Publications

epidemiologic evaluation of diarrhea in dogs in an animal shelter.	to determine associations among infectious pathogens and diarrheal disease in dogs in an animal shelter and demonstrate the use of geographic information systems (giss) for tracking spatial distributions of diarrheal disease within shelters.	2005	16008226
longitudinal monitoring of two commercial layer flocks and their environments for salmonella enterica serovar enteritidis and other salmonellae.	between august 20, 2001, and september 17, 2002, 1429 samples including drag swabs, egg belt or egg rollout swabs, fan-blade swabs, rodent organ and intestinal pools, beetle (alphitobius diaperinus) pools, housefly (musca domestica) pools, chicken organ and intestinal pools, and egg pools were obtained for salmonella culture from two flocks from two different commercial layer ranches. the two ranches were purposefully selected for the study based on their previous status of salmonella enteritidi ...	2005	16094821
a multi-state outbreak of salmonella serotype thompson infection from commercially distributed bread contaminated by an ill food handler.	foodborne transmission is estimated to account for 95% of non-typhoidal salmonella infections reported in the united states; however, outbreaks of salmonellosis are rarely traced to food handlers. in august 2000, an increase in salmonella serotype thompson infection was noted in southern california; most of the cases reported eating at a restaurant chain (chain a) before illness onset. a case-control study implicated the consumption of burgers at chain a restaurants. the earliest onset of illnes ...	2005	16181501
salmonella and campylobacter spp. in northern elephant seals, california.	campylobacter and salmonella spp. prevalence and antimicrobial drug sensitivity were determined in northern elephant seals that had not entered the water and seals that were stranded on the california coast. stranded seals had a higher prevalence of pathogenic bacteria, possibly from terrestrial sources, which were more likely to be resistant.	2005	16485493
prevalence of campylobacter and salmonella species on farm, after transport, and at processing in specialty market poultry.	the prevalence of campylobacter and salmonella spp. was determined from live bird to prepackaged carcass for 3 flocks from each of 6 types of california niche-market poultry. commodities sampled included squab, quail, guinea fowl, duck, poussin (young chicken), and free-range broiler chickens. campylobacter on-farm prevalence was lowest for squab, followed by guinea fowl, duck, quail, and free-range chickens. poussin had the highest prevalence of campylobacter. no salmonella was isolated from gu ...	2006	16493957
thermophilic-anaerobic digestion to produce class a biosolids: initial full-scale studies at hyperion treatment plant.	the highest quality of biosolids is called exceptional quality. to qualify for this classification, biosolids must comply with three criteria: (1) metal concentrations, (2) vector-attraction reduction, and (3) the class a pathogen-density requirements. the city of los angeles bureau of sanitation hyperion treatment plant (htp) (playa del rey, california) meets the first two requirements. thus, the objective of this study was to ensure that htp's biosolids production would meet the class a pathog ...	2006	16566524
antimicrobial resistance and genetic relatedness among salmonella from retail foods of animal origin: narms retail meat surveillance.	salmonella isolates were recovered from a monthly sampling of chicken breasts, ground turkey, ground beef, and pork chops purchased from selected grocery stores in six participating foodnet sites (connecticut, georgia, maryland, minnesota, oregon, and tennessee) in 2002 and an additional two sites in 2003 (california and new york). in 2002 and 2003, a total of 6,046 retail meats were examined, including 1,513 chicken breasts, 1,499 ground turkey samples, 1,522 ground beef samples, and 1,502 pork ...	2006	16602986
salmonella spp., vibrio spp., clostridium perfringens, and plesiomonas shigelloides in marine and freshwater invertebrates from coastal california ecosystems.	the coastal ecosystems of california are highly utilized by humans and animals, but the ecology of fecal bacteria at the land-sea interface is not well understood. this study evaluated the distribution of potentially pathogenic bacteria in invertebrates from linked marine, estuarine, and freshwater ecosystems in central california. a variety of filter-feeding clams, mussels, worms, and crab tissues were selectively cultured for salmonella spp., campylobacter spp., escherichia coli-o157, clostrid ...	2006	16897302
prevalence and antimicrobial resistance patterns of salmonella enterica in preweaned calves from dairies and calf ranches.	to evaluate serovar and antimicrobial resistance patterns of salmonella enterica isolated from preweaned calves and identify management risk factors associated with fecal shedding of s enterica.	2006	16948605
genetic and phenotypic variability among salmonella enterica serovar typhimurium isolates from california dairy cattle and humans.	fifty-six human and 24 adult dairy cattle isolates of salmonella enterica serovar typhimurium from a single county in california were compared using ribotyping, insertion sequence typing (is200), pulsed-field gel electrophoresis, plasmid typing, phage typing, and antimicrobial resistance testing. the majority of the isolates fell into one of two groups which were phage types dt104 and dt193. combining the information from all typing methods, a total of 45 different "clusters" were defined, with ...	2006	17021214
