Background: This study compared the mortality rates within 30 days of 2 different doses of sulbactam (6 g and 9–12 g daily) when used in colistin (COL)-based treatment regimens and COL monotherapy for carbapenem-resistant Acinetobacter baumannii (CRAB). Materials and Methods: This retrospective cohort study included 234 participants diagnosed with severe pneumonia due to CRAB infection at Phramongkutklao Hospital, Thailand, from July 1, 2011, to April 30, 2023. Participants were categorized into three groups: COL monotherapy, COL with 6 g of sulbactam daily (COL+S6g), and COL with 9–12 g of sulbactam daily (COL+SHD). Following the exclusion of patients with renal impairment (serum creatinine ≥1.5 mg/dl), a 1:2 propensity score (PS) matching was used to ensure comparable groups, with the COL group designated as the control. The matching variables included age, APACHE II scores, serum creatinine, intensive care units admission, and bacteremia. The number of participants in each group was as follows: 19 in COL, 32 in COL+S6g, and 38 in COL+SHD.The primary outcomes assessed were all-cause mortality rates at 7, 14, and 30 days. Kaplan–Meier survival curves and the Log-rank test were used to evaluate differences between groups, while multivariate Cox regression models were applied to determine the impact of treatment regimens. Results: The unmatching PS analysis indicated that the COL+SHD regimen significantly reduces mortality compared to the COL regimen; hazard ratios (HR) were 0.18 (95% confidence interval [CI], 0.06–0.55) for 7-day mortality and 0.53 (95% CI,-0.29–0.97) for 30-day mortality. In addition, the COL+SHD regimen also lowered mortality more than the COL+S6g regimen within 7 days (HR, 0.29; 95% CI, 0.11–0.75). After PS matching, the COL+SHD regimen significantly reduced 7-day mortality compared to the COL regimen (adjusted HR, 0.24; 95% CI, -0.07–0.82). However, COL+S6g did not differ in mortality from either COL+SHD or COL for 7-day mortality. At 14 days and 30 days, there were no significant regimens to reduce mortality. Conclusion Combining COL+SHD effectively reduced death in 7 days from severe pneumonia in CRAB infection treatment.

Background: This study compared the mortality rates within 30 days of 2 different doses of sulbactam (6 g and 9–12 g daily) when used in colistin (COL)-based treatment regimens and COL monotherapy for carbapenem-resistant Acinetobacter baumannii (CRAB). Materials and Methods: This retrospective cohort study included 234 participants diagnosed with severe pneumonia due to CRAB infection at Phramongkutklao Hospital, Thailand, from July 1, 2011, to April 30, 2023. Participants were categorized into three groups: COL monotherapy, COL with 6 g of sulbactam daily (COL+S6g), and COL with 9–12 g of sulbactam daily (COL+SHD). Following the exclusion of patients with renal impairment (serum creatinine ≥1.5 mg/dl), a 1:2 propensity score (PS) matching was used to ensure comparable groups, with the COL group designated as the control. The matching variables included age, APACHE II scores, serum creatinine, intensive care units admission, and bacteremia. The number of participants in each group was as follows: 19 in COL, 32 in COL+S6g, and 38 in COL+SHD.The primary outcomes assessed were all-cause mortality rates at 7, 14, and 30 days. Kaplan–Meier survival curves and the Log-rank test were used to evaluate differences between groups, while multivariate Cox regression models were applied to determine the impact of treatment regimens. Results: The unmatching PS analysis indicated that the COL+SHD regimen significantly reduces mortality compared to the COL regimen; hazard ratios (HR) were 0.18 (95% confidence interval [CI], 0.06–0.55) for 7-day mortality and 0.53 (95% CI,-0.29–0.97) for 30-day mortality. In addition, the COL+SHD regimen also lowered mortality more than the COL+S6g regimen within 7 days (HR, 0.29; 95% CI, 0.11–0.75). After PS matching, the COL+SHD regimen significantly reduced 7-day mortality compared to the COL regimen (adjusted HR, 0.24; 95% CI, -0.07–0.82). However, COL+S6g did not differ in mortality from either COL+SHD or COL for 7-day mortality. At 14 days and 30 days, there were no significant regimens to reduce mortality. Conclusion Combining COL+SHD effectively reduced death in 7 days from severe pneumonia in CRAB infection treatment.

