The efficacy and safety of tigecycline for the treatment of bloodstream infections: a systematic review and meta-analysis

Risk factors for bloodstream infection among patients admitted to an intensive care unit of a tertiary hospital of Shanghai, China

Blood flow infections (BSIs) is common occurrences in intensive care units (ICUs) and are associated with poor prognosis. The study aims to identify risk factors and assess mortality among BSI patients admitted to the ICU at Shanghai Ruijin hospital north from January 2022 to June 2023. Additionally, it seeks to present the latest microbiological isolates and their antimicrobial susceptibility. Independent risk factors for BSI and mortality were determined using the multivariable logistic regression model. The study found that the latest incidence rate of BSI was 10.11%, the mortality rate was 35.21% and the mean age of patients with BSI was 74 years old. Klebsiella pneumoniae was the predominant bacterial isolate. Logistic multiple regression revealed that tracheotomy, tigecycline, gastrointestinal bleeding, shock, length of hospital stay, age and laboratory indicators (such as procalcitonine and hemoglobin) were independent risk factors for BSI. Given the elevated risk associated with use of tracheotomy and tigecycline, it underscores the importance of the importance of cautious application of tracheostomy and empirical antibiotic management strategies. Meanwhile, the independent risk factors of mortality included cardiovascular disease, length of hospital stay, mean platelet volume (MPV), uric acid levels and ventilator. BSI patients exhibited a significant decrease in platelet count, and MPV emerged as an independent factor of mortality among them. Therefore, continuous monitoring of platelet-related parameters may aid in promptly identifying high-risk patients and assessing prognosis. Moreover, monitoring changes in uric acid levels may serve as an additional tool for prognostic evaluation in BSI patients.

Monotherapy vs combination therapy in patients with Klebsiella pneumoniae bloodstream infection: A systematic review and meta-analysis

OBJECTIVE

To determine whether mortality is lower in patients with Klebsiella pneumoniae bloodstream infection (BSI) who receive combination antimicrobial therapy than in those who receive monotherapy.

METHODS

Two authors independently searched for relevant articles in the PubMed, Embase, Web of Science, and Cochrane Library databases through to August 10, 2023. Risk of bias was evaluated using the ROBINS-I tool. Possible sources of heterogeneity were evaluated by meta-regression using a mixed-effects model.

RESULTS

Among 8044 articles screened, there were 23 studies (3443 patients) that were eligible for meta-analysis. Meta-regression analysis identified the proportion of patients with carbapenem-resistant Klebsiella pneumoniae (CRKP) BSI to be a potential source of heterogeneity. Subgroup analysis showed that mortality on monotherapy was significantly higher when the proportion of patients with CRKP BSI was ≥50% (OR 1.75, 95% CI 1.33-2.30) and significantly lower when this proportion was <50% (OR 0.55, 95% CI 0.24-1.24). Overall mortality was significantly higher on tigecycline monotherapy (OR 2.86, 95% CI 1.46-5.59) than on combination therapy containing both these agents. There was a trend in favor of colistin/polymyxin B-containing combination therapy (OR 1.37, 95% CI 0.83-2.28).

CONCLUSIONS

Combination antimicrobial therapy can lower mortality in patients with CRKP but may not show a survival advantage over monotherapy when the proportion of patients with CRKP BSI is <50%. High-quality prospective observational studies are needed because of the high risk of bias and limited data in the studies performed to date.

Colistin-induced structural and biochemical changes in carbapenem-resistant Acinetobacter baumannii isolated from the hospital environment

BACKGROUND

Acinetobacter baumannii is an emerging multidrug-resistant bacterium and is considered as one of the important causes of nosocomial infections.

OBJECTIVES

The main objectives are to determine the drug-resistant pattern of beta-lactamase-producing A. baumannii, colistin-induced structural and biochemical changes.

METHODS

A. baumannii strains were isolated from the restrooms using the selective media, viz., restroom door, restroom floor, washing area, and restroom tap. A total of 120 samples were collected from all four sampling sites. These strains and their drug-resistance patterns were identified. Then carbapenem-resistance was analyzed and the occurrence of the drug-resistant gene (blaOXA-23) was determined. Colistin was applied at various concentrations (20 - 100 µg/mL) and the molecular mechanism of A. baumannii was analysed.

RESULTS

The bacterial population was high on doors (53 ± 2 CFU/mL), followed by restroom tap (19 ± 1 CFU/mL), restroom floor (14 ± 3 CFU/mL), and washing area (3 ± 0 CFU/mL), respectively. A total of 343 A. baumannii strains were isolated from the 120 samples obtained for one year from the restroom. The isolated bacteria showed resistance to selected carbapenems, with 100% isolates being resistant to imipenem, followed by cefotaxime (1.4 ± 0.2% susceptibility). More blaOXA-23 gene carrying strains were isolated from restroom tap(89 ± 2.1%) than other sources. Colistin exhibited bactericidal activity against drug-resistant A. baumannii. Treating A. baumannii strain with 100 µg/mL colistin induced cell membrane roughness in vitro. Scanning Electron Microscopy (SEM) analysis revealed moderate cell shrinkage after treatment with colistin. Bacterial cells treated with hydrogen peroxide or colistin for 30 min induced the production of hydroxyl radicals. The bacterial lysis increased fluorescence and hydroxyl radicals, and released cellular protein and sugars.

CONCLUSIONS

The isolated A. baumannii was resistant to imipenem and showed susceptibility to colistin. Colistin disrupted cell membrane in drug-resistant A. baumannii in vitro. The regular screening for drug-resistance among A. baumannii strains can help monitor the outbreak of A. baumannii and manage control measures.

Clinical efficacy and safety of tigecycline based on therapeutic drug monitoring for carbapenem-resistant Gram-negative bacterium pneumonia in intensive care units

BACKGROUND

We investigated the associations between the different doses of tigecycline, its efficacy and safety, and the role of tigecycline therapeutic drug monitoring for patients in the intensive care unit.

METHODS

This study was a single-center cohort including patients infected with multidrug-resistant Acinetobacter baumannii (MDR-AB) and multidrug-resistant Klebsiella pneumoniae (MDR-KP) causing pulmonary infections. The steady-state plasma concentration after tigecycline administration was determined by High-Performance Liquid Chromatography (HPLC) in patients admitted to the ICU between October 2020 and December 2021. Multivariate analyses of tigecycline's clinical efficacy and safety were performed to control confounding factors.

RESULTS

For this study, we included 45 patients and 45 blood samples to determine steady-state trough concentrations of tigecycline. All patients were divided into the High Dose (HD) and Standard Dose (SD) groups. The median trough concentration of tigecycline was 0.56 μg/mL in the HD group, which was higher than in the SD group (0,21 μg/mL), p = 0.000. There was no significant difference between the two groups of patients in terms of bacterial eradication rate, mortality rate, and clinical efficacy. Multiple regression analysis showed that the ICU days were correlated with mortality OR 1.030(1.005-1.056), p = 0.017. APACHE II was significantly associated with clinical efficacy OR 0.870(0.755-1.002), p = 0.045. The level of fibrinogen decline in the HD group was significantly higher than in the SD group (-3.05 ± 1.67 vs -1.75 ± 1.90), p = 0.038. We identified that age and tigecycline treatment duration influenced fibrinogen decline.

CONCLUSIONS

Tigecycline plasma concentrations are significantly increased when using a high dose. However, the plasma concentration of tigecycline is not correlated with clinical efficacy and adverse reactions. Fibrinogen decline appears to be related to the patient's age and days of tigecycline. Large sample data are still needed to confirm the clinical guidance significance of tigecycline TDM.

