Characterizing bacterial resistance to preservatives and disinfectants

Bacterial resistance to preservatives and disinfectants is a problem with serious economic and health consequences. Understanding the basis of resistance may lead to strategies or chemistries capable of reversing or subverting the mechanism. A collection of bacterial isolates resistant to dimethoxydimethyl hydantoin, glutaraldehyde, methylchloroisothiazolone/methylisothiazolone, and benzisothiazolone, as well as combination preservatives, has been gathered. In addition, a perusal of the literature also reveals reports of resistance to quaternary ammonium compounds, biguanides, iodophors, and peroxides, suggesting no particular chemistry is immune to resistance development. The majority of isolates in the collection are members of the genera Pseudomonas and Burkholderia, along with several representatives of the genus Alcaligenes and Enterobacter. Characterization of their susceptibility to other preservatives and disinfectants revealed several patterns of cross-resistance. All isolates were resistant to biocides other than the selecting compound. Several isolates were cross-resistant to either a quaternary ammonium compound or hydrogen peroxide; one P. fluorescens isolate was cross-resistant to both disinfectants. The presence of cross-resistance among preservatives and disinfectants has serious implications for the ability to eradicate resistant microbes from contaminated surfaces or manufacturing processes using commonly accepted disinfectants.     

Intrinsic and acquired resistance to quaternary ammonium compounds in food-related Pseudomonas spp

AIMS: To determine the sensitivity of a strain used for disinfectants testing (Pseudomonas aeruginosa ATCC 15442) and food-associated isolates to benzalkonium chloride and didecyl dimethylammonium chloride (DDAC). To determine whether the increase in bacterial resistance after adaptation to DDAC can be associated with phenotypic changes. To test the activity of alternative disinfectants to eliminate resistant Pseudomonas spp. METHODS AND RESULTS: Pseudomonas aeruginosa ATCC 15442 was among the most resistant strains tested using a bactericidal suspension test. Growth of a sensitive Ps. fluorescens in gradually higher concentrations of DDAC resulted in stable higher resistance and to some cross-resistance to several antibacterial agents, with the exception of disinfectants containing chloramine T, glutaraldehyde or peracetic acid. It was shown by microscopy that adaptation was followed by loss of flagella, and slime formation. Removal of the slime by sodium dodecyl sulphate resulted in partial loss of the acquired resistance. CONCLUSIONS: Pseudomonas spp. may adapt to survive against higher concentrations of quaternary ammonium compounds (QACs), but resistant strains can be eliminated with chemically unrelated disinfectants. SIGNIFICANCE AND IMPACT OF THE STUDY: The work supports the rotation of disinfectants in food processing environments for avoiding the development of bacterial resistance to QACs. The alternating disinfectants should be chosen carefully, because of possible cross-resistance.     

Bacterial metabolism of quaternary ammonium compounds.

Of 10 quaternary ammonium compounds tested for biodegradation by the biological oxygen demand technique, only decyl- and hexadecyltrimethylammonium bromides were decomposed by organisms derived from sewage and soil. A mixture consisting of individual strains of Pseudomonas and Xanthomonas grew in solutions containing decyltrimethylammonium bromide as sole carbon source. The xanthomonad metabolized this quaternary ammonium compound in the presence of other organic molecules. The products of this activity included 9-carboxynomyl- and 7-carboxyheptyltrimethylammonium, suggesting that the terminal carbon of the decyl moiety is oxidized and the resulting carboxylic acid is subject to beta-oxidation.     

食源微生物对季铵盐类消毒剂的抗性

季铵盐类消毒剂基于其高效低毒的杀菌效果,在食品加工、畜牧养殖、公共场所消毒各个方面得到广泛的应用,但是滥用消毒剂会使环境、工农业相关产品中的耐药菌大量产生。本文对国内外关于微生物对季铵盐类消毒剂的抗性概况、耐药基因及其表达产物的特征,以及相应的研究理论和方法进行了综述。     

Kinetics of tethering quaternary ammonium compounds to K(+) channels

Polymeric maleimido-quaternary ammonium (QA) compounds have been shown to function as molecular tape measures when covalently tethered to external cysteine residues of a Shaker K(+) channel (Blaustein R.O., P.A. Cole, C. Williams, and C. Miller. 2000. Nat. Struct. Biol. 7:309-311). For sufficiently long compounds, the cysteine-maleimide tethering reaction creates a high concentration, at the channel's pore, of a TEA-like moiety that irreversibly blocks current. This paper investigates a striking feature of the maleimide-cysteine tethering kinetics. Strong blockers-those that induce substantial levels (>80%) of irreversible inhibition of current-react with channel cysteines much more rapidly than weak blockers and, when delivered to channels with four cysteine targets, react with multiexponential kinetics. This behavior is shown to arise from the ability of a strong blocker to concentrate its maleimide end near a channel's cysteine target by exploiting the reversible pore-blocking affinity of its QA headgroup.     

