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ABSTRACT Clostridioides difficile, the primary cause of nosocomial antibiotic-associated diarrhea, has a complex relationship with antibiotics. While the use of broad-spectrum antibiotics disrupts the gut microbiota and increases the risk of C. difficile infection (CDI), antibiotics are also the primary treatment for CDI. However, only a few antibiotics, including vancomycin, fidaxomicin, and rifaximin, are effective against CDI, and resistance to these antibiotics has emerged recently. In this study, we report the identification of two RT027 C. difficile clinical isolates (TGH35 and TGH64) obtained from symptomatic CDI-diagnosed patients in Tampa, Florida in 2016. These two strains showed an elevated minimum inhibitory concentration (MIC) of vancomycin (MIC = 4 μg/mL, compared to the EUCAST breakpoint of 2 μg/mL) and contained a vanRCd 343A>G mutation resulting in a Thr115Ala substitution in the VanRCd response regulator. This mutation was absent in the vancomycin-sensitive control epidemic strain RT027/R20291. TGH64 was also resistant to rifaximin (MIC ≥ 128 μg/mL) and carried the previously reported Arg505Lys and Ile548Met mutations in RpoB. Furthermore, we report on the antimicrobial resistance (AMR) and genomic characterization of additional C. difficile isolates, including RT106/TGH120, RT017/TGH33, and RT017/TGH51, obtained from the same patient sample cohort representing the highly prevalent and regionally distributed C. difficile ribotypes worldwide. Considering that the VanRCd Thr115Ala mutation was also independently reported in seven C. difficile clinical isolates from Texas and Israel in 2019, we recommend epidemiological surveillance to better understand the impact of this mutation on vancomycin resistance. IMPORTANCE The perpetually evolving antimicrobial resistance (AMR) of C. difficile is an important contributor to its epidemiology and is a grave concern to global public health. This exacerbates the challenge of treating the infections caused by this multidrug-resistant causative organism of potentially life-threatening diarrhea. Further, the novel resistance-determining factors can be transferred between different strains and species of bacteria and cause the spread of AMR in clinical, environmental, and community settings. In this study, we have identified a mutation (vanRCd 343A>G) that causes a Thr115Ala substitution and is linked to an increased MIC of vancomycin in clinical isolates of C. difficile obtained from Florida in 2016. Understanding the mechanisms of AMR, especially those of newly evolving strains, is essential to effectively guide antibiotic stewardship policies to combat antibiotic resistance as well as to discover novel therapeutic targets.

Clostridioides difficile, the primary cause of nosocomial antibiotic-associated diarrhea, has a complex relationship with antibiotics. While the use of broad-spectrum antibiotics disrupts the gut microbiota and increases the risk of C. difficile infection (CDI), antibiotics are also the primary treatment for CDI. However, only a few antibiotics, including vancomycin, fidaxomicin, and rifaximin, are effective against CDI, and resistance to these antibiotics has emerged recently. In this study, we report the identification of two RT027 C. difficile clinical isolates (TGH35 and TGH64) obtained from symptomatic CDI-diagnosed patients in Tampa, Florida in 2016. These two strains showed an elevated minimum inhibitory concentration (MIC) of vancomycin (MIC = 4 μg/mL, compared to the EUCAST breakpoint of 2 μg/mL) and contained a vanR Cd 343A>G mutation resulting in a Thr115Ala substitution in the VanR Cd response regulator. This mutation was absent in the vancomycin-sensitive control epidemic strain RT027/R20291. TGH64 was also resistant to rifaximin (MIC ≥ 128 μg/mL) and carried the previously reported Arg505Lys and Ile548Met mutations in RpoB. Furthermore, we report on the antimicrobial resistance (AMR) and genomic characterization of additional C. difficile isolates, including RT106/TGH120, RT017/TGH33, and RT017/TGH51, obtained from the same patient sample cohort representing the highly prevalent and regionally distributed C. difficile ribotypes worldwide. Considering that the VanR Cd Thr115Ala mutation was also independently reported in seven C. difficile clinical isolates from Texas and Israel in 2019, we recommend epidemiological surveillance to better understand the impact of this mutation on vancomycin resistance. IMPORTANCE The perpetually evolving antimicrobial resistance (AMR) of C. difficile is an important contributor to its epidemiology and is a grave concern to global public health. This exacerbates the challenge of treating the infections caused by this multidrug-resistant causative organism of potentially life-threatening diarrhea. Further, the novel resistance-determining factors can be transferred between different strains and species of bacteria and cause the spread of AMR in clinical, environmental, and community settings. In this study, we have identified a mutation ( vanR Cd 343A>G) that causes a Thr115Ala substitution and is linked to an increased MIC of vancomycin in clinical isolates of C. difficile obtained from Florida in 2016. Understanding the mechanisms of AMR, especially those of newly evolving strains, is essential to effectively guide antibiotic stewardship policies to combat antibiotic resistance as well as to discover novel therapeutic targets., Competing Interests: The authors declare no conflict of interest.

