Pathogenic Bacteria In Fish Research Articles

Sensitivity of Heterotrophic Bacteria in the Low-Salinity Water Areas and Estuary in Siak District toward Pathogenic Bacteria in Fish

The high rate of bacterial diseases in fishes and shrimps has lead scientists seek for natural antibiotic products that would act as a solution. An example of this product is the secondary metabolic products from heterotrophic bacteria. These bacteria could easily be found in many water regions and estuaries, including the Siak District, Riau, Indonesia. Therefore, this study aims at determining the ability of bacterial isolates in inhibiting the growth of pathogens (Vibrio alginolyticus, Aeromonas hydrophila, and Pseudomonas sp.). The research was conducted from June to September 2018. It actuates the type of heterotrophic bacteria in the sampling area using the PCR technique. The phylogenetic structure of bacterial isolates obtained during this study was assessed by nucleotide sequencing of the 16S rRNA gene. The antagonism test showed that bacteria had the ability to inhibit the growth of pathogens (Vibrio alginolyticus, Aeromonas hydrophila, and Pseudomonas sp.). The results showed that 25 pure bacterial isolates were obtained, in which 10 of those were carried out by DNA sequencing; hence, it could be used as antimicrobes. Based on the analysis of 16S rDNA, 10 isolates were identified: 6 were Bacillus cereus and 2 were Pseudomonas aeruginosa with homology levels ranging from 97 to 99%, while the remaining two were suspected as the new species of isolates. From the result, it could be concluded that heterotrophic bacteria are found to be better used as antipathogens against Vibrio alginolitycus than hydrophila and Pseudomonas sp.

Borneo herbal plant extracts as a natural medication for prophylaxis and treatment of Aeromonas hydrophila and Pseudomonas fluorescens infection in tilapia ( Oreochromis niloticus).

Background: The combination of some plant extracts to prevent and treat bacterial infections is gaining momentum, because of effectiveness against certain bacteria. This study aims to describe the antibacterial and immunostimulant abilities of Boesenbergia pandurata (BP), Solanum ferox (SF) and Zingiber Zerumbet (ZZ) plant extracts to treat and prevent Aeromonas hydrophila and Pseudomonas fluorescens infection on Tilapia ( Oreochromis niloticus). Methods: Tilapia (initial weight 15±2 g) were injected intramuscularly (0.1 ml/fish) with a combination of A. hydrophila and P. fluorescens at a density of 1×10 5 CFU ml -1 of each bacteria. Treatment trials were performed at day 7 post-injection with each combined extract, while the prevention trial was performed by including the combined extract into the commercial diet for six and seven days prior to injection. Various extract combinations were 60 mg SF extract/kg feed with 40 mg ZZ/kg feed (SF60/ZZ40), SF50/ZZ50, BP90/SF10, and BP50/SF50. Haemato-immunological parameters were performed for four weeks. Results: In prevention trials, tilapia fed SF50/ZZ50 showed a significant increase of white and red blood cells. Similarly, significantly increased haematocrit was found in tilapia fed SF50/ZZ50 in the treatment trial but not in the prevention trial. In both trials, haemoglobin of tilapia was not affected by any combined extracts but decreased the number of bacteria. Phagocytic index, respiratory burst, lysozyme activity and survival rate of fish fed combined extracts were found significantly higher than controls. The amount of pathogenic bacteria in fish fed combined extracts was lower than the control at week 4 ( P<0.05). In both trials The percentage of survival rate and relative percent survival of tilapia fed SF 50/ZZ 50, showed the optimum results compared to the other combinations. Conclusions: The combined extract in feed, especially SF50/ZZ50 has a positive effect on the tilapia's innate immune system of tilapia to treat and prevent bacterial infections.

Borneo herbal plant extracts as a natural medication for prophylaxis and treatment of Aeromonas hydrophila and Pseudomonas fluorescens infection in tilapia ( Oreochromis niloticus)

