A combined evaluation of the characteristics and antibiotic resistance induction potential of antibiotic wastewater during the treatment process.

Antibiotic wastewater contains a variety of pollutant stressors that can induce and promote antibiotic resistance (AR) when released into the environment. Although these substances are mostly in concentrations lower than those known to induce AR individually, it is possible that antibiotic wastewater discharge might still promote the AR transmission risk via additive or synergistic effects. However, the comprehensive effect of antibiotic wastewater on AR development has rarely been evaluated, and its treatment efficiency remains unknown. Here, samples were collected from different stages of a cephalosporin production wastewater treatment plant, and the potential AR induction effect of their chemical mixtures was explored through the exposure of the antibiotic-sensitive Escherichia coli K12 strain. Incubation with raw cephalosporin production wastewater significantly promoted mutation rates (3.6 × 103-9.3 × 103-fold) and minimum inhibition concentrations (6.0-6.7-fold) of E. coli against ampicillin and chloramphenicol. This may be attributed to the inhibition effect and oxidative stress of cephalosporin wastewater on E. coli. The AR induction effect of cephalosporin wastewater decreased after the coagulation sedimentation treatment and was completely removed after the full treatment process. A Pearson correlation analysis revealed that the reduction in the AR induction effect had a strong positive correlation with the removal of organics and biological toxicity. This indicates that the antibiotic wastewater treatment had a collaborative processing effect of conventional pollutants, toxicity, and the AR induction effect. This study illustrates the potential AR transmission risk of antibiotic wastewater and highlights the need for its adequate treatment.

Degradation of antibiotic Cephalosporin C in different water matrices by ionizing radiation: Degradation kinetics, pathways, and toxicity.

Cephalosporin antibiotics are ubiquitous emerging pollutants in various aquatic environments due to their extensive production and application. Herein, the radiolytic degradation of antibiotic Cephalosporin C (CEP-C) in different water matrices was comprehensively investigated using gamma radiation at various experimental conditions. The results revealed that CEP-C oxidation obeyed pseudo first-order kinetics, and 100%, 94.9%, 67.0%, 44.6% and 34.5% removal of CEP-C with 10-200 mg/L was achieved at 0.4 kGy, respectively. The degradation was faster at higher absorbed dose and acidic conditions (pH = 3.5). The inorganic anions, including SO42-, NO3-, and HCO3-, had negative influence on the degradation of CEP-C, the corresponding rate constant decreased from 4.603 to 3.667, 1.677 and 2.509 kGy-1 respectively in the presence of SO42-, NO3-, and HCO3-. The analysis of intermediate products indicated that CEP-C was oxidized to generate about 10 intermediate products. Besides, it was inferred that the thioether sulfur oxidation, ß-lactam ring opening, acetyl dissociation from dihydrothiazine ring and D-α-aminohexylamide group abscission were the major reaction mechanisms of CEP-C degradation by gamma radiation. Importantly, the antibacterial activity of CEP-C could be completely vanished by gamma radiation alone, while more toxic intermediate products might be formed. Addition of hydrogen peroxide and peroxymonosulfate could significantly improve the CEP-C degradation, and reduce the toxicity of intermediates of CEP-C degradation. Similar degradation behavior was observed in the groundwater and wastewater, implying that ionizing radiation can be used for degradation of Cephalosporin in water and wastewater.

Acute Oral Toxicity and Acute Intraperitoneal Studies of Thermally Treated Ceftiofur.

Ceftiofur (CEF) is a third-generation and the first animal-specific cephalosporin that is widely used in animal husbandry. As a heat-labile antibiotic, the cytotoxicity of CEF after thermal treatment has been reported. This study seeks to investigate the potential toxicity of thermally treated CEF (TTC) in vivo based on acute oral toxicity studies and acute intraperitoneal studies in mice. Our data indicated that TTC exhibited significant increased toxicity in mice compared with CEF. TTC resulted in weight gain, hypercholesterolemia, hepatocyte steatosis and hepatocyte mitochondrial damage, and downregulated ß-oxidation-related genes in mice in acute oral toxicity studies. In addition, TTC caused acute pulmonary congestion, increased levels of reactive oxygen species (ROS), prolonged coagulation time, and even death in mice in acute intraperitoneal toxicity studies. Our data showed that thermal treatment enhanced the toxicity of CEF in vivo. Lung and liver are the main target organs in the pathological damage process mediated by TTC. These findings suggested that residual CEF in animal-derived food may represent a potential food safety risk and pose a potential threat to human health.