Background: This study compared the mortality rates within 30 days of 2 different doses of sulbactam (6 g and 9–12 g daily) when used in colistin (COL)-based treatment regimens and COL monotherapy for carbapenem-resistant Acinetobacter baumannii (CRAB). Materials and Methods: This retrospective cohort study included 234 participants diagnosed with severe pneumonia due to CRAB infection at Phramongkutklao Hospital, Thailand, from July 1, 2011, to April 30, 2023. Participants were categorized into three groups: COL monotherapy, COL with 6 g of sulbactam daily (COL+S6g), and COL with 9–12 g of sulbactam daily (COL+SHD). Following the exclusion of patients with renal impairment (serum creatinine ≥1.5 mg/dl), a 1:2 propensity score (PS) matching was used to ensure comparable groups, with the COL group designated as the control. The matching variables included age, APACHE II scores, serum creatinine, intensive care units admission, and bacteremia. The number of participants in each group was as follows: 19 in COL, 32 in COL+S6g, and 38 in COL+SHD.The primary outcomes assessed were all-cause mortality rates at 7, 14, and 30 days. Kaplan–Meier survival curves and the Log-rank test were used to evaluate differences between groups, while multivariate Cox regression models were applied to determine the impact of treatment regimens. Results: The unmatching PS analysis indicated that the COL+SHD regimen significantly reduces mortality compared to the COL regimen; hazard ratios (HR) were 0.18 (95% confidence interval [CI], 0.06–0.55) for 7-day mortality and 0.53 (95% CI,-0.29–0.97) for 30-day mortality. In addition, the COL+SHD regimen also lowered mortality more than the COL+S6g regimen within 7 days (HR, 0.29; 95% CI, 0.11–0.75). After PS matching, the COL+SHD regimen significantly reduced 7-day mortality compared to the COL regimen (adjusted HR, 0.24; 95% CI, -0.07–0.82). However, COL+S6g did not differ in mortality from either COL+SHD or COL for 7-day mortality. At 14 days and 30 days, there were no significant regimens to reduce mortality. Conclusion Combining COL+SHD effectively reduced death in 7 days from severe pneumonia in CRAB infection treatment.

Background: Linezolid, an oxazolidinone antibiotic, is recommended for vancomycinresistant enterococci (VRE). However, 100% free-drug concentration above the minimum inhibitory concentration (fT>MIC) and an area under the curve of free drug to MIC ratio (fAUC24/MIC) >100 were associated with favorable clinical outcome with less emerging resistance. A plasma trough concentration (Ctrough ) of linezolid ≥9 µg/mL was also related to hematologic toxicity. Thus, linezolid dose optimization is needed for VRE treatment. The study aimed to determine the in vitro linezolid activity against clinical VRE isolates and linezolid dosing regimens in critically ill patients who met the target pharmacokinetics/ pharmacodynamics (PK/PD) for VRE treatment. Materials and Methods: Enterococcal isolates from enterococcal-infected patients were obtained between 2014 and 2018 at Phramongkutklao Hospital. We used Monte Carlo simulation to calculate the probability of target attainment, and the cumulative fraction of response (CFR) of the free area under the curve to MIC ratio (fAUIC 24 ) was used to calculate the fAUC24/MIC 80 - 100 and fT/MIC >85 - 100% of the interval time of administration for clinical response and microbiological eradication as well as the Ctrough ≥9 µg/mL for the probability of hematologic toxicity. Results: For linezolid MIC determination, the MIC median (MIC50 ), MIC for 90% growth (MIC90 ), and range for linezolid were 1.5 µg/mL, 2 µg/mL, and 0.72 - 2 µg/mL, respectively.A dosing regimen of 1,200 mg either once daily or as a divided dose every 12 h gave target attainments of fAUC24/MICs >80 and >100, which exceeded 90% for MICs ≤1 and ≤1 µg/mL, respectively, with a rate of hematologic toxicity <15%. If the expected fT>MICs were >85% and 100%, a 1,200-mg divided dose every 12 h could cover VRE isolates having linezolid MICs ≤1 µg/mL and ≤0.75 µg/mL. Even 600 mg every 8 h and 1,200 mg as a continuous infusion gave a higher target attainment of fAUC24/MIC and a fT>MIC and the target CFR, but those regimens gave Ctrough ≥9 µg/mL rates of 40.7% and 99.6%. Conclusion The current dosing of 1,200 mg/day might be optimal treatment for infection by VRE isolates with documented MICs ≤1 µg/mL. For treatment of VRE with a MIC of 2 µg/mL or to achieve the target CFR, the use of linezolid with other antibiotic combinations might help achieve the PK/PD target, provide better clinical outcome, and prevent resistance.

