Tigecycline in treatment of multidrug-resistant Gram-negative bacillus urinary tract infections: a systematic review

Determination of Tigecycline in Plasma and Bronchoalveolar Lavage Fluid by UPLC-MS/MS and Its Application to a Pharmacokinetic Study in Critically Ill Patients

Tigecycline has been widely used for treating infections caused by multidrug resistant bacteria, but the dosage and intrapulmonary distribution were still controversial. In this study, a UPLC-MS/MS method was established and fully validated to quantify tigecycline in human plasma and BALF. A simple and rapid protein precipitation was used to extract the analytes from plasma and BALF samples. Then, tigecycline and IS were separated on a SHIMADZU AQ-C18 column and detected using electrospray ionization positive ion mode using the transitions of m/z 586.3 → 513.2 m/z for TGC and 458.0 → 441.0 m/z for minocycline (IS). The linearity of the calibration was in the range of 20-2000 ng/mL in plasma and BALF. The validated method was successfully applied to investigate pharmacokinetic characteristics of tigecycline in critically ill patients. The results suggested that after intravenous administration of 100-mg q12h tigecycline, the AUC0-12 was 3663.02 ± 2075.84 ng × h/mL and Css,av was 305.25 ± 172.99 ng/mL; the average plasma concentration/ELF concentration ratio was 3.66. Significant individual differences and highly variable pharmacokinetic properties were observed, indicating that adjustment of dosing regimens according to therapeutic drug monitoring is effective and efficient to guarantee the drug efficacy and safety especially for critically ill patients.

Tigecycline-Based Regimens for Complicated Urinary Tract Infections Caused by Carbapenem-Resistant Gram-Negative Bacteria: Case Series

There is existing controversy regarding the efficacy of tigecycline (TG) in treating complicated urinary tract infections (cUTIs) because of its pharmacokinetic concerns. We present three patients with cUTIs caused by carbapenem-resistant gram-negative (GN) pathogens successfully treated with high-dose tigecycline (HDT)-based regimens, as cefiderocol and aztreonam were not available in our country. The first case describes a 67-year-old patient with diabetes, prostate cancer, and double J ureteral stenting who was hospitalized with a febrile, complicated urinary tract infection (cUTI). Urine and blood cultures were positive for metallo-beta-lactamases (MBL)-producing extensively drug-resistant (XDR) Klebsiella pneumoniae (cefiderocol-susceptible). The synergy between TG and colistin using the in vitro E-test was demonstrated, and the patient was started on this regimen using HDT. Clinical and microbiological cures were achieved, and the patient was discharged home. The second case presents a 70-year-old patient with urethral pathology who was hospitalized with the diagnosis of a lower cUTI caused by an MBL-producing pan-drug-resistant (PDR) Klebsiella pneumoniae. The in vitro E-test showed synergy between TG and colistin, and our patient was successfully treated with this HDT-based combination. The third case emphasizes a 63-year-old patient with insulin-dependent diabetes, Child B cirrhosis, and a right double J ureteral stent who was hospitalized with a febrile cUTI. Urine and blood cultures were positive for carbapenem-resistant XDR Acinetobacter baumannii (susceptible to colistin and TG). Colistin was administered for only 96 hours because of stage II acute kidney injury, and we continued the treatment with HDT in monotherapy. The patient was discharged home, and no urinary tract infection relapse was seen for six months. Favorable clinical and microbiological outcomes were achieved with TG-based regimens in our cUTI cases. We highlight the role of antibiotic synergy determined by the in vitro E-test in two cases of MBL-producing XDR/PDR Klebsiella pneumoniae.

Central composite design driven optimization of sustainable stability indicating HPLC method for the determination of Tigecycline and greenness assessment

Background: Tigecycline (TGC) is a recently developed antibiotic to battle resistant bacteria. The procedures outlined in the literature for analyzing TGC involve chemical solvents that could be hazardous. Therefore, this study aimed to create a sustainable and stable HPLC technique for quantifying Tigecycline in lyophilized powder. The powerful chemometric tool, experimental design (ED), will be applied to analyze the variables' interaction and impact on the selected analytical target profiles. Response surface methodology provides a tutorial on using the central composite design with three levels of variables and quadratic programming to optimize the design space of the developed method. Methods: The New HPLC method consisted of an aqueous buffer and ethanol as a green mobile phase run on a reversed-phase symmetry C18 column. A full resolution between the Tigecycline and its degradation product peaks was achieved in a short analytical runtime. Results: Further, the specificity, accuracy, precision, robustness and stability indicating power of the proposed approach were verified through stress degrading testing. Conclusions: Finally, the analytical eco-scale and the green Analytical Procedure Index (GAPI) were utilized to determine how environmentally friendly the recommended method was compared to other published approaches.

