SUMMARYGuava leaf tea of Psidium guajava Linnaeus is commonly used as a medicine against gastroenteritis and child diarrhea by those who cannot afford or do not have access to antibiotics. This study screened the antimicrobial effect of essential oils and methanol, hexane, ethyl acetate extracts from guava leaves. The extracts were tested against diarrhea-causing bacteria: Staphylococcus aureus, Salmonella spp. and Escherichia coli. Strains that were screened included isolates from seabob shrimp, Xiphopenaeus kroyeri (Heller) and laboratory-type strains. Of the bacteria tested, Staphylococcus aureus strains were most inhibited by the extracts. The methanol extract showed greatest bacterial inhibition. No statistically significant differences were observed between the tested extract concentrations and their effect. The essential oil extract showed inhibitory activity against S. aureus and Salmonella spp. The strains isolated from the shrimp showed some resistance to commercially available antibiotics. These data support the use of guava leaf-made medicines in diarrhea cases where access to commercial antibiotics is restricted. In conclusion, guava leaf extracts and essential oil are very active against S. aureus, thus making up important potential sources of new antimicrobial compounds.

Out of the twenty-four samples of shrimp and fish muscle used for this study, twelve were collected near a large marine sewer for waste disposal, 3 km off the coast of Fortaleza (Brazil) and used for the isolation of E. coli. Other twelve were collected at the Mucuripe fresh fish market (Fortaleza, Brazil) and used for the isolation of Staphylococcus aureus. Ethanol, water and acetone-diluted extracts of guava and papaya leaf sprouts were tested on the bacteria in order to verify their microbicidal potential. The E. coli strains used in the trials were rated LT positive. The papaya leaf extracts (Carica papaya Linn) showed no microbicidal activity while the guava sprout extracts (Psidium guajava Linn) displayed halos exceeding 13 mm for both species, an effect considered to be inhibitory by the method employed. Guava sprout extracts by 50% diluted ethanol most effectively inhibited E. coli (EPEC), while those in 50% acetone were less effective. It may be concluded that guava sprout extracts constitute a feasible treatment option for diarrhea caused by E. coli or by S. aureus-produced toxins, due to their quick curative action, easy availability in tropical countries and low cost to the consumer.

The presence of faecal contamination and pathogenic microorganisms in samples of dry and wet sand collected from three major beaches in Fortaleza, Ceará State, Brazil: (Praia do Mucuripe, Praia do Futuro and Praia do Caça e Pesca), during the period of May 1999 to January 2000 was evaluated. Praia do Caça e Pesca had the highest incidence of E. coli in dry sand (56%) followed by Praia do Mucuripe (28%) and Praia do Futuro (16%). In wet sand, results were 48%, 28% and 24% for Praia do Caça e Pesca, Praia do Futuro and Praia do Mucuripe, respectively. Only two samples from Praia do Futuro, one from dry sand and another one from wet sand, were positive for Salmonella. V. parahaemolyticus was isolated from four samples from Praia do Caça e Pesca (two from dry-sand samples and two from wet-sand), one from Praia do Futuro (wet sand), and three and four from Praia do Mucuripe (wet and dry sand, respectively). Yeasts belonged to the Candida genus. Dry-sand samples presented higher yeast contaminations level than wet-sand ones. Praia do Futuro had the highest level of yeast contamination (41%), followed by Praia do Caça e Pesca (33%) and Praia do Mucuripe (26%).