Serum Antibiotic Concentrations Research Articles

Free serum concentrations of antibiotics determined by ultrafiltration: extensive evaluation of experimental variables.

Aim: To assess the impact of experimental conditions on free serum concentrations as determined by ultrafiltration and HPLC-DAD analysis in a wide range of antibiotics. Materials & methods: Relative centrifugation force (RCF), temperature, pH and buffer were varied and the results compared with the standard protocol (phosphate buffer pH 7.4, 37°C, 1000×g). Results: Generally, at 10,000×g the unbound fraction (fu) decreased with increasing molecular weight, and was lower at 22°C. In unbuffered serum, the fu of flucloxacillin or valproic acid was increased, that of basic or amphoteric drugs considerably decreased. Comparable results were obtained using phosphate or HEPES buffer except for drugs which form metal chelate complexes. Conclusion: Maintaining a physiological pH is more important than strictly maintaining body temperature.

510 Antibiotic Serum Concentrations in Burn Patients with Augmented Renal Clearance and Adjusted Regimens

510 Antibiotic Serum Concentrations in Burn Patients with Augmented Renal Clearance and Adjusted Regimens

A comparison of aminoglycoside antibiotic serum concentrations collected by peripheral veins and peripherally inserted central catheters in adults with cystic fibrosis.

People with cystic fibrosis (PwCF) are frequently hospitalized for treatment of pulmonary exacerbation. The Cystic Fibrosis Foundation Pulmonary Guidelines support the use of intravenous aminoglycosides with therapeutic drug monitoring for the treatment of pulmonary exacerbation due to Pseudomonas aeruginosa. Serum intravenous tobramycin concentrations are commonly collected by peripheral venipuncture (PV). Discomfort associated with collection of samples by PV prompts collection via PICC, but the accuracy of intravenous tobramycin serum levels collected by PICC has not been documented in adult PwCF. The primary study objective was to evaluate the difference between intravenous tobramycin serum levels collected by PV and PICC in adult PwCF. The authors conducted a prospective case-control study of adult PwCF admitted to University of Utah Health for a pulmonary exacerbation receiving tobramycin by a single lumen PICC. The authors compared tobramycin peak and random serum levels collected by PV and PICC using a detailed flush and waste protocol. The authors analyzed a total of 19 patients with peripheral and PICC samples. The mean tobramycin peak collected by PV (27.2 mcg/mL) was similar to the mean peak collected by PICC (26.9 mcg/mL) (paired samples Wilcoxon signed-rank test, p = .94). The correlation coefficient was 0.88 (95% CI = 0.85-0.91, p < .001). Tobramycin serum samples collected by PICC appear to be similar in value to PV collections. Collecting aminoglycoside levels by PICC rather than PV may reduce patient discomfort and improve quality of life. Additional multicenter studies are needed to confirm these results.

Liquid chromatography–tandem mass spectrometry methods for quantification of total and free antibiotic concentrations in serum and exudate from patients with post-sternotomy deep sternal wound infection receiving negative pressure wound therapy

BackgroundSystemically administered antibiotics are thought to penetrate the wounds more effectively during negative pressure wound therapy (NPWT).To test this hypothesis total and free antibiotic concentrations were quantified in serum and wound exudate. MethodsUHPLC-MS/MS methods were developed and validated for the determination of ceftazidime, cefepime, cefotaxime, cefuroxime, cefazolin, meropenem, oxacillin, piperacillin with tazobactam, clindamycin, ciprofloxacin, sulfamethoxazole/trimethoprim (cotrimoxazole), gentamicin, vancomycin, and linezolid. The unbound antibiotic fraction was obtained by ultrafiltration using a Millipore Microcon-30kda Centrifugal Filter Unit. Analysis was performed on a 1.7-µm Acquity UPLC BEH C18 2.1 × 100-mm column with a gradient elution. ResultsThe validation was performed for serum, exudates and free fractions. For all matrices, requirements were met regarding linearity, precision, accuracy, limit of quantitation, and matrix effect. The coefficient of variation was in the range of 1.2–13.6%.and the recovery 87.6–115.6%, respectively. Among the 29 applications of antibiotics thus far, including vancomycin, clindamycin, ciprofloxacin, oxacillin, cefepime, cefotaxime, cotrimoxazole, and gentamicin, total and free antibiotic concentrations in serum and exudate were correlated. ConclusionThis method can accurately quantify the total and free concentrations of 16 antibiotics. Comparison of concentration ratios between serum and exudates allows for monitoring individual antibiotics' penetration capacity in patients receiving NPWT.

