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PubMed2006

Conserved genes in a path from commensalism to pathogenicity: comparative phylogenetic profiles of Staphylococcus epidermidis RP62A and ATCC12228.

BACKGROUND: Staphylococcus epidermidis, long regarded as an innocuous commensal bacterium of the human skin, is the most frequent cause of nosocomial infections associated with implanted medical devices. This conditional pathogen provides a model of choice to study genome landmarks correlated with the transition between commensalism and pathogenicity. Traditional investigations stress differences in gene content. We focused on conserved genes that have accumulated small mutation differences during the transition. RESULTS: A comparison of strain ATCC12228, a non-biofilm forming, non-infection associated strain and strain RP62A, a methicillin-resistant biofilm clinical isolate, revealed consistent variation, mostly single-nucleotide polymorphisms (SNPs), in orthologous genes in addition to the previously investigated global changes in gene clusters. This polymorphism, scattered throughout the genome, may reveal genes that contribute to adaptation of the bacteria to different environmental stimuli, allowing them to shift from commensalism to pathogenicity. SNPs were detected in 931 pairs of orthologs with identical gene length, accounting for approximately 45% of the total pairs of orthologs. Assuming that non-synonymous mutations would mark recent evolution, and hence be associated to the onset of the pathogenic process, analysis of ratios of non-synonymous SNPs vs synonymous SNPs suggested hypotheses about possible pathogenicity determinants. The N/S ratios for virulence factors and surface proteins differed significantly from that of average SNPs. Of those gene pairs, 40 showed a disproportionate distribution of dN vs dS. Among those, the presence of the gene encoding methionine sulfoxide reductase suggested a possible involvement of reactive oxygen species. This led us to uncover that the infection associated strain was significantly more resistant to hydrogen peroxide and paraquat than the environmental strain. Some 16 genes of the list were of unknown function. We could suggest however that they were likely to belong to surface proteins or considered in priority as important for pathogenicity. CONCLUSION: Our study proposed a novel approach to identify genes involved in pathogenic processes and provided some insight about the molecular mechanisms leading a commensal inhabitant to become an invasive pathogen.

Bacterial Proteins↗

PubMed2004

Variation suggestive of horizontal gene transfer at a lipopolysaccharide (lps) biosynthetic locus in Xanthomonas oryzae pv. oryzae, the bacterial leaf blight pathogen of rice.

BACKGROUND: In animal pathogenic bacteria, horizontal gene transfer events (HGT) have been frequently observed in genomic regions that encode functions involved in biosynthesis of the outer membrane located lipopolysaccharide (LPS). As a result, different strains of the same pathogen can have substantially different lps biosynthetic gene clusters. Since LPS is highly antigenic, the variation at lps loci is attributed to be of advantage in evading the host immune system. Although LPS has been suggested as a potentiator of plant defense responses, interstrain variation at lps biosynthetic gene clusters has not been reported for any plant pathogenic bacterium. RESULTS: We report here the complete sequence of a 12.2 kb virulence locus of Xanthomonas oryzae pv. oryzae (Xoo) encoding six genes whose products are homologous to functions involved in LPS biosynthesis and transport. All six open reading frames (ORFs) have atypical G+C content and altered codon usage, which are the hallmarks of genomic islands that are acquired by horizontal gene transfer. The lps locus is flanked by highly conserved genes, metB and etfA, respectively encoding cystathionine gamma lyase and electron transport flavoprotein. Interestingly, two different sets of lps genes are present at this locus in the plant pathogens, Xanthomonas campestris pv. campestris (Xcc) and Xanthomonas axonopodis pv. citri (Xac). The genomic island is present in a number of Xoo strains from India and other Asian countries but is not present in two strains, one from India (BXO8) and another from Nepal (Nepal624) as well as the closely related rice pathogen, Xanthomonas oryzae pv. oryzicola (Xoor). TAIL-PCR analysis indicates that sequences related to Xac are present at the lps locus in both BXO8 and Nepal624. The Xoor strain has a hybrid lps gene cluster, with sequences at the metB and etfA ends, being most closely related to sequences from Xac and the tomato pathogen, Pseudomonas syringae pv. tomato respectively. CONCLUSION: This is the first report of hypervariation at an lps locus between different strains of a plant pathogenic bacterium. Our results indicate that multiple HGT events have occurred at this locus in the xanthomonad group of plant pathogens.

