Contamination Of Water Systems Research Articles

Implementation of a Legionella Ordinance for Multifamily Housing, Garland, Texas.

Context:The incidence of legionellosis has sharply increased in the United States as a result of contaminated water systems. Jurisdictions across the country are considering whether to develop and implement regulations to protect individuals against Legionnaires' disease with its associated high morbidity and mortality.Objective:This article sheds light on the implementation and effectiveness of a 2005 citywide Legionella testing mandate of multifamily housing cooling towers in Garland, Texas. This ordinance has been in place for more than 10 years and represents the first of its kind in the United States to mandate routine testing of cooling towers for Legionella in multifamily housing.Design, Setting, and Population:We utilized a mix of both qualitative and quantitative methods to explore the development, adoption, and implementation of the ordinance. Phone interviews were conducted with individuals from the City of Garland Health Department and apartment managers. Quantitative data included public health surveillance data on legionellosis.Main Outcome Measures:Barriers and facilitators of implementation, number and percentage of cooling towers from multifamily housing units that tested positive for Legionella by year, and number of legionellosis cases by year in Garland, Texas.Results:Study outcomes highlight key themes that facilitated the successful implementation of the Legionella testing mandate, including the importance of timing, leadership support, stakeholder engagement, and education and outreach. The number of contaminated cooling towers was reduced over time.Conclusion:Mandatory monitoring for legionella in a local jurisdiction may result in reduced risk of legionellosis from cooling towers through raising awareness and education of building owners and managers about the need to prevent, detect, and remediate legionella contamination in their building water systems. Garland, Texas, broke new ground in the United States in moving toward primary prevention of legionellosis. The ordinance may be useful both in serving to educate and increase awareness about the need for Legionella prevention and to monitor effectiveness of maintenance procedures.

Electrochemical removal of microalgae with an integrated electrolysis-microbial fuel cell closed-loop system

Uncontrolled algal growth in water systems causes a number of serious issues that range from unpleasant odours and tastes to eutrophication. In this work, we propose for the first time to integrate an electrolysis process with the microbial fuel cell (MFC) technology as a sustainable way to treat algal contamination in water systems. Removal of chlorophyll-a by electrolysis was investigated in a fixed bed electrochemical reactor. The effect that operative parameters, such as current density and hydrodynamics, have on the process was analysed by using Chlorella vulgaris as a model of microalgae. Based on these results, a combined closed-loop system was developed in which the electrolysis unit was coupled with a cascade of miniature single chambered air-cathode MFCs. The electrolysis of C. vulgaris was performed under an applied current density of 25 A m−2 and for Reynolds equal to 13. The treated water was fed into a cascade of MFCs for further treatment and energy generation. The effect of the electrode surface area and of the number of MFCs in the cascade on both algae removal efficiency and power output was investigated. It resulted that the greater the active area of the electrodes in the MFCs, and the larger the number of fuel cells, the better the performance of the stack. The integrated system led to a 20% of reduction on the electrical energy requirement of the electrochemical reactor, giving the best results when the electrode surface area of the MFCs in the cascade was 0.32 cm2. Our approach provides a sustainable alternative to current algal removal systems that not only is chemical-free but also aims to be energy-neutral, thus reducing the large amount of energy that current water treatments require.

A micrometer-sized europium(iii)-organic framework for selective sensing of the Cr2O72- anion and picric acid in water systems.

A micrometer-sized europium(iii)-organic framework with asymmetric binuclear metal subunits extended by 4,5-dichlorophthalaten (DCPA), [Eu2(H2O)(DCPA)3]n, was easily obtained using a reverse microemulsion method. The framework exhibits good dispersibility, excellent thermal and environmental stability and easy regeneration ability. More importantly, the complex displays strong red emission and can selectively and sensitively detect both inorganic Cr2O72- anions (Ksv = 8.7 × 103 M-1) and organic picric acid contaminants (Ksv = 1.07 × 104 M-1) in water systems through fluorescence quenching. A luminescent film of 1 was further prepared and successfully used to detect the Cr2O72- anion in an aqueous system. These interesting results indicate that the well-dispersed europium(iii)-organic framework can serve as a promising dual-responsive luminescent sensor for environmental pollutant monitoring.

Medicaid Politics and Policy

Medicaid Politics and Policy

Impact of new water systems on healthcare-associated colonization or infection with Pseudomonas aeruginosa.