Background: The combination of some plant extracts to prevent and treat bacterial infections is gaining momentum, because of effectiveness against certain bacteria. This study aims to describe the antibacterial and immunostimulant abilities of Boesenbergia pandurata (BP), Solanum ferox (SF) and Zingiber Zerumbet (ZZ) plant extracts to treat and prevent Aeromonas hydrophila and Pseudomonas fluorescens infection on Tilapia ( Oreochromis niloticus). Methods: Tilapia (initial weight 15±2 g) were injected intramuscularly (0.1 ml/fish) with a combination of A. hydrophila and P. fluorescens at a density of 1×10 5 CFU ml -1 of each bacteria. Treatment trials were performed at day 7 post-injection with each combined extract, while the prevention trial was performed by including the combined extract into the commercial diet for six and seven days prior to injection. Various extract combinations were 60 mg SF extract/kg feed with 40 mg ZZ/kg feed (SF60/ZZ40), SF50/ZZ50, BP90/SF10, and BP50/SF50. Haemato-immunological parameters were performed for four weeks. Results: In prevention trials, tilapia fed SF50/ZZ50 showed a significant increase of white and red blood cells. Similarly, significantly increased haematocrit was found in tilapia fed SF50/ZZ50 in the treatment trial but not in the prevention trial. In both trials, haemoglobin of tilapia was not affected by any combined extracts but decreased the number of bacteria. Phagocytic index, respiratory burst, lysozyme activity and survival rate of fish fed combined extracts were found significantly higher than controls. The amount of pathogenic bacteria in fish fed combined extracts was lower than the control at week 4 ( P<0.05). In both trials The percentage of survival rate and relative percent survival of tilapia fed SF 50/ZZ 50, showed the optimum results compared to the other combinations. Conclusions: The combined extract in feed, especially SF50/ZZ50 has a positive effect on the tilapia's innate immune system of tilapia to treat and prevent bacterial infections.

Borneo herbal plant extracts as a natural medication for prophylaxis and treatment of Aeromonas hydrophila and Pseudomonas fluorescens infection in tilapia ( Oreochromis niloticus).

Background: This study aims to describe the antibacterial and immunostimulant abilities of Boesenbergia pandurata (BP), Solanum ferox (SF) and Zingiber Zerumbet (ZZ) plant extracts to treat and prevent Aeromonas hydrophila and Pseudomonas fluorescens infection on Tilapia ( Oreochromis niloticus). Methods: Tilapia (initial weight 15±2 g) were injected intramuscularly (0.1 ml/fish) with a combination of A. hydrophila and P. fluorescens at a density of 1×10 5 CFU ml -1 of each bacteria. Treatment trials were performed at day 7 post-injection with each combined extract, while the prevention trial was performed by including the combined extract into the diet for six and seven days prior to injection. Various combinations of extract-60 ml SF extract/kg feed with 40 ml ZZ/kg feed (SF60/ZZ40), SF50/ZZ50, BP90/SF10, and BP50/SF50-were mixed with a commercial diet and used in both treatment and prevention trials. Haematological and immunological parameters were performed every week for four weeks. Results: In prevention trials, tilapia fed SF50/ZZ50 showed a significant increase of white and red blood cells from weeks 2 to 4. Similarly, significantly increased haematocrit was also found in tilapia fed SF50/ZZ50 in the treatment trial but not in the prevention trial. However, haemoglobin of tilapia in both trials was not affected by any of the various combinations of extract in the diet. Furthermore, phagocytic, respiratory burst, lysozyme activity indexes and survival rate of fish fed with combined extracts were found to be significantly higher than controls. Moreover, the amount of pathogenic bacteria in fish that were fed combined extracts was also lower than the control and was significantly different at week 4. Conclusions: This study indicates that the addition of combined extract into feed has a positive effect on the tilapia's immune system. The SF50/ZZ50 combination appears to improve the innate immune system of tilapia to treat and prevent bacterial infections.

Microplastics as a vector for the transport of the bacterial fish pathogen species Aeromonas salmonicida

Microplastics is widespread in the marine environment where it can cause numerous negative effects. It can provide space for the growth of organisms and serves as a vector for the long distance transfer of marine microorganisms. In this study, we examined the sea surface concentrations of microplastics in the North Adriatic and characterized bacterial communities living on the microplastics. DNA from microplastics particles was isolated by three different methods, followed by PCR amplification of 16S rDNA, clone libraries preparation and phylogenetic analysis. 28 bacterial species were identified on the microplastics particles including Aeromonas spp. and hydrocarbon-degrading bacterial species. Based on the 16S rDNA sequences the pathogenic fish bacteria Aeromonas salmonicida was identified for the first time on microplastics. Because A. salmonicida is responsible for illnesses in fish, it is crucial to get answers if and how microplastics pollution is responsible for spreading of diseases.

