No abstract

Methods. In this case-control study, hepatitis A cases among Hispanic children who were younger than 18 years reported from June 1998 through August 2000 were matched by age group and exposure period to Hispanic children who were susceptible to HAV infection. Participants and their families were interviewed about demographic information and potential sources of HAV infection, including attending child care, food and waterborne exposures, cross-border and other international travel, and travel-related activities.Results. Participants included 132 children with hepatitis A and 354 control subjects. The median age of study participants was 7 years (range: 1-17 D espite declining rates in the United States, hepatitis A is one of the most frequently reported vaccine-preventable diseases, surpassing rubella, pertussis, and measles. In 1997, Ͼ30 000 people, including 11 000 children younger than 18 years, were reported with acute hepatitis A. 1 After these data were adjusted for anicteric infection and underreporting, an estimated 246 000 children were infected with hepatitis A virus (HAV) in 1997 2 (unpublished data, Centers for Disease Control and Prevention [CDC]). Hispanic children have among the highest rates of hepatitis A. In 1997, the rate among Hispanic children was 46.7 cases per 100 000, Ͼ10 times the rate among non-Hispanic white and black children. 1 In the United States, the Hispanic population is now the largest minority group, representing 13.3% of the population. 3 The 2000-mile United StatesMexico border is one of the world's busiest international boundaries, with an estimated 320 million legal northbound border crossings annually. 4 The US and Mexico border areas have a combined population of Ͼ11 million people, many of whom cross the border frequently in both directions to visit family and friends, shop, work, attend school, or seek medical care. 5 From 1990 to 1997, the incidence rate of hepatitis A in US border counties was Ͼ3 times higher than in nonborder US states. 6 In 1997, Hispanics represented 25% of the San Diego County population; however, they accounted for 37% of the reported cases of hepatitis A. From 1990 through 1997, an average of 105 cases of hepatitis A occurred annually among Hispanic children younger than 18 years in San Diego County. The rate of hepatitis A among Hispanic children ranged from 37 to 62 cases per 100 000 (average annual rate: 48 cases per 100 000), Ͼ3 times the national average for children (14 cases per 100 000) and 4 times the rate of Hispanic adults and non-Hispanic white and black children who live in San Diego (unpublished data, CDC).In seroprevalence surveys conducted in rural border areas and colonias, unincorporated border communities, hepatitis A has been associated with limited sanitary infrastructure and crowded living e68PEDIATRICS Vol. conditions. 7-9 In contrast, San Diego County is primarily an urban border area with basic sanitary infrastructure available to most residents; risk factors for hepatitis A in communities such as San Diego have not be...

No abstract

Antimicrobial resistance levels were examined for 365 Salmonella isolates recovered from the lymph nodes (n = 224) and cecal contents (n = 141) of market-age swine at slaughter. Antimicrobial resistance testing was performed by disk diffusion using 13 antibiotics common in the treatment of disease in human and veterinary medicine. Although none of the antibiotics tested were used subtherapeutically within the last 5 years on the farms sampled, resistance to chlortetracycline, penicillin G, streptomycin, and sulfisoxazole was common. Penicillin G resistance was significantly more frequent (P = 0.03) and sulfisoxazole resistance was significantly less frequent (P < 0.01) in lymph node versus cecal isolates. Multidrug resistance was observed among 94.7% of the lymph node isolates and 93.5% of the cecal isolates. The most frequent multidrug resistance pattern included three antibiotics-penicillin G, streptomycin, and chlortetracycline. Isolates in somatic serogroup B, and more specifically, Salmonella Agona and Salmonella Schwarzengrund isolates, were often resistant to a greater number of antibiotics than were isolates in the other serogroups. Streptomycin, sulfisoxazole, ampicillin (lymph node isolates), and nitrofurantoin (cecal isolates) resistance levels differed significantly between somatic serogroups. The prevalence of penicillin G-, streptomycin-, and sulfisoxazole-resistant isolates differed significantly between serovars for both lymph node and cecal isolates. Results of this study suggest that a correlation exists between the somatic serogroup or serovar of a Salmonella isolate and its antimicrobial resistance status, which is specific to the antibiotic of interest and the source of the isolate (lymph node versus cecal contents).

