Pharmacokinetics and Target Attainment of Antimicrobial Drugs Throughout Pregnancy: Part I-Penicillins.

BACKGROUND AND OBJECTIVE: Pharmacokinetics (PK) are severely altered in pregnant women due to changes in volume of distribution (Vd) and/or drug clearance (CL), affecting target attainment of antibiotics in pregnant women. This review is part of a series that reviews literature on the description of PK and target attainment of antibiotics in pregnant women with specific focus on penicillins. METHODS: A systematic literature search was carried out in PubMed. Articles were labelled as relevant when information on PK of penicillins in pregnant women was available. RESULTS: Thirty-two relevant articles were included, 8 of which discussed amoxicillin (with and without clavulanic acid), 15 ampicillin, 4 benzylpenicillin, 1 phenoxymethylpenicillin, and 4 piperacillin (with and without tazobactam). No studies were found on pheneticillin and flucloxacillin in pregnant women. Ten out of 32 articles included information on both Vd and CL. During the second and third trimester of pregnancy, a higher CL and larger Vd was reported than in non-pregnant women and in pregnant women during first trimester. Reduced target attainment was described in second and third trimester pregnant women. Only 7 studies reported dosing advice, 4 of which were for amoxicillin. CONCLUSION: The larger Vd and higher CL in second and third trimester pregnant women might warrant a higher dosage or shortening of the dosing interval of penicillins to increase target attainment. Studies frequently fail to provide dosing advice for pregnant women, even if the necessary PK information was available.

High risk of early sub-therapeutic penicillin concentrations after intramuscular benzathine penicillin G injections in Ethiopian children and adults with rheumatic heart disease.

INTRODUCTION: Intramuscular benzathine penicillin G (BPG) injections are a cornerstone of secondary prophylaxis to prevent acute rheumatic fever (ARF) and rheumatic heart disease (RHD). Uncertainties regarding inter-ethnic and preparation variability, and target exposure profiles of BPG injection are key knowledge gaps for RHD control. METHODS: To evaluate BPG pharmacokinetics (PK) in patients receiving 4-weekly doses in Ethiopia, we conducted a prospective cohort study of ARF/RHD patients attending cardiology outpatient clinics. Serum samples were collected weekly for one month after injection and assayed with a liquid chromatography-mass spectroscopy assay. Concentration-time datasets for BPG were analyzed by nonlinear mixed effects modelling using NONMEM. RESULTS: A total of 190 penicillin concentration samples from 74 patients were included in the final PK model. The median age, weight, BMI was 21 years, 47 kg and 18 kg/m2, respectively. When compared with estimates derived from Indigenous Australian patients, the estimate for median (95% confidence interval) volume of distribution (V/F) was lower (54.8 [43.9-66.3] l.70kg-1) whilst the absorption half-life (t1/2-abs2) was longer (12.0 [8.75-17.7] days). The median (IQR) percentage of time where the concentrations remained above 20 ng/mL and 10 ng/mL within the 28-day treatment cycle was 42.5% (27.5-60) and 73% (58.5-99), respectively. CONCLUSIONS: The majority of Ethiopian patients receiving BPG as secondary prophylaxis to prevent RHD do not attain target concentrations for more than two weeks during each 4-weekly injection cycle, highlighting the limitations of current BPG strategies. Between-population variation, together with PK differences between different preparations may be important considerations for ARF/RHD control programs.

Pharmacokinetics and Target Attainment of Antibiotics in Critically Ill Children: A Systematic Review of Current Literature.