Tigecycline as salvage treatment of febrile neutropenia in patients with haematological malignancies-a retrospective single-centre analysis of 200 cases

Tigecycline has been used to treat patients with febrile neutropenia (FN). This study aims to analyse the effectiveness of tigecycline as salvage treatment of FN. Patients records from 09/2004 to 04/2019 were reviewed. Cases were eligible if fever persisted/recurred (p/r-FN) after 3 days of second-line treatment with a carbapenem, and were divided into three groups: switch to tigecycline (TGC group), switch to other antibiotics (OAB group), and no switch (W&W group). The primary endpoint was response rate (defervescence for ≥ 7 days or at least until discharge); the key secondary endpoint was 30-day mortality rate. Two hundred cases from 176 patients (median 59 years; 53.5% men) treated were included, mostly acute myeloid leukaemias (61.0%). 45.5% of cases were in the TGC group (in combination with an anti-pseudomonal antibiotic, mostly ceftazidime [95.6%]); 35.5% were in the OAB and 19.0% in the W&W group. There was no significant difference in response rates (TGC, 73.6%; OAB, 62.0%; W&W, 78.9%; p = 0.12) or 30-day mortality rates (TGC, 7.7%; OAB, 7.0%; W&W, 5.3%; p = 0.94). Tigecycline plus an anti-pseudomonal antibiotic does not improve response or 30-day mortality rate compared to other antibiotics in patients with p/r-FN. Also, in some cases, no switch in antibiotics may be necessary at all.

Antimicrobial activity of cinnamaldehyde against multidrug-resistant Klebsiella pneumoniae: an in vitro and in vivo study

The emergence and spread of multidrug-resistant (MDR) Klebsiella pneumoniae strains have increased worldwide, posing a significant health threat by limiting the therapeutic options. This study aimed to investigate the antimicrobial potential of cinnamaldehyde against MDR-K. pneumoniae strains in vitro and in vivo assays. The presence of resistant genes in MDR- K. pneumoniae strains were evaluated by Polymerase Chain Reaction (PCR) and DNA sequencing. Carbapenem-resistant K. pneumoniae strains show the blaKPC-2 gene, while polymyxin-resistant K. pneumoniae presented blaKPC-2 and alterations in the mgrB gene. Cinnamaldehyde exhibited an inhibitory effect against all MDR- K. pneumoniae evaluated. An infected mice model was used to determine the in vivo effects against two K. pneumoniae strains, one carbapenem-resistant and another polymyxin-resistant. After 24 h of cinnamaldehyde treatment, the bacterial load in blood and peritoneal fluids decreased. Cinnamaldehyde showed potential effectiveness as an antibacterial agent by inhibiting the growth of MDR-K. pneumoniae strains.

Therapeutics for Vancomycin-Resistant Enterococcal Bloodstream Infections

Vancomycin-resistant enterococci (VRE) are common causes of bloodstream infections (BSIs) with high morbidity and mortality rates. They are pathogens of global concern with a limited treatment pipeline. Significant challenges exist in the management of VRE BSI, including drug dosing, the emergence of resistance, and the optimal treatment for persistent bacteremia and infective endocarditis. Therapeutic drug monitoring (TDM) for antimicrobial therapy is evolving for VRE-active agents; however, there are significant gaps in the literature for predicting antimicrobial efficacy for VRE BSIs. To date, TDM has the greatest evidence for predicting drug toxicity for the three main VRE-active antimicrobial agents daptomycin, linezolid, and teicoplanin. This article presents an overview of the treatment options for VRE BSIs, the role of antimicrobial dose optimization through TDM in supporting clinical infection management, and challenges and perspectives for the future.

Population pharmacokinetics of tigecycline in critically ill patients

Objective: In critically ill patients, the change of pathophysiological status may affect the pharmacokinetic (PK) process of drugs. The purpose of this study was to develop a PK model for tigecycline in critically ill patients, identify the factors influencing the PK and optimiz dosing regimens.

Method: The concentration of tigecycline was measured LC-MS/MS. We established population PK model with the non-linear mixed effect model and optimized the dosing regimens by Monte Carlo simulation.

Result: A total of 143 blood samples from 54 patients were adequately described by a one-compartment linear model with first-order elimination. In the covariate screening analysis, the APACHEII score and age as significant covariates. The population-typical values of CL and Vd in the final model were 11.30 ± 3.54 L/h and 105.00 ± 4.47 L, respectively. The PTA value of the standard dose regimen (100 mg loading dose followed by a 50 mg maintenance dose at q12 h) was 40.96% with an MIC of 2 mg/L in patients with HAP, the ideal effect can be achieved by increasing the dosage. No dose adjustment was needed for Klebsiella pneumoniae for AUC0–24/MIC targets of 4.5 and 6.96, and the three dose regimens almost all reached 90%. A target AUC0–24/MIC of ≥17.9 reached 100% in patients with cSSSI in the three tigecycline dose regimens, considering MIC ≤ 0.25 mg/L.

Conclusion: The final model indicated that APACHEII score and age could affect the Cl and Vd of tigecycline, respectively. The standard dose regimen of tigecycline was often not able to obtain satisfactory therapeutic effects for critically ill patients. For patients with HAP and cIAI caused by one of three pathogens, the efficacy rate can be improved by increasing the dose, but for cSSSI infections caused by Acinetobacter baumannii and K. pneumoniae, it is recommended to change the drug or use a combination of drugs.

Evaluation of Tigecycline Utilization and Trends in Antibacterial Resistance from 2018 to 2021 in a Comprehensive Teaching Hospital in China

Purpose

Tigecycline, the first glycylcycline antibiotic, which was widely used for off-label indications because of its broad-spectrum antibacterial activity. This study evaluated the indications for clinical use of tigecycline, clinical and microbiological effectiveness, factors associated with in hospital mortality, and bacterial resistance.

Methods

This retrospective study evaluated all inpatients who received tigecycline treatment for >72 hours between January 2018 and December 2021 in a comprehensive teaching hospital in China. The evaluation included indications, administration regimen, etiology, efficacy and so on. Univariate and multivariate analyses were used to evaluate the risk factors for all-cause mortality.

Results

There were 203 patients treated with tigecycline. Tigecycline was commonly prescribed for off-label indications (83.25%, 169/203), and hospital-acquired pneumonia ranked first (79.29%, 134/169). The most common pathogen was Acinetobacter baumannii. Clinical and microbiological success was 57.14% (116/203) and 32.28% (41/127), respectively. Fifty-four patients died and all-cause mortality was 26.60%. Univariate and multivariate analyses showed no significant difference in age, gender, off-label indication, duration of treatment, combination with other drugs, multidrug-resistant or extensively drug-resistant infections and tigecycline application scoring with respect to mortality.

Conclusion

Although detection of A. baumannii has decreased in the past 4 years in our hospital, resistance to tigecycline has increased. For clinical application, physicians attach importance to detection of pathogenic microorganisms, but there is still empirical medication without bacterial culture reports. Therefore, an antibiotic stewardship program oriented toward tigecycline should be strengthened to curb bacterial resistance.

Recommendations and guidelines for the treatment of infections due to multidrug resistant organisms

Antimicrobial drug resistance is one of the major threats to global health. It has made common infections increasingly difficult or impossible to treat, and leads to higher medical costs, prolonged hospital stays and increased mortality. Infection rates due to multidrug-resistant organisms (MDRO) are increasing globally. Active agents against MDRO are limited despite an increased in the availability of novel antibiotics in recent years. This guideline aims to assist clinicians in the management of infections due to MDRO. The 2019 Guidelines Recommendations for Evidence-based Antimicrobial agents use in Taiwan (GREAT) working group, comprising of infectious disease specialists from 14 medical centers in Taiwan, reviewed current evidences and drafted recommendations for the treatment of infections due to MDRO. A nationwide expert panel reviewed the recommendations during a consensus meeting in Aug 2020, and the guideline was endorsed by the Infectious Diseases Society of Taiwan (IDST). This guideline includes recommendations for selecting antimicrobial therapy for infections caused by carbapenem-resistant Acinetobacter baumannii, carbapenem-resistant Pseudomonas aeruginosa, carbapenem-resistant Enterobacterales, and vancomycin-resistant Enterococcus. The guideline takes into consideration the local epidemiology, and includes antimicrobial agents that may not yet be available in Taiwan. It is intended to serve as a clinical guide and not to supersede the clinical judgment of physicians in the management of individual patients.

