Once daily high dose tigecycline - pharmacokinetic/pharmacodynamic based dosing for optimal clinical effectiveness: dosing matters, revisited

Pharmacokinetic/pharmacodynamic evaluation of tigecycline dosing in a hollow fiber infection model against clinical bla-KPC producing Klebsiella Pneumoniae isolates

The FDA announced a boxed warning for tigecycline due to progression of infections caused by Gram-negative bacteria and increased risk of mortality during treatment. Plasma exposure of tigecycline might not prevent bacteraemia in these cases from the focuses. Hence, we evaluated intensified dosing regimens and breakpoints that might suppress bloodstream infections, caused by progression of infection by e.g., Gram-negatives. A pharmacometric model was built from tigecycline concentrations (100-600 mg daily doses) against clinical Klebsiella pneumoniae isolates (MIC 0.125-0.5 mg/L). Regrowth occurred at clinically used doses and stasis was only achieved with 100 mg q8h for the strain with the lowest studied MIC of 0.125 mg/L. Stasis at 24 h was related to fAUC/MIC of 38.5. Our study indicates that even intensified dosing regimens might prevent bloodstream infections only for MIC values ≤0.125 mg/L for tigecycline. This indicates an overly optimistic breakpoint of 1 mg/L for Enterobacterales, which are deemed to respond to the tigecycline high dose regimen (EUCAST Guidance Document on Tigecycline Dosing 2022).

Intra-abdominal infection after tumor surgery: tigecycline combined with β-lactam antibiotics versus tigecycline alone

BACKGROUNDS

Tigecycline has a broad spectrum of antimicrobial activity and has been approved for the treatment of complicated intra-abdominal infections. However, it is debatable whether tigecycline should be used alone or in combination. This study aimed to investigate whether tigecycline plus β-lactam antibiotics (combination therapy [CT] group) are superior to tigecycline alone (monotherapy [MT] group) in non-critically ill intra-abdominal infection patients after tumor surgery.

METHODS

This was a multicenter, retrospective cohort study. The primary outcome was mortality during the hospital stay. Secondary outcomes were clinical success rate, microbial eradication rate, relapse rate within one week, course of treatment, and adverse effects. Propensity score matching (PSM) was used to adjust the degree of infection before medication between the MT and CT groups. Univariate comparisons were performed using the chi-squared test for qualitative variables and Student's t-test or the Mann-Whitney U-test for continuous variables, as appropriate. Multivariate logistic regression analysis was performed to examine the relationship between antimicrobial treatments and mortality during hospitalization. The paired samples Wilcoxon test was used to compare the parameters before and after medication.

RESULTS

In total, 291 patients were included in the final analysis: 128 in MT group and 163 in CT group. Mortality rate was 6.25% in the MT group and 6.13% in the CT group (P = 0.97). Multivariate logistic regression model showed that carbapenem-resistant organisms (OR: 4.35, 95% CI: 2.36 ~ 61.70) and age > 65 (OR: 1.32, 95% CI:1.19 ~ 3.01) were independent risk factors for death. CT group had a shorter defervescence time (P < 0.05), with less likelihood of relapse (P < 0.05) but had a more significant effect on activated partial thromboplastin and prothrombin time.

CONCLUSIONS

Tigecycline plus β-lactam wasn't superior to tigecycline monotherapy for the treatment of non-critically ill patients with intra-abdominal infection. But for advanced age patients with cancer, tigecycline combination therapy maybe a better choice in terms of mortality.

Risk factors of tigecycline-associated fibrinogen reduction in patients with renal transplantation: a case-control study

BACKGROUND

Hypofibrinogenemia is a serious adverse reaction related to tigecycline administered against multidrug-resistant (MDR) bacteria and can lead to therapy termination. High dose and prolonged tigecycline therapy, renal failure, and base level of fibrinogen (FIB) were reported risk factors of tigecycline-associated FIB reduction. But results are unknown in patients with renal transplantation.

METHODS

A single-center and a case-control study involving renal transplantation patients was conducted. From January, 2017 to January, 2020, patients with a tigecycline course more than 2 days and a baseline FIB level greater than 2 g/L were enrolled. Hypofibrinogenemia was defined as plasma FIB <2.0 g/L. The extent of FIB reduction was calculated based on the baseline of FIB level before tigecycline administration. FIBRO was defined as the extent of FIB reduction over 50%, and FIBRB referred to the extent of FIB reduction below 50%. Univariate and multivariate analyses were performed by logistic regression models to identify independent risk factors of tigecycline-associated FIB reduction.

RESULTS

In total, 120 patients were enrolled. A total of 114 patients (95.00%) developed with hypofibrinogenaemia. Hypofibrinogenemia mainly occurred 3 days after tigecycline administration. Of them, 79 (65.83%) developed FIBRO with a median occurrence of 3 [2-4] days after initiation of tigecycline. Multivariable regression analysis demonstrated that the FIB level before tigecycline use [odds ratio (OR): 3.225, 95% confidence interval (CI): 1.801-5.772] and total tigecycline dose (OR: 4.930, 95% CI: 1.433-16.959) were risk factors for FIBRO.

