Moraxella nonliquefaciens and M. osloensis Are Important Moraxella Species That Cause Ocular Infections

Abstract

Moraxella is an ocular bacterial pathogen isolated in cases of keratitis, conjunctivitis, and endophthalmitis. Gram-negative brick-shaped diplobacilli from ocular specimens, and slow growth in culture, are early indications of Moraxella ocular infection; however, identifying Moraxella to species can be complex and inconsistent. In this study, bacteria consistent with Moraxella were identified to species using: (1) DNA sequencing coupled with vancomycin susceptibility, (2) MALDI-TOF mass spectrometry, and (3) the Biolog ID system. Study samples consisted of nine ATCC Moraxella controls, 82 isolates from keratitis, 21 isolates from conjunctivitis, and 4 isolates from endophthalmitis. The ATCC controls were correctly identified. For keratitis, 66 (80.5%) were identified as M. nonliquefaciens, 7 (9.0%) as M. lacunata, 5 (6%) as M. osloensis, 2 (2.5%) as Acinetobacter lwoffii, 1 (1.0%) as M. bovis/nonliquefaciens, and 1 (1.0%) as M. osloensis/nonliquefaciens. For conjunctivitis, 9 (43.0%) were identified as M. osloensis, 6 (29.0%) as M. nonliquefaciens, 3 (14.3%) as Roseomonas, 2 (9.5%) as Acinetobacter (parvus, junii), and 1 (4.5%) as M. catarrhalis/nonliquefaciens. From endophthalmitis, 3 of 4 of the isolates were M. nonliquefaciens. Overall, M. nonliquefaciens and M. osloensis were identified in 70% (75 of 107) and 13% (14 of 107) of cases, respectively, totaling 83% (89 of 107). M. nonliquefaciens and M. osloensis are important bacterial pathogens of the eye as determined by DNA sequencing, MALDI-TOF MS, and Biolog. Although Moraxella catarrhalis is a clinical pathogen, other species of Moraxella appear to have a prominent role in eye infections.

Keywords: Biolog; DNA sequencing; MALDI-TOF MS; Moraxella; conjunctivitis; endophthalmitis; eye infections; keratitis.

Figure 1

The presence of Moraxella diplobacilli from corneal scrapings using Gram stain (left picture) and Giemsa (right picture). The pictures were photographed under (100× oil immersion).

Figure 2

Fried egg appearance of Moraxella growing on trypticase soy agar supplemented with 5% sheep blood. The colonies were magnified by 20×.

Figure 3

A diagram of the neighbor joining tree of 16S rRNA sequences for the Moraxella isolates in the study. Panel (A) details the neighbor joining tree (25) constructed with all sequences from this study and relevant type strains. Clades corresponding to M. nonliquefaciens/M.catarrhalis and M. osloensis are condensed. Panel (B) depicts clades corresponding to M. nonliquefaciens/M.catarrhalis. Panel (C) corresponds to M. osloensis. Red indicates strains from our clinical collection and black indicates select type strains. The vancomycin susceptibility status is indicated as S for susceptible and R for resistant.