Prolonged and high dosage of tigecycline - successful treatment of spondylodiscitis caused by multidrug-resistant Acinetobacter baumannii: a case report

Off-label use versus formal recommendations of conventional and novel antibiotics for the treatment of infections caused by multidrug-resistant bacteria

The infections caused by multidrug- and extensively drug-resistant (MDR, XDR) bacteria, including Gram-positive cocci (GPC, including methicillin-resistant Staphylococcus aureus, MDR-Streptococcus pneumoniae and vancomycin-resistant enterococci) and Gram-negative bacilli (GNB, including carbapenem-resistant [CR] Enterobacterales, CR-Pseudomonas aeruginosa and XDR/CR-Acinetobacter baumannii complex) can be quite challenging for physicians with respect to treatment decisions. Apart from complicated urinary tract and intra-abdominal infections (cUTIs, cIAIs), bloodstream infections and pneumonia, these difficult-to-treat bacteria also cause infections at miscellaneous sites (bones, joints, native/prosthetic valves and skin structures, etc.). Antibiotics like dalbavancin, oritavancin, telavancin and daptomycin are currently approved for the treatment of acute bacterial skin and skin structural infections (ABSSSIs) caused by GPC. Additionally, ceftaroline, linezolid and tigecycline have been formally approved for the treatment of community-acquired pneumonia and ABSSSI. Cefiderocol and meropenem-vaborbactam are currently approved for the treatment of cUTIs caused by XDR-GNB. The spectra of ceftazidime-avibactam and imipenem/cilastatin-relebactam are broader than that of ceftolozane-tazobactam, but these three antibiotics are currently approved for the treatment of hospital-acquired pneumonia, cIAIs and cUTIs caused by MDR-GNB. Clinical investigations of other novel antibiotics (including cefepime-zidebactam, aztreonam-avibactam and sulbactam-durlobactam) for the treatment of various infections are ongoing. Nevertheless, evidence for adequate antibiotic regimens against osteomyelitis, arthritis and infective endocarditis due to several GPC and MDR-GNB is still mostly lacking. A comprehensive review of PubMed publications was undertaken and the formal indications and off-label use of important conventional and novel antibiotics against MDR/XDR-GPC and GNB isolates cultured from miscellaneous sites are presented in this paper.

High-Dose versus Standard-Dose Tigecycline Treatment of Secondary Bloodstream Infections Caused by Extensively Drug-Resistant Acinetobacter baumannii: An Observational Cohort Study

Background

Extensively drug-resistant Acinetobacter baumannii (XDR-AB) infections have become difficult to treat and are associated with a high mortality rate. Tigecycline is one of the most effective agents used to treat XDR-AB infections, but data from treating bloodstream infection (BSI) in standard dose do not look promising, because of its low plasma concentration. Secondary BSI with primary infection source may indicate tigecycline treatment with a higher dose. Currently, little is known about the application of high-dose tigecycline among patients with secondary BSI caused by XDR-AB. We aimed to investigate the outcomes for high-dose (HD) tigecycline treatment versus standard-dose (SD) treatment of these patients.

Methods

An observational cohort study was conducted at four university affiliated hospitals in mainland China. Adult inpatients who were confirmed as having secondary BSI caused by XDR-AB and received definitive tigecycline treatment were consecutively included. Patients who were treated with 50 mg every 12 h were defined as the SD group, and a twice dose was defined as the HD group.

Results

Of the enrolled patients, 63 received SD and 88 received HD tigecycline treatment. Patients in the two groups had similar with regard to baseline clinical conditions. The 30-day survival was affected by the source of the primary infection. Survival was significantly better in patients with non-pulmonary-infection-related BSI than in patients with pulmonary-infection-related BSI. Multivariate Cox regression confirmed that HD had a protective effect only observed in patients with non-pneumonia-related BSI.

Conclusion

A tigecycline dose that is twice its standard dose is better for the treatment of XDR-AB infection only in BSI associated with non-pulmonary infection.

[Off label uses of tigecycline]

INTRODUCTION

Tigecycline is a relatively new antibiotic that have very limited valid indications. When no other alternative is available, this drug is widely used off label with promising results. The objective of this study is to summarize the different off label uses of tigecycline so that we can decide when and how to prescribe it in the absence of guidelines.

MATERIAL AND METHODS

This study a revue of the literature collecting all the articles concerning the off label uses of tigecycline.

RESULTS

Tigecycline was widely prescribed, off label, to treat infections with controversial results. Randomised clinical trials were conducted to evaluate its use to treat pneumonia. The results for this indication have a respectable level of evidence. For the other indications, the data collected was insufficient to support tigecycline prescription. In fact, different protocols were used which makes it hard to evaluate the efficacy and to conclude to the best treatment regimen. A tendency to prescribe high doses of the molecule was noted in different studies. When prescribed off label, tigecycline prescriptions were associated with a higher mortality and incidence of side effects.

CONCLUSION

The tigecycline remains a valid option for the treatment of infections dues to multi-resistant bacteria especially when other alternatives are scarce or in cases of renal failure.

Tigecycline Versus Colistin in the Treatment of Carbapenem-resistant Acinetobacter baumannii Complex Osteomyelitis

Background: Acinetobacter baumannii complex is an increasingly important cause of osteomyelitis. It is considered a difficult to treat agent, due to increasing antimicrobial resistance and few available therapeutic options. Objective: To compare effectiveness and tolerability of tigecycline and colistin in patients with osteomyelitis caused by carbapenem-resistant A. baumannii complex (CRABC). Methods: This retrospective review included all patients admitted to a 150-bed tertiary hospital from 2007 to 2015 with microbiologically confirmed CRABC osteomyelitis for which they received tigecycline or colistin. Data on demographic and clinical characteristics, adverse events, and outcomes 12 months after the end of antimicrobial treatment were analysed and stratified according to the antimicrobial used. Results: 65 patients were included, 34 treated with colistin and 31 with tigecycline. There were significantly more men (P = 0.028) in the colistin group, and more smokers (P = 0.021) and greater occurrence of chronic osteomyelitis (P = 0.036) in the tigecycline treatment group. Median duration of therapy was 42.5 days for colistin and 42 days for tigecycline, with no significant difference. Overall incidence of adverse events was higher in the colistin group (P = 0.047). In particular, incidence of renal impairment was also higher in this group (P = 0.003). Nausea and vomiting were more frequent with tigecycline (P = 0.046). There were no significant differences between groups in relapse, amputation, or death. Conclusions: Tigecycline had a better safety profile than colistin in the treatment of osteomyelitis due to CRABC, with no significant difference in outcomes after 12 months of follow-up.

Comparison of tigecycline susceptibility testing methods for multidrug-resistant Acinetobacter baumannii

Automated systems Vitek 2, BD Phoenix, MicroScan WalkAway and gradient diffusion assays Etest and MIC Test Strip were compared against broth microdilution for susceptibility testing of tigecycline against Acinetobacter baumannii. BD Phoenix and MIC Test Strip seemed to provide the most accurate determination of tigecycline susceptibility.