The Evaluation of Methicillin Resistance in Staphylococcus aboard the International Space Station

The International Space Station (ISS) represents a semi-closed environment with a high level of crewmember interaction. As community-acquired methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a health concern in environments with susceptible hosts in close proximity, an evaluation of isolates of clinical and environmental Staphylococcus aureus and coagulase negative Staphylococcus was performed to determine if this trend was also present in astronauts aboard ISS or the space station itself. Rep-PCR fingerprinting analysis of archived ISS isolates confirmed our earlier studies indicating a transfer of S. aureus between crewmembers. In addition, this fingerprinting also indicated a transfer between crewmembers and their environment. While a variety of S. aureus were identified from both the crewmembers and the environment, phenotypic evaluations indicated minimal methicillin resistance. However, positive results for the Penicillin Binding Protein, indicative of the presence of the mecA gene, were detected in multiple isolates of archived Staphylococcus epidermidis and Staphylococcus haemolyticus. Phenotypic analysis of these isolates confirmed their resistance to methicillin. While MRSA has not been isolated aboard ISS, the potential exists for the transfer of the gene, mecA, from coagulase negative environmental Staphylococcus to S. aureus creating MRSA strains. This study suggests the need to expand environmental monitoring aboard long duration exploration spacecraft to include antibiotic resistance profiling

(Table 2, Annex), Manganese crusts and manganese coated rocks recovered from study area (lat 26°N)

An asymmetric tectonic fabric was delineated by narrow-beam bathymetric profiles in a 180-km2 area of the Mid-Atlantic Ridge crest at lat 26°N. Features of the tectonic fabric are a continuous rift valley offset by small (<10-km) transform faults and minor fracture zones expressed as valleys with intervening ridges that trend normal and oblique to the two sides of the rift valley. The discharge zone of a postulated sub-sea-floor hydrothermal convection system is focused by faults on the southeast wall of the rift valley and driven by intrusive heat sources beneath the rift valley. The rift valley has a double structure consisting of linear segments, bounded by ridges, and basins at the intersections of the minor fracture zones. The double structure of the rift valley acts like a template that programs the reproduction of the tectonic fabric. The minor fracture zones form an asymmetric V about the rift valley at variance with the symmetric small circles formed by major fracture zones. To reconcile the asymmetry of minor fracture zones with the symmetry of major fracture zones, it is proposed that the minor fracture zones have been preferentially reoriented by an external stress field attributed to interplate and intraplate motions. Major fracture zones remain symmetric under the same stress field owing to differential stability between minor and major structures of oceanic lithosphere

Seismicity and tectonics of the southeastern Caribbean.

We present 33 new focal mechanisms for SE Caribbean earthquakes (1963–1988). We use these mechanisms, in conjunction with 28 previously available mechanisms, to distinguish between two models of plate boundary zone interaction in the SE Caribbean: the trench-trench transform and hinge faulting model, and the right oblique collision model. Shallow (0–70 km) and intermediate (70–200 km) depth earthquakes occur in the study region; we focus on the tectonic causes of these events and the motions they delineate. The shallow earthquakes are in a broad linear zone which trends NE from the Paria Peninsula of Venezuela towards Barbados. Intermediate depth earthquakes cluster beneath and NW of the Peninsula, and deepen to the NW, perpendicular to the NE-trending shallow events. The vertical distribution of the earthquakes suggests a slab with steep NW dip. Shallow, dextral strike slip on E-striking faults is restricted to a 60-km-wide linear zone between the Gulf of Cariaco and the western margin of the Gulf of Paria. Dextral strike slip is active only as far east as the Gulf of Paria, and not within or east of Trinidad. Shallow thrust events with ENE-striking planes, distributed between the Araya Peninsula and the Gulf of Paria, indicate collision at crustal levels between South America and Caribbean, and that folding and thrusting are still active over a 60-km interval south of the Araya-Paria isthmus. Active thrusting in Venezuela corroborates predictions of transpression between Caribbean and South America and discounts transtensional motions between the two plates in the SE Caribbean. The conjunction of shallow thrust, strike slip, and normal earthquakes in the Gulf of Paria at around 62.3° may be the expression of unpartitioned oblique compressive deformation in the plate boundary zone. Intermediate (165 km > h > 70 km) depth thrust and dip slip events within the NW-dipping slab indicate that oceanic lithosphere, probably originally attached to South America, subducts to the NW beneath the Caribbean plate. Shallow normal faulting events E and NE of Trinidad are expressions of plate bending about near-horizontal axes parallel to the Lesser Antilles subduction zone. We conclude that the earthquake mechanisms provide strong support for the right oblique collision model of Caribbean-South American plate interaction