Imipenem, meropenem, or doripenem to treat patients with Pseudomonas aeruginosa ventilator-associated pneumonia

Performance and impact of rapid multiplex PCR on diagnosis and treatment of ventilated hospital-acquired pneumonia in patients with extended-spectrum β-lactamase-producing Enterobacterales rectal carriage

BACKGROUND

Antimicrobial stewardship (AMS) for ventilator-associated pneumonia (VAP) or ventilated hospital-acquired pneumonia (vHAP) in extended-spectrum β-lactamase-producing Enterobacterales (ESBL-E) carriers is challenging. BioFire® FilmArray® Pneumonia plus Panel (mPCR) can detect bacteria and antibiotic resistance genes, including blaCTX-M, the most common ESBL-encoding gene.

METHODS

This monocentric, prospective study was conducted on a group of ESBL-E carriers from March 2020 to August 2022. The primary objective was to evaluate the concordance between the results of mPCR and conventional culture performed on respiratory samples of ESBL-E carriers to investigate suspected VAP/vHAP. The secondary objective was to appraise the impact of performing or not mPCR on initial antibiotic therapy adequacy in ESBL-E carriers with confirmed VAP/vHAP.

RESULTS

Over the study period, 294 patients with ESBL-E carriage were admitted to the ICU, of who 168 (57%) were mechanically ventilated. (i) Diagnostic performance of mPCR was evaluated in suspected 41 episodes of VAP/vHAP: blaCTX-M gene was detected in 15/41 (37%) episodes, where 9/15 (60%) were confirmed ESBL-E-induced pneumonia. The culture and blaCTX-M were concordant in 35/41 (85%) episodes, and in all episodes where blaCTX-M was negative (n = 26), the culture never detected ESBL-E. (ii) The impact of mPCR on initial antibiotic therapy adequacy was assessed in 95 episodes of confirmed VAP/vHAP (22 episodes were tested with mPCR and 73 without); 47 (49%) episodes were ESBL-E-induced, and 24 (25%) were carbapenem-resistant bacteria-induced. The use of mPCR was significantly associated with higher prescription of adequate empirical antibiotic therapy in the multivariable logistic regression (adjusted odds ratio (aOR) (95% CI) of 7.5 (2.1-35.9), p = 0.004), propensity-weighting (aOR of 5.9 (1.6-22.1), p = 0.008), and matching-cohort models (aOR of 5.8 (1.5-22.1), p = 0.01).

CONCLUSION

mPCR blaCTX-M showed an excellent diagnostic value to rule out the diagnosis of ESBL-E related pneumonia in ESBL-E carriers with suspected VAP/vHAP. In addition, in patients with confirmed VAP/vHAP, a mPCR-based antibiotic therapy was associated with an increased prescription of adequate empirical antibiotic therapy. Performing mPCR on respiratory samples seems to be a promising tool in ESBL-E carriers with suspected vHAP/VAP. However, if mPCR is used in very low pre-test clinical probability of pneumonia, due to the high sensitivity and the rate of overdiagnosed pneumonia, the risk of overconsumption of carbapenem may prevail. Further studies are warranted.

Antibiotic management programme in a tertiary intensive care unit: effects of a carbapenem-restricted period on clinical and laboratory parameters and costs of infections

BACKGROUND

Carbapenems are antibiotics used for serious infections. The consumption of carbapenems has increased worldwide due to increasing microbial resistance.

AIM

To investigate the effects of a carbapenem-restricted antimicrobial stewardship programme (ASP) on changes in the resistance profiles of infectious agents, the amount of antibiotics used, length of stay in the intensive care unit (ICU), mortality, and costs.

METHODS

Patients hospitalized in ICU between July 1st, 2020 and May 1st, 2021 were divided into two periods: the carbapenem-non-restricted period (CNRP); and the carbapenem-restricted period (CRP) in which alternative antibiotics to carbapenems were preferred during infection. The defined daily dose (DDD) per 100 patient-day methodology was used to calculate the antibiotic consumption.

FINDINGS

Of the 572 patients included in the study, 62.2% were male, and mean age was 70.5 years. In the blood culture the most frequently Gram-negative agent was Acinetobacter baumannii (25%). A. baumannii bloodstream infections with multidrug-resistant and extensively drug resistant micro-organisms were significantly different between the two periods (CNRP: 95.6% (N = 22), CRP: 66.6% (N = 8); P = 0.04). There was a gradual decrease in the incidence density and rate of nosocomial infection (P = 0.06), and a significant decrease in meropenem consumption between the two periods (CNRP vs CRP: 21.19 vs 6.37 DDD per 100 patient-days respectively; P = 0.007). ASP yielded US$8,600 of antibiotic cost savings and a total of 14% patient cost savings (P < 0.05) per patient.

CONCLUSION

Combining an effective ASP with a comprehensive infection control programme may mitigate the emergence of antimicrobial-resistant bacteria.

Prevalence of meropenem-resistant Pseudomonas Aeruginosa in Ethiopia: a systematic review and meta‑analysis

INTRODUCTION

Antimicrobial resistance (AMR) is a pressing global health concern, particularly pronounced in low-resource settings. In Ethiopia, the escalating prevalence of carbapenem-resistant Pseudomonas aeruginosa (P. aeruginosa) poses a substantial threat to public health.

METHODS

A comprehensive search of databases, including PubMed, Scopus, Embase, Hinari, and Google Scholar, identified relevant studies. Inclusion criteria encompassed observational studies reporting the prevalence of meropenem-resistant P. aeruginosa in Ethiopia. Quality assessment utilized JBI checklists. A random-effects meta-analysis pooled data on study characteristics and prevalence estimates, with subsequent subgroup and sensitivity analyses. Publication bias was assessed graphically and statistically.

RESULTS

Out of 433 studies, nineteen, comprising a total sample of 11,131, met inclusion criteria. The pooled prevalence of meropenem-resistant P. aeruginosa was 15% (95% CI: 10-21%). Significant heterogeneity (I2 = 83.6%) was observed, with the number of P. aeruginosa isolates identified as the primary source of heterogeneity (p = 0.127). Subgroup analysis by infection source revealed a higher prevalence in hospital-acquired infections (28%, 95% CI: 10, 46) compared to community settings (6%, 95% CI: 2, 11). Geographic based subgroup analysis indicated the highest prevalence in the Amhara region (23%, 95% CI: 8, 38), followed by Addis Ababa (21%, 95% CI: 11, 32), and lower prevalence in the Oromia region (7%, 95% CI: 4, 19). Wound samples exhibited the highest resistance (25%, 95% CI: 25, 78), while sputum samples showed the lowest prevalence. Publication bias, identified through funnel plot examination and Egger's regression test (p < 0.001), execution of trim and fill analysis resulted in an adjusted pooled prevalence of (3.7%, 95% CI: 2.3, 9.6).

CONCLUSION

The noteworthy prevalence of meropenem resistance among P. aeruginosa isolates in Ethiopia, particularly in healthcare settings, underscores the urgency of implementing strict infection control practices and antibiotic stewardship. Further research is imperative to address and mitigate the challenges posed by antimicrobial resistance in the country.

Risk predict model using multi-drug resistant organism infection from Neuro-ICU patients: a retrospective cohort study

The aim of this study was to analyze the current situation and risk factors of multi-drug-resistant organism (MDRO) infection in Neuro-intensive care unit (ICU) patients, and to develop the risk predict model. The data was collected from the patients discharged from Neuro-ICU of grade-A tertiary hospital at Guizhou province from January 2018 to April 2020. Binary Logistics regression was used to analyze the data. The model was examined by receiver operating characteristic curve (ROC). The grouped data was used to verify the sensitivity and specificity of the model. A total of 297 patients were included, 131 patients infected with MDRO. The infection rate was 44.11%. The results of binary Logistics regression showed that tracheal intubation, artery blood pressure monitoring, fever, antibiotics, pneumonia were independent risk factors for MDRO infection in Neuro-ICU (P < 0.05), AUC = 0.887. The sensitivity and specificity of ROC curve was 86.3% and 76.9%. The risk prediction model had a good predictive effect on the risk of MDRO infection in Neuro ICU, which can evaluate the risk and provide reference for preventive treatment and nursing intervention.