Base Sequence↗

PubMed2003

Pathogen survival trajectories: an eco-environmental approach to the modeling of human campylobacteriosis ecology.

Campylobacteriosis, like many human diseases, has its own ecology in which the propagation of human infection and disease depends on pathogen survival and finding new hosts in order to replicate and sustain the pathogen population. The complexity of this process, a process common to other enteric pathogens, has hampered control efforts. Many unknowns remain, resulting in a poorly understood disease ecology. To provide structure to these unknowns and help direct further research and intervention, we propose an eco-environmental modeling approach for campylobacteriosis. This modeling approach follows the pathogen population as it moves through the environments that define the physical structure of its ecology. In this paper, we term the ecologic processes and environments through which these populations move "pathogen survival trajectories." Although such a modeling approach could have veterinary applications, our emphasis is on human campylobacteriosis and focuses on human exposures to Campylobacter through feces, food, and aquatic environments. The pathogen survival trajectories that lead to human exposure include ecologic filters that limit population size, e.g., cooking food to kill Campylobacter. Environmental factors that influence the size of the pathogen reservoirs include temperature, nutrient availability, and moisture availability during the period of time the pathogen population is moving through the environment between infected and susceptible hosts. We anticipate that the modeling approach proposed here will work symbiotically with traditional epidemiologic and microbiologic research to help guide and evaluate the acquisition of new knowledge about the ecology, eventual intervention, and control of campylobacteriosis.

Animals↗

PubMed2005

Recovery of potential pathogens and interfering bacteria in the nasopharynx of smokers and nonsmokers.

BACKGROUND: Active smoking and passive exposure to cigarette smoke are associated with colonization by some potentially pathogenic species of bacteria and an increased risk of respiratory tract infection in both adults and children. In an attempt to explain these observations, this study compared the frequency of isolation of potential pathogens, and aerobic and anaerobic bacteria that possess interfering capabilities (ie, interfering with the in vitro growth of potential pathogens) in the nasopharynx of smokers to their recovery in nonsmokers. METHODS: Nasopharyngeal specimens for cultures were taken from 20 smokers and 20 nonsmokers. Potential pathogens, and aerobic and anaerobic bacteria with interfering capabilities against these organisms were identified. RESULTS: Fourteen potential pathogens (0.7 per patient) were isolated from nasopharyngeal cultures obtained from 11 of the 20 smokers, and 4 (0.2 per patient) were recovered from 3 of the 20 nonsmokers (p < 0.01). In vitro bacterial interference between two aerobic (alpha-hemolytic and nonhemolytic streptococci) and two anaerobic species (Prevotella and Peptostreptococcus species), and four potential pathogens (Streptococcus pneumoniae, Haemophilus influenzae [non-type b], Moraxella catarrhalis, and Streptococcus pyogenes) was observed. Bacterial interference was noted in 61 instances against the four potential pathogens by 22 normal flora isolates that were recovered from the group of smokers, and in 155 instances by 50 isolates from the group of nonsmokers (p < 0.01). CONCLUSIONS: These findings illustrate for the first time that the nasopharyngeal flora of smokers contains fewer aerobic and anaerobic organisms with interfering capabilities and more potential pathogens compared with those of nonsmokers.

Adult↗

PubMed2004

Antibody regulation of Tcell immunity: implications for vaccine strategies against intracellular pathogens.

Intracellular microbial pathogens cause a plethora of diseases that pose a huge public health challenge. Efficacious prophylactic vaccines are needed to protect the population from this myriad of infectious diseases. Contemporary approaches to vaccine design are guided by the immunobiological paradigm that extracellular pathogens are controlled principally by humoral immunity, involving specific antibodies, whereas host protection against intracellular pathogens requires effectors of cell-mediated immunity. However, this distinct T-helper (Th) type 1 and 2 paradigm of host defense has encountered a major challenge due to the reality that most antigens or vaccines induce mixed immune responses comprising of both humoral and CMI effectors. Besides, the true functional independence of antibodies and T-cells under in vivo physiologic conditions is uncertain. Recent findings have revealed that antibodies exert a significant immunoregulatory effect on T-cell immunity. Thus, a robust and protective T-cell memory response against microbial pathogens such as Chlamydia and Mycobacteria require an effective primary humoral immune response characterized by specific antibody isotypes whose role is to modulate Th1 activation via Fc receptors (FcR) by facilitating a rapid uptake, processing and presentation of pathogen-derived antigens for an enhanced T-cell response. These findings have crystallized into a paradigm shift in host defense wherein different components of the apparently disparate mixed immune responses elicited against a microbial pathogen function concertedly to maximize the principal effector mechanism. This review focuses on the essential role of both arms of the immune system in controlling intracellular microbial pathogens, especially the regulatory role of FcR-mediated antibody function in optimizing the induction of a protective Th1 response. The immunobiological implications are discussed in the context of vaccine design, delivery and evaluation against intracellular microbial pathogens of bacteria, fungi and parasitic origin.

