Antibiotic Resistance of Diverse Bacteria from Aquaculture in Borneo

Isolation, identification and characterisation of Pseudomonas koreensis CM-01 isolated from diseased Malaysian mahseer (Tor tambroides)

Pseudomonas species are one of the most threatening fish pathogens which reside a wide range of environments. In this study, the dominant bacteria were isolated from diseased Malaysian mahseer (Tor tambroides) and tentatively named CM-01. It was identified as Pseudomonas koreensis based on its biochemical, morphological, genetic and physiological information. Its pathogenicity was found to be correlated with twelve virulence genes identified including iron uptake, protease, acylhomoserine lactone synthase gacS/gacA component regulation system, type IV secretion system, hydrogen cyanide production, exolysin, alginate biosynthesis, flagella and pili. The median lethal dose (LD50) for the CM-01 isolate on Malaysian mahseer was documented at 5.01 × 107 CFU/mL. The experimental infection revealed that CM-01 led to significant histological lesions in the fish, ultimately resulting in death. These lesions comprise necrosis, tissue thickening and aggregation. Drug sensitivity tests had shown its susceptibility to beta-lactam combination agents and further suggest its drug of choice. Its growing features had shown its growth at optimal temperature and pH. To the best of our knowledge, this is the first report of P. koreensis linked to diseased T. tambroides. STATEMENT OF RELEVANCE: In this research, a novel strain of Pseudomonas koreensis, CM-01 was isolated from diseased T. tambroides for the first time. The antimicrobial susceptibility, pathogenicity, virulence genes and growth characteristics of CM-01 were studied. These findings established a scientific foundation for the recognition of P. koreensis and the management of fish infections caused by this pathogen.

Dynamics of efflux pumps in antimicrobial resistance, persistence, and community living of Vibrionaceae

The marine bacteria of the Vibrionaceae family are significant from the point of view of their role in the marine geochemical cycle, as well as symbionts and opportunistic pathogens of aquatic animals and humans. The well-known pathogens of this group, Vibrio cholerae, V. parahaemolyticus, and V. vulnificus, are responsible for significant morbidity and mortality associated with a range of infections from gastroenteritis to bacteremia acquired through the consumption of raw or undercooked seafood and exposure to seawater containing these pathogens. Although generally regarded as susceptible to commonly employed antibiotics, the antimicrobial resistance of Vibrio spp. has been on the rise in the last two decades, which has raised concern about future infections by these bacteria becoming increasingly challenging to treat. Diverse mechanisms of antimicrobial resistance have been discovered in pathogenic vibrios, the most important being the membrane efflux pumps, which contribute to antimicrobial resistance and their virulence, environmental fitness, and persistence through biofilm formation and quorum sensing. In this review, we discuss the evolution of antimicrobial resistance in pathogenic vibrios and some of the well-characterized efflux pumps' contributions to the physiology of antimicrobial resistance, host and environment survival, and their pathogenicity.

Characterization and biocontrol efficacy of lytic phage (KPP-1) that infects multidrug resistant Klebsiella variicola

Klebsiella variicola strain was identified from a natural water stream. Novel phage (KPP-1) infecting K. variicola was isolated and characterized. The biocontrol efficacy of KPP-1 against K. variicola-infected adult zebrafish was also investigated. The host K. variicola strain was resistant to six of the antibiotics tested and comprised the virulence genes kfuBC, fim, ureA, and Wza-Wzb-Wzccps. Morphological analysis by transmission electron microscopy revealed that KPP-1 has icosahedron head and tail structures. The latent period and burst size of KPP-1 were 20 min and 88 PFU per infected cell, respectively, at a multiplicity of infection of 0.1. KPP-1 was stable over a broad pH range (3-11), temperature (4-50 °C), and salinity (0.1-3%). KPP-1 inhibits the growth of K. variicola in vitro and in vivo. In the zebrafish infection model, treatment with KPP-1-infected K. variicola demonstrated 56% of cumulative survival. This suggests the possibility of developing KPP-1 as a potential biocontrol agent against multidrug-resistant K. variicola that belongs to the K. pneumoniae complex.

Prevalence and antimicrobial resistance profiles of Vibrio spp. and Enterococcus spp. in retail shrimp in Northern California

Shrimp is one of the most consumed seafood products globally. Antimicrobial drugs play an integral role in disease mitigation in aquaculture settings, but their prevalent use raises public health concerns on the emergence and spread of antimicrobial resistant microorganisms. Vibrio spp., as the most common causative agents of seafood-borne infections in humans, and Enterococcus spp., as an indicator organism, are focal bacteria of interest for the monitoring of antimicrobial resistance (AMR) in seafood. In this study, 400 samples of retail shrimp were collected from randomly selected grocery stores in the Greater Sacramento, California, area between September 2019 and June 2020. The prevalence of Vibrio spp. and Enterococcus spp. was 60.25% (241/400) and 89.75% (359/400), respectively. Subsamples of Vibrio (n = 110) and Enterococcus (n = 110) isolates were subjected to antimicrobial susceptibility testing (AST). Vibrio isolates had high phenotypic resistance to ampicillin (52/110, 47.27%) and cefoxitin (39/110, 35.45%). Enterococcus were most frequently resistant to lincomycin (106/110, 96.36%), quinupristin-dalfopristin (96/110, 87.27%), ciprofloxacin (93/110, 84.55%), linezolid (86/110, 78.18%), and erythromycin (58/110, 52.73%). For both Vibrio and Enterococcus, no significant associations were observed between multidrug resistance (MDR, resistance to ≥3 drug classes) in isolates from farm raised and wild caught shrimp (p > 0.05) and in isolates of domestic and imported origin (p > 0.05). Whole genome sequencing (WGS) of a subset of Vibrio isolates (n = 42) speciated isolates as primarily V. metschnikovii (24/42; 57.14%) and V. parahaemolyticus (12/42; 28.57%), and detected 27 unique antimicrobial resistance genes (ARGs) across these isolates, most commonly qnrVC6 (19.05%, 8/42), dfrA31 (11.90%, 5/42), dfrA6 (9.5%, 4/42), qnrVC1 (9.5%, 4/42). Additionally, WGS predicted phenotypic resistance in Vibrio isolates with an overall sensitivity of 11.54% and specificity of 96.05%. This study provides insights on the prevalence and distribution of AMR in Vibrio spp. and Enterococcus spp. from retail shrimp in California which are important for food safety and public health and exemplifies the value of surveillance in monitoring the spread of AMR and its genetic determinants.