Population Pharmacokinetics of Tigecycline: A Systematic Review

Although tigecycline is widely used in clinical practice, its efficiency and optimal dosage regimens remain controversial. The purpose of this article was to help guide tigecycline dosing in different patient subpopulations through comparing the published population pharmacokinetic models of tigecycline, as well as summarizing and determining the potential covariates that markedly influence tigecycline pharmacokinetics. In this review, literature was systematically searched from the PubMed database from inception to March 2022. The articles focusing on population pharmacokinetics for tigecycline in healthy volunteers or patients were included; finally, a total of eight studies were included in this review. NONMEM methods were used in five studies to generate the population pharmacokinetic models. Tigecycline pharmacokinetics were mostly described by a two-compartment model in these included studies. Estimated clearance and volumes of distribution of tigecycline at steady state (Vss) varied widely in different target patient populations, with a range of 7.5–23.1 L/h and 212.7–1087.7 L, respectively. Body-weight and creatinine clearance were the most important predictors of clearance in these studies, while other predictors include age, gender, bilirubin and aspartate aminotransferase. In conclusion, this review showed the large variability of tigecycline population pharmacokinetics, which can provide guide dosing in different target populations. For clinicians, the individual dosing adjustment should be based not only on the indication and pathogen susceptibility but also on the potential important predictors. However, more studies were needed to confirm the necessity of modified dosage regimens in different patient subpopulations.

Cefiderocol- Compared to Colistin-Based Regimens for the Treatment of Severe Infections Caused by Carbapenem-Resistant Acinetobacter baumannii

Cefiderocol may represent a therapeutic option for carbapenem-resistant Acinetobacter baumannii (CRAB) infections, but clinical data are limited. This is an observational retrospective study conducted in the University Hospital of Pisa including consecutive patients with CRAB infections (January 2020 to August 2021). Patients were divided in two study groups according to the antibiotic treatment received: cefiderocol- and colistin-containing regimens. The primary outcome was the 30-day mortality. A Cox regression analysis was performed to identify factors independently associated with 30-day mortality. A propensity score analysis using inverse probability of treatment weighting (IPTW) was also performed. A total of 124 patients were included: 47 (37.9%) received cefiderocol, while 77 (62.1%) colistin-containing regimens. Overall, 79 (63.7%) patients had a bloodstream infection (BSI), 35 (28.5%) a ventilator-associated pneumonia (VAP) and 10 (8.1%) other infections. Thirty-day mortality was higher in patients receiving colistin- compared to those who received cefiderocol-containing regimens (55.8% versus 34%, P = 0.018). This difference was confirmed in patients with BSI, but not in those with VAP. On multivariable analysis, septic shock, SOFA score, and age were independently associated with 30-day mortality, while cefiderocol therapy was protective in an IPTW analysis (Hazard ratio 0.44, 95% confidence interval 0.22-0.66, P < 0.001). Nephrotoxicity was more common in the colistin group. Microbiological failure occurred in 17.4% of patients receiving cefiderocol versus 6.8% of those receiving colistin (P = 0.079). Among 8 cases in the cefiderocol group who experienced microbiological failure, 4 (50%) developed resistance to cefiderocol. Cefiderocol represents a promising therapeutic option in patients with severe CRAB infections. Randomized clinical trial in this specific patient population should confirm our findings.

Isolation and Characterization of a Novel Autographiviridae Phage and Its Combined Effect with Tigecycline in Controlling Multidrug-Resistant Acinetobacter baumannii-Associated Skin and Soft Tissue Infections

Multidrug-resistant Acinetobacter baumannii (MDR A. baumannii) is one of the ESKAPE pathogens that restricts available treatment options. MDR A. baumannii is responsible for a dramatic increase in case numbers of a wide variety of infections, including skin and soft tissue infections (SSTIs), resulting in pyoderma, surgical debridement, and necrotizing fasciitis. To investigate an alternative medical treatment for SSTIs, a broad range lytic Acinetobacter phage, vB _AbP_ABWU2101 (phage vABWU2101), for lysing MDR A. baumannii in associated SSTIs was isolated and the biological aspects of this phage were investigated. Morphological characterization and genomic analysis revealed that phage vABWU2101 was a new species in the Friunavirus, Beijerinckvirinae, family Autographiviridae, and order Caudovirales. Antibiofilm activity of phage vABWU2101 demonstrated good activity against both preformed biofilms and biofilm formation. The combination of phage vABWU2101 and tigecycline showed synergistic antimicrobial activities against planktonic and biofilm cells. Scanning electron microscopy confirmed that the antibacterial efficacy of the combination of phage vABWU2101 and tigecycline was more effective than the phage or antibiotic alone. Hence, our findings could potentially be used to develop a therapeutic option for the treatment of SSTIs caused by MDR A. baumannii.

Efficacy of Tigecycline as Salvage Therapy in Multidrug-Resistant Febrile Neutropenia in Patients with Acute Leukemia—A Single Center Analysis

Severe infectious complications remain the main cause of mortality in leukemia patients due to a long period of profound neutropenia. Standardized regimens for antimicrobial, antifungal, and antiviral prophylaxis and therapy in neutropenic patients have improved infection-associated mortality. Nevertheless, many patients are refractory to these multidrug approaches. Tigecycline is a last-resort antibiotic with a broad-spectrum activity; unfortunately, clinical experience in multidrug-resistant febrile neutropenia is limited. The aim was to evaluate the efficacy of tigecycline treatment in comparison to standard treatment in this patient cohort. In this single center analysis, we analyzed the clinical courses of 73 patients with acute leukemia and diagnosis of febrile neutropenia resistant to hospital-based multidrug escalation levels who continued on a standard approach without antibiotics as the last resort (n = 30) or were switched to tigecycline in addition to carbapenem treatment (n = 43). We observed comparable overall response rates (decrease in C-reactive protein or resolution of fever) in both patient cohorts. Switching the antibiotic approach to tigecycline showed lower absolute sepsis (33% vs. 47%, p = 0.235) and infection-associated mortality rates (5% vs. 13%, p = 0.221). Prospective larger randomized studies are necessary to underline these results and to be able to generate reliable statistics.

European Society of clinical microbiology and infectious diseases (ESCMID) guidelines for the treatment of infections caused by Multidrug-resistant Gram-negative bacilli (endorsed by ESICM -European Society of intensive care Medicine)

SCOPE

These ESCMID guidelines address the targeted antibiotic treatment of 3^rd generation cephalosporin-resistant Enterobacterales (3GCephRE) and carbapenem-resistant Gram-negative bacteria, focusing on the effectiveness of individual antibiotics and on combination vs. monotherapy.

METHODS

An expert panel was convened by ESCMID. A systematic review was performed including randomized controlled trials and observational studies, examining different antibiotic treatment regimens for the targeted treatment of infections caused by the 3GCephRE, carbapenem-resistant Enterobacterales (CRE), carbapenem-resistant Pseudomonas aeruginosa (CRPA) and carbapenem-resistant Acinetobacter baumanni (CRAB). Treatments were classified as head-to-head comparisons between individual antibiotics and monotherapy vs. combination therapy regimens, including defined monotherapy and combination regimens only. The primary outcome was all-cause mortality, preferably at 30 days and secondary outcomes included clinical failure, microbiological failure, development of resistance, relapse/recurrence, adverse events and length of hospital stay. The last search of all databases was conducted in December 2019, followed by a focused search for relevant studies up until ECCMID 2021. Data were summarized narratively. The certainty of the evidence for each comparison between antibiotics and between monotherapy vs. combination therapy regimens was classified by the GRADE recommendations. The strength of the recommendations for or against treatments was classified as strong or conditional (weak).