BACKGROUND: Pharmacokinetics (PK) are severely altered in critically ill patients due to changes in volume of distribution (Vd) and/or drug clearance (Cl). This affects the target attainment of antibiotics in critically ill children. We aimed to identify gaps in current knowledge and to compare published PK parameters and target attainment of antibiotics in critically ill children to healthy children and critically ill adults. METHODS: Systematic literature search in PubMed, EMBASE and Web of Science. Articles were labelled as relevant when they included information on PK of antibiotics in critically ill, non-neonatal, pediatric patients. Extracted PK-parameters included Vd, Cl, (trough) concentrations, AUC, probability of target attainment, and elimination half-life. RESULTS: 50 relevant articles were identified. Studies focusing on vancomycin were most prevalent (17/50). Other studies included data on penicillins, cephalosporins, carbapenems and aminoglycosides, but data on ceftriaxone, ceftazidime, penicillin and metronidazole could not be found. Critically ill children generally show a higher Cl and larger Vd than healthy children and critically ill adults. Reduced target-attainment was described in critically ill children for multiple antibiotics, including amoxicillin, piperacillin, cefotaxime, vancomycin, gentamicin, teicoplanin, amikacin and daptomycin. 38/50 articles included information on both Vd and Cl, but a dosing advice was given in only 22 articles. CONCLUSION: The majority of studies focus on agents where TDM is applied, while other antibiotics lack data altogether. The larger Vd and higher Cl in critically ill children might warrant a higher dose or extended infusions of antibiotics in this patient population to increase target-attainment. Studies frequently fail to provide a dosing advice for this patient population, even if the necessary information is available. Our study shows gaps in current knowledge and encourages future researchers to provide dosing advice for special populations whenever possible.

Fact versus Fiction: a Review of the Evidence behind Alcohol and Antibiotic Interactions.

Many antibiotics carry caution stickers that warn against alcohol consumption. Data regarding concurrent use are sparse. An awareness of data that address this common clinical scenario is important so health care professionals can make informed clinical decisions and address questions in an evidence-based manner. The purpose of this systematic review was to determine the evidence behind alcohol warnings issued for many common antimicrobials. The search was conducted from inception of each database to 2018 using PubMed, Medline via Ovid, and Embase. It included studies that involved interactions, effects on efficacy, and toxicity/adverse drug reactions (ADR) due to concomitant alcohol consumption and antimicrobials. All interactions were considered in terms of three components: (i) alteration in pharmacokinetics/pharmacodynamics (PK/PD) of antimicrobials and/or alcohol, (ii) change in antimicrobial efficacy, and (iii) development of toxicity/ADR. Available data support that oral penicillins, cefdinir, cefpodoxime, fluoroquinolones, azithromycin, tetracycline, nitrofurantoin, secnidazole, tinidazole, and fluconazole can be safely used with concomitant alcohol consumption. Data are equivocal for trimethoprim-sulfamethoxazole. Erythromycin may have reduced efficacy with alcohol consumption, and doxycycline may have reduced efficacy in chronic alcoholism. Alcohol low in tyramine may be consumed with oxazolidinones. The disulfiram-like reaction, though classically associated with metronidazole, occurs with uncertain frequency and with varied severity. Cephalosporins with a methylthiotetrazole (MTT) side chain or a methylthiodioxotriazine (MTDT) ring, ketoconazole, and griseofulvin have an increased risk of a disulfiram-like reaction. Alcohol and antimicrobial interactions are often lacking evidence. This review questions common beliefs due to poor, often conflicting data and identifies important knowledge gaps.

Evaluation of plasma concentration after intravenous and intramuscular penicillin administration over 24 hr in healthy adult horses.