Whole-Genome Sequencing of Pseudomonas koreensis Isolated from Diseased Tor tambroides

Unlike environmental P. koreensis isolated from soil, which has been studied extensively for its role in promoting plant growth, pathogenic P. koreensis isolated from fish has been rarely reported. Therefore, we investigated and isolated the possible pathogen that is responsible for the diseased state of Tor tambroides. Herein, we reported the morphological and biochemical characteristics, as well as whole-genome sequences of a newly identified P. koreensis strain. We assembled a high-quality draft genome of P. koreensis CM-01 with a contig N50 value of 233,601 bp and 99.5% BUSCO completeness. The genome assembly of P. koreensis CM-01 is consists of 6,171,880 bp with a G+C content of 60.5%. Annotation of the genome identified 5538 protein-coding genes, 3 rRNA genes, 54 tRNAs, and no plasmids were found. Besides these, 39 interspersed repeat and 141 tandem repeat sequences, 6 prophages, 51 genomic islands, 94 insertion sequences, 4 clustered regularly interspaced short palindromic repeats, 5 antibiotic-resistant genes, and 150 virulence genes were also predicted in the P. koreensis CM-01 genome. Culture-based approach showed that CM-01 strain exhibited resistance against ampicillin, aztreonam, clindamycin, and cefoxitin with a calculated multiple antibiotic resistance (MAR) index value of 0.4. In addition, the assembled CM-01 genome was successfully annotated against the Cluster of Orthologous Groups of proteins database, Gene Ontology database, and Kyoto Encyclopedia of Genes and Genome pathway database. A comparative analysis of CM-01 with three representative strains of P. koreensis revealed that 92% of orthologous clusters were conserved among these four genomes, and only the CM-01 strain possesses unique elements related to pathogenicity and virulence. This study provides fundamental phenotypic and genomic information for the newly identified P. koreensis strain.

Antimicrobial peptides derived from microalgae for combating antibiotic resistance: Current status and prospects

Microalgae are photosynthetic cell factories that produce a spectrum of bioactive compounds extensively used for various applications. Owing to the increase in antibiotic resistance among microbial pathogens, there is a significant thrust for identifying new treatment strategies, and antimicrobial peptides (AMPs) generation is one such method. These AMPs have multiple roles and are active against bacteria, fungi, and viruses. Such peptides synthesized in microalgae have a significant role in medical application, managing aquaculture-associated diseases, and the food industry. To increase their effectiveness and novel peptides, genetically modified microalgae are used as cell factories. With the advancement of new technologies like the CRISPR-Cas system, new avenues are opened for developing novel AMPs using microalgae. This review gives us insight into the various AMPs produced by microalgae and multiple technologies involved in creating such therapeutically essential molecules.

Prevalence, Antibiotics Resistance and Plasmid Profiling of Vibrio spp. Isolated from Cultured Shrimp in Peninsular Malaysia

Vibrio is the most common bacterium associated with diseases in crustaceans. Outbreaks of vibriosis pose a serious threat to shrimp production. Therefore, antibiotics are commonly used as preventative and therapeutic measures. Unfortunately, improper use of antibiotics leads to antibiotic resistance. Nevertheless, information on the occurrence of Vibrio spp. and antibiotic use in shrimp, particularly in Malaysia, is minimal. This study aimed to provide information on the occurrence of Vibrio spp., its status of antibiotic resistance and the plasmid profiles of Vibrio spp. isolated from cultured shrimp in Peninsular Malaysia. Shrimp were sampled from seven farms that were located in different geographical regions of Peninsular Malaysia. According to the observations, 85% of the shrimp were healthy, whereas 15% were unhealthy. Subsequently, 225 presumptive Vibrio isolates were subjected to biochemical tests and molecular detection using the pyrH gene. The isolates were also tested for antibiotic susceptibility against 16 antibiotics and were subjected to plasmid profiling. Eventually, 13 different Vibrio spp. were successfully isolated and characterized using the pyrH gene. They were the following: V. parahaemolyticus (55%), V. communis (9%), V. campbellii (8%), V. owensii (7%), V. rotiferianus (5%), Vibrio spp. (4%), V. alginolyticus (3%), V. brasiliensis (2%), V. natriegens (2%), V. xuii (1%), V. harveyi (1%), V. hepatarius (0.4%) and P. damselae (3%). Antibiotic susceptibility profiles revealed that all isolates were resistant to penicillin G (100%), but susceptible to norfloxacin (96%). Furthermore, 16% of the isolates revealed MAR of less than 0.2, while 84% were greater than 0.2. A total of 125 isolates harbored plasmids with molecular weights between 1.0 and above 10 kb, detected among the resistant isolates. The resistant isolates were mediated by both chromosomal and plasmid factors. These findings support the use of surveillance data on the emerging patterns of antimicrobial-resistance and plasmid profiles of Vibrio spp. in shrimp farms. The findings from this study can be used to develop a better disease management strategy for shrimp farming.

