Concentrations Of Cefotaxime Research Articles

Effects of Bavistin and Cefotaxime on in vitro Contaminant free Shoot Regeneration of Ruellia tuberosa L.

In general, antimicrobial agents are often used in micropropagation techniques to obtain contaminant free clones. The objective of the present study was to evaluate the effects of bavistin and cefotaxime on producing contaminant free plants of Ruellia tuberosa cultured on MS supplemented with phytohormones. Field grown nodal explants of Ruellia tuberosa was used to regenerate entire plants via direct organogenesis. Among the decontaminants tested, the fungicide bavistin along with higher concentration of BAP (2.0 mg/l) and lower concentration of NAA (1.0 mg/l) was the most effective in regeneration and producing contaminant free shoots from cultured explants. This fungicide at 300 mg/l minimised fungal contamination with survival rate of 54%. While the addition of decontaminant cefotaxime at low concentration (200 mg/l) along with same concentration of BAP and NAA stimulated the bud formation and controlled the bacterial contamination. However, its increasing concentration adversely affected the survival rate of Ruellia tuberosa. These findings clearly showed that low concentrations of bavistin and cefotaxime were not only non-toxic but also facilitated bud regeneration. The results achieved showed the decisive role not only of the use of successful fungicides and antibiotics, but also of their sufficient doses were very important in reducing contamination and helping multiple shoot proliferation.
 Plant Tissue Cult. & Biotech. 31(1): 1-12, 2021 (June)

CSF concentration of cefotaxime in adult patients with pneumococcal meningitis: a multicentre retrospective study.

Pneumococcal meningitis is a devastating disease that requires adequate meningeal antibiotic penetration to limit the mortality. Despite a large usage in this indication, data about CSF concentration of cefotaxime during pneumococcal meningitis in adults are scarce. Therefore, we aimed to describe the CSF concentration obtained after high-dose cefotaxime administration in adult patients treated for Streptococcus pneumoniae meningitis. In this multicentre, observational, retrospective study, cases of adult patients with S. pneumoniae meningitis hospitalized between January 2013 and October 2019 for whom cefotaxime concentration was measured in CSF were reviewed. Cefotaxime concentration was analysed in 44 CSF samples collected among 31 patients. Median (IQR) age was 61 years (52-69). Dexamethasone was administered in 27 subjects. Median (IQR) cefotaxime daily dosage was 15 g (12-19), corresponding to 200 mg/kg (150-280). CSF samples were collected approximately 5 days after cefotaxime initiation. Median (IQR, range) cefotaxime CSF concentration was 10.3 mg/L (4.8-19.3, 1.2-43.4). Median (range) MIC for Streptococcus pneumoniae was 0.25 mg/L (0.008-1) (n = 22). The median (IQR, range) CSF/MIC ratio was 38 (12-146, 4-1844). Twenty-five CSF concentrations (81%) were above 10 times the MIC. Cefotaxime was discontinued in two patients for toxicity. In-hospital mortality rate was 29%. Adult patients with pneumococcal meningitis treated with a high dose of cefotaxime (200 mg/kg/day) had elevated CSF concentrations with satisfying pharmacokinetics/pharmacodynamics parameters and tolerability profile. This study brings reassuring pharmacological data regarding the use of high-dose cefotaxime monotherapy for treating pneumococcal meningitis with susceptible strains to cefotaxime.

Genetic Characterization of CTX-M-2-Producing Klebsiella pneumoniae and Klebsiella oxytoca Associated With Bovine Mastitis in Japan.

