Bactericidal activity of lemon juice and lemon derivatives against Vibrio cholerae.

Food products can be possible vectors of the agent responsible for cholera epidemics, because some of these products allow Vibrio cholerae O1 to develop to concentrations above the dangerous level. This study deals with the behaviour of essential oils, natural and concentrated lemon juice and fresh and dehydrated lemon peel against V. cholerae O1 biotype Eltor serotype Inaba tox+. Our aim was to evaluate whether these products, used at different dilutions, exhibit bactericidal or bacteriostatic activity against the microorganism, when present at concentrations of 10(2), 10(4), 10(6) and 10(8) colony forming units (CFU) ml(-1), and after different exposure times. 10(8) CFU ml(-1) was considered an infectious dose. Concentrated lemon juice and essential oils inhibited V. cholerae completely at all studied dilutions and exposure times. Fresh lemon peel and dehydrated lemon peel partially inhibited growth of V. cholerae. Freshly squeezed lemon juice, diluted to 10(-2), showed complete inhibition of V. cholerae at a concentration of 10(8) CFU ml(-1) after 5 min of exposure time; a dilution of 2 x 10(-3) produced inhibition after 15 min and a dilution of 10(-3) after 30 min. It can be concluded that lemon, a natural product which is easily obtained, acts as a biocide against V. cholerae, and is, therefore, an efficient decontaminant, harmless to humans.

A clinical and bacteriological study of children suffering from haemolytic uraemic syndrome in Tucuman, Argentina.

Haemolytic uraemic syndrome (HUS) is a disease with serious consequences for children, such as terminal chronic renal failure. During the last few years there have been numerous studies undertaken to determine whether there is a relationship between this disease and the presence of Shiga toxin-producing bacteria. Escherichia coli (E. coli) O157:H7 is one of the most frequent etiologic agents of HUS. It acts through cytotoxins called Shiga toxin 1 (Stx1) and/or Shiga toxin 2 (Stx2) and carries a 90-Kb plasmid codified for an adhesion fimbria which is part of its pathogenicity. The objectives of this study were to: 1). confirm whether there exists a relationship between severity and clinical presentation of HUS; 2). prove the existence of Stx1 and/or Stx2 in the faeces of HUS patients; and 3). detect the presence of Stx1- and/or Stx2-producing E. coli. Our results did not show any difference in the average age, sex or clinical behavior between children with diarrhea positive (D+) HUS and diarrhea negative (D-) HUS. Male patients were predominant, as was incidence during summer, considering all cases. Nor could we find any relationship between severity and HUS type. E. coli O157:H7 was isolated in 40% of the patients with (D+) HUS and in 50% of patients with (D-) HUS. Another serotype, O55:K59, was also isolated (7%). Stx1 and/or Stx2 were found in all HUS cases. The following virulence factors of E. coli strains isolated from 12 patients were found: Adhesion fimbria (100%), Stx1 (16%), Stx2 (32%), and Stx1 + Stx2 (50%). None of these factors was found in control patients. Sixty-three percent of the HUS cases showed seroconversion for lipopolysaccharides of E. coli O157. We drew the following conclusions: 1). there is no significant relationship between seriousness of HUS and type of disease; 2). an association exists between HUS and the production of Stx1 and Stx2; 3). the incidence of E. coli O157:H7 was high in Tucuman, Argentina; and 4). Stx2 alone or in association with Stx1 was the predominant toxin.

In vitro comparison of disk diffusion and agar dilution antibiotic susceptibility test methods for Neisseria gonorrhoeae.