RECOMMENDATIONS

The guideline panel reviewed the evidence per pathogen, preferably per site of infection, critically appraising the existing studies. Many of the comparisons were addressed in small observational studies at high risk of bias only. Notably, there was very little evidence on the effects of the new, recently approved, beta-lactam beta-lactamase inhibitors on infections caused by carbapenem-resistant Gram-negative bacteria. Most recommendations are based on very-low and low certainty evidence. A high value was placed on antibiotic stewardship considerations in all recommendations, searching for carbapenem-sparing options for 3GCephRE and limiting the recommendations of the new antibiotics for severe infections, as defined by the sepsis-3 criteria. Research needs are addressed.

An integrated approach to evaluate different tetracycline derivatives for formulary decisions

DISCLAIMER

In an effort to expedite the publication of articles, AJHP is posting manuscripts online as soon as possible after acceptance. Accepted manuscripts have been peer-reviewed and copyedited, but are posted online before technical formatting and author proofing. These manuscripts are not the final version of record and will be replaced with the final article (formatted per AJHP style and proofed by the authors) at a later time.

PURPOSE

Stenotrophomonas maltophilia has emerged as a critical opportunistic pathogen associated with significant morbidity and mortality. Tetracycline derivatives have been recognized as alternative treatment options, but they have varied pharmacokinetic properties. An integrated approach to different tetracycline derivatives for formulary decisions is reported.

METHODS

The minimum inhibitory concentration (MIC) data from clonally diverse bloodstream S. maltophilia isolates were examined, along with the pharmacokinetic profiles of 4 tetracycline derivatives, to predict achievable pharmacodynamic exposures with standard intravenous dosing regimens. Antimicrobial therapy was assessed using the ratio of daily drug acquisition cost relative to the ratio of the free-drug area under the time-concentration curve (fAUC) to the 90th percentile for minimum inhibitory concentration (MIC) values for isolates (fAUC/MIC90).

RESULTS

In our analysis, minocycline had the greatest fAUC/MIC90. Doxycycline was the most financially preferred agent, as calculated using 2020 average wholesale price for base-case estimates of drug acquisition cost.

CONCLUSION

An integrated evaluation for antimicrobial formulary decision-making addressed local susceptibility data, pharmacokinetics, pharmacodynamics, dosing regimens, and drug acquisition costs. This comprehensive method is more objective than the conventional approach and warrants validation.

In vitro pharmacodynamics of omadacycline against Escherichia coli and Acinetobacter baumannii

BACKGROUND

The pharmacodynamics of omadacycline have been extensively studied against Gram-positive pathogens but less information is available for Gram-negative pathogens. We describe the pre-clinical pharmacodynamics of omadacycline against Escherichia coli and Acinetobacter baumannii.

METHODS

An in vitro dilutional pharmacokinetic model was used. Exposure experiments with fAUC/MIC ratios ranging from 0 to 1200 were performed using five strains of E. coli and five strains of A. baumannii. Reduction in bacterial load and changes in population profiles were measured.

RESULTS

The fAUC/MIC targets against E. coli for 24 h static and -1 log reduction in load were 25.3 ± 17.2 and 42.7 ± 32.5, respectively. For A. baumannii the fAUC/MIC for 24 h static effect was 108.1 ± 38.6. Changes in population profiles were observed for E. coli at fAUC/MIC ratios of ≤200 and for A. baumannii up to 1200. MICs were increased 2-32 fold.

CONCLUSIONS

fAUC/MIC targets for A. baumannii are greater than for E.coli and changes in population profiles more likely. E. coli fAUC/MIC targets align with in vivo data and will be useful in determining omadacycline dosing for this pathogen.

Dose optimisation based on pharmacokinetic/pharmacodynamic target of tigecycline

Tigecycline, a new first-in-class glycylcycline antibiotic, has shown promising efficacy against a broad range of micro-organisms. It is widely prescribed for various infections, with most prescriptions being considered for off-label use. However, only a few years after its approval by the US Food and Drug Administration (FDA), tigecycline is suspected of increasing all-cause mortality. Some clinicians have suggested such unfavourable outcomes correlate with inadequate drug exposure at the infection site. The pharmacokinetic/pharmacodynamic (PK/PD) profile of a drug plays an important role in predicting its antibiotic effect, which for tigecycline is determined as the ratio of area under the concentration-time curve (AUC) to minimum inhibitory concentration (MIC). In this study, PK/PD targets based on infection sites, bacterial isolates and patient populations are discussed. Generally, a higher dosage of tigecycline for the treatment of serious infections has been recommended in previous reports. However, the latest finding of tigecycline's atypical protein binding property requires consideration when recommending further use. In addition, combination therapy with other antibiotics provides another option by potentially lowering the MICs of multidrug-resistant bacteria.

Treatment of invasive IMP-4 Enterobacter cloacae infection in transplant recipients using ceftazidime/avibactam with aztreonam: A case series and literature review

Infections caused by carbapenemase-producing Enterobacteriaceae (CPE) are an emerging threat in both solid organ and stem cell transplant recipients. Invasive CPE infections in transplant recipients are associated with a high mortality, often due to limited therapeutic options and antibacterial toxicities. One of the most therapeutically challenging group of CPE are the metallo-β-lactamase (MBL)-producing Gram-negative bacteria, which are now found worldwide, and often need treatment with older, highly toxic antimicrobial regimens. Newer β-lactamase inhibitors such as avibactam have well-established activity against certain carbapenemases such as Klebsiella pneumoniae carbapenemases (KPC), but have no activity against MBL-producing organisms. Conversely, aztreonam has activity against MBL-producing organisms but is often inactivated by other co-existing β-lactamases. Here, we report four cases of invasive MBL-CPE infections in transplant recipients caused by IMP-4-producing Enterobacter cloacae who were successfully treated with a new, mechanism-driven antimicrobial combination of ceftazidime/avibactam with aztreonam. This novel antimicrobial combination offers a useful treatment option for high-risk patients with CPE infection, with reduced drug interactions and toxicity.

Outcomes and prognostic factors of tigecycline treatment for hospital-acquired pneumonia involving multidrug-resistant Acinetobacter baumannii

Objective: To compare outcomes and prognostic factors of tigecycline (TC)-based treatment with those of other antibiotic-based treatments in the treatment of hospital-acquired pneumonia caused by multidrug-resistant Acinetobacter baumannii (MDRAB).

Methods: A retrospective analysis of data was performed from all patients ≥18 years who were treated in the ICU at Xiangya Hospital, Changsha, China (January 2016 to June 2017) with hospital-acquired pneumonia involving monomicrobial MDRAB. Patients were separated into TC and non-TC groups.

Results: Of 86 MDRAB-positive patients, 59 were in the TC group and 27 were in the non-TC group. The 28-day death rates were not significantly different between the two groups, but the TC group had significantly more patients with a good clinical prognosis than the non-TC group. Although prognostic markers for a poor clinical response were sepsis, procalcitonin concentration and APACHE II scores, TC therapy was found to be a protective factor.

Conclusions: TC based therapy was associated with a positive clinical response in the treatment of MDRAB caused hospital-acquired pneumonia. Further studies are required to confirm our results.

Bloodstream Infections Caused by Carbapenem-Resistant Enterobacterales: Risk Factors for Mortality, Antimicrobial Therapy and Treatment Outcomes from a Prospective Multicenter Study

Purpose

Carbapenem-resistant Enterobacterales bloodstream infections (CRE BSIs) have a high mortality. However, an optimal antimicrobial treatment has not been determined. This study was conducted to evaluate the risk factors for mortality and provided potential therapeutic options for treatment of CRE infection.

Patients and Methods

We investigated patients with CRE BSIs from 18 hospitals across nine Chinese provinces from January to December 2019. Data were collected from the medical records according to a pre-established questionnaire. Antimicrobial susceptibility testing and DNA sequencing were performed to investigate the characteristics of isolates.