CTX-M-2-producing Klebsiella oxytoca (K. oxytoca) has not received much attention in animal husbandry compared with Klebsiella pneumoniae (K. pneumoniae), a major reservoir of extended-spectrum β-lactamase (ESBL) genes. Bacteriological examinations of 1,466 mastitic milk samples between October 2012 and December 2014 were conducted. Ninety-five K. pneumoniae isolates (total prevalence: 6.5%) and 81 K. oxytoca isolates (total prevalence: 5.5%) were obtained. Seventeen K. pneumoniae isolates obtained from 15 animals reared on 11 farms and 9 K. oxytoca isolates obtained from 9 animals reared on the same farm were phenotypically confirmed to be ESBL producers. All nine ESBL-producing K. oxytoca isolates were obtained from one farm between June and November 2013 and related to a significantly (p < 0.05) higher monthly prevalence of mild mastitis (in June, August, September, October, and November 2013). Pulsed-field gel electrophoresis (PFGE) patterns of ESBL-producing K. pneumoniae isolates were distinguished from each other by more than 6-band differences except for two isolates from two animals, whereas all nine K. oxytoca isolates showed an identical PFGE pattern. Transferability of the blaCTX−M−2 gene was found in 14 K. pneumoniae and 9 K. oxytoca isolates by conjugation analysis. Of these isolates, the blaCTX−M−2 gene was detected on plasmids belonging to the incompatibility (Inc) groups P and N derived from five K. pneumoniae and nine K. oxytoca isolates, respectively, although the plasmids from the remaining nine K. pneumoniae were untypeable. All the transconjugants exhibited elevated minimum inhibitory concentrations of ampicillin, cefotaxime, and ceftiofur compared with those in the wild-type, recipient strain. Restriction fragment length polymorphism analysis demonstrated that the IncN plasmids extracted from eight of nine transconjugants, which received resistance against β-lactams from K. oxytoca, showed an identical DraI digestion pattern. These results suggest that the CTX-M-2-producing K. oxytoca strain with the above-mentioned characteristics may have clonally spread within a farm, whereas the blaCTX−M−2 gene in K. pneumoniae possibly disseminated among the farms through different plasmids. Thus, monitoring of ESBL genes, including the blaCTX−M−2 gene, among causative agents of bacterial mastitis in cows can help to develop relevant treatments and control practices.

Effective Photodynamic Therapy with Ir(III) for Virulent Clinical Isolates of Extended-Spectrum Beta-Lactamase Klebsiella pneumoniae.

Background: The extended-spectrum beta-lactamase (ESBL) Klebsiella pneumoniae is one of the leading causes of health-associated infections (HAIs), whose antibiotic treatments have been severely reduced. Moreover, HAI bacteria may harbor pathogenic factors such as siderophores, enzymes, or capsules, which increase the virulence of these strains. Thus, new therapies, such as antimicrobial photodynamic inactivation (aPDI), are needed. Method: A collection of 118 clinical isolates of K. pneumoniae was characterized by susceptibility and virulence through the determination of the minimum inhibitory concentration (MIC) of amikacin (Amk), cefotaxime (Cfx), ceftazidime (Cfz), imipenem (Imp), meropenem (Mer), and piperacillin–tazobactam (Pip–Taz); and, by PCR, the frequency of the virulence genes K2, magA, rmpA, entB, ybtS, and allS. Susceptibility to innate immunity, such as human serum, macrophages, and polymorphonuclear cells, was tested. All the strains were tested for sensitivity to the photosensitizer PSIR-3 (4 µg/mL) in a 17 µW/cm2 for 30 min aPDI. Results: A significantly higher frequency of virulence genes in ESBL than non-ESBL bacteria was observed. The isolates of the genotype K2+, ybtS+, and allS+ display enhanced virulence, since they showed higher resistance to human serum, as well as to phagocytosis. All strains are susceptible to the aPDI with PSIR-3 decreasing viability in 3log10. The combined treatment with Cfx improved the aPDI to 6log10 for the ESBL strains. The combined treatment is synergistic, as it showed a fractional inhibitory concentration (FIC) index value of 0.15. Conclusions: The aPDI effectively inhibits clinical isolates of K. pneumoniae, including the riskier strains of ESBL-producing bacteria and the K2+, ybtS+, and allS+ genotype. The aPDI with PSIR-3 is synergistic with Cfx.