The antibiotics apramycin and carbadox were fed to growing swine, and the prevalence of Salmonella isolates that are resistant to apramycin and related aminoglycoside antibiotics was examined. Three hundred twelve Salmonella-positive pigs raised on one of five farms in an integrated swine operation and slaughtered at a central plant were used. All farms fed carbadox during the grower phase, and two farms administered apramycin during the first 21 days of age. Ileocolic lymph nodes and cecal contents were sampled at slaughter. One hundred of the 312 pigs were randomly selected to examine apramycin- and carbadox-resistant Salmonella infection, while all 312 pigs were used to evaluate the association between apramycin exposure and infection with Salmonella organisms resistant to amikacin, gentamicin, kanamycin, and streptomycin. Antimicrobial resistance was determined using disk diffusion and breakpoint concentrations. Apramycin treatment appeared to have little effect on apramycin- (12.5 versus 20.9%) or streptomycin- (76.4 versus 73.5%) resistant Salmonella isolates when averaged across farms and compared to control animals. Feeding carbadox resulted in carbadox-resistant Salmonella infection in only 5.3% of the isolates on one farm. The prevalence of amikacin-, gentamicin-, and kanamycin-resistant Salmonella isolates on farms feeding apramycin and carbadox were 0, 0, and 1.8%, respectively. Serogroup B was the most prevalent serogroup isolated, followed by C1 and E1. Apramycin and carbadox treatment did not appear to have any effect on the serogroup isolated. Subtherapeutic use of carbadox and apramycin did not appear to increase the prevalence of antimicrobial-resistant Salmonella in market-age swine.

The objective of the present study was to evaluate how feed withdrawal and transportation influenced the cecal environment and cecal populations of Campylobacter in swine. Four miniature Yucatan gilts (8.8 kg), naturally infected with Campylobacter jejuni, were surgically implanted with cecal cannulas. The gilts were fasted for 48 h. Samples of cecal contents were collected for 7 days prior to and for 7 days after the fast, and mean values were determined for pH, volatile fatty acids (VFA), and CFU enumeration of C. jejuni. This was replicated three times. In another trial, gilts (full-fed) were transported in a livestock trailer for 4 h and cecal samples were collected before and after transport and analyzed for pH, VFA, and CFU. Following a 48-h fast, cecal pH increased (P < 0.05) by 1 unit; acetic and propionic acids decreased (P < 0.05) by 61% and 71%, respectively; and there was a twofold log10 increase (P < 0.05) in CFU/g cecal content of C. jejuni. Values of pH, VFA, and CFU of C. jejuni did not change in cecal samples from gilts following transportation. These data are important for food safety considerations because feed withdrawal, commonly associated with shipping and slaughter, can increase Campylobacter concentrations in the pig intestinal tract.

No abstract

An epidemiologic survey was conducted to determine the prevalence of salmonellae in swine from 5 farms of an integrated swine operation. The purpose of this study was to evaluate the recovery efficiencies for salmonellae from swine lymph nodes and cecal contents when GN Hajna and tetrathionate were compared as initial enrichments. Salmonellae were isolated from 61% of 645 pigs at slaughter; 324 positive cultures were from lymph nodes, and 224 were from cecal contents. Frequently, pigs had salmonellae isolated from both the lymph nodes and cecal contents. Total isolations, regardless of source, were similar for GN Hajna (247) and tetrathionate (301). There was no difference ( P > 0.05) in the number of isolations from lymph nodes when GN Hajna enrichment was compared with tetrathionate enrichment (174 vs. 150). However, there was a significant ( P > 0.05) advantage of utilizing tetrathionate when compared with GN Hajna for isolations from cecal contents (151 vs. 73).