Species distribution, antibiotic susceptibility and clinical characteristics in Enterococcal bacteremia; experience from South India

Introduction

While the incidence of Vancomycin-resistant Enterococci (VRE) infections in India remains lower than in other countries, recent reports indicate an upward trend. This study investigates the clinical characteristics and antibiotic susceptibility profile associated with Enterococcus bacteremia.

Methods

We conducted a retrospective analysis of patient records with Enterococcal bacteremia from January 2016 to December 2022 at our tertiary care center in Kerala, South India. For the detection of bacterial growth, BacT/AlLERT 3D instrument was used. Identification and antibiotic susceptibility were done by the VITEK-2 system.

Results

During the study period, we identified 214 unique Enterococcus isolates in blood cultures. The median age of patients was 62 years (interquartile range: 51-71 years), with males constituting 66% of the cases. The most prevalent comorbidity was diabetes, affecting 51% of patients (n=109), followed by chronic kidney disease in 27% (n=58), and chronic liver disease in 22% (n=48). Malignancies were present in 16% of patients (n=34), and 17% (n=36) experienced immunosuppression from either disease or medication. The primary sources of infection were genitourinary (17%, n=36) and intestinal (16%, n=35) tracts, with infective endocarditis (IE) observed in 7% (n=15).

E. faecalis was the predominant species, accounting for 50% of cases (n=107), followed by E. faecium at 39.5% (n=85). Other species included E. gallinarum (n=6), E. raffinose (n=4), E. durans (n=2), E. avium (n=2), and E. casseliflavus (n=1). Species identification was indeterminate in 6 isolates.

Among the E. faecalis isolates, 100% susceptibility was noted for vancomycin and linezolid, 95% for teicoplanin, 88% for penicillin, 86% for ampicillin, and 61% for gentamicin. For E. faecium, susceptibility rates were 95% for vancomycin and linezolid, 88% for teicoplanin, 36% for gentamicin, and only 11% for penicillin and ampicillin. Daptomycin was tested in 28 isolates, with 1 being resistant and 2 showing intermediate susceptibility. Among the 2 isolates that exhibited vancomycin and linezolid resistance, daptomycin remained susceptible.

Overall, 59% of patients improved, 30% expired, and 11% were discharged at their request and could not be followed up. Among the 95 patients with E. faecalis bacteremia, 67% survived, while among the 76 patients with E. faecium bacteremia, 64% survived. There was no statistically significant correlation between comorbidities, infection source, species, and clinical outcomes. Among those diagnosed with vancomycin-sensitive Enterococcus, almost one-third (29%) succumbed. Among the 4 patients diagnosed with VRE, 3 did not survive.

Conclusion

Enterococcal bacteremia is associated with significant mortality, with approximately one-third of patients succumbing to the illness. However, vancomycin resistance remains relatively low even in Enterococcus faecium isolates.