A. aestus, A. aquamarinus, A. cupidus, A. pacificus and A. venustus were first reclassified to the genus Deleya and later merged into Halomonas in the class of Gammaproteobacteria.

A. denitrificans, A. piechaudii, A. ruhlandii and A. xylosoxidans are currently placed in Achromobacter,[4] A. latus in Azohydromonas,[5] A. eutrophus in Wautersia,[6] and A. paradoxus in Variovorax.

[12][13] A. faecalis is a known causing agent of nosocomial bacterial sepsis in immunocompromised patients by contaminated hemodialysis or intravenous fluid.

[13] Cases of meningitis, peritonitis,[14] enteric fever, appendicitis, cystitis, chronic suppurative otitis media, abscesses, arthritis, pneumonitis and endocarditis[15] associated with Alcaligenes have been reported,[clarification needed] including a zoonotic infection from ferrets.

[15] An increased recovery rate of Alcaligenes species from patients with cystic fibrosis was reported in 2001,[16] though the most commonly identified strain A. cylosoxidans has since been transferred to Achromobacter.