Detection of metallo-β-lactamases producing Acinetobacter baumannii using microbiological assay, disc synergy test and PCR.

Background: One leading factor responsible for resistance in Acinetobacter baumannii, an important opportunist in health care institutions globally, is the production of carbapenamases like metallo-β-lactamases (MBLs), which hydrolyze a variety of β-lactams including penicillin, cephalosporins and carbapenems. However, neither any standard guidelines are available nor any method has been found to be perfect for their detection. Various methods have shown discordant results, depending upon the employed methodology, β-lactamase substrate and MBL inhibitor used. This study aims to evaluate two phenotypic methods against PCR as gold standard among carbapenem resistant A. baumannii for identifying MBL producers. Materials and Methods: A total of 130 A. baumannii were screened for imipenem and meropenem resistance by Kirby-Bauer disc diffusion method. Phenotypic expression of MBL was detected by EDTA-imipenem-microbiological (EIM) assay and extended EDTA disc synergy (eEDS) test and presence of bla-IMP and bla-VIM was detected by PCR in all the carbapenem resistant isolates. Results: Of the 43 imipenem and/or meropenem resistant A. baumannii isolates, 4 (9.3%) were found to be MBL producers by EIM and 3 (6.97%) by eEDS. Only bla-VIM gene was detected in 7 (16.28%) by PCR. In addition EIM detected 14 (32.56%) carbapenem resistant non-metallo enzyme producers. Conclusion: Of the two MBL genes targeted, bla-VIM was only detected and that too in isolates resistant to both imipenem and meropenem. Further, EIM was useful in differentiating MBL from non-metalloenzymes producers.

Primary mediastinal hydatid cyst.

An unusual case of primary mediastinal echinococcosis in a young female presented with non-specific symptoms. On examination, she had signs of Horner's syndrome and mild superior vena cava compression. She was operated successfully. The final diagnosis could only be made on the operating table and confirmed by histopathology. Hydatid cyst in mediastinum is uncommon but because of surrounding vital structures and potential of its complete cure should be explored without delay.

Quantitation of proteinuria by use of single random spot urine collection.

Measurements of protein to creatinine ratios in single voided urine samples were compared with 24 hour urinary protein excretion for quantification of proteinuria in 20 healthy control and 30 patients of various renal diseases. The range of proteinuria in study group was 1.46-6.0 g/day and renal function was stable in all the cases. An excellent correlation was found between the results obtained by this method and those from the standard 24 hours urine collection method in healthy controls (r = 0.99) and in patients with renal disease (r = 0.98). In our study urinary protein-creatinine ratio in control group was less than 0.2 in all cases and in study group was more than 3.0 except in one. The results of the present study indicate that the random urine protein-creatinine ratio is highly reliable test for quantification of proteinuria in children and has obvious advantage in term of time, cost and patients convenience.