Penicillin is administered intravenously (IV) or intramuscularly (IM) to horses for the prevention and treatment of infections, and both routes have disadvantages. To minimize these shortcomings, a 24-hr hybrid administration protocol (HPP) was developed. Our objective was to determine penicillin plasma concentrations in horses administered via HPP. Venous blood was collected from seven healthy horses administered IV potassium penicillin G at 0 and 6 hr and IM procaine penicillin G at 12 hr. Blood was collected at 2-hr intervals from 0 to 20 hr and at 24 hr. Plasma penicillin concentrations were measured using liquid chromatography and mass spectrometry. Penicillin susceptibility from equine isolates was examined to determine pharmacodynamic targets. The MIC90 of penicillin for 264 isolates of Streptococcus sp. was ≤0.06 µg/ml. For the 24-hr dosing interval, the mean plasma penicillin concentration was >0.07 µg/ml. Five horses (72%) exceeded 0.06 µg/ml for 98% of the dosing interval, and two horses exceeded this value for 52%-65% of the dosing interval. The HPP achieved mean plasma penicillin concentrations in healthy adult horses above 0.07 µg/ml for a 24-hr dosing interval. However, individual variations in plasma concentrations were apparent and deserve future clinical study.

Temocillin dosing in haemodialysis patients based on population pharmacokinetics of total and unbound concentrations and Monte Carlo simulations.

Objectives: To develop a population model describing temocillin pharmacokinetics (PK) in patients undergoing haemodialysis and investigate how pharmacokinetic/pharmacodynamic (PD) targets can be met with different dosage regimens. Patients and methods: Sixteen patients received the currently licenced dosing of 1, 2 or 3 g of temocillin (total of 61 doses) corresponding to an inter-dialytic period of 20, 44 or 68 h, respectively, and a dialysis period of 4 h. A non-linear mixed-effects model was developed jointly for total and unbound temocillin serum concentrations. The performance of clinically feasible dosing regimens was evaluated using a 5000-subject Monte Carlo (MC) simulation for determining the highest MIC for which the PK/PD target of 40%ƒT>MIC would be reached in 90% of patients [probability of target attainment (PTA)]. This PK study was registered at ClinicalTrials.gov (NCT02285075). Results: Temocillin unbound and total serum concentrations (429 samples) were used to fit an open two-compartment model with non-linear albumin binding and first-order elimination. In addition to total body clearance, dialysis clearance was modelled using the Michaels function. The currently licenced dosing achieved a 90% PTA for an MIC up to 8 mg/L. A new temocillin dosage regimen was designed that would achieve a 90% PTA for an MIC of 16 mg/L (MIC90 of target organisms) adjusted to patient weight and inter-dialytic period. Conclusions: Currently licensed dosage regimen is suboptimal for MICs >8 mg/L (frequently found in clinical isolates). Model-based simulations allowed suggestion of a new dosage regimen with improved probability of microbiological success, applicability in routine clinical practice and more appropriate for empirical therapy.

Pharmacokinetics and Pharmacodynamics of Temocillin.

Temocillin, a 6-α-methoxy derivative of ticarcillin, is a forgotten antibiotic that has recently been rediscovered, and issues about clinical breakpoints and optimal therapeutic regimens are still ongoing. Temocillin spectrum is almost restricted to Enterobacteriaceae. The addition of the α-methoxy moiety on ticarcillin confers resistance to hydrolysis by Ambler classes A and C ß-lactamases (extended spectrum ß-lactamases, Klebsiella pneumoniae carbapenemase and AmpC hyperproduced enzymes). Temocillin is bactericidal, and the effect of inoculum size on its activity is relatively mild. The proportion of spontaneous resistant mutants in vitro to temocillin is low, as found in vivo. After intravenous infusion, temocillin showed a prolonged elimination half-life of approximately 5 h. The percentage of protein binding of temocillin is high (approximately 80%), and is concentration-dependent. Temocillin clearance is mainly renal, and urinary recovery is high, ranging from 72 to 82% after 24 h. Furthermore, the penetration of temocillin into bile and peritoneal fluid is high, but poor into cerebrospinal fluid. The cumulative percentage of a 24-h period during which the free drug concentration exceeds the minimum inhibitory concentration (fT > MIC) at steady-state pharmacokinetic conditions seems to be the best pharmacokinetic/pharmacodynamic (PK/PD) index correlating with temocillin efficacy. An fT > MIC of 40-50% is associated with antibacterial effect and survival in vivo. Monte Carlo simulations performed in critically ill patients showed that the 2 g every 12 h and 2 g every 8 h regimens provide a 95% probability of target attainment of 40% fT > MIC up to an MIC of 8 mg/L. In less severely ill patients or in specific foci of infection, such as urinary tract infection, a 4 g daily regimen should be adequate for strains with temocillin MIC up to 16 mg/L. Data regarding actual wild-type MIC distribution, clinical efficacy, PK profiling in volunteers or patients, and PD targets are scarce, and further studies are required to support appropriate dosing recommendations and determination of clinical breakpoints.