Results

A total of 208 patients enrolled; the overall 30-day mortality rate was 46.2%. The causative pathogen was carbapenem-resistant Klebsiella pneumoniae (CRKP) (85.6%). Patients infected by ST11-KL64 CRKP had a high sepsis/septic shock incidence rate (p < 0.05). Sepsis/septic shock, short duration of antimicrobial therapy and empirical using tigecycline were independent risk factors for mortality (p < 0.05 for each risks). Appropriate therapy had better survival benefit than inappropriate therapy (p = 0.003). No difference was identified between monotherapy and combination therapy (p = 0.105). Tigecycline as a frequently used antimicrobial had poor therapeutic effect on BSI patients (p < 0.001). Carbapenem-based treatment had a better therapeutic effect on patients infected by isolates with meropenem MIC ≤ 8 mg/L (p = 0.022). The patients who received short duration of antimicrobial therapy had poorer prognosis (p < 0.001) than the patients who received long duration of antimicrobial therapy.

Conclusion

Reducing the mortality of CRE BSIs need to comprehensively consider whether the antimicrobials were used appropriately, together with infection severity and CRE strains.

Tigecycline antibacterial activity, clinical effectiveness, and mechanisms and epidemiology of resistance: narrative review

Tigecycline is unique glycylcycline class of semisynthetic antimicrobial agents developed for the treatment of polymicrobial infections caused by multidrug-resistant Gram-positive and Gram-negative pathogens. Tigecycline evades the main tetracycline resistance genetic mechanisms, such as tetracycline-specific efflux pump acquisition and ribosomal protection, via the addition of a glycyclamide moiety to the 9-position of minocycline. The use of the parenteral form of tigecycline is approved for complicated skin and skin structure infections (excluding diabetes foot infection), complicated intra-abdominal infections, and community-acquired bacterial pneumonia in adults. New evidence also suggests the effectiveness of tigecycline for the treatment of severe Clostridioides difficile infections. Tigecycline showed in vitro susceptibility to Coxiella spp., Rickettsia spp., and multidrug-resistant Neisseria gonnorrhoeae strains which indicate the possible use of tigecycline in the treatment of infections caused by these pathogens. Except for intrinsic, or often reported resistance in some Gram-negatives, tigecycline is effective against a wide range of multidrug-resistant nosocomial pathogens. Herein, we summarize the currently available data on tigecycline pharmacokinetics and pharmacodynamics, its mechanism of action, the epidemiology of tigecycline resistance, and its clinical effectiveness.

A glimpse of antimicrobial resistance gene diversity in kefir and yoghurt

Antimicrobial resistance (AMR) is a global threat gaining more and more practical significance every year. The main determinants of AMR are the antimicrobial resistance genes (ARGs). Since bacteria can share genetic components via horizontal gene transfer, even non-pathogenic bacteria may provide ARG to any pathogens which they become physically close to (e.g. in the human gut). In addition, fermented food naturally contains bacteria in high amounts. In this study, we examined the diversity of ARG content in various kefir and yoghurt samples (products, grains, bacterial strains) using a unified metagenomic approach. We found numerous ARGs of commonly used fermenting bacteria. Even with the strictest filter restrictions, we identified ARGs undermining the efficacy of aminocoumarins, aminoglycosides, carbapenems, cephalosporins, cephamycins, diaminopyrimidines, elfamycins, fluoroquinolones, fosfomycins, glycylcyclines, lincosamides, macrolides, monobactams, nitrofurans, nitroimidazoles, penams, penems, peptides, phenicols, rifamycins, tetracyclines and triclosan. In the case of gene lmrD, we detected genetic environment providing mobility of this ARG. Our findings support the theory that during the fermentation process, the ARG content of foods can grow due to bacterial multiplication. The results presented suggest that the starting culture strains of fermented foods should be monitored and selected in order to decrease the intake of ARGs via foods.

Impact of Tigecycline's MIC in the Outcome of Critically Ill Patients with Carbapenemase-Producing Klebsiella pneumoniae Bacteraemia Treated with Tigecycline Monotherapy-Validation of 2019's EUCAST Proposed Breakpoint Changes

Background: Tigecycline is a therapeutic option for carbapenemase-producing Klebsiella pneumoniae (CP-Kp). Our aim was to evaluate the impact of the tigecycline’s minimum inhibitory concentration (MIC) in the outcome of patients with CP-Kp bacteraemia treated with tigecycline monotherapy. Methods: Patients with monomicrobial bacteraemia due to CP-Kp that received appropriate targeted monotherapy or no appropriate treatment were included. Primary outcome was 30-day mortality. MICs of meropenem, tigecycline, and ceftazidime/avibactam were determined by Etest, whereas for colistin, the broth microdilution method was applied. PCR for bla_KPC, bla_VIM, bla_NDM, and bla_OXA genes was applied. Results: Among 302 CP-Kp bacteraemias, 32 isolates (10.6%) showed MICs of tigecycline ≤ 0.5 mg/L, whereas 177 (58.6%) showed MICs that were 0.75–2 mg/L. Colistin and aminoglycoside susceptibility was observed in 43.0% and 23.8% of isolates, respectively. The majority of isolates carried bla_KPC (249; 82.5%), followed by bla_VIM (26; 8.6%), both bla_KPC and bla_VIM (16; 5.3%), and bla_NDM (11; 3.6%). Fifteen patients with tigecycline MIC ≤ 0.5 mg/L and 55 with MIC 0.75–2 mg/L were treated with tigecycline monotherapy; 30-day mortality was 20.0% and 50.9%, respectively (p = 0.042). Mortality of 150 patients that received other antimicrobials was 24.7%; among 82 patients that received no appropriate treatment, mortality was 39.0%. No difference in 30-day mortality was observed between patients that received tigecycline (MIC ≤ 0.5 mg/L) or other antimicrobials. Conclusion: Tigecycline monotherapy was as efficacious as other antimicrobials in the treatment of bloodstream infections due to CP-Kp isolates with a tigecycline’s MIC ≤ 0.5 mg/L.

Treating infections caused by carbapenemase-producing Enterobacterales (CPE): a pragmatic approach to antimicrobial stewardship on behalf of the UKCPA Pharmacy Infection Network (PIN)

The emergence of carbapenemase-producing Enterobacterales (CPE) as a major cause of invasive infection both within the UK and internationally poses a very real concern for all providers of healthcare. The burden of morbidity and mortality associated with CPE infections is well described. The need for early, targeted, effective and safe antimicrobial therapy remains key for the management of these infected patients yet reliable antimicrobial treatment options remain scarce. In the absence of a universal treatment for these CPE invasive infections, individual treatment options tailored to susceptibilities and severity of infection are required. This working group from within the UK Clinical Pharmacy Association (UKCPA) Pharmacy Infection Network has developed evidence-based treatment recommendations to support infection specialists in managing these complex infections. A systematic review of peer-reviewed research was performed and analysed. We report consensus recommendations for the management of CPE-associated infections. The national expert panel makes therapeutic recommendations regarding the pharmacokinetic and pharmacodynamic properties of the drugs and pharmacokinetic targets, dosing, dosage adjustment and monitoring of parameters for novel and established antimicrobial therapies with CPE activity. This manuscript provides the infection specialist with pragmatic and evidence-based options for the management of CPE infections.

Biofilm-Formation in Clonally Unrelated Multidrug-Resistant Acinetobacter baumannii Isolates

This study analyzed the genotype, antibiotic resistance, and biofilm formation of Acinetobacter baumannii strains and assessed the correlation between biofilm formation, antibiotic resistance, and biofilm-related risk factors. A total of 207 non-replicate multi-drug-resistant A. baumannii strains were prospectively isolated. Phenotypic identification and antimicrobial susceptibility testing were carried out. Isolate biofilm formation ability was evaluated using the tissue culture plate (TCP), Congo red agar, and tube methods. Clonal relatedness between the strains was assessed by enterobacterial repetitive intergenic consensus-PCR genotyping. Of the 207 isolates, 52.5% originated from an intensive care unit setting, and pan resistance was observed against ceftazidime and cefepime, with elevated resistance (99–94%) to piperacillin/tazobactam, imipenem, levofloxacin, and ciprofloxacin. alongside high susceptibility to tigecycline (97.8%). The Tissue culture plate, Tube method, and Congo red agar methods revealed that 53.6%, 20.8%, and 2.7% of the strains were strong biofilm producers, respectively, while a significant correlation was observed between biofilm formation and device-originating respiratory isolates (p = 0.0009) and between biofilm formation in colonized vs. true infection isolates (p = 0.0001). No correlation was detected between antibiotic resistance and biofilm formation capacity, and the majority of isolates were clonally unrelated. These findings highlight the urgent need for implementing strict infection control measures in clinical settings.

