SARS-CoV-2-IgG response is different in COVID-19 outpatients and asymptomatic contact persons.

Commercially available immunoassays have been developed for sensitive and specific detection of antibodies against SARS-CoV-2. While a fast and reliable IgG response has been reported for samples from hospitalized COVID-19 patients, less is known about ambulatory patients. We evaluated the SARS-CoV-2-IgG response by the Anti-SARS-CoV-2-ELISA IgG (Euroimmun) in a defined cohort of SARS-CoV-2-PCR-confirmed outpatients and asymptomatic contact persons including 137 serum samples from PCR-confirmed outpatients (n = 111) and asymptomatic but PCR-positive contact persons (n = 26) sent to our laboratory as part of routine diagnostics for determination of SARS-CoV-2-IgG. Overall positivity rate for SARS-CoV-2-IgG was 81.1 % in outpatients (irrespective of sampling before or after day 21 after onset of symptoms) but significantly lower in asymptomatic contact persons (15.4 %, p < 0.0001). In contact persons without symptoms the ct values of the PCR assays were significantly higher (5-7 threshold cycles) than in outpatients, and ct values were significantly negative correlated to the SARS-CoV-2-IgG ratio, suggesting a lower viral load as a possible explanation for lower rate of seropositivity. In summary, our study shows that serological response to SARS-CoV-2 in outpatients including asymptomatic persons is less pronounced than in hospitalized patients. Further controlled studies are urgently needed to determine serological response in outpatients and asymptomatic persons since this is the main target population for seroepidemiological investigations.

Actinomyces hominis sp. nov., isolated from a wound swab.

A coryneform bacterium (strain 1094(T)) was isolated from a wound swab taken from an 89-year-old female patient. Chemotaxonomic investigations suggested that this bacterium was related to the genera Actinomyces, Arcanobacterium and Actinobaculum. Phylogenetic analysis of 16S rRNA gene sequences showed that strain 1094(T) was most closely related to Actinomyces europaeus CCUG 32789 A(T) (94.3 % similarity). Phenotypically, the isolate could be separated from its closest phylogenetic neighbours on the basis of being positive for catalase, CAMP reaction, acid phosphatase, N-acetyl-beta-glucosaminidase and raffinose fermentation. Based on the data presented, it is proposed that strain 1094(T) should be classified in a novel species, Actinomyces hominis sp. nov. The type strain is 1094(T) (=CCUG 57540(T) =DSM 22168(T)).

Corynebacterium mustelae sp. nov., isolated from a ferret with lethal sepsis.

A non-lipophilic coryneform bacterium, strain 3105(T), was isolated from various tissues of a ferret with lethal sepsis. The strain was characterized by phenotypic and chemotaxonomic methods, which suggested an assignment of the isolate to the genus Corynebacterium. Strain 3105(T) exhibited the following peculiar features that made it possible to differentiate it phenotypically from all other corynebacteria: its distinctive 'humid cellar'-like odour, strong adherence to agar and a greenish-beige pigment. Strain 3105(T) exhibited more than 2.8 % 16S rRNA gene sequence divergence from its closest phylogenetic neighbour, Corynebacterium pseudotuberculosis NCTC 3450(T) (97.12 % sequence similarity). Analysis of the highly variable region within the rpoB gene sequence showed that strain 3105(T) exhibited more than 14 % divergence from its closest phylogenetic relative, again C. pseudotuberculosis. Based on the data presented, it is proposed that the ferret isolate should be classified within a novel species, Corynebacterium mustelae sp. nov. (type strain 3105( T) =CCUG 57279(T) =DSM 45274(T)).

Corynebacterium canis sp. nov., isolated from a wound infection caused by a dog bite.

A non-lipophilic, coryneform bacterium isolated from a patient's wound caused by a dog bite was characterized by phenotypic, chemotaxonomic and molecular genetic methods. Chemotaxonomic features suggested assignment of the unknown bacterium to the genus Corynebacterium. The isolate exhibited the following unusual features, which made it possible to phenotypically differentiate it from all other medically relevant corynebacteria: the Gram stain showed some very filamentous rods (>15 µm in length); some cells exhibited branching; colonies were domed and adherent to agar; the micro-organism was positive for pyrazinamidase, ß-glucosidase, α-glucosidase and trypsin but negative for ß-galactosidase. 16S rRNA gene sequencing and partial rpoB gene sequencing showed that the closest phylogenetic relative, Corynebacterium freiburgense, exhibited more than 1.9 % and 17.9 % divergence with the unknown bacterium, respectively. Based on both phenotypic and molecular genetic data, it is proposed that the isolate should be classified as a novel species, Corynebacterium canis sp. nov., with the type strain 1170(T) (=CCUG 58627(T) =DSM 45402(T)).