Microdialysis as a tool for antibiotic assessment in patients with diabetic foot: a review.

Diabetic foot is a serious late complication frequently caused by infection and ischaemia. Both require prompt and aggressive treatment to avoid lower limb amputation. The effectiveness of peripheral arterial disease therapy can be easily verified using triplex ultrasound, ankle-brachial/toe-brachial index examination, or transcutaneous oxygen pressure. However, the success of infection treatment is difficult to establish in patients with diabetic foot. Intravenous systemic antibiotics are recommended for the treatment of infectious complications in patients with moderate or serious stages of infection. Antibiotic therapy should be initiated promptly and aggressively to achieve sufficient serum and peripheral antibiotic concentrations. Antibiotic serum levels are easily evaluated by pharmacokinetic assessment. However, antibiotic concentrations in peripheral tissues, especially in diabetic foot, are not routinely detectable. This review describes microdialysis techniques that have shown promise in determining antibiotic levels in the surroundings of diabetic foot lesions.

Antimicrobial Pharmacokinetics and Pharmacodynamics in Critical Care: Adjusting the Dose in Extracorporeal Circulation and to Prevent the Genesis of Multiresistant Bacteria

Critically ill patients suffering from severe infections are prone to pathophysiological pharmacokinetic changes that are frequently associated with inadequate antibiotic serum concentrations. Minimum inhibitory concentrations (MICs) of the causative pathogens tend to be higher in intensive care units. Both pharmacokinetic changes and high antibiotic resistance likely jeopardize the efficacy of treatment. The use of extracorporeal circulation devices to support hemodynamic, respiratory, or renal failure enables pharmacokinetic changes and makes it even more difficult to achieve an adequate antibiotic dose. Besides a clinical response, antibiotic pharmacokinetic optimization is important to reduce the selection of strains resistant to common antibiotics. In this review, we summarize the present knowledge regarding pharmacokinetic changes in critically ill patients and we discuss the effects of extra-corporeal devices on antibiotic treatment together with potential solutions.

Pharmacokinetics of Teicoplanin in a Patient with Coronavirus Disease 2019 Receiving Veno-venous Extracorporeal Membrane Oxygenation.

Patients with severe coronavirus disease 2019 (COVID-19) receiving ventilation or pulmonary support via veno-venous extracorporeal membrane oxygenation (VV-ECMO) can be infected with drug-resistant bacteria. When introducing VV-ECMO, the changes in serum antibiotic concentration should be considered due to an increased volume of distribution (Vd). However, no pharmacokinetic study has assessed teicoplanin (TEIC) treatment in patients with COVID-19 receiving VV-ECMO. A 71-year-old man diagnosed with COVID-19 visited a primary hospital. His oxygenation conditions worsened despite treatment with favipiravir and methylprednisolone as well as oxygen therapy. After his transfer to our center, tracheal intubation and steroid pulse therapy were initiated. Seven days after admission, VV-ECMO was performed. TEIC was administered for secondary bacterial infection. The serum TEIC concentration remained within the therapeutic range, indicating that VV-ECMO did not significantly affect TEIC pharmacokinetics. VV-ECMO was discontinued 17 days after admission. However, he developed multi-organ disorder and died 42 days after admission. As TEIC prevents viral invasion, it may be used with ECMO in patients with COVID-19 requiring ventilation; however, the altered pharmacokinetics of TEIC, such as increased Vd, should be considered. Therefore, TEIC pharmacokinetics in VV-ECMO should be assessed in future studies with an appropriate number of patients.

Treatment of long bone infection by a biodegradable bone cement releasing antibiotics in human.

