Biodegradation of bis(2-hydroxyethyl) terephthalate by a newly isolated Enterobacter sp. HY1 and characterization of its esterase properties

Bis(2-hydroxyethyl) terephthalate (BHET) is an important compound produced from poly(ethylene terephthalate) (PET) cleavage. It was selected as the representative substance for the study of PET degradation. A bacterial strain HY1 that could degrade BHET was isolated and identified as Enterobacter sp. The optimal temperature and pH for BHET biodegradation were determined to be 30°C and 8.0, respectively. The half-life of degradation was 70.20 h at an initial BHET concentration of 1,000 mg/L. The results of metabolites' analysis by liquid chromatograph–mass spectrometer revealed that BHET was first converted to mono-(2-hydroxyethyl) terephthalate (MHET) and then to terephthalic acid. Furthermore, an esterase-encoding gene, estB, was cloned from strain HY1, and the expressed enzyme EstB was characterized. The esterase has a molecular mass of approximately 25.13 kDa, with an isoelectric point of 4.68. Its optimal pH and temperature were pH 8.0 and 40°C, respectively. The analysis of the enzymatic products showed that EstB could hydrolyze one ester bond of BHET to MHET. To the best of authors' knowledge, this is the first report on the biodegradation characteristics of BHET by a member of the Enterobacter genus.     

Inpatient β-lactam test-dose protocol and antimicrobial stewardship in patients with a history of penicillin allergy

Background

Penicillin allergy is the most commonly reported drug allergy in hospitalized patients, resulting in increased second-line antibiotic use, nosocomial infections, and health care use. Given that most patients are not truly allergic, a safe strategy that empowers the admitting physician is needed.

β-Lactam Antibiotic Modulation of Murine Neutrophil Cytokinesis

Abstract

Fourteen cephalosporins, 11 penicillins and 1 monobactam were evaluated for their in vitro modulation of murine neutrophil cytokinesis. As a result, the β-lactam antibiotics were placed into 6 groups based on their effect on random (R) and FMLP-directed (D) migration [Group 1 (no effect) : cephalosporin C; Group 2 (R→D↓): cloxacillin, cefotaxime, ceftazadime, cefuroxime, cephalothin, cephapirin, cephadine, nafcillin, piperacillin, ticarcillin, ampicillin, oxacillin, aztreonam; Group 3 (R↑D→): cephaloridine; Group 4 (R↑D↑): cefsulodin; Group 5 (R↑D↓): cefoperazone, cefoxitin, ceftriaxone, 6-amino-penicillanic acid; Group 6 (R↓D↓): cefadroxil, cefazolin, penicillin G, methicillin]. Trypan blue exclusion studies showed that inhibition of R and D by Group 6 β-lactam antibiotics is not due to overt cytotoxicity. β-lactam antibiotics inhibiting D also increased neutrophil adherence to plastic at a concentration of 1000 μM. Finally, the [Ca⁺⁺] inhibitor chlorpromazine significantly abrogates β-lactam- and FMLP-directed migration at a test concentration of 1 μM.     

Differential effects of bismuth and salicylate salts on the antibiotic susceptibility ofPseudomonas aeruginosa

The influence of salicylate or bismuth salts on antibiotic action againstPseudomonas aeruginosa was assessed in broth cultures. Sodium salicylate (2.5 mM) had no significant effect on the activity of any antibiotic tested. In contrast, bismuth compounds (0.5 mM) produced a significant change in the inhibitory activity of several antibiotics against all strains. Bismuth salts reduced imipenem activity by up to 20-fold, enhanced gentamicin or amikacin activity three to five-fold, and enhanced cefpirome or cefepime activity by as much as 10-fold against antibiotic-sensitive and resistant strains. Bismuth salts had little effect on cefoperazone, ceftazidime, or mezlocillin activity. Combining bismuth salts with aminoglycosides or fourth-generation cephalosporin antibiotics may help to combat the growing problem of resistantPseudomonas aeruginosa.     