Background: Linezolid, an oxazolidinone antibiotic, is recommended for vancomycinresistant enterococci (VRE). However, 100% free-drug concentration above the minimum inhibitory concentration (fT>MIC) and an area under the curve of free drug to MIC ratio (fAUC24/MIC) >100 were associated with favorable clinical outcome with less emerging resistance. A plasma trough concentration (Ctrough ) of linezolid ≥9 µg/mL was also related to hematologic toxicity. Thus, linezolid dose optimization is needed for VRE treatment. The study aimed to determine the in vitro linezolid activity against clinical VRE isolates and linezolid dosing regimens in critically ill patients who met the target pharmacokinetics/ pharmacodynamics (PK/PD) for VRE treatment. Materials and Methods: Enterococcal isolates from enterococcal-infected patients were obtained between 2014 and 2018 at Phramongkutklao Hospital. We used Monte Carlo simulation to calculate the probability of target attainment, and the cumulative fraction of response (CFR) of the free area under the curve to MIC ratio (fAUIC 24 ) was used to calculate the fAUC24/MIC 80 - 100 and fT/MIC >85 - 100% of the interval time of administration for clinical response and microbiological eradication as well as the Ctrough ≥9 µg/mL for the probability of hematologic toxicity. Results: For linezolid MIC determination, the MIC median (MIC50 ), MIC for 90% growth (MIC90 ), and range for linezolid were 1.5 µg/mL, 2 µg/mL, and 0.72 - 2 µg/mL, respectively.A dosing regimen of 1,200 mg either once daily or as a divided dose every 12 h gave target attainments of fAUC24/MICs >80 and >100, which exceeded 90% for MICs ≤1 and ≤1 µg/mL, respectively, with a rate of hematologic toxicity <15%. If the expected fT>MICs were >85% and 100%, a 1,200-mg divided dose every 12 h could cover VRE isolates having linezolid MICs ≤1 µg/mL and ≤0.75 µg/mL. Even 600 mg every 8 h and 1,200 mg as a continuous infusion gave a higher target attainment of fAUC24/MIC and a fT>MIC and the target CFR, but those regimens gave Ctrough ≥9 µg/mL rates of 40.7% and 99.6%. Conclusion The current dosing of 1,200 mg/day might be optimal treatment for infection by VRE isolates with documented MICs ≤1 µg/mL. For treatment of VRE with a MIC of 2 µg/mL or to achieve the target CFR, the use of linezolid with other antibiotic combinations might help achieve the PK/PD target, provide better clinical outcome, and prevent resistance.

Tigecycline was previously considered to have activity against vancomycin-resistant Enterococcus (VRE) isolates, but the optimal dose was not clarified. Thus, this study assessed the in vitro activity of tigecycline against clinical VRE isolates to determine its optimal regimens for complicated intra-abdominal (cIAIs) and complicated skin/soft tissue infections (cSSTIs). We used Monte Carlo simulation to calculate the probability of target attainment (PTA) and the cumulative fraction of response for the ratio of the free area under the curve to the minimum inhibitory concentration (MIC) (fAUIC 24 ), which were 17.9 and 6.9 for treating cSSTIs and cIAIs, respectively. All clinical isolates were Enterococcus faecium. Only a maintenance dose of 200 mg/day tigecycline gave the target attainment of fAUIC 24>17.9, and PTA exceeded 90% for MIC ≤0.38 µg/mL. Meanwhile, this dose gave the target attainment of fAUIC 24>6.9, and PTA exceeded 90% for MIC ≤1 µg/mL. All simulated tigecycline dosing regimens met the fAUIC 24 targets more than 90% of the cumulative fraction of response.Despite its apparent efficacy, a daily tigecycline dose of 200 mg is recommended for VRE isolates with MICs of ≤0.38 µg/mL and ≤1 µg/mL for treating cSSTIs and cIAIs, respectively.