Applicability of bio-synthesized nanoparticles in fungal secondary metabolites products and plant extracts for eliminating antibiotic-resistant bacteria risks in non-clinical environments

The abundance of antibiotic-resistant bacteria in the prawn pond effluents can substantially impact the natural environment. The settlement ponds, which are the most common treatment method for farms wastewater, might effectively reduce the suspended solids and organic matter. However, the method is insufficient for bacterial inactivation. The current paper seeks to highlight the environmental issue associated with the distribution of antibiotic resistant bacteria (ARB) from prawn farm wastewater and their impact on the microbial complex community in the surface water which receiving these wastes. The inactivation of antibiotic-resistant bacteria in prawn wastewater is strongly recommended because the presence of antibiotic-resistant bacteria in the environment causes water pollution and public health issues. The nanoparticles are more efficient for bacterial inactivation. They are widely accepted due to their high chemical and mechanical stability, broad spectrum of radiation absorption, high catalytic activity, and high antimicrobial activity. Many studies have examined the use of fungi or plants extract to synthesis zinc oxide nanoparticles (ZnO NPs). It is evident from recent papers in the literature that green synthesized ZnO NPs from microbes and plant extracts are non-toxic and effective. ZnO NPs inactivate the bacterial cells as a function for releasing reactive oxygen species (ROS) and zinc ions. The inactivation of antibiotic-resistant bacteria tends to be more than 90% which exhibit strong antimicrobial behavior against bacterial species.

Multi-drug resistance, integron and transposon-mediated gene transfer in heterotrophic bacteria from Penaeus vannamei and its culture environment

Multi-drug resistance (MDR) in bacteria is regarded as an emerging pollutant in different food production avenues including aquaculture. One hundred and sixty out of 2304 bacterial isolates from shrimp farm samples (n = 192) of Andhra Pradesh, India, were MDR. Based on biochemical identification and 16S rRNA sequencing, they were grouped into 35 bacterial species with the predominance of Vibrio parahaemolyticus (12.5%). The MDR isolates showed highest resistance toward oxytetracycline (89%) with more than 0.2 MAR (multiple antibiotic resistance), demonstrates a high-risk source. The most prevalent antibiotic-resistance gene (ARG) and mobile genetic element (MGE) detected were tetA (47.5%) and int1 (46.2%), respectively. In conjugation experiments, overall transfer frequency was found to be in the range of 1.1 × 10^-9 to 1.8 × 10^-3 with the transconjugants harbouring ARGs and MGEs. This study exposed the wide distribution of MDR bacteria in shrimp and its environment, which can further aggravate the already raised concerns of antibiotic residues in the absence of proper mitigation measures.

Marine fungal metabolites as a source of drug leads against aquatic pathogens

Aquatic pathogens, including Vibrio, Edwardsiella, Pseudomonas, and Aeromonas, which could result in bacterial diseases to aquaculture, have seriously threatened the world aquaculture production. Marine-derived fungi, which could produce novel secondary metabolites with significant antibacterial activity, may be an important source for finding effective agents against aquatic pathogens. In this review, a systematically overview of the harm of several aquatic pathogens, and 134 antibacterial secondary metabolites against aquatic pathogens from 13 genera of marine-derived fungi, were summarized and concluded. The aim of this review is to find out the relationships between activity and structural type, between bioactive compounds and their hosts, and so on. Altogether, 95 references published during 1997-2021 were cited. KEY POINTS: •Aquatic pathogens, which could result in bacterial diseases to aquaculture, were described. •Marine fungal metabolites with activities against aquatic pathogens were summarized. •The distributions of these bioactive marine fungal metabolites were analyzed.

Systematic review and meta-analysis of environmental Vibrio species - antibiotic resistance

Adequate comprehension of the genomics of microbial resistance to an antimicrobial agent will advance knowledge on the management of associated pathologies and public health safety. However, continued emergences and reemergence of pathogens, including Vibrio species, hallmarks a potential knowledge gap. A clear understanding of the process and forecast of the next trend should be in place to nip in the bud, microbial acquisition of resistance to antibiotics. Therefore, this two-decade (1 January 2000 to 31 December 2019) systematic review and meta-analytical study articulated the prevalence and incidence of antibiotics resistance genes in Vibrio species isolated from environmental samples. Articles from the Web of Science and PubMed electronic databases was engaged. Heterogeneity of the data and bias were analyzed with random effect model meta-analysis and funnel plot. A total of 1920 Vibrio sp. were reported by the ten selected articles included in this study; out of which 32.39% of identified isolates displayed antimicrobial resistance and associated genes. The distribution of antibiotics resistance genes in Vibrio sp., reported within six countries was 21% tetracycline (tet), and 20% sulphonamide (sul) and β-lactamase (bla) respectively. The quinolone, tetracycline and sulfonamide resistance genes showed 32.97% (95% CI 0.18–0.53) prevalence while chloramphenicol, macrolides and aminoglycoside resistance genes are expressed in percentages as 28.67% (95% CI 0.15–0.47) and β-lactamase resistance genes 27.93% (95% CI 0.11–0.56) respectively. The Vibrio antibiotics resistance genes (V-ARG) distribution depicts no regular trend or pattern from the analyzed data. Consequently, more studies would be required to articulate the structure of cohesion in the distribution of the resistance determinants in microbes.

Antibiotics, antibiotic-resistant bacteria, and resistance genes in aquaculture: risks, current concern, and future thinking

Aquaculture is remarkably one of the most promising industries among the food-producing industries in the world. Aquaculture production as well as fish consumption per capita have been dramatically increasing over the past two decades. Shifting of culture method from semi-intensive to intensive technique and applying of antibiotics to control the disease outbreak are the major factors for the increasing trend of aquaculture production. Antibiotics are usually present at subtherapeutic levels in the aquaculture environment, which increases the selective pressure to the resistant bacteria and stimulates resistant gene transfer in the aquatic environment. It is now widely documented that antibiotic resistance genes and resistant bacteria are transported from the aquatic environment to the terrestrial environment and may pose adverse effects on human and animal health. However, data related to antibiotic usage and bacterial resistance in aquaculture is very limited or even absent in major aquaculture-producing countries. In particular, residual levels of antibiotics in fish and shellfish are not well documented. Recently, some of the countries have already decided the maximum residue levels (MRLs) of antibiotics in fish muscle or skin; however, many antibiotics are yet not to be decided. Therefore, an urgent universal effort needs to be taken to monitor antibiotic concentration and resistant bacteria particularly multiple antibiotic-resistant bacteria and to assess the associated risks in aquaculture. Finally, we suggest to take an initiative to make a uniform antibiotic registration process, to establish the MRLs for fish/shrimp and to ensure the use of only aquaculture antibiotics in fish and shellfish farming globally.

