During the period 7/2020–9/2021, stool samples of patients were collected for further analyzes. We detected 113 stool samples positive for Clostridioides difficile toxin. From this number, 44 and 31 were positive for VRE and VSE using CHROMID® VRE and Bile esculin agars, respectively. In the VSE group, 68% (21 isolates) of E. faecium and 32% (10 isolates) of E. faecalis were detected. Among VRE isolates (Fig. 1), the most prevalent were E. faecium (27 isolates; 61.3%), E. faecalis (9 isolates; 20.4%), E. solitarius (4 isolates; 9.0%), E. durans (2 isolates; 4.5%), E. sulfurous (1 isolate, 2.2%), and E. raffinosus (2.2%). All of these isolates were tested for antibiotic susceptibility and analyzed for the presence or absence of vanA/vanB genes. For the VRE isolates, the MIC was established for vancomycin (VAN, Table 1) and teicoplanin (TEI, Table 2). As many as 41 VRE isolates showed the MIC for VAN greater than 256 µg/mL (92%). Three isolates reached the MIC of 192 µg/mL (6%) and one 128 µg/mL (2%).

Distribution of VRE isolates based on biochemical identification

From 44 VRE isolates, 16 gained the MIC for TEI of 192 µg/mL and greater. The second group includes isolates with a MIC of 128 µg/mL (3 isolate E. faecium and 1 isolate E. faecalis) and the third with a MIC of 96–64 µg/mL (5 isolates of E. faecium). However, most of the VRE isolates showed a MIC of 16–1 µg/mL (3 isolates E. faecalis, 4 isolates E. solitarius, 2 isolates E. durans, 1 isolate E. raffinosus, 1 isolate E. sulfurous, 1 isolate E. faecalis).

We detected 18 isolates with the presence of the vanB genotype (7 isolates E. faecalis, 4 isolates E. solitarius, 3 isolates E. faecium, 2 isolates E. durans, 1 isolate E. sulfurous, and E. raffinosus) and 26 isolates with vanA genotype (24 isolates E. faecium, 2 isolates E. faecalis). Among the isolates with the vanA genotype character, we observed 26 isolates with MIC for TEI 64 µg/mL or higher. The vanA genotype of E. faecium (Table 3) manifested resistance against penicillin, chloramphenicol, nitrofurantoin, streptomycin, and trimethoprim/sulfamethoxazole (resistance between 75.0 and 4.1%). We confirmed 2 isolates resistance against linezolid (resistance 8.3%). The vanB genotype of E. faecalis (Table 4) had resistance levels similar to the E. faecium vanA genotype against penicillin at a level of 86.0%. Against other ATBs, the level of resistance ranged from 14.0 to 28.5%.

From the others isolates (Table 5), the most frequent isolate was confirmed than a the E. solitarius vanB genotype with resistance against penicillin at the level of 50.0%. The equal status was identified in the E. durans vanB genotype (2 isolates). Isolates with confirmation of the vanA genotype were not detected. All isolates characterized by the gene in the study are presented in Fig. 2.

Distribution of vanA/vanB genes from isolates (p < 0.001***) (ANOVA, one-way analysis of variance, SPSS 21.0)

We observed significant differences in the distribution between vanA and vanB genotypes of E. faecium (p < 0.001), and the same situation was occurred in the case of E. faecalis (p < 0.001) genotypes.

From the category with gastrointestinal diagnoses (Table 6), we studied 13 clinical isolates. In this group, the mean age was 71 years ± 10.9 SD. The group revealed a sex ratio of 54% women and 46% men. The most frequent diagnosis was infectious gastroenteritis (n = 6). From patients with gastroenteritis, we characterized isolates with the presence of genotype vanB (n = 5) and 1 isolate with genotype vanA of E. faecium. These isolates had a similar MIC character to VAN and TEI. From patients with Clostridioides difficile enterocolitis, we isolated 2 isolates (E. faecalis and E. solitarius) with the vanB genotype. Genotype with character of vanB E. faecalis was also confirmed from patient with acute pancreatitis. E. faecium genotype vanA was confirmed in cases of ileus, function dyspepsia, and unspecified liver diseases. From this group (Fig. 3), we have confirmed statistical significance beetwen the vanA and vanB genotype E. faecium (p < 0.001).

Distribution of vanA/vanB genes in cases of gastrointestinal tract diagnosis (p < 0.001*** (ANOVA, one-way analysis of variance, SPSS 21.0)

From the category (Table 7) with respiratory tract infections and diagnoses, we studied 19 clinical isolates. In this group, the mean age was 72 years ± 19.8 SD and the sex ratio was 90% female and 10% men. The most frequent diagnosis was viral pneumonia (n = 10), including SARS-CoV-19 (n = 4). From these patients, we characterized isolates with the presence of vanA (n = 5) and vanB (n = 5) (n = 4 E. faecium vanA; n = 1 E. faecium vanB; n = 1 E. faecalis vanA and E. faecalis vanB; n = 1 E. durans vanB and E. solitarius vanB). The MIC for VAN varies from 128 to > 256 µg/mL and for MIC TEI, there is a wide interval of 4 to 192 µg/mL. The second most frequent diagnosis was respiratory failure (n = 6), including 3 cases of acute respiratory failure. From these patients, we characterized isolates with the presence of vanA (n = 4) and vanB (n = 2) (n = 4 E. faecium vanA; n = 2 E. faecalis vanB). The MIC for TEI was 6 to 192 µg/mL, and all isolates gained an MIC for VAN higher than > 256 µg/mL. The last diagnoses from respiratory diagnosis were confirmed as unspecified bacterial pneumonia (n = 2) and a patient with dyspnea. From group of respiratory tract diagnoses (Fig. 4), we identified statistical significance among the vanA and vanB genotype E. faecium (p < 0.001), also among the vanA and vanB genotype E. faecalis (p < 0.001).

Distribution of vanA/vanB genes in cases of diagnosis of the gastrointestinal tract (p < 0.001***) (ANOVA, one-way analysis of variance)

The last category of patients (Table 8) is heterogeneous and includes a wide spectrum of chronic and acute diagnoses that could not be classified into the previous categories. In this group, the mean age was 80 years ± 8.7 SD. The group consisted of 54% of women and 46% of men. The most frequent isolate in this group was E. faecium vanA genotype (n = 8) in association with volume depletion, unspecified fever, malignant neoplasm of the bladder wall, iron deficiency anemia, unspecified bacterial infection, heart failure, and gangrene also with ischemic stroke. These isolates had a MIC for VAN higher than > 256 µg/mL. We identified the second most frequent isolate as E. faecalis vanA genotype (n = 2) and 1 isolate vanB genotype. In a patient with cerebral infarction due to embolism, E. faecalis vanB genotype was confirmed. This isolate had a MIC for TEI of 128 µg/mL and VAN > 256 µg/mL. The last isolates identified in this group were E. sulfurous and E. solitarius. Both isolates have vanB character of genotypes (Fig. 5).

Distribution of vanA/vanB genes in the cases of other types of diseases and diagnosis