Background: Currently, the achievement of the target area under the curve (AUC)/ minimum inhibitory concentration ratio during the first 24 - 48 h of treatment is associated with reduced 30-day mortality and greater microbiological eradication in patients with methicillin-resistant Staphylococcus aureus bacteremia. This study aimed to determine the AUC and pharmacokinetic parameters on the first day of vancomycin administration based on the Bayesian theorem to optimize the dosing regimen in critically ill patients. Materials and Methods: This retrospective study included participants meeting the following criteria: 1) ≥18 years old; 2) receipt of at least one dose of vancomycin; 3) measurement of 2 vancomycin serum concentrations during the first 24 h of treatment; and 4) an intensive care unit admission, mechanical ventilator use, or an Acute Physiology and Chronic Health Evaluation II score >15 points. The AUC on day 1 of treatment and the estimated vancomycin pharmacokinetic parameters were measured using PrecisePK software based on the Bayesian theorem. Results: We obtained 132 vancomycin concentrations from 66 patients. The vancomycin pharmacokinetic parameters were as follows: AUC0-24 , 571.09 (± standard deviation [SD] 188.62) mg/L·h; clearance (CL), 2.97 (± SD 1.81) L/h; volume of distribution (Vd), 50.60 (± SD 13.91) L;elimination rate constant, 0.062 (± SD 0.039) h −1 ; and half-life, 18.19 (± SD 15.96) h. Focusing on the vancomycin loading dose, AUC 0-24 400 - 600 was achieved in 41.7, 46.1, 44.4, and 26.3% of patients with loading doses of <20, 20 – 24.9, 25 – 30, and >30 mg/kg, respectively. Whereas AUC0-24 ≥521 was achieved in 50, 50, 77.8, and 84.2% of patients with loading doses of <20, 20 – 24.9, 25 – 30, and >30 mg/kg, respectively. The CL of vancomycin was correlated with creatinine CL, whereas the Vd of vancomycin was significantly correlated with age and body weight. Conclusion This study revealed that the higher Vd and CL values on the first day of vancomycin therapy were found in critically ill patients. Additionally, a higher vancomycin loading dose (25 – 30 mg/kg) might be required to achieve target of AUC0-24 during early phase of administration for critically ill patients.

Background: Acinetobacter baumannii has been recognized as a cause of nosocomial infection. To date, polymyxins, the last-resort therapeutic agents for carbapenem-resistant A. baumannii (CRAB). Thus, the small number of effective antibiotic options against CRAB represents a challenge to human health. This study examined the appropriate dosage regimens of colistin alone or in combination with sulbactam or fosfomycin using Monte Carlo simulation with the aims of improving efficacy and reducing the risk of nephrotoxicity. Materials and Methods: Clinical CRAB isolates were obtained from patients admitted to Phramongkutklao Hospital in 2014 and 2015. The minimum inhibitory concentration (MIC) of colistin for each CRAB isolate was determined using the broth dilution method, whereas those of sulbactam and fosfomycin were determined using the agar dilution method. Each drug regimen was simulated using the Monte Carlo technique to calculate the probability of target attainment (PTA) and the cumulative fraction of response (CFR). Nephrotoxicity based on RIFLE (Risk, Injury, Failure, Loss of kidney function, and End-stage kidney disease) criteria was indicated by colistin trough concentration exceeding ≥3.3 µg/mL. Results: A total of 50 CRAB isolates were included. The MIC 50 and MIC 90 were 64 and 128 µg/mL, respectively, for sulbactam, 256 and 2,048 µg/mL, respectively, for fosfomycin, and 1 and 4 µg/mL, respectively, for colistin. In patients with creatinine clearance of 91 – 130 m/min, the dosing regimens of 180 mg every 12 h and 150 mg every 8 h achieved ≥ 90% of target of the area under the free drug plasma concentration–time curve from 0 to 24 hr (fAUC24)/MIC ≥25 against isolates MICs of ≤0.25 and ≤0.5 µg/mL, respectively, and their rates of colistin trough concentration more than ≥3.3 µg/mL were 35 and 54%, respectively. Colistin combined with sulbactam or fosfomycin decreased the colistin MIC of CRAB isolates from 1 – 16 µg/mL to 0.0625 – 1 and 0.0625 – 2 µg/mL, respectively. Based on CFR ≥ 90%, no colistin monotherapy regimens in patients with creatinine clearance of 91 – 130 mL/min were effective against all of the studied CRAB isolates. For improving efficacy and reducing the risk of nephrotoxicity, colistin 150 mg given every 12 h together with sulbactam (≥6 g/day) or fosfomycin (≥18 g/day) was effective in patients with creatinine clearance of 91 – 130 mL/min. Additionally, both colistin combination regimens were effective against five colistin-resistant A. baumannii isolates. Conclusion Colistin monotherapy at the maximum recommended dose might not cover some CRAB isolates. Colistin combination therapy appears appropriate for achieving the pharmacokinetic/pharmacodynamic targets of CRAB treatment.

