Use Of Biocides Research Articles

Inhibition of green algae growth by corrole-based photosensitizers.

This study was performed to examine the potential of photodynamic inactivation for growth inhibition of green algae through generation of singlet oxygen. Two cationic and two anionic corroles were investigated according to their photoinhibitive effect on two strains of green algae using visible light for photoexcitation. The development of biomass over the experimental period of 18 days was followed using absorptive properties of the algae samples. The anionic photosensitizers showed no significant phototoxicity, whereas the cationic photosensitizers caused a drastic reduction of biomass on a short time scale and also displayed long-term inhibition of algae growth. In general, it was proven that photodynamic inactivation of green algae is possible. Concluding from the results of this study, cationic photosensitizers are favourable for this task, while anionic photosensitizers are not suited. Phototrophic biofilms are an important factor in biofouling and biodeterioration of building materials, causing great damage to historic and contemporary constructions. Growth inhibition of phototrophic organisms using photodynamic inactivation could pose an alternative to the use of biocides. To this end, successful application of this approach on green algae is a vital step in the development of suitable photosensitizers.

Lab Diagnosis of Legionnaires’ Disease

Legionnaires’ disease is a multi-system disease which causes atypical pneumonia due to Legionella bacteria, most commonly of the species Legionella pneumophila. About one out of every 10 people who get sick from Legionnaires’ disease will die. Most common source of infection-contaminated water supply through inhalation of contaminated water droplets (aerosols). A laboratory diagnosis of Legionnaires’ disease can be made using a variety of laboratory tests including: culture/isolation of the causative organism, antigen detection in urine, a significant rise in antibody titres or PCR methods. Determination of the monoclonal subtype and molecular sequence typing can support linking between strains from the sampled environment and from patients. The control measures available to reduce the amount of Legionella in a water system include structural adaptations to the water system, temperature control, disinfection using chemicals or other oxidizing materials, and use of biocides or installation of filters. JMS 2014;17(2):50-54

Pore size criteria of mesh crop covers for the exclusion of tomato-potato psyllid (Bactericera cockerelli)

Control methods for tomato-potato psyllid (TPP; Bactericera cockerelli) are currently dominated by the use of synthetic biocides. A non-chemical alternative for TPP management is crop mesh, which forms a physical barrier between crop and pest. This study examined the ability of TPP adults to penetrate, or lay eggs through, 22 commercially available crop meshes using a laboratory bioassay. Adult TPP were prevented from moving through the mesh if the mesh complied with any one of the following criteria: shortest pore length <0.55 mm; longest pore length <0.60 mm; diagonal length <0.85 mm; area <0.3 mm2. Eggs were found on foliage only when TPP adults had penetrated the mesh, suggesting that eggs could not be laid through the mesh. The results indicate that crop meshes may provide non-chemical control for TPP that can be used by organic growers, and producers attempting to reduce chemical inputs as part of integrated pest management.

Acute toxicity of tralopyril, capsaicin and triphenylborane pyridine to marine invertebrates.

A need for environmentally acceptable alternative antifouling (AF) biocides has arisen through restrictions in the use of many common biocides in the European Union through the Biocidal Product Regulation (Regulation EU No. 528/2012). Three such alternatives are triphenylborane pyridine (TPBP), tralopyril and capsaicin. This study aims at extending the available information on the toxicity of these three emerging AF biocides to key marine invertebrates. Here we investigate the toxicity of tralopyril and capsaicin to the early life stages of the mussel Mytilus galloprovincialis and the sea urchin Paracentrotus lividus and also of tralopyril, capsaicin and TPBP to the early life stages of the copepod Tisbe battagliai. The EC50 that causes abnormal development of mussel's D-veliger larvae and impairs the growth of sea urchin pluteus larvae are respectively 3.1 and 3.0 μg/L for tralopyril and 3,868 and 5,248 μg/L for capsaicin. Regarding the copepod T. battagliai, the LC50 was 0.9 μg/L for tralopyril, 1,252 μg/L for capsaicin and 14 μg/L for TPBP. The results obtained for the three substances are compared to a reference AF biocide, tributyltin (TBT), and their ecological risk evaluated. These compounds pose a lower environmental risk than TBT but still, our results suggest that tralopyril and TPBP may represent a considerable threat to the ecosystems.

