Abstract
In the past 12 years, several case reports have clearly demonstrated that Wohlfahrtiimonas chitiniclastica is capable of causing sepsis and bacteremia in humans. However, since most clinicians are not familiar with this species, little is known about its pathogenicity and treatment options while it is as rare but underestimated human pathogen. Therefore, a larger strain collection is required so that methods can be identified that are most suitable to obtain rapid and reliable identification. Moreover, the antimicrobial resistance profile needs to be elucidated in order to explore possible treatment options. Over a period of 6 years, we therefore have collected a total of 14 W. chitiniclastica isolates in routine diagnostics, which now served as the basis for a comprehensive characterization with respect to identification and antibiotic profiling. We compared the accuracy and convenience of several identification techniques in which MALDI-TOF MS and sequencing of the 16S rRNA gene have proven to be suitable for identification of W. chitiniclastica. In addition, whole genome sequencing (WGS)-based digital DNA-DNA hybridization (dDDH) was used as a reference method for strain identification, and surprised with the detection of a novel W. chitiniclastica subspecies. A combination of in silico and in vitro analyses revealed a first insight into the antimicrobial resistance profile and the molecular basis of antimicrobial resistance. Based on our findings, trimethoprim/sulfamethoxazole, levofloxacin, and cephalosporins (e.g., ceftazidime) may be the best antibiotics to use in order to treat infections caused by W. chitiniclastica, while resistance to fosfomycin, amikacin and tobramycin is observed.
Highlights
The gammaproteobacterium Wohlfahrtiimonas chitiniclastica has first been isolated from larvae of Wohlfahrtia magnifica (Tóth et al, 2008), an obligatory parasitic fly that causes myiasis by depositing eggs and larvae in mammalian wounds both in animals and humans (Robbins and Khachemoune, 2010)
VITEK 2 results of W. chitiniclastica lead to misidentification as Acinetobacter lwoffii of all strains included in this study (Table 3), which has been reported in previous case reports
For the remaining isolates, the results were above 96%, representing an excellent species identification; in our study a misidentification as A. lwoffii was evident for all strains
Summary
The gammaproteobacterium Wohlfahrtiimonas chitiniclastica has first been isolated from larvae of Wohlfahrtia magnifica (Tóth et al, 2008), an obligatory parasitic fly that causes myiasis by depositing eggs and larvae in mammalian wounds both in animals and humans (Robbins and Khachemoune, 2010). Bacteria belonging to this species are described as Gram-negative, strictly aerobic, and non-motile rods. In-depth analysis is still required to generate a comprehensive antimicrobial resistance profile as the available antimicrobial susceptibility data are mostly based on case reports and preliminary genome annotations (Zhou et al, 2016; Schröttner et al, 2017; Matos et al, 2019)
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