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Query: UMLS:C0348321 (Haemophilus)
 15,372 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In vitro, Haemophilus influenzae strains have two distinct patterns of susceptibility to trimethoprim-sulfamethoxazole (TMP/SMZ); strains with low minimum inhibitory concentration and high minimum bactericidal concentration (tolerant) and those with both low minimum inhibitory concentration and minimum bactericidal concentration (kill-sensitive). Tolerant H. influenzae strains were found to elaborate significantly more type b capsular polysaccharide, a linear polymer of ribosyl ribose phosphate (PRP), than kill-sensitive strains. Tolerant strains became susceptible to killing by TMP/SMZ when type b capsule was physically removed, but reacquired tolerance following growth and reversion to original (mucoid) phenotype. Susceptibility of wild (type a, b, c), isogenic (type b and untypable), and transformed (type b and d) strains indicated that elaboration of type b capsule was associated with TMP/SMZ tolerance. In a second series of studies, virulence of H. influenzae in the infant rat model was correlated with in vitro tolerance. Tolerant strains (13/13) caused systemic disease while none (0/7) of kill-sensitive strains were pathogenic. The efficacy of TMP/SMZ in the treatment of invasive infection was evaluated in rats with established bacteremia and meningitis. TMP/SMZ failed to eradicate H. influenzae b from the blood in 85% (17/20) or from the cerebrospinal fluid in 95% (19/20) of infected animals. Thus, in vitro tolerance correlated with therapeutic failure in vivo.
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PMID:Elaboration of type b capsule by Haemophilus influenzae as a determinant of pathogenicity and impaired killing by trimethoprim-sulfamethoxazole. 697 57

Brazilian purpuric fever (BPF) is a highly fatal pediatric disease that may follow an episode of purulent conjunctivitis caused by a virulent clone of Haemophilus influenzae biogroup aegyptius (Hae). Oral rifampin prophylaxis, by eliminating carriage of the BPF clone in children with conjunctivitis, may prevent onset of the systemic disease. A test to detect the BPF clone directly from eye swabs could identify those in need of prophylaxis. This is a preliminary report of a rapid dot immunoassay performed on a "flow-through" cartridge that was developed for use under field conditions. The test is based upon recognition of a unique epitope of the 25-kDa pilin protein on the surface of BPF clone cells by a monoclonal antibody. With 36 laboratory-maintained cultures of Hae (15 clone isolates and 21 others), sensitivity of the assay was 67% and specificity was 95%. When fimbrial-enriched (25-kDa+) phenotypes of five false-negative clone strains were prepared for use as test antigens, sensitivity rose to 100%. Evaluation of the immunoassay under field conditions is necessary to prove its efficacy.
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PMID:A rapid dot immunoassay for detecting the Brazilian purpuric fever clone of Haemophilus influenzae biogroup aegyptius with a "flow through" device. 777 1

Clonally related strains of Haemophilus influenzae biogroup aegyptius have recently been associated with Brazilian purpuric fever (BPF), a fulminant, systemic disease in children. Using an infant rat bacteremia model for BPF, we found that a rat blood-passaged BPF isolate of H. influenzae biogroup aegyptius was more virulent than the original strain was. When compared with the original strain, the animal-passaged variant was found to display an altered lipooligosaccharide (LOS) phenotype and to lack pili. To examine the role of LOS phenotype and pili in virulence, we isolated isogenic variants differing in LOS phenotype or expression of pili. The virulence of variants was compared by examining the results of blood cultures obtained 24 h after intraperitoneal inoculation with 10(5) CFU. Our results indicate that the LOS phenotype is a critical determinant of BPF clone virulence for infant rats. To a lesser extent, the absence of piliation and an undefined additional factor(s) contribute to virulence.
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PMID:Role of lipooligosaccharide in virulence of the Brazilian purpuric fever clone of Haemophilus influenzae biogroup aegyptius for infant rats. 809 94

