Reliability of Kirby-Bauer disk diffusion method for detecting meropenem resistance among non-fermenting gram-negative bacilli.

Background: Meropenem is empirically used as a last resort for the treatment of infections by non-fermenting gram-negative bacilli (NFGNB). Minimum inhibitory concentration (MIC) determined using agar or broth dilution methods is widely used for testing meropenem resistance. However, it is not possible in resource-poor settings. Aim: A prospective study was performed to evaluate the reliability of Kirby-Bauer disk diffusion (KBDD) method for detecting meropenem resistance among NFGNB. Materials and Methods: A total of 146 NFGNB consisting of 56 Acinetobacter baumannii, 24 Acinetobacter lwoffii, 48 Pseudomonas aeruginosa and 18 Pseudomonas spp. were included in the study. All the isolates were tested simultaneously by both KBDD method and agar dilution method. Results: Very major errors were not observed with A. baumannii, A. lwoffii and P. aeruginosa, while other Pseudomonas spp. showed a very major error rate of about 5.6%. The major error rates observed with A. baumannii, A. lwoffii, P. aeruginosa and Pseudomonas spp. were 1.8%, 0%, 2.1% and 28.6%, respectively. All the isolates showed a good correlation between zone diameters (KBDD method) and MICs (agar dilution method). The sensitivity and specificity of KBDD method for detecting meropenem resistance was above 90% for all the NFGNB except Pseudomonas spp. Conclusions: The KBDD method can be reliably used for routine testing of meropenem resistance in A. baumannii, A. lwoffii and P. aeruginosa. However, further studies are needed before employing this technique for detecting meropenem resistance in Pseudomonas spp.

Role of bone marrow trephine biopsy in the diagnosis of marrow involvement in Hodgkin's disease.

Bone marrow involvement in Hodgkin's disease alters the stage and hence the prognosis and treatment modality. Seventy-six patients of biopsy proven Hodgkin's disease in whom a bone marrow aspiration and biopsy were done simultaneously at the time of diagnosis were included in the study. Bone marrow involvement was seen in 14 (18%) cases. All 14 cases were diagnosed on biopsy. Only one aspirate was suspicious of involvement. Rest was either diluted (28%) or was normal (64%). Eleven patients were upstaged from stage I, II and III to stage IV. All patients had cytopenia of one or more cell line. Increased fibrosis, necrosis and a polymorphic cellular infiltrate were associated findings in the marrow. We wish to highlight the importance of bone marrow trephine biopsy over aspirate in staging even clinically early stage Hodgkin's disease.