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PubMedDate not supplied

Escherichia coli as a pathogen in dogs and cats.

Certain strains of Escherichia coli behave as pathogens in dogs and cats causing gastro-intestinal and extra-intestinal diseases. Among the five known groups of diarrhoeagenic E. coli, namely enteropathogenic E. coli (EPEC), enterotoxigenic E. coli (ETEC), enteroinvasive E. coli (EIEC), shiga-toxin producing E. coli (STEC) and enteroaggregative E. coli (EAggEC), only EPEC and ETEC were clearly associated with enteric disease in young dogs. ETEC isolates from diarrhoeic dogs were found to be positive for the heat-stable enterotoxins STa and STb but negative for heat-labile enterotoxin (LT). Canine ETEC were found to be different from those of other animals and humans by their serotypes, production of alpha-haemolysin and adhesive factors and by the production of uncharacterized types of enterotoxins by some ETEC. Canine EPEC could be distinguished from EPEC of humans or other animals by their serotypes and by the eae-protein intimin which mediates intimate adherence of EPEC to intestinal mucosa cells. STEC were occasionally isolated from faeces of healthy and diarrhoeic dogs but their role in canine diarrhoea is not yet well known. EIEC and EAggEC were not reported to occur in dogs or cats. Very little is known on diarrhoegenic E. coli in cats and further epidemiological investigations on this subject are needed. Besides its role in gastro-intestinal infections, E. coli can cause infections of the urogenital tract and systemic disease in dogs and cats. Extra-intestinal pathogenic E. coli strains from dogs and cats belong to a limited number of serotypes and clonal groups and are frequently found as a part of the normal gut flora of these animals. Many of these E. coli strains carry P-fimbriae and produce alpha-haemolysin and a necrotizing cytotoxin (CNF1). Some of the frequently isolated types of extra-intestinal pathogenic E. coli from dogs, cats and humans were found to be highly genetically related but showed differences in their P-fimbrial adhesins which determine host specificity. Transmission of extra-intestinal and enteral pathogenic E. coli between dogs and humans was reported. Further research is needed, however, to determine the role of dogs and cats as transmission vectors of pathogenic E. coli strains to other animals and humans.

Animals↗
PubMed1999

Experimental exposure of young pigs using a pathogenic strain of Streptococcus suis serotype 2 and evaluation of this method for disease prevention.

Control of Streptococcus suis infections and associated disease have proven to be a difficult challenge under most farm conditions. The objective of this study was to experimentally expose young pigs with a pathogenic strain of S. suis serotype 2 as a means of controlling the disease in a commercial swine farm. Prior to the start of the study, the pathogenic S. suis strain responsible for mortality in the farm was identified and used to experimentally inoculate baby piglets. Over a 3-week period, groups of pigs were selected (100 pigs/wk) and divided into 2 groups: control (50 pigs/week) and experimentally exposed (50 pigs/week). Pigs in the experimentally exposed group were inoculated at 5 d old by tonsillar swabbing with the pathogenic S. suis farm isolate. The effect of exposure with this pathogenic strain was evaluated during the nursery and finishing stages and was based on: morbidity (pigs with central nervous signs (CNS) and/or lameness), mortality and number of treatments required by pigs that had either CNS or lameness. The relative risk (RR) of acquiring disease due to S. suis infection was also calculated. Results showed that morbidity in the experimentally exposed groups was lower than in the control group and these results were statistically different (P = 0.006). Experimentally exposed pigs also showed a statistically significant reduction in lameness problems (P = 0.012), but not in CNS (P = 0.20) or mortality (P = 0.59). Pigs in the control group had an increased RR of 4.76, 8.77 and 2.7 for morbidity, to have lameness or to have CNS signs, respectively. In conclusion, experimental exposure of young pigs with the farm's pathogenic S. suis strain at a young age, had a positive effect in reducing clinical signs characteristics of S. suis infection. This method constitutes a novel approach to the control of S. suis infections in swine farms.

Age Factors↗
PubMed2000

Emerging resistance problems among respiratory tract pathogens.

