Inoculum size-insensitive susceptibility determination of urine sample based on in-situ measurement of inducible enzyme activity after 20 min of antibiotic exposure

BACKGROUND

The empirical antibiotic therapies for bacterial infections cause the emergence and propagation of multi-drug resistant bacteria, which not only impair the effectiveness of existing antibiotics but also raise healthcare costs. To reduce the empirical treatments, rapid antimicrobial susceptibility testing (AST) of causative microorganisms in clinical samples should be conducted for prescribing evidence-based antibiotics. However, most of culture-based ASTs suffer from inoculum effect and lack differentiation of target pathogen and commensals, hampering their adoption for evidence-based antibiotic prescription. Therefore, rapid ASTs which can specifically determine pathogens' susceptibilities, regardless of the bacterial load in clinical samples, are in urgent need.

RESULTS

We present a pathogen-specific and inoculum size-insensitive AST to achieve the reliable susceptibility determination on Escherichia coli (E. coli) in urine samples. The developed AST is featured with an 1 h sample-to-result workflow in a filter, termed on-filter AST. The AST results can be obtained by using an inducible enzymatic assay to in-situ measure the cell response of E. coli collected from urine after 20 min of antibiotic exposure. The calculated detection limit of our AST (1.95 × 104 CFU/mL) is much lower than the diagnosis threshold of urinary tract infections. The specific expression of the inducible enzyme enables on-filter AST to correctly profile the susceptibilities of target pathogen to multi-type antibiotics without the interference from commensals. We performed the on-filter AST on 1 mL urine samples with bacterial loads varying from 105 CFU/mL to 107 CFU/mL and compared the results to that of standard method, demonstrating its insensitivity to inoculum size.

SIGNIFICANCE

The developed AST is demonstrated to be of high sensitivity, specificity, and insensitive to inoculum size. With further developments for additional bacteria and clinical validation, on-filter AST is promising as a rapid and reliable surrogate of culture-based AST to promote the evidence-based prescription at the first visit and minimize the emergency of new multi-drug resistant microorganisms.

A comprehensive review on tannase: Microbes associated production of tannase exploiting tannin rich agro-industrial wastes with special reference to its potential environmental and industrial applications

Microorganisms have been used for the production of various enzymes, including inducible tannase for various industrial and environmental applications. Tannases have lot of potential to convert hydrolysable tannins to gallic acid, which is one of the important industrial and therapeutic significant molecules whose demand is over 10000 tons per year. Tannins invariably occur in angiosperms, gymnosperms and pteridophytes, and predominantly present in various parts of plants such as, leaves, roots, bark and fruit. Furthermore, tannery effluents are frequently loaded with significant levels of tannic acid. Tannase can be effectively used to decrease tannin load in the toxic tannery effluent thus providing the opportunity to minimize the operational cost. Over the past three decades, tannase from microbial sources has been proposed for the degradation of natural tannins. The availability of various agro-industrial residues paves a way for maximum utilization of tannase production for the degradation of tannin and eventually the production of gallic acid. In this review, an illustrative and comprehensive account on tannase from microbial source for current day applications is presented. The present review emphasises on up-to-date microbial sources of tannases, biochemical properties, optimization of tannase production in solid state and submerged fermentation and its industrial and environmental applications.