Susceptibility of Haemophilus aegyptius to trooleandomycin: lack of taxonomic value

Two hundred and nine strains of Haemophilus influenzae and Haemophilus aegyptius were screened for trooleandomycin susceptibility. Four strains were shown to be sensitive to the drug. Of these four, two were Haemophilus aegyptius (ATCC 11116, NCTC 8134), and the other two were Haemophilus influenzae biotype I (1-605) and IV (80-212. One strain of Haemophilus aegyptius (NCTC 8135) was resistant to trooleandomycin. Restriction enzyme assays and DNA homology were carried out to establish relationships between the strains. It is concluded that trooleandomycin susceptibility has no taxonomic value to differentiate between Haemophilus aegyptius and biotype III Haemophilus influenzae.     

Plasmid transformation in Haemophilus influenzae.

Purified 34-megadalton-plasmid deoxyribonucleic acid from antibiotic-resistant strains of Haemophilus influenzae transforms competent strains of H. influenzae more efficiently if the recipient strains contain certain other 30-megadalton plasmids.     

Chromosomally integrated conjugative plasmids are common in antibiotic-resistant Haemophilus influenzae.

Twenty-three highly antibiotic-resistant strains of Haemophilus influenzae and two of Haemophilus parainfluenzae without detectable large plasmids were examined for conjugative transfer of their resistance to H. influenzae strain Rd or to other strains. Very inefficient transfer was observed for 18 H. influenzae strains and 1 H. parainfluenzae strain. All H. influenzae transcipients carried a large plasmid, and they were in turn efficient donors of their resistances in standard conjugation crosses with isogenic recipients. This was not seen for the H. parainfluenzae transcipients. It is concluded that most of the original antibiotic-resistant cultures carried an integrated conjugative R plasmid which had been excised in a few cells in each population. It was these cells which transferred resistance in the primary crosses.     

Diagnostic difficulties in identification of Haemophilus influenzae colonising the nasopharynx of children

The frequency of capsulated or non-capsulated Haemophilus influenzae strains colonisation among children attending day-care centres or orphanages has been studied. Detection of capsulated or non-capsulated H. influenzae strains has been compared for agglutination test and PCR. Misdiagnosing of H. influenzae serotype with agglutination found in the study suggest that the frequency of Hib strains colonizing the nasopharynx might be lower that previously evaluated. Due to perspectives of the wider use of Hib Immunisation in the future, more efficient diagnosis scheme for identification/differentiation of capsulated and non-capsulated H. influenzae strain should be undertaken.     

Anomalous but helpful findings from the BBL Crystal ID kit with Haemophilus spp

Fourteen strains of Haemophilus (12 H. influenzae , 1 H. parainfluenzae and 1 H. aphrophilus ) were processed in BBL Crystal ID Enteric/Nonfermenter, API 20E and API 20NE kits, to determine whether the BBL kit misidentifies, as API kits may do, Haemophilus spp. as Pasteurella spp. The 13 H. influenzae and H. parainfluenzae strains produced uninterpretable colour reactions in the Crystal kit, thus signalling that an inappropriate species had been tested. On the other hand, the API kits (especially 20NE) often confidently 'identified' Haemophilus spp. as Pasteurella spp., giving no warning that this was a misidentification.     

The occurrence of denitrification in extremely halophilic bacteria

Abstract A total of 97 aerobic and facultatively anaerobic bacteria, and 3 Candida albicans , were tested for their ability to inhibit the growth of Haemophilus influenzae . Only strains of Pseudomonas aeruginosa showed any inhibitory effect and all 5 strains tested clearly inhibited the growth of all 10 strains of H. influenzae . The inhibition of H. influenzae . by Ps. aeruginosa may play a role in the establishment of chronic Ps. aeruginosa infections in the respiratory tracts of patients with bronchiectasis and cystic fibrosis (CF).     

Mouse models of infection for Neisseria meningitidis B,2b and Haemophilus influenzae type b diseases

A disseminated and fatal infection was established in C57BL mice, injected intraperitoneally with either Neisseria meningitidis B,2b or Haemophilus influenzae type b bacteria plus enhancement factors. The effects of mucin, hemoglobin, and iron dextran as enhancement of bacterial infectivity in mice were evaluated individually and in combination. A mixture of mucin and hemoglobin was most effective in enhancing the virulence of the pathogens. Inbred mouse lines were more susceptible than outbred ones. Relative virulence of a number of bacterial strains was also compared in one selected mouse line. Neisseria meningitidis B,2b and Haemophilus influenzae type b strains were more virulent than non-B,2b and nontypable strains. Finally, the course of bacteremia for the two infections in mice was followed by quantitative blood cultures. The animals succumbed to the generalized condition within 72 h. In the case of Neisseria meningitidis B,2b, 10 organisms with 4% mucin and 1.6% hemoglobin were sufficient to kill 50% of the animals. For Haemophilus influenzae type b, 300 bacteria with 5% mucin and 2% hemoglobin were necessary to obtain similar effects.     