Repair of methicillin-resistant Staphylococcal (MRSA) chronic osteomyelitis and resulting bone defect is one of the major challenges in orthopaedics. Previous study has shown the effectiveness of antibiotic loaded biodegradable composite bone cement with in vitro tests and in the treatment of experimental osteomyelitis. The cement is composed of poly(lactide-co-glycolide) encapsulated antibiotic-biphasic calcium phosphate granule complex and additive antibiotic powder in gypsum binder. In this study, the cement was studied further to evaluate its in vitro biological properties (cytocompatibility, platelet activation), anti-infective, and bone regenerative potential in comparison to poly(methyl methacrylate) (PMMA) cement and parenteral therapy in 43 patients (age 5-57years) with chronic MRSA osteomyelitis by analyzing the results of histopathology, radiographs, magnetic resonance imaging, scanning electron microscopy, and serum drug concentrations for 1year. The composite cement showed superior cytocompatibility and coagulant activity compared to PMMA cement. Moreover, the results of different postoperative clinical and radiological examinations also proved the supremacy of composite cement over the other treatment modalities in terms of success rate, faster sepsis control and bone regeneration. Low serum antibiotic concentrations and normal serum calcium levels indicate that the calcium-rich composite cement is safe for application in human. Therefore, we conclude that the composite bone cement is a promising candidate for the treatment of chronic osteomyelitis.

Influence of intraoperative fluid replacement on ampicillin serum levels and surgical site infections

BackgroundSurgical site infections (SSI) occur despite antimicrobial prophylaxis and increase postoperative morbidity and mortality. This could be caused by an intraoperative decrease in antibiotic serum concentrations such as ampicillin after major abdominal surgery due to blood loss and fluid therapy, which possibly promotes SSI. This hypothesis was tested in the present study. MethodsThis pilot study was performed as a prospective observational trial between March 2018 and May 2019. Ampicillin/sulbactam was administered intravenously during anesthesia induction. Fluid replacement was guided based on hemodynamic variables, including analysis of pulse pressure variation. The primary outcome was ampicillin serum level (ASL), measured after administration and hourly within 4 hours. The incidence of SSI at hospital discharge was the secondary outcome. Linear mixed and logistic regression models were used for statistical analyses. ResultsAfter screening of 133 adult patients, 129 were enrolled, and 102 completed the study protocol. No correlation was found between the volume of intraoperative fluids and ASL, nor was any association found between ASL and SSI. Based on 5 SSI cases, SSI were associated with higher intraoperative fluid volume. ASL was sufficient to provide intraoperative coverage for all potential bacterial strains. ConclusionIntraoperative fluid replacement had no effect on ASL up to 4 hours after ampicillin/sulbactam administration. SSI were within an acceptable range, indicating adequate antimicrobial prophylaxis, so intraoperative control of ASL does not seem necessary. In conclusion, contrary to our initial hypothesis, ASL is not influenced by volume turnover or blood loss during major surgery and therefore does not affect SSI.

Association of serum and fat tissue antibiotic concentrations with surgical site infections in lower gastrointestinal surgery

BackgroundDuring surgery, the effectiveness of perioperative prophylactic antibiotic administration against surgical site infections is inferred from serum concentrations and not from tissues where local infections occur. This study aimed to measure the serum and tissue concentrations of cefmetazole in colorectal surgery cases to clarify whether there is an association between the incidence of surgical site infections and antibiotic concentrations. MethodsThis prospective cohort study was performed at a single tertiary care center. The data of 105 patients who underwent colorectal surgery between October 2017 and September 2019 were evaluated. The primary outcome was the incidence of surgical site infections. Univariate analysis was performed to investigate the association between surgical site infections, perioperative factors, and the serum and tissue concentrations of cefmetazole. ResultsThe incidence of surgical site infections was 13/105 (12.4%). Cefmetazole concentrations were measured at initial incision (serum; 101 vs 93.1 mg/L, P = .75, subcutaneous fat tissue; 2.8 vs 3.7 mg/g, P = .15), intestinal resection (serum; 35.1 vs 36.7 mg/L, P = .63, mesenteric adipose tissue; 1.3 vs 1.7 mg/g, P = .55), and at skin closure (serum; 34.5 vs 44.8 mg/L, P = .18, subcutaneous fat tissue; 1.0 vs 2.2 mg/g, P = .09). In univariate analysis with P ≤ .10, cefmetazole concentration in subcutaneous fat tissue at skin closure was found to be a significant risk factor for surgical site infections. Age, additional intraoperative administration of cefmetazole, and creatinine clearance were also significant risk factors for the occurrence of surgical site infections. ConclusionLow subcutaneous fat cefmetazole concentrations at skin closure during gastrointestinal operations may also be involved in the occurrence of surgical site infections.

