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Eight phenotypically homogeneous Moraxella-like strains were isolated from the nasal flora of healthy goats. Total genomic DNA-DNA hybridization, DNA base composition determination, and genetic transformation studies were performed to determine the relationships of these bacteria to the classical moraxellae. The eight new isolates exhibited very high levels of genetic affinity to Moraxella bovis, as shown by quantitative and qualitative genetic transformation data, and exhibited high DNA-DNA relative binding ratios to each other (63% or more) but lower levels of DNA homology with all of the other species investigated, including the closely related classical moraxellae. Our results, combined with the general morphologic and phenotypic profiles of these organisms, indicate that they should be classified with the classical moraxellae, and we propose the name Moraxella caprae for them. Strain 8897 (= CCUG 33296 [corrected] = NCTC 12877) is the type strain of M. caprae.
From 1953 to 1980 the Centers for Disease Control received 933 isolates of bacteria belonging to species of the genus Moraxella, Moraxella-like Moraxella urethralis, now renamed Oligella urethralis, unnamed groups M-5 and M-6, and Kingella kingae. Ordinarily sterile sites were the source of 233 isolates. Moraxella nonliquefaciens, the most common isolate (356 strains), was recovered from upper respiratory or ocular sites in 208 (58%) of the cases. Moraxella osloensis was next most common (199 strains) but was the most frequent blood isolate (44 cases). K. kingae appeared especially invasive, with 58 of 78 isolates from blood, bone, or joint. Of the K. kingae strains, 75% were recovered from children under 6 years, compared with 23% of the other strains from that age group (P less than .01). Of the 74 isolates of group M-5, 53 were from wounds caused by dog bites; no other organism in this series was recovered from such wounds. Sixteen of the 28 M. urethralis isolates were from urine. Cases occurred as single infections, with no evidence of clusters. Of patients with infection of ordinarily sterile sites, 9.3% died; only bacteremia, meningitis, and empyema caused fatalities. Most referring laboratories (98%) had not identified the organisms to species, and only 30% had identified them to correct genus. Susceptibility testing by broth dilution revealed low MICs of penicillin (mean, 0.3; 64% less than 1 micrograms/mL). Moraxella, M. urethralis, M-5, M-6, and Kingella are important but frequently misidentified pathogens for humans; penicillin appears to be the treatment of choice.
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Six Moraxella-like strains that formed a phenotypically homogeneous group were isolated from the nasal flora of healthy goats. Total genomic DNA-DNA hybridization, rRNA gene restriction pattern, DNA base composition, and genetic transformation studies were performed to determine the relationships of these bacteria to species belonging to the genus Moraxella and other fastidious gram-negative species. The new group of isolates was very homogeneous, as shown by rRNA gene restriction fragment length patterns (ribotyping), and these organisms displayed high relative binding ratios (RBRs) to each other in DNA-DNA hybridization experiments (RBRs, > or = 58%) but distinctly lower levels of DNA homology with all other species investigated. However, the RBRs obtained with species of the genus Moraxella were higher than the RBRs obtained with all other gram-negative strains examined. Although the new strains had most of the Moraxella bovis phenotypic characteristics except nitrate reduction, quantitative and qualitative genetic transformation data led to the conclusion that they belong to a distinct new cluster in the genus Moraxella. The results of this study, combined with the general morphological and phenotypic profiles of the new strains, are consistent with the creation of a new Moraxella species, for which the name Moraxella boevrei is proposed. Strain 88365 (= ATCG 700022 = CCUG 35435 = NCTC 12925 = CIP 104716) is the type strain of M. boevrei.
A polyphasic taxonomic study was performed to determine the relationships of 10 Moraxella-like strains isolated mainly from the human respiratory tract in Sweden. Two of the strains formed a separate subgroup on the basis of both their protein contents and their fatty acid contents. However, the overall protein and fatty acid profiles revealed that all 10 strains were highly related. Representative strains of the two subgroups exhibited high DNA binding values (98%) with each other and had an identical DNA base ratio (44 mol% G+C). DNA-rRNA hybridizations revealed that this taxon can be included in the genus Moraxella, which is only distantly related to phenotypically similar genera, such as the genera Neisseria and Kingella. The results of an extensive phenotypic analysis indicated that the general biochemical profile of the 10 strains conforms with the description of the genus Moraxella given in Bergey's Manual of Systematic Bacteriology. We therefore consider these organisms members of a new Moraxella species, for which the name Moraxella lincolnii is proposed. Furthermore, we also conclude that Moraxella osloensis belongs, genotypically as well as phenotypically, to the genus Moraxella.