What do I need to know about penicillin antibiotics?

The penicillins remain the class of antibiotics most commonly prescribed to children worldwide. In an era when the risks posed by antimicrobial resistance are growing, an understanding of antibiotic pharmacology and how to apply these principles in clinical practice is increasingly important. This paper provides an overview of the pharmacology of penicillins, focusing on those aspects of pharmacokinetics, pharmacodynamics and toxicity that are clinically relevant in paediatric prescribing. Penicillin allergy is frequently reported but a detailed history of suspected adverse reactions is essential to identify whether a clinically relevant hypersensitivity reaction is likely or not. The importance of additional factors such as antibiotic palatability, concordance and stewardship are also discussed, highlighting their relevance to optimal prescribing of the penicillins for children.

[Pharmacokinetics and pharmacodynamics of antibiotics in intensive care]. / Pharmakokinetik und Pharmakodynamik von Antibiotika in der Intensivmedizin.

Optimized dosage regimens of antibiotics have remained obscure since their introduction. During the last two decades pharmacokinetic(PK)-pharmacodynamic(PD) relationships, originally established in animal experiments, have been increasingly used in patients. The action of betalactams is believed to be governed by the time the plasma concentration is above the minimum inhibitory concentration (MIC). Aminoglycosides act as planned when the peak concentration is a multiple of the MIC and vancomycin seems to work best when the area under the plasma vs. time curve (AUC) to MIC has a certain ratio. Clinicians should be aware that these relationships can only be an indication in which direction dosing should go. Larger studies with sufficiently high numbers of patients and particularly severely sick patients are needed to prove the concepts. In times where all antibiotics can be measured with new technologies, the introduction of therapeutic drug monitoring (TDM) is suggested for ICUs (Intensive Care Unit). The idea of a central lab for TDM of antibiotics such as PEAK (Paul Ehrlich Antibiotika Konzentrationsmessung) is supported.

Interaction Between Low-Dose Methotrexate and Nonsteroidal Anti-inflammatory Drugs, Penicillins, and Proton Pump Inhibitors.

OBJECTIVE: To review the potential drug interactions between low-dose methotrexate (LD-MTX) and nonsteroidal anti-inflammatory drugs (NSAIDs), penicillins, and proton-pump inhibitors (PPIs) given the disparity between interactions reported for high-dose and low-dose MTX to help guide clinicians. DATA SOURCES: A literature search was performed in MEDLINE (1946 to September 2016), EMBASE (1974 to September 2016), and International Pharmaceutical Abstracts (1970 to January 2015) to identify reports describing potential drug interactions between LD-MTX and NSAIDS, penicillins, or PPIs. Reference lists of included articles were reviewed to find additional eligible articles. STUDY SELECTION AND DATA EXTRACTION: All English-language observational, randomized, and pharmacokinetic (PK) studies assessing LD-MTX interactions in humans were analyzed to determine clinical relevance in making recommendations to clinicians. Clinical case reports were assigned a Drug Interaction Probability Scale score. DATA SYNTHESIS: A total of 32 articles were included (28 with NSAIDs, 3 with penicillins, and 2 with PPIs [1 including both PPI and NSAID]). Although there are some PK data to describe increased LD-MTX concentrations when NSAIDs are used concomitantly, the clinical relevance remains unclear. Based on the limited data on LD-MTX with penicillins and PPIs, no clinically meaningful interaction was identified. CONCLUSION: Given the available evidence, the clinical importance of the interaction between LD-MTX and NSAIDs, penicillins, and PPIs cannot be substantiated. Health care providers should assess the benefit and risk of LD-MTX regardless of concomitant drug use, including factors known to predispose patients to MTX toxicity, and continue to monitor clinical and laboratory parameters per guideline recommendations.