A MODEL-BASED DECISION SUPPORT TOOL FOR GREY MOULD PREDICTION

Grey mould (Botrytis cinerea) is one of the most severe diseases in greenhouse crops. For its control, humidity is kept low and chemical and biological control agents are used. An early warning system for disease outbreak likelihood would help to improve B. cinerea management. In greenhouses with model-based climate control there is scope for automatic humidity control to manage B. cinerea in trade-offs with other production parameters, such as energy saving and product quality. In the present paper a mathematical simulation model for Botrytis was developed as basis for greenhouse climate control. The model was designed from literature studies and implemented in a software simulation environment. The model consists of two components representing (1) crop microclimate and (2) disease development, including the complete life cycle of Botrytis cinerea from mycelium and spore development to sporulation and spore deposition on the susceptible plant parts. The model calculates durations of leaf wetness and leaf dryness in order to predict the success rate of spore penetration and thus infection. The model was parameterised for the cut flower Gerbera. The model was connected to a greenhouse climate simulator and in general form. Simulations were performed for a standard glass greenhouse located in The Netherlands using a reference climate year. The developed model for Botrytis control presents a novel design that creates a possible basis for a future climate regime to control Botrytis in greenhouses with a strong reduction of chemical biocide use.

English

The appropriate use of biocides is essential in any vaccine production facility and their proper evaluation using standardized tests marks the first step to ensure their proper use. Quantitative suspension tests against reference and environmental isolates were carried out to evaluate the efficacy of various biocides used in the main vaccine production facility in Egypt. Several use-dilutions of the biocides were evaluated at contact times of up to 5 min in case of antiseptics and 30 min in case of disinfectants to measure the biocide activity against bacteria, fungi and spores. Standard strains were used in addition to the main bacterial isolates identified in an environmental monitoring program carried out in the same facility. Alcohol based biocides showed bactericidal and fungicidal activity but no sporicidal activity. Chlorine based compounds and glutaraldehyde showed bactericidal and fungicidal effect while, the sporicidal effects depended on the used dilution and the contact time. Hydrogen peroxide showed bactericidal, fungicidal and sporicidal activity. Quaternary ammonium compounds tested showed very weak activity in all tests. Evaluation of the biocide is an essential step to guarantee the use of the most appropriate agent in any location. &nbsp; Key words: Biocides, antiseptics, disinfectants, vaccines, Egypt.

Is hepatitis B-virucidal validation of biocides possible with the use of surrogates?

The hepatitis B virus (HBV) is considered to be a major public health problem worldwide, and a significant number of reports on nosocomial outbreaks of HBV infections have been reported. Prevention of indirect HBV transmission by contaminated objects is only possible through the use of infection-control principles, including the use of chemical biocides, which are proven to render the virus non-infectious. The virucidal activity of biocides against HBV cannot be predicted; therefore, validation of the virucidal action of disinfectants against HBV is essential. However, feasible HBV infectivity assays have not yet been established. Thus, surrogate models have been proposed for testing the efficacy of biocides against HBV. Most of these assays do not correlate with HBV infectivity. Currently, the most promising and feasible assay is the use of the taxonomically related duck hepatitis B virus (DHBV), which belongs to the same Hepadnaviridae virus family. This paper reviews the application of DHBV, which can be propagated in vitro in primary duck embryonic hepatocytes, for the testing of biocides and describes why this model can be used as reliable method to evaluate disinfectants for efficacy against HBV. The susceptibility levels of important biocides, which are often used as ingredients for commercially available disinfectants, are also described.

Effect of sub-lethal concentrations of biocides on the susceptibility to antibiotics of multi-drug resistant Salmonella enterica strains

Ten multi-drug resistant Salmonella enterica isolates belonging to ten different serotypes were exposed to increasing sub-inhibitory concentrations of three biocides widely used in food industry facilities (trisodium phosphate, sodium nitrite, or sodium hypochlorite). Cultures were tested, before and after exposure to biocides, against 31 antibiotics of clinical significance by means of a standard disk-diffusion technique (CLSI). Exposed cultures displayed reduced susceptibility to a range of antibiotics, as compared with not exposed cultures. The impact of biocide exposure on reduced susceptibility to antibiotics was dependent on the Salmonella strain and the antibiotic family tested, susceptibility to aminoglycosides and cephalosporins being the most strongly affected. Results in the present study suggest that extensive use of biocides at sub-lethal concentrations could contribute to the emergence of antibiotic resistance in multi-drug resistant Salmonella enterica strains and therefore represent a public health risk. The intra-specific differences observed in antibiotic susceptibility underline the need to screen a wide range of strains.

