Impact of zooplankton grazing on the excystation, viability, and infectivity of the protozoan pathogens Cryptosporidium parvum and Giardia lamblia.

Very little is known about the ability of the zooplankton grazer Daphnia pulicaria to reduce populations of Giardia lamblia cysts and Cryptosporidium parvum oocysts in surface waters. The potential for D. pulicaria to act as a biological filter of C. parvum and G. lamblia was tested under three grazing pressures (one, two, or four D. pulicaria grazers per 66 ml). (Oo)cysts (1 x 10(4) per 66 ml) were added to each grazing bottle along with the algal food Selenastrum capricornutum (6.6 x 10(4) cells per 66 ml) to stimulate normal grazing. Bottles were rotated (2 rpm) to prevent settling of (oo)cysts and algae for 24 h (a light:dark cycle of 16 h:8 h) at 20 degrees C. The impact of D. pulicaria grazing on (oo)cysts was assessed by (i) (oo)cyst clearance rates, (ii) (oo)cyst viability, (iii) (oo)cyst excystation, and (iv) oocyst infectivity in cell culture. Two D. pulicaria grazers significantly decreased the total number of C. parvum oocysts by 52% and G. lamblia cysts by 44%. Furthermore, two D. pulicaria grazers significantly decreased C. parvum excystation and infectivity by 5% and 87%, respectively. Two D. pulicaria grazers significantly decreased the viability of G. lamblia cysts by 52%, but analysis of G. lamblia excystation was confounded by observed mechanical disruption of the cysts after grazing. No mechanical disruption of the C. parvum oocysts was observed, presumably due to their smaller size. The data provide strong evidence that zooplankton grazers have the potential to substantially decrease the population of infectious C. parvum and G. lamblia in freshwater ecosystems.

Multidrug-resistant tuberculosis in pregnancy: case report and review of the literature.

A woman at 23 weeks' gestation was treated with rifampin, isoniazid, and ethambutol for cavitary tuberculosis (TB). She did not respond within 3 weeks, and multidrug-resistant (MDR) TB was suspected. Direct plating on susceptibility media was performed immediately. Treatment was initiated with IV capreomycin, levofloxacin, para-aminosalicylic acid, pyrazinamide, cycloserine, and high-dose vitamin B(6) at 26 weeks' gestation. The patient delivered vaginally at week 35. The newborn was not infected. Following delivery, ethionamide was added as a sixth drug, and levofloxacin was replaced with moxifloxacin. The patient's sputum became smear-negative and culture-negative for TB. All reported cases of MDR-TB during pregnancy are reviewed.