Acinetobacter calcoaceticus

Acinetobacter calcoaceticus is a nonfermenting, Gram-negative, aerobic coccobacilli,
belonging to the genus of bacteria known as Acinetobacter and to the Moraxellaceae
family. The genus Acinetobacter includes more than 50 species [1].

Together with the species A. baumannii, A. dijkshoorniae, A. nosocomialis, A. pittii and A. seifertii, A. calcoaceticus forms part of the so-called Acinetobacter-calcoaceticus-A.- baumannii complex (the ACB complex). The species that make up the ACB complex are more closely related than other species of Acinetobacter and are phenotypically very similar [2].

It is not usually possible to differentiate between the individual species using routine identification programs [3]. In cases where Acinetobacter calcoaceticus is detected, it is not possible to rule out confusion with the clinically most important representative of the ACB complex, A. baumannii [2][3].

Acinetobacter calcoaceticus has only rarely been isolated from human clinical specimens (e.g. sputum). Its involvement in clinical infections therefore remains unclear.

The clinical pictures relate to cases of:

A. calcoaceticus is an environmental pathogen found primarily in soil and water. The bacterium has also been detected in wastewater and on human skin, as well as on animals and vegetables [7].

Relevance of pathogen in transmission in endoscopy

  • Gastroenterology: Not relevant

  • Pulmonology: Low

  • Ear, nose, and throat: Not relevant

  • Urology: Not relevant

Relevance for endoscope surveillance

  • High concern organism

Transmission route

Transmission occurs through direct or indirect contact, e.g. via contaminated materials
and objects, as well as via the hands of medical professionals [4][5].

Resistance to antibiotics

The individual species of the A. calcoaceticus-A. baumannii complex (ACB) are difficult to distinguish from one another based on their phenotypic characteristics. A. calcoaceticus can usually be ruled out when resistance patterns are investigated [6]. Two studies conducted in China have identified clinical isolates with the resistance gene blaNDM-1 on plasmids [6][8]. This gene enables the production of the New Delhi metallo-betalactamase (NDM-1) enzyme, which inactivates antibiotics of the carbapenem class. The resistance gene can be transferred to other species and contribute to the further spread of antibiotic-resistant strains of bacteria.