CONCLUSIONS

The FIB level before tigecycline use and total tigecycline dose were significantly associated with FIBRO, suggesting that FIB level and coagulation-related indicators should be closely monitored during tigecycline treatment to avoid life-threatening bleeding events.

Dissemination and prevalence of plasmid-mediated high-level tigecycline resistance gene tet (X4)

With the large-scale use of antibiotics, antibiotic resistant bacteria (ARB) continue to rise, and antibiotic resistance genes (ARGs) are regarded as emerging environmental pollutants. The new tetracycline-class antibiotic, tigecycline is the last resort for treating multidrug-resistant (MDR) bacteria. Plasmid-mediated horizontal transfer enables the sharing of genetic information among different bacteria. The tigecycline resistance gene tet(X) threatens the efficacy of tigecycline, and the adjacent ISCR2 or IS26 are often detected upstream and downstream of the tet(X) gene, which may play a crucial driving role in the transmission of the tet(X) gene. Since the first discovery of the plasmid-mediated high-level tigecycline resistance gene tet(X4) in China in 2019, the tet(X) genes, especially tet(X4), have been reported within various reservoirs worldwide, such as ducks, geese, migratory birds, chickens, pigs, cattle, aquatic animals, agricultural field, meat, and humans. Further, our current researches also mentioned viruses as novel environmental reservoirs of antibiotic resistance, which will probably become a focus of studying the transmission of ARGs. Overall, this article mainly aims to discuss the current status of plasmid-mediated transmission of different tet(X) genes, in particular tet(X4), as environmental pollutants, which will risk to public health for the “One Health” concept.

Analysis of the clinical characteristics of tigecycline-induced hypofibrinogenemia

Knowledge regarding the association between hypofibrinogenemia and tigecycline is based mainly on case reports. However, the clinical features of tigecycline-induced hypofibrinogenemia are unclear. We collected 20 patients (16 males and 4 females) with tigecycline-induced hypofibrinogenemia by searching the Chinese and English databases from June 2005 to May 2021, with a median age of 63.5 years (range 39∼90 years). Hypofibrinogenemia developed at a median of 9 days (range 2∼35 days). Most patients had no typical clinical manifestations, and only a few patients had bleeding and ecchymosis. Fibrinogen levels gradually decreased from 3.98 ± 2.05 g/L to 0.87 ± 0.45 g/L (P = 0.000), and the activated partial thromboplastin time (APTT) increased from 38.26 ± 8.80 s to 83.43 ± 47.23 s (P = 0.002). Fibrinogen levels in all patients recovered to the normal range within a median of 4 days (range 1∼12 days) after tigecycline cessation. Our results suggest that fibrinogen levels should be closely monitored in patients treated with tigecycline, specifically patients who may have renal insufficiency or patients with long-term use.

Machine perfusion combined with antibiotics prevents donor-derived infections caused by multidrug-resistant bacteria

Donor infection affects organ utilization, especially the infections by multidrug-resistant bacteria, which may have disastrous outcomes. We established a rat model, inoculated with Escherichia coli or carbapenem-resistant Klebsiella pneumoniae (CRKP), to investigate whether hypothermic machine perfusion (HMP), normothermic machine perfusion (NMP), or static cold storage (SCS) combined with antibiotic (AB) could eliminate the bacteria. E. coli or CRKP-infected kidneys were treated with cefoperazone-sulbactam and tigecycline, respectively. The HMP+AB and NMP+AB treatments had significant therapeutic effects on E. coli or CRKP infection compared with the SCS+AB treatment. The bacterial load of CRKP-infected kidneys in the HMP+AB (22 050 ± 2884 CFU/g vs. 1900 ± 400 CFU/g, p = .007) and NMP+AB groups (25 433 ± 2059 CFU/g vs. 500 ± 458 CFU/g, p = .002) were significantly reduced, with no statistically significant difference between both groups. Subsequently, the CRKP-infected kidneys of the HMP+AB and SCS+AB groups were transplanted. The rats in the SCS+AB group were severe infected and euthanized on day 4 post-transplant. By contrast, the rats in the HMP+AB group were in good condition. In conclusion, HMP and NMP combined with AB seems to be efficient approaches to decrease bacterial load of infected kidneys. This might lead to higher utilization rates of donors with active infection.

Tigecycline and Gentamicin-Combined Treatment Enhances Renal Damage: Oxidative Stress, Inflammatory Reaction, and Apoptosis Interplay

Although the combination of antibiotics is generally well-tolerated, they may have nephrotoxic effects. This study investigated whether tigecycline (TG) and gentamicin (GM) co-administration could accelerate renal damage. Male Wistar rats were randomly divided into six experimental groups: the control, TG7 (tigecycline, 7 mg/kg), TG14 (tigecycline, 14 mg/kg), GM (gentamicin, 80 mg/kg), TG7+GM, and TG14+GM groups. The combination of TG and GM evoked renal damage seen by the disruption of kidney function tests. The perturbation of renal tissue was mainly confounded to the TG and GM-induced oxidative damage, which was exhibited by marked increases in renal MDA (malondialdehyde) along with a drastic reduction in GSH (reduced-glutathione) content and CAT (catalase) activity compared to their individual treatments. More obvious apoptotic events and inflammation were also revealed by elevating the annexin-V and interleukin-6 (IL-6) levels, aside from the upregulation of renal PCNA (proliferating cell nuclear antigen) expression in the TG and GM concurrent treatment. The principal component analysis indicated that creatinine, urea, annexin-V, IL-6, and MDA all played a role in discriminating the TG and GM combined toxicity. Oxidative stress, inflammatory response, and apoptosis were the key mechanisms involved in this potentiated toxicity.