Tetracyclin-stimulated expression of ampicillin resistance in Haemophilus influenzae.

Tetracycline at a low concentration stimulated the expression of ampicillin resistance in certain strains of Haemophilus influenzae.     

Binding of human hemoglobin by Haemophilus influenzae

Abstract Binding of biotinylated human hemoglobin to Haemophilus influenzae was detected when organisms were grown in heme-deplete, but not heme-replete, conditions. Hemoglobin binding was completely inhibited by a 100-fold excess of unlabelled human hemoglobin or human hemoglobin complexed with human haptoglobin. Binding was only partially inhibited by rat hemoglobin, bovine hemoglobin, human globin, and bovine globin, and not at all by heme, human serum albumin, bovine serum albumin, human transferrin, or myoglobin. Hemoglobin binding was saturable at 16–20 ng of hemoglobin per 10⁹ cfu. Binding of human hemoglobin was detected in serotypes a-f and serologically non-typable strains of H. influenzae , as well as Haemophilus haemolyticus but not Haemophilus parainfluenzae, Haemophilus aphrophilus, Haemophilus parahaemolyticus , or Escherichia coli .     

Intraspecific and intergeneric mobilization of non-conjugative resistance plasmids by a 24.5 megadalton conjugative plasmid of Neisseria gonorrhoeae

pLE2451, a 24.5 megadalton conjugative plasmid from Neisseria gonorrhoeae, was capable of efficiently mobilizing gonococcal beta-lactamase plasmids between gonococci and from gonococci to Haemophilus influenzae and restriction-deficient Escherichia coli. Donor strains of N. gonorrhoeae carrying pLE2451 were also found to be capable of mobilizing a variety of non-conjugative plasmids originally derived from enteric bacteria or Haemophilus species when such plasmids were resident in E. coli. Nevertheless, pLE2451 was not detected physically in E. coli or H. influenzae transconjugants. This suggests that the plasmid is unstable in these hosts but survives transiently to provide transfer functions for mobilization. The proficiency of pLE2451 in promoting intraspecific and intergeneric mobilization was not paralleled by pUB701, pRI234 and pFR16017, a series of conjugative plasmids derived originally from Haemophilus species. These plasmids were incapable of mobilizing even Haemophilus beta-lactamase plasmids, such as RSF0885, between Haemophilus species.     

A rapid purification method of restriction endonucleases from Haemophilus strains.

A simple and rapid method of purification of restriction endonucleases from different Haemophilus strains is presented. By this method highly purified and stable enzymes can be obtained. Separation of different restriction activities present in the same strain is possible. This method was so far successfully used with Haemophilus influenzae, Haemophilus parainfluenzae and Haemophilus aegyptius strains. The main advantages over previously published procedures reside in the simplication of certain purification steps (for instance the BioGel A 0.5 M filtration is replaced by a hydroxyapatite batch step), elimination of exonuclease activity by fractionation with (NH4) 2SO4, separation of different restriction activities by phosphocellulose chromatography, application of this method to various strains and high purification degree of enzymes.     

Serotyping of Noncapsular Haemophilus influenzae

A microtechnique is described for agglutination typing of Haemophilus influenzae. It also provides a further means for classification and study of noncapsular type-specific strains.     

Occurrence of the Fimbria Gene hifA in clinical isolates of nonencapsulated Haemophilus influenzae

The adherence of Haemophilus influenzae to epithelial cells plays a crucial role in infections. However, little is known about the occurrence of fimbriae. In this study, we examined the distribution of the fimbria gene (hifA) by PCR among 167 H. influenzae strains isolated from patients with respiratory infections. Almost all (163; 98%) of the isolates were nonencapsulated strains. The carriage rate of hifA by the nonencapsulated strains was 18.4%. Electron microscopy showed that fimbriae were abundantly present on the cell surface of hifA-positive strains tested. Only four (2.4%) isolates were encapsulated, all of which were type b and did not possess hifA. The present work suggests that fimbriae may play a considerable role as adhesins in nonencapsulated H. influenzae strains.     

Characterization of the genetic locus encoding Haemophilus influenzae type b surface fibrils.

Haemophilus influenzae is a common gram-negative pathogen that initiates infection by colonizing the upper respiratory tract epithelium. In previous work, we reported the isolation of a locus involved in expression of short, thin surface fibrils by H. influenzae type b and presented evidence that surface fibrils promote attachment to human epithelial cells. In the present study, we determined that the fibril locus is composed of one long open reading frame, designated hsf, which encodes a protein (Hsf) with a molecular mass of approximately 240 kDa. The derived amino acid sequence of the hsf product demonstrated 81% similarity and 72% identity to a recently identified nontypeable H. influenzae adhesin referred to as Hia. In experiments with a panel of eight cultured cell lines, the Hsf and Hia proteins were found to confer the same binding specificities, suggesting that hsf and hia are alleles of the same locus. Southern analysis and mutagenesis studies reinforced this conclusion. Further investigation revealed that an hsf homolog is ubiquitous among encapsulated H. influenzae strains and is present in a subset of nontypeable Haemophilus strains as well. We speculate that the hsf gene product plays an important role in the process of respiratory tract colonization by H. influenzae.     