Morphological and biochemical characterization of two fish pathogenic bacteria: Aeromonas salmonicida and Yersinia ruckeri for rapid diagnosis of fish disease

Aeromonas salmonicida and Yersinia ruckeri are two common pathogenic fish bacteria responsible for furunculosis and Enteric Red Mouth disease (ERM), respectively. For the characterization of these two pathogens, a series of morphological (pigmentation, hemolyse, motility and body shape), biochemical tests (Gram staining, catalase, oxidase and API 20E strips) and a soft ionization technique (MALDI-TOF/MS) were performed in the laboratory. Pigmentation, motility, hemolysis and body shape was used as a preliminary identification of the bacteria. Both of the species were identified with the entire biochemical test without any doubt except API20E strips test. Although the API profile of A. salmonicida (0006104) was identified with high confidence (99.6%), but Y. ruckeri was misidentified as Vibrio mimicus. There are strong supports against Vibrio mimicus as it is a human pathogen, grow at a temperature more than 20oC, motile and oxidase positive bacteria. The Y. ruckeri is a non-motile fish bacteria and oxidase negative which are consistent with the study results. Agglutination test with Bionor Mono kit was also identified the bacteria as Y. ruckeri. For rapid diagnosis of infectious disease, accurate identification of pathogen is very important for commercial aquaculture.Asian J. Med. Biol. Res. March 2017, 3(1): 44-51

Impact of environmental bacterial communities on fish health in marine recirculating aquaculture systems

Marine cultured fish diseases caused by bacteria in recirculating aquaculture systems (RASs) greatly threaten fish aquaculture. To date, the dynamics of bacterial populations in RAS and their impacts to fish health remain largely unknown. In the present study, the bacterial communities in the water from two different marine RASs were analyzed using pyrosequencing technique. Fish disease syndromes and mortality had been reported from one RAS (RAS-d) while the fish in the other RAS remained healthy (RAS-h). The diversity of bacteria in each RAS and the abundance of each bacterium were identified based on sequencing the V4 hypervariable region of the 16S rRNA gene. A total number of 107,476 effective sequences were obtained from the pyrosequencing results. 640 and 844 operational taxonomic units (OTUs) were identified in RAS-d and RAS-h, respectively. In order level, tags annotation showed that Vibrionales and Flavobacteriales were the predominant strains in RAS-d with a relative abundance 50.5% and 36.5%, respectively. In contrast, the bacterial community in RAS-h contained 35.8% Vibrionales, 17.3% Alteromonadales, 10.7% Rhodobacterales, 7.43% Kordiimonadales, and 6.26% Oceanospirillales. In addition, the Vibrionaceae in the RAS-d represented 6.98% of the population which was significantly higher than that in RAS-h (0.40%). More potential pathogenic bacteria in fish, such as Vibrio harveyi, Vibrio rotiferianus were also found in the bacterial population in RAS-d. The results also showed that the bacteria community in RAS-h was more diverse and balanced than in RAS-d. These findings of this study suggested a potential correlation between fish diseases and environmental bacterial populations.

English

The need to conduct periodic surveillance on the presence, associated pathological alteration in tissues and the various environmental factors that could trigger some potential fish pathogens that result to disease outbreak in tilapia farming in Malaysia is paramount. This study was conducted to determine the presence of potential pathogenic bacteria in fish and water bodies that could trigger disease outbreak. Some potential pathogenic bacteria were isolated and identified from water, sediments and tissues of red tilapia reared in cage-cultured system in Kenyir Lake, Terengganu and Semantan River, Pahang, east of Peninsular Malaysia, also the water quality was assessed using standard techniques. The brain, eye and kidney were collected randomly from 30 tilapias from each of these water bodies. The bacteria were isolated and identified using standard methods. In Kenyir Lake, bacterial isolates that predominated in selected tissues of tilapia were Micrococcus spp., Aeromonas hydrophila, Staphylococcus spp., Pseudomonas aeruginosa and Enterobacter cloacae while in Semantan River, A. hydrophila and Staphylococcus spp. predominated. The water quality of Semantan River was found to be above the recommended limits of ammonia, sulphide, iron and nitrite-nitrogen levels. For the water sample, Staphylococcus xylosus was the most predominant bacteria isolates in Kenyir Lake, while Staphylococcus lentus was the most predominant of Semantan River. From the sediments, Pseudomonas aeruginosa and Enterobacter cloacae were isolated in Kenyir lake while, A. hydrophila was found in Semantan river. From this investigation, A. hydrophila and Staphylococcus spp. are the predominant bacteria in Red hybrid tilapia; water quality, animal and human activities may play a role in the susceptibility of red tilapia to these potentially pathogenic bacteria which have not being previously observed in Malaysia. There is need for periodic surveillance of water, sediment and tissues of fish to detect the pathogens of paramount importance to Malaysian aquaculture industry. &nbsp; Key words: Bacteria, Red hybrid tilapia, analytical profile index (API) test, water quality, lake, river.