In vitro efficacy of ceftazidime-avibactam, aztreonam-avibactam and other rescue antibiotics against carbapenem-resistant Enterobacterales from the Arabian Peninsula

OBJECTIVES

Our aim was to assess the susceptibility of carbapenem-resistant Enterobacterales (CRE) from the Arabian Peninsula to a broad spectrum of antibiotics, including fosfomycin, ceftazidime-avibactam, and aztreonam-avibactam.

METHODS

1192 non-repeat CRE isolated in 2009-2017 from 33 hospitals in five countries of the Arabian Peninsula were tested. The minimum inhibitory concentration of 14 antibiotics was determined. Carbapenemase and 16S methylase genes were detected by PCR. Clonality was assessed by PFGE.

RESULTS

The highest rate of susceptibility was detected to aztreonam-avibactam (95.5%) followed by colistin (79.8%), fosfomycin (71.8%) and tigecycline (59.9%). Isolates co-producing two carbapenemases (12.4%) were the least susceptible. Aminoglycoside susceptibility was affected by the frequent production of a 16S methylase. Susceptibility to ceftazidime-avibactam was impacted by the high rate of metallo-beta-lactamase producers (46.3%), while aztreonam-avibactam resistance occurred mostly in clonally unrelated, carbapenemase non-producing Escherichia coli.

CONCLUSION

Of the currently available drugs: colistin, tigecycline, and ceftazidime-avibactam co-administered with aztreonam appear to be the most effective to treat CRE infections. However, the presence of non-clonal CRE isolates, in which avibactam does not lower the aztreonam MIC below the clinical breakpoint, is of notable concern. Based on the relatively high rate of fosfomycin susceptibility, it would be desirable to license parenteral fosfomycin in the region.

Methicillin-resistant Staphylococcus aureus replication in the presence of high (≥32 µg/ml) drug concentration of vancomycin as seen by electron microscopy

Methicillin-resistant Staphylococcus aureus (MRSA) has unfortunately become a common pathogen in many healthcare facilities. In many institutions, vancomycin remains the preferred agent for treating serious MRSA infections including bacteraemia with or without endocarditis. The mutant prevention concentration (MPC) testing ≥10⁹ colony forming units of bacteria, describes the antimicrobial drug concentration blocking the growth of the least susceptible cell from high density bacterial populations. With blood culture isolates of MRSA, we discovered strains with MPC values ≥32 µg/ml and viable cells could be readily recovered from agar plates containing 32 µg/ml of vancomycin. To investigate MRSA strains surviving in high concentrations of vancomycin on drug containing agar plates, we utilized electron microscopy to measure cell wall thickness as this has been previously reported as a potential mechanism of resistance¹ along with septum thickening. Our data shows MRSA replication from high density bacterial populations in the presence of ≥32 µg/ml of vancomycin. Such observations may explain vancomycin failure in some patients and/or persistent bacteraemia and could potentially question the use of this drug in some critically ill patients in favour of an alternative agent.

Prevalence and Therapies of Antibiotic-Resistance in Staphylococcus aureus

Infectious diseases are the second most important cause of human death worldwide; Staphylococcus aureus (S. aureus) is a very common human pathogenic microorganism that can trigger a variety of infectious diseases, such as skin and soft tissue infections, endocarditis, osteomyelitis, bacteremia, and lethal pneumonia. Moreover, according to the sensitivity to antibiotic drugs, S. aureus can be divided into methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA). In recent decades, due to the evolution of bacteria and the abuse of antibiotics, the drug resistance of S. aureus has gradually increased, the infection rate of MRSA has increased worldwide, and the clinical anti-infective treatment for MRSA has become more difficult. Accumulating evidence has demonstrated that the resistance mechanisms of S. aureus are very complex, especially for MRSA, which is resistant to many kinds of antibiotics. Therefore, understanding the drug resistance of MRSA in a timely manner and elucidating its drug resistance mechanism at the molecular level are of great significance for the treatment of S. aureus infection. A large number of researchers believe that analyzing the molecular characteristics of S. aureus can help provide a basis for designing effective prevention and treatment measures against hospital infections caused by S. aureus and further monitor the evolution of S. aureus. This paper reviews the research status of MSSA and MRSA, the detailed mechanisms of the intrinsic antibiotic resistance and the acquired antibiotic resistance, the advanced research on anti-MRSA antibiotics and novel therapeutic strategies for MRSA treatment.

Early Experience With Eravacycline for Complicated Infections

Eravacycline (ERV) was used in 35 patients for various infections. The most common pathogen was Klebsiella pneumoniae, and 30-day survival was 74%. Absence of 30-day recurrence and resolution of signs and symptoms of infection were 91% and 57%, respectively. ERV was well-tolerated, with adverse events leading to drug discontinuation in one patient.

Effectiveness and Safety of High Dose Tigecycline for the Treatment of Severe Infections: A Systematic Review and Meta-Analysis

BACKGROUND

Studies assessing the effect of high dose tigecycline on severe infections are limited and remain controversial.

OBJECTIVES

To assess systematically the effectiveness and safety of high dose tigecycline in the treatment of severe infections.

METHODS

Pubmed, Web of Science, Embase, MEDLINE, Cochrane Library and ClinicalTrials were searched up to February 20, 2019 for studies that compared the effectiveness and safety of high dose tigecycline with standard dose tigecycline or other non-tigecycline-containing regimens in the treatment of severe infections. Rates for all-cause mortality, clinical cure, microbiological eradication and adverse events were analysed.

RESULTS

Ten studies with 593 patients were included. The results indicated that using high dose tigecycline resulted in better outcomes compared with controls with lower all-cause mortality (OR 0.44, 95% CI 0.30-0.66, p < 0.0001), higher clinical cure (OR 3.43, 95% CI 2.09-5.63, p < 0.00001), higher microbiological eradication (OR 2.25, 95% CI 1.44-3.50, p = 0.0003), and without increasing adverse events rates. Subgroup analysis showed that high dose tigecycline reduced all-cause mortality in nosocomial acquired pneumonia (OR 0.39, 95% CI 0.22-0.70, p = 0.002), bloodstream infections (OR 0.19, 95% CI 0.06-0.58, p = 0.004) and mixed infections (OR 0.20, 95% CI 0.07-0.59, p = 0.003), with no statistical differences in complicated intra-abdominal infections (OR 2.04, 95% CI 0.80-5.23, p = 0.14). In carbapenem-resistant pathogens, the microbiological eradication rate in those given high dose tigecycline did not differ from controls (OR 1.07, 95% CI 0.44-2.60, p = 0.87), although mortality was reduced (OR 0.20, 95% CI 0.09-0.45, p = 0.0001). The main limitation of the review is that most of the included studies are observational studies with small sample sizes and high risks of bias.

CONCLUSIONS

High dose tigecycline treatment is effective and safe for severe infections owing to its lower all-cause mortality, higher clinical cure, microbiological eradication and comparable adverse events. However, as a result of the high risks of bias of the included studies, well-designed randomised clinical trials are warranted to establish the effectiveness and safety of high dose tigecycline compared with standard dose tigecycline and other commonly used antibiotics.

Mortality from acinetobacter infections as compared to other infections among critically ill patients in South India: A prospective cohort study

Background

Acinetobacter baumannii has become a common pathogen causing hospital-acquired infections (HAIs). Although acquiring any nosocomial infection is associated with increased mortality, we do not know if the acquisition of Acinetobacter infection confers a worse prognosis as compared to non-Acinetobacter-related HAI. The aim of the current study is to compare the clinical outcomes of ventilator-associated pneumonia (VAP) and central line associated blood stream infections (CLABSIs) caused by A. baumannii with those caused by other bacterial pathogens.

