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ABSTRACTThree hundred sixty-one quinupristin-dalfopristin (Q-D)-resistant Enterococcus faecium(QDREF) isolates were isolated from humans, turkeys, chickens, swine, dairy and beef cattle from farms, chicken carcasses, and ground pork from grocery stores in the United States from 1995 to 2003. These isolates were evaluated by pulsed-field gel electrophoresis (PFGE) to determine possible commonality between QDREF isolates from human and animal sources. PCR was performed to detect the streptogramin resistance genes vatD, vatE, and vgbAand the macrolide resistance gene ermBto determine the genetic mechanism of resistance in these isolates. QDREF from humans did not have PFGE patterns similar to those from animal sources. vatEwas found in 35%, 26%, and 2% of QDREF isolates from turkeys, chickens, and humans, respectively, and was not found in QDREF isolates from other sources. ermBwas commonly found in QDREF isolates from all sources. Known streptogramin resistance genes were absent in the majority of isolates, suggesting the presence of other, as-yet-undetermined, mechanisms of Q-D resistance.

ABSTRACTWe evaluated the molecular mechanism for resistance of 360 enterococci for which the gentamicin MICs were =128 µg/ml. The aac(6')-Ie-aph(2")-Ia, aph(2")-Ic, and aph(2")-Idgenes were identified by PCR in isolates from animals, food, and humans. The aph(2")-Ibgene was not identified in any of the isolates. Two Enterococcus faecalisisolates (MICs > 1,024 µg/ml) from animals failed to generate a PCR product for any of the genes tested and likely contain a new unidentified aminoglycoside resistance gene. Pulsed-field gel electrophoresis (PFGE) analysis showed a diversity of strains. However, 1 human and 18 pork E. faecalisisolates from Michigan with the aac(6')-Ie-aph(2")-Iagene had related PFGE patterns and 2 E. faecalisisolates from Oregon (1 human and 1 grocery store chicken isolate) had indistinguishable PFGE patterns. We found that when a gentamicin-resistant gene was present in resistant enterococci from animals, that gene was also present in enterococci isolated from food products of the same animal species. Although these data indicate much diversity among gentamicin-resistant enterococci, the data also suggest similarities in gentamicin resistance among enterococci isolated from humans, retail food, and farm animals from geographically diverse areas and provide evidence of the spread of gentamicin-resistant enterococci from animals to humans through the food supply.

ABSTRACTSequencing of DNA from 15 expanded-spectrum cephalosporin (e.g., ceftriaxone)-resistant Salmonellaisolates obtained in the United States revealed that resistance to ceftriaxone in all isolates was mediated by cmy-2.Hybridization patterns revealed three plasmid structures containing cmy-2in these 15 isolates. These data suggest that the spread of cmy-2among Salmonellastrains is occurring through mobilization of the cmy-2gene into different plasmid backbones and consequent horizontal transfer by conjugation.

Laboratory-based surveillance of salmonella isolates serotyped at four state health departments (Illinois, Michigan, Minnesota and Wisconsin) led to the identification of multistate outbreaks of salmonella infections during 1990 (176 cases of S. javiana) and 1993 (100 cases of S. montevideo). Community-based case-control studies and product traceback implicated consumption of tomatoes from a single South Carolina tomato packer (Packer A) MOR 16·0; 95% CI 2·1, 120·6; P<0·0001 in 1990 and again in 1993 (MOR 5·7; 95% CI 1·5, 21·9; P=0·01) as the likely vehicle. Contamination likely occurred at the packing shed, where field grown tomatoes were dumped into a common water bath. These outbreaks represent part of a growing trend of large geographically dispersed outbreaks caused by sporadic or low-level contamination of widely distributed food items. Controlling contamination of agricultural commodities that are also ready-to-eat foods, particularly fruits and vegetables, presents a major challenge to industry, regulators and public health officials.

The authors present the first published case of angiofollicular lymph-node hyperplasia, observed in identical twins. In both cases the lesion had the same location, but there was a difference of two years in the time of presentation. A morphological description and discussion of pathogenesis are given.

In this work, an adaptive controller for bioreactors, using the measurement of output gas flow rate to handle the uncertainty on biomass concentration and kinetic rate is developed. A mass–balance model based on a unique reaction pathway to represent the input–output behavior is considered. Time-varying and unknown but bounded behavior of plant parameters, including the substrate concentration at the inflow and the yield coefficients is taken into account in the controller. The Lyapunov-like function method to develop the controller is used. A new method to handle the unknown time-varying behavior of the control gain is developed; with this method it is assured that the output tracks the desired reference with a user-defined tolerance and parameter drifting is avoided. The main contributions of the scheme with respect to closely related works are: (i) the exact values of the plant parameters are not required to be known; (ii) upper or lower bound related to the plant parameters is not required to be known; (iii) the time-varying behavior of plant parameters in the control design and in the convergence analysis is considered. [ABSTRACT FROM AUTHOR]