ANSWERS TO SELF-ASSESSMENT QUESTIONS
1. Ignatzschineria sepsis has been most frequently associated with which of the following preexisting conditions?
a. Diabetes mellitus
b. Hypertension
c. Bipolar disorder
d. Alcohol use disorder
Answer: d. Ignatzschineria infection has been associated with definitive or probable maggot infestation of wounds in all reported cases to date. Medical conditions that cause peripheral neuropathy predispose to the formation of pressure ulcers. Additionally, sensory impairment can cause these wounds to go unnoticed by the patient and result in delayed clinical attention. Maggot infestation of wounds, in particular, typically presents in the context of additional psychosocial impairment due to the degree of neglect necessary for maggot colonization to occur. Both diabetes mellitus and alcohol use disorder are associated with peripheral neuropathy, and while bipolar disorder can be associated with psychosocial impairment, it does not cause peripheral neuropathy. Alcohol use disorder is associated with both neuropathy and psychosocial impairment, and, as a result, nearly all cases of human Ignatzschineria infection have been reported in patients with chronic alcohol use disorder.
2. Which of the following methods can be used to accurately differentiate Ignatzschineria species from one another?
a. Oxidase and catalase reactions
b. MALDI-TOF mass spectrometry
c. 16S rRNA sequencing
d. Whole-genome sequencing
Answer: d. Ignatzschineria species cannot be accurately differentiated by routine biochemical tests, such as oxidase and catalase reactions. In addition, commercial MALDI-TOF mass spectrometry libraries do not contain entries for I. larvae or I. ureiclastica. Furthermore, 16S rRNA sequencing shows nearly identical homology between I. larvae and I. ureiclastica species. As demonstrated in this case, only through whole-genome sequencing was species-level identification of Ignatzschineria larvae possible.
3. The principle arthropod vector of Ignatzschineria is also a major vector of which of the following bacterial species?
a. Aeromonas hydrophila
b. Wohlfahrtiimonas chitiniclastica
c. Wohlfahrtia magnifica
d. Chryseobacterium gleum
Answer: b. Ignatzschineria bacteria are transmitted through larvae of the spotted flesh fly, Wohlfhartia magnifica, a member of the Sarcophagidae family. W. magnifica larvae are a known cause of cutaneous myiasis in humans and animals. They are also a major vector of the bacterium Wohlfahrtiimonas chitiniclastica, which can cause wound infections and bacteremia in humans, although other fly species have also been described as vectors for W. chitiniclastica.
TAKE-HOME POINTS
Ignatzschineria species are increasingly recognized as a cause of severe invasive infections in humans, including bacteremia and sepsis.
Ignatzschineria infection is associated with maggot infestation of open wounds; therefore, most case reports to date describe patients with peripheral neuropathy in association with psychosocial impairment.
Ignaztschineria species are transmitted to humans through the larvae of Wohlfhartia magnifica, the spotted flesh fly, which is also a major vector of the bacterium Wohlfhartimonas chinitiniclastica.
Reliable species-level identification of Ignatzschineria is challenging in the clinical laboratory and may not be possible by phenotypic methods or 16S rRNA sequencing. However, genus-level identification is sufficient for clinical management of infected patients.
See https://doi.org/10.1128/JCM.02279-20 in this issue for case presentation and discussion.
- Copyright © 2021 American Society for Microbiology.