#8: Microbiome and immune disruption accompany mouse death in a gnotobiotic mouse model of neonatal sepsis

Abstract Background Premature infants frequently receive antibiotics, which diminishes gut microbial diversity and increases susceptibility to infections by antibiotic resistant pathogens. Neonates with decreased gut microbiota diversity, termed dysbiotic, have dysregulated immune systems marked by increased concentrations of circulating activated T cells and decreased concentrations of circulating neutrophils and dendritic cells. We hypothesize that antibiotics (1) enrich for pathogens within the gut, 2) promote a systemic, proinflammatory host response, and 3) cause death in an antibiotic- and microbiome-specific manner in a gnotobiotic model of preterm gut microbiota disruption. Methods We colonized germ free (GF) dams with stools from preterm infants. Mouse pups acquire this neonatal microbiota, and at 10 days of life (DOL), we treat them with clinically-relevant doses of antibiotics subcutaneously for 3 days. We determined serum concentrations of antibiotics in 10 DOL pups using tandem mass spectrometry to achieve approximate pharmacokinetics as observed in the neonatal intensive care unit (NICU). We ascertained phylogenetic composition using metagenomic shotgun sequencing of individual pup fecal samples longitudinally. We performed flow cytometry on peripheral blood and gut permeability assays to determine the local and peripheral immune response. Results We found adding probenecid prolonged the half-life of ampicillin and meropenem allowing for an approximation of serum levels observed in the NICU with an every 8 hour dosing regimen. Using two representative microbiomes from human neonates (hereafter referred to as microbiota A or B), we show that 95% of pups given microbiota A survive versus 54% given microbiota B after meropenem/probenecid treatment (Fig. 1A; p&amp;lt;0.01; n= 18–42 mice in 3–6 independent experiments). Conversely, only 28% of microbiota-A humanized pups survive during ampicillin/probenecid treatment (Fig. 1; p&amp;lt;0.0001). Ampicillin-resistant Klebsiella species and E. coli dominated the gut of microbiota A-humanized pups who succumbed during ampicillin/probenecid treatment whereas Enterococci dominated the gut of microbiota B-humanized pups who died during treatment. To test the reproducibility of this phenotype, we colonized mice with 2 additional preterm neonatal microbiomes with similar compositions to microbiota A and B (D and C, respectively). We found that microbiota-C humanized pups were similarly dominated by Enterococcus faecalis resulting in 42% mortality during meropenem/probenecid treatment (Fig. 1). Pups colonized with microbiota B had decreased circulating granulocytes, B cells, and CD8+ T cells at sacrifice after treatment compared to microbiota A-humanized pups. We next assessed gut permeability after antibiotic treatment by measuring 4kDa FITC-Dextran in mouse serum after oral gavage. Microbiota-A humanized pups treated with ampicillin/probenecid and microbiota B-humanized pups treated with meropenem/probenecid had elevated serum levels of FITC-Dextran (p&amp;lt;0.05 relative to vehicle control, one way ANOVA), indicative of increased gut permeability. Conclusions Our model of preterm microbiota perturbation by antibiotics demonstrates increased gut permeability, proinflammatory immune response, and death dependent on the microbiota-antibiotic combination. Our transgenerational humanized-microbiota mouse model can be utilized to determine antibiotic by microbiota perturbation and examine risks of late onset sepsis from specific antimicrobial administration. This research can lead to a personalized medicine approach of antibiotic treatment in the NICU to limit antibiotic side effects and mortality.

A Model-Based Pharmacokinetic/Pharmacodynamic Analysis of the Combination of Amoxicillin and Monophosphoryl Lipid A Against S. pneumoniae in Mice.