Virulence factors of Proteus mirabilis clinical isolates carrying blaKPC-2 and blaNDM-1 and first report blaOXA-10 in Brazil

INTRODUCTION

Proteus mirabilis is one of the main pathogens that cause urinary tract infections. Therefore, the aim of this study was to analyze and compare the genetic profile of 36 clinical isolates of P. mirabilis that carry and do not carry the bla_KPC and bla_NDM gene with respect to virulence factors (mrpG, pmfA, ucaA, nrpG and pbtA) and antimicrobial resistance (bla_VIM,bla_IMP, bla_SPM, bla_GES,bla_OXA-23-like, bla_OXA-48-like, bla_OXA-58-like and bla_OXA-10-like).

METHODS

The virulence and resistance genes were investigated by using PCR and sequencing.

RESULTS

ERIC-PCR typing showed that the isolates showed multiclonal dissemination and high genetic variability. The gene that was most found bla_OXA-10-like (n = 18), followed by bla_KPC (n = 10) and bla_NDM (n = 8). To our knowledge, this is the first report of bla_OXA-10 in P. mirabilis in Brazil, as well as the first report of the occurrence of P. mirabilis co-carrying bla_OXA-10/bla_KPC and bla_OXA-10/bla_NDM. The bla_NDM or bla_KPC carrier isolates showed important virulence genes, such as ucaA (n = 8/44.4%), pbtA (n = 10/55.5%) and nrpG (n = 2/11.1%). However, in general, the non-carrier isolates of bla_KPC and bla_NDM showed a greater number of virulence genes when compared to the carrier group.

CONCLUSION

Clinical isolates of P. mirabilis, in addition to being multi-drug resistant, presented efficient virulence factors that can establish infection outside the gastrointestinal tract.

Tigecycline Heteroresistance and Resistance Mechanism in Clinical Isolates of Acinetobacter baumannii

Tigecycline is regarded as a last-resort treatment for multidrug-resistant Acinetobacter baumannii. However, tigecycline resistance in A. baumannii has increased worldwide. In this study, we investigated tigecycline heteroresistance in A. baumannii isolates from South Korea. Antibiotic susceptibility testing was performed on 323 nonduplicated A. baumannii isolates. Among 260 and 37 tigecycline-susceptible and -intermediate-resistant A. baumannii isolates, 146 (56.2%) and 22 (59.5%) isolates were identified as heteroresistant to tigecycline through a disk diffusion assay and population analysis profiling. For selected isolates, an in vitro time-kill assay was performed, and survival rates were measured after preincubation with diverse concentrations of tigecycline. Heteroresistant isolates showed regrowth after 12 h of 2× MIC of tigecycline treatment, and resistant subpopulations were selected by preexposure to tigecycline. Furthermore, genetic alterations in adeABC, adeRS, and rpsJ were assessed, and the relative mRNA expression levels of adeB and adeS were compared. The tigecycline resistance in subpopulations might be due to the insertion of ISAba1 in adeS, leading to the overexpression of the AdeABC efflux pump. However, the tigecycline resistance of subpopulations was not stable during serial passages in antibiotic-free medium. The reversion of tigecycline susceptibility by antibiotic-free passages might occur by additional insertions of ISAba10 in adeR and nucleotide alterations in adeS in some mutants. Tigecycline heteroresistance is prevalent in A. baumannii isolates, which results in treatment failure. Tigecycline resistance is mainly due to the overexpression of the AdeABC efflux pump, which is associated with genetic mutations, but this resistance could be reversed into susceptibility by additional mutations in antibiotic-free environments. IMPORTANCE The evidence that antibiotic heteroresistance is responsible for treatment failure in clinical settings is increasing. Thus, detection and characterization of heteroresistance would be important for appropriate therapeutic guidance to treat bacterial infections. However, data on tigecycline heteroresistance in Gram-negative bacteria is currently limited, although tigecycline is regarded as a last-line antibiotic against infections caused by antibiotic-resistant pathogens. In this study, we investigated the tigecycline heteroresistance in Acinetobacter baumannii, which has been listed by the WHO as a priority for research and development of new antibiotics. We found very high prevalence of tigecycline-heteroresistant A. baumannii clinical isolates, which may result in treatment failure due to the selection of resistant subpopulations. We also identified the main resistance mechanism in tigecycline-resistant subpopulations, that is, upregulation of AdeABC efflux pumps due to ISAba1 insertion in adeS.