Central composite design driven optimization of sustainable stability indicating HPLC method for the determination of Tigecycline and greenness assessment

Background: Tigecycline (TGC) is a recently developed antibiotic to battle resistant bacteria. The procedures outlined in the literature for analyzing TGC involve chemical solvents that could be hazardous. Therefore, this study aimed to create a sustainable and stable HPLC technique for quantifying Tigecycline in lyophilized powder. The powerful chemometric tool, experimental design (ED), will be applied to analyze the variables' interaction and impact on the selected analytical target profiles. Response surface methodology provides a tutorial on using the central composite design with three levels of variables and quadratic programming to optimize the design space of the developed method. Methods: The New HPLC method consisted of an aqueous buffer and ethanol as a green mobile phase run on a reversed-phase symmetry C18 column. A full resolution between the Tigecycline and its degradation product peaks was achieved in a short analytical runtime. Results: Further, the specificity, accuracy, precision, robustness and stability indicating power of the proposed approach were verified through stress degrading testing. Conclusions: Finally, the analytical eco-scale and the green Analytical Procedure Index (GAPI) were utilized to determine how environmentally friendly the recommended method was compared to other published approaches.

Current and Emerging Treatment Options for Multidrug Resistant Escherichia coli Urosepsis: A Review

Escherichia coli is a versatile commensal and pathogenic member of the human microflora. As the primary causative pathogen in urosepsis, E. coli places an immense burden on healthcare systems worldwide. To further exacerbate the issue, multi drug resistance (MDR) has spread rapidly through E. coli populations, making infections more troublesome and costlier to treat. This paper aimed to review the literature concerning the development of MDR in uropathogenic E. coli (UPEC) and explore the existing evidence of current and emerging treatment strategies. While some MDR strains maybe treated with β-lactam-β-lactamase inhibitor combinations as well as cephalosporins, cephamycin, temocillin and fosfomycin, current treatment strategies for many MDR UPEC strains are reliant on carbapenems. Carbapenem overreliance may contribute to the alarming dissemination of carbapenem-resistance amongst some UPEC communities, which has ushered in a new age of difficult to treat infections. Alternative treatment options for carbapenem resistant UPEC may include novel β-lactam-β-lactamase or carbapenemase inhibitor combinations, cefiderocol, polymyxins, tigecycline, aminoglycosides or fosfomycin. For metallo-β-lactamase producing strains (e.g., NDM, IMP-4), combinations of cefazidime-avibacam with aztreonam have been used. Additionally, the emergence of new antimicrobials brings new hope to the treatment of such infections. However, continued research is required to successfully bring these into the clinic for the treatment of MDR E. coli urosepsis.

Virulence Potential and Treatment Options of Multidrug-Resistant (MDR) Acinetobacter baumannii

Acinetobacter baumannii is an opportunistic pathogen which is undoubtedly known for a high rate of morbidity and mortality in hospital-acquired infections. A. baumannii causes life-threatening infections, including; ventilator-associated pneumonia (VAP), meningitis, bacteremia, and wound and urinary tract infections (UTI). In 2017, the World Health Organization listed A. baumannii as a priority-1 pathogen. The prevalence of A. baumannii infections and outbreaks emphasizes the direct need for the use of effective therapeutic agents for treating such infections. Available antimicrobials, such as; carbapenems, tigecycline, and colistins have insufficient effectiveness due to the appearance of multidrug-resistant strains, accentuating the need for alternative and novel therapeutic remedies. To understand and overcome this menace, the knowledge of recent discoveries on the virulence factors of A. baumannii is needed. Herein, we summarized the role of various virulence factors, including; outer membrane proteins, efflux pumps, biofilm, penicillin-binding proteins, and siderophores/iron acquisition systems. We reviewed the recent scientific literature on different A. baumannii virulence factors and the effective antimicrobial agents for the treatment and management of bacterial infections.

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.