Animals↗

PubMed2004

Effective targeting of pathogens to neutrophils via chimeric surfactant protein D/anti-CD89 protein.

Targeting of specific pathogens to FcRs on immune effector cells by using bispecific Abs was reported to result in effective killing of the pathogens, both in vitro and in vivo. Instead of targeting a specific pathogen to an FcR, we assessed whether a broad spectrum of pathogens can be targeted to an FcR using surfactant protein D (SP-D). SP-D is a collectin that binds a great variety of pathogens via its carbohydrate recognition domain. A recombinant trimeric fragment of SP-D (rfSP-D), consisting of the carbohydrate recognition domain and neck domain of human SP-D, was chemically cross-linked to the Fab' of an Ab directed against the human Fc alpha RI (CD89). In vitro, the chimeric rfSP-D/anti-CD89 protein enhanced uptake of Escherichia coli, Candida albicans, and influenza A virus by human neutrophils. Blocking of the interaction between rfSP-D/anti-CD89 and either the pathogen or CD89 abolished its stimulatory effect on pathogen uptake by neutrophils. In addition, rfSP-D/anti-CD89 stimulated killing of E. coli and C. albicans by neutrophils and enhanced neutrophil activation by influenza A virus. In conclusion, rfSP-D/anti-CD89 effectively targeted three structurally unrelated pathogens to neutrophils. (Col)lectin-based chimeric proteins may thus offer promise for therapy of infectious disease.

Animals↗

PubMed2003

Spread of bacterial pathogens during preparation of freshly squeezed orange juice.

To study the potential of three bacterial pathogens to cross-contaminate orange juice during extraction, normal operation conditions during juice preparation at food service establishments were simulated. The spread of Salmonella enterica serovar Typhimurium, Escherichia coli O157:H7, and Listeria monocytogenes from inoculated oranges to work surfaces and to the final product was determined. The transference of these three bacterial pathogens to orange juice made from uninoculated oranges with the use of contaminated utensils was also studied. Fresh oranges were inoculated with a marker strain of rifampicin-resistant Salmonella Typhimurium, E. coli O157:H7, or L. monocytogenes. Final pathogen levels in juice were compared as a function of the use of electric or mechanical juice extractors to squeeze orange juice from inoculated oranges. Pathogen populations on different contact surfaces during orange juice extraction were determined on sulfite-phenol red-rifampicin plates for Salmonella Typhimurium and E. coli O157:H7 and on tryptic soy agar supplemented with 0.1 g of rifampicin per liter for L. monocytogenes. After inoculation, the average pathogen counts for the orange rind surface were 2.3 log10 CFU/cm2 for Salmonella Typhimurium, 3.6 log10 CFU/cm2 for E. coli O157:H7, and 4.4 log10 CFU/cm2 for L. monocytogenes. This contamination was spread over all utensils used in orange juice squeezing. Mean pathogen counts for the cutting board, the knife, and the extractor ranged from -0.3 to 2.1 log10 CFU/cm2, and the juice contained 1.0 log10 CFU of Salmonella Typhimurium per ml, 2.3 log10 CFU of E. coli O157:H7 per ml, and 2.7 log10 CFU of L. monocytogenes per ml. Contact with contaminated surfaces resulted in the presence of all pathogens in orange juice made from uninoculated oranges. These results give emphasis to the importance of fresh oranges as a source of pathogens in orange juice.