Exposure of Escherichia coli ATCC 12806 to Sublethal Concentrations of Food-Grade Biocides Influences Its Ability To Form Biofilm, Resistance to Antimicrobials, and Ultrastructure

Escherichia coli ATCC 12806 was exposed to increasing subinhibitory concentrations of three biocides widely used in food industry facilities: trisodium phosphate (TSP), sodium nitrite (SNI), and sodium hypochlorite (SHY). The cultures exhibited an acquired tolerance to biocides (especially to SNI and SHY) after exposure to such compounds. E. coli produced biofilms (as observed by confocal laser scanning microscopy) on polystyrene microtiter plates. Previous adaptation to SNI or SHY enhanced the formation of biofilms (with an increase in biovolume and surface coverage) both in the absence and in the presence (MIC/2) of such compounds. TSP reduced the ability of E. coli to produce biofilms. The concentration of suspended cells in the culture broth in contact with the polystyrene surfaces did not influence the biofilm structure. The increase in cell surface hydrophobicity (assessed by a test of microbial adhesion to solvents) after contact with SNI or SHY appeared to be associated with a strong capacity to form biofilms. Cultures exposed to biocides displayed a stable reduced susceptibility to a range of antibiotics (mainly aminoglycosides, cephalosporins, and quinolones) compared with cultures that were not exposed. SNI caused the greatest increase in resistances (14 antibiotics [48.3% of the total tested]) compared with TSP (1 antibiotic [3.4%]) and SHY (3 antibiotics [10.3%]). Adaptation to SHY involved changes in cell morphology (as observed by scanning electron microscopy) and ultrastructure (as observed by transmission electron microscopy) which allowed this bacterium to persist in the presence of severe SHY challenges. The findings of the present study suggest that the use of biocides at subinhibitory concentrations could represent a public health risk.

Bacterial biofilm mechanical properties persist upon antibiotic treatment and survive cell death

Bacteria living on surfaces form heterogeneous three-dimensional consortia known as biofilms, where they exhibit many specific properties one of which is an increased tolerance to antibiotics. Biofilms are maintained by a polymeric network and display physical properties similar to that of complex fluids. In this work, we address the question of the impact of antibiotic treatment on the physical properties of biofilms based on recently developed tools enabling the in situ mapping of biofilm local mechanical properties at the micron scale. This approach takes into account the material heterogeneity and reveals the spatial distribution of all the small changes that may occur in the structure. With an Escherichia coli biofilm, we demonstrate using in situ fluorescent labeling that the two antibiotics ofloxacin and ticarcillin—targeting DNA replication and membrane assembly, respectively—induced no detectable alteration of the biofilm mechanical properties while they killed the vast majority of the cells. In parallel, we show that a proteolytic enzyme that cleaves extracellular proteins into short peptides, but does not alter bacterial viability in the biofilm, clearly affects the mechanical properties of the biofilm structure, inducing a significant increase of the material compliance. We conclude that conventional biofilm control strategy relying on the use of biocides targeting cells is missing a key target since biofilm structural integrity is preserved. This is expected to efficiently promote biofilm resilience, especially in the presence of persister cells. In contrast, the targeting of polymer network cross-links—among which extracellular proteins emerge as major players—offers a promising route for the development of rational multi-target strategies to fight against biofilms.

Worldwide Sustainability Hotspots in Potato Cultivation. 2. Areas with Improvement Opportunities

Agriculture has a large impact on the environment and retailers increasingly stimulate their suppliers to reduce the environmental impact of agricultural production. The environmental impact resulting from producing a commodity can be measured with a life cycle analysis (LCA) but performing an LCA is costly and time-consuming. In the first paper of this series a practical and general method to identify hotspot areas in crop production on a global scale was developed. The method was implemented for potatoes. The objective of the work reported here was to evaluate the tool and to identify improvement opportunities for each of seven indicators: yield, erosion risk, nitrogen surplus, depletion of water reserves, biocide use, carbon footprint, and impact on biodiversity. The tool produces realistic outputs that can be used to target improvement efforts and thus improves the use efficiency of limited resources. The tool can be expanded to produce similar results for other crops; methods to improve the resolution of the tool are discussed.

