Clostridium difficile at a community hospital in the Bronx, New York: incidence prevalence and risk factors from 2006 to 2008.

BACKGROUND: The rate of Clostridium difficile has increased over the last decade. This study was undertaken to determine the incidence, prevalence, and risk factors for infection at a 460-bed community hospital in the Bronx, New York. METHOD: Retrospective study reviewing all patients with a positive stool test for C difficile toxin A/B from 2006 to 2008. RESULTS: Three hundred fifty-two stools were positive for toxin. Average age was 58 years; 4% of patients with stools positive for C difficile were asymptomatic; 7% had community-acquired infection; 57% of C difficile acquisition occurred in the hospital; and 36% were in patients who acquired C difficile from a health care facility prior to admission. The incidence of C difficile was 7.8 cases/10,000 days in 2006, 10.3 in 2007, and 9.7 in 2008. The prevalence was 6.2 cases per 1,000 admissions in 2006, 7.6 in 2007, and 7.0 in 2008. The increased prevalence was not uniform throughout the hospital. CONCLUSION: At a community hospital in the Bronx, the incidence of C difficile increased but at a lower rate than previously reported. Prior health facility contact accounted for one third of these cases. Rooms with clusters of patients with C difficile suggest environmental propagation of infection.

Development of PCR-Based Assays for Detecting Xanthomonas campestris pv. carotae, the Carrot Bacterial Leaf Blight Pathogen, from Different Substrates.

Detection of the carrot bacterial leaf blight pathogen, Xanthomonas campestris pv. carotae, was achieved using polymerase chain reaction (PCR) along with primer pairs developed from sequences of cloned random amplified polymorphic DNA (RAPD) fragments. Primer pairs 3S and 9B directed the amplification of ∼350-bp and ∼900-bp (or ∼2 kb) DNA fragments, respectively, from genomic DNA of all known X. campestris pv. carotae strains tested, but not from that of 13 other X. campestris pathovars or other bacterial species, including yellow non-xanthomonad bacteria isolated from carrot tissues and seeds. In tests conducted with an extensive collection of X. campestris pv. carotae-like strains isolated from different substrates from California, Idaho, Oregon, Washington, and Canada, the 3S primer pair directed the amplification of the ∼350-bp target fragment from all strains. These results indicated that the 3S primer pair is highly specific for X. campestris pv. carotae detection. Using the 3S primer pair, PCR assays were developed for detection of X. campestris pv. carotae from colonies on agar media, carrot leaf and stem tissues, and seeds. These tests could be performed in a single day. The PCR-based seed assay detected X. campestris pv. carotae from lots with contamination rates ranging from 2 × 102 to 2.3 × 108 CFU per gram of seed. This assay gave results similar to a seed-wash dilution plating assay and proved more sensitive than an enzyme-linked immunosorbent assay (ELISA)-based assay.

Seed Contamination Thresholds for Development of Carrot Bacterial Blight Caused by Xanthomonas campestris pv. carotae.

The relationship between levels of carrot (Daucus carota subsp. sativus) seed contamination with Xanthomonas campestris pv. carotae and (i) establishment of populations of X. campestris pv. carotae on carrot leaves and (ii) the incidence and severity of carrot bacterial blight was determined in field plots in Davis, California, in 1995 and 1996. Levels of seed contamination ranged from 0 to 1.5 × 105 CFU/g in 1995 and from 0 to 1.5 × 107 CFU/g in 1996. Seed contamination levels were positively correlated with X. campestris pv. carotae populations detected on leaves and with the incidence and severity of carrot bacterial blight. The size of X. campestris pv. carotae populations on leaves was also directly related to disease incidence. In 1996, yields were significantly reduced in plots established with seed lots having the highest levels of X. campestris pv. carotae contamination. Under the conditions of this study (i.e., a location having low rainfall and relative humidity), the threshold of seed contamination for the establishment of X. campestris pv. carotae populations on leaves and for the development of carrot bacterial blight was unexpectedly high: 104 to 105 CFU/g of seed.

Influence of Temperature and Host Plant on the Interaction Between Pratylenchus neglectus and Meloidogyne chitwoodi.

The interaction between Pratylenchus neglectus (Pn) and Meloidogyne chitwoodi (Mc) was investigated at soil temperatures of 15, 20, and 25 C on barley and potato. Maximum numbers of Pn and Mc penetrated barley roots at 20 C, whereas a minimum number penetrated at 15 C. Pratylenchus neglectus restricted root penetration by Mc over time and vice-versa. Population densities of each species increased with increasing temperature. Concomitant inoculation of the two species resulted in lower numbers of Pn at 15 and 25 C in both barley and potato, whereas the numbers of Mc were lower at 15 C in barley and at 25 C in potato. Root weights of potato and barley at 15 and 20 C, respectively, were lowered by the presence of both nematodes singly or concomitantly. At 25 C, barley plants inoculated with Mc alone had lower shoot weight than uninoculated controls, but the damage was restricted when Pn also was present. The two species interact competitively, and the outcome varies with soil temperature and host plant. Pn has the potential to suppress Mc population levels and reduce the damage it causes to potato and barley.

Competition between the Plant-parasitic Nematodes Pratylenchus neglectus and Meloidogyne chitwoodi.

In experiments on competition between Pratylenchus neglectus and Meloidogyne chitwoodi in barley, the species that parasitized the roots first inhibited penetration by the latter species. Prior presence of P. neglectus impeded the development of M. chitwoodi. Pratylenchus neglectus reduced egg production, final population levels, and reproductive index of M. chitwoodi. The reduction was linearly related to initial population densities of P. neglectus. Initial population densities of M. chitwoodi had no effect on final population levels of P. neglectus. Carbon assimilation by barley plants was reduced when either nematode species was present alone, but not when both were present together. Both nematode species assimilated lower amounts of carbon when present together than when present alone. A split-root experiment demonstrated that translocatable chemicals were not involved in the competition between the two species.

Effects of Temperature on Pratylenchus neglectus and on Its Pathogenicity to Barley.

In a petri-dish study, development of the nematode Pratylenchus neglectus was observed every 4 days, and stage-specific development times were estimated, using a parameter estimation algorithm for a distributed-delay population model. The lower threshold temperature for development of a population of P. neglectus was 7.75 C. Temperatures above 25 C were unfavorable for this population on barley. Total numbers of P. neglectus in barley roots and associated soil in pots were greatest at 25 C and lower at temperatures above and below that level. There was no change in nematode numbers per gram of root as temperature increased between 24 C and 32 C because root weights decreased at higher temperatures. Restricted root mass may contribute to the lower total nematode population levels at higher temperature. Maximum number of nematodes moved through a 2-cm layer of sand on a Baermann funnel at about 20 C; lowest number of nematodes moved at 10 C and 30 C.