Aim: We aimed to study the impact of new water systems, which were less contaminated with P. aeruginosa, on the incidence of healthcare-associated P. aeruginosa cases (colonizations or infections) in care units that moved to a different building between 2005 and 2014. Methods: Generalized Estimated Equations were used to compare the incidence of P. aeruginosa healthcare-associated cases according to the building. Results: Twenty-nine units moved during the study period and 2,759 cases occurred in these units. No difference was observed when the new building was compared with older buildings overall.Conclusion: Our results did not support our hypothesis of a positive association between water system contamination and the incidence of healthcare-associated P. aeruginosa cases. These results must be confirmed by linking results of water samples and patients’ data.

Investigating the removal of methyl tertiary butyl ether (MTBE) from water using raw and modified fly ash waste materials

Classical techniques for remediation of methyl tertiary butyl ether (MTBE) from contaminated water sources are characterized by inherent limitations due to its unique physical and chemical characteristics, making further remediation researches promising. Fly ash (FA), which is a waste material derived from the combustion of coal or heavy liquid fuel has been reported to show favorable adsorption results with selected metals, dyes, and some organics in aqueous solution. In this study, raw FA, acid-treated FA, and metal oxide (silver, iron, and aluminum) impregnated FA were assessed on a bench scale, for MTBE adsorption in contaminated water system and benchmarked against activated carbon (AC). Results showed that only silver oxide (Ag2O) impregnated FA achieved ~24% removal of MTBE from aqueous solution, while the other tested adsorbent materials achieved <10%. MTBE optimum adsorption was attained after 120 min of contact, and 0.5 g/L dosage of adsorbent. Conversely, silver oxide impregnation of AC brought about a drop in its MTBE removal efficiency from an optimum efficiency of 71 to 53%. Also, the Langmuir isotherm model best represented the MTBE adsorption behavior of both the Ag2O-impregnated FA and AC, having R2 of 88.75–89.92%, respectively.

Rapid investigation of cases and clusters of Legionnaires' disease in England and Wales using direct molecular typing

Legionella pneumophila is the leading cause of Legionnaires' disease, a severe pneumonia that can occur as sporadic cases or point-source outbreaks affecting multiple patients. The infection is acquired by inhalation of aerosols from contaminated water systems. In order to identify the probable source and prevent further cases, clinical and environmental isolates are compared using phenotypic and genotypic methods. Typically up to 10 days are required to isolate L. pneumophila prior to the application of standard typing protocols. A rapid protocol using a real-time PCR specific for L. pneumophila and serogroup 1, combined with nested direct molecular typing, was adopted by Public Health England in 2012 to reduce reporting time for preliminary typing results. This rapid protocol was first used to investigate an outbreak that occurred in July/August 2012 and due to the positive feedback from that investigation, it was subsequently applied to other incidents in England and Wales where faster typing results would have aided incident investigation. We present here results from seven incidents that occurred between July 2012 and June 2015 where the use of this rapid approach provided preliminary characterization of the infecting strain in an average 1.58 days (SD 1.01) after sample receipt in contrast to 9.53 days (SD 3.73) when standard protocols were applied.

Waste from livestock and poultry breeding and its potential assessment of biogas energy in rural China

Global livestock and poultry industry is growing continuously, with large amounts of excreta produced. These wastes could be either important anaerobic fermentation materials of biogas energy or, if discharged into the environment without appropriate processing, serious pollution sources to soil and water systems. In developing countries, rural energy poverty is currently a major threat to sustainable development and livelihoods. Hence, the availability of clean, affordable and reliable energy is of significant concern in both policy and scholarly circles. Moreover, pollutants related with animal husbandry have been identified as one of the dominant contributors to contamination of water systems, such as surface water eutrophication and groundwater nitrate enrichment. Consequently, assessing waste from livestock and poultry breeding and the associated biogas systems is of critical essence in rural energy and environmental decision-making. The present study concentrates on a Chinese context and attempts to explicitly investigate Environmental Kuznets Curve (EKC) applying heterogeneous panel cointegration methods, combining with distribution and characteristics of waste from livestock and poultry breeding for China's 31 provincial economies from 1991 to 2013. And, potentiality of biogas energy and its CO2 emission reduction based on the utilization of waste is assessed. The empirical results indicate an inverted U-shaped Environmental Kuznets Curve in N indicator resulting from livestock and poultry breeding, where value of the turning point is approximately CNY 51,800. With economic growth and consumptive change, problems arising from animal husbandry mode can be increasingly great. There will be many major challenges to address these special environmental issues in rural area, especially in Central China and West China. Biogas production by animal excreta could be one of the most important rural energies and waste treatment patterns, which could reach 63.65 billion m3 in 2013, equivalent to approximately 20% of natural gas used, and might offer a GHG reduction of more than 220 million tons of CO2 eq. China should assign greater importance to special agricultural pollution and energy options in rural communities, in addition to ‘beautiful countryside’ propaganda.

