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.

BackgroundThe emergence of multidrug-resistant bacteria is a worldwide concern and in order to find an alternative to this problem, the occurrence of antimicrobial compounds in Plectranthus amboinicus essential oil was investigated. Thus, this study aims to determine susceptibility of Staphylococcus aureus isolated from food to antibiotics, P. amboinicus essential oil (PAEO) and carvacrol.MethodsLeaves and stem of P. amboinicus were used for extraction of essential oil (PAEO) by hydrodistillation technique and EO chemical analysis was performed by gas chromatography coupled to a mass spectrometer. S. aureus strains (n = 35) isolated from food and S. aureus ATCC 6538 were used to evaluate the antimicrobial and antibiofilm activity of PAEO and carvacrol. All strains (n = 35) were submitted to antimicrobial susceptibility profile by disk diffusion method. Determination of MIC and MBC was performed by microdilution technique and antibiofilm activity was determined by microtiter-plate technique with crystal violet assay and counting viable cells in Colony Forming Units (CFU).ResultsCarvacrol (88.17%) was the major component in the PAEO. Antibiotic resistance was detected in 28 S. aureus strains (80%) and 12 strains (34.3%) were oxacillin and vancomycin-resistant (OVRSA). From the 28 resistant strains, 7 (25%) showed resistance plasmid of 12,000 bp. All strains (n = 35) were sensitive to PAEO and carvacrol, with inhibition zones ranging from 16 to 38 mm and 23 to 42 mm, respectively. The lowest MIC (0.25 mg mL−1) and MBC (0.5 mg mL−1) values were observed when carvacrol was used against OVRSA. When a 0.5 mg mL−1 concentration of PAEO and carvacrol was used, no viable cells were found on S. aureus biofilm.ConclusionThe antibacterial effect of carvacrol and PAEO proves to be a possible alternative against planktonic forms and staphylococcal biofilm.

No abstract

This study was aimed at evaluating the microbiological quality of mangrove oysters (Crassostrea rhizophorae), collected at a natural oyster bed in the estuary of Cocó river (Fortaleza, Ceará, Brazil). MPN values were used for estimating the total (TC) and fecal (FC) coliforms and Enterococcus spp. TC and FC MPN values in the whole muscle and intervalve liquid ranged from <1.8 to >1,600/g and from <1.8 to 920/g, respectively. The MPN estimates for Enterococcus spp. were between <3.0 and >1,100/g. No correlation was found between the physico-chemical parameters (temperature, salinity and pH) of the surrounding water and the bacteriological contamination levels found in the tested oysters. The only correlation found was between TC and FC values. Enterococcus spp. strains were isolated and subjected to biochemical tests for species identification. The capacity of those strains for production of a bacteriocin-like inhibitory substance was tested using the Escherichia coli strain ATCC 25922 as a testing organism. Only one, E. faecalis, out of 121 Enterococcus strains tested, presented the inhibitory activity.

Thirty-two Escherichia coli strains were isolated from red snapper (Lutjanus purpureus) and from seabob shrimp (Xiphopenaeus kroyeri). The strains were numbered S1-S16, and F1-F16, which corresponds to the isolation origin from shrimp (S) and fish (F). The isolates were biologically and antigenically characterized by agglutination tests with enteropathogenic E. coli (EPEC)-, enteroinvasive E. coli (EIEC)- and enterohemorrhagic E. coli (EHEC) O157-specific antisera. The ETEC enterotoxins were characterized by GMI-ELISA for enterotoxin LT-1 (thermolabile) and by inoculation of supernatants prepared from newly born mice for enterotoxin Sta. A total of 14 strains produced exotoxins, of which seven were thermolabile (LT) and seven were thermostable (ST). Antimicrobial susceptibility profiles were determined by disc diffusion in agar using ampicillin, cephalothin, cefoxitin, ceftriaxone, imipenem, nalidixic acid, ciprofloxacin, chloramphenicol, gentamicin, nitrofurantoin, sulfamethoxazole-trimethoprim, and tetracycline. Four isolates showed lower susceptibility to some antibiotics, two strains were resistant to ampicillin, tetracycline, and sulfamethoxazole-trimethoprim, and two were resistant to tetracycline and nitrofurantoin. Plasmids were extracted in the four resistant isolates; two of them contained plasmids whose molecular weight varied from low to high. The characterization of LT- and ST-toxin-producing E. coli strains displaying multiresistance and containing plasmids suggests the need for tightening current control measures for the use of antimicrobials.