Combining amoxicillin with the immunostimulatory toll-like receptor 4 agonist monophosphoryl lipid A (MPLA) represents an innovative approach for enhancing antibacterial treatment success. Exploiting pharmacokinetic and pharmacodynamic data from an infection model of Streptococcus pneumoniae infected mice, we aimed to evaluate the preclinical exposure-response relationship of amoxicillin with MPLA coadministration and establish a link to survival. Antibiotic serum concentrations, bacterial numbers in lung and spleen and survival data of mice being untreated or treated with amoxicillin (four dose levels), MPLA, or their combination were analyzed by nonlinear mixed-effects modelling and time-to-event analysis using NONMEM® to characterize these treatment regimens. On top of a pharmacokinetic interaction, regarding the pharmacodynamic effects the combined treatment was superior to both monotherapies: The amoxicillin efficacy at highest dose was increased by a bacterial reduction of 1.74 log10 CFU/lung after 36 h and survival was increased 1.35-fold to 90.3% after 14 days both compared to amoxicillin alone. The developed pharmacometric pharmacokinetic/pharmacodynamic disease-treatment-survival models provided quantitative insights into a novel treatment option against pneumonia revealing a pharmacokinetic interaction and enhanced activity of amoxicillin and the immune system stimulator MPLA in combination. Further development of this drug combination flanked with pharmacometrics towards the clinical setting seems promising.

Antibiotic therapeutic drug monitoring in intensive care patients treated with different modalities of extracorporeal membrane oxygenation (ECMO) and renal replacement therapy: a prospective, observational single-center study

BackgroundEffective antimicrobial treatment is key to reduce mortality associated with bacterial sepsis in patients on intensive care units (ICUs). Dose adjustments are often necessary to account for pathophysiological changes or renal replacement therapy. Extracorporeal membrane oxygenation (ECMO) is increasingly being used for the treatment of respiratory and/or cardiac failure. However, it remains unclear whether dose adjustments are necessary to avoid subtherapeutic drug levels in septic patients on ECMO support. Here, we aimed to evaluate and comparatively assess serum concentrations of continuously applied antibiotics in intensive care patients being treated with and without ECMO.MethodsBetween October 2018 and December 2019, we prospectively enrolled patients on a pneumological ICU in southwest Germany who received antibiotic treatment with piperacillin/tazobactam, ceftazidime, meropenem, or linezolid. All antibiotics were applied using continuous infusion, and therapeutic drug monitoring of serum concentrations (expressed as mg/L) was carried out using high-performance liquid chromatography. Target concentrations were defined as fourfold above the minimal inhibitory concentration (MIC) of susceptible bacterial isolates, according to EUCAST breakpoints.ResultsThe final cohort comprised 105 ICU patients, of whom 30 were treated with ECMO. ECMO patients were significantly younger (mean age: 47.7 vs. 61.2 years; p < 0.001), required renal replacement therapy more frequently (53.3% vs. 32.0%; p = 0.048) and had an elevated ICU mortality (60.0% vs. 22.7%; p < 0.001). Data on antibiotic serum concentrations derived from 112 measurements among ECMO and 186 measurements from non-ECMO patients showed significantly lower median serum concentrations for piperacillin (32.3 vs. 52.9; p = 0.029) and standard-dose meropenem (15.0 vs. 17.8; p = 0.020) in the ECMO group. We found high rates of insufficient antibiotic serum concentrations below the pre-specified MIC target among ECMO patients (piperacillin: 48% vs. 13% in non-ECMO; linezolid: 35% vs. 15% in non-ECMO), whereas no such difference was observed for ceftazidime and meropenem.ConclusionsECMO treatment was associated with significantly reduced serum concentrations of specific antibiotics. Future studies are needed to assess the pharmacokinetic characteristics of antibiotics in ICU patients on ECMO support.