Efficacy of florfenicol for control of mortality associated with Francisella noatunensis subsp. orientalis in Nile tilapia, Oreochromis niloticus (L.)

Francisella noatunensis subsp. orientalis (Fno) (syn. F.asiatica) is an emergent Gram-negative facultative intracellular bacterium. Although it is considered one of the most pathogenic bacteria in fish, there are no commercially available treatments or vaccines. The objective of this project was to determine the most efficacious concentration of florfenicol (FFC) [10, 15 or 20mg FFCkg(-1) body weight (bw) per days for 10days] administered in feed to control experimentally induced infections of Fno in Nile tilapia, Oreochromis niloticus (L.), reared in a recirculating aquaculture system. The cumulative mortality of fish that received 0, 10, 15 or 20mg FFCkg(-1) bw per day was 60, 37, 14 and 16%, respectively. Francisella noatunensis subsp. orientalis genome equivalents were detected in water from all challenged groups with slight reduction in the concentration in the florfenicol-treated groups 4days after treatment. The mean LOG of CFU Fnomg(-1) spleen was 3-5 and was present in all challenged groups at necropsy 11days after treatment (21days after challenge). Results show that florfenicol administered at doses of 15 and 20mg FFCkg(-1) bw per days for 10days significantly reduced mortality associated with francisellosis in Nile tilapia.

Environmental microbiota related to bacterial carriage in cultivated trout (Onchorhyncus mykiss and Salvenilus fontinalis).

The recent introduction and spreading of new pathogens, along with the global climate change, has contributed to a considerable decrease in trout production. The increase of fish production presumes the avoidance and control of limiting noxious factors (Purser and Forteath, 2003; Sedgwick, 1990; Shepherd and Bromage, 1992). The presence of potentially pathogenic bacteria in fish of different age categories (n=10/ basin) and level of bacterial contamination of culture waters (12 basins) on a commercial trout farm with mixed population of rainbow and brook trout was monitored by insemination on McConkey agar and use of ID 32 E, API 20NE and API Staph galleries. Both fish and culture waters were higly polluted with bacteria, but the highest bacterial load was found in commercial trout, suggesting the vulnerability of this age category. The pottentially pathogenic bacteria for both fish (Aeromonas hydrophila) and humans (E. coli) indicated technological failure and potential fecal polution of the waters, increasing the risk for handlers and consumers.

Applicability of photodynamic antimicrobial chemotherapy as an alternative to inactivate fish pathogenic bacteria in aquaculture systems

Aquaculture activities are increasing worldwide, stimulated by the progressive reduction of natural fish stocks in the oceans. However, these activities also suffer heavy production and financial losses resulting from fish infections caused by microbial pathogens, including multidrug resistant bacteria. Therefore, strategies to control fish infections are urgently needed, in order to make aquaculture industry more sustainable. Antimicrobial photodynamic therapy (aPDT) has emerged as an alternative to treat diseases and prevent the development of antibiotic resistance by pathogenic bacteria. The aim of this work was to evaluate the applicability of aPDT to inactivate pathogenic fish bacteria. To reach this objective a cationic porphyrin Tri-Py(+)-Me-PF was tested against nine pathogenic bacteria isolated from a semi-intensive aquaculture system and against the cultivable bacteria of the aquaculture system. The ecological impact of aPDT in the aquatic environment was also tested on the natural bacterial community, using the overall bacterial community structure and the cultivable bacteria as indicators. Photodynamic inactivation of bacterial isolates and of cultivable bacteria was assessed counting the number of colonies. The impact of aPDT in the overall bacterial community structure of the aquaculture water was evaluated by denaturing gel gradient electrophoresis (DGGE). The results showed that, in the presence of Tri-Py(+)-Me-PF, the growth of bacterial isolates was inhibited, resulting in a decrease of ≈7-8 log after 60-270 min of irradiation. Cultivable bacteria were also considerably affected, showing decreases up to the detection limit (≈2 log decrease on cell survival), but the inactivation rate varied significantly with the sampling period. The DGGE fingerprint analyses revealed changes in the bacterial community structure caused by the combination of aPDT and light. The results indicate that aPDT can be regarded as a new approach to control fish infections in aquaculture systems, but it is clearly more difficult to inactivate the complex natural bacterial communities of aquaculture waters than pure cultures of bacteria isolated from aquaculture systems. Considering the use of aPDT to inactivate pathogenic microbial community of aquaculture systems the monitoring of microorganisms is needed in order to select the most effective conditions.