Computational exploration of molecular flexibility and interaction of meropenem analogs with the active site of oxacillinase-23 in Acinetobacter baumannii

Background: Carbapenem-resistant Acinetobacter baumannii is an opportunistic pathogen responsible for nosocomial infections and is one of the biggest global threats according to the World Health Organization (WHO), particularly causing substantial morbidity and mortality. Objectives: This study aimed at using computational approaches to screen meropenem and its analogs against OXA-23-positive Acinetobacter baumannii, analyzing the correlations between kinetic and phenotypic characteristics. Methods: A total of 5,450 compounds were screened using virtual screening workflow (HTVS, Glide-SP, and Glide-XP) to identify the best compounds based on their binding energy and interactions against OXA-23 and OXA-27 as they had phenotypic data available. Molecular dynamics simulation and density functional theory (DFT) studies were performed from the outcome of molecular docking analysis. Results: During simulations, meropenem and its analogs exhibited high-level stable interactions with Ser79, Ser126, Thr217, Trp219, and Arg259 of OXA-23. Meropenem displayed a CovDock energy of about -3.5 and -1.9 kcal mol^-1 against OXA-23 and OXA-27, respectively. Among the 5,450 compounds, Pubchem_10645796, Pubchem_25224737, and ChEMBL_14 recorded CovDock energy between -6.0 and -9.0 kcal mol^-1. Moreover, the infra-red (IR) spectrophotometric analysis revealed C=O and C-N atoms showing bands at 1,800 and 1,125 cm^-1, respectively. These observed data are in congruence with the experimental observations. Conclusion: The identified compounds showed good agreement with the spectrophotometric analysis using DFT methods. In the earlier studies, meropenem's MIC value was 32 μg mL^-1 in OXA-23-positive isolate A2265 compared to the MIC of 1 μg mL^-1 in Δbla _OXA-23 A2265. Comparing the CovDock energy and hydrogen-bonding interactions, the predicted results are in good agreement with the experimental data reported earlier. Our results highlight the importance of OXA-23 molecular docking studies and their compliance with the phenotypic results. It will help further in developing newer antibiotics for treating severe infections associated with carbapenem-resistant A. baumannii.

Doripenem in the Treatment of Patients with Nosocomial Pneumonia: A Meta-Analysis

Introduction: Clinically, doripenem therapy for nosocomial pneumonia remains a serious concern. The purpose of this meta-analysis was to explore the efficacy and the safety of doripenem therapy for nosocomial pneumonia in comparison with other antimicrobial agents. Methods: Studies were eligible for inclusion only if they directly compared the clinical effectiveness of doripenem and other antimicrobial agent therapies for nosocomial pneumonia in adult patients between 1 January 2000 and 30 April 2022. All studies were included if they reported one or more of the following outcomes: clinical cure rate, microbiological cure rate, all-cause mortality, and adverse events. Results: Six randomized controlled trials and three retrospective studies were included in the meta-analysis. There were 952 patients in the doripenem group and 1183 patients in the comparator group. The comparator antimicrobial agents included imipenem/cilastatin, meropenem, and piperacillin/tazobactam. Seven studies had a high risk of bias. Doripenem therapy for nosocomial pneumonia had a microbiological cure rate, a clinical cure rate, an all-cause mortality, and adverse events similar to those of comparators. Conclusions: The efficacy and the safety of doripenem therapy for nosocomial pneumonia were comparable with those of comparators. Randomized controlled trials are needed to confirm the role of doripenem in nosocomial pneumonia therapy.

Seeking patterns of antibiotic resistance in ATLAS, an open, raw MIC database with patient metadata

Antibiotic resistance represents a growing medical concern where raw, clinical datasets are under-exploited as a means to track the scale of the problem. We therefore sought patterns of antibiotic resistance in the Antimicrobial Testing Leadership and Surveillance (ATLAS) database. ATLAS holds 6.5M minimal inhibitory concentrations (MICs) for 3,919 pathogen-antibiotic pairs isolated from 633k patients in 70 countries between 2004 and 2017. We show most pairs form coherent, although not stationary, timeseries whose frequencies of resistance are higher than other databases, although we identified no systematic bias towards including more resistant strains in ATLAS. We sought data anomalies whereby MICs could shift for methodological and not clinical or microbiological reasons and found artefacts in over 100 pathogen-antibiotic pairs. Using an information-optimal clustering methodology to classify pathogens into low and high antibiotic susceptibilities, we used ATLAS to predict changes in resistance. Dynamics of the latter exhibit complex patterns with MIC increases, and some decreases, whereby subpopulations' MICs can diverge. We also identify pathogens at risk of developing clinical resistance in the near future.

Routine wastewater-based monitoring of antibiotic resistance in two Finnish hospitals: focus on carbapenem resistance genes and genes associated with bacteria causing hospital-acquired infections

BACKGROUND

Wastewater-based monitoring represents a useful tool for antibiotic resistance surveillance.

AIM

To investigate the prevalence and abundance of antibiotic resistance genes (ARGs) in hospital wastewater over time.

METHODS

Wastewater from two hospitals in Finland (HUS1 and HUS2) was monitored weekly for nine weeks (weeks 25-33) in summer 2020. A high-throughput real-time polymerization chain reaction (HT-qPCR) system was used to detect and quantify 216 ARGs and genes associated with mobile genetic elements (MGEs), integrons, and bacteria causing hospital-acquired infections (HAIs), as well as the 16S rRNA gene. Data from HT-qPCR were analysed and visualized using a novel digital platform, ResistApp. Eight carbapenem resistance genes (blaGES, blaKPC, blaVIM, blaNDM, blaCMY, blaMOX, blaOXA48, and blaOXA51) and three genes associated with bacteria causing HAIs (Acinetobacter baumannii, Klebsiella pneumoniae, and Pseudomonas aeruginosa) were studied.

FINDINGS

There was a significantly higher number of ARGs at both hospitals in weeks 27-30 (174-191 genes) compared to other sampling weeks (151-171 genes). Our analyses also indicated that the two hospitals, which used different amounts of antibiotics, had significantly different resistance gene profiles. Carbapenem resistance genes were more prevalent and abundant in HUS1 than HUS2. Across both hospitals, blaGES and blaVIM were the most prevalent and abundant. There was also a strong positive association between blaKPC and K. pneumoniae in HUS1 wastewater.

CONCLUSION

Routine wastewater-based monitoring using ResistApp can provide valuable information on the prevalence and abundance of ARGs in hospitals. This helps hospitals understand the spread of antibiotic resistance in hospitals and identify potential areas for intervention.

Clinical Effectiveness of a High Dose Versus the Standard Dose of Meropenem in Ventilator-associated Pneumonia Caused by Multidrugresistant Bacteria: A Randomized, Single-blind Clinical Trial

BACKGROUND

Meropenem standard doses are based on the minimum inhibitory concentration of sensitive pathogens and the pharmacokinetic parameter of not critically ill patients. We compared the efficacy of high versus standard dose of meropenem in ventilator-associated pneumonia (VAP). ; Methods: 24 out of 34 eligible patients were randomized to receive meropenem 3 g q8h (high dose group, 11 patients) or 2 g q8h (standard-dose group, 13 patients) as a 3h infusion. The primary outcome was considered as clinical success that was defined as stable hemodynamic, improved sequential organ failure assessment (SOFA) score, stable or improved PaO2/FiO2 after 7 days. Sputum culture was taken before the intervention. ; Results: Clinical success rate was not significantly different between the high and standard-dose group (54.5% vs. 38.5%, P= 0.431). There was a significant difference in the reduction of clinical pulmonary infection score (CPIS) compared to a high dose to the standard group (P=0.038). SOFA score declined significantly in the high dose group throughout the study (P=0.006). A shorter duration of VAP treatment was recorded in the high dose group (P=0.061). We did not observe any significant adverse event related to meropenem. Acinetobacter spp. (34.8%), Klebsiella spp. (32.6%) and Pseudomonas aeruginosa (19.5%) isolated more frequently from sputum cultures. ; Conclusion: Treatment with the high dose of meropenem seems to be safe. However, it did not provide a significantly higher clinical success rate in comparison with the standard dose, but could be considered as an appropriate empirical treatment in patients with severe infection due to reduction in SOFA and CPIS. ; The trial protocol was registered with IRCT.ir (registration number IRCT2010010700 3014N19 in April 2018).

Study on the related risk factors and targeted nursing effects in multi-drug resistant bacteria infections in elderly patients with stroke-associated pneumonia

PURPOSE

to explore the related risk factors and targeted nursing effects in multi-drug resistant bacteria (MDRB) infection in elderly patients with stroke-associated pneumonia.

METHODS

We selected 100 elderly patients with MDRB who received SAP in the hospital encephalology department from May 2011 to November 2014, and pathogenic detection and drug susceptibility tests were performed on the specimens sent for inspection. In addition, we observed the pathogenic characteristics of MDRB, and carried out univariate and multivariate regression analysis of related risk factors. The infected patients were randomly divided into a control group and an intervention group, each with 50 cases. The control group received routine nursing care, and the intervention group received targeted nursing interventions, and the nursing effect of the two groups of patients was compared and analyzed.

