Molecular Characterization of Methicillin-Resistant Staphylococcus aureus Causing Fatal Purulent Pericarditis
A 78-year-old male who was a known case of squamous cell carcinoma of buccal mucosa, which was excised with cervical lymph node dissection two years ago along with systemic hypertension and renal failure (Urea 179 mg/dl, Creatinine 5.28 mg/dl) was hospitalized with complaints of fever since 10 days and dyspnoea on exertion class III of two days duration. A chest X-ray [Figures and ] showed massive pericardial effusion and an electrocardiogram (ECG) [] revealed low voltage waves, ST elevation, atrial fibrillation and a fast ventricular rate. The white cell count was 21 K/μl with 88% neutrophils and liver enzymes were also elevated (SGOT 103 IU/L, SGPT 80 IU/L). The patient developed cardiac tamponade. Emergency pericardiocentesis was done and 800ml of fluid was drained and a pigtail catheter was introduced through a subxiphoid incision and placed under fluoroscopic guidance in the pericardial cavity. Pericardial fluid analysis showed ADA 15.2 U/L, glucose 97.8 g/dl, protein 5.84 g/dl.\nBlood and pericardial fluid cultures grew Gram positive cocci which were identified as MRSA with the Vitek 2 (BioMerieux, Inc., Durham, NC). Both the MRSA isolates (from blood and pericardial fluid) were resistant to multiple classes of antibiotics namely oxacillin, penicillin, trimethoprim-sulfamethoxazole, gentamicin and ciprofloxacin while susceptible to vancomycin, clindamycin, tertracyline, linezolid, quinupristin/dalfopristin, nitrofurantoin, and rifampicin as determined by Vitek 2 system. Vancomycin (1 μg/ml) and daptomycin (0.94 μg/ml) susceptibility was confirmed by Etest (BioMerieux, Inc., Durham, NC). The isolate was intermediately sensitive to erythromycin (1 μg/ml) and a D-test for inducible clindamycin resistance was found to be negative. The MRSA isolate from blood and pericardial fluid were identical and identification was confirmed by amplifying the 16S rDNA gene of the genus Staphylococcus and sau gene specific for S. aureus.[] A multiplex polymerase chain reaction (PCR) was done to simultaneously detect genes responsible for resistance to four classes of antibiotics and the isolate was positive for aac A-aph D, erm (C) and mecA encoding for resistance to aminoglycoside, erythromycin and oxacillin respectively.[] The organism was susceptible to tetracycline and, therefore, tetK and tetM genes were not amplified.[] All the primers were synthesized at Sigma Genosys, India.\nThe patient who was empirically put on piperacillin/tazobactum was shifted to vancomycin when cultures identified the isolate as MRSA on the third day. His renal function worsened and he was put on hemodialysis and mechanical ventilatory support. Subsequently he developed septic shock and metabolic acidosis and expired on the fourth day of admission due to heart failure.