Sorption of organic compounds by organo-zeolites [abstract

Organic compounds such as BTEX and PAHs are one of the most common contaminants in water system. These contaminants would take decades to degrade and they have harmful effects on human health (Qin et al., 2008). Several treatment methods have been developed to remove those contaminants from industrial wastewater. They include ion-exchange, filtration, adsorption and the use of various types of sorbents for example zeolites (Kibazohi et al., 2004; Mathur et al., 2007; Aivaliotiet al., 2012; Almeida et al. 2012). Natural clinoptilolite (Cp) from the Bystre deposit in Slovakia and zeolite Na-X synthesized from fly ash has been modified with a hexadecyltrimethyl ammonium bromide (HDTMA) in amounts of 1.0 and 2.0 of external cation exchange capacity (ECEC) of the zeolites (Szala et al., 2013). The sorption properties of unmodified zeolites and organo-zeolites in terms of aqueous solutions of benzene, ethylobenzene, toluene, p-xylene (BTEX) and their mixtures as well as anthracene, naphthalene, benzo[a]pyrene, dibenzo[a,h]anthracene (PAHs) and their mixtures at different concentrations were evaluated. The results showed that the modification of the zeolite Na-X and Cp with HDTMA improves the sorption properties. Modification in the amount of 1.0 ECEC proved to be the best in terms of p-xylene, anthracene, naphthalene, benzo[a]pyrene, dibenzo[a,h]anthracene. On the other hand benzene, ethylobenzene and toluene were adsorbed the most effectively by 2.0 ECEC modification of Na-X and Cp. Based on experimental data, the removal efficiencies for BTEX follows the order: p-xylene > toluene > benzene > ethylobenzene, for POHs: dibenzo[a,h]anthracene > benzo[a]pyrene > anthracene > naphthalene. P-xylene and naphtalene were adsorbed in the greatest quantity and benzene and anthracene in the lowest quantity from the mixtures of BTEX and PAHs, respectively. The sorption efficiency depends on the physicochemical properties of the organic compounds (dipole moment, molar mass, molecule structure and the time of the sorption process) as well as natural Cp and synthetic zeolite Na-X properties, such as Si/Al ratio, texture parameters and external cation exchange capacity. With an increasing concentration of the hydrocarbons in the solution the sorption capacity increases (Szala et al., 2015). Natural Cp is a better sorbent than synthetic zeolite Na-X in case of BTEX sorption, while PAHs are adsorbed more effectively by zeolite Na-X and its modifications. The mechanism of the sorption consists on the dissolving of the organic compounds into the organic layer of the surfactant (on the zeolites’ surface) as well as on the organic compounds’ penetration into the mesopores.

Scientific Symposium “Small Solution for Big Water-Related Problems: Innovative Microarrays and Small Sensors to Cope with Water Quality and Food Security”

This issue presents the conclusive results of two European Commission funded Projects, namely Universal Microarrays for the Evaluation of Fresh-water Quality Based on Detection of Pathogens and their Toxins (MicroAQUA) and Rationally Designed Aquatic Receptors (RADAR). These projects focused their activities on the quality of drinking water as an extremely important factor for public health of humans and animals. The MicroAQUA Project aimed at developing a universal microarray chip for the detection of various pathogens (cyanobacteria, bacteria, viruses and parasitic protozoa) and their toxins in waters. In addition, the project included the detection of select species of diatoms, which represent reliable bio-indicators to assess overall water quality. Large numbers of compounds are released into the environment; some of these are toxins such as endocrine disrupting compounds (EDCs) and can affect the endocrine, immune and nervous systems of a wide range of animals causing alterations such as reproductive disorders and cancer. Detection of these contaminants in water systems is important to protect sensitive environmental sites and reduce the risk of toxins entering the food chain. A modular platform for monitoring toxins in water and food production facilities, using biosensors derived from aquatic organisms, was the main goal of RADAR Project.

