Revista latinoamericana de microbiologia最新文献

The bacteriocin PsVP-10 is a 2.6 Kda peptide which was isolated and purified from Pseudomonas sp. This bacteriocin possesses lethal activity over Enterococcus faecalis, Salmonella typhimurium and Shigella flexneri. The experimental assays showed that the bacteriocin is able to be adsorbed by all cells of these bacterial species and also by their isolated cell walls. It was observed that the resistant mutants and their respective cell walls are unable to adsorb the bacteriocin. Assays performed with spheroplasts obtained from sensitive bacterial species and their resistant mutants show a rapid lethal effect of the bacteriocin PsVP-10. This results indicated furthermore, it is also shown that the optimal pH and temperature for the adsorption were 7.2 and 37 degrees C, respectively. The study carried out with organic solvents like methanol, ethanol, isopropanol and the detergents sodium dodecyl sulfate and triton X-100 showed a moderate inhibition of the bacteriocin lethal action for the Gram negative cells. The enzymes lysozime, protease XIV and trypsine type III-S did not present any effect over the adsorption capacity of the bacteriocin with any of the bacterial species studied.

The growth and the extracellular amylase production by Aspergillus ochraceus were studied in a stationary culture medium. Maximum growth rate of this fungus was found after 5 days of incubation at 30 degrees C, but maximum amylase production was obtained after 2 days. The highest amylase production were attained with lactose, maltose, xylose and starch as carbon sources. The extracellular amylase production and mycelial growth were influenced by the concentration of starch. Other carbohydrates supported growth but did not induce amylase synthesis and glucose repressed it, indicating catabolite repression in this microorganism. The presence of both mechanisms of induction and repression suggests that at least these multiple forms of regulation are present in A. ochraceus. Of the nitrogen sources tested, casaminoacids, ammonium nitrate and sodium nitrate stimulated the highest yield of amylase. Optimal amylase production was obtained at pH 5.0, but enzyme activity was found only in the 4.0-6.0 pH range. These results were probably due to the inhibitory effect of NH4(+)-N in the culture medium.

Entamoeba histolytica is the pathogenic species of Entamoeba that causes amoebic dysentery and other invasive disease. The morphologically similar species, E. dispar, is non-pathogenic and accounts for about 90% of the previously estimated 500 million E. histolytica infections world-wide. Because of the recent redefinition of E. histolytica and E. dispar, and the limited number of drugs available to treat amoebiasis, a new approach to treatment of individuals carrying these parasites is necessary. A meeting of eminent scientists has recently agreed that on no account should prophylaxis against amoebiasis be given, and no treatment without symptoms should be administered. The expense of treating asymptomatic individuals, both monetary and at the risk of over-use of precious drugs, does not appear to be justified. It would seem wise that we preserve currently effective anti-amoebic drugs and avoid the development of drug-resistant E. histolytica.

The aim of the present study was to determine the presence of Borrelia burgdorferi antibodies in horses from the metropolitan area of Monterrey, Nuevo León, México. Blood serum was obtained from a total of 100 horses residing at different counties in the area. From each animal data was obtained on age, sex, county of residence, presence of ectoparasites and clinical signs. All sera samples were analyzed by indirect immunofluoresence and the sera that resulted positive to this test was analyzed by Western blot. The serological test yielded 34 positive sera at 1:64 dilution, and from them 6 were positive at 1:128 dilution, 3 at 1:256, and only one at 1:512. Confirmation of the infection by Western blot was obtained only in the sample positive at the 1:512 dilution. These results shown a low frequency of seropositivity to B. burgdorferi of the horses in the area, confirming previous studies indicating that in northeast Mexico Lyme disease is present in different animal species.

In this work, culture filtrates of entomopathogenic and phytopathogenic Serratia marcescens strains induced cytotoxic effects on CHO, Vero and HEp-2 cell lines. Morphological changes on sensitive cells were characterized by cell rounding and detachment as soon as 30 min of incubation, culminating in cell death after 24 h. The cytotoxic effect was completely neutralized by specific antiserum indicating that occur antigenic similarity among cytotoxins produced by these strains. The toxicity assays on plants showed that the culture supernatants did not provoke any visible morphological change and did not affect their growth. By contrast, the plants treated with bacterial suspension showed disease symptom, such as shriveling and decay of stores bulbus in onion and lettuce plantlets. In conclusion, this study show that phytopathogenic and entomopathogenic S. marcescens may produce a cytototoxin similar to that produced by clinical isolates and it is toxic to different mammalian cell lines. These results are especially important for studies involving this bacterium as biological control agent.