RESULTS

A total of 112 drug-resistant bacteria were isolated from 100 SAP patients; gram-positive bacteria accounted for 22.3%, gram-negative bacteria accounted for 74.1%, fungi accounted for 3.6%. The multi-factor analysis showed that SAP type, ICU admission, gastric catheter retention, length of hospital stay, prophylactic use of antibiotics and disturbance of consciousness are risk factors associated with MDRB. The total effective rate of the control group was 50.0%, and the total effective rate of the intervention group was 74.0%, the difference between the two groups was statistically significant (P<0.05).

CONCLUSION

The pathogens causing MDRB in elderly SAP patients are mainly gram-negative bacteria, and there are many risk factors for developing MDRB in SAP patients, and targeted nursing measures can significantly improve the prognosis of patients with MDRB infection.

Efficacy of sub-MIC level of meropenem and ciprofloxacin against extensive drug-resistant (XDR) Pseudomonas aeruginosa isolates of diabetic foot ulcer patients

The increasing emergence of extensive drug-resistant bacteria (XDR) among chronic diabetic foot ulcer patients (DFU) possess serious threat which leads to foot amputation. The ideal measurement estimations of the presently accessible medications are getting insufficient against extensive drug-resistant strains. For quite a long-time piperacillin monotherapy, Piperacillin-tazobactam, ceftazidime, Carbapenem class of anti-toxin, ceftalozane-Tazobactam, and so on, has been the suggested therapy towards persistent instances of diabetic foot ulcer but because of the resistance mechanism of the potent pathogens the potency and usage of the antibiotic concentration regime is under the radar. Based on this hypothesis two isolates namely VIT PC 7 &VIT PC 9 were found to be resistant to all five classes of antibiotics exhibiting extensive drug resistance (XDR). The whole-genome sequence of Pseudomonas aeruginosa VIT PC 7 and VIT PC 9 data showed the presence of various RND efflux related genes and antibiotic resistance genes. The broth microdilution assay showed minimum inhibitory concentration (MIC) for ciprofloxacin and meropenem, Synergistic test was performed through checkerboard analysis and sub-MIC concentration of ciprofloxacin/meropenem was deduced using ∑ FICI, Time kills analysis was done for varying time interval to check the maximum reduction in CFU/ml of the bacterial cells, sub-MIC level of meropenem and ciprofloxacin showed inhibitory activity at lower concentration respectively. In vitro time-kill analysis showed the decrease in the number of cells, suggesting that the synergistic antimicrobial combinations are effective in decreasing the MIC level, and combinational test involving sub-MIC level of antibiotics also showed maximum reduction in biofilm forming cells, portraying the effectiveness of both the drugs. Accordingly, an expansion in the antimicrobial spectrum can be accomplished by utilizing the ideal measurements of ciprofloxacin/meropenem in persistent condition like diabetic foot ulcer, sub-MIC level of ciprofloxacin/meropenem could be a promising choice for anticipation against the ongoing drug-resistant crisis.

Mobile Carbapenemase Genes in Pseudomonas aeruginosa

Carbapenem-resistant Pseudomonas aeruginosa is one of the major concerns in clinical settings impelling a great challenge to antimicrobial therapy for patients with infections caused by the pathogen. While membrane permeability, together with derepression of the intrinsic beta-lactamase gene, is the global prevailing mechanism of carbapenem resistance in P. aeruginosa, the acquired genes for carbapenemases need special attention because horizontal gene transfer through mobile genetic elements, such as integrons, transposons, plasmids, and integrative and conjugative elements, could accelerate the dissemination of the carbapenem-resistant P. aeruginosa. This review aimed to illustrate epidemiologically the carbapenem resistance in P. aeruginosa, including the resistance rates worldwide and the carbapenemase-encoding genes along with the mobile genetic elements responsible for the horizontal dissemination of the drug resistance determinants. Moreover, the modular mobile elements including the carbapenemase-encoding gene, also known as the P. aeruginosa resistance islands, are scrutinized mostly for their structures.

Proteomic Analysis of Proteins Associated with Inhibition of Pseudomonas aeruginosa Resistance to Imipenem Mediated by the Chinese Herbal Medicine Qi Gui Yin

Objective: Antibiotic resistance of Pseudomonas aeruginosa (PA) that lowers the effectiveness of current treatments for pneumonia is a growing problem. Qi Gui Yin is a Chinese herbal medicine that has been used to improve the efficacy of antibiotic therapy against antibiotic-resistant bacteria. This study aimed to elucidate the mechanism by which Qi Gui Yin inhibits antibiotic resistance of PA. Methods: Active components of Qi Gui Yin were analyzed by chromatography. Isobaric Tags for Relative and Absolute Quantification (iTRAQ) technology was used to compare protein expression profiles of PA strains cultured in serum from rats that were and were not treated with Qi Gui Yin. Quantitative polymerase chain reaction (qPCR) analysis was performed to detect gene expression changes. Results: Proteomic analysis identified 76 differentially expressed proteins between PA strains cultured in serum from rats that were or were not treated with Qi Gui Yin. Bioinformatics analysis revealed that the largest number of differentially expressed proteins were associated with resistance mechanisms such as quorum sensing, bacterial biofilm formation, and active pumping. In addition, qPCR analysis confirmed that downregulation of iscU and arcA gene expression was associated with Qi Gui Yin treatment. Conclusions: Serum from Qi Gui Yin-treated rats could effectively inhibit antibiotic resistance of PA. Chlorogenic acid and astragaloside IV are the main components of Qi Gui Yin, which may mediate inhibition of antibiotic resistance. Our findings provide new insights into strategies involving Chinese herbal medicine that can be used to treat pneumonia caused by antibiotic-resistant bacteria.

Novel therapeutic strategies for treating Pseudomonas aeruginosa infection

INTRODUCTION

Persistent infections caused by the superbug Pseudomonas aeruginosa and its resistance to multiple antimicrobial agents are huge threats to patients with cystic fibrosis as well as those with compromised immune systems. Multidrug-resistant P. aeruginosa has posed a major challenge to conventional antibiotics and therapeutic approaches, which show limited efficacy and cause serious side effects. The public demand for new antibiotics is enormous; yet, drug development pipelines have started to run dry with limited targets available for inventing new antibacterial drugs. Consequently, it is important to uncover potential therapeutic targets.

AREAS COVERED

The authors review the current state of drug development strategies that are promising in terms of the development of novel and potent drugs to treat P. aeruginosa infection.

EXPERT OPINION

The prevention of P. aeruginosa infection is increasingly challenging. Furthermore, targeting key virulence regulators has great potential for developing novel anti-P. aeruginosa drugs. Additional promising strategies include bacteriophage therapy, immunotherapies, and antimicrobial peptides. Additionally, the authors believe that in the coming years, the overall network of molecular regulatory mechanism of P. aeruginosa virulence will be fully elucidated, which will provide more novel and promising drug targets for treating P. aeruginosa infections.

Synergistic activities of ceftazidime-avibactam in combination with different antibiotics against colistin-nonsusceptible clinical strains of Pseudomonas aeruginosa

Background: This study aims to analyse the effect of ceftazidime-avibactam plus various antibiotics against multidrug-resistant (MDR) Pseudomonas aeruginosa isolated from Intensive Care Units.Methods: 40 non-duplicate P. aeruginosa isolates were screened for their MICs of ceftazidime, ceftazidime-avibactam, colistin, levofloxacin, doripenem and tobramycin. MICs were determined by the broth microdilution method. The in vitro bactericidal activities of ceftazidime-avibactam compared to studied antibiotics were also determined by time-kill curve assays both at 1xMIC and at 4xMIC against carbapenemase-producing or -not producing six colistin-nonsusceptible MDR clinical strains of P. aeruginosa. Additionally, synergistic interactions were investigated by the time-kill curve assay.Results: The MIC₉₀ values for ceftazidime, ceftazidime-avibactam, colistin, levofloxacin, doripenem and tobramycin against MDR P. aeruginosa isolates were found to be >256, 64, 8, 64, 128, and >256 mg/L, respectively. The minimum bactericidal concentration₉₀ values for those antibiotics were also >256, 64, 16, 128, 256, and >256 mg/L, respectively. While doripenem, tobramycin and levofloxacin were bactericidal (>3 log₁₀ killing) against the 2/6, 3/6 and 1/6 P. aeruginosa isolates at 4xMIC concentrations, respectively, levofloxacin and tobramycin were bactericidal against only one isolate (1/6) at 1xMIC concentrations at 24 h. The synergistic interactions of these antimicrobial agents were also achieved with ceftazidime/avibactam + colistin (4/6), ceftazidime/avibactam + tobramycin (3/6), and ceftazidime/avibactam + levofloxacin (3/6) combinations. No antagonism was observed against studied P. aeruginosa strains.Conclusions: The findings of this study suggest that ceftazidime/avibactam with colistin, or tobramycin, were effective against colistin-nonsusceptible strains. This combination therapy could be an alternative antibiotic therapy for resistant P. aeruginosa strains.