The Synergistic Activity and Optimizing Doses of Tigecycline in Combination with Aminoglycosides against Clinical Carbapenem-Resistant Klebsiella pneumoniae Isolates

Carbapenem-resistant Enterobacteriaceae (CRE), especially carbapenem-resistant Klebsiella pneumoniae (CRKP), are among the largest pathogenic threats to humans. The available antibiotic treatment options for combating CRKP are limited. Colistin-resistant Enterobacteriaceae (CoRE) have also been reported worldwide, including in Thailand. Therefore, this study aimed (1) to determine minimum inhibitory concentrations (MICs) and synergistic activities of antibiotics of CRKP, and (2) to determine the probability target of attainment (PTA) and cumulative fraction of response (CFR) using pharmacokinetic/pharmacodynamic (PK/PD) data. Clinical CRKP isolates were obtained from Phramongkutklao Hospital (June to November 2020). Broth microdilution and checkerboard techniques were used to determine the mono- and synergistic activities of antibiotics. Carbapenemase and mcr-1 genes were also identified by polymerase chain reaction (PCR). The optimal antibiotic regimens were evaluated using Monte Carlo simulations. Forty-nine CRKP isolates were collected, 40 of which were CoRKP strains. The MIC50 and MIC90 of tigecycline, amikacin, and gentamicin were 1 and 2 µg/mL, 4 and 16 µg/mL, and 0.25 and 4 µg/mL, respectively. None of any isolates expressed the mcr-1 gene, whereas bla_OXA-48 (53.1%) and bla_OXA-48 plus bla_NDM (42.9%) were detected. Synergistic activity was observed in 8.2% of isolates for tigecycline combined with amikacin or gentamicin. Additive activity was observed in 75.5% of isolates for tigecycline-amikacin and 69.4% for tigecycline-gentamicin, and no antagonism was observed. High-dose antibiotic regimens achieved the PTA target. The general recommended dose of combination regimens began with 200 mg tigecycline and 25 mg/kg amikacin, or 7 mg/kg gentamicin, followed by 100 mg tigecycline every 12 h and 15 mg/kg amikacin or 5 mg/kg gentamicin every 24 h. In conclusion, tigecycline plus aminoglycosides might be a potential regimen against CRKP and CoRKP. The appropriate combination regimen based on MIC-based dose adjustment can improve optimal antibiotic dosing. Further research via clinical studies will be necessary to confirm these results.

First report of bla GES-1 in Proteus mirabilis clinical isolates

Proteus mirabilis is one of the main pathogens causing urinary tract infections and sepsis. To our knowledge, this is the first report of a P. mirabilis hosting bla_GES. The presence of these genes was determined using PCR and sequencing. We identified the presence of bla_GES-1 in all three isolates. In addition, we identified the bla_KPC-2 and bla_NDM-1 genes in the two strains. These data emphasize the importance of monitoring and surveillance of all enterobacteria. The circulation of P. mirabilis strains carrying bla_GES-1 constitutes a new scenario of resistance in this species and should be an epidemiological alert for global health.

Longitudinal Study of the Drug Resistance in Klebsiella pneumoniae of a Tertiary Hospital, China: Phenotypic Epidemiology Analysis (2013-2018)

Purpose

Multi-drug resistant Klebsiella pneumoniae (MDR KP) is spreading worldwide and has posed a huge medical burden to public health. However, studies on drug resistance surveillance of KP, especially MDR KP, with a large longitudinal sample size in a tertiary hospital are rare. This study aims to investigate phenotypic epidemiology characteristics of 4128 KP isolates in a Chinese tertiary hospital covering a period of 5 years.

Methods

All the KP clinical isolates were retrospectively collected from a tertiary hospital in Hunan province of China from Jan 5, 2013 to Jul 24, 2018. All the isolates were identified by MALDI-TOF MS analysis. Twenty-four antimicrobial agents were tested by antimicrobial susceptibility testing. Fisher exact test and logistic regression were used to analyze the association between clinical factors and antimicrobial non-susceptibility for seven second-choice antimicrobials.

Results

A total of 4128 KP isolates were collected in our study. The non-susceptible rates (NSRs) to ertapenem, imipenem and tigecycline increased considerably from 2013 to 2018 (13.6% to 28.6%, 10.1% to 28.9%, 10.8% to 46.5%, respectively). Amikacin presents the lowest NSR among 3 aminoglycosides (3.8–22.8%). The multi-drug NSRs among KP isolates to second-choice antimicrobials (88.6–100%) were higher than to all drugs (68.0%). The NSRs varied significantly among departments and sample sources. Higher ETP/IPM/AK NSRs (39.8/39.7/30.6%) were observed in Intensive Care Unit, and ETP/IPM non-susceptible isolates tended to distribute in cerebrospinal fluid. From 2015 to 2017, the NSRs of ETP, IPM, and AK showed an opposite trend of seasonal fluctuations to SXT.

