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The increase in the use of antimicrobials such as colistin for the treatment of infectious diseases has led to the appearance of Aeromonas strains resistant to this drug. However, resistance to colistin not only occurs in the clinical area but has also been determined in Aeromonas isolates from the environment or animals, which has been determined by the detection of mcr genes that confer a resistance mechanism to colistin. The variants mcr-1 , mcr-3 , and mcr-5 have been detected in the genus Aeromonas in animal, environmental, and human fluids samples. In this article, an overview of the resistance to colistin in Aeromonas is shown, as well as the generalities of this molecule and the recommended methods to determine colistin resistance to be used in some of the genus Aeromonas .

Introduction: Intestinal and extraintestinal infections by Aeromonas spp., remain controversial, due to the existence of healthy carriers of Aeromonas spp. In children under five years old, the diarrhea of infectious origin constitutes the second cause of mortality and remains a major concern for public health. The aim of this work was to detect the pheno/genotype of β-lactamases and class 1 integrons in Aeromonas spp., strains isolated from pediatric patients in a tertiary referral hospital in Mexico., Methodology: Sixty-six strains of Aeromonas spp., were isolated from clinical samples of pediatric origin and were identified by RFLP-PCR 16S rRNA. Resistance phenotype according to CLSI, genetic and phenotypic detection of extended-spectrum β-lactamases (ESBL) and metallo-b-lactamases (MBL) was performed. Finally, characterization of class 1 integrons was performed., Results: Aeromonas spp., strains of diarrheic origin were more predominant. A wide heterogeneity was detected, where A. caviae was the predominant specie. Second-generation cephalosporins, fluoroquinolones, and nitrofurans had best antimicrobial activity; moreover, antibiotics of the β-lactamic and lincosamides families showed lower inhibitory activity. Phenotypically, prevalences of 4.55% and 3.03% were detected for MBL (intestinal origin) and ESBL (extraintestinal origin), respectively. blaIMIS-cphA and blaTEM-1 genes, and nineteen class 1 integrons carrying two variants of cassettes corresponding to adenylyl transferases (aadA), and dihydrofolate reductases (dfrA). Monogenic array with aadA1 cassette was predominantly., Conclusions: ESBL and class 1 integrons, in Aeromonas collected from pediatric patients, determines a major detection challenge for the clinical microbiology laboratory and represents a remarkable epidemiological risk of nosocomial spread of multidrug-resistant determinants., Competing Interests: No Conflict of Interest is declared, (Copyright (c) 2020 Juan Manuel Bello-Lopez, Carlos Sanchez-Garibay, Gabriela Ibanez-Cervantes, Gregorio Leon-García, Luis Uriel Gonzalez-Avila, Cecilia Hernandez-Cortez, Patricia Arzate Barbosa, Graciela Castro-Escarpulli.)

With the increasing antibiotic resistance of bacterial strains, alternative methods for infection control are in high demand. Quorum sensing (QS) is the bacterial communication system based on small molecules. QS is enables bacterial biofilm formation and pathogenic development. The interruption of QS has become a target for drug discovery, but remains in the early experimental phase. In this study, we synthesized a set of six compounds based on a scaffold (alkyl-quinoxalin-2(1 H )-one), new in the anti-QS of Gram-negative bacteria Aeromonas caviae Sch3. By quantifying biofilm formation, we were able to monitor the effect of these compounds from concentrations of 1 to 100 µM. Significant reduction in biofilm formation was achieved by 3-hexylylquinoxalin-2(1 H )-one ( 11 ), 3-hexylylquinoxalin-2(1 H )-one-6-carboxylic acid ( 12 ), and 3-heptylylquinoxalin-2(1 H )-one-6-carboxylic acid ( 14 ), ranging from 11% to 59% inhibition of the biofilm. This pilot study contributes to the development of anti-QS compounds to overcome the clinical challenge of resistant bacteria strains.

A total of 82 strains of presumptive Aeromonas spp. were identified biochemically and genetically (16S rDNA-RFLP). The strains were isolated from 250 samples of frozen fish (Tilapia, Oreochromis niloticus niloticus) purchased in local markets in Mexico City. In the present study, we detected the presence of several genes encoding for putative virulence factors and phenotypic activities that may play an important role in bacterial infection. In addition, we studied the antimicrobial patterns of those strains. Molecular identification demonstrated that the prevalent species in frozen fish were Aeromonas salmonicida (67.5%) and Aeromonas bestiarum (20.9%), accounting for 88.3% of the isolates, while the other strains belonged to the species Aeromonas veronii (5.2%), Aeromonas encheleia (3.9%) and Aeromonas hydrophila (2.6%). Detection by polymerase chain reaction (PCR) of genes encoding putative virulence factors common in Aeromonas, such as aerolysin/hemolysin, lipases including the glycerophospholipid-cholesterol acyltransferase (GCAT), serine protease and DNases, revealed that they were all common in these strains. Our results showed that first generation quinolones and second and third generation cephalosporins were the drugs with the best antimicrobial effect against Aeromonas spp. In Mexico, there have been few studies on Aeromonas and its putative virulence factors. The present work therefore highlights an important incidence of Aeromonas spp., with virulence potential and antimicrobial resistance, isolated from frozen fish intended for human consumption in Mexico City.