The antimicrobial susceptibility and mechanisms of resistance of 109 Shigella and 40 Salmonella isolates from children with diarrhea in southern Mozambique were assessed. The susceptibility to seven antimicrobial agents was tested by disk diffusion, and mechanisms of resistance were searched by PCR or colorimetric method. A high proportion of Shigella isolates were resistant to chloramphenicol (Chl) (52%), ampicillin (Amp) (56%), tetracycline (Tet) (66%), and trimethoprim-sulfamethoxazole (Sxt) (84%). Sixty-five percent of the isolates were multidrug resistant. Shigella flexneri isolates were more resistant than those of Shigella sonnei to Amp (66% versus 0.0%, P < 0.001) and Chl (61% versus 0.0%, P < 0.001), whereas S. sonnei isolates presented higher resistance to Tet than S. flexneri isolates (93% versus 64%, P ‫؍‬ 0.02). Resistance among Salmonella isolates was as follows: Tet and Chl, 15% each; Sxt, 18%; and Amp, 25%. Only 3% of Salmonella isolates were resistant to nalidixic acid (Nal), and none to ciprofloxacin or ceftriaxone (Cro). Among Salmonella isolates, multiresistance was found in 23%. Among Shigella isolates, antibiotic resistance was related mainly to the presence of oxa-1-like ␤-lactamases for Amp, dfrA1 genes for Sxt, tetB genes for Tet, and Chl acetyltransferase (CAT) activity for Chl. Among Salmonella isolates, resistance was conferred by tem-like ␤-lactamases for Amp, floR genes and CAT activity for Chl, tetA genes for Tet, and dfrA1 genes for Sxt. Our data show that Shigella isolates are resistant mostly to the most available, inexpensive antibiotics by various molecular mechanisms but remain susceptible to ciprofloxacin, Cro, and Nal, which is the first line for empirical treatment of shigellosis in the country.

Liver transplantation (LT) of hepatitis C virus (HCV)-infected grafts into HCV-infected recipients leads to superinfection with two different virus strains. To characterize the virological outcomes of HCV superinfection immediately after LT, we performed phylogenetic analysis of a fragment of the NS5B gene in donor and recipient serum samples prospectively collected before and after LT, starting on day 1. In four of six cases, the donor strain finally prevailed, while in the remaining two cases, the native recipient strain overtook the donor quasispecies. Clonal sequence analysis showed that, in three cases, the expelled strain was undetectable 1 day after LT. Our study shows that superinfection with a different HCV strain can lead to the exclusion of one strain by the other as soon as the first day after LT. This would suggest that competition might not be limited to the replication level, but could also take place during virus entry.Hepatitis C virus (HCV) infects an estimated 170 million individuals worldwide, with approximately 3 million individuals newly infected each year (Lavanchy, 2009). HCV displays a high rate of genetic variability and has been classified into six major genotypes (genotypes 1-6) and numerous subtypes (Kuiken & Simmonds, 2009). In addition, in a single infected individual, HCV circulates as a complex population of closely related genomes referred to as quasispecies (Forns et al., 1999; Martell et al., 1992).Chronic infection develops in 50-80 % of infected individuals; HCV chronic carriers are at increased risk of developing cirrhosis and hepatocellular carcinoma. Thus, HCV is the leading indication of liver transplantation (LT) in the Western world and Japan. Regrettably, the demand for liver transplants exceeds the organ supply. One approach to expand the pool of organs for transplantation is to use grafts from extended-criteria donors, such as HCV-positive donors. Several studies have reported no differences in outcomes with the use of HCV-positive grafts in comparison with the use of non-infected grafts (Marroquin et al., 2001;Vargas et al., 1999;Velidedeoglu et al., 2004), although donor age has recently been recognized to play an important role after transplantation with HCV-positive grafts (Khapra et al., 2006). In addition, it is important to note that grafts from genotype 1 donors should not be allocated to recipients infected with genotypes 2 or 3, in which antiviral therapy is significantly more effective than for genotype 1, and the introduction of the latter genotype may be detrimental for the patient's outcome.HCV superinfection refers to infection with a different HCV strain in an individual already infected with HCV. This phenomenon has been reported in experimentally infected chimpanzees (Farci et al., 1992; Okamoto et al., 1994; Prince et al., 1992) and in individuals at a very high risk for infection, such as intravenous drug users, haemophiliacs or patients on haemodialysis, and multitransfused patients before the screening of HCV in the blood donor population (Ey...