What does a pathogen have to do? Infect (infest) a host Reproduce(replicate) itself Ensure that its progeny are transmitted to another host

Medical Virology Dept. of Medical Microbiology and Parasitology Shanghai Second Medical University Shanghai, China. E.mail:(xkguoshsmu.edu.cn)

Spirochetes Gram negative Long, thin, helical, motile axial filaments locomotion between peptidoglycan layer/outer membrane runs parallel

Biological Features Structure and chemical composition Developmental cycle Staining properties Antigens Growth and metabolism Characteristics of host-parasite- relationship Classification

Mycoplasmas a group of the smallest organisms that can be free living in nature, Pass bacterial filter and also grow on laboratory media. More than 80 species, belong to Mycoplasmatales of mollicute. 3 families can be divided:

Campylobacter Among the most widespread cause of infection in the world Cause both diarrheal and systemic diseases Campylobacter jejuni

brucella The genus Brucella consists of six species four of which cause human brucellosis Afj 鲁菌病: Brucella melitensis羊布鲁菌, Brucella suis猪布鲁菌, Brucella abortus 牛布鲁菌, and brucella canis犬布鲁菌 Are all intracellular organisms .B neotomaeB ovis

General introduction Gram-negative, obligate intracellular coccobacilli bacteria that infect mammals and arthropods Rickettsiae are transmitted in the arthropods, which serves as both vector and reservior Both dna and rna Is sensitive to antibiotic

MYCOBACTERIUM THIS GENUS IS COMPOSED OF. Strictly aerobic, acid-fast rods, does not Stain well (gram stain indeterminant) DNA has high g+c content, unique cell wall, Mycolic acid carbon chain length c60 Relatively slow growth(two groups) A. RAPID GROWERS (Visible colonies in <5 days B SLOW GROWERS (Visible colonies in 5 days)

Biological Features Aerobic, Gram, noncapsulated, rods Gray-black colonies on tellurite亚碲酸盐 medium o Metachromatic granules Chinese-letter morphology in Gram stain