comparison of salmonella enterica serovar distribution and antibiotic resistance patterns in wastewater at municipal water treatment plants in two california cities.	to determine salmonella enterica serovars and antibiotic resistance (abr) in the human waste stream.	2006	17105561
full-scale class a biosolids production by two-stage continuous-batch thermophilic anaerobic digestion at the hyperion treatment plant, los angeles, california.	the city of los angeles hyperion treatment plant (htp) (california) converted its anaerobic digesters to thermophilic operation to produce class a biosolids. phase iv tests demonstrated compliance of a two-stage, continuous-batch process with alternative 1 of u.s. environmental protection agency 40 cfr part 503 (u.s. epa, 1993), which defines the time-temperature requirement for batch treatment (t > or = 56.3 degrees c at 16-h holding). fecal coliforms, salmonella sp., viable helminth ova, and e ...	2006	17120443
recurrence of fecal coliforms and salmonella species in biosolids following thermophilic anaerobic digestion.	the u.s. environmental protection agency (u.s. epa) part 503 biosolids rule requires the fecal coliform (indicator) or salmonella species (pathogen) density requirements for class a biosolids to be met at the last point of plant control (truck-loading facility and/or farm for land application). the three southern californian wastewater treatment plants in this study produced biosolids by thermophilic anaerobic digestion and all met the class a limits for both fecal coliforms and salmonella sp. i ...	2006	17120460
prevalence of salmonella in diverse environmental farm samples.	the development of suitable intervention strategies to control salmonella populations at the farm level requires reliable data on the occurrence and prevalence of the pathogen. previous studies on salmonella prevalence have focused on acquiring data from specific farm types and/or selected regions. the purpose of this study was to evaluate the distribution of this pathogen across a variety of farm types and regions in order to generate comparative data from a diverse group of environmental sampl ...	2006	17133798
recovery of salmonella, listeria monocytogenes, and mycobacterium bovis from cheese entering the united states through a noncommercial land port of entry.	a joint multiagency project was initiated in response to a salmonella outbreak in san diego county, california, in 2004. samples of cheese were collected during four 1-day operations at the san ysidro port of entry, along the united states-mexico border. surveyed participants were persons crossing the border as pedestrians or in vehicles who had a minimum of 2.27 kg of cheese, which may suggest a potential diversion to illegal marketing. in addition, data were collected about the cheese to ident ...	2007	17265859
multiple antimicrobial resistance in plague: an emerging public health risk.	antimicrobial resistance in yersinia pestis is rare, yet constitutes a significant international public health and biodefense threat. in 1995, the first multidrug resistant (mdr) isolate of y. pestis (strain ip275) was identified, and was shown to contain a self-transmissible plasmid (pip1202) that conferred resistance to many of the antimicrobials recommended for plague treatment and prophylaxis. comparative analysis of the dna sequence of y. pestis plasmid pip1202 revealed a near identical inc ...	2007	17375195
prevalence and amounts of salmonella found on raw california almonds.	data on the prevalence and populations of pathogens in individual foods are critical to the development of product-specific quantitative microbial risk assessments. an outbreak of salmonellosis associated with the consumption of raw almonds in 2000 to 2001 provided an opportunity to evaluate the levels of salmonella in the recalled product. duplicate 100-g samples from each of fifty 22.7-kg boxes of recalled almonds were enriched by one of two methods. salmonella was isolated by at least one met ...	2007	17477248
the use of bulk tank milk samples to monitor trends in antimicrobial resistance on dairy farms.	the routine monitoring of bacteria obtained from bulk tank milk (btm) may be an important tool for detecting farm-level trends in antimicrobial resistance on dairy farms. this study describes and compares antimicrobial susceptibility patterns of salmonella enterica subspecies enterica (salmonella) and escherichia coli recovered from dairy btm. btm from more than 400 dairies in a dairy-intense region of california were sampled eight times at 2- to 3-month intervals over a 29-month period. from sa ...	2007	18041950
evaluation of commercial antisera for salmonella serotyping.	we compared a set of commercial salmonella somatic and flagellar serotyping antisera to in-house-prepared antisera from the microbial diseases laboratory, california department of public health, using 327 salmonella enterica strains belonging to subgroups i, ii, iiia, iiib, and iv. the sensitivities of denka seiken (tokyo, japan) somatic and flagellar antisera (using a tube agglutination assay) were 94.0% and 99.2%, respectively, and the specificity was 100% for both sets of sera. polyvalent o a ...	2008	18094130
