Relevance of Dermabacter hominis isolated from clinical samples, 2012-2016: a retrospective case series

Antimicrobial susceptibility testing of Dermabacter hominis

Dermabacter hominis, a short gram-positive rod, is a part of the human skin flora, but can also cause infections (e.g., skin and soft tissue infections, bone and joint infections, abscesses, peritoneal dialysis-associated peritonitis, and bacteremia). Only limited data are available for antimicrobial resistance rates. Although CLSI does include coryneform genera in Corynebacterium spp. clinical breakpoints, they point out that only limited data are available on resistance rates. The aim of this study was to assess the minimal inhibitory concentration (MIC) of clinical isolates of D. hominis and to deduce breakpoints for disk diffusion. D. hominis (n = 30) from five laboratories in Germany were tested by broth microdilution and disk diffusion method. MICs were interpreted according to current clinical breakpoints for Corynebacterium spp. or pharmacokinetic-pharmacodynamic breakpoints (EUCAST). To deduce breakpoints for disk diffusion, MICs were correlated with inhibition zone diameters. All isolates were susceptible to vancomycin, rifampicin, and linezolid (100%, n = 30/30). Lower susceptibility rates were found for ampicillin (83%, n = 25/30) followed by ceftriaxone (37%, n = 11/30) and clindamycin (27%, n = 8/30). All isolates were resistant to benzylpenicillin and daptomycin. Good correlations between disk diffusion and MIC (suggested breakpoints for susceptibility in brackets) were found for ampicillin (S ≥ 10 mm), ceftriaxone (S ≥ 24 mm), clindamycin (S ≥ 19 mm), levofloxacin (I ≥ 24 mm), linezolid (S ≥ 29 mm), rifampicin (S ≥ 38 mm), and vancomycin (S ≥ 21 mm). Due to limited variances in both MIC values and inhibition zone diameters, no disk diffusion breakpoint could be deduced for gentamicin and benzylpenicillin in our dataset. D. hominis has favorable susceptibility rates for vancomycin, rifampicin, and linezolid and shows correlations between MIC and disk diffusion diameter for selected antimicrobial agents. Thus, the development of clinical breakpoints for disk diffusion appears feasible.

IMPORTANCE

Dermabacter hominis can cause infections in humans (e.g., skin and soft tissue infections, bone and joint infections, abscesses, peritoneal dialysis-associated peritonitis, and bacteremia). Currently, only limited data are available regarding the resistance rates of this specific pathogen. Data for the easy accessible disk diffusion method are missing. We were able to provide additional data on resistance rates of clinical D. hominis isolates to common antimicrobial agents and correlate these with disk diffusion diameters to derive breakpoints to further improve the antimicrobial susceptibility testing for this specific pathogen. In addition to that, we created a current overview of resistance rates from the existing literature. Our data provide deeper insight into resistance rates and antimicrobial susceptibility testing of this specific pathogen.

A complex case of bacterial pericarditis caused by a new pathogenic agent

Dermabacter hominis is a gram-positive facultative anaerobic agent. It is a human skin colonizer that can be responsible for opportunistic infections in immunocompromised patients. To date, the infections caused by this agent are related to bone, joint, eye, peritoneal dialysis catheters, abscesses or infected vascular grafts. Overall, it has a favorable outcome with good response to vancomycin, teicoplanin or linezolide, and so it has not been considered a concerning pathogenic agent. We present the first case in scientific literature with isolation of D. hominis in pericardial fluid in the setting of infectious bacterial pericarditis, with an aggressive course and poor evolution.

Establishment of a Real-Time PCR Assay for the Detection of Devriesea agamarum in Lizards

(1) Background: Devriesea (D.) agamarum is a potential cause of dermatitis and cheilitis in lizards. The aim of this study was to establish a real-time PCR assay for the detection of D. agamarum. (2) Methods: Primers and probe were selected targeting the 16S rRNA gene, using sequences of 16S rRNA genes of D. agamarum as well as of other bacterial species derived from GenBank. The PCR assay was tested with 14 positive controls of different D. agamarum cultures as well as with 34 negative controls of various non-D. agamarum bacterial cultures. Additionally, samples of 38 lizards, mostly Uromastyx spp. and Pogona spp., submitted to a commercial veterinary laboratory were tested for the presence of D. agamarum using the established protocol. (3) Results: Concentrations of as low as 2 × 10⁴ colonies per mL were detectable using dilutions of bacterial cell culture (corresponding to approximately 200 CFU per PCR). The assay resulted in an intraassay percent of coefficient of variation (CV) of 1.31% and an interassay CV of 1.80%. (4) Conclusions: The presented assay is able to detect D. agamarum in clinical samples, decreasing laboratory turn-around time in comparison to conventional culture-based detection methods.

Conjunctival sac microbiome in anophthalmic patients: Flora diversity and the impact of ocular prosthesis materials

Purpose

To explore the changes of bacterial flora in anophthalmic patients wearing ocular prosthesis (OP) and the microbiome diversity in conditions of different OP materials.

Methods

A cross-sectional clinical study was conducted, involving 19 OP patients and 23 healthy subjects. Samples were collected from the upper, lower palpebral, caruncle, and fornix conjunctiva. 16S rRNA sequencing was applied to identify the bacterial flora in the samples. The eye comfort of each OP patient was determined by a questionnaire. In addition, demographics information of each participant was also collected.

Results

The diversity and richness of ocular flora in OP patients were significantly higher than that in healthy subjects. The results of flora species analysis also indicated that in OP patients, pathogenic microorganisms such as Escherichia Shigella and Fusobacterium increased significantly, while the resident flora of Lactobacillus and Lactococcus decreased significantly. Within the self-comparison of OP patients, compared with Polymethyl Methacrylate (PMMA), prosthetic material of glass will lead to the increased colonization of opportunistic pathogens such as Alcaligenes, Dermabacter and Spirochaetes, while gender and age have no significant impact on ocular flora.

Conclusions

The ocular flora of OP patients was significantly different from that of healthy people. Abundant colonization of pathogenic microorganisms may have an important potential relationship with eye discomfort and eye diseases of OP patients. PMMA, as an artificial eye material, demonstrated potential advantages in reducing the colonization of opportunistic pathogens.

Circulating microbial content in myeloid malignancy patients is associated with disease subtypes and patient outcomes

Although recent work has described the microbiome in solid tumors, microbial content in hematological malignancies is not well-characterized. Here we analyze existing deep DNA sequence data from the blood and bone marrow of 1870 patients with myeloid malignancies, along with healthy controls, for bacterial, fungal, and viral content. After strict quality filtering, we find evidence for dysbiosis in disease cases, and distinct microbial signatures among disease subtypes. We also find that microbial content is associated with host gene mutations and with myeloblast cell percentages. In patients with low-risk myelodysplastic syndrome, we provide evidence that Epstein-Barr virus status refines risk stratification into more precise categories than the current standard. Motivated by these observations, we construct machine-learning classifiers that can discriminate among disease subtypes based solely on bacterial content. Our study highlights the association between the circulating microbiome and patient outcome, and its relationship with disease subtype.