Lactic acid production is considered to be the major protection mechanism of lactobacilli against vaginal infections due to genital pathogens. However, some species of Lactobacillus are also hydrogen peroxide-producers. Women, who usually use intrauterine dispositive (IUD) and spermicides such as nonoxinol-9 (N-9) as contraceptive methods, increase the risk of acquiring an urinary tract infection and a bacterial vaginosis; some studies have demonstrated that these compounds alter the normal vaginal biota. It is known that they inhibit lactobacilli in vitro at concentrations of 0.1% to 1% and that they do not have an effect on the growth of Escherichia coli. It is probable that the presence of nonoxinol-9 affects the ecological balance of the vagina by inhibiting the protector lactobacilli. In this study, we identified Lactobacillus acidophilus, L. brevis, L. crispatus, L. fermentii and L. jensenii as the species most frequently isolated from women. Seventy-one hydrogen peroxide-producer strains and 48 strains resistant to the inhibitory effect of nonoxinol-9 were detected. L. brevis showed the highest number of resistant strains.

Sexually transmitted diseases (STD) are a group of transmittable diseases acquired fundamentally through sexual contact. STD are a social problem resulting from demographic explosion and changes in sexual conduct, which affects teenagers and adults of all socioeconomic strata. The goal of this work was to establish the actual state of the different STD within the studied population. Samples of vaginal fluids, endocervical materials and urethral exudates taken from 2,630 patients during five years were processed. 1,341 samples tested positive to one or more of the microorganisms, 1,099 corresponding to female patients and 242 to male patients. The microorganisms found in women were: Gardnerella vaginalis (39.1%), Candida albicans (21.3%), Trichomonas vaginalis (16.8%), Chlamydia trachomatis (11.5%); Neisseria gonorrhoeae (3.4%), Mycoplasma hominis (2.6%); Ureaplasma urealyticum (4.1%) and Treponema pallidum (1.6%). Associations were: Gardnerella vaginalis with Trichomonas vaginalis (6%), Gardnerella vaginalis with Candida albicans (5.1%); Trichomonas vaginalis with Neisseria gonorrhoeae (2.2%) and Gardnerella vaginalis with Chlamydia trachomatis (2.1%). In men, gonococcic urethritis represented 37.8%, non-gonococcic urethritis 55.4% and Treponema pallidum 6.8%. A decrease in syphilis, gonococcic urethritis and gonococcic cervicitis was observed, increasing the prevalence of non-gonococcic urethritis and cervicitis. This study showed that in our environment the actual tendency of STD is still high.

Cytomegalovirus (CMV) infection in immunocompromised host is an important cause of morbidity and mortality. The protective immunity against the virus is both humoral and cellular. Immunologic mechanisms in rejection as in the immune response against CMV infection are similar but there is difficult to separe as histologic and clinically independent events. At least eight different genes of CMV are homologous to human proteins related to the immune response. The potential role of these genes with homology to human genes can be at different levels. The relevance that immunodominant antigens have on the natural control of CMV infection, suggests that the future design of a vaccine directed to protecting from disease those susceptible to primary infection, in an immunocompromised state, should involve a combination of antigens that include pp65, IE1-exon 4 and gB as a recombinant proteins.

Infection with Leishmania sp. is particularly suitable for the study of immunoregulatory mechanisms associated with host susceptibility or resistance. The clinical spectrum of this infection results from parasite virulence factors and host immune responses, some of which acting in a host protective manner while others exacerbate the disease. In the mouse model, factors governing resistance to Leishmania major infection mainly depends on the IFN-gamma activation of the leishmanicidal function of macrophages, and the Fas/ FasL-dependent T-cell cytotoxicity against infected macrophages. On the other hand, the immunological factors of susceptibility involve: I) the early upregulation of IL-4 production induced by the LACK antigen, II) the upregulation of IL-2 production, III) the high production of TGF-beta as macrophage deactivating factor, and IV) the production of IL-10 by the L. major infected macrophages, inhibited their microbicidal activity.

Biomphalaria glabrata is a fresh water snail of medical importance since it is the intermediate host of the trematode Schistosoma mansoni. The internal defense system of mollusks is mostly represented by circulating elements of the hemolymph (hemocytes). The infectivity of S. mansoni to B. glabrata is determined by genetic factors and evolutionary adaptations. In the present work factors about the parasite/snail relationship were evaluated, especially those related to the morphology and characteristics of the surface of cells present in the hemolymph of two strains of B. glabrata: a strain with high susceptibility to S. mansoni (Puerto Rico, PR) and a strain with medium susceptibility (Caripe, Ca). Hemolymph was collected by cephalopodal puncture; a total and a differential count of hemocytes were done in dyed preparations and through scanning electron microscopy (SEM). Results from both strains show a high quantitative variability of the total hemocyte count. Hemocytes dyed with May-Grünwald Giemsa showed cells with a basophilic nucleus predominantly in PR (61.7%), dense and strongly basophilic in Ca (71.2%) with significant differences between them. Through SEM round cells with a corrugated surface were observed (6-10microm), hemocytes with an irregular spongy surface (12microm), others with many projections (16microm) and cells not reported in similar to erythrocytes (21microm). Hemocytic cells from both strains confirmed cytoadherence and encapsulation were confirmed in the hemocytic cells from both strains, while no differences associated to the susceptibility of the strains were observed after 2 h of parasite-hemocyte incubation.