Detection of Extended-Spectrum β-Lactamases (ESBL) Producing Enterobacteriaceae from Fish Trapped in the Lagoon Area of Bizerte, Tunisia

ESBL-producing Atlantibacter hermannii harboring a plasmid encoding IS26 up and down stream of blaCTX-M-27 ,blaLAP-2, and qnrS1 isolated from an edible river Anabas testudineus fish

Extended-spectrum β-lactamase-producing Atlantibacter hermannii was isolated from an edible river fish, Anabas testudineus, which was sold in a market located in Vietnam. The genome sequence was obtained by using next-generation sequencing, which involved Oxford Nanopore and Illumina technologies. The 92 kb plasmid encodes the gene blaCTX-M-27.

Prevalence and Characterization of Extended-Spectrum β-Lactamase- and Carbapenemase-Producing Enterobacterales from Tunisian Seafood

Aquaculture is a rapidly expanding sector in which it is important to monitor the occurrence of multi-drug resistant (MDR) bacteria. The presence of extended-spectrum β-lactamase (ESBL-) or carbapenemase-producing Enterobacterales is a commonly used indicator of the resistance burden in a given sector. In this study, 641 pieces of farmed fish (sea bream and sea bass), as well as 1075 Mediterranean clams, were analyzed. All ESBL- and carbapenemase-producing Enterobacterales collected were whole-genome sequenced. The proportion of ESBL-producing Enterobacterales was 1.4% in fish and 1.6% in clams, carried by Escherichia coli (n = 23) and Klebsiella pneumoniae (n = 4). The ESBL phenotype was exclusively due to the presence of bla_CTX-M genes, the most frequent one being bla_CTX-M-15. The bla_CTX-M-1 gene was also identified in six E. coli, among which four were carried by IncI1/pST3 plasmids, possibly betraying an animal origin. Carbapenemases were absent in fish but identified in two K. pneumoniae isolates from clams (bla_NDM-1 and bla_OXA-48). Several sequence types (STs) identified were associated with human MDR clones such as E. coli ST131 and ST617, or K. pneumoniae ST307 and ST147. Our results might indicate that bacteria from hospital or farm effluents can reach the open sea and contaminate seafood and fish that are living or raised nearby. Therefore, monitoring the quality of water discharged to the sea and the presence of MDR bacteria in seafood is mandatory to ensure the quality of fishery products.

Hiding in plain sight - Wildlife as a neglected reservoir and pathway for the spread of antimicrobial resistance: A narrative review

Antimicrobial resistance represents a global health problem, with infections due to pathogenic antimicrobial resistant bacteria (ARB) predicted to be the most frequent cause of human mortality by 2050. The phenomenon of antimicrobial resistance has spread to and across all ecological niches, and particularly in livestock used for food production with antimicrobials consumed in high volumes. Similarly, hospitals and other healthcare facilities are recognized as significant “hotspots” of ARB and antimicrobial resistance genes (ARGs); however, over the past decade, new and previously overlooked ecological niches are emerging as hidden reservoirs of ARB/ARGs. Increasingly extensive and intensive industrial activities, degradation of natural environments, burgeoning food requirements, urbanization, and global climatic change have all dramatically affected the evolution and proliferation of ARB/ARGs, which now stand at extremely concerning ecological levels. While antimicrobial resistant bacteria and genes as they originate and emanate from livestock and human hosts have been extensively studied over the past 30 years, numerous ecological niches have received considerably less attention. In the current descriptive review, the authors have sought to highlight the importance of wildlife as sources/reservoirs, pathways and receptors of ARB/ARGs in the environment, thus paving the way for future primary research in these areas.

