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No source of Herbaspirillum spp. identified in cluster of patients
No environmental or common source was identified as the cause of Herbaspirillum spp. infections among a cluster of eight patients with cancer receiving care at The University of Texas MD Anderson Cancer Center, according to recent study results.
“Our joint public health investigation and environmental sampling did not reveal a source of Herbaspirillum spp.,” the investigators wrote in Clinical Infectious Diseases. “While other opportunistic soil and waterborne bacteria were recovered, these organisms were not found in greater than expected counts for treated municipal water. We did not identify any pervasive infection control lapses that could explain acquisition of this organism.”
Between June and August 2011, a cluster of five patients with bloodstream infections was identified. The bacteria was initially identified as Burkholderia cepacia, but further testing identified the isolates as Herbaspirillum spp. The investigators conducted a retrospective review of B. cepacia isolates previously recovered to determine whether any additional Herbaspirillum spp. cases were misidentified. They also reviewed microbiology records prospectively to identify additional cases.
There were eight patients identified, including the original five and three identified prospectively. The isolates from four patients in the original cluster were indistinguishable by pulsed-field gel electrophoresis (PFGE). Isolates from the three subsequent patients had different PFGE patterns. There were no isolates available for typing from the additional patient in the original cluster.
Seven of the patients presented with bacteremia and one of the patients presented with polymicrobial pneumonia. Five of the patients had hospital-onset infections and the other three were hospitalized for community-onset infections. All of the patients had central venous catheters in place at the time of infection except for the patient who presented with pneumonia.
There were no common exposures among the initial cluster of patients, which included one of the community-onset cases. They were all hospitalized during the same time frame, but located on different wards and floors and did not have common health care providers. Only the main water supply system was common to all patients. There were no observed breaches in infection control practices. Lastly, there were no Herbaspirillum spp. or B. cepacia recovered from 40 environmental samples.
“While a source and mechanism of acquisition was not identified in this study, the organism may enter the body via intravenous infusions, the respiratory tract, environmental contamination of lacerated skin or ingestion of uncooked vegetable products,” the researchers wrote. “Herbaspirillum spp. may be widely misidentified as B. cepacia by current testing methods, therefore improved identification methods and increased awareness are necessary to document the true prevalence of this pathogen in human hosts and identify preventive measures.”
Disclosure: The researchers report no relevant financial disclosures.