Objectives: The objectives of the present study were to identify the species of enterococci isolated from nosocomial infections and to determine the antibiotic susceptibility pattern with reference to high-level aminoglycosides and vancomycin. Materials and Methods: Enterococci were isolated from various clinical samples collected from patients after 72 hours of hospitalization. Various species of Enterococcus were identified by standard methods. High-level aminoglycoside resistance and vancomycin susceptibility in enterococci were detected by disk-diffusion and agar-screen methods. Results: One hundred eighty enterococcal strains were isolated from various clinical samples. Various species of Enterococcus - Enterococcus fecalis 130 (72.22%), Enterococcus casseliflavus 24 (13.33%), Enterococcus fecium 17 (9.44%), Enterococcus durans 7 (3.89%) and Enterococcus dispar 2 (1.11%) - were isolated. The highest resistance to aminoglycoside was observed among E. fecium, followed by E. durans, E. fecalis and E. casseliflavus, both by disk-diffusion and agar-screen methods. The high-level aminoglycoside resistance (HLAR) was significantly (P

Objectives Limited data exist regarding the role of agr dysfunction in reducing susceptibility to vancomycin in methicillin-susceptible Staphylococcus aureus (MSSA). This study investigated the clinical and molecular epidemiology of MSSA causing bacteraemia, with emphasis on the reduced susceptibility to vancomycin (RSV) phenotype (MIC ≥1.5 mg/L) and its relationship with agr dysfunction. Methods All MSSA bloodstream isolates obtained at our hospital during 2010 were analysed. Antimicrobial susceptibility was determined and time–kill experiments were performed for oxacillin. Multilocus sequence type and agr genotype were determined and DNA microarray analysis of virulence factors was performed. agr dysfunction was assessed phenotypically and by RT–PCR quantification of RNAIII. Results Of 84 MSSA, 55 (65.5%) exhibited the RSV phenotype, comprising 13 clonal complexes. agr II polymorphism was more prevalent in RSV than non-RSV isolates (41.8% versus 17.2%, P = 0.023) and average levels of RNAIII gene expression were higher in RSV than non-RSV isolates (ΔCt 4.05 ± 3.29 versus 1.5 ± 2.11, P = 0.005), implying greater agr dysfunction in RSV MSSA. Conclusions We demonstrated a correlation between RSV phenotype in MSSA and reduced agr expression, particularly in association with the agr II genotype. These results may help to understand the role of agr dysfunction in the increased mortality in MSSA infections. [ABSTRACT FROM PUBLISHER]

Objectives: The objectives of the present study were to identify the species of enterococci isolated from nosocomial infections and to determine the antibiotic susceptibility pattern with reference to high-level aminoglycosides and vancomycin. Materials and Methods: Enterococci were isolated from various clinical samples collected from patients after 72 hours of hospitalization. Various species of Enterococcus were identified by standard methods. High-level aminoglycoside resistance and vancomycin susceptibility in enterococci were detected by disk-diffusion and agar-screen methods. Results: One hundred eighty enterococcal strains were isolated from various clinical samples. Various species of Enterococcus - Enterococcus fecalis 130 (72.22%), Enterococcus casseliflavus 24 (13.33%), Enterococcus fecium 17 (9.44%), Enterococcus durans 7 (3.89%) and Enterococcus dispar 2 (1.11%) - were isolated. The highest resistance to aminoglycoside was observed among E. fecium, followed by E. durans, E. fecalis and E. casseliflavus, both by disk-diffusion and agar-screen methods. The high-level aminoglycoside resistance (HLAR) was significantly (P<0.05) higher in E. fecium by agar-screen method. All enterococci showed minimum inhibitory concentration (MIC) of ⩽8 μg/mL to vancomycin. Sixteen (12.31%) E. fecalis and 3 (12.5%) E. fecium strains were intermediately resistant to vancomycin (MIC= 8 μg/mL), whereas other strains were susceptible to vancomycin. Conclusion: The occurrence of high-level aminoglycoside resistance in enterococcal isolates in our setup was high. Even though none of the enterococcal strains showed resistance to vancomycin, yet reduced susceptibility to vancomycin was noticed in our study. This would require routine testing of enterococcal isolates for HLAR and vancomycin susceptibility. Agar-screen method was found to be superior to disk-diffusion method in detecting resistant strains to aminoglycosides and vancomycin. [ABSTRACT FROM AUTHOR]

Objective: To investigate the prevalence of antibiotic resistance among Staphylococcus aureus isolated in Kuwaiti hospitals. Materials and Methods:S. aureus were isolated and identified following standard microbiological methods. Antibacterial susceptibility test was performed by disk diffusion and the measurement of minimum inhibitory concentration with E-test strips. Results: A total of 1,846 S. aureus isolates were analyzed from 13 hospitals between 1 March and 30 October 2005. They were isolated from 1,765 (95.6%) inpatients and 81 (4.4%) outpatients. Methicillin resistance was detected in 588 (32.0%) of the isolates. The methicillin-resistant S. aureus (MRSA) consisted of 461 (78%) multiresistant and 127 (22%) nonmultiresistant isolates. The nonmultiresistant MRSA consisted of epidemic MRSA-15 and community-associated MRSA. The community-associated MRSA was detected in all hospitals with MRSA, indicating its establishment in Kuwaiti hospitals. The proportion of isolates resistant to gentamicin, kanamycin, erythromycin, tetracycline, ciprofloxacin, fusidic acid and trimethoprim was higher among MRSA than methicillin-susceptible S. aureus (MSSA) isolates. Twenty-four and 22% of MRSA and MSSA isolates, respectively, expressed reduced susceptibility to vancomycin (minimum inhibitory concentration = 3–4 mg/l). Conclusion: The study revealed the presence of methicillin resistance in 32% of S. aureus isolated in Kuwaiti hospitals and revealed an increase in the number of MRSA and MSSA with reduced susceptibility to vancomycin. Copyright © 2007 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]