Preliminary study of tissue concentrations of penicillin after local administration into the guttural pouches in four healthy horses.

BACKGROUND: Treatment of subclinical carriers of Streptococcus equi subsp. equi with a gelatine-penicillin formulation deposited in the guttural pouch has been empirically proposed, but data on local tissue penicillin concentrations after treatment are lacking. METHODS: We analysed tissue levels of penicillin after administration into the guttural pouches of four healthy horses. Two horses received local treatment with gelatine-penicillin and two horses received local treatment with an intramammary formulation of penicillin. Tissues were harvested for analysis either 12 or 24 h later. CONCLUSION: Results indicate that local treatment may be effective, but more research on optimal drug formulations in a larger sample size is warranted.

Activity of temocillin in a lethal murine model of infection of intra-abdominal origin due to KPC-producing Escherichia coli.

OBJECTIVES: Temocillin is a 6-α-methoxy derivative of ticarcillin that shows in vitro activity against Enterobacteriaceae producing Klebsiella pneumoniae carbapenemase (KPC). Our objective was to assess in vivo temocillin activity against KPC-producing Escherichia coli. METHODS: Isogenic derivatives of the WT E. coli CFT073 producing KPC-2, KPC-3 or OXA-48 were constructed. An experimental murine model of intra-abdominal infection with sepsis was used. Mice were treated subcutaneously with temocillin 200 mg/kg every 2 h for 24 h, reproducing the duration of time that the free serum concentration of temocillin exceeded the MIC in humans with a regimen of 2 g every 12 h or 2 g every 8 h. Blood, peritoneal fluid (PF) and spleen were collected; 24 h survival and sterility rates were assessed. RESULTS: Temocillin MICs were 8, 16, 32, and 256 mg/L for the susceptible strain and KPC-2-, KPC-3-, and OXA-48-producing strains, respectively. In mice treated with temocillin, significant bacterial reduction was obtained in PF, blood, and spleen for the susceptible strain and KPC-2- and KPC-3-producing strains (P < 0.001) but not for the OXA-48-producing strain. Sterility rates in PF were 53%, 10%, 0% and 0% (P < 0.001) and sterility rates in blood were 77%, 40%, 3% and 0% (P < 0.001), while survival rates were 97%, 97%, 57%, 0% (P < 0.001) for mice infected with the susceptible strain and KPC-2-, KPC-3- and OXA-48-producing strains, respectively. CONCLUSIONS: In a lethal-infection model with bacteraemia from intra-abdominal origin, temocillin retained significant activity in PF, blood and spleen and prevented death in mice by effectively working against KPC-producing E. coli with temocillin MICs ≤16 mg/L.

A Qualitative Review on the Pharmacokinetics of Antibiotics in Saliva: Implications on Clinical Pharmacokinetic Monitoring in Humans.