Antibiotic profile of enterobacter isolates from various clinical samples – A study from a tertiary care hospital

Introduction: Enterobacter species, especially Enterobacter cloacae are important nosocomial pathogens. They cause infections of the lower respiratory tract, skin, soft tissue, urinary tract and occasionally sepsis. Enterobacter species are often seen in natural habitats like water and soil. Enterobacter species are often resistant to various antibiotics in a hospital setting. Resistance to antimicrobials can also develop during therapy. The emergence of antimicrobial resistance, especially to third generation cephalosporins is a concern in the management of Enterobacter infections. Objectives: To evaluate the antimicrobial resistance pattern of Enterobacter species isolated from patients attending a tertiary care hospital. Materials and Methods: The present study was conducted in the Microbiology department of a tertiary care hospital. The study was conducted from January 2012 to December 2012. Enterobacter species were isolated from the clinical samples of patients using standard microbiological methods of bacterial culture and identification. Antibiotic susceptibility testing was done by Kirby-Bauer disc diffusion method, according to Clinical laboratory standard institute (CLSI) guidelines. Minimum inhibitory concentration (MIC) of cefotaxime was determined by the micro-broth dilution method. Results: During the study period, 100 isolates of Enterobacter species were isolated from clinical samples. The predominant species of Enterobacterisolated was Enterobacter cloacae(69%), followed by Enterobacter aerogenes (25%). Antibiotic susceptibility testing showed that most of the isolates were resistant to ampicillin (86%). The resistance to cefotaxime was 33%. Conclusion: Enterobacter species in a tertiary care setting could be resistant to common antibiotics like ampicillin and cephalosporins. Clinicians should be aware of these resistance pattern while choosing an empiric antibiotic regimen. Keywords: Enterobacter species, Enterobacter cloacae, Enterobacter aeroge

A New Aspect for In vitro Propagation of Jerusalem Artichoke and Molecular Assessment Using RAPD, ISSR and SCoT Marker Techniques

JERUSALEM artichoke is an important crop for a wide range of agricultural, medicinal and industrial purposes. Its tubers are rich in inulin and it is cultivated for food and animal feed. The current study aimed to develop an applicable protocol for micropropagation of three cultivars of Jerusalem artichoke (i.e., Balady, Fuza and Alba) using stem node explants. These explants were cultured on ½ MS medium augmented with different concentrations of kanamycin or cefotaxime. The lowest contamination correlated with highest survival percentages were recorded for ½ MS supplemented with 62.5mg L-1 cefotaxime. For shoot multiplication, the maximum number of shoots (11) were obtained for Alba cultivar cultured on MS fortified with 1mg L-1 BA + 0.1mg L-1 NAA + 50mg L-1 nano selenium. For rooting in vitro, the maximum values of rooting percent, root numbers/plantlet and length of roots were observed with ½ MS + 2mg L-1 IBA + 0.1mg L-1 NAA + 0.5mg L-1 KIN. Resulted in vitro regenerated plantlets, were acclimatized on perlite and peat moss mixture (1:1), which gave the highest percent of survival (100%) for Alba followed by Fuza and Balady (80 and 60%, respectively). Moreover, the molecular characterization based on RAPD, ISSR and SCoT techniques was carried out. The polymorphic percentages among in vivo shoots of the three cultivars recorded 38.09, 42.3 and 34.61%, respectively; 61.53, 67.8 and 50% between in vivo shoots, in vitro regenerates and stem derived calli of the three cultivars. The dendrogram analysis of combined techniques showed high similarity between Balady and Fuza followed by Alba.

