Halomonas: An Emerging Pathogen?
By Joseph F John, Jr., MD, FACP, FIDSA, FSHEA, Associate Chief of Staff for Education, Ralph H. Johnson Veterans Administration Medical Center; Professor of Medicine, Medical University of South Carolina, Charleston, co-editor of Infectious Disease Alert. Dr. John reports no financial relationships with this field of study.
SYNOPSIS: A 54-year old female with end stage renal disease presented with nausea, vomiting, hypertension and minimal fever. One of two blood cultures grew a gram-negative rod that was eventually identified as Halomonas jonsoniae. None of the local dialysis centers had reported such infections, however, the center under question in Santa Clara, CA reported heavy contamination with H. johnsoniae in 2009.
SOURCE: Stevens DA, et al. Halomonas jonsoniae: Review of a medically underappreciated genus of growing human importance. Am J Med Sci 2013;345:335-338.
A 54-year old female with end stage renal disease presented with nausea, vomiting, hypertension and minimal fever. One of two blood cultures grew a gram-negative rod that was eventually identified as Halomonas jonsoniae. In the current report there was no Halomonas isolated after scrupulous culturing of the dialysis unit. None of the local dialysis centers had reported such infections, however, the center under question in Santa Clara reported heavy contamination with H. johnsoniae in 2009.Two years had passed since two initial patients had bacteremia with Halomonas infection, thus there is no hint where patient exposure originated. The authors make the point that the organism is not considered in infectious disease texts as a pathogen, but with this publication and several others Halomonas has established an ability to cause infection. Although the analysis of environment did not yield halomonas, a previous epidemiologic analysis revealed that the environment and the hands of nurses were contaminated with the organism. Halomonas species are salt lovers and isolation of this genus from the environment requires special media, which may limit its ability to grow in some commercial blood culture systems.
The microbial world continues to fascinate and infect us humans. Now we have another evolving genus, halomonas, which has many species. Stevens et al have done the medical community a great service with this assiduous epidemiologic analysis of halomonas contamination in dialysis units. Clearly there is a troublesome connection between the high tonicity of dialysate, its distribution through the dialysis unit and the ability of the gram-negative bacterium species to grow in high salt concentrations. It would be interesting to know how well human blood supports halomonas growth. From this patient and several others we know it can survive long enough to grow in blood. There have also been outbreaks in neonatal units, again suggesting challenged hosts and environments that may support contamination by halomonas.
Infectious disease specialists and clinical microbiologists have a new organism to watch. Halomonas combines the potential for environmental contamination with susceptibility in patients around high salt medicaments who have risk for opportunistic infections. New pathogens do not come along that often and the medical community stands in appreciation of those investigators who can uncover these "new" organisms. In the current article, all of the references date to after 2000, the first one emanating from the great German microbiologist, Alexander von Graevenitz, who discovered and catalogued many new gram-positive bacteria during his academic life in Zurich. On the Gram-negative front he was also one of the first to report a case of the genus under question, a Halomonas venusta infection following a fish bite (J Clin Micro 2000;38:3123-4). Dr. von Graevenitz headed a renowned basic and clinical lab at the University of Zurich until the last decade, maintaining a close affiliation with investigators and infectious diseases physicians in the United States and throughout the world. During his long career, von Graevenitz befriended a global cadre of infectious disease workers, including myself. His knowledge is encyclopedic and though now less active in the laboratory, he continues to have an influence on modern clinical and academic microbiologists. The current paper on halomonas species indicates the importance of investigating and speciating new bacterial entities.