Use of pulsed-field gel electrophoresis in surveillance of Salmonella in Houston, Texas

Background. Pulsed-field gel electrophoresis (PFGE) is a laboratory technique in which Salmonella DNA banding patterns are used as molecular fingerprints for epidemiologic study for "PFGE clusters". State and national health departments (CDC) use PFGE to detect clusters of related cases and to discover common sources of bacteria in outbreaks. ^ Objectives. Using Houston Department of Health and Human Services (HDHHS) data, the study sought: (1) to describe the epidemiology of Salmonella in Houston, with PFGE subtype as a variable; and (2) to determine whether PFGE patterns and clusters detected in Houston were local appearances of PFGE patterns or clusters that occurred statewide. ^ Methods. During the years 2002 to 2005, the HDHHS collected and analyzed data from routine surveillance of Salmonella. We implemented a protocol, between May 1, 2007 and December 31, 2007, in which PFGE patterns from local cases were sent via e-mail to the Texas Department of State Health Services, to verify whether the local PFGE patterns were also part of statewide clusters. PFGE was performed from 106 patients providing a sample from which Salmonella was isolated in that time period. Local PFGE clusters were investigated, with the enhanced picture obtained by linking local PFGE patterns to PFGE patterns at the state and national level. ^ Results. We found that, during the years 2002 to 2005, there were 66 PFGE clusters, ranging in size from 2 to 22 patients within each cluster. Between different serotypes, there were marked differences in the sizes of PFGE clusters. A common source or risk factor was found in fewer than 5 of the 66 PFGE clusters. With the revised protocol, we found that 19 of 66 local PFGE patterns were indistinguishable from PFGE patterns at Texas DSHS. During the eight months, we identified ten local PFGE clusters with a total of 42 patients. The PFGE pattern for eight of the ten clusters matched the PFGE patterns for cases reported to Texas DSHS from other geographic areas. Five of the ten PFGE patterns matched PFGE patterns for clusters under investigation at PulseNet at the national level. HDHHS epidemiologists identified a mode of transmission in two of the ten local clusters and a common risk factor in a third local cluster. ^ Conclusion. In the extended-study protocol, Houston PFGE patterns were linked to patterns seen at the state and national level. The investigation of PFGE clusters was more efficacious in detecting a common transmission when local data were linked to state and national data. ^

(Table T1) Magnetic anisotropy of samples from ODP Hole 180-1117A

At Site 1117, drilled during Leg 180 of the Ocean Drilling Program in the Woodlark Basin, we cored a fault zone and recovered fault gouge, mylonitized and brecciated gabbros, and undeformed gabbro. We measured the anisotropy of magnetic susceptibility for the rock samples. The susceptibilities of the fault gouge samples were lower than those of the undeformed gabbro, and those of deformed gabbros were lowest. The anisotropy degrees of the fault gouge samples were higher than those of the deformed and undeformed gabbros. Oblate magnetic fabrics were dominant in the samples from the fault zone.

Magnetic properties of plutonic rocks at DSDP Leg 82 holes

Ten samples of gabbro and peridotite, with varying degrees of serpentinization, were studied by magnetic techniques and reflected light microscopy. Evidence from these methods suggests that the natural remanent magnetization is primarily of chemical origin. It is generally weak for the gabbros and much stronger for the peridotites. This difference is offset by the fact that the peridotites have generally lower magnetic stability and Koenigsberger ratios. There is a considerable variation in both magnetic parameters and petrology even among closely spaced samples, which suggests that some combination of source heterogeneity and tectonic mixing was involved in the production of these rocks. However, the small number of samples makes this conclusion tentative. There may also have been significant postemplacement alteration involved. All samples show a significant anisotropy of weak field susceptibility that appears to be related to deformation. This anisotropy may be useful in defining petrofabrics.