110. Clinical Outcomes of Patients with Secondary Bacteremia in the Omadacycline Phase 3 Acute Bacterial Skin and Skin Structure Infections and Community-Acquired Bacterial Pneumonia Studies

BackgroundLow serum concentrations of tetracycline antibiotics may raise concerns on their efficacy in patients with secondary bacteremia, especially in comorbid patients and in those with higher acuity of illness. Omadacycline (OMC), an aminomethylcycline antibiotic, showed noninferiority to linezolid (LZD) in two acute bacterial skin and skin structure infections (ABSSSI) studies (Omadacycline in Acute Skin and skin structure Infections Study [OASIS]-1 and -2), or to moxifloxacin (MOX) in a community-acquired bacterial pneumonia (CABP) study (Omadacycline for Pneumonia Treatment In the Community study [OPTIC]). This analysis considers clinical outcomes in patients with secondary bacteremia identified in these studies.MethodsBaseline blood cultures were taken from adult patients enrolled in Phase 3 randomized, double-blind clinical studies of OMC. Patients received ≥1 treatment dose: N = 1,347 ABSSSI (OMC n = 676; LZD n = 671); N = 774 CABP (OMC n = 386; MOX n = 388). Efficacy was evaluated by investigator assessment of clinical response at a post-treatment evaluation (PTE) 7–14 days (ABSSSI) or 5–10 days (CABP) after the last dose.ResultsBacteremia was confirmed in 63 patients (3%) across the three studies. Staphylococcus aureus was the most common pathogen in patients with ABSSSI (N = 30: OMC n/N = 7/13; LZD n/N = 9/17), with a median treatment duration of median 9 days (OMC) and median 10 days (LZD). Streptococcus pneumoniae was the most common pathogen in patients with CABP (N = 33; OMC n/N = 11/15; MOX n/N = 11/18), with a median treatment duration of 11 days (OMC) and 14 days (MOX). Clinical success was numerically comparable between treatment groups within each study (figure) after completion of therapy.ConclusionThe clinical successes of patients receiving OMC for ABSSSI or CABP with secondary bacteremia were comparable to results for LZD and MOX, respectively. Although limited by the small sample size, data from ABSSSI and CABP study patients with secondary bacteremia provide reassurance for the use of OMC. Real-world OMC data in patients with ABSSSI and CABP will be needed to assess outcomes in patients with additional comorbidities and/or higher acuity of illness. Disclosures All authors: No reported disclosures.

Cells released from S. epidermidis biofilms present increased antibiotic tolerance to multiple antibiotics.

Biofilm released cells (Brc) are thought to present an intermediary phenotype between biofilm and planktonic cells and this has the potential of affecting their antimicrobial tolerance.AimCompare the antimicrobial tolerance profiles of Brc, planktonic or biofilm cultures of S. epidermidis.MethodologyPlanktonic, biofilm cultures or Brc from 11 isolates were exposed to peak serum concentrations (PSC) of antibiotics. The antimicrobial killing effect in the three populations was determined by CFU.ResultsIncreased Brc tolerance to vancomycin, teicoplanin, rifampicin, erythromycin, and tetracycline was confirmed in model strain 9142. Furthermore, significant differences in the susceptibility of Brc to vancomycin were further found in 10 other clinical isolates.ConclusionsBrc from distinct clinical isolates presented a decreased susceptibility to most antibiotics tested and maintained that enhanced tolerance despite growing planktonically for up to 6 h. Our data suggest that Brc maintain the typical enhanced antibiotic tolerance of biofilm populations, further suggesting that addressing antimicrobial susceptibility in planktonic cultures might not reflect the full potential of biofilm-associated bacteria to survive therapy.

Individualization of treatment with gentamicin in neonates based on drug concentration in the blood serum.

AimTo evaluate how useful it is to make measurements of gentamicin concentrations in newborns' b/ood in order to optimize antibiotic therapy.Material and methods73 newborns empirically treated with gentamicin, in doses consistent with the Neofax® guidelines. There were 152 measurements of maximum and minimum serum gentamicin concentrations. Samples were determined based on the chemiluminescence technique on the Siemens Advia Centaur analyzer. The concentrations of gentamicin that were measured were compared with various therapeutic ranges used in the literature.ResultsAccording to the standards adopted in the University Hospital in Wrocław, the maximum concentration was reached in 38.16% of all the chi/dren, white the minimum in 26.32%. In other chi/dren the concentrations were below or above the therapeutic range. According to the Neofax® guidelines, the intended maximum concentration was observed in 71.05% of the newborns, and the minimum in 32.89%. The minimum concentration of <2 mg/L was found in 93.42% of the newborns, white >2 mg/L was determined in 33.33%, despite a 48-hour dosing interval. These were premature ba bies (<28th week of gestational age) and 55.56% of them reached a maximum concentration of 5-12 mg/L.There was no significant correlation between maximum or minimum concentration and gestational age or body weight.Conclusions1. The dosage of gentamicin in newborns according to the Neofax® recommendations does not ensure achieving the intended serum antibiotic concentrations. 2. In order to optimize gentamicin therapy in newborns it is necessary to individualize the dose based on measurements of drug concentrations in the blood and pharmacokinetic calculations.

