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Category: Microbial Genetics and Molecular Biology
Distinguishing between Epidemic and Endemic Occurrences of Infectious Diseases, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555817688/9781555812683_Chap05-1.gif /docserver/preview/fulltext/10.1128/9781555817688/9781555812683_Chap05-2.gifAbstract:
This chapter emphasizes the idea that outbreaks provide opportunities to evaluate the utility of new strain-typing systems applied to an infectious disease epidemiologic investigation. It shows that much of what we have come to know about transmission dynamics of infectious diseases was derived from attempts to better define relationships among seemingly unrelated individual, sporadic cases of the disease in community or institutional settings. Specific examples of the application of molecular strain-typing methods to differentiate between epidemic and endemic occurrences of infectious disease are discussed to illustrate these concepts. Through such applications, several new paradigms that determine infectious disease distribution and transmission have emerged. This chapter shows that efforts made to distinguish epidemic from endemic will identify features of an infectious disease process that are more complex, though often not recognized or considered. This idea is illustrated in the description of two common infectious disease epidemiologic problems: antimicrobial resistance and infectious disease transmission in community settings. The chapter provides examples of studies of the spatial distribution of drug-resistant infections. It also focuses on bacterial pathogens as examples to illustrate the epidemiologic concepts. These concepts should be applicable to other groups of infectious agents, including viral, fungal, and parasitic organisms for which discriminating strain-typing methods have been developed.
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(A) Proportion of Salmonella serotype Typhimurium isolates resistant to ampicillin from selected counties in the United States, 1979 to 1990. There appears to be a gradual increase in the prevalence of ampicillin resistance in this serotype of Salmonella over time. (B) This observation is compared with that of serial studies from New York State, where serotype Typhimurium ampicillin resistance appears to show no temporal trend in prevalence. Possible explanations for these two observations based on plasmid profile analysis are discussed in the text.
(A) Proportion of Salmonella serotype Typhimurium isolates resistant to ampicillin from selected counties in the United States, 1979 to 1990. There appears to be a gradual increase in the prevalence of ampicillin resistance in this serotype of Salmonella over time. (B) This observation is compared with that of serial studies from New York State, where serotype Typhimurium ampicillin resistance appears to show no temporal trend in prevalence. Possible explanations for these two observations based on plasmid profile analysis are discussed in the text.
Plasmid electrophoretic profile analysis of selected serotype Typhimurium isolates resistant to AKSSuT isolated from nine states in the 1979–1980 antimicrobial drug resistance study ( 46 ). Note the identical or very similar patterns shown in lanes 1, 3, 4, and 9.
Plasmid electrophoretic profile analysis of selected serotype Typhimurium isolates resistant to AKSSuT isolated from nine states in the 1979–1980 antimicrobial drug resistance study ( 46 ). Note the identical or very similar patterns shown in lanes 1, 3, 4, and 9.
Plasmid profile analysis of selected serotype Typhimurium isolates resistant to AKSSuT from a CDC collection of isolates from a 1974–1975 antimicrobial drug resistance study in the United States. Lanes 2, 3, 6, 7, and 9 show identical or very similar patterns. This single clone was responsible for a large proportion of the study isolates during this period.
Plasmid profile analysis of selected serotype Typhimurium isolates resistant to AKSSuT from a CDC collection of isolates from a 1974–1975 antimicrobial drug resistance study in the United States. Lanes 2, 3, 6, 7, and 9 show identical or very similar patterns. This single clone was responsible for a large proportion of the study isolates during this period.
Plasmid profile analysis of serotype Typhimurium isolates from family members (lanes 1 to 4), a calf (lane 5), and calf feed (lane 6) obtained during a salmonellosis outbreak on a calf farm in Mobile, Ala., in December 1973. A serotype Typhimurium isolate with an identical plasmid profile pattern was isolated from a calf in New York State in April 1974 (lane 7). This pattern is the same predominant pattern observed among serotype Typhimurium isolates from the 1974–1975 CDC collection ( Fig. 5.3 ).
Plasmid profile analysis of serotype Typhimurium isolates from family members (lanes 1 to 4), a calf (lane 5), and calf feed (lane 6) obtained during a salmonellosis outbreak on a calf farm in Mobile, Ala., in December 1973. A serotype Typhimurium isolate with an identical plasmid profile pattern was isolated from a calf in New York State in April 1974 (lane 7). This pattern is the same predominant pattern observed among serotype Typhimurium isolates from the 1974–1975 CDC collection ( Fig. 5.3 ).
Antimicrobial drug susceptibility patterns of Salmonella serotype Typhimurium isolates obtained from rural and urban counties in the United States from 1979 to 1980 a
Antimicrobial drug susceptibility patterns of Salmonella serotype Typhimurium isolates obtained from rural and urban counties in the United States from 1979 to 1980 a