Assessment of the Activity of Tigecycline against Gram-Positive and Gram-Negative Organisms Collected from Italy between 2012 and 2014, as Part of the Tigecycline Evaluation and Surveillance Trial (T.E.S.T.)

Antibiotic Susceptibility Patterns for Carbapenem-Resistant Enterobacteriaceae

Carbapenem is a broad-spectrum beta-lactam antibiotic considered the last choice for the treatment of antibiotic-resistant Gram-negative bacteria. Thus, the increasing rate of carbapenem resistance (CR) in Enterobacteriaceae is an urgent public health threat. This study aimed to evaluate the antibiotic susceptibility pattern of carbapenem-resistant Enterobacteriaceae (CRE) to new and old antibiotics. In this study, Klebsiella pneumoniae, E. coli, and Enterobacter spp. were collected from 10 hospitals in Iran for one year. CRE is recognized by resistance to meropenem and/or imipenem disk after identification of the collected bacteria. Antibiotic susceptibility of CRE against fosfomycin, rifampin, metronidazole, tigecycline, and aztreonam was detected by disk diffusion method and colistin by MIC. In this study, 1222 E. coli, 696 K. pneumoniae, and 621 Enterobacter spp. were collected from 10 hospitals in Iran in one year. Fifty-four E. coli (4.4%), 84 K. pneumoniae (12%), and 51 Enterobacter spp. (8.2%) were CRE. All CRE strains were resistant to metronidazole and rifampicin. Tigecycline has the highest sensitivity on CRE and levofloxacin for Enterobacter spp. Tigecycline showed an acceptable effectiveness rate of sensitivity on the CRE strain. Therefore, we suggest that clinicians consider this valuable antibiotic to treat CRE.

Insight into Acinetobacter baumannii: pathogenesis, global resistance, mechanisms of resistance, treatment options, and alternative modalities

Acinetobacter baumannii, once considered a low-category pathogen, has emerged as an obstinate infectious agent. The scientific community is paying more attention to this pathogen due to its stubbornness to last resort antimicrobials, including carbapenems, colistin, and tigecycline, its high prevalence of infections in the hospital setting, and significantly increased rate of community-acquired infections by this organism over the past decade. It has given the fear of pre-antibiotic era to the world. To further enhance our understanding about this pathogen, in this review, we discuss its taxonomy, pathogenesis, current treatment options, global resistance rates, mechanisms of its resistance against various groups of antimicrobials, and future therapeutics.

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

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

Bloodstream infections caused by Acinetobacter species with reduced susceptibility to tigecycline: clinical features and risk factors

INTRODUCTION

During recent decades, the rates of multidrug resistance, including resistance to carbapenems, have increased dramatically among Acinetobacter species. Tigecycline has activity against multidrug-resistant Acinetobacter spp, including carbapenem-resistant isolates. However, reports of tigecycline-resistant Acinetobacter spp are emerging from different parts of the world. The purpose of this study was to evaluate potential risk factors associated with tigecycline non-susceptible Acinetobacter bacteremia.

METHODS

The medical records of 152 patients with Acinetobacter bacteremia attending Samsung Medical Center between January 2010 and December 2014 were reviewed. Non-susceptibility to tigecycline was defined as a minimum inhibitory concentration (MIC) of tigecycline ≥4μg/ml. Cases were patients with tigecycline non-susceptible Acinetobacter bacteremia and controls were those with tigecycline-susceptible Acinetobacter bacteremia.

RESULTS

Of the 152 patients included in the study, 61 (40.1%) had tigecycline non-susceptible Acinetobacter bacteremia (case group). These patients were compared to 91 patients with tigecycline-susceptible Acinetobacter bacteremia (control group). The case group showed high resistance to other antibiotics (>90%) except colistin (6.6%) and minocycline (9.8%) when compared to the control group, which exhibited relatively low resistance to other antibiotics (<50%). Multivariate analysis showed that recent exposure to corticosteroids (minimum 20mg per day for more than 5 days within 2 weeks) (adjusted odds ratio (OR) 2.887, 95% confidence interval (CI) 1.170-7.126) and carbapenems (within 2 weeks) (adjusted OR 4.437, 95% CI 1.970-9.991) were significantly associated with tigecycline non-susceptible Acinetobacter bacteremia. Although prior exposure to tigecycline was more common in the case group than in the control group (9.8%, 6/61 vs. 2.2%, 2/91; p=0.046), this variable was found not to be a significant factor associated with tigecycline non-susceptibility after adjustment for other variables (adjusted OR 1.884, 95% CI 0.298-11.920; p=0.501).

CONCLUSIONS

These data suggest that tigecycline non-susceptible Acinetobacter spp have emerged and disseminated in the hospital in association with a recent exposure to carbapenems and an immunosuppressed state. This indicates that the rational use of antibiotics through a comprehensive antimicrobial stewardship program, especially in immunosuppressed patients, may be essential in limiting the emergence and spread of multidrug-resistant organisms such as tigecycline-resistant Acinetobacter spp, which are difficult to treat.