Treatment of water contaminated with methyl tertiary butyl ether using UV/chlorine advanced oxidation process

Methyl tertiary butyl ether (MTBE) is a widely used gasoline additive to improve the air quality by increasing the oxygen content of the fuel. After extensive use for some years in the USA, it was recognized as a groundwater contaminant. Several remediation techniques are available for the removal of MTBE from contaminated water systems. However, the inherent limitations of each removal technique makes further research promising. The aim of this study was to investigate the MTBE degradation in water with chlorine-based advanced oxidation process (AOP). A bench scale study was carried out by varying the experimental conditions such as UV radiation intensity, pH, chlorine doses, and treatment time. Free chlorine was used as a chemical oxidant in combination with low-pressure (LP) and medium-pressure (MP) mercury lamps to degrade MTBE in water. LP and MP UV/chlorine were able to degrade more than 99% of MTBE in deionized water within 15–30 min at pH 5 and 7, respectively. The MTBE removal in groundwater sample with LP UV/chlorine and MP UV/chlorine is greater than 99 and 90% after 30 min respectively. The electrical energy per order estimated for LP UV/chlorine and MP UV/chlorine to treat ground water sample was 4.01 and 54.67 kW h/m3 respectively. Chlorine-based AOP could be a promising technique for treating water contaminated with MTBE.

Legionellosis on the Rise: A Review of Guidelines for Prevention in the United States.

Reported cases of legionellosis more than tripled between 2001 and 2012 in the United States. The disease results primarily from exposure to aerosolized water contaminated with Legionella. To identify and describe policies and guidelines for the primary prevention of legionellosis in the US. An Internet search for Legionella prevention guidelines in the United States at the federal and state levels was conducted from March to June 2012. Local government agency guidelines and guidelines from professional organizations that were identified in the initial search were also included. Federal, state, and local governing bodies and professional organizations. Guidelines and regulations for the primary prevention of legionellosis (ie, Legionnaires' disease and Pontiac fever) have been developed by various public health and other government agencies at the federal, state, and local levels as well as by professional organizations. These guidelines are similar in recommending maintenance of building water systems; federal and other guidelines differ in the population/institutions targeted, the extent of technical detail, and support of monitoring water systems for levels of Legionella contamination. Legionellosis deserves a higher public health priority for research and policy development. Guidance across public health agencies for the primary prevention of legionellosis requires strengthening as this disease escalates in importance as a cause of severe morbidity and mortality. We recommend a formal and comprehensive review of national public health guidelines for prevention of legionellosis.

Enumeration of Somatic and F-RNA Phages as an Indicator of Fecal Contamination in Potable Water from Rural Areas of the North West Province.

Bacteriophages are regarded as enteric viral indicators in faecally contaminated water systems and may indicate the presence of human viral pollution. They are relatively resistant to inactivation by natural and treatment processes. In this study, the presence of somatic coliphages and F-RNA coliphages was investigated in potable water from rural areas in the North West province. Water samples were aseptically collected from boreholes and tap water from some rural communities in the North West Province. Physical parameters of the water, such as the temperature, pH and turbidity, were measured before sample collection. Double-agar layer assay was performed using ISO, (1995, 2000) standard methods. Bottled water was used as a negative control and the strains фX174 and MS2 as positive controls. Of the 16 water samples collected, 15 were positive for somatic bacteriophages while F-RNA coliphages were detected in only two samples. Amongst the positive samples 189 and three plaque forming units were obtained for both somatic and F-RNA coliphages, respectively. No coliphage was detected in water from Masamane tap 1. The rest of the samples obtained from various rural areas were positive and did not comply with national and international standards for potable water. This was a cause for concern and should be further investigated.