At present, most Neisseria gonorrhoeae testing is done with beta-lactamase and agar dilution tests with common therapeutic agents. Generally, in bacteriological diagnosis laboratories in Argentina, study of antibiotic susceptibility of N. gonorrhoeae is based on beta-lactamase determination and agar dilution method with common therapeutic agents. The National Committee for Clinical Laboratory Standards (NCCLS) has recently described a disk diffusion test that produces results comparable to the reference agar dilution method for antibiotic susceptibility of N. gonorrhoeae, using a dispersion diagram for analyzing the correlation between both techniques. We obtained 57 gonococcal isolates from patients attending a clinic for sexually transmitted diseases in Tucumán, Argentina. Antibiotic susceptibility tests using agar dilution and disk diffusion techniques were compared. The established NCCLS interpretive criteria for both susceptibility methods appeared to be applicable to domestic gonococcal strains. The correlation between the MIC's and the zones of inhibition was studied for penicillin, ampicillin, cefoxitin, spectinomycin, cefotaxime, cephaloridine, cephalexin, tetracycline, norfloxacin and kanamycin. Dispersion diagrams showed a high correlation between both methods.

Association between hemolytic uremic syndrome and verotoxin-producing strains of E. coli.

One of the most frequent etiologic agents of Hemolytic Uremic Syndrome (HUS) is Escherichia coli O157H7, a microorganism that possesses virulence factors (Shiga-like Toxins I and II and adhesion fimbriae). The present study was set up to determine the relationship between HUS and the presence of Verotoxin in patients of "Niño Jesús" Children's Hospital. Tucumán, Argentina. 19 Children between 0 and 4 years old suffering from HUS (typical and atypical symptoms) and 15 control children of similar sex and age were selected. Presence of enterohemorrhagic E. coli was studied in both groups using molecular hybridization techniques. Free Verotoxin and Verotoxin-producing E. coli were analyzed in Vero cells. The following results were obtained: 1) The cytotoxic effect on Vero cells from fecal filtrates was observed in all children suffering from HUS 2) Verotoxin-producing E. coli was detected in only 12 of them 3) None of the filtrates of feces from control children presented a cytotoxic effect on Vero cells 4) In 8 of the patients suffering from HUS serotype O157H7 was isolated, in one O55K59 and in 3 typification of E. coli was not possible with the serums assayed 5) 77.5% of the strains isolated from HUS patients gave a positive molecular hybridization reaction, showing the following: Adhesion Fimbriae (AF) (25%); AF + Shiga-like Toxin I (13.75%); AF + Shiga-like Toxin II (20%); AF + Shiga-like Toxins I and II (41.25%). In patients suffering from atypical HUS a combination of AF + Shiga-like Toxins I and II was found. The 15 control children did not hybridize to the probes assayed. From the results obtained we may conclude that there exists a relationship between HUS and the presence of Verotoxin in the children suffering from HUS studied. The predominant serotype in our cases was O157H7 and Shiga-like Toxin II was found with highest frequency.

Action against Vibrio cholerae O1 Tox+ of chemical products used in the lemon production.

Tucuman is the first lemon exporting province in Argentina and the fourth lemon exporter in the world. The present work was set up to study the survival of Vibrio cholerae O1 Tox+ after application of different chemical products used in the lemon production (from its cultivation until its packing). The following products were studied: copper oxychloride, benomil (a carbamate), active chlorine, sodium-o-phenylphenoate, guazatine (a polyamine mixture), imazalil (an imidazole) and fresh and dehydrated lemon peel. Using different dilutions of the products above mentioned antimicrobial tests were carried out with different exposure times against V. cholerae Serogroup O1, Biotype El Tor, Serotype Inaba. The microorganism was used at concentrations of 10(2), 10(4), 10(6) and 10(8) CFU ml-1, the latter one being considered as an infectious dose. The following results were obtained: 1) Active chlorine (chlorinated water) showed bactericidal activity at concentrations of 0.5 x 10(-1), 10(-1), y 2 x 10(-1) g l-1 after 10 min of exposure time. 2) Copper oxychloride, sodium-o-phenylphenoate, guazatine and imazalil showed bactericidal activity against V. cholerae at concentrations of 10(2) and 10(4) CFU ml-1. 3) Due to the fact that the fruit is successively sprayed with several chemical products during its cultivation, it could be proposed that the result of the successive treatments is superior to the result of a treatment with each of the individual products. This consideration should be taken into account when evaluating the eventual protection of the lemon.

Evaluation of the standardized disk diffusion and agar dilution antibiotic susceptibility test methods by using strains of Neisseria gonorrhoeae from Tucumán, Argentina.

