termed pSTF10, hybridised to Mbo I restricted genomic DNA of S. tenella and S. arieticanis, but not to DNA of S. gigantea, T. gondii, mouse, or sheep. It is likely that STF10 will become a valuable diagnostic tool for Sarcocystis infections in sheep to differentiate between pathogenic species of this genus and S. gigantea or T. gondii.

Animals↗

PubMed1998

A simplified sample preparation method from various foods for PCR detection of pathogenic Yersinia enterocolitica: a possible model for other food pathogens.

A simplified method for the direct application of multiplex polymerase chain reaction (PCR) was developed to detect plasmid-bearing virulent serotypes of Yersinia enterocolitica (YEP+) in a variety of foods. Strains of YEP+ representing five serotypes were detected in enriched swab samples of artificially contaminated pork chops, ground pork, cheese and zucchini using multiplex PCR analysis. The method was also effective for identifying YEP+ strains in naturally contaminated porcine tongues. The use of swabs eliminated time-consuming extraction of DNA from food, inhibition of PCR by food-derived DNA, interference by background flora and reduced the time needed for processing samples. The detection of other food pathogens should be feasible by this technique.

Animals↗

PubMed1993

Distribution of a lipooligosaccharide-specific sialyltransferase in pathogenic and non-pathogenic Neisseria.

Sialyltransferase activity has been detected in Triton X100 extracts of all examined strains of pathogenic Neisseria as well as in 17 out of 18 Neisseria lactamica isolates. The enzyme was detected both in strains able to synthesize the 4.5 kDa lipooligosaccharide (LOS) component known to be sialylated in vivo and in vitro by cytidine 5'-monophospho-N-acetylneuraminic acid, and in some strains which lack this component. Exogenous 4.5 kDa+ LOS was required to detect the sialyltransferase activity in strains which lacked the LOS component. Sialyltransferase activity in a serogroup A, L11 (4.5 kDa-) meningococcal strain sialylated exogenous purified LOS from gonococci. The meningococcal serogroup B and C strain sialyltransferases active with LOS acceptors appeared to be distinct from the sialyltransferase required for the synthesis of the meningococcal polysialic acid capsule.

Lipopolysaccharides↗

PubMed2001

Rotavirus cross-species pathogenicity: molecular characterization of a bovine rotavirus pathogenic for pigs.

Rotaviruses which cause disease in heterologous animal species have been reported but the molecular basis of cross-species infectivity and disease is not established. We report the molecular characterization of a cloned rotavirus, PP-1, which was originally obtained from cattle and which had been biologically characterized in vivo in two target animal species, gnotobiotic pigs and calves. In pigs, PP-1 caused severe clinical disease but in experimental calves it replicated subclinically. PP-1 was characterized as a G3 reassortant with a porcine VP4 and NSP4 but a bovine NSP1. The PP-1 VP4 had 96 to 97% deduced amino acid identity to P[7] porcine rotaviruses and P[7] specificity was confirmed with VP4-specific monoclonal antibodies. Sequence analysis of the PP-1 NSP1 showed 94 to 99.6% deduced amino acid identity to bovine rotaviruses but the NSP4 protein had 94 to 98% identity to the NSP4 genotype B porcine rotaviruses. G-typing PCR initially classified PP-1 as a G10 rotavirus but sequence analysis revealed 92 to 96% identity of the PP-1 VP7 with porcine, simian, and human G3 rotaviruses. These results, combined with the in vivo properties of PP-1 in the two target species, supported the concept that species-specific VP4 and NSP4, but not NSP1, are required to induce rotavirus disease, at least in calves and pigs. The results illustrate experimentally that rotaviruses circulating in one animal species can pose a risk to another by the emergence of a pathogenic reassortant rotavirus under appropriate conditions.

Amino Acid Sequence↗

PubMed1996

Fusaric acid and pathogenic interactions of corn and non-corn isolates of Fusarium moniliforme, a nonobligate pathogen of corn.

Fusarium moniliform is a nonobligate parasite of corn, which exists as a complex of closely related fungi from different mating population or biological species. Strains of this fungus isolated from corn, have been determined to belong to mating populations A, although other populations have been isolated from corn. The ultrastructural association of the fungus with corn during growth, and the effects of the host on suppression of disease suppression are reviewed. This fungus enters a relationship with corn cultivars that is not always pathogenic. Pathogenesis is delayed, if it ever occurs. F. moniliforme can exist entirely as an endophyte, systemically colonizing kernels, remaining there until germination upon which the fungus infects the emerging seedlings. The symptomless association persists during the growth cycle of corn, and the resulting endophytic hyphae may be the source of mycotoxin production. The host's ability to suppress the fungus appears to be related to one class of compounds, the cyclic hydroxamic acids and their decomposition products, which can be catabolized by the fungi of mating population A but not C.

Fusaric Acid↗

PubMedDate not supplied

Antimicrobial activity of cefotaxime tested against infrequently isolated pathogenic species (unusual pathogens).