Monitoring Treatment of Childhood Tuberculosis and the Role of Therapeutic Drug Monitoring.

Most children tolerate the first-line antibiotics used to treat Mycobacterium tuberculosis (TB) very well. The most common adverse effect is gastrointestinal distress unrelated to hepatotoxicity; the latter is seen in less than 1% of children. Despite the infrequency of hepatotoxicity, the potential long-term impact of hepatic insufficiency dictates that all children receiving antimycobacterial therapy should be evaluated periodically by symptom screening and physical examination. Routine measurement of transaminases in previously healthy, asymptomatic children is discouraged, as up to 40% of children will have transient, asymptomatic transaminase elevation that should not alter clinical management; measurement of serum liver enzymes is reserved for children who develop symptoms and those with existing liver disease or taking other potentially hepatotoxic drugs. Caregivers and personnel distributing directly-observed therapy need to be cognizant of potential drug toxicities and have a clear understanding of what to do if a child develops symptoms. There are substantial inter-patient variations in serum antibiotic concentrations when the same milligram per kilogram dose is given to different children of varying ages and sizes, reflecting differences in drug absorption and metabolism. While these variations may not impact the outcome of previously healthy children with mild disease, outcomes for children with human immunodeficiency virus infection or severe disease can be worse if sub-therapeutic drug concentrations are achieved. Therapeutic drug monitoring, wherein serum drug concentrations are used to optimize medication doses, should be considered for children with severe disease or if there is concern about alterations in drug absorption or metabolism.

2391. Liposomal Vancomycin and Cefazolin Combinations for S. aureus Biofilms

BackgroundBiofilms are sophisticated communities of matrix-encased and surface-attached bacteria that exhibit a distinct and specific resistant/tolerant phenotype to almost all antibacterial agents, with activity reduced 10- to 1,000-fold. Interestingly, this augmented resistance rapidly reverts when bacteria detach from the biofilm and return to a planktonic state. However, in this in vitro pharmacokinetic and pharmacodynamic (PK/PD) model we are able to expose biofilms to shear rates that are consistent with human interface and mimic antibiotic penetration and diffusion pathways from serum antibiotic concentration in humans.MethodsMethicillin-susceptible ATCC 29213 and MRSA 494 strains were evaluated. Initial susceptibility tests were performed by broth microdilution method. Time kill studies were performed to identify synergy patterns for liposomal and commercial antibiotics. Biofilm eradication was investigated using antibiotics vancomycin (VAN) (commercial) vs. liposomal VAN (VAN-L) (Patent#17-1460) and also combination of VAN- cefazolin (commercial) vs. liposomal vancomycin and liposomal cefazolin (CFZ-L) (Patent# 17-1460) in biofilms for strain MRSA 494. Biofilms were generated overnight using the BioFlux Microfluidic system (Fluxion BioSciences) at constant and continuous shear rates to optimize biofilm attachment and creation. Perfusion of antibiotic solutions (free peak concentration) was applied over a 24 h time period. Time lapse pictures were recorded to determine antibiotic biofilm eradication rates over 18h of incubation and pictures were analyzed using Bioflux Montage software.ResultsMIC values demonstrated a 2-fold reduction for liposomal vancomycin vs. commercial vancomycin. Also, combination of liposomal VAN MIC in presence of CFZ-L showed a 15.87-fold reduction in comparison to commercial VAN for 494. Overall, our biofilm results demonstrated a 43.6% improved eradication using VAN-L and CFZ-L combination in comparison to commercial VAN-CFZ combination. We also observed 5.7% improved eradication using VAN-L vs. commercial VAN.ConclusionLiposomal form of VAN and CFZ combinations are a promising approach to improved efficacy and reduced VAN resistance in S. aureus biofilms.Disclosures M. J. Rybak, Allergan: Consultant, Grant Investigator and Speaker’s Bureau, Research grant and Research support. Achaogen: Consultant, Grant Investigator and Speaker’s Bureau, Consulting fee, Research grant and Research support. Bayer: Consultant, Grant Investigator and Speaker’s Bureau, Consulting fee, Research grant and Research support. Melinta: Consultant, Grant Investigator and Speaker’s Bureau, Consulting fee, Research grant and Research support. Merck: Consultant, Grant Investigator and Speaker’s Bureau, Consulting fee, Research grant and Research support. Theravance: Consultant, Grant Investigator and Speaker’s Bureau, Consulting fee, Research grant and Research support. Sunovian: Consultant, Grant Investigator and Speaker’s Bureau, Consulting fee, Research grant and Research support. Zavante: Consultant, Grant Investigator and Speaker’s Bureau, Consulting fee, Research grant and Research support. NIAID: Consultant, Grant Investigator and Speaker’s Bureau, Consulting fee, Research grant and Research support.

