CDC is collaborating with the Pennsylvania State Health Department in an ongoing investigation of an outbreak of human Salmonella enterica serotype Paratyphi B var. L (+) tartrate + infections associated with pet turtle exposures. Turtles have long been recognized as sources of human Salmonella infections and are a particular risk to young children. Although the sale or distribution of small turtles (those with carapace lengths <4 inches [<10.2 cm]) has been prohibited in the United States since 1975 (with exceptions for scientific or educational purposes), they are still available for illegal purchase through transient vendors on the street, at flea markets, and at fairs.

BACKGROUND: The emergence of resistance to antimicrobial agents within the salmonellae is a worldwide problem that has been associated with the use of antibiotics in livestock. Resistance to ceftriaxone and the fluoroquinolones, which are used to treat invasive salmonella infections, is rare in the United States. We analyzed the molecular characteristics of a ceftriaxone-resistant strain of Salmonella enterica serotype typhimurium isolated from a 12-year-old boy with fever, abdominal pain, and diarrhea. METHODS: We used pulsed-field gel electrophoresis and analysis of plasmids and beta-lactamases to compare the ceftriaxone-resistant S. enterica serotype typhimurium from the child with four isolates of this strain obtained from cattle during a local outbreak of salmonellosis. RESULTS: The ceftriaxone-resistant isolate from the child was indistinguishable from one of the isolates from cattle, which was also resistant to ceftriaxone. Both ceftriaxone-resistant isolates were resistant to 13 antimicrobial agents; all but one of the resistance determinants were on a conjugative plasmid of 160 kb that encoded the functional group 1 beta-lactamase CMY-2. Both ceftriaxone-resistant isolates were closely related to the three other salmonella isolates obtained from cattle, all of which were susceptible to ceftriaxone. CONCLUSIONS: This study provides additional evidence that antibiotic-resistant strains of salmonella in the United States evolve primarily in livestock. Resistance to ceftriaxone, the drug of choice for invasive salmonella disease, is a public health concern, especially with respect to children, since fluoroquinolones, which can also be used to treat this disease, are not approved for use in children.

BACKGROUND: Salmonella enterica serotype choleraesuis is a cause of serious systemic infections. Because fluoroquinolones are the drug of choice for the treatment of severe salmonella infections, the emergence and dissemination of fluoroquinolone-resistant S. enterica serotype choleraesuis have clinical consequences. METHODS: In Taiwan, a hospital-based surveillance system has been in place since 1987 to monitor the incidence of S. enterica serotype choleraesuis infections and the antimicrobial susceptibility of the isolates. We investigated the rapid emergence of fluoroquinolone resistance in this serotype in 2000 and 2001. Pigs in Taiwan were evaluated as a potential source of the resistant salmonella. RESULTS:A total of 501 clinical isolates of S. enterica serotype choleraesuis were recovered in our hospital from 1987 through 2000. The proportion of total salmonella isolates made up by S. enterica serotype choleraesuis decreased from an average of 8.4 percent before 1995 to 2.7 percent in 1996 through 1998. During 1999 and 2000, this proportion increased significantly, to an average of 5.0 percent. Ciprofloxacin resistance in S. enterica serotype choleraesuis has been observed since 2000. In the third quarter of 2001, 60 percent of isolates were resistant to ciprofloxacin. Molecular typing indicated that the primary source of S. enterica serotype choleraesuis isolates was herds of swine. All the resistant isolates from humans and swine had mutations that led to the substitution of phenylalanine for serine at position 83 and asparagine for aspartic acid at position 87 in the gene for DNA gyrase A. CONCLUSIONS: This investigation in Taiwan indicates that fluoroquinolone-resistant S. enterica serotype choleraesuis can spread from swine to humans. The use of fluoroquinolones in food animals should be prohibited.