Efficacy and safety of tigecycline for complicated urinary tract infection: a systematic review

BACKGROUND

Facing the global threat of emerging resistance to antibiotics, tigecycline, a novel glycylcycline antibiotic, is developed to against multidrug-resistant pathogens, but not recommended for the treatment of complicated urinary tract infection (cUTI). We performed a summary of the literatures to characterize and evaluate the efficacy and safety of tigecycline in patients with cUTI.

METHODS

We searched PubMed, EMBASE, Cochrane and Clinical Trials using appropriate syntax to retrieve potential articles up to Jan 2020. General information, pathogen, medication regimen, comorbidities of patients from eligible literatures were recorded. Univariate logistic regression analysis was used to detect the potential factors associated with clinical cure.

RESULTS

Nineteen articles comprising 31 cases were included. The subpopulation with transplantation (25.8% of the patients) was the most common comorbidity, and cUTIs were mainly caused by Klebsiella pneumoniae (K. pneumoniae) (48.28%) in our research. Tigecycline 100 mg per day as monotherapy was most common. Clinical cure was reported as majority (77.4%), and microbiological eradication cases accounted for the most (65.2%) among the clinical cure cases. Univariate analysis showed that K. pneumoniae caused cUTI and tigecycline as a single treatment have significant meaning to clinical outcomes (P=0.044 and P=0.034, respectively).

CONCLUSIONS

Clinical and microbiological outcomes of tigecycline treatment revealed high rate of successful response. Tigecycline monotherapy may have a role in the treatment of cUTI except that caused by the pathogen K. pneumoniae. Further randomized controlled trials was still needed to evaluate tigecycline monotherapy for cUTI.

Establishment and Validation of a Liquid Chromatography-Tandem Mass Spectrometry Method for the Determination of Tigecycline in Critically Ill Patients

Utilizing tigecycline-d9 as an internal standard (IS), we establish and validate a simple, effective, and rapid liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantitative measurement of tigecycline (TGC) in patient plasma. Acetonitrile was used as a precipitant to process plasma samples by a protein precipitation method. The analyte and IS were separated on an HSS T3 (2.1 × 100 mm, 3.5 μm) chromatographic column using isocratic program with a mobile phase comprising of 80% solvent A (water containing 0.1% formic acid (v/v) with 5 mM ammonium acetate) and 20% solvent B (acetonitrile) with a flow rate of 0.3 mL/min. The mass spectrometer, scanning in multireaction monitoring (MRM) mode and using an electrospray ion source (ESI), operated in the positive-ion mode. The ion pairs used for quantitative analysis were m/z 586.4 ⟶ 513.3 and m/z 595.5 ⟶ 514.3 for TGC and the IS, respectively. The range of the linear calibration curve obtained with this approach was 50–5000 ng/ml. Intra- and interbatch precision for TGC quantitation were less than 7.2%, and the accuracy ranged from 93.4 to 101.8%. The IS-normalized matrix effect was 87 to 104%. Due to its high precision and accuracy, this novel method allows for fast quantitation of TGC with a total analysis time of 2 min. This approach was effectively applied to study the pharmacokinetics of TGC in critically ill adult patients.

Clinico-Microbiological Investigation on Fosfomycin and Tigecycline Resistant Gram-Negative Bacilli Isolated from Urinary Tract Infections: A Potential Resurgence

Background: Traditional antibiotics are no longer as effective as before for controlling pathogens associated with urinary tract infections (UTI), which shows the necessity of developing new and more effective antibiotics. Objectives: The current study aimed to evaluate in vitro susceptibility of fosfomycin and tigecycline towards common antibiotic-resistant Gram-negative bacilli isolated from the urinary tract. Besides, clinico-microbiological on fosfomycin and tigecycline resistant Gram-negative bacilli was investigated. Methods: In this descriptive cross-sectional study, 150 resistant Gram-negative bacilli were isolated from urine specimens send for culture, and antibiotic susceptibility assessment to the Division of Microbiology of Sina Hospital affiliated to Tabriz University of Medical Sciences which were collected from April-September 2017 are included. Antibiotic susceptibilities were evaluated according to the Clinical and Laboratory Standards published by the Institute and the criteria of the Food and Drug Administration. Results: Of 150 isolates, 138 (92%) were susceptible, and 2 (1.3%) were resistant to both fosfomycin and tigecycline, as confirmed by disk diffusion and Epsilonmeter tests. The difference was statistically significant (P = 0.001). Conclusions: Based on the results, resistance to the conventional antibiotics prescribed for the treatment of UTI was significantly high. Fosfomycin and tigecycline have an appropriate antimicrobial activity towards Gram-negative-resistant isolates involved in UTIs.