Culturability and Persistence of Francisella noatunensis subsp. orientalis (syn. Francisella asiatica) in Sea- and Freshwater Microcosms

Francisella noatunensis subsp. orientalis (syn. Francisella asiatica), the causative agent of franciselliosis in warm-water fish, is a Gram-negative facultative intracellular bacterium. Although it has been characterized as one of the most pathogenic bacteria in fish, the water conditions that allow for its survival and infectious capacities outside the fish host are not known. Data obtained in this project indicate that both temperature and salinity are important factors in the culturability and persistence of F. noatunensis subsp. orientalis in both sea- and freshwater microcosms. These results indicate that culturable F. noatunensis subsp. orientalis persist for longer periods of time and at higher numbers in seawater, and its persistence is inversely related to water temperature. Moreover, the pathogenic properties of the bacteria suspended in water microcosms appear to decrease after only 24 h and become non-infective after 2 days in the absence of the fish host.

Enhancement of protective immunity in European eel (&amp;lt;italic&amp;gt;Anguilla anguilla&amp;lt;/italic&amp;gt;) against &amp;lt;italic&amp;gt;Aeromonas hydrophila&amp;lt;/italic&amp;gt; and &amp;lt;italic&amp;gt;Aeromonas sobria&amp;lt;/italic&amp;gt; by a recombinant &amp;lt;italic&amp;gt;Aeromonas&amp;lt;/italic&amp;gt; outer membrane protein

To develop a vaccine, which can simultaneously prevent the diseases caused by various pathogenic bacteria in fish, we try to find a conserved outer membrane protein (OMP) antigen from different bacterial pathogens. In this study, an OMP fragment of 747 bp (named as Omp-G), which was highly conserved in seven Aeromonas OMP sequences from the NCBI database, was amplified by PCR from one Aeromonas sobria strain (B10) and two Aeromonas hydrophila strains (B27 and B33) with the designed specific primers. The sequence was cloned into pGEX-2T (6 × His-tag) vector, expressed in Escherichia coli system, and then the recombinant protein (named as rOmp-G) was purified with nickel chelating affinity chromatography. The purified rOmp-G showed a good immunogenicity in rabbits and well-conserved characteristics in these three pathogens by enzyme-linked immunosorbed assay. Furthermore, the rOmp-G also showed good immunogenicity in eels (Anguilla anguilla) for eliciting significantly increased specific antibodies (P < 0.01), and providing higher protection efficiencies (P < 0.05) after the pathogens challenge. The values of the relative percent survival in eels were 70% and 50% for two A. hydrophila strain challenge, and 75% for A. sobria strain challenge. This is the first report of a potential vaccination in eels that simultaneously provide protectiveness against different Aeromonas pathogens with a conserved partial OMP.

The In Vitro Activity of a Range of Natural Bioflavonoids Against Five Species of Pathogenic Fish Bacteria

The in vitro antibacterial activity of thirty two plant-derived compounds (26 crude herbal extraction and 6 pure citrus-based bioflavonoids) were tested on five different species of aquatic bacterial pathogens (Aeromonas hydrophila, A. salmonicida, A. sobria, Edwardsiella ictaluri, and E. tarda) over a period of 72 hours at 22 oC. From the agar diffusion test, six pure citrus-based bioflavonoids (apigenin, catechin, hesperidin, morin, naringin and quercetin) appeared to impact on growth when used at concentrations ranging from 10 ppm - 1000 ppm. To confirm their effect on the growth dynamics of each bacteria, a 1000 ppm dose of the appropriate bioflavonoid was added to a bacterial culture and daily changes in culture growth were measured. Quercetin was found to be bacteriocidal against all the bacterial strains. Morin was found to be bacteriocidal against only 4 out of 6 strains while hesperidin was found to affect the growth of all the tested bacterial strains, working both as a bacteriocidal and as a bacteriostatic agent. Apigenin performed poorly and had no effect on the growth of any bacterial strain while catechin and naringin were found to be generally bacteriostatic in action but had little impact on the growth of the Aeromonad strains. From the current in vitro work, it was concluded that certain plant extracts do have an impact on the growth dynamics of select bacteria and show potential as alternatives to the use of antimicrobials, but further research is required to assess their performance in vivo.