Optimization of Agrobacterium-mediated transformation of perspective winter wheat genotypes in vitro

Aim. Optimization of conditions for genetic transformation of new perspective winter wheat genotypes. Methods. Agrobacterium-mediated transformation in culture in vitro. Results. The influence of the optical density of cells of the agrobacterial suspension, the concentration of the antibiotic cefotaxime, the duration of coculture on the frequency of obtaining kanamycin-resistant regenerants of new winter wheat genotypes by genetic transformation of callus cultures were investigated using LBA4404 and AGL0 strains. It is shown that depending on the strain the most optimal is the concentration of agrobacteria 0.2-03 OD, duration of coculture for 2-3 days and the use of cefotaxime at a concentration of 250-500 mg/L. Conclusions. The optimal parameters for conducting Agrobacterium-mediated transformation of callus cultures of new perspective winter wheat genotypes were selected.&#x0D; Keywords: Triticum aestivum, Agrobacterium-mediated transformation, callus cultures.

Genetic transformation of new perspective winter wheat genotypes in vitro

Aim. Optimization of conditions for genetic transformation of new perspective winter wheat genotypes and production of transgenic plants. Methods. Agrobacterium-mediated transformation in vitro culture using callus cultures. Results. The influence of the optical density of cells of agrobacterial suspension, the concentration of the antibiotic cefotaxime, the duration of coculture on the frequency of obtaining kanamycin-resistant regenerants of new winter wheat genotypes by genetic transformation of callus cultures were investigated. By Agrobacterium-mediated transformation of morphogenic calluses of new perspective winter wheat genotypes were obtained plant-regenerants in the genome of which revealed the complete incorporation of a genetic construct containing oat and nptII transgenes. Conclusions. Agrobacterium-mediated transformation of callus cultures of new perspective winter wheat genotypes was optimized, and transgenic plants with the target gene of ornithine-δ-aminotransferase were obtained.&#x0D; Keywords: Triticum aestivum, Agrobacterium-mediated transformation, callus cultures, ornithine-δ-aminotransferase gene.

The Influence of Aquaculture Effluents on the Prevalence and Biocides Resistance of Opportunistic Pseudomonas fluorescens Bacteria in the Drwęca River Protected under the Natura 2000 Network

The aim of this study was to determine the effect of trout aquaculture effluents on the Drwęca River. The count of opportunistic pathogen Pseudomonas fluorescens (OPPF) in the total Pseudomonas fluorescens population (TPFP) were determined by plating on King B medium and fluorescence in situ hybridization. The resistance of OPPF strains to 12 antibiotics and two disinfectants was evaluated. Significant differences (p ≤ 0.05) in OPPF counts were found between seven sampling sites. OPPF counts were highest in samples collected directly downstream from three fish farms. More than 50% of these isolates demonstrated multiple-drug resistance to ampicillin, mezlocillin, cefotaxime, norfloxacin, tetracycline and two disinfectants (Steridial and chloramine T). Of these, 52% were resistant to high doses of cefotaxime and norfloxacin (MIC ≥ 256 µg·mL−1), and 65% were resistant to the maximum doses of Steridial (MIC Ste ≥ 25 mL·m−3) and chloramine T (MIC Chlor ≥ 20 mg·L−1). All OPPF sampled upstream from the farms were sensitive to low concentrations of CTX (cefotaxime) and NOR (norfloxacin) (MIC ≤ 2 µg·mL−1), Steridial (MIC Ste ≤ 5 mL·m−3) and chloramine T (MIC Chlor ≤ 2.5 mg·L−1). Agglomerative clustering revealed two clusters: strains from samples collected upstream and downstream from trout farms. The results indicate that aquaculture effluents significantly affect the prevalence of biocides resistant OPPF along the river continuum.