The taxonomic position of a group of 16 Moraxella catarrhalis-like strains, isolated mainly from dogs, was examined by using morphological tests, biochemical tests, serology, ribotyping with oligonucleotide probes, polymerase chain reaction typing of the 16S rRNA gene and the 16S-23S rRNA gene spacer region, polyacrylamide gel electrophoresis of total proteins, fatty acid profiles, moles percent G+C, dot spot and in-solution DNA-DNA hybridizations, and DNA-rRNA hybridizations. It was found that these organisms constitute a distinct cluster within the genus Moraxella. Since they differ genotypically as well as phenotypically from previously described Moraxella species, a new species, Moraxella canis, is proposed to accommodate these isolates. The type strain is LMG 11194 (= N7 = CCUG 8415A).
Two closely related beta-lactamases, BRO-1 and BRO-2 (formerly called Ravasio and 1908), are found in Moraxella (Branhamella) catarrhalis. We screened strains of B. catarrhalis recovered in the United States since 1952 and identified the first beta-lactamase-positive isolate in August 1976. The prevalence of the enzymes among 394 clinical isolates from one Texas hospital has averaged 75% since testing began in 1983. Screening of isolates of Moraxella subgenus Moraxella revealed the BRO enzymes in two other human respiratory tract species, M. lacunata and M. nonliquefaciens, beginning in 1978. A different beta-lactamase with a pI of 6.4 predominated in other species of subgenus Moraxella. BRO-2 had a different isoelectric focusing pattern and was produced in lesser amounts than BRO-1, but the two enzymes were indistinguishable by substrate or inhibitor profile. BRO enzymes from B. catarrhalis, M. nonliquefaciens, and M. lacunata could be transferred by conjugation and, for B. catarrhalis, also by transformation to B. catarrhalis. Plasmid bands were demonstrated in 90% of M. nonliquefaciens and in one previously reported strain of B. catarrhalis, but no change in plasmid profiles was seen in beta-lactamase-positive recombinants, supporting previous studies that suggested the beta-lactamase genes are chromosomal.
The majority of clinical isolates of Moraxella catarrhalis produce beta-lactamase. The role of this enzyme in the phenomenon of indirect pathogenicity, in which a true pathogen such as Streptococcus pneumoniae is protected from the action of certain beta-lactam antibiotics, is well recognized. By using a simple continuous-culture biofilm system, it has been shown that the pneumococcus attains high titers in excess of 10(12) CFU/biofilm; furthermore, the penicillin-sensitive pneumococcus used remained susceptible to a range of beta-lactam antibiotics in these biofilms (R. K. Budhani and J. K. Struthers, J. Antimicrob. Chemother. 40:601-602, 1997). This system was used to characterize the antibiotic susceptibility of this isolate when grown with beta-lactamase-negative or -positive moraxellae. When grown with beta-lactamase-producing moraxellae in the presence of either benzylpenicillin or amoxicillin, the pneumococcus was protected in the range of the antibiotic concentrations to which it would be considered resistant. With amoxicillin-clavulanic acid the titers of the two organisms collapsed at the antibiotic concentration at which moraxellae became susceptible. The levels of beta-lactamase activity in cell-free supernatants of broth culture, in biofilm, and in biofilm effluent revealed distinct differences in this activity; levels in biofilm were significantly lower than those in broth culture supernatants. The system appears suitable for studying organisms under antibiotic stress and for investigating the interactions of bacteria under such conditions.
We determined phenotypic characteristics, cellular fatty acid composition, and isoprenoid quinone content of representative strains of CDC groups EO-2, M-5, and M-6, Moraxella (Moraxella) species, Oligella urethralis, Acinetobacter species, and Psychrobacter immobilis. All organisms contained ubiquinone with eight isoprene units as the major isoprenolog, but distinct differences were observed in fatty acid composition. Twenty-eight of the original collection of CDC group EO-2 strains were further identified as P. immobilis, EO-2, or EO-3 by distinctive cellular fatty acid profiles, cellular morphology, and pigment production. The cellular fatty acid compositions of M-5 and M-6 were similar but were clearly different from those of other organisms. The genus Acinetobacter was differentiated from other organisms in the study by small amounts of 2-hydroxydodecanoic acid (2-OH-12:0), and P. immobilis was differentiated by small amounts of decanoic acid (10:0) and a branched-chain 17-carbon acid (i-17:0). All Moraxella species were distinguished by small amounts of decanoic acid (10:0) and the absence of i-17:0. M. bovis, M. nonliquefaciens, and some strains of M. lacunata formed a single fatty acid group, while M. osloensis, M. phenylpyruvica, M. atlantae, and other strains of M. lacunata (M. lacunata II) had species-specific fatty acid profiles. O. urethralis differed from Moraxella species by the presence of large amounts (49%) of cis-vaccenic acid (18:1 omega 7c), small amounts (1%) of 3-hydroxyhexadecanoate (3-OH-16:0), and the absence of 10:0 and 3-hydroxydodecanoate (3-OH-12:0). The combined use of chemical data and a small number of conventional tests permitted rapid identification and differentiation of these organisms from each other and from related organisms.