washing practices on the microflora on georgia-grown cantaloupes.	in recent years, several foodborne illness outbreaks have been associated with the consumption of cantaloupe. cantaloupes can be contaminated with pathogens anywhere from the field to the packing line. in the united states, cantaloupes are handled and packed differently in each state. georgia-grown cantaloupes are brought to sheds, washed, and packed, whereas california-grown cantaloupes are field packed. in this study, the microbiological status of cantaloupes produced by four georgia growers t ...	2008	18236661
salmonella infections associated with mung bean sprouts: epidemiological and environmental investigations.	we investigated an outbreak of salmonella enteritidis (se) infections linked to raw mung bean sprouts in 2000 with two case-control studies and reviewed six similar outbreaks that occurred in 2000-2002. all outbreaks were due to unusual phage types (pt) of se and occurred in the united states (pt 33, 1, and 913), canada (pt 11b and 913), and the netherlands (pt 4b). pt 33 was in the spent irrigation water and a drain from one sprout grower. none of the growers disinfected seeds at recommended co ...	2009	18294429
fecal indicator bacteria and salmonella in ponds managed as bird habitat, san francisco bay, california, usa.	throughout the world, coastal resource managers are encouraging the restoration of previously modified coastal habitats back into wetlands and managed ponds for their ecosystem value. because many coastal wetlands are adjacent to urban centers and waters used for human recreation, it is important to understand how wildlife can affect water quality. we measured fecal indicator bacteria (fib) concentrations, presence/absence of salmonella, bird abundance, and physico-chemical parameters in two coa ...	2008	18457857
antimicrobial resistance in salmonella enterica subspecies enterica serovar dublin from dairy source calves in the central san joaquin valley, california (1998-2002).	the present study describes antimicrobial resistance patterns of salmonella enterica subspecies enterica serovar dublin (s. dublin) in clinical submissions from calves and temporal and farm-type trends in antimicrobial resistance patterns of the isolates. a total of 300 isolates of s. dublin were obtained from fecal or internal organs of calves fewer than 120 days of age originating from 84 dairies and 18 calf ranches from july 1998 to december 2002. the isolates were susceptibility tested to a ...	2008	18599857
risk factors for infection with pathogenic and antimicrobial-resistant fecal bacteria in northern elephant seals in california.	the goal of this study was to identify potential environmental and demographic factors associated with campylobacter jejuni (c. jejuni), salmonella enterica (salmonella spp.), and antimicrobial-resistant escherichia coli (e. coli) infection in northern elephant seals stranded along the california coastline.	2008	19006978
enteric bacterial pathogen detection in southern sea otters (enhydra lutris nereis) is associated with coastal urbanization and freshwater runoff.	although protected for nearly a century, california's sea otters have been slow to recover, in part due to exposure to fecally-associated protozoal pathogens like toxoplasma gondii and sarcocystis neurona. however, potential impacts from exposure to fecal bacteria have not been systematically explored. using selective media, we examined feces from live and dead sea otters from california for specific enteric bacterial pathogens (campylobacter, salmonella, clostridium perfringens, c. difficile an ...	2010	19720009
multistate outbreak of human salmonella typhimurium infections associated with aquatic frogs - united states, 2009.	during april-july 2009, the utah department of health identified five cases of salmonella typhimurium infection with indistinguishable pulsed-field gel electrophoresis (pfge) patterns, predominantly among children. in august, cdc began a multistate outbreak investigation to determine the source of the infections. this report summarizes the results of this ongoing investigation, which, as of december 30, had identified 85 s. typhimurium human isolates with the outbreak strain from 31 states. in a ...	2010	20057349
presence of bacteroidales as a predictor of pathogens in surface waters of the central california coast.	the value of bacteroidales genetic markers and fecal indicator bacteria (fib) to predict the occurrence of waterborne pathogens was evaluated in ambient waters along the central california coast. bacteroidales host-specific quantitative pcr (qpcr) was used to quantify fecal bacteria in water and provide insights into contributing host fecal sources. over 140 surface water samples from 10 major rivers and estuaries within the monterey bay region were tested over 14 months with four bacteroidales- ...	2010	20639358
use of a self-assessment questionnaire for food safety education in the home kitchen --- los angeles county, california, 2006-2008.	foodborne diseases remain an important cause of morbidity in the united states among all age groups. a potentially important contributor to this morbidity is improper food handling and preparation practices in kitchens at restaurants and in private homes. in 1998, the los angeles county department of public health (lacdph) established numeric scores for restaurant inspections and posted grades for these inspections publicly; by the end of 1998 this initiative was credited with helping to reduce ...	2010	20814405