Beverages↗

PubMed2006

Radiation sensitivity and postirradiation growth of foodborne pathogens on a ready-to-eat frankfurter on a roll product in the presence of modified atmosphere and antimicrobials.

Intervention technologies including ionizing radiation, antimicrobials, and modified atmospheres (MA) can be used to inhibit the growth of or inactivate foodborne pathogens on complex ready-to-eat foods such as sandwiches. However, the effect of these technologies when used in combination (the hurdle concept) on the survival of foodborne pathogens is unknown. The ability of ionizing radiation to inactivate Escherichia coli O157:H7, Salmonella, Listeria monocytogenes, and Staphylococcus aureus inoculated onto a frankfurter on a roll product containing the antimicrobials sodium diacetate and potassium lactate in the presence of an MA (100% N2, 50% N2 plus 50% CO2, or 100% CO2) was investigated. The radiation resistances (D10-values) of the foodborne pathogens were 0.43 to 0.47 kGy for E. coli O157:H7, 0.61 to 0.71 kGy for Salmonella, 0.53 to 0.57 for L. monocytogenes, and 0.56 to 0.60 for S. aureus. The MA had no effect on the radiation resistance of the pathogens. During a 2-week storage period under mild temperature abuse (10 degrees C), none of the pathogens were able to proliferate on the frankfurter on a roll product, regardless of the MA used. However, application of sublethal doses of ionizing radiation resulted in increased mortality of the gram-positive pathogens L. monocytogenes and S. aureus during the storage period regardless of the MA. Although the pathogens were unable to proliferate on the frankfurter on a roll product during the storage period, application of a postpackaging intervention step was needed to actually inactivate the foodborne pathogens. Ionizing radiation used in combination with sodium diacetate and potassium lactate resulted in additional mortality of L. monocytogenes and S. aureus, independent of the MA, during the 2-week storage period.

Carbon Dioxide↗

PubMedDate not supplied

[The factors of bacterial pathogenicity and their role in the development of the infectious process].

The latest data concerning the characterization of the pathogenicity factors of bacteria and the evaluation of their role in the realization of definite phases of the development of the infectious process are presented. The infectious process is regarded as the result of the complicated simultaneous interaction of microorganisms and different cells and tissues of the host body. The problems of the polydeterminant character of pathogenicity factors, tho possibility of the joint action of different factors at one and the same stage of the development of the infectious process and, vice versa, the action of the same factors at different stages of the interaction of the infective agent and the susceptible host are discussed. Modern data on the genetic control of pathogenicity factors, on the localization of their genetic determinants on the chromosome and the virulence plasmids, information of pathogenicity "islets" which jointly determine the pathogenic potential of the infective agent are given. The emphasis is made on fact that the general principle of the genetic control of bacterial pathogenicity is complicated relationship between chromosomal and nonchromosomal determinants; some of them form a part of genetic pathogenicity "islets", simultaneously regulating and expressing the pathogenicity factors of the infective agent.

Bacteria↗

PubMed2000

Identification of enteric pathogens in HIV-positive patients with diarrhoea in northern India.

Enteric pathogens associated with chronic diarrhoea in HIV-positive patients were studied. The study was conducted during January 1995-December 1998. Stool specimens from all diarrhoea patients (n = 26) were examined microscopically for ova and parasites using wet preparations and stained smears. Stool samples from diarrhoea patients were also cultured on appropriate media to isolate enteric bacterial pathogens. Of the 59 patients, 26 (44%) had prolonged diarrhoea for more than 4 weeks. Enteric pathogens were detected in 19 (73%) of the 26 patients: 17 patients harboured a single pathogen, and 2 patients had mixed pathogens. The detection rate of emerging parasites, including Isospora, Cryptosporidium, Blastocystis hominis, and Strongyloides stercoralis as a single agent, was significantly higher than conventional pathogens (50% vs 19.2%; p < 0.05). Only one patient harboured both conventional and emerging pathogens (Entamoeba histolytica and Cryptosporidium). Isospora belli was detected in 8 (31%) of the 26 diarrhoea patients: in 7 (27%) patients as a single agent and in one patient with S. stercoralis. Cryptosporidium was identified in 3 (11%) diarrhoea patients: in 2 (8%) patients as a single agent and in one patient with E. histolytica, followed by B. hominis in 2 (8%) patients. E. histolytica was most commonly isolated (3/26; 11.5%), followed by Giardia lamblia, enteropathogenic Escherichia coli, and Campylobacter jejuni (one patient each). Parasitic pathogens were frequently associated with HIV-positive patients with diarrhoea in northern India. I. belli was the most frequent parasite isolated, followed by Cryptosporidium. Stools of all HIV-positive patients with diarrhoea should thoroughly be investigated to identify aetiologic agents for proper management.