Development of a highly efficient decontamination approach for ceftolozane in the pharmaceutical manufacturing environment.

The ß-lactam core is a key structure responsible for inducing both IgE-mediated acute-onset hypersensitivity and T-cell-mediated delayed-onset hypersensitivity with penicillins in humans. There is essentially no clinically significant immunologic cross-reactivity noted between the ß-lactam cores of penicillins and cephalosporins based on challenge studies in humans. The side-chains appear to be more important in inducing IgE-mediated acute-onset hypersensitivity and T-cell delayed-onset hypersensitivity with cephalosporins in humans. Despite these clinical findings, the U. S. Food and Drug Administration (FDA) still requires the level of ß-lactam-related antibiotic residues to be controlled at very low levels in manufacturing facilities. Ceftolozane is Merck & Co., Inc., Kenilworth, NJ, USA's (MSD's) 5th generation broad spectrum cephalosporin antibiotic against gram-negative bacteria. In searching for the optimal decontamination method of ceftolozane, most methods were found to be very slow in opening the ß-lactam ring in ceftolozane. Moreover, most of the previously reported decontamination methods applied analytical methods that only monitored the disappearance of the parent molecule as the endpoint of degradation. In this way, many of the ß-lactam-containing degradation products could be overlooked. In order to develop an efficient decontamination solution for ceftolozane, a sensitive ultra high performance liquid chromatography-high resolution-electrospray ionization-tandem mass spectrometry (UHPLC-HRMS/MS) method was first developed to ensure the detection of the ß-lactam ring in all degradation products. Through online UHPLC-UV-HRMS monitoring, 2.5 N KOH in 50% aqueous MeOH or 50% aqueous EtOH was identified as the best condition to fully degrade the ß-lactam ring in ceftolozane. This decontamination could be done within 15 min, even at 100 mg/mL concentration, and thus enable a quick turnaround time for equipment cleaning in the ß-lactam manufacturing facility. This method was also successfully applied to 12 other commercially available ß-lactam antibiotics.

Investigation of the effects of cephalosporin antibiotics on glutathione S-transferase activity in different tissues of rats in vivo conditions in order to drug development research.

Glutathione S-transferases are multifunctional enzymes for the cellular defense against xenobiotics and provide protection for organism. In this study, the inhibition effects of some antibiotics were investigated against GST obtained from albino-rats kidney, liver, and heart tissues. Ninety-six albino-rats were randomly divided into 16 groups (n:6). The first four groups were control groups that were administrated blank enjection and decapitated at 1-7 h. The other groups were administrated the antibiotics. In all tissues, GST activity was increased in antibiotics groups at 1st and 3rd hours compared to control groups, while it began to fall at 5th and 7th hours (p < .05). In kidney tissues, it was lower than the same control group the cefuroxime and cefoperazone groups at 7th hours (p < .05). In addition, almost all antibiotic groups of kidney tissues had higher GST activity at all hours than those of control groups, but it was higher only at 5th hours in heart tissues (p < .05).

Validated LC-MS/MS method for simultaneous analysis of 21 cephalosporins in zebrafish for a drug toxicity study.

Zebrafish model was used to perform this drug toxicity study. In this study, we monitored the absorption of drugs in zebrafish. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed in this experiment. The LC-MS/MS method was used for the simultaneous quantification of 21 cephalosporins in zebrafish. To prepare samples, rapid protein precipitation was performed with 1% formic acid in methanol. All the analytes were separated on a C18 column. These analytes were analyzed by performing multiple-reaction monitoring (MRM) scans in positive electrospray ionization mode. The ranges for limits of detection (LOD) and quantification (LOQ) were as follows: 0.01-10 ng/mL (S/N ≥ 3) and 0.05-25 ng/mL. Intra-and inter-day accuracy of all 21 cephalosporins were within the range of 80%-120%. Intra-and inter-day precision were within the range of 0.4%-11.2%. All the 21 analytes were analyzed within 10 min. In drug toxicity studies, the present method can be used to determine the internal concentrations of cephalosporins in zebrafish following the administration of drugs.