Multidrug-resistant Pseudomonas aeruginosa and mortality in mechanically ventilated ICU patients

BACKGROUND

The link between bacterial resistance and prognosis remains controversial. Predominant pathogen causing ventilator-associated pneumonia (VAP) is Pseudomonas aeruginosa (Pa), which has increasingly become multidrug resistant (MDR). The aim of this study was to evaluate the relationship between MDR VAP Pa episodes and 30-day mortality.

METHODS

From a longitudinal prospective French multicenter database (2010-2016), Pa VAP onset and physiological data were recorded. MDR was defined as non-susceptibility to at least 1 agent in 3 or more antimicrobial categories. To analyze if MDR episodes were associated with greater in-hospital 30-day mortality, we performed a multivariate survival analysis using the multivariate nonlinear frailty model.

RESULTS

A total of 230 patients presented 286 Pa VAP. A maximum of 3 episodes per patient was observed; 73 episodes were MDR and 213 were susceptible. In the multivariate model, factors independently associated with 30-day mortality included hospitalization in the 6 months preceding the first episode (hazard ratio [HR], 2.31; 95% confidence interval [CI], 1.50-3.60; P = .0002), chronic renal failure (HR, 2.34; 95% CI, 1.15-4.77; P = .0196), and Pa VAP recurrence (HR, 2.29; 95% CI, 1.79-4.87; P = .032). Finally, MDR Pa VAP was not associated with death (HR, 0.87; 95% CI; 0.52-1.45; P = .59).

CONCLUSIONS

This study did not identify a relationship between the resistance profile of Pseudomonas aeruginosa and mortality.

The Efficacy and Safety of Doripenem in the Treatment of Acute Bacterial Infections-A Systemic Review and Meta-Analysis of Randomized Controlled Trials

This study aims to assess the efficacy and safety of doripenem on treating patients with acute bacterial infections. The Pubmed, Embase, and Cochrane databases were searched up to April 2019. Only randomized clinical trials comparing doripenem and other comparators for the treatment of acute bacterial infection were included. The primary outcome was the clinical success rate and the secondary outcomes were microbiological eradication rate and risk of adverse events. Eight randomized controlled trials (RCTs) were included. Overall, doripenem had a similar clinical success rate with comparators (odds ratio [OR], 1.15; 95% CI, 0.79-1.66, I2 = 58%). Similar clinical success rates were noted between doripenem and comparators for pneumonia (OR, 0.84; 95% CI, 0.46-1.53, I² = 72%) and for intra-abdominal infections (OR, 1.00; 95% CI, 0.57-1.72). For complicated urinary tract infection, doripenem was associated with higher success rate than comparators (OR, 1.89, 95% CI, 1.13-3.17, I² = 0%). The pool analysis comparing doripenem and other carbapenems showed no significant differences between each other (OR, 0.96, 95% CI, 0.59-1.58, I² = 63%). Doripenem also had a similar microbiological eradication rate with comparators (OR, 1.08; 95% CI, 0.86-1.36, I² = 0%). Finally, doripenem had a similar risk of treatment-emergent adverse events as comparators (OR, 0.98; 95% CI, 0.83-1.17, I² = 33%). In conclusion, the clinical efficacy of doripenem is as high as that of the comparator drugs in the treatment of acute bacterial infection; furthermore, this antibiotic is as well tolerated as the comparators.

Management of ventilator-associated pneumonia (VAP) caused by resistant gram-negative bacteria: which is the best strategy to treat?

Introduction: Treatment of ventilator-associated pneumonia (VAP) is a major challenge. The increase in multi-drug resistant bacteria has not been accompanied by the validation of new drugs, or by any new antimicrobial strategies to exploit the available agents. VAP due to Gram-negative bacteria has increased mortality, both due to the resistant pathogens themselves and due to inappropriate treatment. Local epidemiology, patients' characteristics and clinical responses provide the most important information for therapeutic decision-making. Moreover, data on VAP therapy due to resistant bacteria are lacking, and the choice of treatment is often based on clinical practice and individual experience. Areas covered: This review summarizes the strategies available for treating the three most prevalent resistant Gram-negative organisms causing VAP: Pseudomonas aeruginosa, Acinetobacter baumannii and Enterobacteriaceae. The review covers the results of a Pubmed search, clinical practice guidelines and reviews, and the authors' experience. Expert opinion: The existing evidence focuses on bloodstream infections or other sites rather than pneumonia and there are no recommendations for the treatment of VAP by multi-drug resistant Gram-negative bacteria, especially for combination regimens. The approval of new drugs is needed to provide effective and safe alternatives for treating carbapenemase-producing strains. Precision medicine and personalized approach are also fundamental in future research.

Repair Process Impairment by Pseudomonas aeruginosa in Epithelial Tissues: Major Features and Potential Therapeutic Avenues

Epithelial tissues protecting organs from the environment are the first-line of defense against pathogens. Therefore, efficient repair mechanisms after injury are crucial to maintain epithelial integrity. However, these healing processes can be insufficient to restore epithelial integrity, notably in infectious conditions. Pseudomonas aeruginosa infections in cutaneous, corneal, and respiratory tract epithelia are of particular concern because they are the leading causes of hospitalizations, disabilities, and deaths worldwide. Pseudomonas aeruginosa has been shown to alter repair processes, leading to chronic wounds and infections. Because of the current increase in the incidence of multi-drug resistant isolates of P. aeruginosa, complementary approaches to decrease the negative impact of these bacteria on epithelia are urgently needed. Here, we review the recent advances in the understanding of the impact of P. aeruginosa infections on the integrity and repair mechanisms of alveolar, airway, cutaneous and corneal epithelia. Potential therapeutic avenues aimed at counteracting this deleterious impact of infection are also discussed.

A Combination Antibiogram Evaluation for Pseudomonas aeruginosa in Respiratory and Blood Sources from Intensive Care Unit (ICU) and Non-ICU Settings in U.S. Hospitals

Pseudomonas aeruginosa is an important pathogen associated with significant morbidity and mortality. U.S. guidelines for the treatment of hospital-acquired and ventilator-associated pneumonia recommend the use of two antipseudomonal drugs for high-risk patients to ensure that ≥95% of patients receive active empirical therapy. We evaluated the utility of combination antibiograms in identifying optimal anti-P. aeruginosa drug regimens. We conducted a retrospective cross-sectional analysis of the antimicrobial susceptibility of all nonduplicate P. aeruginosa blood and respiratory isolates collected between 1 October 2016 and 30 September 2017 from 304 U.S. hospitals in the BD Insights Research Database. Combination antibiograms were used to determine in vitro rates of susceptibility to potential anti-P. aeruginosa combination regimens consisting of a backbone antibiotic (an extended-spectrum cephalosporin, carbapenem, or piperacillin-tazobactam) plus an aminoglycoside or fluoroquinolone. Single-agent susceptibility rates for the 11,701 nonduplicate P. aeruginosa isolates ranged from 72.7% for fluoroquinolones to 85.0% for piperacillin-tazobactam. Susceptibility rates were higher for blood isolates than for respiratory isolates (P < 0.05). Antibiotic combinations resulted in increased susceptibility rates but did not achieve the goal of 95% antibiotic coverage. Adding an aminoglycoside resulted in higher susceptibility rates than adding a fluoroquinolone; piperacillin-tazobactam plus an aminoglycoside resulted in the highest susceptibility rate (93.3%). Intensive care unit (ICU) isolates generally had lower susceptibility rates than non-ICU isolates. Commonly used antipseudomonal drugs, either alone or in combination, did not achieve 95% coverage against U.S. hospital P. aeruginosa isolates, suggesting that new drugs are needed to attain this goal. Local institutional use of combination antibiograms has the potential to optimize empirical therapy of infections caused by difficult-to-treat pathogens.

Evaluation of carbapenem use in a tertiary hospital: antimicrobial stewardship urgently needed

Background

China launched a 3-year rectification scheme for the clinical use of antibiotics in 2011, and a specific scheme for carbapenem use in 2017. The aim of this study was to investigate the effects of government policies on carbapenem use, and their correlation with carbapenem-resistant Pseudomonas aeruginosa (CRPA).

