Transmission electron microscopy studies of Moraxella (Branhamella) catarrhalis

A trypsin-sensitive 200-kDa protein has been reported to be exclusively associated with haemagglutinating isolates of Moraxella (Branhamella) catarrhalis. Transmission electron microscopy studies revealed that haemagglutination by M. catarrhalis to both human and rabbit erythrocytes was mediated by a trypsin-sensitive outer fibrillar coat. This fibrillar layer was absent on non-haemagglutinating isolates examined. Immuno-electron microscopy, using a polyclonal antiserum containing antibodies to the 200-kDa protein as a probe, showed that the 200-kDa protein is present on the outer fibrillar layer of the bacterium. These findings suggest that the haemagglutinin of M. catarrhalis is a 200-kDa protein present on the outer fibrillar coat.     

Transformation of Acinetobacter calco-aceticus (Bacterium anitratum)

A highly efficient transformation system has been demonstrated in a strain of Acinetobacter calco-aceticus (Bacterium anitratrum). During mixed growth of various stable, unencapsulated, mutant strains, deoxyribonucleic acid (DNA) is liberated and fully encapuslated transformants can be isolated. Purified DNA preparations have been used to transform suitable recipient mutant strains for ability to synthesize capsules, ability to dispense with a growth factor requirement, and resistance to streptomycin. When the wild-type strain is deprived of its capsule, either by mechanical stripping or by mutation, the unencapsulated cells tend to form large clumped masses. A nonclumping mutant of an unencapsulated strain has been isolated. When ability to synthesize capsules is transformed into this nonclumping strain, the resultant cells no longer form chains, unlike the wild-type encapsulated strain. It appears likely that the occurrence of transformation during growth of mixed cultures, with glucose or gluconate as the carbon source, may be the result of osmotic rupture resulting from the inability of unencapsulated strains to oxidize triose phosphates as fast as they are formed. The finding of transformation in Acinetobacter may provide an additional useful organism for the study of this mode of genetic transfer since this strain grows well in a simple mineral medium containing a single oxidizable source of carbon. Furthermore, no special supplementary factors seem to be required for transformation to take place.     

Complement resistance is a virulence factor of Branhamella (Moraxella) catarrhalis

Abstract The purpose of this study was to investigate complement resistance in Branhamella (Moraxella) catarrhalis isolated from healthy schoolchildren or sputum-producing adult patients. Two techniques were used: a serum bactericidal assay as the gold standard and an easier ‘culture and spot’ test. Children (age 4–13; n = 303) and patients ( n = 1047) showed high colonization/infection rates with B. catarrhalis (31% and 19%, respectively). Complement resistance or intermediate sensitivity occurred frequently in patient isolates (62% and 27%, respectively) and less often in children (33% and 8.5%, respectively; P ⪡ 0.0001). In young children (age 4–5 years), the proportion of complement-resistant strains was around 50%. Complement resistance in B. catarrhalis is associated with illness and may hence be considered a virulence factor.     

Tissue culture adherence and haemagglutination characteristics of Moraxella (Branhamella) catarrhalis

The haemagglutination and tissue culture adherence properties of 20 isolates of Moraxella catarrhalis obtained from the sputum of elderly patients with lower respiratory tract infections were compared with those of 20 isolates of M. catarrhalis obtained from the nasopharynx of elderly persons colonised by the organism. Eighty percent of isolates from the infected group as opposed to 5% of isolates from the colonised group haemagglutinated human erythrocytes (P < 0.001), indicating that the haemagglutinin might be a marker of pathogenicity for M. catarrhalis. There was a significant difference in the adherence to HEp-2 cells of isolates from the infected group in comparison to isolates from the colonised group (P = 0.03). Haemagglutination and tissue culture adherence properties were unrelated, indicating that separate adhesin systems are involved. The adherence of M. catarrhalis to HEp-2 cells was unaffected following pronase and trypsin treatment, however, sodium periodate pre-treatment of the bacteria significantly reduced the tissue culture adherence index, indicating that the adhesin by which the bacteria bind to HEp-2 cells may have a carbohydrate moiety. Transmission electron microscopy studies revealed that adherence of M. catarrhalis to HEp-2 cells was mediated by trypsin-resistant 'tack-/spicule-like' structures protruding from the surface of the bacteria.     

Morphological and Biochemical Differentiation of Achromobacter and Moraxella (Debord's Tribe Mimeae)

To determine the most useful laboratory tests for the differentiation of Achromobacter anitratus, Achromobacter lwoffii, and Moraxella duplex (DeBord''s tribe Mimeae), 157 strains of these bacteria, isolated from clinical specimens, were examined for their morphological and biochemical characteristics. There were several differences between these nonfermentative, gram-negative diplococci: Moraxella was nonglucolytic in either infusion base or synthetic base, oxidase-positive, and sensitive to penicillin, whereas Achromobacter produced variable carbohydrate activity, and was oxidase-negative and resistant to penicillin. A. anitratus was distinguished from A. lwoffii in that the former utilized infusion media containing either glucose or 10% lactose, whereas the latter did not. Both species utilized the same carbohydrates in a chemically defined medium, although the latter acted more sluggishly.     

