These are shaped bacteria or coccobacilli (Moraxella) or cocci (Branhamella). Bacilli are very short, rounded, sometimes coccoid. They are usually in pairs or short chains, often pleomorphic, they show variations in size, length and are frequently under filamentous form in cultures. Cocci occur singly or in pairs and their morphology is identical to that of Neisseria.
Moraxella, motionless on direct examination fresh (no flagella), however, are capable of sliding or moving jerkily when in contact with a suitable surface (oil chamber Piéchaud and semi middle -Solid: Barker and Maxted). This mobility is related to the presence of pili.
They are Gram (-) but they fade easily. They may be encapsulated.
They are strict aerobic, some species breathe nitrate under anaerobic conditions. They have a cytochrome C oxidase and catalase in general.
They do not produce pigment, does not produce acid from carbohydrates and are sensitive to penicillin.
These are chemo-organotrophic bacteria with complex nutritional requirements and growth factors which are unknown in general.
The optimum growth temperature is between 33 and 35 ° C. These are the usual saprophytic mucous of humans and warm-blooded animals. Pathogenicity is generally limited, except for land debility they behave as opportunistic pathogens.
MORAXELLA:
HISTORY:
Morax (1896) and Axenfeld (1897) have individualized conjunctivitis due to sérophile diplobacille in the ill-defined group catarrhal conjunctivitis. They grew the bacterium and showed its pathogenicity. Lwolff A. (1939) created the genus Moraxella to separate iSHaemophilus.
I – CLASSIFICATION OF SPECIES – NAMES:
The grouping of Moraxella kind in two subgenresMoraxella and Branhamella was done on the basis of genetic studies. The former name of Moraxella oxidase (-) corresponds to the currently genus Acinetobacter.
In the subgenus Moraxella, three species are closely related genomic perspective M. lacunata, M. bovis, M. liquefaciens not.
Mr. osloensis Mr. phenyipyruvica Mr. Atlantae have more- genetic differences between them and different from otherMoraxella. M.urethralis departs many of these species and has been linked to gender Oligella, a new genus in the family Neisseriaceae.
It is proposed to collect Branhamella and Moraxella into a new family, Branhamaceae.
II – GENERAL CHARACTERISTICS:
On agar colonies are iridescent. The broth culture presents a homogeneous disorder with a veil on the surface where we find the same short forms on agar.
In isolation, the best culture medium comprises blood agar that can meet the complex nutritional requirements ofMoraxella. Besides Mr. lacunata, other species may be grown on nutrient agar containing yeast extract.
The sérophilie Mr. lacunata reflects a need in oleic acid. It may be reproduced in peptone water where growth is proportional to the concentration of Tween 80 (ester ac. Oleic).
A simple mineral medium containing an ammonium salt as nitrogen source and acetate as carbon source is sufficient to allow the growth of M. osloensis and 0. urethralis useful character for identification. However this type of environment does not allow their isolation.
III – MORAXELLA LACUNATA:
A – Body type:
In pus conjunctival: large rods rights, stocky with rounded ends, grouped mainly diplobacilli sometimes singly or in short chains in the middle of polymorphonuclear cells and epithelial cells.
Culture more polymorphic diplobacilli, large diplococci. Corpuscles metachromatic presence.
B – Cropping characters and identification:
– Sérophile: never grows on mainstream
– Isolation medium: blood agar, chocolate agar
– Serum agar: 24 am to 35 to 37 ° C, with small colonies often less than 1 mm, greyish, semi-transparent, magnifying later with a protruding center and a thinner periphery.
– Coagulated serum: after 24 h small cups liquefaction features (“gaps”) that increase thereafter. The serum is gradually liquefied.
– Gelatin + serum at 37 ° C: liquefaction
– Milk + serum (aerobic) culture, sometimes clotting.
C – pathogenic natural power:
It is the agent of subacute conjunctivitis diplobacillaire described by Morax.
Infectious, non-epidemic, not seasonal, rare, benign, often becoming the bilateral or secondarily, it evolves happy chronic.
It is characterized by an early joining of the eyelids, a slight mucopurulent secretion, redness usually limited to the lid margin and the inner corner of the eye (wattle), rarely complicated. Keratitis can be observed (severe ulcer with hypopyon serpiginous). It is possible bacterial complication of trachoma. It is rapidly cured by eye drops with zinc sulfate or antibiotics.
The extreme sensitivity of this organism to antiseptics and antibiotics that Mr. lacunata is only rarely isolated.
The current classification brings Mr. lacunata and M. liquefaciens (Mr. duplex var. liquefaciens) that were previously distinguished three criteria alone (cultivation easier and faster and sérophilie not mandatory) and pathogenicity more pronounced for the latter.
IV – MORAXELLA BOVIS (formerly duplex M. bovis var..):
This species was described by Hauderoy et al. in 1937 and in 1979 by Bovre.
A – bacteriological characters:
– Proteolytic: liquefied gelatin and coagulated serum
– Milk: coagulated peptonized
– Hemolytic
– Do not reduce nitrate
– No urease
– The presence of serum promotes culture.
B – Pathogenicity:
It is the agent of infectious keratoconjunctivitis of widespread cattle worldwide. A species very similar called M. equiwas isolated from the horses.
V – NON MORAXELLA liquefaciens (Mr. duplex non liquefaciens var.):
This species was described in 1916 by Scarlett then Bovre in 1979.
The colonies on blood agar were 2-3 mm after 48 hours. Some are very mucous membranes and non-haemolytic, the curved and flowing colonies may suggest Klebsiella.