AIDS-Related Opportunistic Infections↗

PubMed1975

Pathogenicity for several laboratory animals of toxoplasma oocysts originated from naturally infected cats.

The pathogenicity of four strains, O-1, O-2, O-3, and O-4, of Toxoplasma isolated in the form of oocyst from the feces of naturally infected cats was examined for such laboratory animals as mice, rats, rabbits, guinea pigs, and dogs, in comparison with that of the Beverley strain. Suspensions of seven graded doses of oocysts of each strain ranging from 1.0 X 10(-1) to 1.0 X 10(5) were inoculated orally into seven groups of five mice each. The O-1, O-2, and O-3 strains were as pathogenic for mice as the Beverley strain, but the O-4 strain was not so pathogenic as any other strain. Rats, rabbits, guinea pigs, and dogs were inoculated orally with around 1.0 X 10(5) oocysts. The four O strains were not so severly pathogenic for rats and rabbits as to cause death. The O-2 and O-3 strains showed strong pathogenicity for guinea pigs, almost all of which, when inoculated with them, died after manifesting severe clinical symptoms. The pathogenicity of the O-1 and O-2 strains showed essentially the same tendency for dogs as for any other animal. In inoculation with oocysts, as well as with proliferative forms or cysts, the same pathogenicity was not observed in different strains, even if the same species of host animals was used. On the contrary, the same pathogenicity was not always found even in one strain when a different species of animals was used.

Administration, Oral↗

PubMed2002

[Changes of pathogenic bacteria in pediatric patients of septicemia and drug resistance there of in Zhejiang Children's Hospital 1991 approximately 2000].

OBJECTIVE: To investigate the changes of pathogenic bacteria detected from the blood culture of pediatric patients with septicemia in the past 10 years, and to observe the drug resistance thereof in the past two years. METHODS: The blood samples of 4 425 pediatric patients aged 0 approximately 14 with the diagnosis of septicemia 1991 approximately 2000 in Zhejiang Children's Hospital were cultured in broth (1991 approximately 1996) or VITA AER blood culture apparatus (1997 approximately 2000). Analytic Product Inc. (API ) system and KB paper strip method and VITEK automicroscan were used to identify the species and conduct drug resistance test. The results were interpreted according to the guideline of National Committee for Clinical Laboratory Standards. RESULTS: In the past 10 years, Gram-positive bacteria remained the more frequent pathogens than Gram-negative bacteria in pediatric patients with septicemia. The proportion of coagulase-negative staphylococcus (CNS) had been increasing and reached 69% in 2000. The proportions of Staphylococcus aureus and Escherichia coli decreased from 35.4% and 18.2% in 1991 to 5.3% and 1.5% in 2000. In the past two years, the drug resistance rate of staphylococci against penicillin and erythromycin were more than 90% and 70% respectively. The oxacillin resistance rate of CNS was 60.3%, significantly higher than that of Staphylococcus aureus (10.3%). No strain of Staphylococcus and Enterococcus resistant to vancomycin was found. Escherichia coli and Psudomonas aeruginosa and other species of Enterobacteriae were sensitive to imipenem/cilastin sodium, whereas the resistance rate of them to ampicillin and first generation cephalosporins was more than 50%. CONCLUSION: (1) Gram-positive bacteria are the predominant pathogens of pediatric patients with septicemia, with the species of Staphylococcus ranking first among which CNS is the main pathogen for infants and Staphylococcus aureus is the main pathogen for school children. (2) Escherichia coli is the most frequently found pathogenic Gram-negative bacterium in infants with septicemia whereas Salmonella in school children. (3) Drug resistance of isolated pathogenic bacteria in department of pediatrics is a serious problem. Monitoring the change of pathogen and the trends of antimicrobial resistance is very important in guiding therapy.

Adolescent↗

PubMed2003

[The functional role of arterial intima. Endogenous and exogenous pathogens and specificity of atheromatosis as an inflammation].