临床分离铜绿假单胞菌对氟喹诺酮类抗菌药物的耐药性检测

目的了解临床分离铜绿假单胞菌对喹诺酮类等抗菌药物的耐药性。方法琼脂稀释法测定86株铜绿假单胞菌对5种氟喹诺酮类抗菌药物以及头孢吡肟、美罗培南的耐药性。结果铜绿假单胞菌对诺氟沙星、氧氟沙星、左氧氟沙星、环丙沙星、加替沙星的耐药率分别为50%、61.6%、51.2%、48.8%、51.2%;对头孢吡肟和美罗培南的耐药率分别为30.2%、23.2%。结论铜绿假单胞菌对氟喹诺酮类抗菌药物耐药显著,临床应加强检测和监测。     

Overexpression of the Escherichia coli sugE gene confers resistance to a narrow range of quaternary ammonium compounds

SugE of Escherichia coli, first identified as a suppressor of groEL mutations but a member of the small multidrug resistance family, has not previously been shown to confer a drug resistance phenotype. We show that high-level expression of sugE leads to resistance to a subset of toxic quaternary ammonium compounds.     

Resistance of Staphylococcus aureus strains to quaternary ammonium compounds and chlorhexidine

The level of susceptibility of 90 different Staphylococcus aureus strains to chosen quaternary ammonium compounds: cetyltrimethyl ammonium bromide, benzalkonium chloride and benzethonium chloride as well as to chlorhexidine digluconate were examined. The examined strains consist of three groups: hospital originated MRSA, hospital originated MSSA and non-hospital MSSA. The significant differences between these groups were observed in they susceptibility to the investigated disinfectants. The obtained MIC values showed that the most resistant were hospital MRSA strains, where 55% was estimated as resistant to cetyltrimethyl ammonium bromide, 72% were resistant to benzalkonium chloride and benzethonium chloride and 7% were resistant to chlorhexidine digluconate. Among hospital originated MSSA 3% of strains were resistant to cetyltrimethyl ammonium bromide and 6% were resistant to benzalkonium chloride and benzethonium chloride. 14% non-hospital S. aureus strains were resistant to benzalkonium chloride and benzethonium chloride. None were resistant to chlorhexidine digluconate or cetyltrimethyl ammonium bromide.     

The qacG gene on plasmid pST94 confers resistance to quaternary ammonium compounds in staphylococci isolated from the food industry

The 2.3 kb resistance plasmid pST94 revealed a new gene (qacG) encoding resistance to benzalkonium chloride (BC), a commonly used quaternary ammonium disinfectant, and the intercalating dye ethidium bromide (Eb) in staphylococci isolated from the food industry. The 107 amino acid QacG protein showing 69.2% identity to the staphylococcal multi-drug resistance protein Smr is a new member of the small multi-drug resistance (SMR) protein family. QacG conferred resistance via proton dependent efflux. An additional ORF on pST94 encoded a protein with extensive similarity to replication proteins of other Gram-positive bacteria. Gene constructs containing the qacG and smr gene region combined with the smr or qacG promoter, respectively, indicated that QacG is more efficient than Smr and that qacG has a weaker promoter. Resistant qacG-containing cells could be adapted to withstand higher concentrations of BC. Adapted qacG-containing cells showed increased resistance mainly to BC. In contrast, adaptation of sensitive cells showed cross-resistance development to a range of compounds. Induction of proton-dependent efflux was observed for BC-adapted staphylococci cells not containing qacG. The ability of sublethal concentrations of BC to develop cross-resistance and induce efflux mechanisms could be of practical significance; it should be considered before use of any new disinfectant and in the design of better disinfection procedures.     

茄子种质资源抗青枯病的鉴定与评价

对304份茄子种质资源进行抗青枯病苗期人工接种鉴定,筛选出免疫材料10份,高抗材料51份,抗病材料35份,中抗材料32份,感病或高感材料176份,分别占鉴定材料的3.3%、16.8%、11.5%、10.5%和57.9%.茄子野生近缘种Solanum sisymbriifolium和S.torvum对青枯病有较强的抗病性,可作为茄子青枯病的抗源材料.获得4份抗青枯病的种间体细胞杂种.茄子对青枯病的抗性遗传较为复杂,主要由多基因控制.     