The other mediator for adherence of Haemophilus influenzae organisms without involvement of fimbriae.

The number of the nontypeable Haemophilus influenzae (HiN) organisms that adhered to the primary mouse fetal lung cells was significantly more than type b Haemophilus influenzae (Hib) organisms. The average number of HiN organisms adherent to host cells was 2,291/100 host cells (range, 1,654-3,182), but that of Hib was markedly reduced to 147/100 host cells (range, 102-238). In this case, P value was less than 0.05 by using a paired Student t-test. The sonicated extract from HiN TMS11 organisms inhibited adherence of H. influenzae TMS11 organisms to monolayer at 76.3% and it inhibited adherence of Hib TMS24 organisms at 92.3%. This result indicates that a mediator existing on the surface of HiN organisms may be the same as that on type b organisms. The number of detected organisms in broncho and lung tissues 3 days after intranasal infection with HiN strains was significantly greater than that in infection with Hib strains. Therefore, in vitro adhesive capacity of H. influenzae organisms was correlative to infectivity by intranasal injection.     

Sensitivity of Haemophilus influenzae to Antibiotics

The use of many different antibiotics to treat chest infection has led us to test the sensitivity of 68 strains of Haemophilus influenzae to 15 different compounds. These included established compounds such as ampicillin and tetracycline and newer agents such as cephalosporins and clindamycin. The minimum inhibitory concentrations of the compounds for H. influenzae were then compared with blood levels attained after the usual dose regimens. There has been a significant increase in tetracycline resistance in the last few years, but all strains were sensitive to ampicillin, chloramphenicol, sulphamethoxazole, and trimethoprim, Several antibiotics were found to be microbiologically unsuitable for treating H. influenzae infections.     

Urogenital, maternal and neonatal isolates of Haemophilus influenzae: identification of unusually virulent serologically non-typable clone families and evidence for a new Haemophilus species

A collection of 117 strains of Haemophilus influenzae, including 112 non-typable isolates recovered predominantly in the USA and France from genital, obstetric and neonatal sources, was characterized by the electrophoretic mobilities of 10 metabolic enzymes. Eighty-six distinctive multilocus chromosomal genotypes (electrophoretic types, ETs) were distinguished on the basis of allele profiles at the enzyme loci. Isolates of five allied biotype IV ETs were highly divergent from all other strains and hybridization of chromosomal DNA revealed that they undoubtedly represent a previously unrecognized species of Haemophilus. Isolates representing these ETs were recovered predominantly from obstetric infections and serious neonatal diseases and apparently possess specific tropism for the genital tract. Strains of these five ETs were present in samples from both the USA and France, but only in the USA did they cause bacteraemia and meningitis, an occurrence which probably reflects differences in patient management between the two countries. Although strains assigned to H. influenzae (sensu stricto) were strongly polymorphic in multilocus enzyme genotype, 69% of isolates recovered from patients with meningitis and/or septicaemia were assigned to only two clone families, a result suggesting that some serologically nontypable strains of H. influenzae originating from the genital tract are unusually virulent.     

Susceptibility of gram-negative bacteria to the synergistic bactericidal action of serum and polymyxin B nonapeptide

Polymyxin B nonapeptide was able to sensitize Escherichia coli strains and strains of Salmonella typhimurium, Klebsiella spp., Enterobacter cloacae, Pseudomonas aeruginosa, and Haemophilus influenzae to the bactericidal action of fresh normal human serum. The degree of sensitization varied significantly within the strains. Strains of Proteus mirabilis, Neisseria gonorrhoeae, and N. meningitidis remained resistant.     

Serotypes and biotypes and antibiotic susceptibility of Haemophilus influenzae encountered in a clinical laboratory in Taiwan.

Forty-four serologically and biochemically typable Haemophilus influenzae isolates from clinical specimens in Taiwan were subjected to analysis in their relationship with source of isolation and age distribution. It was found that all isolates from blood and cerebrospinal fluid were serotype b, biotype I, and all were in children less than 4 years of age. Serotypes b and e, biotypes I and III were encountered to have the highest incidence of infection caused by H. influenzae in this area. All H. influenzae isolates were further tested for susceptibility to several selected antibiotics. All strains of this organism were susceptible to erythromycin and chloramphenicol. All but two strains were susceptible to tetracycline, whereas more strains were resistant to carbenicillin, gentamycin, keflin, and penicillin. Thirty-four percent strains were found to be resistant to ampicillin and all were beta-lactamase producer. No direct correlation between ampicillin resistance and serotypes or biotypes was recognized.