We believe that the intima is a biological filter accountable for arresting the endogenous and exogenous pathogens, which activate the biological function of inflammation, and for preventing the access of pathogens into the internal-space intercellular pool. The below described biological reactions occur in the arterial intima: trans-cytosis of pathogens by endothelial cells onto the intima surface; sorption of pathogens into the filter proteoglycan matrix; destruction of the matrix by macrophage metalloproteinases; desorption of pathogens with matrix elements by resident macrophages through squewenjer-receptor endocytosis; proteolysis of pathogens in lysosomes; retroendocytosis of non-hydrolyzed components of pathogens into the intercellular medium; and a recovery of the integrity of proteoglycan matrix by the smooth-muscle cells. Sorption and desorption of pathogens (i.e. modified low-density lipoproteins who carry the essential polyene fat acids to cells) by resident macrophages (from the filter) under the conditions of the blockade of apoB-100-receptoral endocytosis predetermine the specificity of atheromatosis as an inflammation.

Arteries↗

PubMed2006

[A multicentre study on the pathogenic agents in 665 adult patients with community-acquired pneumonia in cities of China].

OBJECTIVE: To investigate the pathogenic causes of community-acquired pneumonia (CAP) in adult patients in China, the relation of previous antibiotic use and the Pneumonia Patient Outcome Research Team (PORT) classification to microbial etiology, and the prevalence of drug resistance of common CAP bacteria. METHODS: A prospective study was performed on 665 consecutive adult patients with CAP at 12 centers in 7 Chinese cities during one year. The etiology of pneumonia was considered if one of the following criteria was met: (1) valid sputum sample yielding one or more predominant strains; (2) blood cultures yielding a bacterial pathogen; (3) seroconversion, a > or = 4-fold increase or decrease titers of antibodies to Mycoplasma pneumoniae, Chlamydia pneumoniae and Legionella pneumophila. Minimum inhibitory concentration (MIC) of respiratory tract isolates was determined using the agar dilution method. RESULTS: Pathogens were identified in 324/610 patients (53.1%) with valid serum samples and sputum cultures as follows: Mycoplasma pneumoniae (126, 20.7%), Streptococcus pneumoniae (63, 10.3%), Haemophilus influenzae (56, 9.2%), Chlamydia pneumoniae (40, 6.6%), Klebsiella pneumoniae (37, 6.1%), Legionella pneumophila (31, 5.1%), Staphylococcus aureus (23, 3.8%), Escherichia coli (10, 1.6%), Moraxella catarrhalis (8, 1.3%), Pseudomonas aeruginosa (6, 1.0%). Of 195 patients with a bacterial pathogen, an atypical pathogen was identified in 62 (10.2%) cases. The non-susceptibility rate of Streptococcus pneumoniae to penicillin, azithromycin, and moxifloxacin was 20.3%, 75.4% and 4.3% respectively. CONCLUSIONS: Atypical pathogens have important role in CAP, with Mycoplasma pneumoniae being the most common pathogen, and mixed infection of atypical pathogens with bacteria was found in 10.2% of the cases. Streptococcus pneumoniae and Haemophilus influenzae remain the most important bacteria for CAP. More than 75.0% of Streptococcus pneumoniae was resistant to macrolides and 20.3% was resistant to penicillin.

Adult↗

PubMed1988

Frequency of isolation of environmental mastitis-causing pathogens and incidence of new intramammary infection during the nonlactating period.

Quarter samples (n = 6,328) of mammary secretions were collected from 160 cows during physiologic transitions of the udder to determine the frequency of isolation of mastitis-causing pathogens and the incidence of new intramammary infections (IMI) during the nonlactating period. None of the cows in the herd was infected with Streptococcus agalactiae, and the prevalence of Staphylococcus aureus was low. Cows were not treated with antibiotics at cessation of milking. A threefold increase in the percentage of quarters infected with major mastitis-causing pathogens developed from late lactation to early involution. Coliforms and streptococci other than Str agalactiae accounted for 94% of major pathogen infections. The number of quarters infected with coagulase-negative staphylococci increased slightly from late lactation to early involution, whereas the number of quarters infected with Corynebacterium bovis decreased markedly. Major pathogens caused 101 of 153 IMI at parturition and greater than 90% were caused by streptococci and coliforms. At parturition, 51 of 52 minor pathogen IMI were caused by coagulase-negative staphylococci. During early lactation, there was a marked decrease in quarters infected with major pathogens; however, the number of quarters with major pathogen IMI during early lactation was 2.3 times higher than the number of quarters infected before cessation of milking. The number of quarters with minor pathogen IMI during early lactation was the same as at parturition, but a marked decrease in quarters infected with coagulase-negative staphylococci and a marked increase in C bovis IMI developed from parturition to early lactation.

