Identifying genetic diversity of O antigens in Aeromonas hydrophila for molecular serotype detection

Abstract

Aeromonas hydrophila is a globally occurring, potentially virulent, gram-negative opportunistic pathogen that is known to cause water and food-borne diseases around the world. In this study, we use whole genome sequencing and in silico analyses to identify 14 putative O antigen gene clusters (OGCs) located downstream of the housekeeping genes acrB and/or oprM. We have also identified 7 novel OGCs by analyzing 15 publicly available genomes of different A. hydrophila strains. From the 14 OGCs identified initially, we have deduced that O antigen processing genes involved in the wzx/wzy pathway and the ABC transporter (wzm/wzt) pathway exhibit high molecular diversity among different A. hydrophila strains. Using these genes, we have developed a multiplexed Luminex-based array system that can identify up to 14 A. hydrophila strains. By combining our other results and including the sequences of processing genes from 13 other OGCs (7 OGCs identified from publicly available genome sequences and 6 OGCs that were previously published), we also have the data to create an array system that can identify 25 different A. hydrophila serotypes. Although clinical detection, epidemiological surveillance, and tracing of pathogenic bacteria are typically done using serotyping methods that rely on identifying bacterial surface O antigens through agglutination reactions with antisera, molecular methods such as the one we have developed may be quicker and more cost effective. Our assay shows high specificity, reproducibility, and sensitivity, being able to classify A. hydrophila strains using just 0.1 ng of genomic DNA. In conclusion, our findings indicate that a molecular serotyping system for A. hydrophila could be developed based on specific genes, providing an important molecular tool for the identification of A. hydrophila serotypes.

Prediction and Analysis in silico of Genomic Islands in Aeromonas hydrophila

“…It consists of repeating oligosaccharide subunits whose variability confers immunological specificity ( Tomás, 2012 ). Several O Ag gene cluster types have been described in A. hydrophila ( Hossain et al, 2013 ; Pang et al, 2015 ; Cao et al, 2018 ) and previously associated with GIs ( Hossain et al, 2013 ; Pang et al, 2015 ). Gene clusters for O Ag were found in the predicted GIs of all strains; however, they differed in their gene content and were related to 10 distinct serogroups ( Figure 2 ).…”

“…Thirteen of the strains analyzed in this study had their O Ag gene clusters previously determined ( Hossain et al, 2013 ; Pang et al, 2015 ; Cao et al, 2018 ).…”

“…The putative serogroup OX1 was proposed for strains ML09-119, AL09-71, pc104a, JBN2301, and D4 strains ( Cao et al, 2018 ). Strain ZYAH72, which had no previously analyzed O Ag cluster, shared the same cluster with the strains above ( Figure 2 ).…”

Structural Studies of the Lipopolysaccharide of Aeromonas veronii bv. sobria Strain K133 Which Represents New Provisional Serogroup PGO1 Prevailing among Mesophilic Aeromonads on Polish Fish Farms

“…serotyping, the original classification scheme proposed by Sakazaki and Shimada, which included 44 different O-serogroups (the NIH scheme; National Institute of Health, Japan), was later supplemented by addition of new provisional serogroups, and it currently consists of 97 O-serogroups [ 21 , 22 ]. Serotyping of pathogenic bacteria leads to recognition of the etiological agent associated with specific disease syndrome [ 23 ]. Since there are differences in the distribution of the dominant O-serogroups responsible for the onset of various diseases depending on geographical regions [ 24 ], as evidenced by epidemiological studies carried out in various areas, including Polish aquacultures indicating to the emergence of new O-antigen variants, there are reasons to extend further or modify the classical serogrouping scheme [ 25 , 26 , 27 ].…”

Structural and Serological Studies of the O6-Related Antigen of Aeromonas veronii bv. sobria Strain K557 Isolated from Cyprinus carpio on a Polish Fish Farm, which Contains l-perosamine (4-amino-4,6-dideoxy-l-mannose), a Unique Sugar Characteristic for Aeromonas Serogroup O6

“…The O-specific polysaccharide is a surface antigen called the somatic O-antigen, whose high degree of diversity determines the specificity of each bacterium and gives the basis for their serological classification. Serotyping to identify bacterial strains is invaluable for epidemiological investigations since many O-serotypes are associated with specific disease syndromes [21,24].…”