Haemophilus influenzae is a common commensal organism of the human respiratory tract and is an important cause of localized and systemic disease. While isolates recovered from the respiratory tract are generally nonencapsulated (serologically nontypeable), isolates from systemic sites typically express a polysaccharide capsule. To explore the possibility that nontypeable strains evolved from encapsulated organisms, a series of serologically nontypeable isolates were examined for the presence of capsule gene sequences. Pharyngeal isolates (123) were collected from healthy 3-year-old Finnish children and examined by Southern hybridization with pUO38, a plasmid that contains one complete set of cap genes from an H. influenzae type b strain. Twenty-four isolates (20%) demonstrated homology with capsule-specific sequences. Of these 24, 18 in addition to 14 others had evidence of one or more copies of IS1016, an insertion element that has been associated with encapsulation in H. influenzae. These results support the hypothesis that nontypeable strains of H. influenzae arose from an encapsulated ancestor. Possibly the selective pressure driving the loss of encapsulation relates to the disadvantage associated with encapsulation during respiratory tract colonization.
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PMID:Evidence for capsule gene sequences among pharyngeal isolates of nontypeable Haemophilus influenzae. 810 67

Most human pathogens are acquired through mucosal portals of entry, and replicate in the mucosal tissues. Subsequently, the infecting agent may invade the blood stream and produce disease at distant systemic sites. However, a large number of pathogenic organisms are limited to development of disease only at the site of initial mucosal replication. Studies carried out with naturally acquired infections and mucosally delivered vaccines have provided strong evidence for the existence of a common mucosal immune system in the organized lymphoid follicles in respiratory and intestinal epithelium, and in the mucosa of genital tract, mammary glands, conjunctiva, upper airways, and the middle ear cavity. Mucosal application of live attenuated oral poliovaccine (OPV), rubella virus vaccine (RA 27/3), adenoviruses, influenza A virus, rotavirus, salmonella, and cholera vaccines have demonstrated consistent development of secretory IgA, serum antibody, and cellular immune responses. Mucosal immunization appears to result in preferential expression of several integrins and cell adhesion molecules associated with homing of lymphocytes to mucosal sites of immunization. Induction of mucosal immune responses often result in specific protection against reinfection challenge and against illness. Replicating agents introduced via the parenteral route also result in the development of mucosal responses and protection against systemic illness. Parenteral immunization with non-replicating agents often fails to induce specific mucosal responses. Such immunization, however, is quite effective in mounting high levels of serum antibody with development of protection against systemic illness. Parenteral vaccines, such as enhanced potency inactivated polio vaccine (eIPV), Haemophilus influenzae type B (HIB), hepatitis B virus (HBV), and other non-mucosal vaccines, have been highly effective in preventing systemic disease during subsequent exposure to natural infection. Recent evidence has shown that parenteral immunization can also be quite effective in inducing varying degrees of functional mucosal antibody responses as detected by ELISA and less frequently by neutralization. Systemic illnesses such as poliomyelitis and Haemophilus influenzae meningitis and community circulation of these agents has been eliminated or significantly limited in many parts of the world with the exclusive use of inactivated vaccines. Based on these observations, it is suggested that development of serum immunological responses are effective in the prevention of systemic disease regardless of the types of vaccines or route of their administration. However, induction of pathogen-specific antibody or cellular immunity at the mucosal sites is best elicited by mucosal application of the antigen.
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PMID:Mucosal responses to parenteral and mucosal vaccines. 985 24

We investigated the role of cytokines in differences in histopathologic changes in the lung between bronchopneumonia caused by non-encapsulated Haemophilus influenzae strain 770235f(0)b(0)and systemic disease caused by type b H. influenzae strain 770235f(0)b(+). Tumour necrosis factor-alpha (TNF-alpha), interleukin-(IL)-6 and IL-1 beta levels in bronchoalveolar lavage fluid (BALF) samples of mice infected with strain 770235f(0)b(0)were higher than in those infected with strain 770235f(0)b(+)until 24 h post-infection. Serum IL-6 rapidly increased in strain 770235f(0)b(0)infection after 72 h post-infection. Serum TNF-alpha level in strain 770235f(0)b(0)infection appeared earlier than in strain 770235f(0)b(+)infection. IL-1 beta production in strain 770235f(0)b(+)infection was later than in strain 770235f(0)b(0)infection. Moreover, a biphasic concentration pattern of TNF-alpha and IL-6 was noted in BALF of mice with strain 770235f(0)b(0)infection.
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PMID:Lipoolygosaccharide indirectly enhances inflammatory lesions in lungs as a primary infection site by non-encapsulated and type B Haemophilus influenzae through production of cytokines. 1155 87