Corynebacterium freiburgense sp. nov., isolated from a wound obtained from a dog bite.

A non-lipophilic, coryneform bacterium, isolated from a patient's wound obtained from a dog bite, was characterized by phenotypic, chemotaxonomic and molecular genetic methods. Chemotaxonomic features suggested assignment of the unknown bacterium to the genus Corynebacterium. The isolate exhibited the following peculiar features which made it possible to differentiate it phenotypically from all other medically relevant corynebacteria: older colonies exhibited a 'spoke-wheel' macroscopic morphology, colonies were strongly adherent to blood agar and the strain did not have pyrazinamidase activity, but was positive for beta-galactosidase. 16S rRNA gene sequencing showed that the closest phylogenetic relative exhibited more than 3.9% divergence from the unknown isolate. Based on phenotypic and molecular genetic data, it is proposed that the isolate should be classified as a representative of a novel species, Corynebacterium freiburgense sp. nov., with strain 1045T (=CCUG 56874T=DSM 45254T) as the type strain.

Identities of Microbacterium spp. encountered in human clinical specimens.

In the present study, 50 strains of yellow-pigmented gram-positive rods that had been isolated from human clinical specimens and collected over a 5-year period were further characterized by phenotypic and molecular genetic methods. All 50 strains belonged to the genus Microbacterium, and together they represented 18 different species. Microbacterium oxydans (n = 11), M. paraoxydans (n = 9), and M. foliorum (n = 7) represented more than half of the strains included in the present study. The isolation of strains belonging to M. hydrocarbonoxydans (n = 2), M. esteraromaticum (n = 1), M. oleivorans (n = 1), M. phyllosphaerae (n = 1), and M. thalassium (n = 1) from humans is reported for the first time. Microbacterium sp. strain VKM Ac-1389 (n = 1) and the previously uncultured Microbacterium sp. clone YJQ-29 (n = 1) probably represent new species. Comprehensive antimicrobial susceptibility data are given for the 50 Microbacterium isolates. This study is, so far, the largest on Microbacterium spp. encountered in human clinical specimens and outlines the heterogeneity of clinical Microbacterium strains.

Comprehensive study of strains previously designated Streptococcus bovis consecutively isolated from human blood cultures and emended description of Streptococcus gallolyticus and Streptococcus infantarius subsp. coli.

Modern taxonomy has delineated Streptococcus gallolyticus subsp. gallolyticus, S. gallolyticus subsp. pasteurianus, Streptococcus infantarius subsp. coli, and S. infantarius subsp. infantarius within the heterogenous group of previously designated clinical Streptococcus bovis bacteria. In the present study, 58 consecutive blood culture isolates initially designated S. bovis were further characterized by applying phenotypic and molecular genetic methods, and possible disease associations were investigated by studying the patients' records. Published phenotypic characteristics of S. gallolyticus and S. infantarius were not unequivocal and did not allow an unambiguous phenotypic differentiation of the 58 clinical isolates. However, full-length 16S rRNA gene sequences clearly assigned the strains to S. gallolyticus subsp. gallolyticus (n = 29), S. gallolyticus subsp. pasteurianus (n = 12), and S. infantarius subsp. coli (n = 17). Only 28% of the patients with available records presented with endocarditis and 7% presented with colon carcinoma, whereas 37% of the patients had altered liver parenchyma and 28% had gall bladder disease as underlying diseases. Detailed antimicrobial susceptibility data on both S. gallolyticus subspecies and S. infantarius subsp. coli are given for the first time. As a result of the extensive characterization of the largest number of S. gallolyticus and S. infantarius human clinical isolates published so far, emended species descriptions are given. It is recommended that both clinical microbiologists and infectious disease specialists avoid the designation S. bovis for true S. gallolyticus and S. infantarius strains in the future in order to get a clearer picture of the possible disease associations of these species.

