Abstract
Nonhuman primates are commonly used for cognitive neuroscience research and often surgically implanted with cephalic recording chambers for electrophysiological recording. Aerobic bacterial cultures from 25 macaques identified 72 bacterial isolates, including 15 Enterococcus faecalis isolates. The E. faecalis isolates displayed multi-drug resistant phenotypes, with resistance to ciprofloxacin, enrofloxacin, trimethoprim-sulfamethoxazole, tetracycline, chloramphenicol, bacitracin, and erythromycin, as well as high-level aminoglycoside resistance. Multi-locus sequence typing showed that most belonged to two E. faecalis sequence types (ST): ST 4 and ST 55. The genomes of three representative isolates were sequenced to identify genes encoding antimicrobial resistances and other traits. Antimicrobial resistance genes identified included aac(6’)-aph(2”), aph(3’)-III, str, ant(6)-Ia, tetM, tetS, tetL, ermB, bcrABR, cat, and dfrG, and polymorphisms in parC (S80I) and gyrA (S83I) were observed. These isolates also harbored virulence factors including the cytolysin toxin genes in ST 4 isolates, as well as multiple biofilm-associated genes (esp, agg, ace, SrtA, gelE, ebpABC), hyaluronidases (hylA, hylB), and other survival genes (ElrA, tpx). Crystal violet biofilm assays confirmed that ST 4 isolates produced more biofilm than ST 55 isolates. The abundance of antimicrobial resistance and virulence factor genes in the ST 4 isolates likely relates to the loss of CRISPR-cas. This macaque colony represents a unique model for studying E. faecalis infection associated with indwelling devices, and provides an opportunity to understand the basis of persistence of this pathogen in a healthcare setting.
Highlights
Nonhuman primates (NHP) are an important animal model in cognitive neuroscience research, with the macaque (Macaca spp.) being the most commonly utilized species [1]
Kirby-Bauer testing revealed that while S. aureus isolates were susceptible to the majority of antimicrobials tested, E. faecalis and Proteus spp. isolates were multi-drug resistant
We identified virulence factor genes associated with biofilm formation including aggregation substance, enterococcal surface protein, adhesion of collagen from E. faecalis, gelatinase, endocarditis and biofilm-associated pili genes (Ebp) and sortase A (SrtA) [35, 45,46,47,48]
Summary
Nonhuman primates (NHP) are an important animal model in cognitive neuroscience research, with the macaque (Macaca spp.) being the most commonly utilized species [1]. Implanted cephalic chambers allow placement of microelectrodes into specific regions of the brain to monitor the activity of individual neurons (Fig 1). Materials commonly used in cephalic recording chamber implants include CILUX plastic (CRIST Instruments), titanium, stainless steel, thermoplastic polyetherimide Ultem (Gray Matter Research), polymethyl methacrylate acrylic and combinations of these materials. Trichosporon beigelii as common bacterial and fungal contaminants of recording chambers and S. aureus, Streptococcus spp., Corynebacterium spp., and Enterococcus spp. as common bacterial isolates from the skin-cranial implant margin [4,5,6]. C. ulcerans isolated from the skin-cranial implant margin was found to be doi:10.1371/journal.pone.0169293.g001
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