A – bacteriological characters:
– Gelatin and DWMC are not liquefied
– Nitrates reduced to nitrites
– Urease present in a few strains.
B – Habitat:
In the human respiratory tract, it is customary in the nasal cavity, which is probably its main natural habitat, it is present in the throat and spitting.
C – Pathogenicity:
It is still uncertain. It could be an agent of secondary superinfection and some cases of purulent bronchitis. In isolated cases of meningitis, septicemia, formal evidence for its pathogenic role are not always made.
VI – MORAXELLA phenylpyruvica:
This species was described by Henriksen and Bovre in 1967.
The colonies on blood agar are quite small: 0.5 to 1 mm after 24 hours.
Growth is slow, difficult, the presence of serum improves.
The species name comes from the fact that the acid is phényipyruvique the deamination product of phenylalanine and tryptophan.
A – bacteriological characters:
– Usually non-hemolytic, but one can note a greening of the agar around the colonies.
– Nitrates usually reduced to nitrite
– Gelatin and serum coagulates non liquified
– Usually presents Urease
– Very sensitive to penicillin-resistant strains have been described that have a beta-lactamase.
B – Habitat:
It is not well known. Strains are isolated from the urogenital tract, urine, blood, cerebrospinal fluid, pus, various injuries. Brain abscess was described.
C – Pathogenicity:
It is likely to be small and poorly known at present.
VII – MORAXELLA OSLOENSIS:
This species was described by Henriksen and Bovre in 1967 and isolated in Oslo for the first time. We can highlight inclusions poly-beta-hydroxybutyrate (PHB) cultivating the seeds on a suitable medium containing a nitrogen source in limiting amount.
This germ is often encapsulated, colonies are smooth, often opaque. The growth is quite easy. It has no special requirements and can be grown on a simple mineral medium with acetate as a carbon source.
A – bacteriological characters:
– Non hemolytic
– Coagulated serum and not liquefied gelatin
– Nitrate reduction by half of the stem
– Rarely found Urease
– No deamination of phenylalanine
– Citrate rarely used
Less sensitive to penicillin than other species, some strains are resistant and have a beta-lactamase.
B – Habitat:
It is not well known. This species can be isolated from the urogenital tract, blood, CSF, upper respiratory tract.
C – Pathogenicity:
It is probably low. Some strains were isolated in cases of severe infections.
VIII – MORAXELLA Atlantae:
This species was described by Bovre et al. in 1976. The colonies are small sometimes become encrusted in the agar. This species is rarely isolated from blood, CSF, spleen. Its habitat and its pathogenicity are not defined.
IX – OLIGELLA (Moraxella urethralis):
Based on genetic studies M. urethralis was attached to the new kind Oligella where there are two species: 0.urethralis and 0. ureolytica.
A – bacteriological characters:
– Nitrate reduction Absence
– Reduction of nitrite
– Can be grown upon mineral medium with acetate
– Presence of inclusions of poly-beta-hydroxybutyrate
– Very sensitive to penicillin
B – Habitat:
This species is isolated from the genitourinary tract, urine and genital tract of women.
Pathogenicity is uncertain, it may be isolated in immunocompromised subjects.
Branhamella:
Three other species of Branhamella have recently been described. They are isolated in animals: B. caviae (dog), B.ovis (sheep), B. cuniculi (rabbit).
Although having common characteristics with Neisseria:cocci Gram (-) oxidase (+), catalase (+), the Branhamellahave no genetic relationship to this genre.
The opportunity of their attachment to the Moraxellasubgenus Branhamella is being discussed.
I – BACTERIOLOGICAL DIAGNOSIS:
The diagnosis of this species will be on the following characters:
– No acidification of carbohydrates
– Absence of pigment, and synthetic polysaccharides
– Growth in usual media
– Hydrolysis of tributyrin
– Production of lipase and DNase
– Reduction of nitrates and nitrites
– No hemolysis or greening of blood agar.
A small percentage of strains resistant colimycin and grows on the middle
VCF. Resistance of vancomycin permits the fabrication of selective media.
II – PATHOGENICITY:
n is now better known. The role of B. catarrhalis was demonstrated in:
– Broncho-pulmonary infections: in older people with respiratory failure (silicosis, emphysema) or left heart; in premature infants, immunocompromised patients …
– Children’s ENT infections (otitis media, sinusitis, nasopharyngitis)
– Septicemia and meningitis (exceptional)
– Lens and venereal infections (rare).
These infections are common in hospitals.
The concomitant presence of B. catarrhalis producer of B-lactamase and Streptococcus pneumoniae or Haemophilus influenzae susceptible to penicillin in the airways has developed the concept of indirect pathogenicity:B. catarrhalis protect other respiratory pathogens antibiotic action for the extension of the lean infection treatment sufficient a priori by ampicillin or amoxicillin. In this case a treatment with an oral cephalosporin is justified.
However, it should be noted that B. catarrhalis is often the only pathogen isolated during infectious episodes. For now, it has not been demonstrated virulence factors in this bacterium.
B. catarrhalis is often isolated from the child’s oropharynx but is uncommon in adults.
III – ANTIBIOTIC SENSITIVITY:
B. catarrhalis is generally sensitive to the antibiotics. But currently more than half of the strains has a B-lactamase hydrolyze penicillins.
This enzyme is constitutive and the gene on chromosome. Inactive on cloxacillin and cephalosporins, it is inhibited by clavulanic acid.
B. catarrhalis is sensitive to macrolides and tetracyclines. It is resistant to trimethoprim.