Green biocides, a promising technology: current and future applications to industry and industrial processes

The study of biofilms has skyrocketed in recent years due to increased awareness of the pervasiveness and impact of biofilms. It costs the USA literally billions of dollars every year in energy losses, equipment damage, product contamination and medical infections. But biofilms also offer huge potential for cleaning up hazardous waste sites, filtering municipal and industrial water and wastewater, and forming biobarriers to protect soil and groundwater from contamination. The complexity of biofilm activity and behavior requires research contributions from many disciplines such as biochemistry, engineering, mathematics and microbiology. The aim of this review is to provide a comprehensive analysis of emerging novel antimicrobial techniques, including those using myriad organic and inorganic products as well as genetic engineering techniques, the use of coordination complex molecules, composite materials and antimicrobial peptides and the use of lasers as such or their modified use in combination treatments. This review also addresses advanced and recent modifications, including methodological changes, and biocide efficacy enhancing strategies. This review will provide future planners of biofilm control technologies with a broad understanding and perspective on the use of biocides in the field of green developments for a sustainable future.

Antimicrobial resistance determinants in antibiotic and biocide-resistant gram-negative bacteria from organic foods

In the present study, a collection of 29 Gram-negative bacteria selected from organic foods according to antibiotics and biocide resistance were screened for multidrug efflux pumps and specific antibiotic resistance genes. The acrB pump gene of the AcrAB–TolC system was detected in all isolates. EfrAB determinants efrA and efrB were frequently detected (Enterobacter, Pantoea, Salmonella), while other efflux pump genes (norE, mepA mdeA, norC) were detected only in some Enterobacter and Pantoea isolates. Genes encoding resistance to quaternary ammonium compounds qacE and qacJ were detected only in Enterobacter isolates, while sugE was detected in Enterobacter and in one Pantoea isolate. The aminoglycoside-resistance ant(4_)-Ia gene was detected in Enterobacter, Pantoea agglomerans and Klebsiella oxytoca. The antibiotic resistance determinant most frequently found was lsa gene (Enterobacter, Pantoea and Salmonella isolates). Erythromycin resistance genes (ereA, ereB) were detected among Enterobacter, Klebsiella or Salmonella. The macrolide efflux pump msrA and the phosphotransferase type I mphA genes were detected in Salmonella. Other resistance determinants analyzed (mdfA, yhiUV, evgA, 455emeA, yvcC, qacA/B, qacC, qacG, qacH, norA, norB, norC, sdrM, sepA, mecA, emrE, smr, bla, cat, aac(6_)-Ie-aph(2_)-Ia, aph(2_)-Ib, aph(2_)-Ic, aph(2_)-Id, aph(3_)-IIIa, ermA, ermB, ermC, and mefA genes) were not detected in any isolate. Results from the present study suggest that the main mechanisms of antibiotic and biocide resistance in Gram-negative bacteria from organic foods rely on different kinds of efflux pumps of broad substrate specificity. The indiscriminate use of biocides in the food chain should be revised in order to minimize persistence of reservoirs of antimicrobial resistance in the food chain.

Recently introduced qacA/B genes in Staphylococcus epidermidis do not increase chlorhexidine MIC/MBC

Chlorhexidine is used as a disinfectant to prevent surgical infections. Recently, studies have indicated that chlorhexidine usage has selected methicillin-resistant Staphylococcus aureus strains that are tolerant to chlorhexidine and that this may be related to the presence of the qacA/B-encoded efflux pumps. Here, we evaluated if high-level exposure to chlorhexidine selects for tolerant colonizing Staphylococcus epidermidis and we addressed the consequences of long-term exposure to chlorhexidine. Chlorhexidine susceptibility and carriage of qacA/B was determined for colonizing S. epidermidis isolated from scrub nurses heavily exposed to chlorhexidine and were compared with isolates from non-users of chlorhexidine hand rubs. S. epidermidis blood isolates from the 1960s, before the wider introduction of chlorhexidine to the market, were also tested and compared with recently collected S. epidermidis blood isolates. There was no correlation between the use of chlorhexidine in scrub nurses and the presence of qacA/B genes in S. epidermidis isolates or increased MICs/MBCs of chlorhexidine for S. epidermidis isolates. While 55% of current blood isolates harboured the qacA/B genes, none of the 33 historical S. epidermidis isolates did, although their MICs and MBCs of chlorhexidine were comparable to those for current isolates. Chlorhexidine used as a hand rub does not select for S. epidermidis isolates with increased MICs or MBCs of chlorhexidine. However, the absence of qacA/B genes in S. epidermidis isolates obtained in the 1960s suggests that long-term use of biocides like chlorhexidine or related compounds may select for the presence of qacA/B genes.