Antimicrobial treatment challenges in the era of carbapenem resistance

Infections due to carbapenem-resistant Gram-negative bacteria are burdened by high mortality and represent an urgent threat to address. Clinicians are currently at a dawn of a new era in which antibiotic resistance in Gram-negative bacilli is being dealt with by the availability of the first new antibiotics in this field for many years. Although new antibiotics have shown promising results in clinical trials, there is still uncertainty over whether their use will improve clinical outcomes in real world practice. Some observational studies have reported a survival benefit in carbapenem-resistant Enterobacteriaceae bloodstream infections using combination therapy, often including "old" antibiotics such as colistin, aminoglycosides, tigecycline, and carbapenems. These regimens, however, are linked to increased risk of antimicrobial resistance, and their efficacy has yet to be compared to new antimicrobial options. While awaiting more definitive evidence, antibiotic stewards need clear direction on how to optimize the use of old and novel antibiotic options. Furthermore, carbapenem-sparing regimens should be carefully considered as a potential tool to reduce selective antimicrobial pressure.

Bacteremia by colistin-resistant Acinetobacter baumannii isolate: a case report

BACKGROUND

Carbapenem-resistant Acinetobacter baumannii infections are a major public health problem worldwide, requiring the use of "old" antibiotics such as polymyxin B and E (colistin). However, there is concern regarding the emergence of isolates resistant to these antibiotics.

CASE PRESENTATION

We report a case of a 64-year-old mestizo man hospitalized in an intensive care unit of a health institution in Colombia with identification and clinical and molecular typing of a colistin- and carbapenem-resistant A. baumannii isolate with mechanisms of resistance to colistin not previously reported, causing bacteremia.

CONCLUSIONS

We have identified a strain of A. baumannii with mechanisms of resistance to colistin not previously reported in a patient with bacteremia who required treatment with multiple antibiotic schemes and had an adequate response.

Treatment outcome of non-carbapenemase-producing carbapenem-resistant Klebsiella pneumoniae infections: a multicenter study in Taiwan

Carbapenem-resistant Klebsiella pneumoniae (CRKP) infections are associated with high mortality, and experiences with its treatment are usually based on carbapenemase-producing strains. Non-carbapenemase-producing CRKP is of clinical significance, but relevant studies are lacking. This nationwide study aimed to evaluate the outcome of antimicrobial therapy in patients with non-carbapenemase-producing CRKP infections. Patients with non-carbapenemase-producing CRKP infections were enrolled from 16 hospitals during January 2013 to December 2014 in Taiwan. Carbapenem resistance was defined as reduced susceptibility with a minimum inhibitory concentration of ≥2 mg/L for imipenem or meropenem. The resistance mechanisms of CRKP isolates were analyzed, and the clinical data of these patients were collected retrospectively. Independent risk factors of 14-day morality were determined by Cox regression analysis. A total of 99 patients with non-carbapenemase-producing CRKP infections were enrolled, and 14-day mortality was 27.3%. Among 67 patients treated with appropriate antimicrobial therapy, most (n = 61) patients received monotherapy. The 14-day mortality was lower in patients treated with appropriate monotherapy (21.3%) than in those with inappropriate therapy (37.5%). The multivariate regression model identified monotherapy (hazard ratio [HR], 0.30; 95% confidence interval [CI], 0.13-0.71; P = 0.005) as protective factor, and APACHE II scores (HR, 1.09; 95% CI, 1.01-1.18; P = 0.022) as risk factor associated with 14-day mortality. Tigecycline, colistin, and carbapenem were the most commonly used drugs in monotherapy. This study provides evidence supporting the efficacy of monotherapy in the treatment of non-carbapenemase-producing CRKP infections, and provides a future target for antibiotics stewardship for CRKP infection.

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.