Tropical Cellulolytic Bacteria: Potential Utilization of Sugarcane Bagasse as Low-Cost Carbon Source in Aquaculture

Sugarcane bagasse (SB), as a major by-product of sugarcane, is one of the most abundant organic matter and characterized by cheap and easily available carbon source in Hainan Island, China. The objective of this study was to isolate tropical cellulolytic bacteria from Hainan Island and demonstrate their prospects of utilization of SB as a low-cost carbon source to greatly reduce the cost of aquaculture. A total of 97 cellulolytic marine bacteria were isolated, of which, 58 cellulolytic marine bacteria displayed the hydrolysis capacity (HC) of more than 1, while 28 cellulolytic marine bacteria displayed more than 2. Of the 28 tropical cellulolytic bacterial strains with HC more than 2, Microbulbifer sp. CFW-C18 and Vibrio sp. MW-M19 exhibited excellent SB decomposition in a small-scale laboratory simulation of shrimp aquaculture, up to 75.31 and 74.35%, respectively, and both of them were safe for shrimps. Meanwhile, both of CFW-C18 and MW-M19 besides displaying low multiple antibiotic resistance (MAR) index, also increased the C/N ratio (CFW-C18: C/N ratio of 14.34; MW-M19: C/N ratio of 14.75) of the small-scale laboratory simulation of shrimp aquaculture by decreasing the nitrogen content after a supplement of SB for 15 days. More importantly, CFW-C18 and MW-M19 displayed a relatively low MAR index, 0.47 and 0.1, respectively, especially MW-M19, with the lowest MAR index (0.1), which was resistant to only three antibiotics, streptomycin, amikacin, and levofloxacin, indicating that this strain was safe and non-drug resistance for further use. Overall, tropical cellulolytic bacteria isolated from Hainan Island, especially CFW-C18 and MW-M19, will provide the proficient candidates as probiotics for further construction of the recirculating aquaculture system based on the supplement of low-cost external carbon source—SB.

Occurrence of Virulence and Antimicrobial Resistance Determinants in Vibrio harveyi Isolated from Marine Food Fish Cultured in Korea

Vibrio harveyi is a significant cause of infection in both marine animals and humans. It has been reported frequently in seafood-borne infections worldwide. This study was conducted to determine the potential health impact of the V. harveyi isolated from marine food fish cultured in Korea concerning their virulence and antimicrobial resistance. A total of 49 V. harveyi samples were isolated by biochemical tests and multiplex PCR. Phenotypic detection of virulence factors resulted DNase activity (81.63%), hemolysis (α = 75.51% and β = 12.25), gelatinase activity (71.43%), protease production (71.43%), phospholipase activity (65.31%), and lipase production (34.69%). Virulence genes, including VPI, tlh, tdh, toxR, VAC, and ctxAB, were detected in 57.14%, 44.90%, 36.73%, 22.45%, 12.24%, and 8.16% of the isolates, respectively. Resistance to ampicillin (77.55%), oxacillin (69.39%), nalidixic acid (53.06%), amoxicillin (46.94%), oxytetracycline (46.94%), colistin sulfate (34.69%), fosfomycin (34.69%), chloramphenicol (32.65%), streptomycin (32.65%), cephalothin (28.57%), oxytetracycline (26.53%), ceftriaxone (20.41%), erythromycin (14.29%), and cefoxitin (12.24%) was detected in disc diffusion assay. Most of the isolates were classified as multidrug resistant as they scored multiple antimicrobial resistance index ≥0.2. Furthermore, antimicrobial resistance genes tetB, qnrA, intI1 (Class 1 integron integrase), aac(6')-Ib, bla_SHV, bla_CTX-M, strA-strB, tetA, aphAI-IAB, qnrC, qnrS, and bla_TEM were found in 81.63%, 67.35%, 61.22%, 46.94%, 44.90%, 44.90%, 36.73%, 18.37%, 10.20%, 10.20%, 8.16% and 6.12% of the isolates, respectively. In conclusion, the development of antimicrobial resistance among V. harveyi will ultimately reduce the efficacy of antimicrobials used for treating and can favor the development of more virulent V. harveyi strains.

An update on the ornamental fish industry in Malaysia: Aeromonas hydrophila-associated disease and its treatment control

Malaysia is the world’s major producer and exporter of ornamental fish, contributing 9% to the global trade and taking the second position after Singapore. Because of their artistic appeal and tremendous commercial value for international trade, ornamental fish recently gain rapid importance for foreign exchange and as a source of employment. While ornamental fish production is growing, there is an increase in infectious diseases, resulting in high fish mortality with significant economic loss. Bacterial disease is a serious problem for ornamental fish industry. Bacterial species surveillance in diseased freshwater ornamental fish from an aquarium shop reveals that Aeromonas hydrophila is the most dominant bacteria isolated. Consequently, Malaysia is stepping up its efforts by implementing the Economic Transformation Program and other biosecurity steps to address the aquaculture issues and encourage the regrowth of the ornamental fish market. Chemotherapeutic medications, phytobiotics, probiotics, yeast extracts, vaccines, and disinfectants can be used in controlling bacteria. Further studies should be done to find new antibacterial agents from natural sources to combat bacterial fish diseases and reduce fish mortality rate in sustainable aquaculture farms. This review summarizes the literature on ornamental fish industries and aquaculture production in relation to A. hydrophila-associated diseases and ornamental fish health management in Malaysia.