Conclusion

Higher multi-drug resistance (MDR) rates were observed in KP isolates to second-choice antimicrobials than to others, among which MDR rates to carbapenems or AK are the highest. A unique pattern of MIC and time distributions of MDR were observed. Clinical factors including gender were correlated with MDR rates of KP. Isolates in ICU and CSF showed higher NSRs in carbapenems which should be paid more attention to, and temporal distribution of NSRs was observed.

Hypofibrinogenemia induced by high-dose tigecycline-case report and review of literature

RATIONALE

Extensive off-label use may affect the safety profile of tigecycline. Tigecycline-associated hypofibrinogenemia is potentially life threatening, although the frequency of life-threatening reactions is unknown and their incidence is easily overlooked. We report a case of 2 instances of treatment with high-dose tigecycline, each of which presented with hypofibrinogenemia.

PATIENT CONCERNS

An 86-year-old male patient was treated twice with high-dose tigecycline and presented with hypofibrinogenemia both times. The decrease in fibrinogen occurred within 3 to 7 days of tigecycline treatment. Other coagulation parameters had slightly prolonged values.

DIAGNOSES

Coagulopathy and hypofibrinogenemia.

INTERVENTIONS

We discontinued the tigecycline.

OUTCOMES

The fibrinogen level normalized within 5 days after the withdrawal of tigecycline. Following 80 days of hospitalization, the patient was transferred to the rehabilitation hospital for further treatment.

LESSONS

We suggest routine strict monitoring of coagulation parameters, particularly fibrinogen. Attention should be paid to below-normal fibrinogen levels due to increased bleeding risk and severity of reaction at fibrinogen levels below 1 g/L.

Is it time to move away from polymyxins?: evidence and alternatives

Increasing burden of carbapenem resistance and resultant difficult-to-treat infections are of particular concern due to the lack of effective and safe treatment options. More recently, several new agents with activity against certain multidrug-resistant (MDR) and extensive drug-resistant (XDR) Gram-negative pathogens have been approved for clinical use. These include ceftazidime-avibactam, meropenem-vaborbactam, imipenem-cilastatin-relebactam, plazomicin, and cefiderocol. For the management of MBL infections, clinically used triple combination comprising ceftazidime-avibactam and aztreonam is hindered due to non-availability of antimicrobial susceptibility testing methods and lack of information on potential drug-drug interaction leading to PK changes impacting its safety and efficacy. Moreover, in several countries including Indian subcontinent and developing countries, these new agents are yet to be made available. Under these circumstances, polymyxins are the only last resort for the treatment of carbapenem-resistant infections. With the recent evidence of suboptimal PK/PD particularly in lung environment, limited efficacy and increased nephrotoxicity associated with polymyxin use, the Clinical and Laboratory Standards Institute (CLSI) has revised both colistin and polymyxin B breakpoints. Thus, polymyxins 'intermediate' breakpoint for Enterobacterales, P. aeruginosa, and Acinetobacter spp. are now set at ≤ 2 mg/L, implying limited clinical efficacy even for isolates with the MIC value 2 mg/L. This change has questioned the dependency on polymyxins in treating XDR infections. In this context, recently approved cefiderocol and phase 3 stage combination drug cefepime-zidebactam assume greater significance due to their potential to act as polymyxin-supplanting therapies.

Pharmacokinetics of tigecycline in critically ill patients with liver failure defined by maximal liver function capacity test (LiMAx)

BACKGROUND

In critically ill patients, tigecycline (TGC) remains an important therapeutic option due to its efficacy against multiresistant Gram-positive and Gram-negative bacteria. TGC is metabolized and eliminated predominantly by the liver. Critical illness-induced liver failure may have a profound impact on the pharmacokinetic of TGC. In the present study, we aimed to establish a link between the degree of liver dysfunction and TGC plasma concentration using the novel maximum liver function capacity (LiMAx) test, as a dynamic liver function test.

MATERIALS/METHODS

The prospective study included 33 patients from a surgical ICU with the clinical indication for antibiotic therapy with TGC. The patients received 100 mg loading dose of TGC followed by intermittent standard doses of 50 mg q12. Blood samples for TGC plasma concentration were collected at 0.3, 2, 5, 8 and 11.5 h in a steady-state condition after at least 36 h post-standard dosage. The results were analyzed by means of a high-performance liquid chromatography (HPLC) method. Within the same day, the LiMAx test was carried out and routine blood parameters were measured.

RESULTS

Peak plasma concentrations of TGC were significantly higher in patients with severe liver failure (LiMAx < 100 µg/kg/h) when compared to patients with normal liver function (LiMAx > 300 µg/kg/h). The pharmacokinetic curves revealed higher values in severe liver failure at any measured point. Moreover, LiMAx and total bilirubin were the only liver-related parameters that correlated with TGC C_max.

CONCLUSIONS

The present study demonstrates a high variability of TGC plasma concentrations in critically ill patients. The results show a significant correlation between the degree of liver dysfunction, measured by the LiMAx test, and TGC C_max. LiMAx test may be a helpful tool beyond others for adjusting the required dosage of hepatic metabolized antibiotics in critically ill patients. Trial registry DRKS-German clinical trials register; Trial registration number: DRKS00008888; Date of registration: 07-17-2015; Date of enrolment of the first participant to the trial: 12-10-2015.