New pharmacological effects of caripazim

The effects of a proteolytic enzyme found in papaya milk juice (caripazim) on the rate of lymphatic drainage of tissues and the pharmacokinetics of cefotaxime were studied in experiments on rabbits and mice. During the study, caripazim was administered to experimental animals, and the rate of removal of Evans blue from the mesentery of mice, as well as the concentration of cefotaxime over time in the blood plasma of rabbits and the blood plasma, intestinal tissues, and livers of mice, after 1.5 and 24 h of antibiotic administration following injection of caripazim, were determined. Thus, the lymphostimulatory properties of caripazim were revealed. Its preliminary administration increased the concentration of cefotaxime in the blood plasma of rabbits in comparison with single administration of an antibiotic at all points of the study (1.5, 3, 4.5, 6, 8, 12, and 24 h). This coincides with the data from the study of the level of antibiotic in the blood plasma of mice. Administration of cefotaxime after injection of caripazim leads to an increase in its content in the intestinal tissue, after both 1.5 and 24 h, but does not affect at the accumulation of the antibiotic in the liver. The concentration ratio liver tissue / blood in mice in the main group was significantly lower than that in the control group, both 1.5 and 24 h into the experiment, which indirectly indicates a decrease in hepatic antibiotic extraction. The data obtained indicates that caripazim has the properties of an endolymphatic conductor.

Persistence of wastewater antibiotic resistant bacteria and their genes in human fecal material.

Domestic wastewater is a recognized source of antibiotic resistant bacteria and antibiotic resistance genes (ARB&ARGs), whose risk of transmission to humans cannot be ignored. The fitness of wastewater ARB in the complex fecal microbiota of a healthy human was investigated in feces-based microcosm assays (FMAs). FMAs were inoculated with two wastewater isolates, Escherichia coli strain A2FCC14 (MLST ST131) and Enterococcus faecium strain H1EV10 (MLST ST78), harboring the ARGs blaTEM, blaCTX, blaOXA-A and vanA, respectively. The FMAs, incubated in the presence or absence of oxygen or in the presence or absence of the antibiotics cefotaxime or vancomycin, were monitored based on cultivation, ARGs quantification and bacterial community analysis. The fecal bacterial community was dominated by members of the phyla Firmicutes, Bacteroidetes, Actinobacteria, Proteobacteria and Verrucomicrobia. The ARGs harbored by the wastewater isolates could be quantified after one week, in FMAs incubated under both aerobic and anaerobic conditions. These observations were not significantly different in FMAs incubated anaerobically, supplemented with sub-inhibitory concentrations of cefotaxime or vancomycin. The observation that ARGs of wastewater ARB persisted in presence of the human fecal microbiota for at least one week supports the hypothesis of a potential transmission to humans, a topic that deserves further investigation.

Continuous versus intermittent infusion of cefotaxime in critically ill patients: a randomized controlled trial comparing plasma concentrations.

In critical care patients, reaching optimal β-lactam concentrations poses challenges, as infections are caused more often by microorganisms associated with higher MICs, and critically ill patients typically have an unpredictable pharmacokinetic/pharmacodynamic profile. Conventional intermittent dosing frequently yields inadequate drug concentrations, while continuous dosing might result in better target attainment. Few studies address cefotaxime concentrations in this population. To assess total and unbound serum levels of cefotaxime and an active metabolite, desacetylcefotaxime, in critically ill patients treated with either continuously or intermittently dosed cefotaxime. Adult critical care patients with indication for treatment with cefotaxime were randomized to treatment with either intermittent dosing (1 g every 6 h) or continuous dosing (4 g/24 h, after a loading dose of 1 g). We defined a preset target of reaching and maintaining a total cefotaxime concentration of 4 mg/L from 1 h after start of treatment. CCMO trial registration number NL50809.042.14, Clinicaltrials.gov NCT02560207. Twenty-nine and 30 patients, respectively, were included in the continuous dosing group and the intermittent dosing group. A total of 642 samples were available for analysis. In the continuous dosing arm, 89.3% met our preset target, compared with 50% in the intermittent dosing arm. Patients not reaching this target had a significantly higher creatinine clearance on the day of admission. These results support the application of a continuous dosing strategy of β-lactams in critical care patients and the practice of therapeutic drug monitoring in a subset of patients with higher renal clearance and need for prolonged treatment for further optimization, where using total cefotaxime concentrations should suffice.