Virulence properties and pathogenicity of multidrug-resistant Vibrio harveyi associated with luminescent vibriosis in pacific white shrimp, Penaeus vannamei

Global high demand for pacific white shrimp Penaeus vannamei has led to intensified cultivation and a wide range of disease problems, including bacterial diseases due to vibrios. Three presumptive luminescent Vibrio harveyi strains (Vh5, Vh8 and Vh10) were isolated from the hepatopancreas (Vh5) and haemolymph (Vh8 and Vh10) of diseased growout pacific white shrimp from a farm in Setiu, Terengganu, Malaysia, using Vibrio harveyi agar (VHA) differential medium. All three strains were identified as V. harveyi by biochemical characteristics. 16S rRNA gene-based phylogenetic analyses by neighbour-joining, maximum likelihood and maximum parsimony methods showed all three strains in the V. harveyi cluster. All three strains were β-haemolytic and positive for motility, biofilm formation and extracellular products (caseinase, gelatinase, lipase, DNase, amylase and chitinase). Vh10 was subjected to pathogenicity test in pacific white shrimp by immersion challenge and determined to have a LC₅₀ of 6.0 × 10⁸ CFU mL^-1 after 168 h of exposure. Antibiotic susceptibility tests showed that all strains were resistant to oxytetracycline (OXT30), oleandomycin (OL15), amoxicillin (AML25), ampicillin (AMP10) and colistin sulphate (CT25) but sensitive to doxycycline (DO30), flumequine (UB30), oxolinic acid (OA2), chloramphenicol (C30), florfenicol (FFC30), nitrofurantoin (F5) and fosfomycin (FOS50). Each strain was also resistant to a slightly different combination of eight other antibiotics, with an overall multiple antibiotic resistance (MAR) index of 0.40, suggesting prior history of heavy exposure to the antibiotics. Vh10 infection resulted in pale or discoloured hepatopancreas, empty guts, reddening, necrosis and luminescence of uropods, as well as melanized lesions in tail muscle. Histopathological examination showed necrosis of intertubular connective tissue and tubule, sloughing of epithelial cells in hepatopancreatic tubule, haemocytic infiltration, massive vacuolation and loss of hepatopancreatic tubule structure.

Staphylococcus aureus in Intensive Pig Production in South Africa: Antibiotic Resistance, Virulence Determinants, and Clonality

Although Staphylococcus aureus is a major threat to the veterinary, agricultural, and public health sectors because of its zoonotic potential, studies on its molecular characterisation in intensive animal production are rare. We phenotypically and genotypically characterised antibiotic-resistant S. aureus in intensive pig production in South Africa, using the farm-to-fork approach. Samples (n = 461) were collected from the farm, transport vehicles, and the abattoir using the World Health Organisation on Integrated Surveillance of Antimicrobial Resistance (WHO-AGISAR) sampling protocol. Bacteria were isolated using selective media and identified using biochemical tests and polymerase chain reaction (PCR). Phenotypic resistance was determined using the disk diffusion method. Selected resistance and virulence genes were investigated using PCR. Clonality among the isolates was determined using the repetitive element sequence-PCR. In all, 333 presumptive staphylococcal isolates were obtained, with 141/333 (42.3%) identified as staphylococci biochemically. Ninety-seven (97; 68.8%) were confirmed as S. aureus using PCR, 52.6% of which were identified as methicillin-resistant S. aureus (MRSA) through the mecA gene. All the 97 S. aureus isolates (100%) were resistant to at least one of the antibiotics tested, with the highest resistance observed against erythromycin and clindamycin (84.50% each), and the lowest observed against amikacin (2.10%); 82.47% (80/97) were multidrug-resistant with an average multiple antibiotic resistance index of 0.50. Most of the phenotypically resistant isolates carried at least one of the corresponding resistance genes tested, ermC being the most detected. hla was the most detected virulence gene (38.14%) and etb was the least (1.03%). Genetic fingerprinting revealed diverse MRSA isolates along the farm-to-fork continuum, the major REP types consisting of isolates from different sources suggesting a potential transmission along the continuum. Resistance to antibiotics used as growth promoters was evidenced by the high prevalence of MDR isolates with elevated multiple antibiotic resistance indices >0.2, specifically at the farm, indicating exposure to high antibiotic use environments, necessitating antibiotic stewardship and proper infection control measures in pig husbandry and intensive pig production.

Phenotypic Antimicrobial Susceptibility of Escherichia coli from Raw Meats, Ready-to-Eat Meats, and Their Related Samples in One Health Context

Meat is an important food source that can provide a significant amount of protein for human development. The occurrence of bacteria that are resistant to antimicrobials in meat poses a public health risk. This study evaluated the occurrence and antimicrobial resistance of E. coli (Escherichia coli) isolated from raw meats, ready-to-eat (RTE) meats and their related samples in Ghana. E. coli was isolated using the USA-FDA Bacteriological Analytical Manual and phenotypic antimicrobial susceptibility test was performed by the disk diffusion method. Of the 200 examined meats and their related samples, 38% were positive for E. coli. Notably, E. coli was highest in raw beef (80%) and lowest in RTE pork (0%). The 45 E. coli isolates were resistant ≥ 50% to amoxicillin, trimethoprim and tetracycline. They were susceptible to azithromycin (87.1%), chloramphenicol (81.3%), imipenem (74.8%), gentamicin (72.0%) and ciprofloxacin (69.5%). A relatively high intermediate resistance of 33.0% was observed for ceftriaxone. E. coli from raw meats, RTE meats, hands of meat sellers and working tools showed some differences and similarities in their phenotypic antimicrobial resistance patterns. Half (51.1%) of the E. coli isolates exhibited multidrug resistance. The E. coli isolates showed twenty-two different resistant patterns, with a multiple antibiotic resistance index of 0.0 to 0.7. The resistant pattern amoxicillin (A, n = 6 isolates) and amoxicillin-trimethoprim (A-TM, n = 6 isolates) were the most common. This study documents that raw meats, RTE meats and their related samples in Ghana are potential sources of antimicrobial-resistant E. coli and pose a risk for the transfer of resistant bacteria to the food chain, environment and humans.

