Urinary tract infection by coagulase negative staphylococci and staphylococcus aureus with special reference to mrsa

Background: Urinary tract infection (UTI) is a frequent cause of morbidity both in the community and in the hospital setting. It is one of those infections where empirical antibiotics are frequently used. S. aureus is an opportunistic pathogen affecting both immune competent and immunocompromised individuals. Methicillin-resistant S. aureus (MRSA) is widespread and is increasingly seen in community health care units. MRSA infections occur most frequently among persons in hospitals and healthcare facilities such as nursing homes and dialysis centers, who have weakened immune systems. MRSA strains with decreased susceptibility to vancomycinand strains fully resistant to vancomycin (MIC ≥ 16 μg/ml) have been reported.
Materials and Methods: The study was performed from January 2017 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 MacConkey’s agar and Blood agar. Inoculated plates were incubated overnight at 37 0C. Isolated catalase positive Staphylococcus species 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 158 isolates of S. aureus, 41 (25.94%) were MRSA. Of the 58 isolates of S. saprophyticus, 23 (39.65%) were methicillin resistant (MRCONS). Cefoxitin was used as a surrogate marker for methicillin and oxacillin resistance.Of the 158 isolates of S. aureus, 4 strains were resistant to vancomycin (VRSA) with MIC values more than 32 µg/ml and one strain was intermediate with MIC of 4 µg/ml. Of the 58 isolates of S. saprophyticus, one strain was resistant to vancomycin with MIC 32 µg/ml. The isolates of Staphylococcus aureus which were intermediate to vancomycin (VISA) and resistant to vancomycin (VRSA) were re-tested with vancomycin E (Biomerieux-Etest strips) to compare the results with automated susceptibility testing.
Discussion: The worldwide incidence of symptomatic urinary tract infection is estimated to be around 150 million cases annually. Urinary catheterization is one of the major risk factor for development of UTI in hospitalized patients. A UTI in the presence of a urinary catheter warrants removal or changing of the catheter. Most of the MRSA isolates (N=41) in our study were from catheterized patients. Since S. aureus is known for multidrug resistance, knowledge of local antimicrobial susceptibility pattern is important in an order to choose empirical therapy. In the present study, we have noted highest drug resistance rates among Fluoroquinolones with ciprofloxacin (87.34%) and levofloxacin (70.88%) which are one of the empirical drugs in treatment of uncomplicated UTI.
Conclusion: MRSA is one of the most prevalent nosocomial pathogens worldwide. MRSA strains which are multidrug resistant (MDR) leaves very few options for treating UTI. Appropriate therapy should be based on the local antimicrobial susceptibility pattern for which periodic review of the antibiogram is essential. Rapid detection of a staphylococcal isolate especially MRSA may help in timely initiation of an appropriate therapy. Drug resistance is a huge concern today and therefore, awareness about the rationale of judicious antibiotic use cannot be overemphasized.