|Moraxella lacunata colonies on Sheep Blood Agar
Phylum Proteobacteria, Class Gammaproteobacteria, Order Pseudomonadales, Family Moraxellaceae, Genus Moraxella, Moraxella
lacunata (Eyre 1900) Lwoff 1939. Type species of the genus. The two subspecies: M. lacunata subsp. lacunata and M. lacunata
subsp. liquefaciens are not validly published.
Synonyms: Diplobacille de la conjonctivite subaiguë Morax 1896, Bacillus lacunatus Eyre 1900, Diplobacillus moraxenfeld McNab
Gram-negative, medium thick to plump rods, 0.8-1.2 μm in diameter, coccoid to
distinctly bacillary, occurring predominantly in pairs and short chains. Frequently
pleomorphic. May form narrow capsules. Nonmotile.
Colonies on blood agar are small, 0.1-0.3 mm in diameter, translucent to
semiopaque. Subsp. liquefaciens produce larger colonies (3 mm). Pitting of the agar
may be observed. Nonhemolytic, sometimes weak alpha hemolysis may occur. On
heated blood (chocolate) agar, large dark zones around the colonies usually occur.
Aerobic. Optimum growth temperature 35 ºC. No growth at 42 ºC. Good growth on
chocolate agar medium and may not grow on certain rich media without serum or
oleic acid. Unable to grow on medium MB (M. bovis medium), MacConkey agar or in
minimal medium containing ammonium and acetate.
M. lacunata subsp. lacunata has been isolated from inflamed and healthy human conjunctiva and from sites in the upper respiratory
tract; occasionally isolated from blood. Rarely isolated.
M. lacunata subsp. liquefaciens has been isolated from a case of keratitis. It has also been isolated from cases of endocarditis and
sinusitis and from the conjunctiva of healthy guinea pigs.
Admin note: we have isolated a Moraxella lacunata strain from poultry feces.
May be the causative agent of human conjunctivitis and keratitis. One report of septic arthritis.
- Elliot Juni and Kjell Bovre. Order IX Pseudomonadales Orla-Jensen 1921, Family II Moraxellaceae Rossau, Van Landschoot,
Gillis and De Ley 1991 In: Bergey’s Manual of Systematic Bacteriology, Second edition, Vol two, part B, George M. Garrity (Editor-
in-Chief), pp. 411-442.
- Anna Woodbury, James Jorgensen, Aaron Owens, Andres Henao-Martinez: Moraxella lacunata Septic Arthritis in a Patient with
Lupus Nephritis. J. Clin. Microbiol. doi:10.1128/JCM.01403-09.
- Gabriel Ionescu, Delia Berceanu-Vaduva: Cocobacili Gram negativi nefermentativi. In: (Eds.) Dumitru Buiuc, Marian Negut. Tratat
de microbiologie clinica, ed. a III-a, cap. 32.2, 787-795.
M. lacunata subsp liquefaciens is biochemically very similar to M. lacunata subsp.
lacunata, but differs in being able to grow on media without serum and to liquefy the
Positive results for alkaline phosphatase, acid phosphatase (weak), catalase,
esterase, oxidase, nitrate reduction, liquefaction of gelatin & Tween 80 hydrolysis.
Negative results for DN-ase, indole production, phenylalanine deaminase, urease,
acid production from glucose and other sugars.
(c) Costin Stoica