In vitro activity of seventeen antimicrobial agents againstGardnerella vaginalis

The in vitro activity of 17 antimicrobial agents was tested against 25 clinical isolates ofGardnerella vaginalis. Minimum inhibitory concentrations were determined by agar dilution. The isolates were sensitive to penicillin, ampicillin, ticarcillin, piperacillin, cephalothin, cefoxitin, cefotaxime, cefoperazone, N-formimidoyl-thienamycin, chloramphenicol, clindamycin and erythromycin. MIC₉₀ for theβ-lactam antibiotics ranged from 0.12 mg/l for penicillin to 2 mg/l for ticarcillin. Cefoperazone was the most active cephalosporin, inhibiting all isolates at 1.0 mg/l. N-formimidoyl-thienamycin was the most active of the newerβ-lactam compounds inhibiting all isolates with a concentration of 0.5 mg/l. Clindamycin and erythromycin were highly active, inhibiting all isolates at 0.6 mg/l. Susceptibility to tetracycline, gentamicin, metronidazole and tinidazole varied between strains. All isolates were resistant to rosoxacin. The hydroxy-metabolites of metronidazole and tinidazole were more active than the parent compounds, inhibiting all isolates     

Pharmacokinetic and microbial susceptibility studies of ceftriaxone

The in vitro activity of ceftriaxone, a new parenteral cephalosporin, was tested against 450 strains isolated from blood cultures and compared with that of various other antibiotics. The compound was comparable to cefotaxime for all species tested. Its was more potent than cefoperazone, cefamandole and ticarcillin in inhibitingEnterobacteriaceae (Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, indole-positiveProteus spp. andSerratia marcescens). The MIC₉₅ of ceftriaxone for these strains was 0.5Μg/ml. The drug was less active againstStaphylococcus aureus than cefamandole, cloxacillin and vancomycin, but most isolates were inhibited by 4Μg/ml. AgainstPseudomonas aeruginosa, ceftriaxone was comparable in activity to ticarcillin (MIC₉₅=64Μg/ml), and inferior to cefoperazone, ceftazidime and cefsulodine. Levels of ceftriaxone in serum and various body fluids were determined by bio-assays. Due to its very long half-life (8 h), ceftriaxone serum levels 24 h after i.v. or i.m. injection of 1 and 2 g were still above the MIC₉₅ of all strains tested exceptPseudomonas aeruginosa. Levels in bile, synovial and cerebro-spinal fluids were high.     

Impact of antibiotic administration on blood culture positivity at the beginning of sepsis: a prospective clinical cohort study

Objectives

Sepsis guidelines recommend obtaining blood cultures before starting anti-infective therapy in patients with sepsis. However, little is known of how antibiotic treatment before sampling affects bacterial growth. The aim of this study was to compare the results of blood cultures drawn before and during antibiotic therapy.

Pharmacodynamic modelling of β-lactam/β-lactamase inhibitor checkerboard data: illustration with aztreonam–avibactam

Objectives

Checkerboard experiments followed by fractional inhibitory concentration (FIC) index determinations are commonly used to assess in vitro pharmacodynamic interactions between combined antibiotics, but FIC index cannot be determined in case of antibiotic/non-active compound combinations. The aim of this study was to use a simple modelling approach to quantify the in vitro activity of aztreonam-avibactam, a new β-lactam–β-lactamase inhibitor combination.

