Clostridium difficile hospitalizations in Louisiana: a 10 year review.

Clostridium difficile (CD) is a common cause of diarrhea in hospitalized patients and can cause more serious intestinal conditions such as pseudomembranous colitis, toxic megacolon, perforations of the colon, sepsis, and even death. Clostridium difficile associated disease (CDAD) is mainly a health care associated illness. Known risk factors for CDAD are antibiotics, gastrointestinal surgery/manipulation, long length of stay in health care settings, serious underlying illness, a compromised immune system, and advanced age (>65+). In 2004 a new epidemic strain of CD was identified as causing hospital outbreaks in several states. This new strain is more virulent and is more resistant to fluoroquinolone antibiotics. The Healthcare Cost and Utilization Project (HCUP) analyzed hospitalization discharge rates of CDAD in the United States (US) between 1993 and 2005 and reported that hospital discharges for CDAD doubled between 2001 and 2005. This study was done to see if Louisiana had similar trends in CDAD rates compared to the rest of the nation. Discharge records from the Louisiana Hospital Inpatient Discharge Database (LAHIDD) were analyzed for CDAD rates between 1999 and 2008 and were compared to the HCUPnet national estimates in the US. Trend and variance analyses were performed to compare demographics within Louisiana and overall trends to the US. Our results show that Louisiana had similar trends of CDAD rates compared to the US over the past 10 years. Furthermore, Louisiana also had a doubling of CDAD rates from 2001 to 2005.

Hormones, performance and fitness: Natural history and endocrine experiments on a lizard (Sceloporus undulatus).

We used the "morphology-performance-fitness" paradigm (Arnold, 1983) as our framework to investigate endocrine control of performance and fitness in Sceloporus undulatus (Eastern Fence Lizard). Focusing on males, we used the "natural experiments" of seasonal, sexual, and developmental variation in growth and in exercise endurance to identify testosterone and corticosterone as potential modulators of performance and related traits of interest. We followed with experimental manipulations of testosterone to investigate functional relationships, both in the laboratory and in the field. Further, we used focal observations and demographic studies, coupled with genetic determination of paternity, to test associations between performance and fitness, measured as reproductive success. We found that in males, endurance and plasma concentrations of testosterone and corticosterone are at their peaks in the spring breeding season, when lizards are most actively engaged in patrolling home ranges and in reproductive behavior. At that time, plasma concentrations of testosterone are correlated with body size; plasma concentrations of corticosterone and parameters of home range, including area and the number of overlapped females, are correlated with home-range overlap between males and females. During prereproductive development, males (but not females) experience a maturational increase in plasma testosterone. At about the same time, they become more active, expand their home ranges, and grow less quickly than do females, suggesting a trade-off in the allocation of energy, mediated by testosterone. Experimentally, testosterone has positive effects on fitness by stimulating endurance and reproductive activity and increasing home-range area, but it exacts costs in fitness by increasing ectoparasitism, decreasing growth, and decreasing survivorship. We found evidence of selection on body size, endurance, and home-range size (and thus access to potential mates). Despite having positive effects on performance traits, plasma concentrations of testosterone were not correlated with number of offspring sired by males. However, we found a strong correlation between the level of plasma corticosterone and the number of offspring sired. We also found evidence of size-assortative mating, indicating that for males, both the number and the size (and thus, fecundity) of their mates increase with body size. Our studies exemplify the power of natural history combined with experimental endocrine manipulations to identify hormonal regulators of performance and linkages to fitness. Furthermore, our results illustrate ecological and evolutionary significance of individual variation in endocrine traits.

Testosterone and group size in cliff swallows: testing the "challenge hypothesis" in a colonial bird.

The "challenge hypothesis" states that increases in testosterone levels of male animals during the breeding season are directly related to the extent of intrasexual competition for resources or mates that they experience. Although often tested in territorial species, the challenge hypothesis has not been evaluated for colonial animals that live in groups of different sizes and that thus experience different intensities of intrasexual competition. We measured circulating testosterone levels of male and female cliff swallows (Petrochelidon pyrrhonota) in southwestern Nebraska, where these birds nest in colonies of widely different sizes. Males had significantly higher testosterone levels than females, as expected. For males especially, there was a seasonal rise in testosterone levels early in the nesting cycle, corresponding to the period when birds were establishing nest ownership and egg laying, and then a fall as they switched to parental duties. Testosterone levels varied significantly with colony size; for both sexes, birds in larger colonies had higher levels of testosterone than those in smaller colonies when controlling for date. Age and body mass were not related to testosterone levels. Higher levels of testosterone for birds of both sexes in larger colonies probably reflect greater competition for matings, often extra pair, in the more social nesting situations. The results support the predictions of the challenge hypothesis.

Effects of testosterone treatment and season on the frequency of dewlap extensions during male-male interactions in the lizard Anolis sagrei.

Lizards of the genus Anolis extend and retract a large and often brightly colored throat fan called a dewlap. The dewlap in most anoles is a sexually dimorphic structure. It is larger in males than females and males use the dewlap more frequently and in more contexts than do females. In the present study we investigated whether plasma testosterone (T) levels and season affect the frequency of dewlap use in male--male interactions in the brown anole, Anolis sagrei. We manipulated plasma T levels by implanting adult, castrated males with pellets that delivered no T, a moderate dose of T, or a high dose of T. In tests with stimulus males, castrated males that were treated with a moderate or with a high dose of T had a significantly higher frequency of dewlap extensions than did castrated males that received no T. However, the frequency of dewlap extensions in castrated males that received the high dose of T did not differ significantly from castrated males that received the moderate dose of T or from non-castrated control males. Males captured during the breeding season and tested in the laboratory had a significantly higher frequency of dewlap extensions than did males captured in the postbreeding season and tested in the same manner. These results suggest that plasma T levels affect how frequently males of A. sagrei extend their dewlaps in male--male interactions and that seasonal changes in male dewlap use may be due to seasonal differences in plasma T levels.