Methods

The study was divided into four stages: preintervention (2010), antimicrobial programme (2011-2013), post-antimicrobial programme (2014-2016) and carbapenem programme (2017). A point-score system was proposed for evaluating the rationality of carbapenem use, and evaluated based on the indications, microbial culture, single dose, interval, and duration. Any prescription without a global score of 10 points was judged as irrational. The trend was analyzed by regression analysis, and Spearman correlation analysis was used for testing the correlation.

Findings

The rate of rational use of carbapenems was 29.7% in 2010, and increased by 55.5, 45.2, and 51.5% during the subsequent three stages. The rationality declined slightly during the post-antimicrobial programme (2014-2016) while the consumption of carbapenems was markedly increased. These two parameters improved slightly in 2017. Moreover, the prevalence of CRPA was significantly negatively correlated with the rate of rational carbapenem use (Coefficient = - 0.553, P < 0.05), and not with the consumption of carbapenems (P > 0.05).

Conclusions

The rational application of carbapenems was related to government policies in this study, with irrational carbapenem use possibly related to the development of CRPA. The current point-score system could be a useful tool for performing assessments.

Antibiotic resistance in Pseudomonas aeruginosa: mechanisms and alternative therapeutic strategies

Pseudomonas aeruginosa is an opportunistic pathogen that is a leading cause of morbidity and mortality in cystic fibrosis patients and immunocompromised individuals. Eradication of P. aeruginosa has become increasingly difficult due to its remarkable capacity to resist antibiotics. Strains of Pseudomonas aeruginosa are known to utilize their high levels of intrinsic and acquired resistance mechanisms to counter most antibiotics. In addition, adaptive antibiotic resistance of P. aeruginosa is a recently characterized mechanism, which includes biofilm-mediated resistance and formation of multidrug-tolerant persister cells, and is responsible for recalcitrance and relapse of infections. The discovery and development of alternative therapeutic strategies that present novel avenues against P. aeruginosa infections are increasingly demanded and gaining more and more attention. Although mostly at the preclinical stages, many recent studies have reported several innovative therapeutic technologies that have demonstrated pronounced effectiveness in fighting against drug-resistant P. aeruginosa strains. This review highlights the mechanisms of antibiotic resistance in P. aeruginosa and discusses the current state of some novel therapeutic approaches for treatment of P. aeruginosa infections that can be further explored in clinical practice.

The Combination of Fosfomycin plus Meropenem Is Synergistic for Pseudomonas aeruginosa PAO1 in a Hollow-Fiber Infection Model

Treating high-density bacterial infections is a challenging clinical problem. We have a paucity of new agents that can address this problem. Pseudomonas aeruginosa is a particularly difficult pathogen to treat effectively because of the plethora of resistance mechanisms it carries. Fosfomycin is an agent discovered circa 40 years ago. Recently, it has been resurrected in the United States and studied for intravenous therapy. We hypothesized that, to maximize its utility, it would require combination chemotherapy when used in a clinical circumstance in high-bacterial-burden infections. We chose to examine the combination of meropenem plus fosfomycin. These agents were studied in the hollow-fiber infection model. We utilized a fully factorial study design, looking at 2 doses of meropenem alone (1 and 2 g 8-hourly) and two doses of fosfomycin alone (6 and 8 g 8-hourly), as well as all possible combinations plus a no-treatment control. We used a high-dimensional model of 5 inhomogeneous differential equations with 5 system outputs to analyze all data simultaneously. Combination therapy outperformed all monotherapy regimens, with all combinations driving >6 log₁₀ CFU/ml of bacterial killing. Combination therapy was able to counterselect resistance emergence (meropenem mutants being killed by the combination, as well as fosfomycin mutants being killed by the combination) in all regimens studied. The analysis demonstrated that the combination was significantly synergistic for bacterial cell killing and resistance suppression. Meropenem plus fosfomycin is a promising combination for therapy of high-burden Pseudomonas aeruginosa infections and requires further study.

Risk factors for hospitalized patients with resistant or multidrug-resistant Pseudomonas aeruginosa infections: a systematic review and meta-analysis

Background

Identifying risk factors predicting acquisition of resistant Pseudomonas aeruginosa will aid surveillance and diagnostic initiatives and can be crucial in early and appropriate antibiotic therapy. We conducted a systematic review examining risk factors of acquisition of resistant P. aeruginosa among hospitalized patients.

Methods

MEDLINE®, EMBASE®, and Cochrane Central were searched between 2000 and 2016 for studies examining independent risk factors associated with acquisition of resistant P. aeruginosa, among hospitalized patients. Random effects model meta-analysis was conducted when at least three or more studies were sufficiently similar.

Results

Of the 54 eligible articles, 28 publications (31studies) examined multi-drug resistant (MDR) or extensively drug resistant (XDR) P. aeruginosa and 26 publications (29 studies) examined resistant P. aeruginosa. The acquisition of MDR P. aeruginosa, as compared with non-MDR P. aeruginosa, was significantly associated with intensive care unit (ICU) admission (3 studies: summary adjusted odds ratio [OR] 2.2) or use of quinolones (4 studies: summary adjusted OR 3.59). Acquisition of MDR or XDR compared with susceptible P. aeruginosa was significantly associated with prior hospital stay (4 studies: summary adjusted OR 1.90), use of quinolones (3 studies: summary adjusted OR 4.34), or use of carbapenems (3 studies: summary adjusted OR 13.68). The acquisition of MDR P. aeruginosa compared with non-P. aeruginosa was significantly associated with prior use of cephalosporins (3 studies: summary adjusted OR 3.96), quinolones (4 studies: summary adjusted OR 2.96), carbapenems (6 studies: summary adjusted OR 2.61), and prior hospital stay (4 studies: summary adjusted OR 1.74). The acquisition of carbapenem-resistant P. aeruginosa compared with susceptible P. aeruginosa, was statistically significantly associated with prior use of piperacillin-tazobactam (3 studies: summary adjusted OR 2.64), vancomycin (3 studies: summary adjusted OR 1.76), and carbapenems (7 studies: summary adjusted OR 4.36).

Conclusions

Prior use of antibiotics and prior hospital or ICU stay was the most significant risk factors for acquisition of resistant P. aeruginosa. These findings provide guidance in identifying patients that may be at an elevated risk for a resistant infection and emphasize the importance of antimicrobial stewardship and infection control in hospitals.

Interpreting carbapenem susceptibility testing results for Pseudomonas aeruginosa

OBJECTIVES

Carbapenems are among the most powerful antipseudomonal agents. Limited data is available on drug susceptibility testing by routine methods (disc diffusion and Etest) for meropenem and doripenem. We aimed to compare the in vitro activity of imipenem, meropenem, and doripenem against Pseudomonas aeruginosa.

METHODS

A total of 311 P. aeruginosa strains isolated from respiratory specimens in 170 patients who developed ventilator-associated pneumonia in two intensive care units were collected over a period of 31 months. The susceptibility of these isolates to imipenem, meropenem, and doripenem were determined by Etest and disc diffusion method.

RESULTS

Considering either all isolates or only the first isolates recovered per patient (311 and 170 respectively), the susceptibility rate for doripenem was higher than that for meropenem and imipenem. When MICs determined by Etest were converted into interpretative categories (S, I, R) using French (CA-SFM) guidelines, a poor correlation was observed for meropenem and doripenem. The percentages of correlation with the disc diffusion method were 90.6% and 89.7% for imipenem, 80.5% and 82.6% for meropenem, and 80.5% and 73.3% for doripenem, for the first isolates and all isolates, respectively. The rate of minor errors was as high as 17.7% and 16.1% for meropenem and 17.7% and 25.7% for doripenem for the first isolates and all isolates, respectively.

CONCLUSION

The accuracy of disc diffusion using CA-SFM guidelines appears unsatisfactory for all three carbapenems justifying guideline update for P. aeruginosa and carbapenems.

A Questionnaire-based Survey of Physician Perceptions of the Prevalence of Antimicrobial Resistance and Their Antibiotic Prescribing Patterns

Background:

Antibiotic resistance is a serious problem being faced by physicians worldwide. This article was designed to study physician perceptions of antibiotic resistance and their prescribing patterns.

Materials and Methods:

A structured questionnaire was developed for reporting the prevalence of antibiotic resistance as perceived by physicians and recording their antibiotic preferences in specific contexts. A total of 539 intensivists across India participated in the study.

