Parallel Epidemics of Community-Associated Methicillin-Resistant Staphylococcus aureus USA300 Infection in North and South America.

BACKGROUND: The community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) epidemic in the United States is attributed to the spread of the USA300 clone. An epidemic of CA-MRSA closely related to USA300 has occurred in northern South America (USA300 Latin-American variant, USA300-LV). Using phylogenomic analysis, we aimed to understand the relationships between these 2 epidemics. METHODS: We sequenced the genomes of 51 MRSA clinical isolates collected between 1999 and 2012 from the United States, Colombia, Venezuela, and Ecuador. Phylogenetic analysis was used to infer the relationships and times since the divergence of the major clades. RESULTS: Phylogenetic analyses revealed 2 dominant clades that segregated by geographical region, had a putative common ancestor in 1975, and originated in 1989, in North America, and in 1985, in South America. Emergence of these parallel epidemics coincides with the independent acquisition of the arginine catabolic mobile element (ACME) in North American isolates and a novel copper and mercury resistance (COMER) mobile element in South American isolates. CONCLUSIONS: Our results reveal the existence of 2 parallel USA300 epidemics that shared a recent common ancestor. The simultaneous rapid dissemination of these 2 epidemic clades suggests the presence of shared, potentially convergent adaptations that enhance fitness and ability to spread.

Range Expansion and the Origin of USA300 North American Epidemic Methicillin-Resistant Staphylococcus aureus.

The USA300 North American epidemic (USA300-NAE) clone of methicillin-resistant Staphylococcus aureus has caused a wave of severe skin and soft tissue infections in the United States since it emerged in the early 2000s, but its geographic origin is obscure. Here we use the population genomic signatures expected from the serial founder effects of a geographic range expansion to infer the origin of USA300-NAE and identify polymorphisms associated with its spread. Genome sequences from 357 isolates from 22 U.S. states and territories and seven other countries are compared. We observe two significant signatures of range expansion, including decreases in genetic diversity and increases in derived allele frequency with geographic distance from the Pennsylvania region. These signatures account for approximately half of the core nucleotide variation of this clone, occur genome wide, and are robust to heterogeneity in temporal sampling of isolates, human population density, and recombination detection methods. The potential for positive selection of a gyrA fluoroquinolone resistance allele and several intergenic regions, along with a 2.4 times higher recombination rate in a resistant subclade, is noted. These results are the first to show a pattern of genetic variation that is consistent with a range expansion of an epidemic bacterial clone, and they highlight a rarely considered but potentially common mechanism by which genetic drift may profoundly influence bacterial genetic variation.IMPORTANCE The process of geographic spread of an origin population by a series of smaller populations can result in distinctive patterns of genetic variation. We detect these patterns for the first time with an epidemic bacterial clone and use them to uncover the clone's geographic origin and variants associated with its spread. We study the USA300 clone of methicillin-resistant Staphylococcus aureus, which was first noticed in the early 2000s and subsequently became the leading cause of skin and soft tissue infections in the United States. The eastern United States is the most likely origin of epidemic USA300. Relatively few variants, which include an antibiotic resistance mutation, have persisted during this clone's spread. Our study suggests that an early chapter in the genetic history of this epidemic bacterial clone was greatly influenced by random subsampling of isolates during the clone's geographic spread.

Single low-dose mebendazole administered quarterly for ascaris treatment.

BACKGROUND: Intestinal parasites are difficult to eradicate in tropical climates where poor sanitation exists. In addition, pharmaceutical stability is poor making traditional three day dosing for the treatment of A. lumricoides challenging. METHODS: Single 100 mg doses of mebendazole were administered to persons living along Amazon tributaries in Northeastern Peru. Directly-observed treatment was repeated at 3-month intervals over a 2-year period in a single treatment village. Treatment was repeated at 12-month intervals in the remaining (control) villages. Treatment was accompanied by a regimen of multivitamins with iron to be taken daily for 14 days after each treatment. Subjects were screened for ova and parasites prior to treatment and at 1-year intervals. In addition to A. lumbricoides, other parasites found on screening were recorded. RESULTS: Treatment resulted in a 92.5% cure rate for A. lumbricoides at the 2-year assessment. Growth and development assessments demonstrated fewer individuals below the 3 percentile for age-adjusted measurements when treated quarterly. CONCLUSIONS: Based on these limited data, single low-dose mebendazole administered quarterly appears to have a positive effect on the health of isolated village populations in the Amazon River basin.

Evaluation of a positive yeast-in-blood service.

BACKGROUND: The purpose of this study was to evaluate the effect of a novel "yeast-in-blood" surveillance service on the timeliness of antifungal chemotherapy for candidemia. METHODS: Two hundred seven blood cultures positive for Candida species between July 1, 1994, and February 15, 2009, as identified by the microbiology positive culture log, were included in this retrospective chart review. Patients with a positive culture before July 1, 2008, were evaluated by the yeast-in-blood surveillance service and included as intervention cases (IC). After this time, those occurring after discontinuation of the service were included as nonintervention cases (NIC). The primary outcome measure was the time to antifungal therapy from the time of blood culture draw. Secondary outcome measures included antifungal selection and time to antifungal prescription order from culture positivity. RESULTS: Median time to therapy was 58.9±28.4 hours and 41.3±30.5 hours for NIC and IC, respectively (P=0.001). Median time to prescription order was 3.0±6.9 hours for NIC versus 1.9±3.9 hours for IC. Candida albicans was the predominant organism identified (45.3% of NIC and 54.6% of IC). Treatment agents included an azole in 57.4% of NIC and 47.4% of IC, an echinocandin in 33.3% and 27.3% and a polyene in 5.7% and 27.8%, respectively. CONCLUSIONS: Time to therapy and time to prescription were shorter in those evaluated by the surveillance service. These data suggest that a yeast surveillance service improves antifungal medication therapy initiation.