Incidence of indicator organisms, opportunistic and pathogenic bacteria in fish

Fish is an excellent source of high quality protein; however, it is susceptible to microbial spoilage. Fish carries high microbial load on the surface of the skin, in the intestine and in the gills. In Botswana, fishermen catch fish and sell their products in the open market. The microbiological quality and safety of these street vended fish have always been contentious. Therefore, a study on fish sold in Gaborone, Botswana was conducted from July 2006 to January 2007. Tilapia from the supermarkets and tilapia and catfish from street vendors were analyzed for the microbial load, presence of indicator microorganisms, opportunistic and pathogenic bacteria using conventional microbiological methods. Though coliforms were found in 84% of fish from the street vendors, only 16% of the fish had coliforms above the acceptable limits (3 log10 CFU/g). No Escherichia coli were isolated. Bacteria which are associated with plants, animals and soils but are normally classified as coliforms because of their biochemical reactions to sugars such as Citrobacter species, Klebsiella species including the enteropathogen Salmonella species were isolated. Fresh water or tap water is not available where vendors degut the fish. Hence, they carry water in containers to the point of sale sites and use it repeatedly. The unsanitary water (8.7 log10 CFU/ml of bacteria) used during the gutting of tilapia on the streets influenced the microbial levels in the fish, which were 6.0 log10 CFU/g compared to the 3.90 log10 CFU/g of ungutted whole tilapia from the same sale points. Frozen tilapia from supermarkets also had high bacterial counts (4.8 log10 CFU/g). Staphylococcus species were isolated frequently in all fish analyzed. Salmonella arizonae, Salmonella paratyphi (22-40%) was only isolated in street vended fish. Other bacterial isolates from fish included Citrobacter brackii, Citrobacter freundii, Enterobacter sakazakii, Enterobacter cloacae, Vibrio cholorae, Proteus mirabilis, Proteus vulgaris, Klebsiella pneumoniae and Aeromonas hydrophila. The presence of diverse enteric bacteria indicated the degree of cross contamination from the handlers. Their presence represents a potential hazard to humans, especially the immunocompromised consumers such as cases of HIV/AIDS. Stringent regulations on registration of fishermen, traders, education and mandatory observance of sanitation at trading points and use of ice have to be enforced to ensure safety of fish consumption.Key words: Indicator bacteria, pathogens, tilapia, catfish

Pathogenic bacteria, fish, DNA molecular, PCR

Food infection and intoxication of fish products are common due to consumption of foodexposed by either pathogenic or toxin promoter bacteria. A number of pathogenic bacteria havebeen identified related to fish and seafood such as Vibrio parahaemolyticusand other Vibrios,Escherichia coli, Aeromonas spp., Salmonellaspp., Staphylococcus aureus, Listeriamonocytogenes, Clostridium botulinum, C. perfringens, and Shigellaspp. However, isolationand identification of pathogenic bacteria from fish and seafood are often difficult due to the highnumber of contaminating and indigenous bacteria, while numbers of pathogenic bacteria arerelatively low. In the last 3 decades, several molecular methods have been developed and adoptedas official standard to supplement classical method, such as polymerase chain reaction (PCR)and its applications. Besides its limitation, molecular based identification offers advantages asroutine or screening analytical protocol for pathogenic bacteria in fish and seafood products.

In Vitro Efficacy of Human-Derived Probiotic, Lactobacillus rhamnosus Against Pathogenic Bacteria in Fish and Frogs

In Vitro Efficacy of Human-Derived Probiotic, Lactobacillus rhamnosus Against Pathogenic Bacteria in Fish and Frogs

Phenotypic Characterization of Human Pathogenic Bacteria in Fish from the Coastal Waters of South West Cameroon: Public Health Implications