The cefotaxime sodium spectrum of activity is very broad and includes many common species and a variety of less frequently isolated pathogens. We have reviewed the clinical microbiology literature (44 references) and the data base of the University of Iowa Hospitals and Clinics (Iowa City, IA) to collect data on the activity of cefotaxime against the less common species. Cefotaxime was consistently active against Actinobacillus actinomycetemcomitans, Capnocytophaga spp., Eikenella corrodens, Erysipelothrix rhusiopathiae, Pasteurella multocida, Plesiomonas shigelloides, and Fusobacterium nucleatum. The species Alcaligenes xylosoxidans, Flavobacterium spp., Stenotrophomonas (Xanthomonas) maltophilia, Bacillus cereus, Listeria monocytogenes, and Rhodococcus equi were uniformly cefotaxime resistant. For many other species there was considerable variation in reported minimum inhibitory concentrations. These data may be helpful in guiding therapy of unusual infections, particularly in the case of fastidious species, where the appropriate susceptibility testing methodology may not be immediately or routinely available.

Bacteria, Anaerobic↗

PubMed2003

Tularemia in BALB/c and C57BL/6 mice vaccinated with Francisella tularensis LVS and challenged intradermally, or by aerosol with virulent isolates of the pathogen: protection varies depending on pathogen virulence, route of exposure, and host genetic background.

In order to begin understanding the immunological basis for immunity to tularemia, and to establish a baseline for judging the efficacy of potential novel vaccines, the present study examined the ability of the live vaccine strain of Francisella tularensis (F. tularensis) LVS, to elicit immunity in mice against subsequent systemic and aerosol challenge with highly virulent strains of the pathogen. The results show, that infection with LVS protects BALB/c mice against systemic challenge with virulent Types A and B F. tularensis. In contrast, C57BL/6 mice vaccinated with LVS were only rendered immune to systemic challenge with Type B F. tularensis. Neither mouse strain immunized with LVS was able to resist aerosol challenge with Type A F. tularensis, and only immunized BALB/c mice withstood exposure to aerosols of Type B F. tularensis.

Aerosols↗

PubMed1999

Sequence analysis of the chitin synthase A gene of the Dutch elm pathogen Ophiostoma novo-ulmi indicates a close association with the human pathogen Sporothrix schenckii.

Degenerate oligonucleotide primers were designed according to conserved regions of the chitin synthase gene family and used to amplify a 621 basepair (bp) fragment from genomic DNA of Ophiostoma novo-ulmi, the causal agent of Dutch elm disease. The amplification product was used as a hybridization probe to screen a library of genomic DNA sequences and to retrieve a full-length chitin synthase gene (chsA). The putative coding region of the gene was 2619 bp long, lacked introns, and encoded a polypeptide of 873 amino acids. Based on the similarity of the predicted amino acid sequence to the full-length chsC gene of Aspergillus nidulans and chsA gene of Ampelomyces quisqualis, the O. novo-ulmi chsA was classified as a Class I chitin synthase. The phylogenies constructed, according to a subregion of all available chitin synthases, showed that O. novo-ulmi consistently clustered most closely with the human pathogen Sporothrix schenckii, recently classified as a member of the mitosporic Ophiostomataceae. Disruption of the chsA gene locus had no obvious effects on the growth or morphology of the fungus.

Amino Acid Sequence↗

PubMed2000

Phylogenetic analysis of two potyvirus pathogens of commercial cowpea lines: implications for obtaining pathogen-derived resistance.

As a prelude to developing engineered resistance to two important potyvirus pathogens of cowpea, a phylogenetic analysis of strains of Cowpea aphid-borne mosaic virus (CAbMV) and Bean common mosaic virus--blackeye cowpea strain (BCMV-B1C) was undertaken. Nucleotide sequences for the coat protein genes and 3'-untranslated regions of four CAbMV and one BCMV-B1C strains were determined and included in an analysis with published sequences. While all the newly sequenced viruses showed strong homology with the existing respective sequences in the database, the CAbMV group showed a divergence into two subgroups. These groups differed from each other by more than some CAbMV strains differed from the South African Passiflora virus (CAbMV-SAP), which has distinct biological characteristics. The implications of the sequence analyses are discussed with respect to a strategy for the generation of engineered resistance to both groups of viruses.

3' Untranslated Regions↗

PubMed2000

The txtAB genes of the plant pathogen Streptomyces acidiscabies encode a peptide synthetase required for phytotoxin thaxtomin A production and pathogenicity.

Four Streptomyces species have been described as the causal agents of scab disease, which affects economically important root and tuber crops worldwide. These species produce a family of cyclic dipeptides, the thaxtomins, which alone mimic disease symptomatology. Structural considerations suggest that thaxtomins are synthesized non-ribosomally. Degenerate oligonucleotide primers were used to amplify conserved portions of the acyladenylation module of peptide synthetase genes from genomic DNA of representatives of the four species. Pairwise Southern hybridizations identified a peptide synthetase acyladenylation module conserved among three species. The complete nucleotide sequences of two peptide synthetase genes (txtAB) were determined from S. acidiscabies 84.104 cosmid library clones. The organization of the deduced TxtA and TxtB peptide synthetase catalytic domains is consistent with the formation of N-methylated cyclic dipeptides such as thaxtomins. Based on high-performance liquid chromatography (HPLC) analysis, thaxtomin A production was abolished in txtA gene disruption mutants. Although the growth and morphological characteristics of the mutants were identical to those of the parent strain, txtA mutants were avirulent on potato tubers. Moreover, introduction of the thaxtomin synthetase cosmid into a txtA mutant restored both pathogenicity and thaxtomin A production, demonstrating a critical role for thaxtomins in pathogenesis.