Molecular Detection of Antibiotic-Resistant Genes in Pseudomonas aeruginosa from Nonclinical Environment: Public Health Implications in Mthatha, Eastern Cape Province, South Africa

Evaluation of resistant profiles and detection of antimicrobial-resistant genes of bacterial pathogens in the nonclinical milieu is imperative to assess the probable risk of dissemination of resistant genes in the environment. This paper sought to identify antibiotic-resistant genes in Pseudomonas aeruginosa from nonclinical sources in Mthatha, Eastern Cape, and evaluate its public health implications. Samples collected from abattoir wastewater and aquatic environment were processed by membrane filtration and cultured on CHROMagarTM Pseudomonas medium. Species identification was performed by autoSCAN-4 (Dade Behring Inc., IL). Molecular characterization of the isolates was confirmed using real-time polymerase chain reaction (rPCR) and selected isolates were further screened for the possibility of harboring antimicrobial resistance genes. Fifty-one Pseudomonas species were recovered from abattoir wastewater and surface water samples, out of which thirty-six strains were Pseudomonas aeruginosa (70.6%). The P. aeruginosa isolates demonstrated resistance to aztreonam (86.1%), ceftazidime (63.9%), piperacillin (58.3%), cefepime (55.6%), imipenem (50%), piperacillin/tazobactam (47.2%), meropenem (41.7%), and levofloxacin (30.6%). Twenty out of thirty-six P. aeruginosa displayed multidrug resistance profiles and were classified as multidrug-resistant (MDR) (55.6%). Most of the bacterial isolates exhibited a high Multiple Antibiotic Resistance (MAR) Index ranging from 0.08 to 0.69 with a mean MAR index of 0.38. In the rPCR analysis of fifteen P. aeruginosa isolates, 14 isolates (93.3%) were detected harboring bla SHV, six isolates (40%) harbored bla TEM, and three isolates (20%) harbored bla CTX-M, being the least occurring ESBL. Results of the current study revealed that P. aeruginosa isolates recovered from nonclinical milieu are resistant to frontline clinically relevant antipseudomonal drugs. This is concerning as it poses a risk to the environment and constitutes a public health threat. Given the public health relevance, the paper recommends monitoring of multidrug-resistant pathogens in effluent environments.

Multiple Antibiotic Resistance-Coliform Bacteria in Some Selected Fish Farms of the Central Region of Ghana

This study aimed at assessing the quality of water and fishery products as well as the antibiotic resistance status of some selected fish farms of the Central Region of Ghana. Interview guides were administered to farmers to get data on farming practices and antibiotic use. Total coliform loads of catfish (Clarias gariepinus), tilapia (Oreochromis niloticus), and water samples were determined. Coliforms were identified through various biochemical assays, and their antibiotic resistance patterns were determined. Generally, the total coliform loads of water samples significantly surpassed those of fish samples (p < 0.05). The maximum and minimum antibiotic resistance percentages were recorded for ampicillin (96.83%) and gentamicin (6.35%), respectively. Although farmers stated that antibiotics were sparingly used, coliform bacteria isolated exhibited various antibiotic resistance patterns. Four out of six fish farms harboured some coliforms with multiple antibiotic resistance (MAR) indices above 0.2, an indication that these bacteria originated from potentially dangerous sources where antibiotics are regularly used.

Prevalence and Antimicrobial Resistance of Escherichia coli Isolated from Various Meat Types in the Tamale Metropolis of Ghana

Meats are important potential sources of foodborne pathogens including Escherichia coli. This study was conducted to determine the prevalence and antimicrobial resistance of Escherichia coli isolated from meats in the Tamale metropolis of Ghana. Isolation of Escherichia coli was done using the procedure according to the USA-FDA Bacteriological Analytical Manual. Antibiotic resistance patterns in the Escherichia coli isolates were determined by the Kirby-Bauer disk diffusion method against 8 antibiotics. The overall prevalence of Escherichia coli in the meat samples was 84.00% (189/225). Mutton (88.89%), guinea fowl (88.89%), beef (86.67%), local chicken (80.00%), and chevon (75.56%) were contaminated by Escherichia coli. The average coliform count was 4.22 cfu/cm² and was highest in guinea fowl (4.94 log cfu/cm²) and lowest in local chicken (3.23 log cfu/cm²). The Escherichia coli isolates were highly resistant to erythromycin (85.00%), tetracycline (73.33%), and ampicillin (71.67%). The multiple antibiotic resistance (MAR) index ranged from 0.13 to 1. The Escherichia coli isolates exhibited 23 antimicrobial resistance patterns with resistant pattern TeAmpE (tetracycline-ampicillin-erythromycin) being the most common. Multidrug resistance was 68.33% (41/60) among the Escherichia coli isolates. The results showed that Escherichia coli was commonly present in the various meat types and exhibited multidrug resistances, necessitating efficient antibiotic stewardship guidelines to streamline their use in the production industry.