An update on the management of urinary tract infections in the era of antimicrobial resistance

Urinary tract infections (UTIs) caused by antibiotic-resistant Gram-negative bacteria are a growing concern due to limited therapeutic options. Gram-negative bacteria, specifically Enterobacteriaceae, are common causes of both community-acquired and hospital acquired UTIs. These organisms can acquire genes that encode for multiple antibiotic resistance mechanisms, including extended-spectrum-lactamases (ESBLs), AmpC- β -lactamase, and carbapenemases. The assessment of suspected UTI includes identification of characteristic symptoms or signs, urinalysis, dipstick or microscopic tests, and urine culture if indicated. UTIs are categorized according to location (upper versus lower urinary tract) and severity (uncomplicated versus complicated). Increasing rates of antibiotic resistance necessitate judicious use of antibiotics through the application of antimicrobial stewardship principles. Knowledge of the common causative pathogens of UTIs including local susceptibility patterns are essential in determining appropriate empiric therapy. The recommended first-line empiric therapies for acute uncomplicated bacterial cystitis in otherwise healthy adult nonpregnant females is a 5-day course of nitrofurantion or a 3-g single dose of fosfomycin tromethamine. Second-line options include fluoroquinolones and β-lactams, such as amoxicillin-clavulanate. Current treatment options for UTIs due to AmpC- β -lactamase-producing organisms include fosfomycin, nitrofurantion, fluoroquinolones, cefepime, piperacillin-tazobactam and carbapenems. In addition, treatment options for UTIs due to ESBLs-producing Enterobacteriaceae include nitrofurantion, fosfomycin, fluoroquinolones, cefoxitin, piperacillin-tazobactam, carbapenems, ceftazidime-avibactam, ceftolozane-tazobactam, and aminoglycosides. Based on identification and susceptibility results, alternatives to carbapenems may be used to treat mild-moderate UTIs caused by ESBL-producing Enterobacteriaceae. Ceftazidime-avibactam, colistin, polymixin B, fosfomycin, aztreonam, aminoglycosides, and tigecycline are treatment options for UTIs caused by carbapenem-resistant Enterobacteriaceae (CRE). Treatment options for UTIs caused by multidrug resistant (MDR)-Pseudomonas spp. include fluoroquinolones, ceftazidime, cefepime, piperacillin-tazobactam, carbapenems, aminoglycosides, colistin, ceftazidime-avibactam, and ceftolozane-tazobactam. The use of fluoroquinolones for empiric treatment of UTIs should be restricted due to increased rates of resistance. Aminoglycosides, colistin, and tigecycline are considered alternatives in the setting of MDR Gram-negative infections in patients with limited therapeutic options.

Antibiogram of Medical Intensive Care Unit at Tertiary Care Hospital Setting of Pakistan

OBJECTIVE

 To determine the frequency of micro-organisms causing sepsis as well as to determine the antibiotic susceptibility and resistance of microorganisms isolated in a medical intensive care unit.

MATERIALS AND METHODS

 This is a cross-sectional analysis of 802 patients from a medical intensive care unit (ICU) of Shifa International Hospital, Islamabad, Pakistan over a one-year period from August 2015 to August 2016. Specimens collected were from blood, urine, endotracheal secretions, catheter tips, tissue, pus swabs, cerebrospinal fluid, ascites, bronchoalveolar lavage (BAL), and pleural fluid. All bacteria were identified by standard microbiological methods, and antibiotic sensitivity/resistance was performed using the disk diffusion technique, according to Clinical and Laboratory Standards Institute (CLSI) guidelines. Data was collected using a critical care unit electronic database and data analysis was done by using  the Statistical Package for Social Sciences (SPSS), version 20 (IBM SPSS Statistics, Armonk, NY).

RESULTS

 Gram-negative bacteria were more frequent as compared to gram-positive bacteria. Most common bacterial isolates were Acinetobacter (15.3%), Escherichia coli (15.3%), Pseudomonas aeruginosa (13%), and Klebsiella pneumoniae (10.2%), whereas Enterococcus (7%) and methicillin-resistant staphylococcus aureus (MRSA) (6.2%) were the two most common gram-positive bacteria. For Acinetobacter, colistin was the most effective antibiotic (3% resistance). For E.coli, colistin (0%), tigecycline (0%), amikacin (7%), and carbapenems (10%) showed low resistance. Pseudomonas aeruginosa showed low resistance to colistin (7%). For Klebsiella pneumoniae, low resistance was seen for tigecycline (0%) and minocycline (16%). Overall, ICU mortality was 31.3%, including miscellaneous cases.

CONCLUSION

 Gram-negative infections, especially by multidrug-resistant organisms, are on the rise in ICUs. Empirical antibiotics should be used according to the local unit specific data. Constant evaluation of current practice on basis of trends in multidrug resistance and antibiotic consumption patterns are essential.