Background: Currently, the achievement of the target area under the curve (AUC)/ minimum inhibitory concentration ratio during the first 24 - 48 h of treatment is associated with reduced 30-day mortality and greater microbiological eradication in patients with methicillin-resistant Staphylococcus aureus bacteremia. This study aimed to determine the AUC and pharmacokinetic parameters on the first day of vancomycin administration based on the Bayesian theorem to optimize the dosing regimen in critically ill patients. Materials and Methods: This retrospective study included participants meeting the following criteria: 1) ≥18 years old; 2) receipt of at least one dose of vancomycin; 3) measurement of 2 vancomycin serum concentrations during the first 24 h of treatment; and 4) an intensive care unit admission, mechanical ventilator use, or an Acute Physiology and Chronic Health Evaluation II score >15 points. The AUC on day 1 of treatment and the estimated vancomycin pharmacokinetic parameters were measured using PrecisePK software based on the Bayesian theorem. Results: We obtained 132 vancomycin concentrations from 66 patients. The vancomycin pharmacokinetic parameters were as follows: AUC0-24 , 571.09 (± standard deviation [SD] 188.62) mg/L·h; clearance (CL), 2.97 (± SD 1.81) L/h; volume of distribution (Vd), 50.60 (± SD 13.91) L;elimination rate constant, 0.062 (± SD 0.039) h −1 ; and half-life, 18.19 (± SD 15.96) h. Focusing on the vancomycin loading dose, AUC 0-24 400 - 600 was achieved in 41.7, 46.1, 44.4, and 26.3% of patients with loading doses of <20, 20 – 24.9, 25 – 30, and >30 mg/kg, respectively. Whereas AUC0-24 ≥521 was achieved in 50, 50, 77.8, and 84.2% of patients with loading doses of <20, 20 – 24.9, 25 – 30, and >30 mg/kg, respectively. The CL of vancomycin was correlated with creatinine CL, whereas the Vd of vancomycin was significantly correlated with age and body weight. Conclusion This study revealed that the higher Vd and CL values on the first day of vancomycin therapy were found in critically ill patients. Additionally, a higher vancomycin loading dose (25 – 30 mg/kg) might be required to achieve target of AUC0-24 during early phase of administration for critically ill patients.

Background: Acinetobacter baumannii has been recognized as a cause of nosocomial infection. To date, polymyxins, the last-resort therapeutic agents for carbapenem-resistant A. baumannii (CRAB). Thus, the small number of effective antibiotic options against CRAB represents a challenge to human health. This study examined the appropriate dosage regimens of colistin alone or in combination with sulbactam or fosfomycin using Monte Carlo simulation with the aims of improving efficacy and reducing the risk of nephrotoxicity. Materials and Methods: Clinical CRAB isolates were obtained from patients admitted to Phramongkutklao Hospital in 2014 and 2015. The minimum inhibitory concentration (MIC) of colistin for each CRAB isolate was determined using the broth dilution method, whereas those of sulbactam and fosfomycin were determined using the agar dilution method. Each drug regimen was simulated using the Monte Carlo technique to calculate the probability of target attainment (PTA) and the cumulative fraction of response (CFR). Nephrotoxicity based on RIFLE (Risk, Injury, Failure, Loss of kidney function, and End-stage kidney disease) criteria was indicated by colistin trough concentration exceeding ≥3.3 µg/mL. Results: A total of 50 CRAB isolates were included. The MIC 50 and MIC 90 were 64 and 128 µg/mL, respectively, for sulbactam, 256 and 2,048 µg/mL, respectively, for fosfomycin, and 1 and 4 µg/mL, respectively, for colistin. In patients with creatinine clearance of 91 – 130 m/min, the dosing regimens of 180 mg every 12 h and 150 mg every 8 h achieved ≥ 90% of target of the area under the free drug plasma concentration–time curve from 0 to 24 hr (fAUC24)/MIC ≥25 against isolates MICs of ≤0.25 and ≤0.5 µg/mL, respectively, and their rates of colistin trough concentration more than ≥3.3 µg/mL were 35 and 54%, respectively. Colistin combined with sulbactam or fosfomycin decreased the colistin MIC of CRAB isolates from 1 – 16 µg/mL to 0.0625 – 1 and 0.0625 – 2 µg/mL, respectively. Based on CFR ≥ 90%, no colistin monotherapy regimens in patients with creatinine clearance of 91 – 130 mL/min were effective against all of the studied CRAB isolates. For improving efficacy and reducing the risk of nephrotoxicity, colistin 150 mg given every 12 h together with sulbactam (≥6 g/day) or fosfomycin (≥18 g/day) was effective in patients with creatinine clearance of 91 – 130 mL/min. Additionally, both colistin combination regimens were effective against five colistin-resistant A. baumannii isolates. Conclusion Colistin monotherapy at the maximum recommended dose might not cover some CRAB isolates. Colistin combination therapy appears appropriate for achieving the pharmacokinetic/pharmacodynamic targets of CRAB treatment.