Pharmacokinetics of high-dose tigecycline in critically ill patients with severe infections

Background

In critically ill patients, the use of high tigecycline dosages (HD TGC) (200 mg/day) has been recently increasing but few pharmacokinetic/pharmacodynamic (PK/PD) data are available. We designed a prospective observational study to describe the pharmacokinetic/pharmacodynamic (PK/PD) profile of HD TGC in a cohort of critically ill patients with severe infections.

Results

This was a single centre, prospective, observational study that was conducted in the 20-bed mixed ICU of a 1500-bed teaching hospital in Rome, Italy. In all patients admitted to the ICU between 2015 and 2018, who received TGC (200 mg loading dose, then 100 mg q12) for the treatment of documented infections, serial blood samples were collected to measure steady-state TGC concentrations. Moreover, epithelial lining fluid (ELF) concentrations were determined in patients with nosocomial pneumonia. Amongst the 32 non-obese patients included, 11 had a treatment failure, whilst the other 21 subjects successfully eradicated the infection. There were no between-group differences in terms of demographic aspects and main comorbidities. In nosocomial pneumonia, for a target AUC_0-24/MIC of 4.5, 75% of the patients would be successfully treated in presence of 0.5 mcg/mL MIC value and all the patients obtained the PK target with MIC ≤ 0.12 mcg/mL. In intra-abdominal infections (IAI), for a target AUC_0-24/MIC of 6.96, at least 50% of the patients would be adequately treated against bacteria with MIC ≤ 0.5 mcg/mL. Finally, in skin and soft-tissue infections (SSTI), for a target AUC_0-24/MIC of 17.9 only 25% of the patients obtained the PK target at MIC values of 0.5 mcg/mL and less than 10% were adequately treated against germs with MIC value ≥ 1 mcg/mL. HD TGC showed a relevant pulmonary penetration with a median and IQR ELF/plasma ratio (%) of 152.9 [73.5–386.8].

Conclusions

The use of HD TGC is associated with satisfactory plasmatic and pulmonary concentrations for the treatment of severe infections due to fully susceptible bacteria (MIC < 0.5 mcg/mL). Even higher dosages and combination strategies may be suggested in presence of difficult to treat pathogens, especially in case of SSTI and IAI.

Analysis of clinical characteristics of tigecycline-induced acute pancreatitis

WHAT IS KNOWN AND OBJECTIVE

The purpose of this study is to explore the clinical characteristics of tigecycline-induced acute pancreatitis.

METHODS

We searched the PubMed/Medline, Web of Knowledge, OVID, Elsevier, Springer Link, Embase, Cochrane Library, China National Knowledge Infrastructure (CNKI), Wanfang Data, and Chinese VIP databases from 2005 and identified 19 studies of tigecycline-induced acute pancreatitis involving a total of 22 patients for inclusion in a retrospective analysis.

RESULTS AND DISCUSSION

The median (range) age of 22 patients with acute pancreatitis was 58 years (range 9-83). Overall, the median (range) time of symptom onset was 6.5 days (range 2-28), or 6 days (range 2-14) and 6 days (range 3-28) in patients with or without a loading dose of tigecycline, respectively. Symptoms included nausea, vomiting and abdominal distension (73%) and abdominal pain (73%); 90% (18/20) of patients developed mild acute pancreatitis (MAP), and 10% (2/20) developed severe acute pancreatitis (SAP). Computed tomography (CT) scans showed oedematous infiltrate in 56% (10/18) of cases and acute pancreatitis in 28% (5/18) of cases. The median (range) level of lipase and amylase was 936U/L (range 382-4089) and 588U/L (range 312-1166), respectively. The median (range) time to recovery of symptoms was 4 days (range 1-10), and the time for recovery of pancreatic enzymes to the normal range was 5 days (range 1-30) after the withdrawal of tigecycline in all patients.

WHAT IS NEW AND CONCLUSION

Clinicians should be particularly mindful of clinical signs and symptoms, the level of serum pancreatic enzymes and abdominal CT images in order to monitor the development of pancreatitis when using tigecycline.

Uso compasional de tigeciclina intraventricular en pacientes con ventriculitis causada por Enterococcus faecium. Reporte de seis casos pediátricos

Introducción: La Tigeciclina es un fármaco de uso restringido en pediatría. El uso de este antibiótico por vía intraventricular es una decisión de uso compasivo en casos de bacterias altamente resistentes, y para los casos en que no exista otra alternativa. Caso clínico: Se presenta seis casos de pacientes con diagnóstico de ventriculitis a Enterococcus faecium que recibieron tigeciclina intraventricular con evolución bacteriológica exitosa. Se discute las dosis utilizadas por vía endovenosa e intraventricular. Conclusiones: el uso de este antibiótico por vía intraventricular puede ser una alternativa exitosa en casos de gérmenes altamente resistentes y cuando no exista otra alternativa terapéutica.