We conducted a systematic search to describe the current state of knowledge regarding the utility of saliva for clinical pharmacokinetic monitoring (CPM) of antibiotics. Although the majority of identified studies lacked sufficient pharmacokinetic data needed to assign an appropriate suitability classification, most aminoglycosides, fluoroquinolones, macrolides, penicillins/cephalosporins, and tetracyclines are likely not suitable for CPM in saliva. No clear pattern of correlation was observed between physiochemical properties that favor drug distribution into saliva and the likelihood of the antibiotic being classified as suitable for CPM in saliva (and vice versa). Insufficient data were available to determine if pathophysiological conditions affected salivary distribution of antibiotics. Additional confirmatory data are required for drugs (especially in patients) that are deemed likely suitable for CPM in saliva because only a few studies were available and many focused only on healthy subjects. All studies identified had relatively small sample sizes and exhibited large variability. Very few studies reported salivary collection parameters (e.g., salivary flow, pH) that could potentially have some impact on drug distribution into saliva. The available data are heavily weighted on healthy subjects, and insufficient data were available to determine if pathophysiology had effects on saliva drug distribution. Some studies also lacked assay sensitivity for detecting antibiotics in saliva. Overall, this review can be useful to clinicians who desire an overview on the suitability of saliva for conducting CPM of specific antibiotics, or for researchers who wish to fill the identified knowledge gaps to move the science of salivary CPM further.

Thrice-weekly temocillin administered after each dialysis session is appropriate for the treatment of serious Gram-negative infections in haemodialysis patients.

In patients with end-stage renal disease (ESRD) treated with intermittent haemodialysis, a limited number of antibiotics have been studied for their suitability for parenteral administration after dialysis sessions only in a thrice-weekly regimen. Temocillin is a ß-lactam antibiotic with a long half-live and enhanced activity against most Gram-negative bacteria, including extended-spectrum ß-lactamase-producers, thus making it an ideal candidate for use in this setting. This study aimed to evaluate the reliability of thrice-weekly parenteral temocillin in haemodialysis patients by characterising the pharmacokinetics of total and free temocillin. Free and total temocillin concentrations were determined with a validated HPLC method in 448 samples derived from 48 administration cycles in 16 patients with ESRD treated with intermittent haemodialysis and temocillin. Pharmacokinetics were non-linear partly due to saturation in protein binding. Median clearance and half-life for the free drug during intradialysis and interdialysis periods were 113 mL/min vs. 26 mL/min and 3.6 h vs. 24 h, respectively, with dialysis extracting approximately one-half of the residual concentration. The free temocillin concentration remained >16 mg/L (MIC90 threshold for most Enterobacteriaceae) during 48%, 67% and 71% of the dosing interval for patients receiving 1 g q24h, 2 g q48h and 3 g q72h, respectively, suggesting appropriate exposure for the two latter therapeutic schemes. Temocillin administered on dialysis days only in a dosing schedule of 2 g q48h and 3 g q72h is appropriate for the treatment of serious and/or resistant Gram-negative infections in patients with ESRD undergoing intermittent haemodialysis. These doses are higher than those previously recommended.

Minimal amounts of dipalmitoylphosphatidylcholine improve aerosol performance of spray-dried temocillin powders for inhalation.

Administration of antibiotics by inhalation can greatly improve drug targeting to the site of respiratory infections. In addition, dry powder inhalers are particularly convenient for the patients. The purposes of this study were to demonstrate the interest of pulmonary temocillin delivery to reach high temocillin concentrations locally in the lungs as well as to prepare a spray-dried temocillin powder for inhalation using a minimal amount of generally recognized as safe excipients. Intratracheal instillation of a temocillin solution allowed to reach higher and more sustained drug concentrations in the lungs than intravenous injection in mice, although a 10-fold lower temocillin dose was delivered intratracheally than systemically. A spray-dried powder of pure temocillin presented a fine particle fraction of 9% of the dose loaded in the inhaler. However, the incorporation of 0.5% to 20% of dipalmitoylphosphatidylcholine (DPPC) in the powder increased the fine particle fraction 4- to 5-fold. X-ray photoelectron spectroscopy and X-ray diffraction revealed that DPPC concentrated at the particle surface with its aliphatic chains laterally packed. The minimal amount of DPPC needed to improve the aerosol performance of temocillin supports the use of this excipient in the formulation of cohesive antibiotic powders for inhalation.

Recent Updates on the Role of Pharmacokinetics-pharmacodynamics in Antimicrobial Susceptibility Testing as Applied to Clinical Practice.

