Carbapenem resistance and phenotypic detection of carbapenemases in clinical isolates of acinetobacter baumannii.

Background and Objectives: Multidrug-resistant Acinetobacter baumannii (MDR-Ab) reported worldwide has become one of the most difficult nosocomially acquired Gram-negative pathogens to control and treat. The clinical utility of carbapenems is under threat with the emergence of acquired carbapenemases, particularly Ambler class B metallo-lactamases (MBL). Because of the global increase in the occurrence and dissemination of MBLs, early detection is critical. This study was undertaken to detect resistance to carbapenems in clinical isolates of A. baumannii from hospitalized patients by both disk-diffusion and minimum inhibitory concentration (MIC) methods and to assess the rate of carbapenemase and MBL production among the isolates. Materials and Methods : A. baumannii were identified from various clinical samples and antibiotic susceptibility profile was determined by the standard disk-diffusion method. Meropenem-resistant strains were tested further by agar dilution MIC for meropenem. Resistant isolates were screened for carbapenemase production by the modified Hodge test and positive isolates were further checked for metallo-β-lacatmase production by the EDTA disk synergy test. Results : 42 isolates (31.81%) showed resistance to meropenem by the disk diffusion method. 47.6% were carbapenemase positive by the modified Hodge test and 19% were MBL producers phenotypically by the EDTA disc synergy test (EDS). These meropenem-resistant isolates were resistant to most of the other antibiotics tested. These 42 isolates were recovered mostly from patients admitted to intensive care units. Four isolates of the A. baumannii complex were pan drug resistant and showed resistance to even tigecycline and polymyxin B. Conclusion : Carbapenem resistance has been increasingly reported, necessitating their detection. This study reports simple, carbapenemase, and MBL detection method that can be easily incorporated into the daily routine of a clinical laboratory.

Study of suspected plague cases for isolation and identification of Yersinia pestis.

A total of 62 suspected patients of plague were investigated for evidence of Yersinia pestis, by blood culture, lymph node aspirate culture, sputum culture, animal inoculation and serology for f1 antibodies against f1 antigen of Yersinia pestis. None of the samples was positive by direct smear examination and culture for Yersinia pestis, as well as for serology. The non positivity of the cultures is discussed.

Utilization of used human immunodeficiency virus ELISA microplates & surplus reagents for HIV antibody testing.

Used non-competitive enzyme-linked immunosorbent assay (ELISA) microplates were washed and reused to test samples and positive and negative controls, utilising the surplus reagents provided with the kit, which otherwise would have been discarded as useless after the entire 960 test kit had been utilized. These surplus reagents could be used for additional 220 tests over and above the recommended 960 tests per kit. A total of 839 unknown serum samples, 54 negative controls and 36 positive controls were tested using both washed and fresh (new) ELISA plates simultaneously. The optical density (OD) value of the control sera was within the prescribed limits in both the methods and 15 samples were found to be positive for HIV antibodies by the fresh plates whereas the washed plates showed 18 samples to be positive for HIV antibodies. None of the samples positive by fresh plates were negative by washed plates.

Slime producing Staphylococci from clinical specimens - a simple diagnostic test.

Coagulase negative Staphylococci are now being increasingly recognised as pathogens. Some strains produce a viscous extracellular material or slime. These strains are uniquely adapted for adherence to even smooth surfaces. Present study is a preliminary report of 101 isolates of coagulase negative Staphylococci from different clinical specimens. Forty three of these 101 isolates (42.5%) were slime producers. The percentage of slime producing Staphylococci ranged from 20% in peritoneal fluid to 66.6% in Cerebrospinal fluid. The test for slime production may have an important application in deciding the pathogenecity of the strains of coagulase negative Staphylococci and should be done routinely in a diagnostic laboratory.