Materials and Methods

This prospective cohort study was conducted among critically ill adults admitted to a tertiary care hospital in South India from January 2013 to June 2014. We enrolled patients who developed new-onset fever ≥48 h after admission and fulfilled pre-specified criteria for VAP or CLABSI. The patients were followed up until the primary outcomes of death or hospital discharge.

Results

During the study period, 4047 patients were admitted in the intensive care units, among which 129 eligible HAI events were analysed. Of these, 95 (73.6%) were VAP, 34 (26.4%) were CLABSI, 78 (60.4%) were A. baumannii-related HAI (AR-HAI) and 51 (39.6%) were non-A. baumannii-related HAI (NAR-HAI). Mortality among AR-HAI was 57.6% compared to 39.2% in NAR-HAI (P = 0.04) which on multivariate analysis did not achieve statistical significance, although the trend persisted (odds ratio [OR] = 4.2, 95% confidence interval [CI]: 0.95-18.4, P = 0.06). The acquisition of VAP due to A. baumannii was associated with poor ventilator outcomes even after adjusting for confounders (adjusted OR = 3.5, 95% CI: 1.07-11.6, P = 0.04).

Conclusion

In our cohort of critically ill adults with VAP and CLABSI, AR-HAI was associated with poor ventilator outcomes and a trend towards higher mortality. These findings add to the evidence suggesting that A. baumannii is a dangerous pathogen, perhaps even more so than others.

Prevalence and Therapies of Antibiotic-Resistance in Staphylococcus aureus

Infectious diseases are the second most important cause of human death worldwide; Staphylococcus aureus (S. aureus) is a very common human pathogenic microorganism that can trigger a variety of infectious diseases, such as skin and soft tissue infections, endocarditis, osteomyelitis, bacteremia, and lethal pneumonia. Moreover, according to the sensitivity to antibiotic drugs, S. aureus can be divided into methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA). In recent decades, due to the evolution of bacteria and the abuse of antibiotics, the drug resistance of S. aureus has gradually increased, the infection rate of MRSA has increased worldwide, and the clinical anti-infective treatment for MRSA has become more difficult. Accumulating evidence has demonstrated that the resistance mechanisms of S. aureus are very complex, especially for MRSA, which is resistant to many kinds of antibiotics. Therefore, understanding the drug resistance of MRSA in a timely manner and elucidating its drug resistance mechanism at the molecular level are of great significance for the treatment of S. aureus infection. A large number of researchers believe that analyzing the molecular characteristics of S. aureus can help provide a basis for designing effective prevention and treatment measures against hospital infections caused by S. aureus and further monitor the evolution of S. aureus. This paper reviews the research status of MSSA and MRSA, the detailed mechanisms of the intrinsic antibiotic resistance and the acquired antibiotic resistance, the advanced research on anti-MRSA antibiotics and novel therapeutic strategies for MRSA treatment.

Colistin-sparing approaches with newer antimicrobials to treat carbapenem-resistant organisms: Current evidence and future prospects

Antimicrobial resistance is on the rise across the globe. Increasing incidence of infections due to carbapenem resistance organisms is becoming difficult to treat, due to the limited availability of therapeutic agents. Very few agents such as colistin, fosfomycin, tigecycline and minocycline are widely used, despite its toxicity. However, with the availability of novel antimicrobials, beta-lactam/beta-lactamase inhibitor-based and non-beta-lactam-based agents could be of great relief. This review covers three important aspects which include (i) current management of carbapenem-resistant infections, (ii) determination of specific types of carbapenemases produced by multidrug-resistant and extensively drug-resistant Gram-negative pathogens and (iii) the currently available novel beta-lactam/beta-lactamase inhibitors and non-beta-lactam-based agents' laboratory findings, clinical outcome and implications.

Molecular Surveillance of Multidrug-Resistant Acinetobacter baumannii

Acinetobacter baumannii, a bacterial strain which demonstrates an elevated wide range multidrug resistance to commonly prescribed antibiotics, has been linked to recent major global outbreaks, raising a major clinical concern. Its reduced antibiotic susceptibility is closely related to the acquisition of a potent carbapenemase and/or intrinsic gene "over expression" through insertion sequences. Hence, this study aimed at investigating the antimicrobial susceptibility and molecular mechanisms underlying β-lactam resistance in A. baumannii, isolated at an academic medical centre. To understand the basis of resistance, 103 multidrug-resistant (MDR) A. baumannii isolates were collected, their antibiotic susceptibility was tested phenotypically, and then molecular analyses were performed, by testing a range of commonly encountered carbapenemases-OXA-51, OXA-23, NDM, VIM, and KPC. All strains demonstrated pan-resistance to most of the advanced antibiotics tested, including piperacillin/tazobactam, ceftazidime, cefepime, and ciprofloxacin. Moreover, majority of isolates exhibited resistance to imipenem (98.1%) and trimethoprim (90.3%). Approximately 50% of the strains showed meropenem, amikacin, and gentamycin resistance; however, lower resistance rate to tigecycline (4.9%) was noted. Moreover, isolates contained potent carbapenemases such as the intrinsic OXA-51 (89.3%), as well as the acquired resistant genes OXA-23 (68.9%), NDM (84.5%), and VIM (88.3%). The insertion sequence element ISAba1 was only detected in 35.9% of the strains. Potent resistant genes known to be carried on mobile genetic elements that aid the spread of highly resistant phenotypes were observed in a majority of isolates. These findings enforce the need for vigilant infection control measures and continuous surveillance.

XDR-Klebsiella pneumoniae isolates harboring blaOXA-48: In vitro and in vivo evaluation using a murine thigh-infection model

Blood stream infection with extensively drug-resistant-carbapenamase producing Klebsiella (K.) pneumoniae usually represents a major threat with medical challenges among hospitalized cancer patients with poor functional status and underlying diseases. Accordingly, the aim of the study was to evaluate the efficacy of different antibiotics either alone or in combinations against extensively drug-resistant-OXA-48 producing K. pneumoniae clinical isolates that were previously recovered from febrile neutropenic pediatric cancer patients. The antimicrobial activity of amikacin, gentamicin, colistin, ertapenem, imipenem, meropenem and tigecycline was assessed by broth microdilution method. The results revealed that all the tested OXA-48 producing K. pneumoniae isolates exhibited extensively drug-resistant phenotype and all of them were susceptible to tigecycline. Checkerboard method was used to determine the fraction inhibitory concentration index, to further classify the effect of antibiotic combination as synergistic, additive, indifferent, or antagonistic effect. The results revealed that in vitro dual carbapenem combination of ertapenem with meropenem had shown synergistic effect against all of the tested isolates. Additionally, synergistic effect of meropenem with colistin was detected among three of four isolates tested. Herein we investigated the in vivo activity of colistin, meropenem alone and in combination in a rat thigh infection model. The results showed that addition of meropenem to colistin was not effective at reduction of bacterial count as compared to colistin alone at 24 h post treatment. Accordingly, we can conclude that in vitro antibiotic combinations of dual carbapenems (ertapenem plus meropenem) and meropenem plus colistin showed synergism in 100% and 75% of the tested isolates, respectively. Colistin alone had significantly reduced bacterial count while its combination with meropenem was not superior to monotherapy in murine thigh infection model.

Impact statement

The present study aimed to evaluate the effectiveness of various antibiotics both in vitro and in vivo using murine animal model either alone or in combination against various strains of extensively drug-resistant (XDR) Klebsiella pneumoniae, life-threatening pathogens of relevant medical importance isolated from febrile neutropenic pediatric cancer patients. This work also emphasizes how to select the appropriate antibiotics options and help the physicians to choice the appropriate antibiotic for the treatment of such superbugs (extensively drug-resistant (XDR) Klebsiella pneumoniae). The results showed that in vitro dual carbapenem combination of ertapenem with meropenem had shown synergistic effect against all of the tested XDR isolates. Antibiotic combinations of dual carbapenems and meropenem plus colistin showed synergism in 100% and 75% of the testes isolates, respectively. Results of the in vivo evaluation, colistin alone had significantly reduced bacterial count while its combination with meropenem was not superior to monotherapy.

