This in vitro study aimed to determine the activity of colistin plus sulbactam and colistin plus fosfomycin against carbapenem-resistant A. baumannii (CRAB). Fifteen clinical isolates were obtained from patients admitted to Phyathai II International Hospital, Bangkok, Thailand, from August 2014 to April 2015. The antimicrobial susceptibilities of colistin, sulbactam, and fosfomycin were evaluated using the E-test or broth microdilution and the synergistic activity of the antibacterial combinations (colistin plus sulbactam or fosfomycin) was determined using the chequerboard method. Clonal relationships were explored using repetitive element palindromic- (REP-) PCR. The CRAB isolates were categorized by REP-PCR in 8 groups [A-H]. All CRAB isolates were universally susceptible to colistin but only 20.0% were susceptible to sulbactam. The MIC ranges for colistin, sulbactam, and fosfomycin were 0.75–2 mg/L, 2–96 mg/L, and 64–256 mg/L, respectively. A chequerboard assay revealed that the rates of synergistic and additive effect rates of colistin plus sulbactam and colistin plus fosfomycin were 53.3% and 73.3% of isolates, respectively. No antagonistic effect in any colistin-based combination was observed. However, almost CRAB strains in clone A showed the synergy or additive effects of colistin-sulbactam combination, whereas the other clone (B-H) mostly showed indifferent effects. In conclusion, colistin plus sulbactam and colistin plus fosfomycin against CRAB seem to be interesting option but the efficacy in clinical use has to be evaluated.

BackgroundProcalcitonin (PCT) is a diagnostic biomarker for bacterial infections in critically-ill patients. However, the cut-off value of PCT for the diagnosis of bacterial infections is unclear and unreliable. This study aimed to determine the optimal cut-off value of PCT for the diagnosis of bacterial infections in critically-ill patients.Materials and MethodsWe conducted a retrospective study involving 311 adult patients who had been admitted to the medical or surgical intensive care unit for more than 24 hours from 2013 to 2015. At least one blood test for PCT level was performed for all patients within the first 24 hours of suspecting an infection.ResultsOne hundred and fifty-seven patients had bacterial infections, while 154 did not. Patients with bacterial infections had a significantly higher median PCT level than those without bacterial infections (1.90 ng/mL vs. 0.16 ng/mL, P <0.001). The area under the receiver operating characteristic curve of PCT for discriminating between bacterial and non-bacterial infections was 0.874 (95% confidence interval: 0.834, 0.914; P <0.001). The optimal cut-off value of PCT for differentiating between fevers due to bacterial infections from those due to non-bacterial infections was 0.5 ng/mL, with a sensitivity of 84.7%, specificity of 79.9%, positive predictive value of 81.1%, and negative predictive value of 83.7%.ConclusionPCT was found to be an accurate biomarker for the diagnosis of bacterial infections among patients admitted to medical and surgical intensive care units. The optimal cut-off value of PCT for the diagnosis of bacterial infections was 0.5 ng/mL.

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A cinetobacter baumannii, a Gram-negative coccobacilli, is a major causative pathogen involving nosocomial infection in various organs, such as the lower respiratory tract, skin/soft tissue, blood and, rarely, in the urinary tract and central nervous system. 1 In Thailand, regarding the data of the first half-year of 2018, 2 A. baumannii was the third and second ranked organism isolated from all specimens and sputum, respectively. This pathogen is not only an important nosocomial pathogen, but also has multiple mechanisms to resist the current antimicrobials varied from multi-drug treatment (more than three groups), extensive drug resistance (resistant to all antibiotics except colistin and tigecycline) to pan-drug (resistant to all available antibiotics). 3 Over the past 19 years (from 2000-2018), the prevalence of carbepenem resistant A. baumannii (CRAB) has increased. 2 The National Antimicrobial Resistance Surveillance, Thailand (NARST) reported that among A. baumannii isolates from hospitalized patients in 50 hospitals, the rate of CRAB increased from 5.8% in 2000 to 52.5% in 2018. 2 However, the increasing rate of CRAB has affected carbapenems use as empirical therapy for infections suspected of A. baumannii. The known type of carbapenemase enzyme in CRAB remains important for some circumstances including the role of carbapenems in combination with the other antimicrobials against CRAB and the upcoming use of new betalactamase inhibitor such as avibactam against carbapenemase producing organisms. 4,5 To date, carbapenem-destroying enzymes in CRAB have been found in two major types, namely, OXA-carbapenemases and metallo-beta lactamases. 1

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