The number-1 indication for antibiotic prescriptions in the United States is a respiratory tract infection. The changing spectrum of pathogens and emerging bacterial resistance are changing the way these infections are managed. The epidemiology of community-acquired pneumonia has changed significantly in the past 20 years, with increased diversity of pathogens and mortality. Emerging resistance in respiratory tract pathogens, particularly to beta-lactams, is an increasing concern. Of the important gram-negative pathogens, more than a third of Haemophilus influenzae isolates are now resistant to beta-lactam antibiotics, as well as virtually all isolates of Moraxella catarrhalis. Of the gram-positive organisms, more than 40% of Streptococcus pneumoniae isolates are no longer susceptible to penicillin, and methicillin resistance has been reported in up to half of Staphylococcus aureus isolates in some institutions. Among staphylococci, resistance to the beta-lactam methicillin is often accompanied by resistance to multiple classes of antibiotics, particularly the macrolides. Little resistance to fluoroquinolones has been reported among gram-negative respiratory tract pathogens and S pneumoniae, although increasing resistance may be seen as these drugs are used with increasing frequency. In contrast, fluoroquinolone resistance can develop rapidly in S aureus and appears to be associated with methicillin resistance. Fortunately, many of the newer fluoroquinolones appear to offer significant activity against methicillin-resistant S aureus isolates and are active against ciprofloxacin-resistant strains of S pneumoniae. Today, to combat respiratory tract infections, a broad-based empiric therapy needs to be used and bacterial resistance must be taken into account. New antimicrobial options must be considered, with an emphasis on effective drug use and optimal dosing. Even if a direct relationship between antibiotic resistance and clinical outcomes in the treatment of pneumonia in adults has not been extensively demonstrated, the increasing problem of resistance has changed treatment approaches for respiratory tract infections as a whole.

Anti-Infective Agents↗
PubMed1999

Molecular characterization of ticks and tick-borne pathogens.

Ticks and their vertebrate hosts often carry several pathogens simultaneously, which either belong to different or to the same genera. Conventional methods (such as blood smear examination or tick salivary gland staining) are often unable to discriminate between pathogens. Therefore, molecular methods for the detection and differentiation of tick-borne pathogens are increasingly used. Technical problems still remain to identify pathogens within tick tissues, or within host animals when infection rates are very low. Recently we developed an integrated approach to identify several pathogens with only one molecular test. This approach, the reverse line blot hybridization (RLB) reduces costs of analysis, gives quicker results. and allows standardized inter-laboratory comparisons. Finally, this paper also focuses on the molecular diagnostic techniques currently used in the laboratories of the Mediterranean countries.

Animals↗
PubMed2000

The effects of Nosema algerae Vavra and undeen (Microsporida: Nosematidae) pathogen of Culex pipiens L.(Diptera: Culicidae) from Egypt on fecundity and longevity of the host.

A microsporidian, Nosema algerae Vavra and undeen, was found parasitizing larvae and adults of a laboratory colony of Culex pipiens L. originated from Gharbia Governorate. A detailed examination of the developmental stages of the pathogen under light and electron microscopes showed that they are typical of the original characteristics of N. algerae. Other observations on the infected individuals revealed that spores of the pathogen were found in all organs of the infected mosquitoes except the nervous system. The most heavily infected organ was the alimentary canal, particularly the mid gut. The susceptibility of the different larval instars of a laboratory maintained Cx. pipiens colony to infection by N. algerae was determined. Using 24 hours exposure to a range of doses between 40 and 5 x 10(5) spores per cm, larvae of the 1st and 2nd instars were more susceptible to infection than 3rd and 4th instar larvae as indicated by the differences in the estimated IC50 dosages. The dosages of N. algerae which produced 50% mortality (LC50) in each group of treated larvae was approximately 25-30 times higher than the doses that caused 50% infection. When a sublethal dose of 1.2 x 10(3) spores per cm2 of N. algerae was used to induce infection in each of the different larval instars infection rates of 100% were obtained in all exposed larval instars and in adults developed from them. Females from larvae infected with N. algerae had significantly reduced fecundity, fertility, and longevity regardless the larval instar in which infection was initiated. However, the reduction was obviously high when 1st and 2nd instars were exposed. The accumulative effects of reduced survival and fecundity on the reproductive potential of the infected females derived from larvae that were infected as 1st and 2nd instars probably serve to limit the natural increase of mosquito populations. Further studies are necessary, however, to determine the efficacy of this pathogen on target species in the natural environment where the combined effect of the pathogen and environmental stresses may enhance its pathogenicity.