Molecular dynamics simulation study of rheological properties of CuO–water nanofluid

Nanoparticle (NP) dispersion in engineering fluids holds significant characteristics that impact the quality and performance of liquid fluidic systems, like in biomedical fluids, contaminated water system, heat and energy transfer applications. This paper investigates the dispersal dynamics of metal oxide NPs in the aqueous fluid using large-scale Atomic/Molecular Parallel Simulator by applying CuO NPs as a targeting material with water (H2O). Two major parameters were chosen for evaluating the actual system in the simulation: (a) Discrete particle dynamics (DPD) and (b) Charged optimized many body (COMB) potential. In comparison to the experimental results, the current molecular dynamics (MD) simulation results show good correlations with the actual MD viscosity as 2.44 mPas at 313 K. The outcomes of this study were compared with the reference study of Loya et al., i.e. CuO–water nanofluid dispersion using DPD and smoothed particle hydrodynamics that demonstrated a marginal variation between both studies. The current research investigates viscosity, diffusion coefficient and radial distribution function with implementation of COMB potential on CuO–H2O dispersion.

Impact of Organic Contamination on Some Aquatic Organisms.

Background:Contamination of water systems with organic compounds of agricultural uses pose threats to aquatic organisms. Carbaryl, chlorpyrifos, and diuron were considered as model aquatic pollutants in this study. The main objective of this study was to characterize the toxicity of organic contamination to two different aquatic organisms.Materials and Methods:Low concentrations (0.0–60 µmol/L) of carbaryl, diuron and very low concentration (0.0–0.14 µmol/L) of chlorpyrifos and their mixtures were tested against fish and Daphnia magna. Percentage of death and immobilization were taken as indicators of toxicity.Results:Toxicity results to fish and D. magna showed that chlorpyrifos was the most toxic compound (LC50 to fish and D. magna are 0.08, and 0.001 µmol/L respectively), followed by carbaryl (LC50 to fish and D. magna are 43.19 and 0.031 µmol/L), while diuron was the least toxic one (LC50 values for fish and D. magna are 43.48 and 32.11 µmol/L respectively). Mixture toxicity (binary and tertiary mixtures) showed antagonistic effects. Statistical analysis showed a significant difference among mixture toxicities to fish and D. magma.Conclusion:Fish and D. magam were sensitive to low concentrations. These data suggest potent threats to aquatic organisms from organic contamination.

Immobilization of Cd, Zn, and Pb from Soil Treated by Limestone with Variation of pH Using a Column Test

Decades of mining in South Korea have resulted in the contamination of large amounts of soil by metals. The most feasible approach to site restoration requires the use of a stabilization agent to reduce metal mobility. This study examined the leaching characteristics of limestone used as a stabilization agent when subjected to solutions of differing pH. In a laboratory-scale column test, solutions with pH values of 3.5, 4.6, and 5.6, representing acidic to nonacidic rainfall, were applied to soil mixed with limestone. Test results indicate that metal components can be released with the addition of acidic solutions, even if the soil is highly alkaline. Cd and Zn, in particular, exhibited abrupt or continuous leaching when exposed to acid solutions, indicating the potential for contamination of water systems as metal-laden soils are exposed to the slightly acidic rainfall typical of South Korea. Treatment using stabilization agents such as limestone may reduce leaching of metals from the contaminated soil. Stabilizing metal-contaminated farmland is an economical and feasible way to reduce pollutants around abandoned metal mines.

Pseudomonas aeruginosa in hospital water systems: biofilms, guidelines, and practicalities

Pseudomonas aeruginosa is one of many micro-organisms that can act as an opportunistic pathogen and colonize and infect vulnerable patients. Hospital water is a recognized source P. aeruginosa. Several outbreaks, including the incidents involving babies in Northern Ireland in 2011/12, have been attributed to contaminated water systems. As a direct result of the deaths of four neonates in Northern Ireland, guidance documents--addendums to Health Technical Memorandum 01-04 (Department of Health, England)--were produced to advise National Health Service managers on how to deal with the presence of P. aeruginosa in augmented care units. The guidance was based on current expert opinion and limited scientific evidence. Public Health England has established a reproducible and controllable water distribution test rig in a laboratory setting to further understand the contamination of water systems by P. aeruginosa and to identify vulnerable sites for microbial colonization. It is anticipated that these studies will add to the evidence base and enable the guidance documents to be updated in due course.

Legionella spp., amoebae and not-fermenting Gram negative bacteria in an Italian university hospital water system.