Given current challenges in antimicrobial resistance and drug development, infectious diseases clinicians must rely on their own ingenuity to effectively treat infections while preserving the current antimicrobial armamentarium. An understanding of pharmacokinetics (PK), pharmacodynamics (PD), antimicrobial susceptibility testing (AST), and how these concepts relate, is essential to this task. In this review, we discuss how and why PK-PD impacts AST and the way infectious diseases are being treated, with a particular focus on vancomycin for methicillin-resistant Staphylococcus aureus, penicillin for Streptococcus pneumoniae, and an update on cephalosporins for Enterobacteriaceae. Finally, we address how new ideas to exploit PK-PD can promote innovative study design and bring about more rapid regulatory review of new antimicrobials.

Sustained release of bactericidal concentrations of penicillin in the pleural space via an antibiotic-eluting pigtail catheter coated with electrospun nanofibers: results from in vivo and in vitro studies.

BACKGROUND: Inadequate intrapleural drug concentrations caused by poor penetration of systemic antibiotics into the pleural cavity is a major cause of treatment failure in empyema. Herein, we describe a novel antibiotic-eluting pigtail catheter coated with electrospun nanofibers used for the sustained release of bactericidal concentrations of penicillin in the pleural space. METHODS: Electrospun nanofibers prepared using polylactide-polyglycolide copolymer and penicillin G sodium dissolved in 1,1,1,3,3,3-hexafluoro-2-propanol were used to coat the surface of an Fr6 pigtail catheter. The in vitro patterns of drug release were tested by placing the catheter in phosphate-buffered saline. In vivo studies were performed using rabbits treated with penicillin either intrapleurally (Group 1, 20 mg delivered through the catheter) or systemically (Group 2, intramuscular injection, 10 mg/kg). Penicillin concentrations in the serum and pleural fluid were then measured and compared. RESULTS: In vitro studies revealed a burst release of penicillin (10% of the total dose) occurring in the first 24 hours, followed by a sustained release in the subsequent 30 days. Intrapleural drug levels were significantly higher in Group 1 than in Group 2 (P<0.001). In the former, penicillin concentrations remained above the minimum inhibitory concentration breakpoint throughout the entire study period. In contrast, serum penicillin levels were significantly higher in Group 2 than in Group 1 (P<0.001). Notably, all Group 2 rabbits showed signs of systemic toxicity (paralytic ileus and weight loss). CONCLUSION: We conclude that our antibiotic-eluting catheter may serve as a novel therapeutic option to treat empyema.

Highly sensitive bacterial susceptibility test against penicillin using parylene-matrix chip.

This work presented a highly sensitive bacterial antibiotic susceptibility test through ß-lactamase assay using Parylene-matrix chip. ß-lactamases (EC 3.5.2.6) are an important family of enzymes that confer resistance to ß-lactam antibiotics by catalyzing the hydrolysis of these antibiotics. Here we present a highly sensitive assay to quantitate ß-lactamase-mediated hydrolysis of penicillin into penicilloic acid. Typically, MALDI-TOF mass spectrometry has been used to quantitate low molecular weight analytes and to discriminate them from noise peaks of matrix fragments that occur at low m/z ratios (m/z<500). The ß-lactamase assay for the Escherichia coli antibiotic susceptibility test was carried out using Parylene-matrix chip and MALDI-TOF mass spectrometry. The Parylene-matrix chip was successfully used to quantitate penicillin (m/z: [PEN+H](+)=335.1 and [PEN+Na](+)=357.8) and penicilloic acid (m/z: [PA+H](+)=353.1) in a ß-lactamase assay with minimal interference of low molecular weight noise peaks. The ß-lactamase assay was carried out with an antibiotic-resistant E. coli strain and an antibiotic-susceptible E. coli strain, revealing that the minimum number of E. coli cells required to screen for antibiotic resistance was 1000 cells for the MALDI-TOF mass spectrometry/Parylene-matrix chip assay.