Haemophilus parasuis is a commensal organism of the upper respiratory tract of conventional pigs, but under appropriate conditions can invade and cause severe systemic disease, characterized by fibrinous polyserositis, arthritis and meningitis. Factors involved in systemic invasion by H. parasuis remain largely unknown. However, major advances in our knowledge of H. parasuis include (1) development of a species-specific PCR test to detect H. parasuis in clinical samples, (2) study of molecular epidemiology within and between herds, by use of a repetitive element-based PCR, (3) the proposal of an alternative serotyping technique, (4) development and testing of a new in vivo model for pathogenesis and virulence studies, and (5) use of controlled exposure of young pigs to low doses of live, virulent H. parasuis strains to reduce nursery mortality in affected swine herds.
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PMID:Haemophilus parasuis: new trends on diagnosis, epidemiology and control. 1501 7

A total of 103 Danish Haemophilus parasuis field isolates was collected from diseased pigs in connection with routine diagnostics. The isolates were serotyped using indirect haemagglutination (IHA) and for 57 of the isolates the serotyping was also performed by immunodiffusion. Serovar 5 was the most prevalent (36%), followed by serovar 4 (13%) and serovar 13 (22%), whereas 15% of the strains were nontypeable by IHA. Serovars 1, 2, 6, 7, 9, 12, 14, and 15 were only represented by a small number of isolates. Most of the Danish isolates belong to serovars, which earlier have been shown to be virulent. The strains could be divided into two groups depending on whether they were isolated from cases with systemic disease (polyserositis, arthritis or meningitis) or if they only were found in the lower respiratory tract. The most marked differences were observed for serovar 4, which had a higher prevalence in respiratory disease compared to systemic infection, and for the nontypeable isolates, which were mainly found in cases of systemic infection.
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PMID:Serological characterization of Danish Haemophilus parasuis isolates. 1550 97

The ability of unencapsulated (nontypeable) Haemophilus influenzae (NTHi) to cause systemic disease in healthy children has been recognized only in the past decade. To determine the extent of similarity among invasive nontypeable isolates, we compared strain R2866 with 16 additional NTHi isolates from blood and spinal fluid, 17 nasopharyngeal or throat isolates from healthy children, and 19 isolates from middle ear aspirates. The strains were evaluated for the presence of several genetic loci that affect bacterial surface structures and for biochemical reactions that are known to differ among H. influenzae strains. Eight strains, including four blood isolates, shared several properties with R2866: they were biotype V (indole and ornithine decarboxylase positive, urease negative), contained sequence from the adhesin gene hia, and lacked a genetic island flanked by the infA and ksgA genes. Multilocus sequence typing showed that most biotype V isolates belonged to the same phylogenetic cluster as strain R2866. When present, the infA-ksgA island contains lipopolysaccharide biosynthetic genes, either lic2B and lic2C or homologs of the losA and losB genes described for Haemophilus ducreyi. The island was found in most nasopharyngeal and otitis isolates but was absent from 40% of invasive isolates. Overall, the 33 hmw-negative isolates were much more likely than hmw-containing isolates to have tryptophanase, ornithine decarboxylase, or lysine decarboxylase activity or to contain the hif genes. We conclude (i) that invasive isolates are genetically and phenotypically diverse and (ii) that certain genetic loci of NTHi are frequently found in association among NTHi strains.
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PMID:Characterization of genetic and phenotypic diversity of invasive nontypeable Haemophilus influenzae. 1611 4

Haemophilus somnus can be either a commensal of bovine mucosal surfaces or an opportunistic pathogen. Pathogenic strains of H. somnus are a significant cause of systemic disease in cattle. We report the genome sequence of H. somnus 129Pt, a nonpathogenic commensal preputial isolate, and the results of a genome-wide comparative analysis of H. somnus 129Pt, Haemophilus influenzae Rd, and Haemophilus ducreyi 35000HP. We found unique genes in H. somnus 129Pt involved in lipooligosaccharide biosynthesis, carbohydrate uptake and metabolism, cation transport, amino acid metabolism, ubiquinone and menaquinone biosynthesis, cell surface adhesion, biosynthesis of cofactors, energy metabolism, and electron transport. There were also many genes in common among the three organisms. Our comparative analyses of H. somnus 129Pt, H. influenzae Rd, and H. ducreyi 35000HP revealed similarities and differences in the numbers and compositions of genes involved in metabolism, host colonization, and persistence. These results lay a foundation for research on the host specificities and niche preferences of these organisms. Future comparisons between H. somnus 129Pt and virulent strains will aid in the development of protective strategies and vaccines to protect cattle against H. somnus disease.
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PMID:Complete genome sequence of Haemophilus somnus (Histophilus somni) strain 129Pt and comparison to Haemophilus ducreyi 35000HP and Haemophilus influenzae Rd. 1717 29


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