Detection, identification and antimicrobial susceptibility study of Arcobacter spp. isolated from shellfish in Spain

Abstract

[EN] This work aimed to determine the presence of Arcobacter spp. in shellfish and to determine its susceptibility to quinolones. One hundred samples (41 mussels, 37 clams, and 22 cockles) were purchased from different local retail shops in Valencia, Spain from September 2013 to June 2015. All samples were analyzed simultaneously by culture, after an enrichment step, and by PCR, directly and after enrichment. The susceptibility to levofloxacin and ciprofloxacin of the isolates was tested using the disk-diffusion test and E-test strips method. To clarify the mechanism of quinolone resistance, a fragment of the quinolone resistance-determining region (QRDR) of the gyrA gene was sequenced. 37 samples were positive and 49 isolates were obtained by culture, and Arcobacter spp. DNA was detected in 32% of the samples by PCR. However, after 48 h enrichment, the number of positive samples increased, and 68 of the 100 samples yielded the specific Arcobacter spp. PCR product. In addition, 49 isolates were identified by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The most commonly found species was A. butzleri (25 isolates, 51.03%) followed by A. cryaerophilus (19 isolates, 38.77%) and A. defluvii (5 isolates, 10.20%). Only three isolates of A. butzleri were resistant to both antibiotics. A mutation C to T transition in the position 254 of the gyrA gene was present in the three resistant isolates. This study confirms that pathogenic arcobacters are frequently found in edible shellfish samples. Moreover, this is the first time that A. butzleri and A. cryaerophilus have been isolated from cockles.