Clusters and outbreaks of nosocomial infections occur frequently in neonatal care units (NCU). Achromobacter and Alcaligenes are emerging, infectious, gram-negative, oxidative, bacterial species that can affect immunocompromised patients and those with underlying illnesses. Epidemiological data suggest that water is the natural source of A. xylosoxidans and that most infections may be waterborne [1–3]. Holmes et al. [2] previously described clinical material as the source of this pathogen. In the literature, sporadic cases of bacteremia have appeared [3–5], but outbreaks in adults and newborns have also been reported [6–9]. Some environmental sources contaminated with A. xylosoxidans and associated with nosocomial infections include swimming pools [2], respirators, humidifiers, incubators [6], deionized water [7], tap water, and chlorhexidine solutions [2, 7, 8]. Between January 2004 and June 2005, 58 cases of Achromobacter xylosoxidans colonization or infection occurred in 52 neonates admitted to the NCU of the University Children’s Hospital in Las Palmas, Spain. This NCU is a level III neonatal reference unit that admits a mean of 1,350 newborns annually. It has 15 beds for intensive care, 10 for intermediate care and 30 for minimal care. A case of nosocomial infection was defined as one culture or more that tested positive for Achromobacter xylosoxidans in samples obtained from any body site when clinical evidence of infection in the neonatal population was present. In the absence of clinical evidence of infection, patients with positive results were considered colonized. All infecting strains were considered nosocomially acquired. Medical and nursing procedures were additionally reviewed. Bacteriological cultures of environmental objects such as soaps, antiseptic solutions (chlorhexidine digluconate, aqueous and alcoholic), containers of such solutions, washbasins, incubator surfaces, and faucets were performed. The hands of 39 healthcare workers were sampled by direct fingerprinting in Petri dishes. Fluids were filtered through 0.45 μm membranes (Millipore, Bedford, MA, USA) and cultivated on sheep blood agar (bioMerieux, Marcy l’Etoile, France). For antiseptics, the membranes were rinsed three times with distilled water and cultivated on Tryptic soy agar with Tween 80 (bioMerieux). The swabs were plated onto McConkey and 5% sheep blood agar. Plates were incubated for 24 h at 36°C. Since October 2004, environmental cultures have been performed regularly, but no positive results were obtained prior to June 2005. Biochemical testing was performed using the Vitek System Gram Negative Identification Card (bioMerieux, Durham, USA). Antimicrobial susceptibility testing was performed using standard techniques and Sensititre EMIZA 9EF panels (Trek Diagnostic Systems, West Sussex, UK). Pulsed-field gel electrophoresis (PFGE) of XbaI-digested genomic DNA was performed with a Chief DR-III system (Bio-Rad Laboratories, Hercules, CA, USA). The Statistical Package for the Social Sciences (SPSS, version 11.0) was used for statistical analysis. Eur J Clin Microbiol Infect Dis (2007) 26:435–437 DOI 10.1007/s10096-007-0311-7