Antimicrobial Resistance in Enterococci

Background. Enterococcus spp. are opportunistic agents of community-acquired and in-hospital infections, which have been considered a threat to public health due to their antimicrobial resistance, primarily to glycopeptides, in recent years.The aim of the study is to determine the prevalence of various Enterococcus species causing infections in hospitalized patients and their antimicrobial resistance.Methods included identification by MALDI-TOF mass spectrometry and antimicrobial susceptibility testing in accordance with the EUCAST or, in their absence, CLSI guidelines.Results. Antimicrobial resistance in 1562 consecutive Enterococcus strains isolated from hospitalized patients was determined in a major medical center admitting patients from various regions of the Russian Federation in 2019. The predominance of E.faecalis and E.faecium (99.5%) was revealed; the frequency of isolation of the former was 56% higher than that of the latter. E.avium, E.casseliflavus, E.gallinarum, E.durans were isolated from 0.5% of biological samples. The highest level of resistance of enterococci was observed to erythromycin (84.8%), tetracycline (75.0%), and rifampicin (68.2%). Multidrug, as well as vancomycin resistance, prevailed in E.faecium. All E.faecium strains isolated from blood were multidrug resistant. Resistance to vancomycin in enterococci, causing bloodstream infections, was observed solely in 19.5% of E.faecium; all vancomycin-resistant isolates were also resistant to teicoplanin. Linezolid resistance was detected in 2 community-acquired strains of E.faecalis (0.1%). Rare enterococci have shown diverse patterns of antimicrobial resistance.Conclusions. E.faecalis and E.faecium prevailed among Enterococcus spp. causing infections in hospitalized patients. Multidrug resistance and vancomycin resistance were observed predominantly in E.faecium, especially in strains causing blood-stream infections. Further monitoring of the spread and antimicrobial resistance of various Enterococcus spp. in hospital and community-acquired infections is needed.

The Emergence of Linezolid-resistant Staphylococcus Epidermidis in the COVID-19 Hospitalized Intubated Patients in North Khorasan, Iran

BackgroundIn the COVID-19 pandemic from 2019 to date, we confront secondary bacterial and viral infections in SARS-CoV2 infected patients, especially hospitalized patients. Coagulase-negative staphylococci, are commensals of the human body and can lead to infections in immunocompromised patients. The antimicrobial resistance is increasingly reported in coagulase-negative staphylococci, especially in Staphylococcus epidermidis. One of the most critical problems is resistance to linezolid in S. epidermidis, observed in Europe since 2014. The aim of this study was to evaluation of bacterial Co-infections and determination of antimicrobial resistance pattern of co-infection isolated strains in North Khorasan, Iran, in the last six-month period. MethodsAfter microbiological evaluation of pulmonary samples of hospitalized intubated patients with signs of bacterial pneumonia, we found co-infection in 11 of 185 patients with S. epidermidis, S. aureus, and Acinetobacter baumani, respectively. Interestingly seven of nine S. epidermidis isolates were linezolid resistant. For identification of the isolates at the species level, we used phenotypic methods and also the Polymerase Chain Reaction (PCR) for the atlE gene. Selected isolates were characterized by determining their antimicrobial resistance patterns and using molecular methods including SCCmec typing, detection of ica, mecA, vanA, and cfr genes. ResultsAll isolates were resistant to methicillin, and Seven isolates were resistant to linezolid. It should be noted that all nine isolates were positive for the ica gene. Nine of 11 isolated have belonged to the SCCmec I, and two belonged to the SCCmec IV. It should be noted that all patients had the underlying disease and six patients died.ConclusionThe increasing linezolid resistance in bacterial strains becomes a real threat for patients, and monitoring such infections combined with surveillance and infection prevention programs is very important to decrease the number of linezolid-resistant staphylococcal strains.