The effect of endophytic bacteria on in vitro shoot growth of Prunus yedoensis and its identification and elimination

Tissue cultures of Prunus yedoensis, a famous ornamental tree species, are important to mass-propagate true-to-type plants. Within in vitro cultures, bacterial contamination of explants hinders the propagation of sustainable cultures. Negative effects of endophytic bacteria vary from leaf yellowing to shoot-tip necrosis, ultimately resulting in shoot death. Explants with an overgrowth of endophytic bacteria on basal parts showed inferior growth than explants with no bacterial growth. Shoot growth and contamination became severe as the shoots were subcultured. Two endophytic bacteria, Pantoea spp. and Curtobacterium spp., were identified from the in vitro shoots using 16S rRNA gene sequences. Bacterial susceptibility to antibiotics was screened using different antibiotics. Two antibiotics, cefotaxime and tetracycline, effectively controlled bacteria growth. Although both antibiotics killed the bacteria, tetracycline adversely affected plant growth by reducing shoot growth. A broad range of cefotaxime concentrations had no toxic effects to the in vitro plants. However, concentrations between 50 and 150 mg/L showed no difference in eliminating bacteria. Shoot growth, induction, and elongation were greater in a medium supplemented with cefotaxime compared with a control (without antibiotics) and a medium amended with tetracycline.

The Effects of Cytokinin and Auxin Interactions on Proliferation and Rooting of Seedless Grapevine (Vitis vinifera L.) cv. ‘Sultanine’

This research is carried out to produce Agrobacterium free rootstocks of seedless grapevine cv. ‘Sultanine’ through tissue culture to increase the quantity and quality of grape production in the country. In order to control bacterial contamination, four concentrations of cefotaxime in the combination with three concentrations of tetracycline were used for sterilization of explants (shoot tips and internode segments). After the establishment of the buds in MS medium, for node proliferation, four concentrations of BAP (0, 0.5, 1 and 1.5 mg l−1) in the combination with three concentrations of IBA (0, 0.25 and 0.5 mg l−1) were tested. The results showed the lowest bacterial contamination was obtained in the culture medium with 200 mg l−1 of cefotaxime in combination with 100 mg l−1 of tetracycline. The mean comparisons of growth regulators treatments showed that the highest proliferation (4.05 nodes per explant) and higher growth length (10.50 cm) obtained at 1.5 mg l−1 BAP plus 0.5 mg l−1 IBA treatment. Also the highest rooting percentage was 95% which obtained in the 1/2 MS containing 1 mg l−1 IBA. The PCR test using Agrobacterium specific primer pair indicated that the plant samples from tissue culture were free of Agrobacterium.

Changes in physiology and virulence during the selection of resistant Yersinia ruckeri mutants under subinhibitory cefotaxime concentrations.

Bacterial antibiotic resistance is one of the main healthcare problems currently. Apart from reducing antibiotic efficacy, it has awakened the interest of scientists due to its association with bacterial fitness and virulence. Interestingly, antibiotic resistance can be a source of both increased fitness and decreased fitness, even though the molecular basis of these relationships remains unknown. The aim of this work is to define the effects of sub-MIC concentrations of cefotaxime, an antibiotic extensively used in clinical practice, on the physiology and virulence of Yersinia ruckeri and to determine the importance of these sub-MIC concentrations for the selection of antibiotic-resistant mutants in the aquatic environment. Results indicated that exposure to sub-MIC concentrations of cefotaxime selected Y.ruckeri populations with irreversible alterations in the physiology, such as slow growth, aggregation in liquid cultures and modification of the colony morphology. These bacteria also displayed changes in the OMPs and LPS profiles and a full attenuation of virulence. An overexpression of the envelope stress regulator RpoE was also detected after exposure to the antibiotic. In conclusion, exposure to cefotaxime selected, at high frequency, Y.ruckeri strains that survive the antibiotic stress at the expense of a fitness cost and the loss of virulence.

Antibiotic Resistance of LACTOBACILLUS Strains.