Pathological, Immunological, and Hematological Parameters Associated with Experimental Infection of Citrobacter Freundii in Rabbits

Citrobacter freundii is one of the most important nosocomial opportunistic pathogens, which causes sepsis, as well as different gross and histopathological lesions in various internal organs in humans and animals, especially dogs and fish. This study aimed to investigate the hematological parameters, immunological responses, and pathological effects of the infection induced by the virulent strain of C. freundii on rabbits. A total of 42 rabbits (local breed; male and female), with a mean weight of 1.5-2 kg, were housed under controlled environmental conditions (20±2°C, 14:10 h light: dark cycle) and allowed ad libitum access to food and water. After two weeks of adaption, the rabbits were divided randomly into three groups of 14 animals per group. Group one (G1) received 3×10⁸ CFU/ml of the virulent isolate (intraperitoneally [IP]) of C. freundii. Group two (G2) was injected subcutaneously (SC) with 3×10⁸ CFU/ml of the virulent strain of C. freundii, while group three was IP injected with phosphate buffer saline and considered a negative control group. Results showed the variable gross pathological effects which included hemorrhage, edema, and congestion of visceral organs. Furthermore, the microscopic lesions showed pneumonia due to inflammatory cells infiltration, mainly neutrophils, macrophages, plasmacytes, and lymphocytes, severe interstitial and intra-alveolar edema, extensive pulmonary hemorrhage, emphysema, and atelectasis. The recorded data from the liver samples revealed hepatitis which was characterized by perivascular and periportal leukocyte cuffing, marked centrilobular with periportal necrosis, extensive hepatic edema, and periportal edema in addition to extensive fibrosis in interlobular septa and periportal fibrosis with severe interstitial hemorrhage. In the kidneys, there were severe renal edema, mixed inflammatory exudation, mainly neutrophils, macrophages, plasmacytes, lymphocytes, fibroblast infiltration in renal parenchyma and renal cortex, extensive renal hemorrhage, edema, as well as fibrosis and severe renal tubular necrosis. In addition, enteritis appeared in the intestine with mucosal edema, especially in lamina propria; moreover, necrosis of entire villi, epithelial necrosis, mucosal and submucosal hemorrhage, and fibrosis were observed. The present study revealed a significant increase in total leukocytes count and the concentration of TNF-α in the infected groups. To the best of the authors' knowledge, this study is considered the first attempt aimed to detect the pathological effects of C. freundii on visceral organs in rabbits. It is concluded that this bacterium could induce a significant pathological, hematological, and immunological changes in the infected animals.

Genomic, Morphological and Functional Characterization of Virulent Bacteriophage IME-JL8 Targeting Citrobacter freundii

Citrobacter freundii refers to a fish pathogen extensively reported to be able to cause injury and high mortality. Phage therapy is considered a process to alternatively control bacterial infections and contaminations. In the present study, the isolation of a virulent bacteriophage IME-JL8 isolated from sewage was presented, and such bacteriophage was characterized to be able to infect Citrobacter freundii specifically. Phage IME-JL8 has been classified as the member of the Siphoviridae family, which exhibits the latent period of 30–40 min. The pH and thermal stability of phage IME-JL8 demonstrated that this bacteriophage achieved a pH range of 4–10 as well as a temperature range of 4, 25, and 37°C. As revealed from the results of whole genomic sequence analysis, IME-JL8 covers a double-stranded genome of 49,838 bp (exhibiting 47.96% G+C content), with 80 putative coding sequences contained. No bacterial virulence- or lysogenesis-related ORF was identified in the IME-JL8 genome, so it could be applicable to phage therapy. As indicated by the in vitro experiments, phage IME-JL8 is capable of effectively removing bacteria (the colony count decreased by 6.8 log units at 20 min), and biofilm can be formed in 24 h. According to the in vivo experiments, administrating IME-JL8 (1 × 10⁷ PFU) was demonstrated to effectively protect the fish exhibiting a double median lethal dose (2 × 10⁹ CFU/carp). Moreover, the phage treatment led to the decline of pro-inflammatory cytokines in carp with lethal infections. IME-JL8 was reported to induce efficient lysis of Citrobacter freundii both in vitro and in vivo, thereby demonstrating its potential as an alternative treatment strategy for infections attributed to Citrobacter freundii.