THE ROLE OF ACTIVE EFFLUX IN ANTIBIOTIC-RESISTANCE OF CLINICAL ISOLATES OF HELICOBACTER PYLORI

Purpose: In gram-negative bacteria, active efflux pumps that excrete drugs can confer resistance to antibiotics however, in Helicobacter pylori this role is not well established. The purpose of this study is to evaluate the role of active efflux in resistance of H. pylori isolates to antibiotics. Materials and Methods: Twelve multiple antibiotic resistant (MAR) isolates resistant to at least four antibiotics, including β-lactams, metronidazole, tetracycline, erythromycin, and ciprofloxacin; three resistant to only β-lactams, and two hyper-susceptible isolates, were obtained from screening of 96 clinical isolates of H. pylori. Their minimal inhibitory concentrations (MICs) for antibiotics and ethidium-bromide (EtBr) were compared in the presence-and absence of a proton-conductor, carbonyl cyanide-m chlorophenyl-hydrazone (CCCP) using agar-dilution and disc diffusion. Drug accumulation studies for EtBr and antibiotics were assessed in the presence and absence of CCCP using spectrofluorometry. Results: MIC of EtBr for eight MAR-isolates was decreased two- to four-folds in the presence of CCCP, of which five showed reduced MICs for β-lactam, metronidazole, tetracycline, and ciprofloxacin with CCCP. Accumulation of EtBr by the MAR-isolates was rapid and not dependant on the pattern of multiple resistance. Antibiotic accumulation assay confirmed the presence of energy-dependant efflux of β-lactam, metronidazole, tetracycline, and ciprofloxacin, but no erythromycin in five MAR isolates. Energy-dependant efflux of EtBr or antibiotics was not observed for four MAR-isolates, and three isolates were resistant only to β-lactams. Conclusion: Energy-dependant efflux plays a role in the resistance of H. pylori clinical isolates to structurally unrelated antibiotics in a broadly specific multidrug efflux manner. Difference in the efflux potential of MAR isolates may be related to the presence or absence of functional efflux-pumps in diverse H. pylori isolates.     

Beta-Lactam Antibiotic Sensitization and Its Relationship to Allergic Diseases in Tertiary Hospital Nurses

Purpose

Skin allergies through type 1 and 4 hypersensitivity reactions are the most frequent manifestations of drug allergies. We had previously experienced a case of a nurse with cefotiam-induced contact urticaria syndrome. To aid in preventing the progression of drug-induced allergic disease in nurses, we conducted a survey of tertiary hospital nurses who were likely to have been exposed professionally to antibiotics.

Methods

All 539 staff nurses at a tertiary hospital were asked to respond to a questionnaire regarding antibiotic exposure. Of the 457 nurses (84.8%) who responded, 427 (79.2%) received a physical examination of the hands and 318 (59.0%) received skin prick tests with the β-lactam antibiotics cefotiam, cefoperazone, ceftizoxime, flomoxef, piperacillin and penicillin G.

Results

A positive response to at least one of the antibiotics occurred in 8 (2.6%) of the 311 subjects included in the analysis and stages 1 and 2 contact urticaria syndrome were observed in 38 (8.9%) and 3 (0.7%) of 427 nurses, respectively. The frequencies of a positive antibiotic skin test (6.9 versus 1.3%, χ²=7.15, P=0.018), stage 1 contact urticaria syndrome (14.4 versus 7.4%, χ²=4.33, P=0.038) and drug allergy (15.3 versus 3.6%, χ²=18.28, P=0.000) were higher in subjects with a positive skin allergy history than in those without. Allergic rhinitis (P=0.02, OR=3.86, CI=1.23-12.06), night cough (P=0.04, OR=3.12, CI=1.03-9.41) and food allergy (P=0.00, OR=9.90, CI=3.38-29.98) were significant risk factors for drug allergy.

Conclusions

Antibiotic sensitization and drug allergy occurred more frequently in nurses with a positive skin allergy history. Atopy may be an important risk factor for drug allergy.     

Antibiotic choice and methicillin-resistant Staphylococcus aureus rate in children hospitalized for atopic dermatitis

Background

Systemic antibiotics are commonly used in hospitalized patients with severe atopic dermatitis (AD) exacerbation. However, the antibiotic prescribing patterns are unclear.