Colistin and tigecycline resistance in carbapenemase-producing Gram-negative bacteria: emerging resistance mechanisms and detection methods

A literature review was undertaken to ascertain the molecular basis for tigecycline and colistin resistance mechanisms and the experimental basis for the detection and delineation of this resistance particularly in carbapenemase-producing Gram-negative bacteria. Pubmed, Google Scholar and Science Direct were searched with the keywords colistin, tigecycline, resistance mechanisms and detection methods. Trans-complementation and comparative MIC studies, mass spectrometry, chromatography, spectrofluorometry, PCR, qRT-PCR and whole genome sequencing (WGS) were commonly used to determine tigecycline and colistin resistance mechanisms, specifically modifications in the structural and regulatory efflux (acrAB, OqxAB, kpgABC adeABC-FGH-IJK, mexAB-XY-oprJM and soxS, rarA robA, ramRAB marRABC, adeLRS, mexRZ and nfxb) and lipid A (pmrHFIJFKLM, lpxA, lpxC lpxD and mgrB, pmrAB, phoPQ,) genes respectively. Mutations in the ribosomal 16S rRNA operon rrnBC, also yielded resistance to tigecycline through target site modifications. The mcr-1 gene conferring resistance to colistin was identified via WGS, trans-complementation and a murine thigh infection model studies. Common detection methods are mainly antibiotic sensitivity testing with broth microdilution while molecular identification tools are mostly PCR and WGS. Spectrofluorometry, MALDI-TOF MS, micro-array and real-time multiplex PCR hold much promise for the future as new detection tools.

Tigecycline antimicrobial activity tested against clinical bacteria from Latin American medical centres: results from SENTRY Antimicrobial Surveillance Program (2011-2014)

Bacterial organisms (n = 13,494) were consecutively collected in 2011-2014 from 21 Latin American medical centres (11 nations). Antimicrobial susceptibility was determined by broth microdilution at a central laboratory. Tigecycline was very active against Gram-positive organisms, with MIC50/90 values of 0.06/0.06 µg/mL for Staphylococcus aureus (n = 2878), 0.06/0.12 µg/mL for coagulase-negative staphylococci (n = 880), 0.06/0.06 µg/mL for enterococci (n = 708) and ≤0.03/≤0.03-0.06 µg/mL for streptococci (n = 1352). All Gram-positive species exhibited 100.0% susceptibility (FDA and/or EUCAST criteria), except for Streptococcus pneumoniae (99.8% susceptible). The S. aureus oxacillin resistance rate varied from 28.0% (Brazil) to 55.0% (Argentina), and the overall vancomycin resistance rate was 15.5% (Enterococcus faecium, 50.3%; and Enterococcus faecalis, 2.3%). The E. faecium vancomycin resistance rate varied from a low (26.3%) in Argentina to a high (71.7%) in Brazil. Against Enterobacteriaceae (n = 4543), tigecycline MIC50/90 values were 0.25/1 µg/mL; 98.3% and 94.2% of strains were considered susceptible according to FDA and EUCAST breakpoints, respectively. Overall, 37.7% and 57.3% of Escherichia coli and Klebsiella pneumoniae exhibited the CLSI ESBL screening phenotype. The highest CLSI ESBL screening phenotype rates among E. coli and Klebsiella spp. strains were observed for isolates collected from Mexico (69.9%) and Chile (69.9%), respectively. Occurrence of carbapenem-resistant Enterobacteriaceae was substantially higher in Brazil (9.0%) and Argentina (6.3%) compared with Chile and Mexico (0.4-0.7%). Tigecycline was also active against Acinetobacter spp. (MIC50/90, 1/2 µg/mL; 92.3/72.1% inhibited at ≤2/≤1 µg/mL) and Stenotrophomonas maltophilia (MIC50/90, 0.5/2 µg/mL; 91.5/83.0% inhibited at ≤2/≤1 µg/mL).

Treatment options for infections caused by carbapenem-resistant Enterobacteriaceae: can we apply "precision medicine" to antimicrobial chemotherapy?

INTRODUCTION

For the past three decades, carbapenems played a central role in our antibiotic armamentarium, trusted to effectively treat infections caused by drug-resistant bacteria. The utility of this class of antibiotics has been compromised by the emergence of resistance especially among Enterobacteriaceae.