Identities of Arthrobacter spp. and Arthrobacter-like bacteria encountered in human clinical specimens.

After the initial description of Arthrobacter spp. isolated from clinical specimens in the mid-1990s, very few further reports on Arthrobacter spp. have appeared in the clinical microbiology literature. The aim of the present study was to elucidate the distribution of Arthrobacter spp. and Arthrobacter-like bacteria encountered in clinical specimens by studying 50 consecutively isolated or received strains of large-colony-forming, whiteish-grayish, non-cheese-like-smelling, nonfermentative gram-positive rods by applying phenotypic methods as well as 16S rRNA gene sequencing. We observed a very heterogenous distribution, with the 50 strains belonging to 20 different taxa and each of 13 strains as a single representative of its particular taxon. Thirty-eight strains represented true Arthrobacter strains, 7 strains belonged to the genus Brevibacterium, 2 were Microbacterium species, and each of 3 single strains was a member of the rarely encountered genera Pseudoclavibacter, Leucobacter, and Brachybacterium, respectively. A. cumminsii (n = 14) and A. oxydans (n = 11) were the most frequently found species. The present report describes the first three A. aurescens strains isolated from human clinical specimens. Comprehensive antimicrobial susceptibility data are given for the 38 Arthrobacter isolates.

Comprehensive study of Corynebacterium freneyi strains and extended and emended description of Corynebacterium freneyi Renaud, Aubel, Riegel, Meugnier, and Bollet 2001.

In 2001, Corynebacterium freneyi was described as a new fermentative, alpha-glucosidase-positive Corynebacterium species related to C. xerosis based on data from three strains. During a review of our extensive culture collection we encountered 18 additional C. freneyi strains and further characterized them in detail. Thirteen of the 18 strains were isolated from female genital tract specimens without any obvious disease association. Phenotypically, C. freneyi can be easily differentiated from C. xerosis by its distinct wrinkled colonies whereas nearly all other routinely applied phenotypic tests do not allow a unanimous separation of C. freneyi from C. xerosis. Restriction length polymorphism analysis using CfoI of the 16S-23S rRNA gene intragenic spacer definitively allows differentiation between the two species. Surprisingly, comparative 16S rRNA gene analysis does not discriminate between C. freneyi and C. xerosis because the designated type strain of C. freneyi is not the most representative strain for this species. The present report also includes detailed data on the antimicrobial susceptibility pattern of C. freneyi presented here for the first time. Based on the large number of additional C. freneyi strains from our culture collection, we provide an extended and emended species description of C. freneyi.

First description of Curtobacterium spp. isolated from human clinical specimens.

During a 4-year period, five strains (three of which were doubtless clinically significant) of yellow- or orange-pigmented, oxidative, slowly acid-producing coryneform bacteria were recovered from human clinical specimens in two reference laboratories or referred to them. The strains were motile, catalase positive, nitrate reductase negative, and urease negative, but strongly hydrolyzed esculin. In all reference and clinical strains described in the present study, anteisopentadecanoic (C(15:0ai)) and anteisoheptadecanoic (C(17:0ai)) acids represented more than 75% of all cellular fatty acids except in one clinical strain and in Curtobacterium pusillum, in which both the unusual omega-cyclohexyl fatty acid (identified as C(18:1omega7cis/omega9cis/omega12trans) by the Sherlock system) represented more than 50% of all cellular fatty acids. In all clinical strains, ornithine was the diamino acid of the cell wall, the interpeptide bridge consisted of ornithine, and acetyl was the acyl type of the peptidoglycan. Therefore, the five clinical strains were unambiguously identified as Curtobacterium spp. Analyses of the complete 16S rRNA genes of the five clinical strains with homologies to the established Curtobacterium species ranging from 99.2 to 100% confirmed the identifications as Curtobacterium spp. Data on the antimicrobial susceptibility pattern of curtobacteria are reported, with macrolides and rifampin showing very low MICs for all strains tested. This report is the first on the isolation of Curtobacterium strains from human clinical specimens.

First comprehensively documented case of Paracoccus yeei infection in a human.

Paracoccus yeei was isolated in pure culture from an aerobic blood culture and bulla fluid from a 67-year-old male. The biochemical identification scheme for this recently described species is outlined. Because of its reaction pattern it is not unlikely that P. yeei is underdiagnosed.