A retrospective study of the incidence, clinical characteristics, identification, and antimicrobial susceptibility of bacteremic isolates of Acinetobacter ursingii

Abstract

BackgroundAcinetobacter ursingii bacteremia is rarely reported. We investigated the incidence and clinical features of A. ursingii bacteremia, performance of the identification system, and antimicrobial susceptibility of the isolates. Acinetobacter ursingii bacteremia patients were compared with A. baumannii bacteremia patients.MethodsIn this 9-year retrospective study, A. ursingii was identified using 16S rRNA and 16S–23S rRNA internal transcribed spacer sequence analysis. The performances of the Vitek 2, Phoenix, and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometer systems for identifying isolates were tested. Pulsed-field gel electrophoresis (PFGE) was used to determine the clonality of the isolates. The minimal inhibitory concentrations of the antimicrobials were determined using the Vitek 2 system.ResultsNineteen patients were identified. Acinetobacter ursingii was noted in 1.5–5.2 % of all Acinetobacter bacteremia cases. For the PFGE analysis, two isolates had smeared DNA, two had 93 % similarity, and 15 had similarity <80 %. Among 16 patients with complete medical records, 10 (62.5 %) had no identifiable source of A. ursingii bacteremia. Most patients (n = 12) had underlying malignant disease. Patients with A. ursingii bacteremia had lower Acute Physiology and Chronic Health Evaluation II scores than those with A. baumannii bacteremia (median [interquartile range], 17.1 [10.0–24.7] vs. 24.9 [14.6–35.1]). Patients with A. ursingii bacteremia were also less likely admitted to the intensive care unit than patients with A. baumannii bacteremia (18.8 % vs 63.5 %, p value < 0.01). About half of the patients with A. ursingii (50.8 %) and A. baumannii bacteremia (62.5 %) had received inappropriate antimicrobial therapy within 48 h after bacteremia onset. However, patients with A. ursingii bacteremia had significantly lower 14-day (6.25 % vs 29.8 %, p value = 0.04) and 28-day mortality rates (6.25 % vs 37.3 %, p value = 0.02) than patients with A. baumannii bacteremia. Nine isolates (47.4 %) were correctly identified as A. ursingii and the other 10 isolates (52.6 %) were incorrectly identified as A. lwoffii by the Vitek 2 system. The Phoenix system incorrectly identified all 19 isolates. The MALDI-TOF mass spectrometer system correctly identified all 19 isolates. All the A. ursingii isolates were resistant or showed intermediate susceptibility to ceftriaxone and ceftazidime, but were susceptible to levofloxacin and imipenem.ConclusionsAcinetobacter ursingii is a rare pathogen that mostly caused primary bacteremia in patients with malignancies. Patients with A. ursingii bacteremia had significantly lower disease severity and mortality rates than patients with A. baumannii bacteremia.

Clinical and Pathophysiological Overview of Acinetobacter Infections: a Century of Challenges

“…Furthermore, the clinical strains of non-baumannii Acinetobacter species were substantially less lethal during infection in wax moth larvae of Galleria. Similarly, in a case-control study, patients infected with A. ursingii had much lower 28-day mortality than those infected with A. baumannii (6% versus 37%) even though multidrug resistance and inadequate initial therapy were as likely to occur in patients infected with either species (10).…”

“…The most common species to cause infections is A. baumannii, followed by A. calcoaceticus and A. lwoffii (4). Additional species, including A. haemolyticus, A. johnsonii, A. junii, A. nosocomialis, A. pittii, A. schindleri, and A. ursingii, have occasionally been reported as pathogens (5)(6)(7)(8)(9)(10)(11). A. seifertii is an emerging pathogen in Asia; it is genetically closely related to and may be misidentified as A. baumannii (12)(13)(14).…”

Late-onset neonatal sepsis:Acinetobacterursingiias an infectious agent

“…Although there has been reports of deaths and morbidity associated with neonatal outbreaks due to A. ursingii ,9 a retrospective study by Chiu et al concluded that patients with A. ursingii bacteraemia usually have overall lower disease severity and mortality rates than patients with A. baumannii bacteraemia,8 which might explain the good outcome seen in our case.…”

“…Acinetobacter infections in neonatal intensive care units are described in literature, but the subspecies ursingii is rarely isolated 2. In a study by Chiu et al , of a sample of 616 patients with Acinetobacter species bacteraemia, 3.1% were identified as A. ursingii 8. It has lower pathogenic potential than A. baumannii , but it has also been recognised as an opportunistic agent in hospitalised and immunocompromised patients 2…”

A Case Report of Persistent Acinetobacter baumannii Bloodstream Infection

“…Bloodstream infection due to Acinetobacter baumannii is characteristically a nosocomial infection with a fatality rate of up to 37% (1). Suspicion of bloodstream infection warrants immediate blood tests, and if bloodstream infection is confirmed, pathogen-based treatment should be initiated immediately.…”