Cephalosporin antibiotics in the aquatic environment: A critical review of occurrence, fate, ecotoxicity and removal technologies.

Due to their widespread occurrence in the aquatic environment, human and veterinary cephalosporin antibiotics have been studied as water pollutants. In order to characterize environmental risks of this compound class, this review evaluates relevant data about physicochemical properties, occurrence, ecotoxicity and degradation of cephalosporins. Although application of cephalosporins is rather low compared to other antibiotics and their environmental life-time is believed to be short (i.e. days), the available data is insufficient to draw conclusions on their environmental relevance. Few studies concerning the fate of cephalosporins in soil are available, while hydrolysis and photo-degradation are suggested as the main attenuation processes in the aquatic environment. Cephalosporins have been detected in different aqueous matrices in concentrations ranging from 0.30 ng L-1 to 0.03 mg L-1, with sewage and wastewater being the main matrices with positive findings. For wastewater treatment purposes, several technologies have been tested for the abatement of cephalosporins, including photolysis and adsorption. In most cases, the technology employed led to complete or significant removal (>95%) of parental drugs but few authors reported on cephalosporins' metabolites and transformation products. Furthermore, the present ecotoxicological data are insufficient for comprehensive ecological risk quotient calculations. Considering the total of 53 cephalosporins, effective values (EC, LC, NOAEC, NOAEL, etc.) are only available for around 30% of parental drugs and are very scarce for cyanobacteria, which is considered to be the most sensitive group of organisms to antibiotics. Furthermore, it has been demonstrated that cephalosporins' transformation products can be more toxic and more persistent than the parental drugs. Few investigations considering this possibility are available. Consequently, more effort on ecotoxicological data generation and verification of biological inactivation of cephalosporins-related products is needed. Likewise, the lack of natural depletion rates and knowledge gaps on mixture effects for cephalosporins' degradation and toxicity have to be overcome.

Investigating the environmental risks from the use of spray-dried cephalosporin mycelial dreg (CMD) as a soil amendment.

Cephalosporin mycelial dreg (CMD) is a by-product of the pharmaceutical industry. Spray-drying is widely used for the dewatering process prior to the application of CMD as a soil amendment. However, the potential environmental behaviors and risks of spray-dried CMD amendment remain unclear. Here, a lab-scale incubation experiment was conducted to investigate the salinity, phytotoxicity, introduced antibiotics, heavy metals and the potential impacts of resistance genes in CMD-amended soil. Spray-dried CMD amendment generally increased soil salinity and only high dosed soils showed phytotoxic effects at the end of the incubation period, implying the physiological damage to plant growth. The introduced antibiotics quickly degraded over time, indicating a relatively low environmental persistence. Heavy metal slightly increased in soil receiving spray-dried CMD, and regulations should be developed to avoid metal accumulation. A decreased diversity and distinct patterns of ß-lactam resistance genes as well as a dose-effect of their enrichment were observed in CMD-amended soil, which might be partially explained by the specific metals and introduced antibiotics. Antibiotic resistance genes in soil may be a valuable tool for evaluating the environmental risk associated with use of CMD as a soil amendment.

Isolation, identification and in silico toxicity predictions of two isomers from cefotiam hydrochloride.

Two structural isomers of cefotiam in cefotiam hydrochloride for injection were observed, and the structures of the isomers were determined by mass spectrometry and various 1D and 2D NMR techniques. The thermo-isomerization mechanism of cefotiam was also discussed. Thermo-isomerization occurred not only in cefotiam but also in cephalosporins containing a 1-alkyl-1H-tetrazole-5-thiol side chain at C-3. Furthermore, the toxic effects of the two impurities of cefotiam hydrochloride were predicted and it is thought that they could be more toxic than cefotiam. The results reported in this article may be important for quality control and stability studies of this class of drugs.

Ecotoxicity of the two veterinarian antibiotics ceftiofur and cefapirin before and after photo-transformation.