Animals↗

PubMed1983

Candida adherence to mucosal epithelial cells with regard to its pathogenicity.

Twelve Candida strains were tested to compare their ability to adhere to human buccal and vaginal mucosa epithelial cells in vitro. The tests were performed in 0.9% saline and in phosphate buffer with both kinds of cells and additionally in saliva with buccal cells. The time of incubation was either 30 or 90 min. The pathogenicity of all of the fungal strains had been evaluated previously using viability test in mice. Eight strains were found to be pathogenic while four strains were considered to be not pathogenic. Out of the pathogenic ones, 5 strains of C. albicans, two strains of C. guilliermondi and one strain of C. stellatoidea were found. Non-pathogenic single strains were identified as C. krusei, C. parapsilosis, C. pseudotropicalis and C. tropicalis. The adherence tests with the pathogenic strains revealed significantly higher values for vaginal epithelial cells after 30 as well as after 90 min of incubation both in phosphate buffer and in saline in comparison to non-pathogenic ones (p less than 0.01). The adherence of the pathogenic strains to the buccal cells was significantly greater only after incubation in saline (p less than 0.05 after 30 min and p less than 0.01 after 90 min). The above findings suggest that adherence may be of importance in fungal colonization on mucous membrane surface resulting in development of fungal infection.

Adhesiveness↗

PubMed1996

Microbial pathogenicity factors as parts of global regulatory networks. (A short review).

Pathogenic bacteria differ from non-pathogenic isolates by the expression of so-called virulence or pathogenicity factors, including adherence molecules, toxins, capsules and others. The majority of the genes encoding pathogenicity factors are not expressed constitutively, but rather undergo environmental regulation or random regulatory events. In enterobacteria, such virulence associated genes are often corregulated with determinants influencing metabolic properties. By analyzing the structure and regulation of genes which are essential for the urovirulence of pathogenic Escherichia coli, we were able to show that genes coding for alfa haemolysin, cytotoxic necrotizing factor I and P fimbriae are located on large instable DNA regions, termed "pathogenicity islands". These islands also comprise regulatory genes which are able to activate adherence specific genes that are not part of those islands. In addition, pathogenicity islands are associated with tRNA loci. One of these tRNA genes, which codes for a minor leucin tRNA and is therefore termed leuX, acts as a global regulator. It influences the expression of various genes of pathogenic E. coli, including adherence specific loci, enterobactin genes, flagella specific gene clusters and determinants involved in serum resistance.

Antigenic Variation↗

PubMed1998

Pathogen resistance as the origin of kin altruism.

It is suggested that pathogen and parasite avoidance act as a driving force for kin selection. Preferential association with relatives decreases the probability of infection with unfamiliar pathogens. Altruistic behavior towards kin will further decrease the danger of infection by increasing the representation of relatives in a group. Such a behavioral strategy could evolve if pathogen resistance were heritable. Highly polymorphic major histocompatibility (MHC) genes largely determine heritable resistance to particular pathogens. The degree of relatedness within a group correlates with the degree of similarity in MHCs. It has been shown that detection of MHC type by mice guides preferential kin association. Pathogen avoidance appears to be the simplest explanation for the existence of a direct link between detecting the heritable component of the immune system and kin altruism. Detection of MHC also serves kin avoidance in mating. Periodic introduction of new genes including MHCs through mating provides resistance to the unavoidable appearance of foreign virulent pathogens (Hamilton et al., 1990, Proc. Natl Acad. Sci. U.S.A. 87, 3566-3573). It is suggested that kin preference favoring homogeneity punctuated by introduction of new genes through mating provides an optimal strategy for pathogen avoidance. Aggression might also serve to decrease infection by isolating or eliminating individuals with unrelated MHCs.

Altruism↗