In Moraxella (Branhamella) catarrhalis and Moraxella nonliquefaciens strains isolated from clinical specimens in the south of Sweden two variants of beta-lactamase were distinguished by isoelectric focusing (IEF). The BRO-1 (Ravasio type) enzyme was the most common in Branhamella catarrhalis, constituting about 90% of the beta-lactamase found in this species, while the BRO-2 enzyme (1908 type) was as common as BRO-1 in Moraxella nonliquefaciens. The determinants mediating the production of BRO-1 and BRO-2 were both transferable by conjugation. Cell-bound beta-lactamase from reference strains producing BRO-1 and BRO-2 could be solubilized by papain digestion. The isoelectric point of the solubilized enzymes differed distinctly between BRO-1 (pI 6.5) and BRO-2 (pI 6.9). The molecular species of BRO-1 and BRO-2 released by papain digestion were purified by affinity chromatography with phenylboronic acid agarose gel. They had identical molecular weights of approximately 28,000. Their kinetic constants were indistinguishable for a number of substrates and beta-lactamase inhibitors.
By employing the non-ionic detergent Triton X-100, a membrane-bound beta-lactamase was extracted from strains of Moraxella (Branhamella) catarrhalis and Moraxella nonliquefaciens that produce BRO-1 and BRO-2 beta-lactamases. Unlike BRO-1 and BRO-2, which exhibit multiple major bands on isoelectric focusing (IEF), the membrane-bound enzyme focused as a single IEF band at a pI of 6.20, which was not present with either of the other two enzymes. The membrane-bound beta-lactamase could be extracted from all strains producing BRO-1 and BRO-2, including recombinant strains constructed by transformation or conjugation. The enzyme was also recovered from Escherichia coli strain HB101 carrying vector plasmid pLQ521 into which the BRO-1 beta-lactamase gene from M. catarrhalis had been cloned. All three beta-lactamases were indistinguishable by inhibitor profiles with clavulanic acid, BRL 42715, sulbactam and tazobactam. These data suggested that all three beta-lactamases were the product of a single gene in Moraxella spp., and that the membrane-bound beta-lactamase serves as a precursor of both BRO-1 and BRO-2. Species differences in cellular processing of the membrane-bound enzyme could explain the minor differences in IEF patterns that occurred with BRO-1 and BRO-2 beta-lactamases when present in different species.
Moraxella lacunata and Moraxella bovis use type 4 pili to adhere to epithelial tissues of the cornea and conjunctiva. Primer extension analyses were used to map the transcriptional start sites for the genes encoding the major pilin subunits (tfpQ/I) and the DNA invertase (piv), which determines pilin type expression. tfpQ/I transcription starts at a sigma54-dependent promoter (tfpQ/Ip2) and, under certain growth conditions, this transcription is accompanied by weaker upstream transcription that starts at a potential sigma70-dependent promoter (tfpQ/Ip1). piv is expressed in both M. lacunata and M. bovis from a putative sigma70-dependent promoter (pivp) under all conditions assayed. Sigma54-dependent promoters require activators in order to initiate transcription; therefore, it is likely that tfpQ/Ip2 is also regulated by an activator in Moraxella. Primer extension assays with RNA isolated from Escherichia coli containing the subcloned pilin inversion region from M. lacunata showed that pivp is used for the expression of piv; however, tfpQ/Ip2 is not used for the transcription of tfpQ/I. Transcription from tfpQ/Ip2 was activated in E. coli when the sensor (PilS) and response regulator (PilR) proteins of type 4 pilin transcription in Pseudomonas aeruginosa were expressed from a plasmid. These results suggest that the expression of the type 4 pilin in M. lacunata and M. bovis is regulated not only by a site-specific DNA inversion system but also by a regulatory system which is functionally analogous to the PilS-PilR two-component system of P. aeruginosa.