The release of antibiotics into the environment may lead to deleterious effects in non-target organisms as well as pressure in antimicrobial resistance acquirement. Ceftiofur (CEF) and cefapirin (CEPA) are veterinary cephalosporins used for recurrent and economically relevant infections. Both antibiotics have been detected in aquatic environments and their fate during drinking water processing is still unknown. This work investigated the acute and chronic toxicities of CEF and CEPA towards aquatic organisms including stability tests. Complementary, the effects of water disinfection radiation (UV-C, 254nm) on ecotoxicological responses were studied. CEF and CEPA have significant decay during Daphnia magna tests, portraying half-lives (t1/2) of 49 and 53h, respectively. During tests with green algae (Scenedesmus spec.), CEPA was more instable (t1/2 88h) than CEF (t1/2 267h). CEF and its presumable hydrolysis products induced deleterious effects in Daphnia magna (48h EC50 139, LC50 179 in µM), which was not observed with Scenedesmus spec. (72h NOAEC 82.5±2.5µM). In the case of CEPA, no toxic effects were observed in either test (48h EC-LC50>510 and 72h NOAEC 57±6, in µM). Photolysis of CEPA resulted in toxic products, which were effective for the cladoceran but not for the green algae. On the other hand, the different radiation doses studied did not affect CEF ecotoxicity. This investigation illustrates the importance of cephalosporin hydrolysis during standard toxicity tests. Furthermore, the potential formation of species-specific toxic compounds during water processing is demonstrated, highlighting the need of further assessing toxicity of both cephalosporins and their transformation products.

A systematic toxicity evaluation of cephalosporins via transcriptomics in zebrafish and in silico ADMET studies.

Cephalosporins are beta-lactam antibiotics that are widely used in clinics in China. However, information on their toxicity to zebrafish is limited. This study reports that the toxicity effects of cephalosporins containing an N-methyltetrazolthio ring at the C-3 position (CNMTs) exposure on zebrafish were comparable to those predicted by in silico analysis. The effects of CNMTs on the mortality and malformation rate of zebrafish were concentration-dependent. The transcriptional levels of the has1 and cnnm2a genes, which are related to embryo development and absorption of Mg2+ in vivo, significantly changed. Several pathways that were enriched by differentially expressed genes (DEGs) were identified, and the most significantly co-enriched pathways were related to neuroactive ligand-receptor interactions, cardiac muscle contraction, and vascular smooth muscle contraction. In sum, the C-3 substituent in the nucleus 7-aminocephalosporanic acid (7-ACA) of CNMTs is responsible for the observed toxicity at higher concentrations, and the C-7 substituent plays an important role in toxicity at lower concentrations. Our results show that zebrafish embryos and transcriptomics may be useful for determining target organ toxicity, assessing the structure and toxicity relationship of chemicals, and improving drug safety assessments.

Cardiac safety evaluation in zebrafish and in silico ADME prediction of cephalosporins with an aminothiazoyl ring at the C-7 position.

Systems toxicology approaches have been used as important tools in the drug discovery and medicine quality control processes. The aim of this study was to assess the pharmacokinetic and toxicity properties of cephalosporins with an aminothiazoyl ring at the C-7 position (CATRs). Cardiac toxicity of the compounds was assessed in zebrafish embryos, and it was determined that CATRs disturbed the formation and development of the heart in a dose-dependent manner. Differentially expressed genes (DEGs) related to the heart were also identified by transcriptome analysis, and co-DEGs were obtained in the protein-protein interaction (PPI) network. Several Gene Ontology (GO) terms and pathways that were enriched by DEGs were identified, and the most significantly enriched pathways were adrenergic signaling in cardiomyocytes, cardiac muscle contraction, and vascular smooth muscle contraction. Combined molecular docking results elucidated that cardiac toxicity mainly depends on the mother nucleus structure 7-aminocephalosporanic acid (7-ACA). The predicted absorption, distribution, metabolism and excretion (ADME) profile suggests that there is a modification at the C-3 side chain of 7-ACA that could change the compound distribution in vivo. The 7-ACA mother nucleus is responsible for the CATRs induced cardiac toxicity, and the three DEGs (nppa, adra2c, and tnni1c) may potentially be utilized as novel biomarkers for CATRs. Our results show that zebrafish embryos may be used to reveal the pathways of cardiac toxicity and they play a vital role in drug safety assessments.