Effectiveness of tigecycline in the treatment of infections caused by carbapenem-resistant gram-negative bacteria in pediatric liver transplant recipients: A retrospective study

INTRODUCTION

Tigecycline (TGC) is effective for the infections caused by carbapenem-resistant gram-negative bacteria (CRGNB) in adults, but it is not investigated systematically in children because of concern about adverse effects. This study aimed to analyze the effectiveness of TGC in treating CRGNB infections in children after receiving liver transplant.

METHODS

The subjects in this retrospective study were pediatric liver transplant recipients treated with TGC for at least 3 days to fight microbiologically verified CRGNB infection after initial antibiotic failure during the period from January 2014 to May 2018. Clinical and microbiological outcomes were reviewed to evaluate the efficacy and safety of TGC.

RESULTS

Of the 1177 pediatric liver transplant recipients, 13 patients were eligible for inclusion in this analysis. All the patients received TGC at dose of 2 mg/kg every 12 hours for a duration of 10.1 ± 5.1 days on average to treat CRGNB infections, including complicated intra-abdominal infection, ventilator-associated pneumonia, and bloodstream infection. The isolates included Klebsiella pneumoniae (69.2%, 9/13) and Acinetobacter baumannii (30.8%, 4/13). Clinical efficacy was achieved in 84.6% (11/13) and pathogen eradicated in 69.2% (9/13) of the patients. The overall mortality rate was 15.4% (2/13). No TGC-related serious adverse event was reported.

CONCLUSION

Tigecycline can be considered in combination antimicrobial regimen for treating CRGNB-related infections in pediatric liver transplant recipients.

Optimizing therapy in carbapenem-resistant Enterobacteriaceae infections

PURPOSE OF REVIEW

In the absence of randomized clinical trial data, questions remain regarding the optimal treatment of carbapenem-resistant Enterobacteriaceae (CRE) infections. CRE have historically been susceptible to polymyxins, tigecycline or aminoglycosides (mostly gentamicin), and these antibiotics have long been considered the drugs of choice for CRE infections, although varying rates of resistance to all have been reported. This review looks at data from clinical studies assessing the outcomes of CRE infections treated with different antibiotic regimens.

RECENT FINDINGS

The recently approved fixed-dose combination agent, ceftazidime-avibactam (CAZ-AVI), is active against KPC and OXA-48-producing Enterobacteriaceae. The limited clinical data available on CAZ-AVI indicate that it is associated with survival benefits relative to other commonly used regimens, although development of resistance is a concern. New drugs active against CRE isolates (including the recently approved meropenem-vaborbactam) are in different stages of development.

SUMMARY

CAZ-AVI and meropenem-vaborbactam seem destined to become the backbone of target therapy for high-risk patients with severe infections caused by susceptible CRE strains. However, empirical therapy should be based on risk factors to be defined in the near future, whereas the necessity of combinations with CAZ-AVI requires further studies. Polymyxins are still important options for low-risk patients with susceptible CRE infections, but also for high-risk patients in regions where metallo-β-lactamase-producing CRE predominate because CAZ-AVI and meropenem-vaborbactam are both ineffective against these strains.

Tigecycline treatment in a liver transplant infant with carbapenem-resistant Escherichia coli infection: Case report

INTRODUCTION

During the past decade, the rate of carbapenem resistance among Enterobacteriaceae, mostly in Escherichia coli and Klebsiella pneumoniae, has significantly increased worldwide. It is a great challenge for the choice of drug treatment especially in children.Tigecycline is the first drug in the glycylcycline class of antibiotics. For children, the China Food and Drug Administration and US Food and Drug Administration postulated that tigecycline is not recommended. It must be used only as salvage therapy for life-threatening infections in critically ill children who have no alternative treatment options.

PATIENT CONCERNS

A male pediatric case of 4.5 months was blood stream infection after liver transplantation. The blood cultures obtained grew Gram-negative rods, which reportedly grew a strain of extended-spectrum β-lactamase and carbapenemases-producing Escherichia coli within 10 hours. All bacterial isolates were found to be resistant to all antimicrobial agents except aminoglycosides and tigecycline.

DIAGNOSES

Complicated intra-abdominal infection, central line-associated blood stream infection.

INTERVENTIONS

The blood stream infection with carbapenem-resistant Escherichia coli after liver transplantation was cured by tigecycline.

OUTCOMES

The patient's condition continued to improve, then transferred to general ward.

CONCLUSION

The following report, to our knowledge, is the youngest liver transplantation patient who used tigecycline treatment around the world. It provides reference and experience for the use of tigecycline in infants with severe infections.

Treatment of Infections Caused by Extended-Spectrum-Beta-Lactamase-, AmpC-, and Carbapenemase-Producing Enterobacteriaceae

Therapy of invasive infections due to multidrug-resistant Enterobacteriaceae (MDR-E) is challenging, and some of the few active drugs are not available in many countries. For extended-spectrum β-lactamase and AmpC producers, carbapenems are the drugs of choice, but alternatives are needed because the rate of carbapenem resistance is rising. Potential active drugs include classic and newer β-lactam-β-lactamase inhibitor combinations, cephamycins, temocillin, aminoglycosides, tigecycline, fosfomycin, and, rarely, fluoroquinolones or trimethoprim-sulfamethoxazole. These drugs might be considered in some specific situations. AmpC producers are resistant to cephamycins, but cefepime is an option. In the case of carbapenemase-producing Enterobacteriaceae (CPE), only some "second-line" drugs, such as polymyxins, tigecycline, aminoglycosides, and fosfomycin, may be active; double carbapenems can also be considered in specific situations. Combination therapy is associated with better outcomes for high-risk patients, such as those in septic shock or with pneumonia. Ceftazidime-avibactam was recently approved and is active against KPC and OXA-48 producers; the available experience is scarce but promising, although development of resistance is a concern. New drugs active against some CPE isolates are in different stages of development, including meropenem-vaborbactam, imipenem-relebactam, plazomicin, cefiderocol, eravacycline, and aztreonam-avibactam. Overall, therapy of MDR-E infection must be individualized according to the susceptibility profile, type, and severity of infection and the features of the patient.

Use of Next Generation Sequencing and Synergy Susceptibility Testing in Diagnosis and Treatment of Carbapenem-Resistant Klebsiella pneumoniae Blood Stream Infection

Early diagnosis and appropriate treatment for carbapenem-resistant Klebsiella pneumoniae (CR-Kp) infection is a big challenge for clinicians due to its high mortality. Every effort has been made to improve its clinical outcomes. However, treatment according to synergy susceptibility testing has never been reported in the literature. We reported a 29-year-old systemic lupus erythematosus female with CR-Kp blood stream infection. We highlighted the identification by next generation sequencing and treatment according to synergy susceptibility testing in the case.

In vitro and in vivo activity of fosfomycin alone and in combination with rifampin and tigecycline against Gram-positive cocci isolated from surgical wound infections

Complicated skin and soft tissue infections constitute a heterogeneous group of severe disorders, with surgical site infections being the most common hospital-acquired ones. The aim of our study was to investigate the synergistic and bactericidal activities of antimicrobial combinations of fosfomycin with rifampicin and tigecycline against Enterococcus faecalis, Enterococcus faecium and methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates, and also to evaluate their in vivo effects in a mouse wound infection model. In in vitro studies, the combinations of fosfomycin with rifampicin and tigecycline were both synergistic. These synergies were confirmed in in vivo studies: the drug combinations showed the highest antimicrobial effects compared to monotherapy. In conclusion, the efficacy of fosfomycin combinations, also confirmed in our in vivo model, may suggest new directions in the treatment of infected skin and a possible alternative way to control bacterial skin infection.