Morphological and Biochemical Differentiation of Achromobacter and Moraxella (Debord''s Tribe Mimeae)

To determine the most useful laboratory tests for the differentiation of Achromobacter anitratus, Achromobacter lwoffii, and Moraxella duplex (DeBord's tribe Mimeae), 157 strains of these bacteria, isolated from clinical specimens, were examined for their morphological and biochemical characteristics. There were several differences between these nonfermentative, gram-negative diplococci: Moraxella was nonglucolytic in either infusion base or synthetic base, oxidase-positive, and sensitive to penicillin, whereas Achromobacter produced variable carbohydrate activity, and was oxidase-negative and resistant to penicillin. A. anitratus was distinguished from A. lwoffii in that the former utilized infusion media containing either glucose or 10% lactose, whereas the latter did not. Both species utilized the same carbohydrates in a chemically defined medium, although the latter acted more sluggishly.     

Morphogenetic expression of Moraxella bovis fimbriae (pili) in Pseudomonas aeruginosa.

Type 4 fimbriae (pili) are found in a wide variety of gram-negative bacteria and are composed of small structural subunits which share significant sequence homology among different species, especially at their amino-terminal ends. Previous studies demonstrating morphogenetic expression of Bacteroides nodosus fimbriae from cloned subunit genes in Pseudomonas aeruginosa suggested that there is a common mechanism for type 4 fimbriae assembly and that the structural subunits are interchangeable (J. S. Mattick et al., J. Bacteriol. 169:33-41, 1987). Here we have examined the expression of Moraxella bovis fimbrial subunits in P. aeruginosa. M. bovis subunits were assembled into extracellular fimbriae in this host, in some cases as a homopolymer but in others as a mosaic with the indigenous subunit, indicating structural equivalence. This result contrasts with other studies in which recombinant P. aeruginosa expressing different subunits produced fimbriae composed almost exclusively of one subunit or the other (T. C. Elleman and J. E. Peterson, Mol. Microbiol. 1:377-380, 1987). Both observations can be explained by reversibility of subunit-subunit interactions at the site of assembly, with the forward equilibrium favoring chain extension between compatible subunits.     

Herellea (Acinetobacter) and Pseudomonas ovalis (P. putida) from Frozen Foods

Seventeen strains of Herellea vaginicola (Acinetobacter antitratus) and 8 of Pseudomonas ovalis (P. putida), isolated from 23 (6.3%) of 364 samples of frozen, foil-pack foods, were identified and characterized morphologically and biochemically. Herellea was isolated from 17 foods (4.7%), P. ovalis from 6 (1.6%). No Mima were found. The food samples included precooked frozen meats, precooked and uncooked frozen vegetables, and uncooked frozen desserts. The bacteria were detected in the food with a procedure used generally for the detection of salmonellae. The pseudomonad simulated the characteristics of Herellea on Sellers differential agar, except for the fact that it fluoresced. From consideration of the habitat and pathogenicity of Herellea and Mima, it is concluded that, although the presence of these bacteria may not be desirable, their significance in food remains unanswered.     

Restriction Fragment Length Polymorphism (RFLP) of Genomic DNA of Moraxella (Branhamella) catarrhalis Isolates in a Hospital

Epidemiological typing, based on restriction fragment length polymorphism (RFLP) by pulsed-field gel electrophoresis (PFGE), was attempted for the 38 clinical isolates of Moraxella catarrhalis obtained at Shinshu University Hospital during the years 1987 and 1993. Digestion with SmaI or NotI generated well separable, 12 to 5 genomic DNA fragments ranging from 1,000 kb to 30 kb and the strains could be classified into 14 or 13 types, respectively. The electrophoretic profile differed with the strain in most of them and was hence useful to distinguish the each strain. Investigation for their RFLP have, however, suggested that majority of them, including the type strain ATCC25238, may have derived from a common ancestor.     

Progress toward the development of a vaccine to prevent Moraxella (Branhamella) catarrhalis infections

Moraxella catarrhalis is a major cause of otitis media and respiratory disease. Vaccine development is at the antigen identification stage. This review examines the more promising antigens, including the 200K protein, the hemagglutinins, the lactoferrin-binding proteins, the UspA proteins, the CopB protein, the transferrin-binding proteins, the CD protein, the E protein and lipooligosaccharide conjugates. Clinical testing of some of these antigens should begin soon.