English

The petroleum reservoirs are commonly exposed to bacterial contamination. The proliferation of several bacterial species, could modify the product quality, change viscosity, help other sulfate-reducing, iron reducing bacteria to grow, and accelerate reservoir biocorrosion. Thus, companies of storage and transport of petroleum frequently use biocides to prohibit bacterial proliferation. However, the use of the appropriate biocide, need an obvious knowledge of bacterial population harbouring the reservoir. Thus, in this study, we intended to isolate and identify the aerobic bacterial population existing in different reservoirs of petroleum derivatives in the refinery of Bizerte, Tunisia. The isolation and identification of these microorganisms may be of great interest in bioremediation of polluted sites. Besides, it could inform about hydrocarbon specificity of these microorganisms and therefore lead to the use of suitable biocides to clean these storage reservoirs. 25 different bacterial strains were isolated from water collected from reservoirs of crude oil, gasoline, diesel oil and kerosene. The different strains were identified using morphological and biochemical characterization, as well as sequencing of 16S rRNA. The systematic study of these strains showed that they belong to six different genera. The highest strain number was affiliated to the genera of Pseudomonas and Bacillus followed by genera of Staphylococcus, Enterobacter Comamonas and Paenibacillus. The results of this study are discussed in terms of the ecological significance of these microorganisms in relation with physico-chemical conditions of reservoirs and hydrocarbon composition. Key words: Bacterial diversity, storage reservoirs, phylogenetic relationships.

Biocide susceptibility in bifidobacteria of human origin

Disinfectants have been used in a variety of environmental applications, in products for personal care and in the food industry. The food industry has increased the use of biocides and chemical-based disinfectants to control microbial ecology at production sites in an effort to improve hygiene measures and food safety. However, the susceptibility profile of micro-organisms to disinfectants has been largely neglected. This study therefore aimed to provide this type of information by focusing on the four most commonly used biocides in the food industry, determining their minimum inhibitory concentrations (MICs) and analysing the distribution of MICs across a variety of micro-organisms. In total, 99 different strains of Bifidobacterium spp. were studied. Results showed a unimodal distribution of MICs for chlorhexidine, triclosan (Irgasan) and sodium hypochlorite with no apparent species-specific correlation. Conversely, part of the tested bifidobacteria population (20%) showed reduced susceptibility to benzalkonium chloride compared with the susceptibility exhibited by the majority of the tested bacterial community. The highest MICs were distributed among almost all of the considered Bifidobacterium spp. In generally, the sensitivity of the studied strains to the four tested biocides appeared to be a genus-related trait.

가습기 폐질환(Humidifier Lung)의 환경적 원인 인자 고찰

Background: In Korea, there is low awareness of the respiratory health problems caused by the use of humidifiers, leading to a lack of governmental measures. Objectives: The objectives of this study were to review cases of varying degrees of humidifier lung and fever in connection with the use of humidifiers and to summarize the probable environmental agents causing these cases. Methods: We searched all articles reporting on humidifier lung, humidifier fever, and humidifier diseases caused by the use of a humidifier both at home and in the workplace. Results: We summarized a number of cases of varying degrees of respiratory diseases resulting from inhalation of water mist of humidifiers containing various species of bacteria and fungi and their toxins. Type of respiratory disease connected with humidifier lung includes interstitial pneumonitis, hypersensitivity pneumonitis, fever and several respiratory symptoms. Non-tuberculous mycobacteria (NTM), Actinomycetes, endotoxins and contaminated humidifier water were the most commonly suspected probable environmental agents causing humidifier lung. In Korea, the use of humidifier biocide is suspected as a likely cause of fatal lung injury including death and lung transplantation. Conclusion: Governmental policy should be devised and measures including a national surveillance system should be taken to prevent humidifier lung caused by the use of humidifiers.