AREAS COVERED

We review the current mainstays of pharmacotherapy against infections caused by carbapenem-resistant Enterobacteriaceae (CRE) including tigecycline, aminoglycosides, and rediscovered 'old' antibiotics such as fosfomycin and polymyxins, and discuss their efficacy and potential toxicity. We also summarize the contemporary clinical experience treating CRE infections with antibiotic combination therapy. Finally, we discuss ceftazidime/avibactam and imipenem/relebactam, containing a new generation of beta-lactamase inhibitors, which may offer alternatives to treat CRE infections. We critically evaluate the published literature, identify relevant clinical trials and review documents submitted to the United States Food and Drug Administration.

EXPERT OPINION

Defining the molecular mechanisms of resistance and applying insights about pharmacodynamic and pharmacokinetic properties of antibiotics, in order to maximize the impact of old and new therapeutic approaches should be the new paradigm in treating infections caused by CRE. A concerted effort is needed to carry out high-quality clinical trials that: i) establish the superiority of combination therapy vs. monotherapy; ii) confirm the role of novel beta-lactam/beta-lactamase inhibitor combinations as therapy against KPC- and OXA-48 producing Enterobacteriaceae; and, iii) evaluate new antibiotics active against CRE as they are introduced into the clinic.

Case-control study of the risk factors for acquisition of Pseudomonas and Proteus species during tigecycline therapy

Tigecycline is an important agent in clinical practice because of its broad-spectrum activity. However, it has no activity against Pseudomonas or Proteus species. We conducted a case-control study to analyze risk factors for the acquisition of Pseudomonas or Proteus spp. during tigecycline therapy. Placement of suction drainage at infected wound sites, ICU stay, and neurologic disease were identified as independent risk factors for the acquisition of Pseudomonas and Proteus spp.

Genome sequencing and genomic characterization of a tigecycline-resistant Klebsiella pneumoniae strain isolated from the bile samples of a cholangiocarcinoma patient

Background

The relationship between Klebsiella pneumoniae and nosocomial and community-acquired infections is well known, and K. pneumoniae resistance to most antibiotics is increasing worldwide. In contrast, tigecycline remains active against many bacterial strains, and serves as a last resort for treating multi-drug resistant bacterial infections. That tigecycline nonsusceptibility among K. pneumoniae isolates has been reported worldwide is worrying. However, the mechanisms of tigecycline resistance in K. pneumoniae are less well known. We report the genome sequence and genomic characterization of tigecycline-resistant K. pneumoniae strain 5422 isolated from the bile samples of a patient with cholangiocarcinoma.

Results

We sequenced the K. pneumoniae strain 5422 genome using next-generation sequencing technologies. Sequence data assembly revealed a 5,432,440-bp draft genome and 57.1% G + C content, which contained 5397 coding sequences. The genome has extensive similarity to other sequenced K. pneumoniae genomes, but also has several resistance-nodulation-cell division (RND) efflux pump genes that may be related to tigecycline resistance.

Conclusions

K. pneumoniae strain 5422 is resistant to multiple antibiotics. The genome sequence of the isolate and comparative analysis with other K. pneumoniae strains presented in this paper are important for better understanding of K. pneumoniae multi-drug resistance. The RND efflux pump genes identified in the genome indicate the presence of an antibiotic resistance mechanism prior to antibiotics overuse. The availability of the genome sequence forms the basis for further comparative analyses and studies addressing the evolution of the K. pneumoniae drug resistance mechanism and the K. pneumoniae transcriptome.

Tigecycline in treatment of multidrug-resistant Gram-negative bacillus urinary tract infections: a systematic review

OBJECTIVES

To review cases of multidrug-resistant (MDR) Gram-negative bacillus urinary tract infections (UTIs) treated with tigecycline and the literature related to this subject.

METHODS

We performed a systematic review of the literature identifying patients with MDR Gram-negative bacillus UTIs treated with tigecycline.

RESULTS

Fourteen cases describing treatment of UTIs caused by MDR Gram-negative bacilli with tigecycline are reviewed. Favourable clinical outcomes were noted in 11 of 14 cases. An initial favourable microbiological outcome was noted in 12 cases. Post-treatment cultures in two cases were positive for tigecycline-resistant organisms.

CONCLUSIONS

The clinical efficacy of tigecycline for treatment of UTIs has not been extensively evaluated. Based on the available literature, tigecycline appears to have efficacy in some patients with MDR Gram-negative bacillus UTIs. Further research in this area is needed to fully elucidate the role of tigecycline in treating such patients.