Toxic effect prediction of cefatirizine amidine sodium and its impurities by structure-toxicity relationship of cephalosporins.

The three-dimensional (3D) structure-toxicity relationship of cephalosporins was explored by computing the most stable conformations of 33 kinds of cephalosporins in aqueous solution and using the teratogenicity and lethality of these compounds obtained in zebrafish embryo toxicity testing to evaluate their toxic effects. The toxic effect of cefatirizine amidine sodium, a novel cephalosporin which has finished preclinical study, was investigated. It is thought that the teratogenic effect of the triazine ring at the C-3 position is the main toxic effect of cefatirizine amidine. In addition, cefatirizine amidine is no more toxic than cefathiamidine and ceftriaxone. The results of the zebrafish embryo toxicity test combined with gene expression microarray technology were consistent with the prediction. The toxic effects of some potential process-related impurities of cefatirizine amidine were also predicted.

Electrochemical treatment of penicillin, cephalosporin, and fluoroquinolone antibiotics via active chlorine: evaluation of antimicrobial activity, toxicity, matrix, and their correlation with the degradation pathways.

Antibiotics are pharmaceuticals widely consumed and frequently detected in environmental water, where they can induce toxic effects and development of resistant bacteria. Their structural variety makes the problem of antibiotics in natural water more complex. In this work, six highly used antibiotics (at 40 µmol L-1) belonging to three different classes (penicillins, cephalosporins, and fluoroquinolones) were treated using an electrochemical system with a Ti/IrO2 anode and a Zr cathode in the presence of NaCl (0.05 µmol L-1). The attack of electrogenerated active chlorine was found to be the main degradation route. After only 20 min of treatment, the process decreased more than 90% of the initial concentration of antibiotics, following the degradation order: fluoroquinolones > penicillins > cephalosporins. The primary interactions of the degrading agent with fluoroquinolones occurred at the cyclic amine (i.e., piperazyl ring) and the benzene ring. Meanwhile, the cephalosporins and penicillins were initially attacked on the ß-lactam and sulfide groups. However, the tested penicillins presented an additional reaction on the central amide. In all cases, the transformations of antibiotics led to the antimicrobial activity decreasing. On the contrary, the toxicity level showed diverse results: increasing, decreasing, and no change, depending on the antibiotic type. In fact, due to the conservation of quinolone nucleus in the fluoroquinolone by-products, the toxicity of the treated solutions remained unchanged. With penicillins, the production of chloro-phenyl-isoxazole fragments increased the toxicity level of the resultant solution. However, the opening of ß-lactam ring of cephalosporin antibiotics decreased the toxicity level of the treated solutions. Finally, the application of the treatment to synthetic hospital wastewater and seawater containing a representative antibiotic showed that the high amount of chloride ions in seawater accelerates the pollutant degradation. In contrast, the urea and ammonium presence in the hospital wastewater retarded the removal of this pharmaceutical.

Cefepime loaded O-carboxymethyl chitosan microspheres with sustained bactericidal activity and enhanced biocompatibility.

Cefepime (CFP) is a frequently used antibiotic for prevention of post-surgery infection. Systemic delivery of CFP in a bulk dose usually shows effective therapeutic effects, while cytotoxicity can also be generated. To avoid the drawback of systemic delivery of antibiotic, local and controlled administration of drug is being employed to prolong therapeutic effects and reduce cytotoxicity by sustaining drug release and minimizing drug exposure. In this work, CFP loaded polymer O-carboxymethyl chitosan (OCMC) microspheres (CFP-OCMC-MPs) were fabricated and their antimicrobial activity against Staphylococcus aureus as well as biocompatibility were evaluated. The microspheres possessed the spherical surface with diameter approximately 7 µm. Fourier transforms infrared spectral and wide-angle X-ray diffraction analysis showed that CFP was steadily incorporated. The drug loading content and encapsulation efficiency of the microspheres were 21.4 ± 0.5% and 42.3 ± 0.7%, respectively. The drug release profiles were found to be biphasic with an initial burst release followed by a gradual release phase, following the Higuchi model. In addition, the CFP-OCMC-MPs were able to kill all the bacteria cultured in suspension within 24 h and exhibited long-lasting bactericidal activity as demonstrated by inhibition zone study. Compared to CFP, CFP-OCMC-MPs showed a milder toxicity toward osteoblast-like cells over an 8 day period. All these results suggest that CFP-OCMC-MPs are endowed with sustained treatment of bacterial infection and enhanced biocompatibility.