1250. Development of Linezolid and Daptomycin Resistance in Vancomycin Resistant Enterococcus faecium (VRE) during prolonged treatment for Intraabdominal Abscess

Background Vancomycin-resistant enterococci (VRE) are nosocomial pathogens with extensive intrinsic and acquired antimicrobial resistance (AMR) mechanisms. We report a case in which intraabdominal (IA) and blood cultures grew linezolid and daptomycin resistant VRE (DLVRE). Methods We report a case of DLVRE bacteremia after prolonged treatment with linezolid and daptomycin. Results The patient was a 65-year-old female with a history of multiple abdominal surgeries who presented for elective incisional hernia repair. Her post-operative course was complicated by the development of loculated IA abscesses. A drain was placed into the largest abscess, and aspiration cultures were polymicrobial containing vancomycin-resistant E. faecium (Isolate 1). The patient was treated meropenem, fluconazole and linezolid for 6 weeks. Clinical and radiographic improvement was achieved. However, 4 days after competing antibiotics she developed recurrent abdominal pain and a leukocytosis. Daptomycin was chosen out of concern for long-term linezolid toxicity and IA cultures demonstrated new linezolid resistance (Isolate 2, LVRE). After an additional three weeks of therapy, she developed a catheter-associated bloodstream infection (CLABSI). Blood cultures revealed daptomycin-resistant LVRE bacteremia (Isolate 3, DLVRE). She was started empirically on a combination of ceftaroline and daptomycin, her PICC line removed, and her blood cultures cleared. Her antibiotic course is presented in Figure 1 and resistance patterns of the VRE in Table 1. Conclusion In this patient, an IA abscess known to harbor VRE developed resistance to both linezolid and daptomycin during prolonged treatment with both agents. Ultimately, the patient experienced an episode of CLABSI DLVRE. Limited data exists on appropriate antibiotic choice in such challenging situations. Based on prior clinical and experimental data, we elected to use daptomycin in conjunction with ceftaroline for synergy, and the patient achieved the desired clinical response, clearance of her blood cultures and diminishing size of her IA abscess. Further work is needed to elucidate the best course of treatment for patients with VRE requiring long-term antibiotic therapy and for those who have developed extensively drug-resistant E. faecium. Disclosures All Authors: No reported disclosures

First Report of the Plasmid-Mediated fosB Gene in Enterococcus faecalis from Pigs

Plasmid-mediated fosfomycin determinants is a global public health concern due to the increasing dissemination of fosfomycin resistance and limited clinical treatment options. Information about the fosfomycin resistant and molecular genetic among Enterococcus spp. is still lacking. In this study, we found the first plasmid-medieted fosB in Enterococcus faecalis from pigs, and all the fosfomycin resistant Enterococcus spp. (FRE) isolates were multi-drug resistant. S1-PFGE, Southern blot and conjugation experiments indicated that the fosB gene located on ~54.7 kb transferable plasmids. Relative competition assay confirmed that the fosB-carrying plasmid impaired fitness in recipient E. faecalis JH2-2. Illumina and the MinION sequencing data revealed that both E. faecalis ES-1 and ES-2 isolates belonged to novel ST (ST964), and had 71 SNPs difference. WGS showed that the genetic environments of fosB were diverse among different species, and the linezolid resistance gene optrA was found in the fosB-carrying strains. To summarize, for the first time, we reported plasmid-mediated fosB in E. faecalis from pigs. And, the co-occurrence of fosB and optrA pose a serious threat to public health.

Genetic Profile of Linezolid-Resistant M. tuberculosis Clinical Strains from Moscow

Background: Linezolid, bedaquiline, and newer fluoroquinolones are currently placed as priority Group A drugs for the treatment of drug-resistant tuberculosis. The number of reported linezolid-resistant clinical strains is still low, and the correlation of molecular determinants with phenotype is not perfect. Methods: We determined the linezolid MICs for clinical isolates from the Moscow region and identified mutations in rplC and rrl genes. Results: All 16 linezolid-resistant isolates had previously reported mutations in the rplC or rrl loci, and 13 of them bore a RplC C154R substitution. Detection of this substitution in a heteroresistant state was not successful, probably, due to the more stable DNA secondary structure of the mutated fragment, which precludes its amplification in mixes with the wild-type DNA. Strains with an rplC mutation had higher linezolid MIC compared to isolates with rrl mutations. Conclusions: Linezolid resistance mostly emerged during treatment with the latest regimen. Three primary cases with linezolid resistance question the possible transmission of totally drug-resistant tuberculosis in the Moscow region, which demands further investigation.