Impairment of Intramacrophagic Brucella suis Multiplication by Human Natural Killer Cells through a Contact-Dependent Mechanism

Brucella spp. are facultative intracellular bacteria that can establish themselves and cause chronic disease in humans and animals. NK cells play a key role in host defense. They are implicated in an early immune response to a variety of pathogens. However, it was shown that they do not control Brucella infection in mice. On the other hand, NK cell activity is impaired in patients with acute brucellosis, and recently it was demonstrated that human NK cells mediate the killing of intramacrophagic Mycobacterium tuberculosis in in vitro infection. Therefore, we have analyzed the behavior of Brucella suis infecting isolated human macrophages in the presence of syngeneic NK cells. We show that (i) NK cells impair the intramacrophagic development of B. suis, a phenomenon enhanced by NK cell activators, such as interleukin-2; (ii) NK cells cultured in the presence of infected macrophages are highly activated and secrete gamma interferon and tumor necrosis factor alpha; (iii) impairment of bacterial multiplication inside infected cells is marginally associated with the cytokines produced during the early phase of macrophage-NK cell cocultures; (iv) direct cell-to-cell contact is required for NK cells to mediate the inhibition of B. suis development; and (v) inhibition of B. suis development results from an induction of NK cell cytotoxicity against infected macrophages. Altogether, these findings show that NK cells could participate early in controlling the intramacrophagic development of B. suis in humans. It seems thus reasonable to hypothesize a role for NK cells in the control of human brucellosis. However, by impairing the activity of these cells in the acute phase of the illness, the pathogen should avoid this control

Antimicrobial Susceptibility of Bacteria and Yeasts Isolated from the Milk of Dairy Cattle Presenting with Subclinical Mastitis in Puebla, Mexico

"This study was designed to identify the bacteria and yeasts from the milk samples of dairy cattle presenting with subclinical mastitis and evaluate their antimicrobial susceptibility. We collected a total of 52 milk samples from cows across three farms in San Salvador El Seco (Puebla, Mexico). Microbial isolation was performed using microbiological techniques followed by taxonomic identification of bacteria and yeasts. Antimicrobial susceptibility was evaluated using the guidelines provided by the Clinical Laboratory Standard Institute (CLSI). 1 We identified three genera and six species of yeasts including Candida glabrata, C. krusei, C. lipolytica, Cryptococcus laurentii, Rhodotorula rubra, and R. glutinis and five species of bacteria, including Staphylococcus saprophyticus, S. aureus, S. hominis, S. epidermidis, and Streptococcus disgalactiae. All of the yeast strains were sensitive to amphotericin B; 1/23 (4.3%) were resistant to ketoconazole and nystatin, 10/23 (43%) were resistant to fluconazole, and 13/23 (53%) were resistant to 5-fluorocytosine. The dominant genus isolated was Candida, with the most abundant groups being C glabrata and C. krusei. Resistance to 5-fluorocytosine was observed in all yeasts except C. lipolytica, while both S. aureus and S. epidermidis were resistant to oxacillin and dicloxacillin. S. hominis was resistant to gentamicin"

Results of Geothermal Gradient Core Hole TCB-1, Tecuamburro Volcano Geothermal Site, Guatemala, Central America

Results of geological, volcanological, hydrogeochemical, and geophysical field studies conducted in 1988 and 1989 at the Tecuamburro volcano geothermal site in Guatemala indicated that there is a substantial shallow heat source beneath the area of youngest volcanism. To obtain information on subsurface temperatures and temperature gradients, stratigraphy, hydrothermal alteration, fracturing, and possible inflows of hydrothermal fluids, a geothermal gradient core hole (TCB-1) was drilled to 808 m low on the northern flank of the Tecuamburro volcano Complex, 300 km south of a 300-m-diameter phreatic crater, Laguna Ixpaco, dated at 2,910 years. Gases from acid-sulfate springs near Laguna Ixpaco consistently yield maximum estimated subsurface temperatures of 250--300{degrees}C. The temperature versus depth curve from TCB-1 does not show isothermal conditions and the calculated thermal gradients from 500--800 m is 230{degrees}C/km. Bottom hole temperature is 238{degrees}C. Calculated heat flow values are nearly 9 heat flow units (HFU). The integration of results from the TCB-1 gradient core hole with results from field studies provides strong evidence that the Tecuamburro area holds great promise for containing a commercial geothermal resource