A review of tigecycline

Tigecycline in the Treatment of Ventilator-Associated Pneumonia Due to Stenotrophomonas maltophilia: A Multicenter Retrospective Cohort Study

Introduction

Tigecycline is a potential alternative to trimethoprim–sulfamethoxazole in treating Stenotrophomonas maltophilia infections due to its potent in vitro antimicrobial activity. Clinical evidence regarding the use of tigecycline in the treatment of S. maltophilia infections is scarce. In this study, we assessed the efficacy of tigecycline treating ventilator-associated pneumonia (VAP) due to S. maltophilia in comparison with fluoroquinolones.

Methods

This is a multicenter retrospective cohort study of patients admitted between January 2017 and December 2020 with the diagnosis of VAP caused by S. maltophilia receiving either tigecycline or fluoroquinolones as the definitive therapy ≥ 48 h. Clinical outcomes including 28-day mortality, clinical cure and microbiological cure were analyzed.

Results

Of 82 patients with S. maltophilia VAP included, 46 received tigecycline, and 36 received fluoroquinolones; 70.7% of patients had polymicrobial pneumonia, and the appropriate empiric therapy was applied to only 14.6% of patients. The overall 28-day mortality was 39%. Compared with patients receiving fluoroquinolones, tigecycline therapy resulted in worse clinical cure (32.6% vs. 63.9%, p = 0.009) and microbiological cure (28.6% vs. 59.1%, p = 0.045), while there was no statistical difference between 28-day mortality (47.8% vs. 27.8%, p = 0.105) in the two groups. Similar results were also shown in the inverse probability of treatment weighted univariable regression model and multivariable regression model.

Conclusions

The standard dose of tigecycline therapy was associated with a lower clinical and microbiological cure rate but not associated with an increased 28-day mortality in patients with S. maltophilia VAP compared with fluoroquinolones. Considering the unfavorable clinical outcomes, we therefore recommend against using the standard dose of tigecycline in treating S. maltophilia VAP unless new clinical evidence emerges.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40121-021-00516-5.

Riemerella anatipestifer M949_0459 gene is responsible for the bacterial resistance to tigecycline

Based on its important role in last-line therapeutics against multidrug-resistant bacteria, tigecycline has been increasingly important in treating infections. However, mounting reports on tigecycline-resistant bacterial strains isolated from different sources are of concern, and molecular mechanisms regarding tigecycline resistance are poorly understood. Riemerella anatipestifer is a Gram-negative, non-motile, non-spore-forming, rod-shaped bacterium, which causes fibrinous pericarditis, perihepatitis, and meningitis in infected ducks. We previously constructed a random transposon mutant library using Riemerella anatipestifer strain CH3, in present study, we described that Riemerella anatipestifer M949_0459 gene is responsible for the bacterial resistance to tigecycline. Using the minimum inhibitory concentration assay, a mutant strain showed significantly increased (about six-fold) tigecycline susceptibility. Subsequently, the knocked-down gene was identified as M949_0459, a putative flavin adenine dinucleotide-dependent oxidoreductase. To confirm the resistance function, M949_0459 gene was overexpressed in Escherichia coli strain BL21, and the minimum inhibitory concentration analysis showed that the gene product conferred resistance to tigecycline. Additionally, expression of the M949_0459 gene under treatment with tigecycline was measured with quantitative real-time PCR. Results showed that the mRNA expression of M949_0459 gene was elevated under tigecycline treatment with dose range of 1-10 mg/L, and peaked at 4 mg/L. Moreover, two kinds of efflux pump inhibitors, carbonyl cyanide m-chlorophenyl hydrazone and phenylalanine arginyl β-naphthylamide were tested, which showed no function on tigecycline resistance in the strain CH3. Our results may provide insights into molecular mechanisms for chemotherapy in combating Riemerella anatipestifer infections.

Fluorocyclines. 2. Optimization of the C-9 side-chain for antibacterial activity and oral efficacy

Utilizing a fully synthetic route to tetracycline analogues, the C-9 side-chain of the fluorocyclines was optimized for both antibacterial activity and oral efficacy. Compounds were identified that overcome both efflux (tet(K), tet(A)) and ribosomal protection (tet(M)) tetracycline-resistance mechanisms and are active against Gram-positive and Gram-negative organisms. A murine systemic infection model was used as an oral efficacy screen to rapidly identify compounds with oral bioavailability. Two compounds were identified that exhibit both oral bioavailability in rat and clinically relevant bacterial susceptibility profiles against major respiratory pathogens. One compound demonstrated oral efficacy in rodent lung infection models that was comparable to marketed antibacterial agents.