Phenotypical and Molecular Characterization of Pseudomonas spp. Isolated from a Pharmaceutical Facility

The characterization of environmental Pseudomonas spp. from pharmaceutical industries is a relatively underexplored area of research. This study used 40 isolates of Pseudomonas from a pharmaceutical company that had been presumptively identified as Pseudomonas aeruginosa by VITEK®2. The isolates were characterized using 16S rRNA sequencing, Multilocus Sequence Typing (MLST), Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass (MALDI–TOF MS), Fourier Transform Infrared (FT-IR) spectroscopy, ERIC-PCR, antimicrobial susceptibility profiling, and biofilm formation assessment on stainless steel surfaces. Twenty isolates were confirmed as P. aeruginosa. Sixteen isolates were only identified to the genus level of Pseudomonas, and the remaining four isolates were identified as Enterococcus faecalis (n = 2), Proteus spp. (n = 1), and Staphylococcus saprophyticus subsp. bovis/S. edaphicus/S. saprophyticus subsp. saprophyticus/S. pseudoxylosus/S. xylosus/S. caeli/S. ureilyticus. Typing of the 20 P. aeruginosa strains yielded 18 distinct FT-IR profiles and 19 ERIC-PCR profiles. The MLST analysis identified eight new sequence types (ST4292–ST4299). All strains were classified as multidrug-resistant (MDR), exhibiting resistance to multiple antimicrobial classes. Biofilm formation was observed in 28 (77.8%) Pseudomonas spp. strains on polystyrene surfaces, classified as moderately or strongly adherent, while all P. aeruginosa strains formed biofilms on stainless steel. Of the three disinfectants tested, sodium hypochlorite at 0.01% showed the best performance, reducing or eliminating biofilm formation in 24 (85.7%) strains. The regular evaluation of disinfection effectiveness in pharmaceutical industries is essential, as the presence of biofilm-forming strains can compromise production and contaminate final products.