In hospital and other health care facilities, contamination of water systems by potentially infectious microorganisms, such as bacteria, viruses and protozoa, is a source of nosocomial infections, which may originate fromcolonization of water pipes, cooling towers, spa pools, taps, showers and water supplies. Objective. The study focuses on the occurrence of Legionella spp., free-living amoebae and non-fermenting Gram-negative microorganisms in a University hospital water system located in the town of Messina (Sicily, Italy), which had never been examined previously. From January 2008 - March 2009, hot tap water samples were collected from 10 wards. Legionella spp. recovered on selective culture medium were identified by microagglutination latex test; free-living amoebae were cultured using Escherichia coli as a food source. Non-fermenting Gram negative microorganisms were identified by API 20 NE strips. Legionella spp. were found in 33.33% of the samples. L. pneumophila serogroup 1 was recovered from the Laboratory Diagnostic and Anaesthesia-Neurology Wards, with a peak of 3.5 × 10(4) cfu/L in May 2008. L. pneumophila serogroups 2-14 were found in the Othorhinolaryngology, Pathologic Anatomy, Paediatrics and Surgery Wards, and peaked (4 × 10(4) cfu/L) in April 2008. Pseudomonadaceae and Hyphomycetes were also detected. Legionella spp. were recovered from samples positive for non-pathogenic amoebae Hartmannella spp. This first study of a Messina hospital water system suggested potential health risks related to the detection of Hartmannella spp., as reservoirs for Legionella spp., and Pseudomonas aeruginosa, a Gram negative non-fermenting bacterium frequently causing nosocomial pneumonia. The urgent need for monitoring programmes and prevention measures to ensure hospital water safety is stressed.

Editorial: advanced catalytic materials for environmental application

Environmental protection is directly related to the sustainable development of the economy and society. Controlling the release of major air and water pollutants remains a daunting challenge in China. The removal of major air pollutants [PM, SO2, NOx, volatile organic compounds (VOCs), and Hg] from stationary and mobile sources is becoming increasingly urgent to improve air quality. Additionally, the removal of numerous industrial and natural chemical compounds from contaminated water systems is essential to maintaining the availability of clean water. Therefore, cost-effective and appropriate air pollution control and water treatment technologies must be explored and implemented. Regarding air pollution control, the selective catalytic reduction of NOx (SCR) by ammonia and hydrocarbons over metal oxide and zeolite catalysts is discussed; non-toxic transition metal oxides supported on titania and zeolite matrices are emerging new catalysts. The removal of Hg from flue gas using catalysis is also a new research direction in this field. The oxidation of VOCs using photoand thermal catalysis for indoor air quality improvement is reviewed based on recent research progress achieved worldwide. Regarding wastewater treatment, the catalytic elimination of inorganic and organic pollutants from wastewater is presented. Additionally, mechanisms for the abatement of air and water pollutants using catalysis are discussed in detail. Finally, several aspects should be aimed in future research of environmental catalysis for the abatement of major pollutants in air and water. For instance, the development of environment-friendly catalysts that have attracted much attention in both the academic and industrial fields should be enhanced. Significant efforts should be made towards the development of highly active and durable catalysts, and anti-fouling catalysts for long-term successful treatments. For the selectivity of pollutants transformation to harmfulness should be more concerned by adjusting heterogeneous catalytic processes. Further efforts should be made to gradually improve material or reactor design for pilot and demonstration purposes. Moreover, much work is required to combine catalytic processes with other remediation technologies.

Mutation of environmental mycobacteria to resist silver nanoparticles also confers resistance to a common antibiotic.

Non-tuberculous mycobacteria are a threat to human health, gaining entry to the body through contaminated water systems, where they form persistent biofilms despite extensive attempts at disinfection. Silver is a natural antibacterial agent and in nanoparticle form activity is increased by a high surface area. Silver nanoparticles (AgNPs) have been used as alternative disinfectants in circulating water systems, washing machines and even clothing. However, nanoparticles, like any other antibiotic that has a pervasive durable presence, carry the risk of creating a resistant population. In this study Mycobacterium smegmatis strain mc(2)155 was cultured in AgNP enriched agar such that only a small population survived. Surviving cultures were isolated and re-exposed to AgNPs and AgNO3 and resistance to silver was compared to a negative control. After only a single exposure, mutant M. smegmatis populations were resistant to AgNPs and AgNO3. Further, the silver resistant mutants were exposed to antibiotics to determine if general resistance had been conferred. The minimum inhibitory concentration of isoniazid was four times higher for silver resistant mutants than for strain mc(2)155. However, core resistance was not conferred to other toxic metal ions. The mutants had lower resistance to CuSO4 and ZnSO4 than the mc(2)155 strain.