During the period from 1994 to 1996, an increase in the number of laboratory-confirmed cases of human salmonellosis associated with exposure to exotic pets including iguanas, pet turtles, sugar gliders, and hedgehogs was observed in Canada. Pet turtle-associated salmonellosis was recognized as a serious public health problem in the 1960s and 1970s, and in February 1975 legislation banning the importation of turtles into Canada was enacted by Agriculture Canada. Reptile-associated salmonellosis is once again being recognized as a resurgent disease. From 1993 to 1995, there were more than 20,000 laboratory-confirmed human cases of salmonellosis in Canada. The major source of Salmonella infection is food; however, an estimated 3 to 5% of all cases of salmonellosis in humans are associated with exposure to exotic pets. Among the isolates from these patients with salmonellosis, a variety of Salmonella serotypes were also associated with exotic pets and included the following: S. java, S. stanley, S. poona, S. jangwani, S. tilene, S. litchfield, S. manhattan, S. pomona, S. miami, S. rubislaw, S. marina subsp. IV, and S. wassenaar subsp. IV.

Chickens in groups of 40 were infected orally with a nalidixic acid-resistant mutant of Salmonella typhimurium and then fed continuously on diets containing ampicillin, chloramphenicol, furazolidone, neomycin, oxytetracycline, polymixin, spectinomycin, streptomycin or a mixture of trimethoprim and sulphadiazine. The amount of S. typhimurium excreted in their faeces was estimated at intervals by culture on brilliant green agar containing sodium nalidixate, both direct and after enrichment in selenite broth; the amount of Escherichia coli excreted was estimated by culture on MacConkey agar. The feeding of diets containing 500 mg./kg. of ampicillin, furazolidone, neomycin, polymixin, spectinomycin or streptomycin or 100 mg./kg. of trimethoprim and 500 mg./kg. of sulphadiazine for 46 days reduced to a varying degree the amount of S. typhimurium and E. coli excreted, the greatest reduction in S. typhimurium being brought about by the last treatment. The effect was less obvious when the concentration of the antibiotics in the food was decreased fivefold. An important reason for the very limited effect of some of the antibiotics was the emergence of antibiotic-resistant populations of S. typhimurium and E. coli. High concentrations of antibiotic-resistant organisms also arose in the faeces of the chickens fed diets containing tetracyclines and chloramphenicol, treatments which had no apparent effect on the amount of S. typhimurium and E. coli excreted. Much of the antibiotic resistance encountered was determined by R factors, a particular R factor usually being found in the E. coli populations of individual chickens before it was found in their S. typhimurium populations. No S. typhimurium or E. coli were isolated that possessed R factors determining resistance to polymixin, furazolidone or trimethoprim. No S. typhimurium or E. coli were isolated that were polymixin-resistant and no S. typhimurium that were furazolidone-resistant. The few trimethoprim-resistant S. typhimurium isolated were thymine-dependent. The feeding of diets containing the higher concentrations of trimethoprim/sulphadiazine, neomycin, furazolidone or ampicillin for 9 days reduced the amount of S. typhimurium excreted. After the withdrawal of these diets, the amount of S. typhimurium excreted increased to the numbers found in chickens given ordinary diets throughout; the chickens that had been given trimethoprim/sulphadiazine or furazolidone did not remain faecal excreters of S. typhimurium longer than the chickens that had been given ordinary diets. Similar results were obtained with trimethoprim/sulphadiazine when the start of the 9-day treatment period was delayed for an extra 9 days or when it was extended to 18 days.

Salmonella typhimurium phage type (PT) or definitive type (DT) 104 is a virulent pathogen for humans and animals, particularly cattle. It has been isolated increasingly from humans and animals in the United Kingdom and several other European countries and, more recently, in the United States and Canada. Humans may acquire the infection from foods of animal origin contaminated with the infective organism. Farm families are particularly at risk of acquiring the infection by contact with infected animals or by drinking unpasteurized milk. The symptoms in cattle are watery to bloody diarrhea, a drop in milk production, pyrexia, anorexia, dehydration and depression. Infection may result in septicemic salmonellosis and, upon necropsy, a fibrinonecrotic enterocolitis may be observed. The infection occurs more commonly in the calving season than at other times. Feedlot cattle and pigs may also be affected. Prolonged carriage and shedding of the pathogen may occur. Symptoms in humans consist of diarrhea, fever, headache, nausea, abdominal pain, vomiting, and, less frequently, blood in the stool. Salmonella typhimurium DT104 strains are commonly resistant to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline.

