Resistant pathogens in biliary obstruction: Importance of cultures to guide antibiotic therapy

Background . Cholangitis, infection of the bile ducts, is a serious condition that necessitates prompt and efficacious treatment for a good clinical outcome. A single center retrospective study of cholangitis was conducted to better define the spectrum of responsible pathogens and their antibiotic sensitivities. Methods . We studied all patients at our hospital who had cholangitis from January 1998 to June 2004. Patients were identified by ICD-9 codes and the cause of the cholangitis, the treatment and culture data were noted by review of the medical record. Results . Thirty patients presented with cholangitis as noted by the clinical symptoms of jaundice, fever and abdominal pain. The cause of the biliary obstruction was gallstones in 18 patients, benign biliary strictures in 5 and malignant obstruction in 7. All the patients with malignant obstruction with cholangitis had stents; there were no cases of cholangitis in malignant obstruction unless prior instrumentation had been performed. The most common isolates were Enterococcus>E. coli>Enterobacter>Klebsiella. Sixty-four percent of blood cultures and all but one of the bile cultures grew organisms. Seventy-two percent of patients had positive blood cultures with at least one resistant organism present and 36% had organisms resistant to multiple antibiotics. Fifty percent of patients with benign biliary disease and positive blood cultures had multiple organisms growing in their blood. Three-quarters of the isolates were resistant to one or more antibiotics and one-quarter of isolates were resistant to three or more antibiotics. Resistant organisms were found regardless of the cause of the biliary obstruction. Discussion . For all causes of cholangitis, there is a high incidence of positive blood cultures and a high rate of antibiotic resistance. For optimal treatment, blood and/or bile cultures should be routinely performed to optimize antibiotic therapy.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73375/1/13651820510028792.pd

Quantifying the effects of temperature on mosquito and parasite traits that determine the transmission potential of human malaria

Malaria transmission is known to be strongly impacted by temperature. The current understanding of how temperature affects mosquito and parasite life history traits derives from a limited number of empirical studies. These studies, some dating back to the early part of last century, are often poorly controlled, have limited replication, explore a narrow range of temperatures, and use a mixture of parasite and mosquito species. Here, we use a single pairing of the Asian mosquito vector, An. stephensi and the human malaria parasite, P. falciparum to conduct a comprehensive evaluation of the thermal performance curves of a range of mosquito and parasite traits relevant to transmission. We show that biting rate, adult mortality rate, parasite development rate, and vector competence are temperature sensitive. Importantly, we find qualitative and quantitative differences to the assumed temperature-dependent relationships. To explore the overall implications of temperature for transmission, we first use a standard model of relative vectorial capacity. This approach suggests a temperature optimum for transmission of 29°C, with minimum and maximum temperatures of 12°C and 38°C, respectively. However, the robustness of the vectorial capacity approach is challenged by the fact that the empirical data violate several of the model's simplifying assumptions. Accordingly, we present an alternative model of relative force of infection that better captures the observed biology of the vector-parasite interaction. This model suggests a temperature optimum for transmission of 26°C, with a minimum and maximum of 17°C and 35°C, respectively. The differences between the models lead to potentially divergent predictions for the potential impacts of current and future climate change on malaria transmission. The study provides a framework for more detailed, system-specific studies that are essential to develop an improved understanding on the effects of temperature on malaria transmission