Neurotoxicidad grave por cefepime en una paciente trasplantada renal: informe de caso / Severe neurotoxicity due to cefepime in a kidney transplanted patient: case report / Neurotoxicidade grave por cefepime numa paciente transplantada renal: relatório de caso

El cefepime es un antibiótico betalactámico utilizado para tratar pacientes con infecciones complicadas. Debido a que su excreción es predominantemente renal y a que su vida media se incrementa significativamente en pacientes con deterioro de la función renal, los efectos adversos pueden ser de mayor gravedad incluyendo los de índole neurotóxica. Se informa el caso de una paciente trasplantada renal que presentó neurotoxicidad secundaria al uso de cefepime.

Cefepime is a betalactamic antibiotic used for the treatment of patients with severe infections. It is mainly excreted by the kidney, so that its half-life is significantly increased in patients with kidney failure, and in this population adverse effects may be more severe including neurotoxicity. We report the case of a kidney-transplanted patient who presented neurotoxicity associated with the use of cefepime.

O cefepime é um antibiótico betalactámico utilizado para tratar pacientes com infecções complicadas. Devido a que sua excreção é predominantemente pelo rim, sua vida média se incrementa significativamente em pacientes com deterioração da função renal em quem os efeitos adversos podem ser de maior gravidade incluindo os de índole neurotóxica. Informa-se o caso de uma paciente transplantada renal que apresentou neurotoxicidade secundária ao uso de cefepime.

Toxic effects of cephalosporins with specific functional groups as indicated by zebrafish embryo toxicity testing.

Cephalosporins, derivatives of 7-aminocephalosporanic acid (7-ACA), are potent antibacterial agents. The toxicity prediction of these compounds is of considerable importance in new drug development. Zebrafish embryo toxicity testing was thought to be suitable for evaluation of the toxic properties of cephalosporins. Here, five kinds of cephalosporins and their isomers were used for investigation of the toxic functional groups of cephalosporins and for further evaluation of the efficacy of zebrafish embryo toxicity testing. Computational chemistry methods were also used to study the conformations of the stereoisomers of cephalosporins in aqueous solution to explore the relationship between the stereoisomers and the experimental results of toxicity tests on zebrafish embryos. Our results suggest that both the C-7 and C-3 substituents of cephalosporins are toxic functional groups. The toxic functional groups increase the toxic reaction of 7-ACA and can induce variable abnormal phenotypes in zebrafish embryo toxicity testing. The embryonic toxicities of cephalosporins were involved in organogenesis, mainly in the development of the cranial nerve, cardiovascular system, notochord and abdomen, and pigment formation; those tissues and organs are derived from ectoderm, mesoderm, and endoderm. The theoretical calculations showed a strong negative correlation between topological polar surface area (TPSA) values and the toxic effect, which indicated that molecular polarity may be crucial to the toxic effects of the isomers of cephalosporins. The concept of toxic functional groups may help us understand the safety differences of cephalosporins.

Phototransformation of cephalosporin antibiotics in an aqueous environment results in higher toxicity.

Photodegradation may be the most important elimination process for cephalosporin antibiotics in surface water. Cefazolin (CFZ) and cephapirin (CFP) underwent mainly direct photolysis (t(1/2) = 0.7, 3.9 h), while cephalexin (CFX) and cephradine (CFD) were mainly transformed by indirect photolysis, which during the process a bicarbonate-enhanced nitrate system contributed most to the loss rate of CFX, CFD, and cefotaxime (CTX) (t(1/2) = 4.5, 5.3, and 1.3 h, respectively). Laboratory data suggested that bicarbonate enhanced the phototransformation of CFD and CFX in natural water environments. When used together, NO(3)(-), HCO(3)(-), and DOM closely simulated the photolysis behavior in the Jingmei River and were the strongest determinants in the fate of cephalosporins. TOC and byproducts were investigated and identified. Direct photolysis led to decarboxylation of CFD, CFX, and CFP. Transformation only (no mineralization) of all cephalosporins was observed through direct photolysis; byproducts were found to be even less photolabile and more toxic (via the Microtox test). CFZ exhibited the strongest acute toxicity after just a few hours, which may be largely attributed to its 5-methyl-1,3,4-thiadiazole-2-thiol moiety. Many pharmaceuticals were previously known to undergo direct sunlight photolysis and transformation in surface waters; however, the synergistic increase in toxicity caused by this cocktail (via pharmaceutical photobyproducts) cannot be ignored and warrants future research attention.