Results:

The prevalence of multidrug-resistant (MDR) Gram-negative pathogens was reported to be on the rise in Intensive Care Units. The prevalence rate of carbapenem-resistant Enterobacteriaceae was reported to be between 20% and 40% by 33% of the participants. Piperacillin-tazobactam was the preferred beta-lactam/beta-lactamase inhibitor antibiotic by the majority of intensivists (47%) in the treatment of infections caused by extended-spectrum beta-lactamase producers. Meropenem was recommended to be used at a higher dose (2 g t.i.d.) by 41% of intensivists for Pseudomonas/Acinetobacter infections with high minimum inhibitory concentration values for meropenem. De-escalation data revealed that 43% of intensivists “always” would like to de-escalate from carbapenems, based on the antibiotic susceptibility data. Minocycline was recommended by 33% for the treatment of ventilator-associated pneumonia (VAP) and by 21% for bloodstream infections caused by MDR Acinetobacter. Up to 83% of intensivists preferred the use of nebulized colistin for the management of VAP/hospital-acquired pneumonia.

Conclusion:

This study reveals that the prevalence of MDR Gram-negative pathogens is perceived to be on the rise. Prescription patterns indicate high levels of variability. Hence, antibiotic stewardship is essential to standardize antibiotic prescriptions not only for efficacy but also to reduce the burden of multiple drug resistance.

Assessment of Doripenem, Meropenem, and Imipenem against Respiratory Isolates of Pseudomonas aeroginosa in a Tertiary Care Hospital of North India

OBJECTIVE

Pseudomonas aeruginosa is one of the leading pathogen causing healthcare-associated infections, particularly in immunocompromised and critically ill patients. The development of carbapenem resistance in P. aeruginosa infections is worrisome. Data specifically comparing the susceptibility of the three available carbapenems are lacking in the Indian subcontinent.

MATERIALS AND METHODS

We evaluated the minimum inhibitory concentrations (MICs) of the three commonly used carbapenems- imipenem, meropenem, and doripenem against, 435 P. aeruginosa isolates obtained from respiratory samples and compared their susceptibility patterns to determine the best possible carbapenem among those available that may be used in combination regimes.

RESULTS

Overall, 222 (51.0%) of isolates were susceptible to doripenem followed by imipenem 206 (47.3%) and meropenem 195 (44.8%), respectively. Two hundred and sixty-two (60.23%) strains were intermediate or resistant to at least one carbapenem. The MIC90 of all three carbapenems was >32 μg/ml while the MIC50 of meropenem was 16 μg/ml which was higher than MIC50 of both imipenem (4 μg/ml) and doripenem (2 μg/ml).

CONCLUSION

Our study revealed that doripenem exerted better in vitro activity against the tested bacteria compared to imipenem and meropenem, but the difference was not statistically significant.

Pseudomonas Endocarditis with an unstable phenotype: the challenges of isolate characterization and Carbapenem stewardship with a partial review of the literature

Background

Pseudomonas endocarditis is exceedingly rare, especially in patients without predisposing risks. We present such a case that included unexpected switches in antibacterial resistance profiles in two Pseudomonas aeruginosa (PA) strains with the same whole-genome sequence. The case also involved diagnostic and treatment challenges, such as issues with automated testing platforms, choosing the optimal aminoglycoside, minimizing unnecessary carbapenem exposure, and the need for faster, more informative laboratory tests.

Case presentation

On hospital day one (HD-1) a cefepime and piperacillin-tazobactam (FEP-TZP)-susceptible P. aeruginosa was isolated from the bloodstream of a 62-year-old man admitted for evaluation of possible endocarditis and treated with gentamicin and cefepime. On HD-2, his antibiotic regimen was changed to tobramycin and cefepime. On HD-11, he underwent aortic valve replacement, and P. aeruginosa was isolated from the explanted valve. Unexpectedly, it was FEP-TZP-resistant, so cefepime was switched to meropenem. On HD-14, in preparation for whole-genome sequencing (WGS), valve and blood isolates were removed from cryo-storage, re-cultured, and simultaneously tested with the same platforms, reagents, and inoculations previously used. Curiously, the valve isolate was now FEP-TZP-susceptible. WGS revealed that both isolates were phylogenetically identical, differing by a single nucleotide in a chemotaxis-encoding gene. They also contained the same resistance genes (bla_ADC35, aph(3′)-II, bla_OXA-50, catB7, fosA).

Conclusion

Repeated testing on alternate platforms and WGS did not definitively determine the resistance mechanism(s), which in this case, is most likely unstable de-repression of a chromosomal AmpC β-lactamase, porin alterations, or efflux upregulation, with reversion to baseline (non-efflux) transcription. Although sub-culture on specialized media to select for less fit (more resistant) colonies, followed by transcriptome analysis, and multiple sequence alignment, might have revealed the mechanism and better informed the optimal choice of β-lactam, such approaches are neither rapid, nor feasible for hospital laboratories. In this era of escalating drug resistance and dwindling antibiotics, use of the most potent anti-pseudomonals must be balanced with stewardship. Clinicians need access to validated genomic correlates of resistance, and faster, more informative diagnostics. Therefore, we placed these isolates and their sequences in the public domain for inclusion in the Pseudomonas pan-genome and database projects for further countermeasure development.

Frequency, associated factors and outcome of multi-drug-resistant intensive care unit-acquired pneumonia among patients colonized with extended-spectrum β-lactamase-producing Enterobacteriaceae

Background

We assessed prevalence, associated factors and prognosis of extended-spectrum beta-lactamase-producing Enterobacteriaceae pneumonia acquired in intensive care unit (ESBL-PE pneumonia) among carriers. Variables associated with nosocomial pneumonia caused by carbapenem-resistant bacteria (CRB) were also assessed.

Methods

A 6-year prospective study (May 2009–March 2015) in the medical ICU of an 850-bed university-affiliated hospital was conducted.

Results

Of the 6303 patients admitted, 843 (13.4%) had ESBL-PE carriage detected. Among carriers, 111 (13%) patients developed ICU-acquired pneumonia of whom 48 (43%) had ESBL-PE pneumonia (6% of carriers). By multivariable analysis, SAPS II at admission >43 [OR 2.81 (1.16–6.79)] and colonization with Enterobacter sp. or K. pneumoniae species [OR 10.96 (2.93–41.0)] were independent predictive factors for ESBL-PE pneumonia in colonized patients, whereas receipt of >2 days of amoxicillin/clavulanic acid during the ICU stay [OR 0.24 (0.08–0.71)] was protective. Patients with ESBL-PE pneumonia had a higher SOFA score (p = 0.037) and more frequent septic shock at pneumonia onset (p = 0.047). However, ESBL-PE pneumonia was not an independent predictor of mortality. Twenty-five patients had pneumonia caused by CRB. Chronic renal insufficiency, administration of third-generation cephalosporin within the past 3 months, acute respiratory distress syndrome before pneumonia and prior therapy with a carbapenem or fluoroquinolones were associated with CRB pneumonia in this selected population.

Conclusions

Although few ESBL-PE carriers developed ESBL-PE pneumonia overall, a high proportion of pneumonia were caused by ESBL-PE in carriers developing ICUAP. ESBL-PE pneumonia was not an independent predictor of mortality. As pneumonia caused by CRB is increasing, knowledge of factors associated with ESBL-PE or CRB pneumonia may help empiric therapy of pneumonia among ESBL-PE carriers.

Electronic supplementary material

The online version of this article (doi:10.1186/s13613-017-0283-4) contains supplementary material, which is available to authorized users.

Predicting and preventing antimicrobial resistance utilizing pharmacodynamics: part II Gram-negative bacteria

INTRODUCTION

Antimicrobial resistance is a serious health threat worldwide. Better understanding of exposure targets that could suppress resistance amplification is necessary to guide the dosing of currently available agents as well as new therapies in the drug development process. Areas covered: This review will discuss studies that focused on predicting development of resistance using the pharmacokinetic-pharmacodynamic approach and how to design dosing regimens that can successfully suppress resistance emergence in Gram-negative bacteria. Expert opinion: Pharmacokinetic-pharmacodynamic targets could provide useful insights to guide antimicrobial dosing to prevent resistance emergence. Exposure targets required for resistance suppression are higher than those for efficacy and might not be clinically feasible. Combination therapy is a possible approach to improve the efficacy and minimize the resistance emergence for difficult-to-treat infections.

Aerosolized tobramycin for Pseudomonas aeruginosa ventilator-associated pneumonia in patients with acute respiratory distress syndrome

BACKGROUND

Ventilator-associated pneumonia (VAP) due to Pseudomonas aeruginosa has a high mortality and recurrence rate, especially in patients with acute respiratory distress syndrome (ARDS). Therefore, new therapeutic strategies against severe pneumonia are needed. This study evaluated the efficacy of aerosolized tobramycin for P. aeruginosa VAP in ARDS patients.