A number of animal-associated infections occur in persons infected with the human immunodeficiency virus (HIV), including those due to Toxoplasma gondii, Cryptosporidium, Microsporida, Salmonella, Campylo-bacter, Giardia, Rhodococcus equi, Rochalimaea, and Listeria monocytogenes. Most of these infections, with the exception of those due to Rochalimaea, appear to be acquired by the immunosuppressed individual from sources other than exposure to animals. Drs. Glaser and colleagues review our current understanding of the role of exposure to animals, especially pets, in the natural history of these opportunistic infections. They suggest that the risk of zoonotic transmission is small and offer practical suggestions designed to reduce this low risk. They conclude that the benefits of animal companionship outweigh the risks to patients and that prohibition of pet ownership by individuals infected with HIV is not warranted.

The importance and origin of antimicrobial-resistant Salmonella infections were examined in 52 outbreaks investigated by the Centers for Disease Control between 1971 and 1983. The case fatality rate was higher for patients infected with antimicrobial-resistant Salmonella (4.2 percent) than for those with antimicrobial-sensitive infections (0.2 percent). In the 38 outbreaks with identified sources, food animals were the source of 11 (69 percent) of 16 resistant and 6 (46 percent) of 13 sensitive outbreak strains.

A strain of Salmonella typhimurium appeared sequentially in three patients in a burn unit, and epidemiological study suggested the occurrence of person-to-person spread. This organism was responsible for both colonisation and invasive infection in these patients whose burn surfaces were receiving topical treatment with 0.5% silver nitrate (AgNO3) solution. The antibiotic and metal ionsusceptibility pattern of this strain of S. typhimurium was unique and disturbing: resistant to silver nitrate, mercuric chloride, ampicillin, chloramphenicol, tetracycline, streptomycin, and sulphonamides. This pattern of multiple resistances could be transferred by invitro mating experiments to sensitive recipient strains of Escherichia coli and S. typhimurium. Further transfer of these resistances could be consumated between different strains of E. coli. A survey of other salmonella strains isolated from patients in this hospital without thermal burns did not reveal this pattern of resistance. Also, strains of S. typhimurium, isolated elsewhere and showing simultaneous resistance to both ampicillin and chloramphenicol, were not resistant to AgNO3 in vitro. The very real danger of this strain of S. typhimurium in burn units stems from its resistance to the two most effective antibiotics (ampicillin and chloramphenicol) available for systemic therapy; and this threat may be compounded through the selection effected by the widespread topical use of AgNO3 solutions and sulphonamide preparations on burned surfaces.

A genotypically non-fimbriate (Fim-) strain of Salmonella typhimurium and a genotypically fimbriate (Fim+) strain derived from it by spontaneous mutation were compared for pathogenicity in mice. The two strains caused similar numbers of infections and deaths in groups of mice challenged by intraperitoneal inoculation, and nearly similar numbers in groups challenged by inoculation on to the conjunctiva, but the Fim+ strain caused many more infections (plus 26%) and deaths (plus 40%) than the Fim- strain when the inoculation was by mouth. Faecal cultures were made at intervals up to 120 days in the mice surviving after oral or conjunctival challenge and S. typhimurium was isolated more commonly from the animals challenged with the Fim+ strain (906 isolations from 384 animals infected out of 877 challenged) than from those challenged with the Fim- strain (614 isolations from 341 animals infected out of 877 challenged). The greater opportunity for faecal dissemination enjoyed by Fim+ bacteria may account for the preponderance of Fim+ over Fim- strains of S. typhimurium found in mammalian sources.