Bacterial Proteins↗

PubMed2002

O(6)-alkylguanine-DNA alkyltransferase DNA repair in mycobacteria: pathogenic and non-pathogenic species differ.

SETTING: DNA repair genes assist the organism in maintaining DNA integrity in the face of environmental (mutagenic) stress. The genome sequences of M. tuberculosis and M. bovis demonstrate sequences suggestive of an O(6)-alkylguanine-DNA alkyltransferase DNA repair activity similar to that seen in almost all other bacterial and eukaryotic organisms. The near ubiquitousness of this gene implies an important function. OBJECTIVE: Our aim was to ascertain whether mycobacteria exert an alkyltransferase response to mutagen (streptozotocin) stimulation and whether alkyltransferase activity is essential for mycobacterial survival. DESIGN: Alkyltransferase activity in slow- and fast-growing mycobacterial species was determined in the presence and absence of sublethal concentrations of an alkylating agent streptozotocin. The intracellular survival and response to anti-tuberculosis drugs of an alkyltransferase knockout strain of M. bovis BCG was also determined. RESULTS: We demonstrate the presence of O(6)-alkylguanine alkyltransferase (cellular methyltransferase activity) in mycobacterial species and that there is an inducible and constitutive form in fast-growing mycobacteria (M. smegmatis), whereas only the constitutive form exists in the pathogenic or slow-growing species (M. bovis BCG) under the conditions tested. The overall activity of the constitutive form is high. We also show that intracellular growth of M. bovis BCG in macrophages is reduced when the alkyltransferase gene is absent. The presence of alkyltransferase activity appears to assist the organism in reducing the effects of isoniazid, since interruption of the gene confers sensitivity to the drug. CONCLUSIONS: We conclude that for the slow-growing mycobacteria, an inducible response is not essential as their ecological niche is stable and protected, but that the presence of the alkyltransferase activity confers a growth advantage in macrophages and offers some protection against antibiotics.

Base Sequence↗

PubMed1999

Pathogenic neisseriae: complexity of pathogen-host cell interplay.

Recent studies have provided insight into the function of important neisserial adhesins (pili and Opa) and their interaction with cellular receptors, including members of heparan sulfate proteoglycan, CD66, and integrin receptor families. These interactions not only allow colonization of the human mucosa but also stimulate cellular signaling cascades involving phosphatidylcholine-dependent phospholipase C, acidic sphingomyelinase and protein kinase C in epithelial cells, and Src-related kinases, Rac1, p21-activated kinase, and Jun N-terminal kinase in phagocytic cells. Activation of these pathways is essential for cellular entry and intracellular accommodation of the pathogens but also leads to early induction of cytokine release, thus priming the immune response. Detailed knowledge of the cellular signaling cascades that are activated by infection will aid us in applying both current and novel interfering drugs (in addition to classical antibiotic therapy) as therapy and prophylaxis for persistent or otherwise difficult-to-treat bacterial infections, including periodontal infections.

Antigens, Bacterial↗

PubMed1998

Cloning, expression, and role in pathogenicity of pg1 encoding the major extracellular endopolygalacturonase of the vascular wilt pathogen Fusarium oxysporum.

pg1 encoding the major in vitro extracellular endopolygalacturonase of the tomato vascular wilt pathogen Fusarium oxysporum f. sp. lycopersici was cloned and sequenced. The deduced mature protein had a calculated molecular mass of 35.5 kDa and a pI of 6.2, and showed significant similarity with other fungal endoPGs. pg1 mRNA was induced in vitro by citrus pectin, tomato vascular tissue, 0.1% D-galacturonic acid, and polygalacturonic acid, and repressed by 1% D-galacturonic acid and 1% glucose. Reverse transcription-polymerase chain reaction revealed pg1 expression in roots and lower stems of tomato plants infected by F. oxysporum f. sp. lycopersici. Three naturally occurring F. oxysporum f. sp. melonis isolates deficient in PG1 were transformed with the cloned gene. The PG1 enzyme secreted by the transformants had the same molecular mass, pI, and glycosylation pattern as those of the donor isolate. Polygalacturonase activity in cultures of transformants grown in vitro on citrus pectin and on melon plants, but not on glucose, increased 10- to 20-fold, compared with the PG1-deficient wild-type isolate, whereas mycelial dry weight increased two- to three-fold. Transformants exhibited the same degree of virulence toward susceptible muskmelon cultivars as the wild-type isolate and were avirulent on a resistant cultivar.

Amino Acid Sequence↗