Animals↗
PubMedDate not supplied

[Pathogen-induced plant proteins].

Pathogen-induced plant proteins are classified by their functional characteristics: (a) involvement in plant cell signaling; (b) inhibition of enzymes excreted by the pathogens; (c) stabilization of plant cell walls or ability to trigger apoptosis; (d) enzymatic activity producing lysis of cell walls of pathogenic fungi and bacteria; (e) enzymatic activity in metabolic pathways of phenylpropane and terpene phytoalexins; and (f) ability to affect the pathogens directly, by disturbing the function of their cell membranes or by inactivating their ribosomes. Examples of transgenic plants with increased immunity against pathogens are also provided.

Plant Cells↗
PubMed2001

Epidemiological study of pathogenic fungi in China: 1986 and 1996.

OBJECTIVE: An annual decade epidemiological survey of pathogenic fungi of inpatients or outpatients includes more than 25 provinces in China has been done in 1986 and 1996. METHODS: In 1986, there were a total of 9096 strains of pathogenic fungi collected from more than 41 units of 25 provinces in China. 10 years late, 18,085 strains of pathogenic fungi from 41 units of 25 provinces were collected from January 1st to December 31st in 1996. RESULTS: The results showed that during this decade the prominent pathogenic fungus was Trichophyton rubrum, but its ratio gradually decreased. On the contrary, Candida albicans gradually increased in its ratio from 5th in 1986 to 2nd in 1996. CONCLUSION: The pathogenic fungi in China have changed greatly in the past decade from 1986 to 1996.

Candida albicans↗
PubMed2002

Determination of antimicrobial activity of Cefaclor on common respiratory tract pathogens in Pakistan.

OBJECTIVE: To determine the antimicrobial activity of Cefaclor against common respiratory tract pathogens isolated from patients in Pakistan. SETTING: Department of Microbiology, Liaquat National Postgraduate Medical Centre, Karachi. METHOD: A laboratory analysis was done on 466 isolates of respiratory tract pathogens collected from 13 laboratories from all over Pakistan. Antibiotic sensitivity test was done by Kirby Bauer disc diffusion method and MIC of Cefaclor was determined by 'E' test. RESULT: Of the 163 Streptococcus pneumoniae, 87 Moraxella catarrhalis and 216 Haemophilus influenzae > 95% isolates were susceptible to Cefaclor. The MIC 90 of all these pathogens were < 2 ug. CONCLUSION: Resistance of respiratory tract pathogens to the 2nd generation Cephalosporin, Cefaclor is very low. MIC 90 of Cefaclor against all three common respiratory tract pathogens is < 2 ug, which indicates that Cefaclor would be effective in more than 90% of cases infected with these bacteria.

Cefaclor↗
PubMed2002

A risk assessment of emerging pathogens of concern in the land application of biosolids.

Since the development of the United States Environmental Protection Agency's 503 biosolids Rule, which includes treatment requirements to reduce the threat of pathogen transmission, many new pathogens have been recognized which could be transmitted by biosolids. A risk analysis was performed assess which emerging pathogens would be most likely to survive treatments required for Class B biosolids before land application. The literature was reviewed on the resistance of emerging pathogens to temperature and other environmental factors to assess their probability of surviving various biosolids treatment processes. In addition existing information on occurrence in biosolids and dose response models for each pathogen was reviewed. It was concluded that adenoviruses and hepatitis A virus are the most thermally resistant viruses and can survive for prolonged periods in the environment. The protozoan parasites microsporidia and Cyclospora were unlikely to survive the temperatures achieved in anaerobic digestion and do not survive well under low moisture conditions. A risk model was used to assess the risk of infection and illness from enteric viruses after application of class B biosolids.

Adenoviridae↗
PubMedDate not supplied

[Pathogenicity islands in opportunistic Enterobacteria].

