Screening of the Antibacterial Activity of Some Marine Algae Against Fish and Human Pathogens

This study aims to investigate the effect of some algal extracts as antibacterial agents against some pathogenic bacteria. Thus the ethyl acetate and methanolic extracts of the marine algae Ulva lactuca, Enteromorpha compressa, Ulva fasciata, Pterocladia capillacea, Corallina mediterranea, Hypnea musciformis and Padina pavonia, collected from the coast of Alexandria (Egypt), were tested as antibacterial agents against fish and human pathogenic bacteria; Aeromonas hydrophila, Vibrio anguillarum, Pseudomonas fluorescens, Staphylococcus aureus, Pseudomonas aeruginosa and Salmonella typhimurium. The best activities were shown by the methanolic-L extract of P. capillacea against P. fluorescens, V. anguillarum and P. aeruginosa. The methanolic-L extract of U. lactuca showed high activity towards A. hydrophila, V. anguillarum, P. fluorescens and S. aureus. Cluster analysis was used to study the action of the crude algal extracts.


INTRODUCTION
Aeromonas hydrophila causes infection and several diseases like hemorrhagic septicemia, fin and tai l rot in fishes. 3,4V.
Bull High Inst Public Health Vol.39 No.1 [2009]   anguillarum causes a bacteraemia in salmonoid fish that leads to internal The main objective of this study is to investigate the action of some algal extracts as antibacterial agents against some pathogenic bacteria.

MATERIAL AND METHODS
Seven species of marine algae from the divisions; Chlorophyta (U.

Statistical analysis:
Statistical analyses were performed by Minitab statistical software Version 14, using cluster analysis for data upon complete linkage level.

Antibacterial activity:
The

Cluster analysis:
The action of the different algal extracts on the tested pathogens was studied using the cluster analysis as shown in  This work showed that Ulva lactuca possessed significant antibacterial activity against different pathogenic bacteria in contrast to the results of Perez et al. 24 which may be due to time and place of sample collection.Also, it was in contrast with Wefky and Ghobrial 25 who reported that the acetone and ethanolic extracts of P. capillacea had strong antimicrobial activity against fish pathogens while no activity was observed by the methanolic extract.
The present results are in consistence with the findings of previous studies for the crude extracts of some green, red and brown algae that have great antibacterial activity against Gram positive and Gram negative bacteria. 26,27e results also revealed that the algal extracts showed significant activity against some of the tested pathogenic bacteria, however, other strains did not respond to these extracts.This might be due to masking of the antibacterial activity by the presence of some inhibitory compounds in the extract 21 as well as the distribution of antimicrobial substances which varied from species to species. 28uster analysis showed that high Bacterial infection causes high rate of mortality for human and aquaculture organisms.Staphylococcus aureus and Pseudomonas aeruginosa cause mastitis, diarrhea and typhoid fever.1,2 diseases cause economic losses in aquaculture on global scale.The antibiotic resistant bacteria associated with fish disease are a worldwide problem in aquaculture and have received a considerable attention in recent years. 6The search for new effective antimicrobial agents is necessary due to the appearance of microbial resistance and occurrence of fatal opportunistic infections.The development of antimicrobial resistance in many pathogenic microbes possesses one of the most serious problems in the control of infectious diseases. 7Using synthetic drugs are not recommended nowadays because of some ill effects to the organisms and human consumption.Therefore, research is focused on herbal medicines as alternate antibiotics.Marine macroalgae are good sources for new antimicrobial agents and they are able to produce a variety of secondary metabolites characterized by a broad spectrum of biological activities against human pathogens, fungi and yeast.However, there are a few reports concerning their effects against fish pathogens. 8-10Some substances obtained from marine algae such as amino acids, terpenoids, aeruginosa.The tested pathogens were varied in their response to the antibacterial action of the different extracts.The most susceptible organisms were A. hydrophila and P. fluorescens.The growth of A. hydrophila was strongly inhibited by the methanolic-L extracts of U. lactuca (IZ = 27 mm) and H. musciformis (IZ = 21 mm) while P. fluorescens was strongly inhibited by the methanolic-L extracts of P. capillacea (IZ = 29) and U. lactuca (IZ = 20 mm).

Fig. [ 2
Fig. [2].They were clustered into 5 groups (A, B, C, D and E) in addition to two single clusters representing the ethyl acetate extract of U. lactuca and linkage (100%) exists between the antibacterial actions of the methanolic-R extract of U. lactuca and ethyl acetate extract of C. mediterranea.This may be attributed to their collection from the same site (Abu Qir) and during the same season.High linkages also observed between the methanolic-R extracts of P.capillacea and H. musciformis as well as the ethyl acetate extracts of H. musciformis, and both of U. fasciata (A) and (B) while lower linkage was found between the methanolic-L extracts of U. lactuca and P. capillacea.be useful as therapeutic agents for fish populations with bacterial diseases, and should be investigated for natural antibiotics.The results also showed that methanol is an efficient solvent for extracting the bioactive materials and the significant inhibition zones were observed for methanolic extracts.RECOMMENDATION Further investigations should be undertaken for isolation and identification of the bioactive compounds which are responsible for the antibacterial effect.AKNOWLEDGMENT We thank Dr. N. G. Shams El Din, Associate Prof. of Aquatic Plants, Division of Marine Environment, National Institute of Oceanography and Fisheries for identifying the algae.
alga collected from El-Manshia; B: The alga collected from El-Anfoushy.

Fig
Fig ( ): The Area of Study and The collection Stations

Antibacterial activity of algal extracts:
lactuca, E. compressa, U. fasciata), Rhodophyta (P.capillacea, C. mediterranea, H. musciformis) and Phaeophyta (P.pavonia) [table 1] were collected during May and July, 2008 from sublittoral rocks at Abu Qir Bay and the Eastern Harbor(El-Manshia and El-Anfoushy) in the coast of Alexandria Fig.[1].Their extracts o C for 24 h.The inhibition zone was determined for each well and expressed in millimeter.