Increasing economic and recreational opportunities, attractive scenery and a perception of a better quality of life are luring people to the coast. Unfortunately, these activities together with the commensurate increase in population in the area inevitably result in pollution of coastal waters with excessive microorganisms and other pollutants. Microbial pollutants not only contaminate the coastal water but also aquatic food sources, thus posing a health risk to consumers. Fish is a major source of protein in Cameroon, especially in the coastal areas. In this study, we investigated the microbiological quality of fish from the Limbe and Tiko beaches in South West Cameroon from May to October 2007. We isolated human pathogenic bacteria from three anatomic sites (skin, gills, intestine) of 50 fish (150 specimens) and investigated their susceptibility patterns to a battery of antibiotics. Data were analyzed statistically using chi2 with significance set at p < .05. Eleven bacterial species were identified, including Escherichia coli type 1 (20.8%), Citrobacter fruendii (16.4%), Proteus vulgaris (13%), Klebsiella pneumoniae (12.1%), Klebsiella ozaenae (7.7%), Enterobacter cloacae (7.2%), Klebsiella oxytoca (5.8%), Serratia marcescens (4.8%), Serratia odorifera (4.8%), Hafnia alvei (4.4%) and Proteus penneri (2.9%). More contaminated fish were found at Limbe beach than at Tiko beach (61.4% versus 38.6%, respectively (p < .05)). When ranking contamination with respect to anatomic site, skin was the most contaminated (40.6%) specimen and gills the least (28.5%). Ciprofloxacillin, ofloxacillin, and cotrimoxazole were the most effective antibiotics against all isolates, exhibiting 100% sensitivity. Almost half of the isolates (45.7%) were resistant to ampicillin. The results of our study demonstrate that fish from the coastal waters of South West Cameroon are a source of human pathogenic and opportunistic bacteria; hence this finding has public health implications.

Reduction of exoprotease production in Aeromonas hydrophila by tomato fruits extract (Lycopersicon esculentum Mill.)

Aeromonas hydrophila is pathogenic bacteria in fish. One of its virulence factors is exoprotease. The production of exoprotease is controlled by a quorum sensing system. Quorum sensing is an intercellular communication of bacteria that using a signal molecule of C4-HSL. The exoprotease production of A. hydrophila can be blocked by using quorum sensing inhibitors. The inhibition of quorum sensing of A. hydrophila can be conducted by C4-HSL analogs molecules. In this research, the molecules that predicted as quorum sensing inhibitors and act as C4-HSL analog molecules were furanone from tomato fruits. The inhibition of quorum sensing of A. hydrophila could be shown by a reduction of exoprotease production. The aim of this research was to determine the reduction of exoprotease production of A. hydrophila by extracts of n-hexane, ethyl acetate and methanol of tomato fruits with the concentrations of 0%, 2%, 4%, 6% and 8%, respectively. The qualitative exoprotease assay result showed that n-hexane extract of tomato had no effect on growth and exoprotease production of A. hydrophila. As much as 4% of ethyl acetate extract of tomato fruits could inhibit exoprotease production, but affect A. hydrophilla growth. Meanwhile, 4% methanol extract of tomato fruits could inhibit exoprotease production, without affect A. hydrophilla growth. The quantitative exoprotease assay result showed that 4% of methanol extract could inhibit exoprotease production by 71.68% without affect the growth of A. hydrophila.

Two new nitrogen-fixing bacteria from the rhizosphere of mangrove trees: Their isolation, identification and in vitro interaction with rhizosphere Staphylococcus sp.

Two new diazotrophic bacteria, Listonella anguillarum and Vibrio campbellii, and one non-nitrogen-fixing bacterium, Staphylococcus sp., were isolated from the rhizosphere of mangrove trees. Strains of these newly-defined diazotrophs are known as pathogenic bacteria in fish and shellfish. During the purification of diazotrophic species from the entire rhizosphere population, N 2-fixation of the bacterial mixtures decreased. When grown in vitro in mixed cultures, the non-fixing bacterium Staphylococcus sp. increased the nitrogen-fixing capacity of L. anguillarum by 17% over the pure culture; the nitrogen-fixing capacity per bacterial cell increased 22%. This interaction was not due to a change in O 2 concentration. Staphylococcus sp. decreased the nitrogen-fixing capacity of V. campbellii by 15%. These findings indicate that (i) other species of rhizosphere bacteria, apart from the common diazotrophic species, should be evaluated for their contribution to the nitrogen-fixation process in mangrove communities; and (ii) the nitrogen-fixing activity detected in the rhizosphere of mangrove plants is probably not the result of individual nitrogen-fixing strains, but the sum of interactions between members of the rhizosphere community.