The presence of fragments of genomes hlyA, hlyB, papAH, papC, sfaG, sfaA and kps MT, associated with the pathogenicity islands of Escherichia coli, in clinical strains of other genera of the family Enterobacteriaceae, has been experimentally evaluated with the use of PCR. The presence of DNA fragments specific to the known genes of the pathogenicity clusters of E. coli in representatives of the genera Citrobacter, Enterobacter, Hafnia, Klebsiella, Morganella, Proteus, Providencia, Serratia and Yersinia of rarely occurring groups has been established. In Enterobacteriaceae cultures isolated from the intestine amplicons homologous to hlyB were detected significantly less frequently than among strains of nonintestinal origin. In Enterobacteriaceae strains isolated in respiratory pathology amplicons of the pili gene (sfaG) were detected significantly more frequently than in collection cultures. The total evaluation of the detection rate of the genes of pathogenicity islands among Enterobacteriaceae clinical strains under study in comparison with E. coli showed that they occurred significantly less frequently. Klebsiella spp. were found to differ most essentially from E. coli as regards the occurrence of fragments of the genes of pathogenicity islands. The conclusion was made on the high probability of genetic exchange in DNA fragments between different species of bacteria with corresponding changes in their pathogenicity.

Bacterial Proteins↗
PubMed2003

Interaction of pathogens with the endothelium.

The endothelium lines the inner surface of the vessel wall establishing a multifunctional, semi-permeable cellular barrier at blood-tissue interface. The large total surface of the endothelium is exposed to pathogens, pathogen-derived products as well as to agents of the activated host defense during an inflammatory reaction. The endothelium is not only specifically targeted by important infective agents like Rickettsiae (1) or Bartonella (2), it is involved in virtually most, if not all, acute inflammatory responses. Pathogens attack the endothelium by a wide variety of strategies, as different as activation of preformed receptor-mediated pathways in the endothelium, release of pore-forming exotoxins or intracellular replication and chronic parasitism. These pathophysiological forces affect the endothelial phenotype, resulting in endothelial barrier dysfunction, increased leukocyte-endothelial interaction, mediator release, and procoagulant activity. Moreover, endothelial responses retroact on the invading pathogen as well as on the host defense resulting in a complex and dynamic interaction. Endothelial activation contributes considerably to inflammation and resulting clinical characteristics. In this context the endothelium is not just a passive victim, it rather aggravates the ongoing struggle with the pathogen. In this review we focus on some important mechanisms of the cellular microbiology of endothelial infection by bacteria and viruses.

Animals↗
PubMed2003

[Vulvovaginal candidiasis and sensitivity of pathogens to antimycotics].

OBJECTIVE: Analysis of the prevalence and species representation of pathogenic yeasts in patients with vulvovaginal candidiasis. Determination of in vitro susceptibility of yeast isolates to clinically used antimycotic agents. DESIGN: A retrospective clinical study of patients with positive vaginal cultures for the presence of pathogenic yeast species. SETTING: I. gynekologicko-pôrodnícka klinika LF UK a FN, Zochova 7,811 03 Bratislava, Slovenská republika. METHODS: Identification of yeast pathogens on the chromogenic medium CHROMagar CANDIDA and with API-CANDIDA identification system. In vitro susceptibility assays of clinical yeast isolates to antifungal agents using the plate dilution method, NCCLS method and ATB-FUNGUS test system. RESULTS: The highest prevalence of vulvovaginal candidasis was found in women aged between 20-30 years. Candida albicans was the most commonly identified species of pathogenic yeasts (87.4%). Of the non-albicans species, C. glabrata (6.3%) was the most prevalent species. C. glabrata and C. krusei clinical isolates were found to be generally less susceptible to several antifungals in vitro as compared to C. albicans strains. A minimal number of resistant yeast isolates was observed for econazole, clotrimazole and nystatin. A relatively high number of resistant strains was observed for some other azole antifungals (miconazole, ketoconazole, itraconazole, fluconazole). CONCLUSION: A successful treatment of vaginal mycotic infections requires the results of the microbiological analyses. They will bring evidence to a physician of the presence and fate of the pathogen, of its sensitivity to antifungals, both of which are essential for the rational and successful therapy of Candida vaginitis.

