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.

Sources and further readings

  1. Wong, D et al. Clinical and pathophysiological overview of Acinetobacter
    infections: a century of challenges. Clin Microbiol Rev. 2016; 30: 409–447.

  2. Gales, A. C. Antimicrobial Susceptibility of Acinetobacter calcoaceticus-Acinetobacter baumannii complex and Stenotrophomonas maltophilia. Clinical
    Isolates: Results from the SENTRY Antimicrobial Surveillance Program (1997–
    2016). Open Forum Infectious Diseases, 2019, 6 (Suppl. 1): 34–46.

  3. Higgins, P. G. et al. gyrB Multiplex PCR to Differentiate between Acinetobacter
    and Acinetobacter Genomic Species 3. Journal of Clinical
    Microbiology 2010, 48: 4592–4594.

  4. Stone, W, Das, C. Investigation of an outbreak of infection with Acinetobacter
    in a special care baby unit. J Hosp Infect. 1986 7(1):42–8.

  5. Buxton, A. E. et al. Nosocomial respiratory tract infection and colonization with
    Acinetobacter calcoaceticus. Epidemiologic characteristics. Am J Med. 1978,
    65(3): 507–13.

  6. Sun Y et al. Characterization and Plasmid Elimination of NDM-1-Producing
    Acinetobacter calcoaceticus from China. PLoS ONE, 2014, 9(9): e106555.

  7. Atrouni, A. A. et al. Reservoirs of Non-baumannii Acinetobacter Species. Front.
    Microbiol. 2016; 7:49.

  8. Li et al. 1. Acinetobacter calcoaceticus from a fatal case of pneumonia harboring
    blaNDM-1 on a widely distributed plasmid. BMC Infectious Diseases, 2015,15: 131.