Development of a combination antibiogram for empirical treatments of Pseudomonas aeruginosa at a university-affiliated teaching hospital

IntroductionThe significantly higher mortality rate in the critical illness patients with Pseudomonas aeruginosa (PA) infection is linked to inappropriate selecting of empirical treatment. Traditional local antibiogram provides clinicians the resistant rate of a single antimicrobial agent to the pathogen in the specific setting. The information is valuable to the clinicians in selecting suitable empirical antibiotic therapy. However, traditional local antibiogram can only provide information for single agent empirical antibiotic not combination regimens. The combination antibiogram should be developed to facilitate the selection of appropriate antibiotics to broader the coverage rate of resistant PA.MethodsThe susceptibility to the β-lactam antibiotics (piperacillin/tazobactam (PTZ), ceftazidime, cefepime, imipenem, or meropenem) or to those administered in combination with an aminoglycoside (gentamicin or amikacin) or fluoroquinolone (ciprofloxacin or levofloxacin) was calculated. The chi-square test was used to compare the differences of combination coverage rates between non-ICU and ICU isolates.Results880 PA isolates were isolated during study period. The susceptibility of single agents ranged from 83.1% to 89.7%. The combination regimens containing amikacin provide the highest cover rate (98.9%–99.1%) and those containing levofloxacin provide less coverage rate (92.3%–93.9%). The susceptibility to five β-lactam single agents in ICU isolates significantly lower than non-ICU isolates. The non-ICU isolates exhibited significantly higher susceptibility to the PTZ–gentamicin (p = 0.002) and ceftazidime–gentamicin (p = 0.025) than ICU isolates.ConclusionOur results support the use of aminoglycosides instead of fluoroquinolones as additive agents in empirical combination treatments for patients with critical infections caused by PA.     

Influence of subinhibitory concentrations of antibiotics on opsonization and phagocytosis ofPseudomonas aeruginosa by human polymorphonuclear leukocytes

To determine whether pretreatingPseudomonas aeruginosa with antibiotics had an effect on phagocytosis, a serum-resistant clinical isolate was incubated with one-third of the minimum inhibitory concentrations of azlocillin, carbenicillin, cefoperazone, fosfomycin, netilmicin and piperacillin respectively prior to exposure to human polymorphonuclear leukocytes. The phagocytic process was measured by assaying radiolabeled bacteria. The uptake rates of untreated and antibiotic treated bacteria did not differ when normal human serum was used for opsonization. However, when the serum was heated to inactivate the complement system, its opsonic activity for untreated as well as for fosfomycin and netilmicin treated pseudomonas was removed and phagocytosis did not take place. In contrast, bacteria pretreated with the betalactam antibiotics still underwent phagocytosis, as also confirmed by electron microscopy. Even in the presence of rabbit immune serum untreated bacteria still required the participation of the complement system for optimal opsonization, whereas bacteria treated withβ-lactam antibiotics did not.     

Evaluation of antibiotic use in Pediatric Intensive Care Unit of a developing country

Background:Pediatric Intensive Care Unit (PICU) patients are often prescribed antibiotics with a low threshold in comparison to patients elsewhere. Irrational antibiotics use can lead to rapid emergence of drug resistance, so surveillance of their use is important.Objectives:To evaluate the use of antibiotics in relation to bacteriological findings in PICU of a Tertiary Hospital.Methods:Retrospective review of medical records of all children (age 1 month–16 years) admitted in our closed multidisciplinary-cardiothoracic PICU from January to June 2013 was performed, after approval from Ethical Review Committee. For each antibiotic, indication (prophylactic, empiric, therapeutic) and duration of use were recorded. All diagnoses of infections were recorded according to diagnostic criteria of IPSCC 2005. Results are presented as frequency and percentages and median with inter quartile range using SPSS version 19.Results:All of the total 240 patients admitted in PICU during the study period received antibiotics: 43% (n = 104) prophylactically, 42% (n = 102) empirically, and 15% (n = 15) therapeutically. Median number of antibiotic use per patient in PICU was 3, with range of 1–7. 25% received 1 antibiotic, 23% received 2 antibiotics, 29% received 3 antibiotics, and rest received ≥4 antibiotics. Most commonly used antibiotics were cefazolin, meropenem, vancomycin and ceftriaxone, and most frequently used combination was meropenem and vancomycin. In majority of the cases, (70%) empiric antibiotic combinations were stopped in 72 h.Conclusion:This is the first report of antibiotics use in PICU from our country, which shows that antibiotics are prescribed universally in our PICU. Strategies to assess the need for antibiotic use are needed.     

