Medically important enterococcus species from isolates of urinary tract infection with their antimicrobial susceptibility

Background: Enterococcus are primarily opportunistic pathogens causing infections in immunocompromised patients with some underlying medical disorder. Recently, enterococci have become one of the most common causes of hospital acquired infections, leading to high mortality and morbdity. Studies indicate that enterococci are the second most common cause of urinary tract infections (UTI) and third most common cause of bacteremia and nosocomial infections.
Materials and methods: The study was performed over a period of two years from January 2016 to December 2017. Urine samples collected in appropriate sterile manner were screened for pus cells and bacteria by routine microscopic examination. This was followed by plating on Mac-conkey’s agar and Blood agar. Inoculated plates were incubated overnight at 37⁰c. Isolated Enterococcus strains were identified with Matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) to confirm the speciation. Antibiotic susceptibility was performed by Vitek compact 2 as per CLSI guidelines establishing MIC (Minimum Inhibitory Concentration).
Results: Of the total 1113 isolates of Enterococcus species from urinary tract, Enterococcus faecalis (77%) was found to be the most common species followed by Enterococcus faecium (21%). Of the 860 strains of Enterococcus faecalis, 30 strains were resistant to vancomycin (VRE) with MIC values more than 32. Of the 230 isolates of Enterococcus faecium thirty two strains were resistant to vancomycin (VRE). Thirteen isolates of Enterococcus avium and 3 isolates of Enterococcus hirae were susceptible to vancomycin and teicoplanin. In general Enterococcus faecium was found to be more resistant to antimicrobials with higher MIC values.
Discussion: Enterococcus faecalis is the most prevalent isolate being associated with 80-90% of human Enterococcal infection. Enterococcus faecium ranks second and is isolated from 10-15% of infections. Other species are infrequently isolated from clinical specimens are E. gallinarum, E. avium, E. casseliflavus, E. flavescens, and E. hirae. Enterococci are highly notorious for their drug resistance pattern. In vitro, Enterococci have penicillin MICs 10 to 100 fold higher than that of Streptococci which are uniformly sensitive to penicillin and β lactam group of drugs. Increased level of antimicrobial resistance by different isolates of Enterococcus possesses a threat to nosocomial set up as it tends to limit treatment options.
Conclusion: The identification of and speciation of Enterococcus is of utmost importance. Recently, enterococci have become one of the most common nosocomial pathogens, giving a high mortality and morbidity. Overall, greater understanding of the ability of Enterococcus species to survive stresses and especially of increasing antibiotic resistance, is needed in order to fully appreciate the complexity of Enterococcus species in causing human disease.