The study provides phenotypic and molecular analyses of the antibiotic resistance in 20 Lactobacillus strains including 11 strains newly isolated from fermented plant material. According to the results of disc diffusion method, 90% of tested lactobacilli demonstrated sensitivity to clindamycin and 95% of strains were susceptible to tetracycline, erythromycin, and rifampicin. Ampicillin and chloramphenicol were found to inhibit all bacteria used in this study. The vast majority of tested strains revealed phenotypic resistance to vancomycin, ciprofloxacin, and aminoglycosides. Most of Lactobacillus strains showed high minimum inhibitory concentrations (MICs) of cefotaxime, ceftriaxone, and cefazolin and therefore were considered resistant to cephalosporins. All the strains exhibited multidrug resistance. The occurrence of resistance genes was associated with phenotypic resistance, with the exception of phenotypically susceptible strains that contained genes for tetracycline (tetK, tetL) and erythromycin (ermB, mefA) resistance. The vanX gene for vancomycin resistance was among the most frequently identified among the lactobacilli (75% of strains), but the occurrence of the parC gene for ciprofloxacin resistance was sporadic (20% of strains). Our results mainly evidence the intrinsic nature of the resistance to aminoglycosides in lactobacilli, though genes for enzymatic modification of streptomycin aadA and aadE were found in 20% of tested strains. The occurrence of extended spectrum beta-lactamases (ESBL) was unknown in Lactobacillus, but our results revealed the blaTEM gene in 80% of strains, whereas blaSHV and blaOXA-1 genes were less frequent (20% and 15% of strains, respectively).

An insight into analysis and elimination of plasmids encoding metallo-β-lactamases in Pseudomonas aeruginosa

ObjectivesThe aim of this study was to characterise metallo-β-lactamase (MBL)-harbouring plasmids, their change in copy number in respect to different antibiotic pressure, and the efficiency of different curing agents in eliminating these resistance plasmids from nosocomial Pseudomonas aeruginosa isolates. MethodsPlasmids were extracted from four isolates harbouring blaNDM-1 or blaVIM-2 under four different concentrations of imipenem, meropenem, ertapenem, aztreonam and cefotaxime. Quantitative real-time PCR was performed to analyse the change in plasmid copy number under these different conditions. The effect of different physical and chemical curing agents in elimination of plasmids carrying blaNDM-1 and blaVIM-2 was examined, with meropenem resistance used as a selectable marker. ResultsConjugatively transferable MBL genes (blaNDM-1 and blaVIM-2) carried on plasmids were found to be highly stable. Sodium dodecyl sulfate (SDS) was the most effective agent in eliminating these resistance plasmids. The change in copy number of the blaNDM-1-encoding plasmid was found to be similar to the blaVIM-2-encoding plasmid, with a single exception under cefotaxime pressure. ConclusionThe spread of multidrug resistance plasmids has been noted as a key factor associated with increasing carbapenem resistance. Successful curing of resistance plasmids can reverse the bacterial phenotype back to susceptible. This study revealed that different antibiotic pressure induces a change in copy number of MBL-encoding plasmids. SDS can be successfully used as an eliminating agent for these resistance determinants, although therapeutic application of this agent is not possible due to its high toxicity and mutagenic nature.

Antibiotic-Induced, Increased Conjugative Transfer Is Common to Diverse Naturally Occurring ESBL Plasmids in Escherichia coli.