Understanding the microbiome of diabetic foot osteomyelitis: insights from molecular and microscopic approaches

Objectives

Rigorous visual evidence on whether or not biofilms are involved in diabetic foot osteomyelitis (DFO) is lacking. We employed a suite of molecular and microscopic approaches to investigate the microbiome, and phenotypic state of microorganisms involved in DFO.

Cephalosporin and fluoroquinolone combinations are highly associated with CTX-M β-lactamase-producing Escherichia coli: a case–control study in a French teaching hospital

The aim of this study was to investigate the risk factors associated with CTX-M-producing Escherichia coli strains isolated from infected or colonized patients. From 191 clinical samples, a case–control study was designed. From January 2005 to December 2007, 98 hospitalized patients infected or colonized with CTX-M-producing E. coli were included in the study. They were matched 1 : 1 with controls that had a non-CTX-M-producing E. coli infection on the basis of the site of sample, the unit of hospitalization and the time at risk. The rate of CTX-M-producing E. coli among those producing extended spectrum β-lactamases was always ≥90% from 2005 to 2008. All strains were susceptible to carbapenems. However, we observed a high rate of co-resistance to ciprofloxacin (61%), sulphonamides (86%) and gentamicin (34%). Significant risk factors identified by multivariate analysis were recurrent infections (OR = 2.93), presence of artificial nutrition (OR = 3.99), and recent exposure to quinolones (OR = 4.39), third- or fourth-generation cephalosporin (OR = 3.49) and the combination of both antibiotic classes (OR = 5.50). This report highlights the dramatic increase of CTX-M-producing E. coli and the need for changes in the use of antimicrobial drugs and in infection control measures to manage this major health concern.     

Predictors of polymyxin B treatment failure in Gram-negative healthcare-associated infections among critically ill patients

Background

With increasing prevalence and spread of multidrug resistant Gram-negative infections, parenteral polymyxins resurged in clinical practice. The primary aim of the study was to determine the predictors of treatment failure and in-hospital mortality among critically ill patients treated with polymyxin B.

Reappraisal of parenteral antimicrobial therapy for nontyphoidal Salmonella enteric infection in children

Increasing antimicrobial resistance in nontyphoidal Salmonella (NTS) species complicates the use of antibiotics if indicated. We investigated the impact of antimicrobial resistance on clinical outcomes and discussed how to use antibiotics rationally. Hospitalized children in 2005–2006 with stool cultures positive for NTS were identified. The clinical and microbiological features were retrospectively reviewed. A total of 683 children were included [371 (54.3%) male; 89.5% <5 years of age]. Antibiotics were given to 56.5% of the patients; third-generation cephalosporin was the most commonly used drug class. Cases receiving antibiotics that were inactive in vitro did not have more complications than those receiving antibiotics active in vitro. Complications occurred in 7.9% of the patients, with bacteraemia being the most common (57.4%). Compared to the others, patients with longer febrile duration and higher C-reactive protein (CRP) levels (CRP ≥100 mg/L) were more frequently put on empirical antimicrobial therapy and had more complications. These patients usually had shorter hospitalization and duration of fever if antimicrobial agents that can reach high tissue concentrations in the intestinal mucosa were administered, such as fluoroquinolone or ceftriaxone. It is concluded that adequate antibiotics may be clinically beneficial to a subset of patients with high CRP and longer duration of fever among children with NTS enteritis. To prevent the induction of antibiotic resistance from this therapy, we suggested a short course (3–5 days) of intravenous ceftriaxone for such patients, which would lead to a faster clinical recovery.