Adult↗
PubMed2002

Use of restriction endonucleases for differentiation of pathogenic & saprophytic leptospires.

BACKGROUND & OBJECTIVES: PCR has been reported for amplification of the 482 bp genus specific region in 23S rRNA gene of Leptospira species. The sequence of this region was analyzed for specific restriction sites that could have yielded digestion products expected to provide differentiating banding profile for the pathogenic and the saprophytic group of leptospires. METHODS: Sixteen standard serovars of pathogenic group, two standard serovars of saprophytic group, 12 Leptospira isolates recovered from hospitalized patients with fever and jaundice or pyrexia of unknown origin and 23 isolates from different water sources were studied. Conventional tests, PCR methods and restriction digestion were used for confirming the identity of these isolates. RESULTS: All 12 isolates from patients and 1 from tap water source were identified as pathogenic and 22 isolates from water sources as saprophytic by the conventional tests and PCR. Of the 5 restriction endonuclease enzymes, viz, Apa I, Ban II, Hae III, Pst I and Sin I analyzed for digestion of PCR amplified 482 bp product, Apa I, Ban II, Pst I and Sin I provided fragments of different sizes providing distinct patterns for saprophytic and pathogenic leptospires. INTERPRETATION & CONCLUSION: The identity of a strain to genus Leptospira could be confirmed by PCR amplification of 482 bp region of 23S rRNA and with further restriction digestion a clear distinction into pathogenic or saprophytic group was achieved with the use of any of these 4 restriction enzymes.

Base Sequence↗
PubMedDate not supplied

[Avian pathogenic Escherichia coli (APEC)].

Infections with avian pathogenic Escherichia coli (APEC) cause colibacillosis, an acute and mostly systemic disease resulting in significant economic losses in poultry industry worldwide. Avian colibacillosis is a complex syndrome characterized by multiple organ lesions with airsacculitis and associated pericarditis, perihepatitis and peritonitis being most typical. Environmental factors as well as the constitution of poultry or initial viral infections influence the outcome of APEC-infections. However, several challenge experiments in chickens proofed the role of virulent APEC strains as the single aetiological agent. Currently serotypes O1:K1, O2:K1 and O78:K80 are recognized as the most prevalent, however the number of published serotypes is increasing. In addition, single APEC isolates vary profoundly in virulence, and knowledge about the molecular basis of this variability is still scarce. Known virulence factors of APEC are adhesins (F1- and P-fimbriae), iron acquisition systems (aerobactin and yersiniabactin), hemolysins (hemolysinE and temperaturesensitive hemagglutinin), resistance to the bactericidal effects of serum and phagocytosis (outer membrane protein, iss protein, lipopolysaccharide, K/1)-capsule and colilcin production) as well as toxins and cytotoxins (heat stable toxin, cyto-/verotoxin and flagella toxin). Esperimental studies have shown that the respiratory tract, principally the gas-exchange region of the lung and the interstitium of the air sacs are the most important sites of entry for avian pathogenic E. coli. APEC strains adhere to the epithelial cells of air sacs presumably through F1-fimbriae. After colonization and multiplication the bacteria enter the bloodstream, and the temperature-sensitive hemagglutinin (tsh) seems to be important int his step. After invading the bloodstream APEC cause a septicemia resulting in massive lesins in multiple internal organs and in sudden death of the birds. The ability of the bacteria to acquire iron and the resistance to the bactericidal effects of serum, predominantly conferred by the increased serum survival (iss)--protein, enables APEC to multiply quickly in their hosts. Iss is regarded a specific genetic marker for avian pathogenic E. colistrains. A critical review of the literature published so far on APEC reveals, that these pathotypes are not defined appropriately. This findings urge investigations on the population structure of APEC, enabling the establishment of appropriate diagnostic tools and avoiding the obsolete use of serotyping for APEC diagnosis. So far more than 20 APEC strains have been investigated in animal experiments, explaining contrary published results. Thus, the lack of knowledge in pathogenicity and in immunity of APEC infections urges further experimental studies. As APEC share not only identical serotypes with human pathogens but also specific virulence factors, their zoonotic potential is under consideration.