Antimicrobial Resistance analysis of Pathogenic Bacteria Isolated from Freshwater Nile Tilapia (Oreochromis niloticus) Cultured in Kerala, India

Aquaculture of popular freshwater species, Nile tilapia (Oreochromis niloticus), accounts for around 71% of the total global tilapia production. Frequent use of antibiotics for treating bacterial infections in tilapia leads to the emergence of antimicrobial resistance. To mitigate the issue, proper evaluation methods and control strategies have to be implemented. This study was aimed to analyze the antimicrobial resistance of bacterial isolates from the infected Nile tilapia cultured in freshwater. The recovered isolates were identified as Pseudomonas entomophila, Edwardsiella tarda, Comamonas sp, Delftia tsuruhatensis, Aeromonas dhakensis, A. sobria, A. hydrophila, A. lacus, Plesiomonas shigelloides and Vogesella perlucida through phenotypic and genotypic analyses. Using Primer-E software, Shannon Wiener diversity index of the isolates was determined as H' (loge) = 2.58. Antibiotic susceptibility test of the recovered strains through disk diffusion using 47 antibiotics, showed an elevated resistance pattern for Aeromonas hydrophila, Pseudomonas entomophila and Comamonas with higher multiple antibiotic resistance indexes (MAR index > 0.3). The minimum inhibitory concentration of antibiotics was > 256 mcg/ml for most of the resistant isolates. Meanwhile, all the recovered isolates were susceptible to amikacin, aztreonam, kanamycin, cefalexin, cefotaxime, levofloxacin, norfloxacin, piperacillin, and polymyxin-B.

Diversity of antimicrobial-resistant pathogens from a freshwater ornamental fish farm

The indiscriminate use of antimicrobials in aquaculture results in antibiotic selection pressure and proliferation of antimicrobial resistant (AMR) bacteria. Frequent assessment of antimicrobial resistance in aquaculture environment is inevitable so as to reduce the passage of clinically important AMR from aquatic to other environment. The present study analysed the antimicrobial resistance of pathogens associated with diseased koi carp and goldfish from an ornamental fish farm. Phenotypic and genotypic characterization of the recovered isolates from both fishes revealed significant pathogens in aquaculture such as Aeromonas, Edwardsiella tarda, Acinetobacter, Lactococcus, Citrobacter, Enterobacter and Comamonas. Shannon-Wiener diversity of koi isolates (2·359) was found to be higher than that of goldfish (1·864). Antibiotic susceptibility testing using disc diffusion with 47 antibiotics revealed significant resistance pattern of Acinetobacter, Comamonas, Klebsiella and Enterobacter from goldfish and Edwardsiella, Aeromonas, Lactococcus, Enterobacter and Acinetobacter from koi with higher multiple antibiotic resistance indexes (>0·3). The minimum inhibitory concentration of antibiotics for the major resistant isolates was found to be very high with >256 μg. All the isolates were susceptible to amoxicillin, kanamycin, cefepime, cefexime, cefotaxime, ceftazidime, doripenem, ciprofloxacin and norfloxacin, recommending their successful application in the farm. SIGNIFICANCE AND IMPACT OF THE STUDY: Antimicrobial resistance is a major threat faced in aquaculture industry. The current study provides baseline information regarding the antibiotic resistance patterns of diverse pathogens recovered from ornamental koi carp and goldfish. The higher MAR index of pathogens and greater MIC of antibiotics for the resistant isolates highlighted the intense use of antibiotics in aquaculture farm. The potential of the pathogens to exhibit resistance even towards the new generation antibiotics remind the need of prudent use of antibiotics and continuous monitoring and surveillance programmes.

Genetic diversity and multiple antibiotic resistance index study of bacterial pathogen, Klebsiella pneumoniae strains isolated from diseased Indian major carps

Intensive fish farming systems have led to increase in disease incidence, due to higher stocking density, high organic matter levels, and poor quality of the aquatic environment. Diseased fish samples showing hemorrhages and reddish lesions were collected from different freshwater fish farms located at three different districts of West Bengal, India (Burdwan, North 24 Parganas, and Nadia). The present study was conducted to evaluate the genetic diversity of ten different Klebsiella pneumoniae strains isolated from different infected freshwater fish samples based on 16S rRNA gene sequence analysis. Primarily, Klebsiella-specific media was used for the isolation and characterization of Klebsiella pneumoniae. Further, through a biochemical test, all the strains were confirmed as K. pneumoniae. PCR analysis of 16S-23S internal transcribed spacer (PCR ribotyping) was carried out to study the species variation within different Klebsiella pneumoniae isolates. For all the isolates, a conserved PCR ribotype pattern was observed while differing from other bacterial species. Phylogenetic study showed the high degree of homology with diverse source of other strains. The multiple antibiotic resistance (MAR) values of the present study for the isolates were found to be 0.468. MAR value above 0.2 indicates that the source of isolation was highly contaminated with antibiotics. Based on the 16S rRNA gene sequence analysis, the present study revealed the genetic diversity of Klebsiella pneumoniae isolated from the different diseased fish farms of West Bengal. All the strains were found to be hypermucoviscous and multidrug-resistant, thus making it pathogenic towards the host organisms. Further, the study revealed a high prevalence of K. pneumoniae in aquaculture farms, representing a risk towards successful aquaculture.

The effects of marine farm-scale sequentially integrated multi-trophic aquaculture systems on microbial community composition, prevalence of sulfonamide-resistant bacteria and sulfonamide resistance gene sul1

Aquaculture, one of the most important food production practices worldwide, faces serious challenges of mitigating the detrimental impacts of intensive farming on the environment and increased prevalence of antibiotic resistance. To develop an environment-friendly aquaculture system, a land-based and farm-scale sequentially integrated multi-trophic aquaculture (IMTA) system was established for farming Chanos chanos in southwestern Taiwan. In this system, fishes are cultured in combination with organic extractive shellfish and inorganic extractive seaweed. This study aimed to evaluate the prevalence of sulfonamide-resistant bacteria, microbial community structure, and occurrence of sulfonamide resistance genes in the IMTA and traditional aquaculture systems. Water and sediment samples were collected before raising and after harvesting C. chanos. Our results showed that the occurrence of sulfonamide-resistant phenotypes in the IMTA system was comparable with that in influent seawater, while the traditional system exhibited a high sulfonamide resistance rate. Additionally, the traditional system resulted in a deviation of the bacterial community structure from that of seawater. In the water samples from the IMTA system and influent seawater, Proteobacteria and Bacteroidetes were the two dominant phyla, representing approximately 75% and 15% of the community, respectively. In the traditional system, Actinobacteria, constituting 39% of the community, was the dominant bacterial phylum. Thirty-one sulfonamide-resistant bacterial species were isolated. In conclusion, a sequentially IMTA system showed superior ability to maintain the prevalence of antibiotic resistance and the integrity of the bacterial community structure compared to the traditional farming system, representing a potentially valuable aquaculture system for preserving the sustainability of the marine environment.