Previously, we showed that cefotaxime (CTX) exposure increases conjugative transfer of a blaCTX–M–1 encoding IncI1 plasmid (IncI1/pST49/CTX-M-1) in Escherichia coli in a SOS-independent manner. This study aimed at investigating whether the observation was unique for that plasmid/strain/antibiotic combination or whether antibiotic-induced plasmid transfer (PT) is a more general phenomenon among plasmids in E. coli. Whole genome sequences of 25 E. coli strains were analyzed to identify different extended spectrum beta-lactamases (ESBL) plasmids enabling selection of a diverse collection of plasmids. Experiments were performed following exposure of these strains to 1/2 minimal inhibitory concentration (MIC) of CTX, ampicillin (AMP), or ciprofloxacin (CIP) before conjugation experiments. The frequency of PT was measured and compared to that of donors not exposed to antibiotics. Reverse-transcribed-quantitative real time polymerase chain reaction (RT-qPCR) was used to measure mRNA levels of five PT genes and two SOS response genes in donors exposed to antibiotics. The PT of eight strains (30.8% of strains tested) with IncI1/pST7/CTX-M-1, IncI1/pST49/CTX-M-1, IncI1/pST3/CTX-M-1, IncI1/pST293/CTX-M-1, IncI1/pST295/CTX-M-1, IncI1/pST16/CTX-M-55, and IncFII/CTX-M-14 (n = 2) plasmids was significantly increased following antibiotic exposure. CTX increased PT in all of these eight strain/plasmid combinations, AMP and CIP increased the PT in six and three strains, respectively. RT-qPCR showed that PT genes were up-regulated in the presence of the three antibiotics, whereas SOS-response genes were up-regulated only following CIP exposure. Our findings reveal that antibiotics can increase PT in E. coli strains with various ESBL plasmids. Thus, antibiotic-induced conjugative transfer of ESBL plasmids appears to be a common phenomenon in E. coli, having important implications for assessing the risks of antibiotic use.

Synergistic antibacterial mechanism of Bi2Te3 nanoparticles combined with the ineffective β-lactam antibiotic cefotaxime against methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) infections have become a serious threat to public health because traditional antibiotics are less efficient. Here, we developed a simple and efficient combination of Bi2Te3 nanoparticles (NPs) with β-lactam antibiotics cefotaxime (CTX), which presented significant synergistic antibacterial activity against MRSA. The minimal inhibitory concentration of CTX decreased from 256 to 32 μg/mL in the presence of 8 μg/mL Bi2Te3 NPs. The results of cell membrane potential and cellular K+ content measurements demonstrated that the destruction of membrane functions is a factor in the synergistic mechanism. Furthermore, the induction of cellular reactive oxygen species generation, inhibition of β-lactamases induced by CTX and direct damage to the cell structure constituted other factors of the synergistic mechanism. These observations suggest that reviving the efficacy of ineffective β-lactam antibiotic CTX by Bi2Te3 NPs may be a potentially effective therapeutic strategy to overcome refractory MRSA infections.

Target attainment of cefotaxime in critically ill children with meningococcal septic shock as a model for cefotaxime dosing in severe pediatric sepsis

Reduced target attainment of β-lactam antibiotics is reported in critically ill patients. However, as target attainment of cefotaxime in severely ill pediatric sepsis patients may differ from adults due to age-related variation in pharmacokinetics, we aimed to assess target attainment of cefotaxime in this pilot study using meningococcal septic shock patients as a model for severe sepsis. Secondary analysis of prospectively collected data from a randomized controlled trial. Children with meningococcal septic shock (1 month to 18 years) included in this study received cefotaxime 100–150 mg/kg/day as antibiotic treatment. Left-over plasma samples were analyzed using LC-MS/MS to determine cefotaxime concentrations. MIC values from EUCAST were used to determine target attainment of cefotaxime for Neisseria meningitidis (0.125 mg/l), but also for Streptococcus pneumoniae (0.5 mg/l), Enterobacteriaceae (1 mg/l), and Staphylococcus aureus (4 mg/l). Target attainment was adequate when all samples exceeded MIC or fourfold MIC values. One thirty-six plasma samples of 37 severe septic shock patients were analyzed for cefotaxime concentrations. Median age was 2 years with a median PRISM-score of 24 and mortality of 24.8%. The median unbound cefotaxime concentration was 4.8 mg/l (range 0–48.7). Target attainment ranged from 94.6% for the MIC of N. meningitidis to 16.2% for fourfold the MIC S. aureus. Creatinine levels were significantly correlated with cefotaxime levels. Target attainment of cefotaxime with current dosing guidelines seems to be adequate for N. meningitidis but seems to fail for more frequently encountered pathogens in severely ill children.