Significance of urinary tract infection by enterobacter, citrobcater and serratia species and their antimicrobial susceptibility profile with special refernce to intrinsic resistance

Background: Urinary tract infections (UTIs) are one of the most common bacterial infections affecting humans. Despite advances in antimicrobial therapy, the mortality and morbidity associated with UTIs remain significantly high. This study highlights the significance of Enterobacter, Citrobacter and Serratia species in causing urinary tract infection. The knowledge of knowing intrinsic drug resistance of these organisms is important particularly in the management. As most of these isolates are intrinsically resistant to commonly used antimicrobial agents, antimicrobial susceptibility plays a pivotal role in patient care.
Materials and Methods: This is a retrospective analysis from January 2016 to December 2017. Urine samples collected in appropriate sterile manner were screened for polymorphonuclear leucocytes and bacteria by routine microscopic examination. Isolated strains of Enterobacter, Citrobacter and Serratia in significant count from MacConkey’s agar were identified with Matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS). Antibiotic susceptibility was performed by Vitek CompactTM 2 (Biomeuriux, France) as per CLSI standards establishing MIC (Minimum Inhibitory Concentration).
Results: Of the 402 strains of Enterobacter, 334(83.08%) were sensitive, 9(2.23%) strains shown intermediate susceptibility and 59(14.67%) strains found resistant to meropenem. Meropenem has shown good in-vitro susceptibility as compared with imipenem. Of the 238 species of Citrobacter, 227(95.37%) were susceptible to Nitrofurantoin, seven (2.94%) strains wereresistant and four (1.68%) strains shown intermediate susceptibility. Of the 402 Enterobacterspecies, 133(33.08%) strains were sensitive, 73(18.15%) strains were resistant and 196(48.75%) strains shown intermediate susceptibility. All the 38 strains of Serratiamarcescens shown intrinsic resistance to Nitrofurantoin. Of the 238 strains of Citrobacter species, 220(92.43%) were susceptible and 18(7.57%) were resistant with ciprofloxacin. Of the 402 Enterobcater species, 288(71.64%) were susceptible, 15(3.73%) strains shown intermediate suceptibility and 99(24.63%) were resistant. Of the 38 strains of Serratia marcescens, 34(89.47%) were susceptible and only four strains were resistant.
Discussion: The magnitude of health care associated and community acquired urinary tract infections have increased over time considering its potential to cause MDR infections. UTIs caused by E. aerogenes, E. cloacae complex, Serraita marcescens, Citrobacter koseri and C. freundii are increasing both in hospital and in general community. It is of utmost importance of performing antimicrobial susceptibility testing for these isolates as they are known to be intrinsically resistant to commonly used antimicrobials. Extensive use ofantimicrobial agents as empirical therapy without evidence of culture susceptibility pattern and local antibiogram has resulted in development of drug resistance including multidrug resistant (MDR) organisms.
Conclusion: E. aerogenes, E. cloacae complex, Serraita marcescens, Citrobacter koseri and C. freundii are now recognised to be clinically important pathogens causing both complicated and uncomplicated urinary tract infections. Early empirical treatment with fluoroquinolones, penicillins and cephalosporins in UTI should be carefully considered. Drugs like cotrimoxazole and nitrofurantoin should be considered as an alternative agent’s for treatment of urinary tract infections based on susceptibility pattern and local epidemiological data.