Spanish teaching hospital study finds rare but notable Acinetobacter AMR

A research team at the Complutense University of Madrid is adding a useful datapoint to veterinary antimicrobial resistance surveillance in Spain: Acinetobacter appears to be rare in its veterinary teaching hospital, but not absent, and not entirely susceptible. In a preprint posted March 25, 2026, the authors described 23 suspect isolates collected over 27 years from the Complutense Veterinary Teaching Hospital, with whole-genome sequencing confirming 13 as Acinetobacter spp. Those confirmed isolates accounted for 0.3% of clinical isolates at the hospital, and four of the 13 were classified as multidrug-resistant. (preprints.org)

That low prevalence matters because Acinetobacter has long carried outsized significance in human healthcare. A. baumannii is one of the best-known hospital-associated Gram-negative pathogens, valued by infection-control teams less for how often it appears than for how hard it can be to eradicate once established. WHO’s 2024 bacterial priority pathogens list continues to place carbapenem-resistant A. baumannii in the critical-priority category, reflecting its public health importance. In veterinary medicine, previous reviews and companion-animal studies have already shown why the genus draws attention: it can persist on surfaces, form biofilms, and pick up multidrug resistance, particularly in hospitalized animals and clinic environments. (who.int)

The Spanish study also highlights a practical diagnostic issue. Of the 23 presumptive isolates, only 13 were confirmed as Acinetobacter by whole-genome sequencing, underscoring how species-level identification can be difficult with routine methods alone. Five of the 13 confirmed isolates were A. baumannii. The isolates came from multiple animal species and sample types, including cats, dogs, horses, tortoises, a sheep, and a rabbit, which suggests the organism’s veterinary relevance is broad even if its frequency is low. The authors used MALDI-TOF, VITEK-2, whole-genome sequencing, and chromogenic media for identification, then assessed susceptibility with disk diffusion and broth microdilution interpreted under CLSI guidance. (preprints.org)

On resistance, the headline is mixed. The authors say overall AMR frequency was low, and they conclude resistance in veterinary-origin Acinetobacter in Spain may not yet be widespread. But the details still deserve attention. Four of the 13 confirmed isolates were multidrug-resistant, two isolates with the highest temocillin MICs carried tet(X), and two had mutations in both gyrA and parC associated with quinolone resistance. The preprint also notes that some phenotypes, including tigecycline and temocillin, could not be fully interpreted because species-specific breakpoints were lacking, which is an important limitation for clinicians trying to translate surveillance findings into treatment decisions. (preprints.org)

There doesn’t appear to be broad outside commentary on this specific preprint yet, but the surrounding field points in the same direction: low-frequency detection should not be confused with low consequence. A 2024 MDPI study from Greece described A. baumannii from companion animals as an emerging nosocomial challenge tied to hospitalization, multidrug resistance, and persistence in healthcare facilities through biofilm formation. Separately, reporting on a pilot surveillance effort at the same Madrid veterinary hospital described active screening of patients, staff, and the environment for resistant organisms, reinforcing that the institution has already been building a broader AMR surveillance framework rather than treating resistant bacteria as isolated case findings. (mdpi.com)

Why it matters: For veterinary professionals, this is a reminder that surveillance value isn’t limited to finding a crisis. Negative space matters. Knowing that confirmed Acinetobacter represented just 0.3% of isolates in this setting gives hospitals a baseline, while the multidrug-resistant fraction shows why infection prevention programs still need to include non-fermenting Gram-negative organisms that may be sporadic but operationally important. Referral hospitals, ICUs, surgical services, oncology services, and long-stay wards may want to pay particular attention to environmental cleaning, device handling, culture workups in refractory infections, and antimicrobial selection policies for hospitalized patients. WOAH’s recent AMR standards revisions explicitly broaden the scope to companion animals, reflecting the same One Health concern raised by this paper: resistant organisms that circulate in human healthcare can also appear in veterinary care settings over time. (preprints.org)

What to watch: The immediate next step is peer review, since the available manuscript is still a preprint as of March 25, 2026. After that, the bigger question is whether multicenter Spanish or European veterinary surveillance will confirm the same pattern: low detection frequency, but enough multidrug resistance to justify routine monitoring and tighter infection-control protocols in teaching and referral hospitals. (preprints.org)