Quaternary ammonium compounds in plants in relation to salt resistance

Fourteen plant species exhibiting a wide range of salt resistance as halophytes, semi-resistant glycophytes and sensitive glycophytes, have been grown in nutrient solution culture under low and high salt conditions. Inorganic analyses and shoot sap osmotic pressure values of these plants confirm that osmotic compensation at high salt levels is largely achieved by the accumulation of Na salts. Choline was found in shoots and roots in the range 1.0-0.2 μmol g fr. wt^?1 and varied little following salt stress. Trigonelline was found in some of the sensitive glycophytes and did not increase significantly in stressed plants. Betaine levels were high (10 μmol g fr. wt^?1) in the shoot of the halophytes at low salt conditions, lower values (1–10 μmol g fr. wt^?1) were found in the semi-resistant glycophytes and none detected in the sensitive glycophytes. In the two resistant groups betaine accumulated to higher levels following NaCl stress. Shoot betaine levels always exceeded root levels. Proline occurred in all plants and in all cases was accumulated following NaCl stress.     

Neutralisation of the antibacterial action of quaternary ammonium compounds with cyclodextrins

Abstract Cyclodextrins can be used to inactivate the antimicrobial activity of quaternary ammonium biocides. Their use offers several advantages over other methods which employ non-ionic detergents or phospholipids.     

Sinorhizobium meliloti chemotaxis to quaternary ammonium compounds is mediated by the chemoreceptor McpX

The bacterium Sinorhizobium meliloti is attracted to seed exudates of its host plant alfalfa (Medicago sativa). Since quaternary ammonium compounds (QACs) are exuded by germinating seeds, we assayed chemotaxis of S. meliloti towards betonicine, choline, glycine betaine, stachydrine and trigonelline. The wild type displayed a positive response to all QACs. Using LC–MS, we determined that each germinating alfalfa seed exuded QACs in the nanogram range. Compared to the closely related nonhost species, spotted medic (Medicago arabica), unique profiles were released. Further assessments of single chemoreceptor deletion strains revealed that an mcpX deletion strain displayed little to no response to these compounds. Differential scanning fluorimetry showed interaction of the isolated periplasmic region of McpX (McpX^PR and McpX_34‐306) with QACs. Isothermal titration calorimetry experiments revealed tight binding to McpX^PR with dissociation constants (K_d) in the nanomolar range for choline and glycine betaine, micromolar K_d for stachydrine and trigonelline and a K_d in the millimolar range for betonicine. Our discovery of S. meliloti chemotaxis to plant‐derived QACs adds another role to this group of compounds, which are known to serve as nutrient sources, osmoprotectants and cell‐to‐cell signalling molecules. This is the first report of a chemoreceptor that mediates QACs taxis through direct binding.     

CIP耐药的铜绿假单胞菌两种分子耐药机制关系的研究

目的探讨环丙沙星（CIP）耐药的铜绿假单胞菌临床分离株主动外排药物与gyrA、parC基因突变的关系。方法联合碳酰氰基-对-氯苯腙（CCCP）和CIP对CIP耐药的铜绿假单胞菌株进行主动外排阳性株和阴性株的筛选,并对这些菌株的gyrA,parC基因进行聚合酶链式反应-限制性片段长度多态性分析（PCR—RFLP）。结果57％（55／97）的CIP耐药菌株最小抑菌浓度（MIC）可被逆转,gyrA单基因突变率为65％,gyrA和pa-C双基因突变率为35％,未发现parC单基因突变的菌株。主动外排阳性组与阴性组gyrA、parC基因突变情况差异无显著性。结论在本地区铜绿假单胞菌对CIP的耐药机制中,主动外排系统表达上调与抗菌药物作用靶位的改变均占有重要的地位,两者可能是并存的两种相对独立的机制。     

Changes in fatty acid composition of Pseudomonas aeruginosa ATCC 15442 induced by growth conditions: consequences of resistance to quaternary ammonium compounds

The effects of changes in the fatty acid composition of Pseudomonas aeruginosa induced by growth conditions on its resistance to two quaternary ammonium compounds (QAC) were investigated. The temperature and growth phase were the most influential parameters affecting the fatty acid composition of this bacterium. Furthermore, the formation of saturated fatty acids and cyclopropane fatty acids was stimulated by increasing the temperature, whereas the proportion of unsaturated fatty acids fell. The degree of saturation and the proportion of cyclopropane fatty acids increased in the course of the exponential and stationary phases. These modifications mostly concerned the inner membrane of the bacterium. Resistance of P. aeruginosa to both QAC tested was not significantly influenced by temperature and growth phase variations. Thus, resistance to the two QAC did not seem to be dependent on modifications of the fatty acid composition of the inner membrane.