Moraxella subgenus Moraxella sp. was isolated in pure culture from the sputum of a 43-year-old male with pneumonia and congestive heart failure due to idiopathic dilated cardiomyopathy. In this case, we concluded that the patient's bacterial pneumonia was caused by M. (M.) sp. based on a Gram stain of the sputum smear and bacterial findings, increased WBC count, and elevated CRP. A chest X-ray revealed right middle, and left upper and middle lobe infiltrates. This Moraxella strain produced a BRO-type beta-lactamase, a carbenicillinase-type enzyme.
A number of strains of oxidase-positive moraxellas and of neisserias related to Neisseria catarrhalis were characterized with respect to a number of nutritional and physiological properties and could be assigned to several species or species groups on the basis of their phenotypic traits. This grouping was consistent with that established by Bövre on the basis of transformation frequencies for streptomycin resistance. It is proposed to reserve the generic name Moraxella for the oxidase-positive rodshaped organisms, and a redescription of the genus is offered. Following the recent taxonomic proposals of Bövre and Henriksen, the specific name Moraxella osloensis is applied to the nutritionally unexacting strains that accumulate poly-beta-hydroxybutyrate as carbon reserve. The nutritionally exacting strains are assigned to three distinct groups which can be regarded as separate species or as varieties of M. lacunata. The epithets applicable to these groups appear to be lacunata, nonliquefaciens, and bovis. The "false neisserias" could be assigned to at least three subgroups, one of which constitutes the clearly defined entity, N. catarrhalis, which could be distinguished from N. caviae and N. ovis.
The peptidoglycans of Moraxella glucidolytica and Moraxella lwoffi grown on aliphatic hydrocarbons were isolated. They contained muramic acid, glucosamine, alanine, D-glutamic acid and mesodiaminoimelic acid in a molar ratio of about 0.5:0.5:1.6:1.0:1.0 (M. glucidolytica) and 0.8:0.7:1.3:1.0:1.0 (M. lwoffi). The peptidoglycans were lysozyme-resistant. However, when treated with formanide, they could be partially degraded by lysozyme. The fragments were purified and their structure determined. In both strains, the peptide subunits consisted mainly of tripeptides (L-Ala-D-Glu-meso-DAP) and tetrapeptides (L-Ala-D-glu-meso-DAP-D-Ala), most of them being directly cross-linked. It is concluded that in both strains the primary structures of the peptidoglycans are closely related.
The bacterium Moraxella lacunata is a causative agent of human conjunctivitis and keratitis. We have previously reported construction of plasmid pMxL1, which includes a 5.9-kb fragment on which the pilin gene inversion region of M. lacunata resides. The inversion region of pMxL1 was shown to invert when pMxL1 was in an Escherichia coli host cell. In this report, we present Western immunoblot analysis using Moraxella bovis Epp63 anti-I and anti-Q pilin sera which demonstrate that pMxL1 makes pilin only when in orientation 1. The sequence of the pMxL1 plasmid containing the invertible region contains a perfect tandem repeat of 19 bp in the orientation 1 nonexpressed pilin gene at the middle of the recombination junction site. This 19-bp insert causes a frameshift and disrupts the pilin gene. The predicted amino acid sequence of this nonfunctional pilin gene (with the 19-bp repeat subtracted) bears closest resemblance to M. bovis Epp63 Q pilin sequence, although the other (functional) M. lacunata pilin encoded by pMxL1 shows slightly higher homology to Q pilin. Comparison of the pMxL1 sequence with that of the M. bovis Epp63 sequence shows two other particularly interesting differences. One is a 15-bp sequence addition found in pMxL1 at the 60-bp region previously reported as a possible M. bovis recombinational enhancer. The second is an AT deletion in pMxL1 compared with Epp63 within an open reading frame (tfpB) which results in the pMxL1 tfpB open reading frame being one-third shorter than in Epp63. The DNA sequences in these three altered regions from the M. lacunata strain from which pMxL1 was derived were amplified by polymerase chain reaction and sequenced. The parent strain was found to contain the differences seen in pMxL1. Comparison of the M.bovis and M. lacunata pilin gene amino acid sequences is also presented.
By means of a lincomycin containing selective medium, gram-negative, oxidase-positive, non-motile, non-saccharolytic, penicillin-sensitive rods have been isolated from 24 of 165 healthy adults (13,9%). Three strains were lost, 7 strains were Moraxella osloensis (4,2%), 12 strains were Neisseria elongata (7,3%) and 2 strains were considered to be a subspecies of N. elongata (1.2%). By agglutination and immunodiffusion could be demonstrated that N. elongata is a serologically heterogenous species. The nasopharynx seems to represent the natural habitat of M. osloensis and N. elongata.