Successful High-Dosage Monotherapy of Tigecycline in a Multidrug-Resistant Klebsiella pneumoniae Pneumonia-Septicemia Model in Rats

Background: Recent scientific reports on the use of high dose tigecycline monotherapy as a “drug of last resort” warrant further research into the use of this regimen for the treatment of severe multidrug-resistant, Gram-negative bacterial infections. In the current study, the therapeutic efficacy of tigecycline monotherapy was investigated and compared to meropenem monotherapy in a newly developed rat model of fatal lobar pneumonia–septicemia. Methods: A Klebsiella pneumoniae producing extended-spectrum β-lactamase (ESBL) and an isogenic variant producing K. pneumoniae carbapenemase (KPC) were used in the study. Both strains were tested for their in vitro antibiotic susceptibility and used to induce pneumonia–septicemia in rats, which was characterized using disease progression parameters. Therapy with tigecycline or meropenem was initiated at the moment that rats suffered from progressive infection and was administered 12-hourly over 10 days. The pharmacokinetics of meropenem were determined in infected rats. Results: In rats with ESBL pneumonia–septicemia, the minimum dosage of meropenem achieving survival of all rats was 25 mg/kg/day. However, in rats with KPC pneumonia–septicemia, this meropenem dosage was unsuccessful. In contrast, all rats with KPC pneumonia–septicemia were successfully cured by administration of high-dose tigecycline monotherapy of 25 mg/kg/day (i.e., the minimum tigecycline dosage achieving 100% survival of rats with ESBL pneumonia–septicemia in a previous study). Conclusions: The current study supports recent literature recommending high-dose tigecycline as a last resort regimen for the treatment of severe multidrug-resistant bacterial infections. The use of ESBL- and KPC-producing K. pneumoniae strains in the current rat model of pneumonia–septicemia enables further investigation, helping provide supporting data for follow-up clinical trials in patients suffering from severe multidrug-resistant bacterial respiratory infections.

Eravacycline for the treatment of complicated intra-abdominal infections

Introduction: Complicated intra-abdominal infections (cIAIs) are among the most frequent infections, contributing to significant morbidity and healthcare costs. Several medical needs remain unmet, related to the pharmacokinetic capacities of the available drugs and their limited spectrum of activity for targeting multidrug-resistant Gram-negative and Gram-positive bacteria. Eravacycline, a new synthetic fluorocycline, could have useful properties in cIAIs.Areas covered: The antimicrobial activity of eravacycline against the microorganisms most frequently cultured in cIAIs has been confirmed in worldwide panels of clinical isolates, including enterococci, ESBL-producing Enterobacteriaceae, Acinetobacter baumannii and anaerobes. Pharmacokinetic data demonstrate interesting characteristics with good tissue concentrations including biliary tract and digestive tissues. At a conventional dosage of 1 mg/kg q12h, no adjustment is required on the basis of race or gender, or in elderly (≥ 65 years old) patients, patients with renal impairment or patients undergoing hemodialysis. Phase 2 and 3 trials assessing the clinical efficacy and safety of eravacycline demonstrated non-inferiority versus carbapenems and a good safety profile.Expert opinion: Eravacycline may be particularly suitable for the treatment of cIAIs. Results from clinical trials and real-world data are now expected in specific subgroups of patients to confirm the safety profile and efficacy observed in registration trials.

Efficacy and safety of high-dose tigecycline for the treatment of infectious diseases: A meta-analysis

BACKGROUND

High-dose (HD) tigecycline regimen is increasingly used in infectious diseases, however its efficacy and safety versus low-dose (LD) is still unclear.

METHODS

A systematic review and meta-analysis was performed; PubMed, Embase, Cochrane Library, ScienceDirect, Web of Science, clinicalTrials.gov, Wanfang, VIP, and China National Knowledge Infrastructure (CNKI), were searched using terms "tigecycline" AND "dose" up to October 31, 2018. Eligible studies were randomized trials or cohort studies comparing mortality, clinical response, microbiological eradication and safety of different tigecycline dose regimens for any bacterial infection. The primary outcome was mortality, and the secondary outcomes were clinical response rate, microbiological eradiation rate and adverse events (AEs). Meta-analysis was done with random-effects model, with risk ratios (RR) and 95% confidence intervals (CI) calculated for all outcomes.

RESULTS

Of 951 publications retrieved, 17 studies (n = 1041) were pooled in our meta-analysis. The primary outcome was available in 11 studies, and the RR for mortality was 0.67 (95% CI 0.53-0.84, P < .001). Clinical response (RR 1.46, 95% CI 1.30-1.65, P < .001) and microbiological eradication rate (RR 1.61, 95% CI 1.35-1.93, P < .001) were both higher in HD than in LD tigecycline regimen. However, non-Chinese study subgroup presented no statistical significance between HD and LD regimen, RR for mortality, clinical response and microbiological eradication were 0.79 (95% CI 0.56-1.14, P = .21), 1.35 (95% CI 0.96-1.92, P = .26), 1.00 (95% CI 0.22-4.43, P = 1.00), respectively. AEs did not differ between HD and LD tigecycline (RR 1.00, 95% CI 0.80-1.26, P = .97).