In vitro resistance of Enterobacter cloacae isolated from fresh seafood to colistin

INTRODUCTION

Enterobacter cloacae is a clinically important bacterium from the Enterobacteriaceae family. This study evaluated resistance of E. cloacae strains from fish (n=14) and shrimp (n=9) to colistin.

METHODS

Biochemical identification and antimicrobial susceptibility tests were carried out in an automated Vitek®2 instrument.

RESULTS

Colistin resistance was observed in 21.4% and 66.7% of the strains from fish and shrimp, respectively. We observed minimum inhibitory concentrations of ≥16 mg/L and ≤5 mg/L in 8 and 15 of all strains, respectively.

CONCLUSIONS

Fish and shrimp can carry drug-resistant enterobacteria, which can be of clinical interest.

Protective effect of apple mangrove Sonneratia caseolaris extract in Edwardsiella tarda-infected African catfish, Clarias gariepinus

Outbreaks of edwardsiellosis have severe impact on the aquaculture production of African catfish Clarias gariepinus. In this study, feed supplemented with apple mangrove Sonneratia caseolaris extract was evaluated for its protective effect against Edwardsiella tarda infection in African catfish. Results showed an increase in growth performance and higher survival rate in the treatment groups in a dose dependent manner. Haematological analyses showed an increase in white blood cell count in the treatment groups. Histopathological analysis revealed degenerative changes and regeneration of liver tissue architecture in both the control and treatment groups. However, the presence of inflammatory cells was found exclusively in the kidney of T3 treatment group that was supplemented with the highest dose of extract at 3.17 mg/ml, which inferred the activation of immune response in the fish. Contrast to the deteriorative alteration observed in the kidney of the control group due to E. tarda infection, treatment group exhibited tissue regeneration and well-defined kidney tissue architecture at 3 dpi. Taken together, these results demonstrated that supplementation with the methanol extract of S. caseolaris possesses protective effect in African catfish against the infection of E. tarda.

Identification of Peptides in Flowers of Sambucus nigra with Antimicrobial Activity against Aquaculture Pathogens

The elder (Sambucus spp.) tree has a number of uses in traditional medicine. Previous studies have demonstrated the antimicrobial properties of elderberry liquid extract against human pathogenic bacteria and also influenza viruses. These properties have been mainly attributed to phenolic compounds. However, other plant defense molecules, such as antimicrobial peptides (AMPs), may be present. Here, we studied peptide extracts from flowers of Sambucus nigra L. The mass spectrometry analyses determined peptides of 3 to 3.6 kDa, among them, cysteine-rich peptides were identified with antimicrobial activity against various Gram-negative bacteria, including recurrent pathogens of Chilean aquaculture. In addition, membrane blebbing on the bacterial surface after exposure to the cyclotide was visualized by SEM microscopy and SYTOX Green permeabilization assay showed the ability to disrupt the bacterial membrane. We postulate that these peptides exert their action by destroying the bacterial membrane.

Chemical Synthesis and Functional Analysis of VarvA Cyclotide

Cyclotides are circular peptides found in various plant families. A cyclized backbone, together with multiple disulfide bonds, confers the peptides’ exceptional stability against protease digestion and thermal denaturation. In addition, the features of these antimicrobial molecules make them suitable for use in animal farming, such as aquaculture. Fmoc solid phase peptide synthesis on 2-chlorotrityl chlorine (CTC) resin using the “tea-bag” approach was conducted to generate the VarvA cyclotide identified previously from Viola arvensis. MALDI-TOF mass spectrometry determined the correct peptide amino acid sequence and the cyclization sites-critical in this multicyclic compound. The cyclotide showed antimicrobial activity against various Gram-negative bacteria, including recurrent pathogens present in Chilean aquaculture. The highest antimicrobial activity was found to be against Flavobacterium psychrophilum. In addition, membrane blebbing on the bacterial surface after exposure to the cyclotide was visualized by SEM microscopy and the Sytox Green permeabilization assay showed the ability to disrupt the bacterial membrane. We postulate that this compound can be proposed for the control of fish farming infections.

The Roles of Spinochromes in Four Shallow Water Tropical Sea Urchins and Their Potential as Bioactive Pharmacological Agents

Spinochromes are principally known to be involved in sea urchin pigmentation as well as for their potentially interesting pharmacological properties. To assess their biological role in sea urchin physiology, experiments are undertaken on crude extracts from four species and on four isolated spinochromes in order to test their antibacterial, antioxidant, inflammatory and cytotoxic activities. First, the antibacterial assays show that the use of crude extracts as representatives of antibacterial effects of spinochromes are inaccurate. The assays on purified spinochromes showed a decrease in the growth of four strains with an intensity depending on the spinochromes/bacteria system, revealing the participation of spinochromes in the defense system against microorganisms. Secondly, in the 2,2-diphenyl-1-picrylhydrazyl antioxidant assays, spinochromes show an enhanced activity compared to the positive control. This latter observation suggests their involvement in ultraviolet radiation protection. Third, spinochromes present a pro-inflammatory effect on lipopolysaccharide-stimulated macrophages, highlighting their possible implication in the sea urchin immune system. Finally, cytotoxicity assays based on Trypan blue exclusion, performed in view of their possible future applications as drugs, show a weak cytotoxicity of these compounds against human cells. In conclusion, all results confirm the implication of spinochromes in sea urchin defense mechanisms against their external environment and reveal their potential for pharmacological and agronomical industries.