METHODS

A retrospective analysis was performed on patients who developed VAP caused by P. aeruginosa during the course of ARDS at the intensive care unit (ICU) of Kumamoto University Hospital. Aerosolized tobramycin inhalation solution (TIS) 240 mg was administered daily for 14 days in addition to systemic antibiotics.

RESULTS

A total of 44 patients (TIS group, n = 22; control group, n = 22) were included in the analysis. No significant differences were found between the two groups in terms of clinical characteristics, including acute physiology and chronic health evaluation II score upon ICU admission. The TIS group had significantly lower recurrence of P. aeruginosa VAP (22.7% vs. 52.4%, P = 0.04) and ICU mortality (22.7% vs. 63.6%, P < 0.01) than the control group. Bacterial concentration in tracheal aspirate (mean log 10 cfu/mL ± SD on days 2-5: 1.2 ± 1.3 vs. 5.0 ± 2.3, P < 0.01) decreased more rapidly and markedly in the TIS group compared with the control group.

CONCLUSION

Aerosolized tobramycin was an effective therapeutic strategy for P. aeruginosa VAP patients with ARDS.

Management of Adults With Hospital-acquired and Ventilator-associated Pneumonia: 2016 Clinical Practice Guidelines by the Infectious Diseases Society of America and the American Thoracic Society

It is important to realize that guidelines cannot always account for individual variation among patients. They are not intended to supplant physician judgment with respect to particular patients or special clinical situations. IDSA considers adherence to these guidelines to be voluntary, with the ultimate determination regarding their application to be made by the physician in the light of each patient's individual circumstances.These guidelines are intended for use by healthcare professionals who care for patients at risk for hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP), including specialists in infectious diseases, pulmonary diseases, critical care, and surgeons, anesthesiologists, hospitalists, and any clinicians and healthcare providers caring for hospitalized patients with nosocomial pneumonia. The panel's recommendations for the diagnosis and treatment of HAP and VAP are based upon evidence derived from topic-specific systematic literature reviews.

From lead optimization to NDA approval for a new antimicrobial: Use of pre-clinical effect models and pharmacokinetic/pharmacodynamic mathematical modeling

Because of our current crisis of resistance, particularly in nosocomial pathogens, the discovery and development of new antimicrobial agents has become a societal imperative. Changes in regulatory pathways by the Food and Drug Administration and the European Medicines Agency place great emphasis on the use of preclinical models coupled with pharmacokinetic/pharmacodynamic analysis to rapidly and safely move new molecular entities with activity against multi-resistant pathogens through the approval process and into the treatment of patients. In this manuscript, the use of the murine pneumonia system and the Hollow Fiber Infection Model is displayed and the way in which the mathematical analysis of the data arising from these models contributes to the robust choice of dose and schedule for Phase 3 clinical trials is shown. These data and their proper analysis act to de-risk the conduct of Phase 3 trials for anti-infective agents. These trials are the most expensive part of drug development. Further, given the seriousness of the infections treated, they represent the riskiest element for patients. Consequently, these preclinical model systems and their proper analysis have become a central part of accelerated anti-infective development. A final contention of this manuscript is that it is possible to embed these models and in particular, the Hollow Fiber Infection Model earlier in the drug discovery/development process. Examples of 'dynamic driver switching' and the impact of this phenomenon on clinical trial outcome are provided. Identifying dynamic drivers early in drug discovery may lead to improved decision making in the lead optimization process, resulting in the best molecules transitioning to clinical development.

Optimization of Polymyxin B in Combination with Doripenem To Combat Mutator Pseudomonas aeruginosa

Development of spontaneous mutations in Pseudomonas aeruginosa has been associated with antibiotic failure, leading to high rates of morbidity and mortality. Our objective was to evaluate the pharmacodynamics of polymyxin B combinations against rapidly evolving P. aeruginosa mutator strains and to characterize the time course of bacterial killing and resistance via mechanism-based mathematical models. Polymyxin B or doripenem alone and in combination were evaluated against six P. aeruginosa strains: wild-type PAO1, mismatch repair (MMR)-deficient (mutS and mutL) strains, and 7,8-dihydro-8-oxo-deoxyguanosine system (GO) base excision repair (BER)-deficient (mutM, mutT, and mutY) strains over 48 h. Pharmacodynamic modeling was performed using S-ADAPT and facilitated by SADAPT-TRAN. Mutator strains displayed higher mutation frequencies than the wild type (>600-fold). Exposure to monotherapy was followed by regrowth, even at high polymyxin B concentrations of up to 16 mg/liter. Polymyxin B and doripenem combinations displayed enhanced killing activity against all strains where complete eradication was achieved for polymyxin B concentrations of >4 mg/liter and doripenem concentrations of 8 mg/liter. Modeling suggested that the proportion of preexisting polymyxin B-resistant subpopulations influenced the pharmacodynamic profiles for each strain uniquely (fraction of resistance values are -8.81 log10 for the wild type, -4.71 for the mutS mutant, and -7.40 log10 for the mutM mutant). Our findings provide insight into the optimization of polymyxin B and doripenem combinations against P. aeruginosa mutator strains.

Microbial profiling of dental plaque from mechanically ventilated patients

Micro-organisms isolated from the oral cavity may translocate to the lower airways during mechanical ventilation (MV) leading to ventilator-associated pneumonia (VAP). Changes within the dental plaque microbiome during MV have been documented previously, primarily using culture-based techniques. The aim of this study was to use community profiling by high throughput sequencing to comprehensively analyse suggested microbial changes within dental plaque during MV. Bacterial 16S rDNA gene sequences were obtained from 38 samples of dental plaque sampled from 13 mechanically ventilated patients and sequenced using the Illumina platform. Sequences were processed using Mothur, applying a 97 % gene similarity cut-off for bacterial species level identifications. A significant ‘microbial shift’ occurred in the microbial community of dental plaque during MV for nine out of 13 patients. Following extubation, or removal of the endotracheal tube that facilitates ventilation, sampling revealed a decrease in the relative abundance of potential respiratory pathogens and a compositional change towards a more predominantly (in terms of abundance) oral microbiota including Prevotella spp., and streptococci. The results highlight the need to better understand microbial shifts in the oral microbiome in the development of strategies to reduce VAP, and may have implications for the development of other forms of pneumonia such as community-acquired infection.

Could the DiversiLab® semi-automated repetitive-sequence-based PCR be an acceptable technique for typing isolates ofPseudomonas aeruginosa? An answer from our experience and a review of the literature

Recently the DiversiLab® (DL) system (bioMérieux) was developed as an automated platform that uses repetitive element polymerase chain reaction (rep-PCR) technology for standardized, reproducible DNA fingerprinting of bacteria. The purpose of this study was to evaluate the usefulness of DL rep-PCR for typing Pseudomonas aeruginosa isolates. The performance of DL rep-PCR was compared with that of pulsed-field gel electrophoresis (PFGE) in a prospective multicenter study of patients with ventilator-associated pneumonia due to P. aeruginosa, conducted in 3 intensive care units over a 31-month period. In total, 203 P. aeruginosa isolates from 66 patients, from whom at least 2 consecutive respiratory samples each were collected more than 48 h apart, were typed using DL rep-PCR. Forty isolates (corresponding to 20 patients) were also typed using PFGE of SpeI-digested DNA. The typeability was 100% with DL rep-PCR and 95% with PFGE. The discriminatory power was close for DL rep-PCR and for PFGE (Simpson’s diversity indices of 0.901 and 0.947, respectively). Insufficient agreement between DL rep-PCR and PFGE typing results was observed for the 40 selected isolates (adjusted Rand coefficient of 0.419), mostly due to isolates of the same DL rep-PCR type but of different PFGE types (adjusted Wallace coefficients of 0.306 for DL rep-PCR with PFGE, and of 0.667 for PFGE with DL rep-PCR). Considered together with published data, DL rep-PCR results should be interpreted with caution for the investigation of outbreaks caused by P. aeruginosa and evaluated in conjunction with epidemiological data.

Antibacterial activity of achievable epithelial lining fluid exposures of Amikacin Inhale with or without meropenem

OBJECTIVES

While Amikacin Inhale (BAY41-6551), an integrated drug-device combination under development, achieves an estimated amikacin epithelial lining fluid (ELF) concentration of ∼ 5000 mg/L, its target site pharmacodynamics are unknown. We evaluated the pharmacodynamics of ELF exposure of inhaled amikacin ± meropenem.

METHODS

ELF exposures of inhaled amikacin (400 mg every 12 h), intravenous meropenem (2 g every 8 h) and a combination of both were studied in an in vitro pharmacodynamic model. Seven Klebsiella pneumoniae and 10 Pseudomonas aeruginosa with amikacin/meropenem MICs of 1 to 32,768/≤ 0.125 to >128 mg/L were included. Efficacy was assessed over 24-72 h.

