Phenotypic & molecular characterization of AmpC ß-lactamases among Escherichia coli, Klebsiella spp. & Enterobacter spp. from five Indian Medical Centers.

BACKGROUND & OBJECTIVES: AmpC ß-lactamases which are often plasmid mediated hydrolyze all ß-lactam antibiotics except cefepime and carbapenems. We evaluated the presence of AmpC ß-lactamases among Enterobacteriaceae strains recovered prospectively from patients at five Indian tertiary care centres. METHODS: The study included 909 consecutive Gram-negative isolates recovered from clinically significant specimens during June 2007 - May 2008 as part of an ICMR-ESBL study. Among the study isolates, 312 were found to be cefoxitin resistant by disc diffusion test (DDT). Minimum inhibitory concentration (MIC) determination by E test was done against amikacin, levofloxacin, impinem, meropenem, ertapenem, tigecycline and piperacillin-tazobactam. Combined DDT using phenyl boronic acid as inhibitor with cefoxitin was used for phenotypic confirmation of AmpC phenotype. The common Amp C genotypes ACC, FOX, MOX, DHA, CIT and EBC were detected by multiplex PCR. RESULTS: Plasmid mediated Amp C phenotype was confirmed in 114 of the 312 (36.5%) cefoxitin resistant isolates with 255 (81.7%) showing multidrug resistance. Susceptibility to tigecycline was highest (99%) followed by imipenem, meropenem (97%), ertapenem (89%), amikacin (85%), and piperacillin-tazobactam (74.6%). Levofloxacin resistance was 82 per cent. ESBL co carriage was observed among 92 per cent of Amp C producers. Among 114 Amp C producers, 48 could be assigned a genotype, this included CIT- FOX (n = 25), EBC (n = 10), FOX (n = 4), CIT (n = 3), EBC-ACC (n = 2) and one each of DHA, EBC-DHA, FOX -DHA and FOX-EBC-DHA. INTERPRETATION & CONCLUSIONS: Overall, AmpC phenotypes were found in 12.5 per cent isolates, multidrug resistance and ESBL co-carriage among them was high suggesting plasmid mediated spread. The study results have implications in rational antimicrobial therapy and continued surveillance of mechanisms of resistance among nosocomial pathogens.

Thyrotoxicosis presenting as acute bulbar palsy.

Myopathy chiefly affecting the proximal muscles of the limbs is frequently seen in hyperthyroidism. But isolated acute bulbar palsy without skeletal muscle involvement is rare in thyrotoxicosis. We report the case of a 52 year old man who presented with severe dysphagia, dysphonia and bouts of aspiration. Laboratory testing revealed an underlying Graves' thyrotoxicosis. His symptoms recovered dramatically within 6 weeks with treatment of hyperthyroidism. This case is reported to emphasize that thyrotoxicosis should be considered in the differential diagnosis of dysphagia of obscure etiology.