impact of urbanization and agriculture on the occurrence of bacterial pathogens and stx genes in coastal waterbodies of central california.	fecal pollution enters coastal waters through multiple routes, many of which originate from land-based activities. runoff from pervious and impervious land surfaces transports pollutants from land to sea and can cause impairment of coastal ocean waters. to understand how land use practices and water characteristics influence concentrations of fecal indicator bacteria (fib) and pathogens in natural waters, fourteen coastal streams, rivers, and tidal lagoons, surrounded by variable land use and an ...	2010	21168181
analysis of tomato and jalapeño and serrano pepper imports into the united states from mexico before and during a national outbreak of salmonella serotype saintpaul infections in 2008.	case-control studies conducted during a multistate outbreak of salmonella enterica serotype saintpaul infections in 2008 revealed associations between illness and the consumption of jalapeño peppers, serrano peppers, and tomatoes. traceback investigations of implicated jalapeño and serrano peppers led to farms in tamaulipas and nuevo león, mexico. we conducted a novel analysis of a u.s. food and drug administration database of tomatoes and jalapeño and serrano peppers imported from mexico during ...	2010	21219707
prevalence, distribution, and diversity of salmonella enterica in a major produce region of california.	a survey was initiated to determine the prevalence of salmonella enterica in the environment in and around monterey county, ca, a major agriculture region of the united states. trypticase soy broth enrichment cultures of samples of soil/sediment (n = 617), water (n = 252), wildlife (n = 476), cattle feces (n = 795), and preharvest lettuce and spinach (n = 261) tested originally for the presence of pathogenic escherichia coli were kept in frozen storage and later used to test for the presence of ...	2011	21378057
zoonotic pathogens isolated from wild animals and environmental samples at two california wildlife hospitals.	to determine types and estimate prevalence of potentially zoonotic enteric pathogens shed by wild animals admitted to either of 2 wildlife hospitals and to characterize distribution of these pathogens and of aerobic bacteria in a hospital environment.	2011	21401435
effect of irradiation on salmonella survival and quality of 2 varieties of whole green onions.	two varieties of green onions, banner and baja verde, were inoculated with a cocktail of 3 salmonella strains using dip and spot inoculation and irradiated at 0, 0.3, 0.6, 0.9, and 1.2 kgy using electron beam. salmonella survivors were enumerated using a xld underlay/tsaye overlay plating method. the d values were in the range of 0.26 to 0.32 kgy depending on variety but not on the method of inoculation. this indicated that a 5-log reduction of salmonella can be achieved at a dose of 1.6 kgy. fo ...	2011	21623790
to the happy few.	i became a microbiologist in post-wwii japan, working with toshio fukasawa on galactose metabolism in salmonella. we characterized mutants defective in udp-galactose 4-epimerase, which produced a defective lipopolysaccharide, and this opened doors for me to study lipopolysaccharide biosynthesis, which i pursued in the united states, in the laboratory of herman kalckar. after i moved to berkeley, california, in 1969, i became interested in the function of bacterial outer membranes, a line of work ...	2011	21639787
sources and fate of salmonella and fecal indicator bacteria in an urban creek.	this research aimed to understand the sources and fate of salmonella and fecal bacteria in urban surface waters. an urban creek (san pedro creek, california, usa) that had unusually high levels of salmonella and fecal bacteria relative to other nearby waterbodies was chosen as a model field site. state of the art microbiological methods were used in concert with modeling to investigate salmonella and fecal bacteria sources, and determine field-relevant dark inactivation and photoinactivation rat ...	2011	21687857
multistate outbreak of multidrug-resistant salmonella newport infections associated with ground beef, october to december 2007.	in late october 2007, an outbreak of multidrug-resistant salmonella newport infections affected 42 case patients in california, arizona, idaho, and nevada. a case-control study implicated ground beef from one chain store. despite detailed ground beef purchase histories-including shopper card information for several case patients-traceback efforts by both the u.s. department of agriculture, food safety and inspection service and the california department of public health were unable to identify t ...	2011	21819658
prevalence of selected bacterial and parasitic agents in feces from diarrheic and healthy control cats from northern california.	background: bacterial and parasitic agents are commonly implicated as causes of diarrhea in cats, but there is a paucity of information evaluating epidemiological and prevalence factors associated with most of these organisms in cats. objectives: determine the prevalence of selected enteropathogens in diarrheic and nondiarrheic cats. animals: a total of 219 diarrheic and 54 nondiarrheic cats. methods: prospective study. fresh fecal specimens were submitted for centrifugation flotation, culture, ...	2011	22182203