RESULTS

The mean ± SD 0 h bacterial density was 6.5 ± 0.1 log10 cfu/mL. Controls grew to 8.0 ± 0.5 log10 cfu/mL by the end of the experiments. Simulation of inhaled amikacin monotherapy rapidly achieved and sustained bactericidal activity near the limit of detection over 24 h for all 13 isolates with amikacin MIC ≤ 256 mg/L except only ∼ 2 log10 cfu/mL reduction was observed in K. pneumoniae 375 (amikacin/meropenem MIC 64/32 mg/L) and P. aeruginosa 1544 (amikacin/meropenem MIC 64/128 mg/L). No activity was seen against the three isolates with amikacin MIC ≥ 2048 mg/L. Among the six isolates tested with meropenem monotherapy, five (meropenem MIC ≥ 16 mg/L) grew similarly to the controls while one (meropenem MIC 2 mg/L) achieved ∼ 2.5 log10 cfu/mL decrease. Among seven isolates tested in combination, four (amikacin/meropenem MIC ≤ 64/32 mg/L), including K. pneumoniae 375, maintained limit of detection until 72 h, whereas P. aeruginosa 1544 sustained a 1 log reduction. Combination therapy had no activity against the two isolates with amikacin MIC ≥ 2048 mg/L.

CONCLUSIONS

Inhaled amikacin monotherapy showed bactericidal activity against most isolates tested with amikacin MICs ≤ 256 mg/L. Adjunct inhaled amikacin plus meropenem sustained this activity for 72 h for the tested isolates with amikacin/meropenem MIC ≤ 64/32 mg/L.

In vitro Antibacterial Activity of Doripenem against Gram-Negative Blood Isolates in a Korean Tertiary Care Center

Background

Doripenem is the most recently introduced antimicrobial agent of the carbapenem class. It is a valuable therapeutic option in the context of increasing antimicrobial resistance to imipenem and meropenem among gram-negative bacilli (GNB) clinical isolates. However, clinicians are usually reluctant to prescribe doripenem, because susceptibility to doripenem is not automatically reported by most clinical laboratories and the in vitro activity of doripenem against clinically significant GNB isolates remains uncertain.

Materials and Methods

We investigated the in vitro antibacterial activity of doripenem in GNB blood isolates in a tertiary care center. Over a period of 10 months, 212 adult bacteremia cases were treated at the study hospital. Doripenem susceptibility testing was performed for the 212 blood isolates by the disk diffusion method, and clinical data were collected.

Results

Among the blood isolates, the rate of doripenem resistance (7.5%) was lower than that of imipenem (12.9%) or other anti-GNB antimicrobial agents, except amikacin (2.1%). Almost all imipenem-susceptible GNB blood isolates (181/182, 99.5%) were susceptible to doripenem. Whereas doripenem resistance was rarely observed in Enterobacteriaceae (2/181, 1.1%), it was frequently observed in patients with non-fermentatative GNB (12/27, 44.4%), hospital-acquired infections (7/27, 25.9%), and pneumonia (11/49, 22.4%).

Conclusion

Doripenem exhibited more potent in vitro activity against GNB blood isolates than other anti-GNB antimicrobial agents in a tertiary care center where it was infrequently prescribed compared with other carbapenems. However, its clinical utility may be limited due to the increasing number of carbapenem-resistant non-fermentative GNB infections.

Clinical evaluation of the need for carbapenems to treat community-acquired and healthcare-associated pneumonia

Carbapenems have an overall broad antibacterial spectrum and should be protected against from the acquisition of drug resistance. The clinical advantages of carbapenem in cases of pneumonia have not been certified and the need for antipseudomonal antimicrobial agents to treat healthcare-associated pneumonia (HCAP) remains controversial. We introduced an antimicrobial stewardship program for carbapenem and tazobactam/piperacillin use and investigated the effects of this program on the clinical outcomes of 591 pneumonia cases that did not require intensive care unit management, mechanical ventilation or treatment with vasopressor agents [221 patients with community-acquired pneumonia (CAP) and 370 patients with HCAP]. Compared with the pre-intervention period, age, comorbidities and the severity and etiology of pneumonia did not differ during the intervention period. Carbapenems were rarely used during the intervention period in cases of pneumonia (CAP: 12% vs. 1%, HCAP: 13% vs. 1%), while antipseudomonal beta-lactam use was reduced from 33% to 8% among cases with HCAP. This reduction in the rate of carbapenem administration did not have an impact on the prognosis in the cases of CAP, and the in-hospital mortality was lower among the patients with HCAP during the intervention period (15% vs. 5%, p = 0.013). The causes of death in the cases of HCAP were not directly related to pneumonia during the intervention period. The current study shows that carbapenem use can be avoided in cases of CAP or HCAP that are not in a critical condition. The frequent use of antipseudomonal beta-lactams does not improve the clinical outcomes of HCAP.

How to treat VAP due to MDR pathogens in ICU patients

Background

The increasing occurrence of multidrug resistant (MDR) bacteria arises at a time when there is a lack of antibiotics active against these pathogens and few new antimicrobials are in the pipelines of the pharmaceutical industry. Treatment of ventilator-associated pneumonia (VAP) caused especially by MDR Gram-negative bacilli (GNB) represents a real challenge due to the dearth of treatment options.

Methods

We searched the medical literature relevant about management of ventilator-associated pneumonia caused by multi-drug resistant pathogens including GNB and methicillin-resistant S. aureus.

Results

Empirical therapy should be prescribed based on the local pattern of susceptibilities. Colistin and tigecycline are in many cases the unique options for the treatment of many episodes of VAP caused by MDR-GNB. Tigecyline (not licensed for treatment of pneumonia) should be used with an initial bolus of 200 mg followed by 100 mg every 12 h. The need for a loading dose and the administration of high doses of colistin (9 million IU/day in two or three doses) is currently accepted. Vancomycin has been considered the treatment of choice for pneumonia due to MRSA although linezolid may provide higher rate of clinical cure for MRSA VAP with a good safety profile. The initial antibiotic treatment must be reassessed and simplify in accordance of culture results.

Conclusions

Empirical treatment of VAP due to MDR pathogens should be based on knowledge of local ecology. A strategy combining early high doses of effective agents with subsequent simplification in the light of microbiologic information is recommended.

Combination treatment with meropenem plus levofloxacin is synergistic against Pseudomonas aeruginosa infection in a murine model of pneumonia

BACKGROUND

Meropenem plus levofloxacin treatment was shown to be a promising combination in our in vitro hollow fiber infection model. We strove to validate this finding in a murine Pseudomonas pneumonia model.

METHODS

A dose-ranging study with meropenem and levofloxacin alone and in combination against Pseudomonas aeruginosa was performed in a granulocytopenic murine pneumonia model. Meropenem and levofloxacin were administered to partially humanize their pharmacokinetic profiles in mouse serum. Total and resistant bacterial populations were estimated after 24 hours of therapy. Pharmacokinetic profiling of both drugs was performed in plasma and epithelial lining fluid, using a population model.

RESULTS

Meropenem and levofloxacin penetrations into epithelial lining fluid were 39.3% and 64.3%, respectively. Both monotherapies demonstrated good exposure responses. An innovative combination-therapy analytic approach demonstrated that the combination was statistically significantly synergistic (α = 2.475), as was shown in the hollow fiber infection model. Bacterial resistant to levofloxacin and meropenem was seen in the control arm. Levofloxacin monotherapy selected for resistance to itself. No resistant subpopulations were observed in any combination therapy arm.

CONCLUSIONS

The combination of meropenem plus levofloxacin was synergistic, producing good bacterial kill and resistance suppression. Given the track record of safety of each agent, this combination may be worthy of clinical trial.

Antibiotic stewardship in the intensive care unit

The rapid emergence and dissemination of antimicrobial-resistant microorganisms in ICUs worldwide constitute a problem of crisis dimensions. The root causes of this problem are multifactorial, but the core issues are clear. The emergence of antibiotic resistance is highly correlated with selective pressure resulting from inappropriate use of these drugs. Appropriate antibiotic stewardship in ICUs includes not only rapid identification and optimal treatment of bacterial infections in these critically ill patients, based on pharmacokinetic-pharmacodynamic characteristics, but also improving our ability to avoid administering unnecessary broad-spectrum antibiotics, shortening the duration of their administration, and reducing the numbers of patients receiving undue antibiotic therapy. Either we will be able to implement such a policy or we and our patients will face an uncontrollable surge of very difficult-to-treat pathogens.