Role of the two component signal transduction system CpxAR in conferring cefepime and chloramphenicol resistance in Klebsiella pneumoniae NTUH-K2044.

BACKGROUND: Klebsiella pneumoniae is a gram-negative, non-motile, facultative anaerobe belonging to the Enterobacteriaceae family of the γ-Proteobacteria class in the phylum Proteobacteria. Multidrug resistant K. pneumoniae have caused major therapeutic problems worldwide due to emergence of extended-spectrum ß-lactamase producing strains. Two-component systems serve as a basic stimulus-response coupling mechanism to allow organisms to sense and respond to changes in many different environmental conditions including antibiotic stress. PRINCIPAL FINDINGS: In the present study, we investigated the role of an uncharacterized cpxAR operon in bacterial physiology and antimicrobial resistance by generating isogenic mutant (ΔcpxAR) deficient in the CpxA/CpxR component derived from the hyper mucoidal K1 strain K. pneumoniae NTUH-K2044. The behaviour of ΔcpxAR was determined under hostile conditions, reproducing stresses encountered in the gastrointestinal environment and deletion resulted in higher sensitivity to bile, osmotic and acid stresses. The ΔcpxAR was more susceptible to ß-lactams and chloramphenicol than the wild-type strain, and complementation restored the altered phenotypes. The relative change in expression of acrB, acrD, eefB efflux genes were decreased in cpxAR mutant as evidenced by qRT-PCR. Comparison of outer membrane protein profiles indicated a conspicuous difference in the knock out background. Gel shift assays demonstrated direct binding of CpxR(KP) to promoter region of ompC(KP) in a concentration dependent manner. CONCLUSIONS AND SIGNIFICANCE: The Cpx envelope stress response system is known to be activated by alterations in pH, membrane composition and misfolded proteins, and this systematic investigation reveals its direct involvement in conferring antimicrobial resistance against clinically significant antibiotics for the very first time. Overall results displayed in this report reflect the pleiotropic role of the CpxAR signaling system and diversity of the antibiotic resistome in hyper virulent K1 serotype K. pneumoniae NTUH-K2044.

Investigation of the toxic functional group of cephalosporins by zebrafish embryo toxicity test.

2-mercapto-5-methyl-1,3,4-thiadiazole (MMTD) is the 3'-side chain of cephalosporin including cefazolin sodium (CFZL) and cefazedone (CFZD). It is not only present in finished products as the residual precursor, but also produced through drug degradation. Performing the zebrafish embryo toxicity test, we evaluated the toxicity effects of cefazolin sodium, cefazedone, their synthetic precursors and intermediates. Our results suggest that the teratogenic effect of cefazedone and cefazolin sodium on zebrafish embryonic development is associated with the structure of MMTD. They mainly interfere with the development of tissues and organs derived from embryonic ectoderm and mesoderm. We further consider the rationality of the quality control limit of MMTD (1.0%) in the specification. As the acceptable daily intakes (ADIs) of cefazolin is 10 µg/kg per day 16 and the minimum teratogenic concentration of MMTD is tenfold lower than that of cefazolin sodium, we recommend that the acceptable daily intakes of MMTD should be 1 µg/(kg day). In general, the therapeutic dose of cefazolin sodium is 2-4 g/day. Based upon the calculation of MMTD quality control limits (1.0%), MMTD intake can be 20-40 mg/day, which will be much more than the acceptable daily intake value of 1 µg/(kg day). Thus, MMTD should be recommended as a specified impurity and qualified as serious again.