Relationship of Pulmonary Outcomes, Microbiology, and Serum Antibiotic Concentrations in Cystic Fibrosis Patients

To determine the frequency of subtherapeutic exposure to intravenously administered β-lactam antibiotics in a cohort of cystic fibrosis (CF) patients who were treated for a pulmonary exacerbation, and its impact on pulmonary function. Nineteen CF patients between the ages of 5 and 21 years treated at Children's National Health System for a pulmonary exacerbation were followed between March 2015 and August 2016 in a prospective, longitudinal study. Pharmacokinetic modeling and minimum inhibitory concentrations (MICs) of the involved pathogens were used to determine therapeutic or subtherapeutic β-lactam antibiotic exposure based on the time the antibiotic concentration was above the MIC. Clinical outcomes were measured by spirometry values. The 19 participants were treated with a total of 29 courses of antibiotics. The most common β-lactam antibiotics used in a treatment course were ceftazidime (62%) and meropenem (45%). There was no difference in age, CF genotype, or creatinine clearance between the 9 participants (47%) who reached therapeutic concentrations versus the 10 (53%) who did not. Those who achieved sufficiently high antibiotic exposure had more significant improvement of their pulmonary function tests. We found that sufficient antibiotic exposure during treatment of CF pulmonary exacerbations was associated with improved pulmonary function. Moreover, it was impossible to predict, solely from the dosing regimen used, which patients were going to reach therapeutic β-lactam antibiotic serum concentrations. This suggests that CF patients may benefit from closer monitoring of their β-lactam exposure and bacterial MIC for optimal clinical outcomes.

Fluid flow in tumescent subcutaneous tissue observed with 3D scanning: massage accelerates injection dispersal

Objective: Tumescent injections are used for regional anesthesia, lipoplasty, and antibiotic delivery amonst others. We evaluate the potential of 3D scanning to monitor the extent and dispersal of tumescent injections and compare it to a method based on CT. We use the scanning technique to determine whether massage and/or transcutaneous ultrasound accelerates the dispersal of the tumescent fluid. Methods: 10–20 mL tumescent injections into live pig subcutaneous tissue were monitored with 3D scanning or CT and their response to waiting, massaging, or applying therapeutic ultrasound at 1 MHz and 3 W cm−2 was quantified. In a separate experiment, antibiotic was added to the tumescent fluid and serial blood samples were taken to monitor serum antibiotic concentrations. Massage or ultrasound was applied to generate a change in serum levels. Results: Massage significantly accelerates dispersal when compared to waiting (p < 0.05). Simultaneous application of ultrasound does not accelerate dispersal further. No change in serum antibiotic levels could be detected in response to massage or ultrasound. Conclusion: 3D scanning is an effective and inexpensive method of monitoring tumescent injections through the swollen skin profile. Although 3D scans do not capture the subcutaneous information revealed by CT, they do not require radiation or dedicated facilities.