Resolving the mechanism of bacterial inhibition by plant secondary metabolites employing a combination of whole-cell biosensors

Tightening regulations regarding the use of biocides have stimulated interest in investigating alternatives to current antimicrobial strategies. Plant essential oils and their constituent compounds are promising candidates as novel antimicrobial agents because of their excellent ability in killing microbes while being non-toxic to humans at antimicrobially-active concentrations. Allyl isothiocyanate (AIT), carvacrol, cinnamaldehyde (CNAD), citral, and thymol were investigated for their antibacterial activity against Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. The five compounds were screened via disc diffusion assay and broth microdilution method, by which inhibition zone diameters, minimum inhibitory concentrations (MICs), and minimum bactericidal concentrations (MBCs) were determined. AIT and CNAD displayed the greatest inhibitory effects against all species tested, with AIT yielding MICs of 156.25mg/L and MBCs of 156.25 to 312.5mg/L, and CNAD yielding MICs of 78.125 to 156.25mg/L and MBCs of 78.125 to 312.5mg/L. Based on these results, AIT and CNAD were selected for closer examination of their toxic effects. Two complementary bioluminescence-based bacterial biosensors, E. coli HB101_pUCD607_lux and Acinetobacter baylyi ADP1_recA_lux, were employed to examine the dose-response relationships and mechanism of action of AIT and CNAD. This is the first reported study to employ a lux-based biosensor assay coupled with parallel plate count experiments to demonstrate that AIT and CNAD not only damaged cell membranes, but also disrupted cellular metabolism and energy production in bacteria. It is also the first to use genotoxicity-sensing whole-cell bioreporters to demonstrate that neither AIT nor CNAD induced expression of the universal DNA repair gene, recA. This suggests that AIT and CNAD were not genotoxic. As an antimicrobial agent, it is advantageous that the compound be genetically non-damaging so that toxicity towards higher multicellular organisms and resistance development can be minimized. Thus, AIT and CNAD may be of high value as novel antimicrobial agents.

Comparative Analysis of the Susceptibility to Triclosan and Three Other Biocides of Avian Salmonella enterica Isolates Collected 1979 through 1994 and 2004 through 2010

Few studies have been conducted on changes in the susceptibility of bacteria due to long-term use of biocides. A total of 375 avian Salmonella isolates collected in Germany from healthy or diseased animals during two time periods, 1979 through 1994 and 2004 through 2010, were included in the present study. The isolates were tested for their MICs of triclosan, acriflavine, benzalkonium chloride, and chlorhexidine by broth macrodilution. MIC50, MIC90, and the distribution of MICs were compared. The MIC ranges were 0.0625 to 0.5 μg/ml for triclosan, 16 to 256 μg/ml for acriflavine, 8 to 128 μg/ml for benzalkonium chloride, and 0.5 to 32 μg/ml for chlorhexidine. MIC50s and MIC90s were equal or differed by not more than one dilution step. For isolates from healthy poultry collected during the two time periods, statistical analysis revealed a significant increase only in MICs for chlorhexidine. Salmonellae from diseased birds were more susceptible to triclosan and benzalkonium chloride but less susceptible to acriflavine and chlorhexidine. Overall, only 25 strains had the highest detected MIC of 0.5 μg/ml triclosan, but an association with multidrug resistance could not be confirmed.

Recent advances in the potential interconnection between antimicrobial resistance to biocides and antibiotics

Workshop on biocides: do they select for antimicrobial resistance?Second International Conference on Antimicrobial ResearchLisbon, Portugal, 21–23 November 2012.Interconnection between microbial resistance to biocides and antibiotics is a topic of increasing interest given the recent changes in European legislation and claims of a risk of biocide use on bacterial resistance. In the second International Conference on Antimicrobial Research held in Lisbon in November 2012, a workshop specifically addressed this topic, presentations included approaches to risk assessment and investigations into the molecular mechanisms of biocide resistance and co- and cross-resistance to antibiotics. The overall conclusion was that, even if each biocide represents a specific case, there is scientific evidence that biocides select for biocide resistance, but that there is, so far, no conclusive evidence that this also determined or will determine an increase in antibiotic resistance.