Short-term toxicity test: monitoring Klebsiella oxytoca bacterium respiration using a flow injection analysis/conductometric system

Abstract

Neste estudo, foi desenvolvido um teste de toxicidade rápido, utilizando-se a bactéria Klebsiella oxytoca como organismo-teste. Ensaios com Escherichia coli foram usados como referência. A inibição do crescimento bacteriano foi avaliada por um sistema de análise por injeção em fluxo (FIA) com detecção condutométrica do CO 2 produzido durante o processo respiratório. Os resultados foram expressos em termos de CE 50 (concentração efetiva). A bactéria K. oxytoca foi mais resistente que a E. coli. A ordem de sensibilidade da K. oxytoca em relação aos metais foi Hg 2+ > Cd 2+ > Cu 2+ e para E. coli, Hg 2+ > Cu 2+ > Cd 2+ . Para o detergente Laborhex 2 (princípio ativo: digluconato de clorexidina), o CE 50 foi 1,55 ± 0,32 mg L -1 e 0,32 ± 0,10 mg L -1 para K. oxytoca e E. coli, respectivamente, enquanto que para o detergente Riodeine Degermant (princípio ativo: iodeto de polivinilpirrolidona-PVP-I), ambas as bactérias apresentaram sensibilidades bem semelhantes, 11,0 ± 1,7 mg L -1 e 12,0 ± 2,0 mg L -1 , respectivamente.In this study, the Klebsiella oxytoca bacterium was used as a test organism in short-term toxicity evaluations, and Escherichia coli was used as reference. The inhibition of bacterial growth was quantified by flow injection analysis (FIA) via conductometric measurements of the CO 2 produced during respiration. The results were expressed as effective concentration (EC 50 ) values. K. oxytoca was more resistant than E. coli in respect to growth inhibition. The metal sensitivity order for K. oxytoca was found to be Hg 2+ > Cd 2+ > Cu 2+ and Hg 2+ > Cu 2+ > Cd 2+ for E. coli. The sensitivity to the Laborhex 2 detergent (active ingredient: chlorhexidine digluconate) was 1.55 ± 0.32 mg L -1 and 0.32 ± 0.10 mg L -1 for K. oxytoca and E. coli, respectively. The bacteria showed comparable sensitivities to the Riodeine Degermant detergent (active ingredient: polyvinyl pyrrolidone-iodine-PVP-I), of 11.0 ± 1.7 mg L -1 and 12.0 ± 2.0 mg L -1 , for K. oxytoca and E. coli, respectively. Keywords: short-term toxicity test, Klebsiella oxytoca, Escherichia coli, heavy metals, hospital detergents IntroductionThe toxicity of a compound is usually defined in terms of the biological response of a particular organism to a toxin, such that toxicity reflects the harmful effects on an organism upon exposure to a given concentration of a chemical agent for a given period of time. In a toxicity test, organisms are used to identify the minimum concentration of a chemical agent that results in disturbance, which determines the level at which exposure becomes harmful.The tests may be used to evaluate the toxicity of chemical products available in the market, to appraise the quality of surface waters, to monitor and verify the efficiency of systems that treat wastewaters and effluents, 1,2 to evaluate the effects of industrial effluent discharge into surface waters or in wastewater treatment plants, 3,4 or to evaluate the deleterious actions of industrial products. 5 The tests can also evaluate the sensitivity of an organism to a subs...

Lethal and sub lethal effects of the biocide chlorhexidine on aquatic organisms

“…These results agree with those of previous studies performed with chlorhexidine compounds that also showed higher sensitivity of D. magna when compared to bacteria and fish (Table 3). Chlorhexidine digluconate toxicity to V. fischeri is similar to the toxicity to Klebsiella oxytoca (EC50 of 1,550 lg/l) but lower than the toxicity to Escherichia coli (EC50 of 320 lg/l) (Guimarães et al 2012). ChD was highly toxic to the algae P. subcapitata, with values as low as 31.1 lg/l causing a 20 % reduction in algae growth rate (i.e.…”

“…ChD was reported to be toxic to bacteria (Guimarães et al 2012). Moreover, two studies reported bioaccumulation of ChD on river microbial biofilms and a significant effect of ChD on the structure of microorganism communities (increase in the proportion of archaea, bacteria and cyanobacteria when compared to algae) at doses of 10 lg/1 (Lawrence et al 2008;Dynes et al 2006).…”

Synergistic effect of microwave irradiation and conjugated polymeric catalyst in the facile degradation of dyes

“…Acute toxicity determinations were carried out by measuring the respiration inhibition in Escherichia coli cultures, by using FIAconductometric methodology which was composed of a peristaltic pump, the samples and standards injector, a diffusion cell, a conductivity cell, reagent delivery tubes, ion exchange resins, a conductivity meter, a recorder, and a water bath. 21 The sterilized culture media for E.coli was composed of K 2 HPO 4 (7.0 g), KH 2 PO 4 (3.0 g), sodium citrate (0.5 g), ammonium sulphate (1.0 g), magnesium sulphate (0.2 g) and glucose (20 g) (nal volume: 1 L with deionized water; pH: 7.2). The culture medium was inoculated with the bacteria and le in an oven at 37 C until the bacterial suspension became cloudy.…”

“…where C is the nal minus initial CO 2 concentration in the control culture and T is the nal minus initial CO 2 concentration in the test cultures. 21…”

Flow injection chemiluminescence determination of ethion and computational investigation of the adsorption process on molecularly imprinted polymerized high internal phase emulsion

“…Various detection techniques have been proposed for FIA methods, including electrochemical methods such as potentiometry, [ 5 ] amperometry [ 6 ] and conductometry, [ 7 ] and spectrophotometric, [ 8 ] fluorometric, [ 9 ] and chemiluminescence (CL) methods. [ 10,11 ]…”