Adhesins, Escherichia coli↗
PubMedDate not supplied

Re-evaluation of the pathogenicity of A/chicken/Alabama/75 (H4N8) influenza virus.

Avian influenza (AI) virus A/chicken/Alabama/7395/75 (H4N8), a putatively non-pathogenic virus associated with a self-limiting outbreak of severe disease in commercial layers, was selectively passed in chickens or in cell cultures and then in chickens to determine whether virus with increased pathogenicity would emerge. When 20 derivatives of the parental virus were each inoculated intranasally and intratracheally in leghorn hens, mortality rates ranged from zero (0/24) to 25% (6/24); mortality was 4% (1/24) for hens inoculated with the parental virus. Many virus reisolates (51/144) from hens that died exhibited high pathogenicity, killing at least six of eight intravenously inoculated 4-week-old chickens. Most derivatives examined produced plaques in trypsin-free cell cultures more efficiently than the parental virus, but the highest plaquing efficiencies observed (10%) were lower than would be expected (100%) for highly pathogenic subtype H5 or H7 AI viruses. These results confirm that the Alabama H4N8 virus can acquire increased pathogenicity upon passage in chickens and suggest that it may have acted alone in producing the severe disease observed in laying chickens in Alabama.

Animals↗
PubMed2003

[The nematode Caenorhabditis elegans as a model for the study of host-pathogen interactions].

For certain pathogens capable of infecting a broad range of organisms, there exist universal virulence factors, necessary for full pathogenicity regardless of the host. This has been most clearly demonstrated by Ausubel and colleagues for the human opportunistic pathogen Pseudomonas aeruginosa. As a consequence, one can use non-mammalian model systems, including the nematode worm Caenorhabditis elegans, to assay for such virulence factors. A significant number of pathogens of C. elegans, that provoke a range of diseases, are now known, including the opportunistic human pathogen Serratia marcescens. After explaining the practical advantages associated with the use of C. elegans, and briefly reviewing previous studies, the results of a screen for S. marcescens virulence factors will be presented.

Animals↗
PubMed2003

Emerging food pathogens and bacterial toxins.

Many different foodborne diseases have been described. For example, Shigella bacteria, hepatitis A virus and Norwalk virus were shown as a unwashed hands microorganisms, but pathogen Campylobacter and Escherichia coli were named as raw and undercooked meat and poultry or raw milk and untreated water born bacteria. However, two of them: Listeria monocytogenes and Yersinia enterocolitica are known as growing at refrigerator temperatures. Essential virulence determinants of Listeria monocytogenes pathogenicity are well known as a bacterial toxins. Basic molecular mechanisms of pathogenicity depending from these toxins were presented. It was shown that other bacterial toxins may act as very danger food poisoning substances. This is why elimination of pathogenic microorganisms from foods is an obvious solution in some food processes, however this approach is not practical or even desirable in many processes. Thus, risk assessment and microbial monitoring will continue to play important roles in ensuring food safety. Some technological advances have the capability of delivering detection systems that can not only monitor pathogenic microorganisms, but also entire microbial populations in the food matrix.

Bacterial Toxins↗
PubMed2003

The impact of "ancient pathogen" studies on the practice of public health.

A new field of "ancient pathogens" is making an impact on our concepts of the evolution of infectious diseases, and it will eventually alter the practice of public health in their control. It has begun to answer important questions regarding past epidemics of influenza and tuberculosis by recovering the genetic sequences of the ancient causative agents. Vaccination strategics will have to study these microbial variants in order to develop tomorrow's vaccines. It may also be possible to examine the role of past and present reservoirs in the dynamics of emerging diseases. In unraveling the evolution of pathogens, insights into the mechanisms of drug and antibiotic resistance are possible. As "genome projects" of more and more pathogens are being completed. Targets for chemotherapy are being revealed which are totally different from the metabolic processes of the mammalian host. Signal molecules are being identified which alter the virulence of the microbe. Focussing on these mechanisms without attempting to kill the pathogen may in some cases drive it into a benign state. These and other aspects of the evolution of pathogens are discussed which may lead to innovative approaches to the control of infectious diseases.

Biological Evolution↗