CONCLUSION

HD tigecycline regimen reduced mortality meanwhile improved clinical efficacy and should be considered in serious infections caused by multidrug-resistant and extensively drug-resistant (MDR/XDR) bacteria.

Biological Functions and Molecular Mechanisms of Antibiotic Tigecycline in the Treatment of Cancers

As an FDA-approved drug, glycylcycline tigecycline has been used to treat complicated microbial infections. However, recent studies in multiple hematologic and malignant solid tumors reveal that tigecycline treatment induces cell cycle arrest, apoptosis, autophagy and oxidative stress. In addition, tigecycline also inhibits mitochondrial oxidative phosphorylation, cell proliferation, migration, invasion and angiogenesis. Importantly, combinations of tigecycline with chemotherapeutic or targeted drugs such as venetoclax, doxorubicin, vincristine, paclitaxel, cisplatin, and imatinib, have shown to be promising strategies for cancer treatment. Mechanism of action studies reveal that tigecycline leads to the inhibition of mitochondrial translation possibly through interacting with mitochondrial ribosome. Meanwhile, this drug also interferes with several other cell pathways/targets including MYC, HIFs, PI3K/AKT or AMPK-mediated mTOR, cytoplasmic p21 ^CIP1/Waf1, and Wnt/β-catenin signaling. These evidences indicate that antibiotic tigecycline is a promising drug for cancer treatment alone or in combination with other anticancer drugs. This review summarizes the biological function of tigecycline in the treatment of tumors and comprehensively discusses its mode of action.

Molecular basis for the emergence of a new hospital endemic tigecycline-resistant Enterococcus faecalis ST103 lineage

Enterococcus faecalis are a major cause of nosocomial infection worldwide, and the spread of vancomycin resistant strains (VRE) limits treatment options. Tigecycline-resistant VRE began to be isolated from inpatients at a Brazilian hospital within months following the addition of tigecycline to the hospital formulary. This was found to be the result of a spread of an ST103 E. faecalis clone. Our objective was to identify the basis for tigecycline resistance in this lineage. The genomes of two closely related tigecycline-susceptible (MIC = 0.06 mg/L), and three representative tigecycline-resistant (MIC = 1 mg/L) ST103 isolates were sequenced and compared. Further, efforts were undertaken to recapitulate the emergence of resistant strains in vitro. The specific mutations identified in clinical isolates in several cases were within the same genes identified in laboratory-evolved strains. The contribution of various polymorphisms to the resistance phenotype was assessed by trans-complementation of the wild type or mutant alleles, by testing for differences in mRNA abundance, and/or by examining the phenotype of transposon insertion mutants. Among tigecycline-resistant clinical isolates, five genes contained non-synonymous mutations, including two genes known to be related to enterococcal tigecycline resistance (tetM and rpsJ). Finally, within the in vitro-selected resistant variants, mutation in the gene for a MarR-family response regulator was associated with tigecycline resistance. This study shows that E. faecalis mutates to attain tigecycline resistance through the complex interplay of multiple mechanisms, along multiple evolutionary trajectories.

Therapies for multidrug resistant and extensively drug-resistant non-fermenting gram-negative bacteria causing nosocomial infections: a perilous journey toward 'molecularly targeted' therapy

INTRODUCTION

Non-fermenting Gram-negative bacilli are at the center of the antimicrobial resistance epidemic. Acinetobacter baumannii and Pseudomonas aeruginosa are both designated with a threat level to human health of 'serious' by the Centers for Disease Control and Prevention. Two other major non-fermenting Gram-negative bacilli, Stenotrophomonas maltophilia and Burkholderia cepacia complex, while not as prevalent, have devastating effects on vulnerable populations, such as those with cystic fibrosis, as well as immunosuppressed or hospitalized patients. Areas covered: In this review, we summarize the clinical impact, presentations, and mechanisms of resistance of these four major groups of non-fermenting Gram-negative bacilli. We also describe available and promising novel therapeutic options and strategies, particularly combination antibiotic strategies, with a focus on multidrug resistant variants. Expert commentary: We finally advocate for a therapeutic approach that incorporates in vitro antibiotic susceptibility testing with molecular and genotypic characterization of mechanisms of resistance, as well as pharmacokinetics and pharmacodynamics (PK/PD) parameters. The goal is to begin to formulate a precision medicine approach to antimicrobial therapy: a clinical-decision making model that integrates bacterial phenotype, genotype and patient's PK/PD to arrive at rationally-optimized combination antibiotic chemotherapy regimens tailored to individual clinical scenarios.

Dissemination of Multidrug-Resistant Proteus mirabilis Clones Carrying a Novel Integron-Borne blaIMP-1 in a Tertiary Hospital

This study aimed to characterize multidrug-resistant Proteus mirabilis clones carrying a novel class 1 integron-borne bla_IMP-1 In1359 was inserted into a large conjugative plasmid that also carried bla_CTX-M-2 The production of carbapenemases in Enterobacteriaceae that are intrinsically resistant to polymyxins and tigecycline is very worrisome, representing a serious challenge to clinicians and infection control teams.