At present, most Neisseria gonorrhoeae testing is done with beta-lactamase and agar dilution tests using common therapeutic agents. Generally, in bacteriological diagnosis laboratories in Argentina, study of antibiotic susceptibility of N. gonorrhoeae is based on beta-lactamase determination and agar dilution method using common therapeutic agents. The National Committee for Clinical Laboratory Standards (NCCLS) recently described a disk diffusion test that produces results similar to the reference agar dilution method for antibiotic susceptibility of N. gonorrhoeae. We obtained 57 gonococcal isolates from patients attending a clinic for sexually transmitted diseases in Tucumán, Argentina. Antibiotic susceptibility tests using agar dilution and disk diffusion techniques were compared. The established NCCLS interpretive criteria for both susceptibility methods appeared to be applicable to domestic gonococcal strains. The correlation between the minimum inhibitory concentration (MIC's) and the zones of inhibition was studied for penicillin, ampicillin, cefoxitin, spectinomycin, cefotaxime, cephaloridine, cephalexin, tetracycline, norfloxacin and kanamycin. Dispersion diagrams showed a high correlation between both methods, with a sensitivity of 89% and specificity of 91%.

Bactericidal activity against Vibrio cholerae of chemical products used in lemon production in Tucumán, Argentina.

The present research was set up to verify whether the chemical products used in lemon production (from cultivation until packaging) have a bactericidal or a bacteriostatic ability against Vibrio cholerae O1. The studied products were: copper oxychloride, benomil (a carbamate), active chlorine, sodium-o-phenylphenoate, guazatine (a polyamine mixture), imazalil (an imidazole) and lemon peel. The latter was studied with and without treatment using the above mentioned chemicals. Different dilutions of these products were tried out with varying exposure times against the bacterium V. cholerae Serogroup O1, Biotype E1 Tor, Serotype Inaba. The concentrations of the microorganism ranged from 10(2) to 10(8) CFU ml-1, the latter one being considered an infectious dose. The following results were obtained: 1) active chlorine (chlorinated water) showed bactericidal activity at concentrations of 50, 100 and 200 ppm after 10 min of exposure time, 2) copper oxychloride, sodium-o-phenylphenoate, guazatine and imazalil showed bactericidal activity against V. cholerae at concentrations of 10(2) and 10(4) CFU ml-1, 3) due to the fact that during its cultivation the fruit is successively sprayed with several chemical products, it could be that the result of the successive treatments is superior to the result of a repeated treatment with each of the individual products. This consideration should be taken into account when evaluating the eventual protection of the lemon.

Agar dilution method for susceptibility testing of Neisseria gonorrhoeae.

The antibiotic susceptibilities of Neisseria gonorrhoeae isolates obtained from patients attending a clinic for sexually transmitted diseases in Tucumán, Argentina, were determined by the agar dilution method (MIC). 3.5% of the isolates produced beta-lactamase. A total of 96.5% of beta-lactamase negative isolates tested were susceptible to penicillin (MIC < or = 2 micrograms/ml-1); 14.03% of the tested isolates were resistant to tetracycline (MIC < or = 2 micrograms/ml-1), and 98% of the tested isolates were susceptible to spectinomycin (MIC < or = 64 micrograms/ml-1). The MICs for 95% of the isolates, tested for other drugs were: < or = 2 micrograms/ml-1 for cefoxitin, < or = 0.06 microgram/ml-1 for cefotaxime, < or = 0.25 microgram/ml-1 for norfloxacin, < or = 10 micrograms/ml-1 for cephaloridine, < or = 10 micrograms/ml-1 for cephalexin, and < or = 50 micrograms/ml-1 for kanamycin. Antibiotic resistance among N. gonorrhoeae isolates from Tucumán, Argentina, appeared to be primarily limited to penicillin and tetracycline, which has been a general use against gonorrhoeae in Tucumán since 1960. Periodic monitoring of the underlying susceptibility profiles of the N. gonorrhoeae strains prevalent in areas of frequent transmission may provide clues regarding treatment options and emerging of drug resistance.