principle of bacteriologi · bakteriologi. phylogenetic tree of ... monotrichous flagellum on the...
TRANSCRIPT
dr. Agus Eka Darwinata, Ph.DBakteriologi
Phylogenetic Tree of Life
Taxonomy
Bacteria
Proteobacteria
Gammaproteobacteria
Enterobacteriales
Enterobacteriaceae
Escherichia
E. coli
Bos taurus
Mus musculus
Homo sapiens
Staphylococcus aureus
Escherichia coli
Bacillus anthracis
Oryza sativa “Semua organisme memiliki nama yang terdiri dari nama Genus diikuti nama Spesies”
The dimensions of bacteria
Bacterial Structures
Bacterial Structures
Flagella-Bacterial Propellers
(a) Structure in gram-negative cells. (b) Structure in gram-positive cells.
Flagella-Bacterial Propellers
(a) Monotrichous flagellum on the pathogen Vibrio cholerae (10,000×). (b) Lophotrichous flagella on Spirillum serpens, a widespread aquatic bacterium (9,000×). (c) Unusual flagella on Aquaspirillum are amphitrichous and coil up into tight loops (7,500×), (d) Proteus mirabilis exhibits peritrichous flagella (10,000×).
Nonflagellar Appendages: Fimbriae and Pili
(Left) Several cells of pathogenic Escherichia coli covered with numerous fibers called fimbriae (30,000×). (Right) Three bacteria in the process of conjugating. Clearly evident are the sex pili forming mutual conjugation bridges between a donor (upper cell) and two recipients (two lower cells).
Cell Membrane
Bakteri Kecil (tidak tampak dengan mata)
Staining Visible (warna)
Mikroskop Invisible (transparan)
• Hans Christian Gram, a Danish physician developed a staining technique, the Gram stain.
• Commonly used to delineate two different groups of bacteria known as the gram-positive bacteria and the gram-negative bacteria
GRAM STAINING “Most useful staining in clinical microbiology”
More about Gram Staining: https://mikrobiologifkunud.com/gram-biomedik2.html
Morfologi Bakteri
Shape Arrangement
Arrangement of cocci resulting from different planes of cell division. (a) Div is ion in one p lane produces diplococci and streptococci. (b) Division in two planes at right angles produces tetrads and packets. (c) Division in several planes produces irregular clusters.
Arrangement of Cocci
MORPHOLOGI and GRAM STAINING “Clinical-important pathogens”
OXYGEN METABOLISM and GRAM STAINING “Clinical-important pathogens”
or AEROTOLERANT
Bacterial Pathogenesis• Virulence can be quantified by how many organisms
are required to cause disease in 50 percent of those exposed to the pathogen (ID 50 , where I = Infectious and D = Dose), or to kill 50 percent of test animals (LD 50 , where L = Lethal).
• The infectious dose of a bacterium depends primarily on its virulence factors.
• The probability that an infectious disease occurs is influenced by both the number and virulence of the infecting organisms and the strength of the host immune response opposing infection.
Virulence factors are properties that enable a microorganism to establish itself and replicate on or within a specific host
Mechanism of infectious process
• Thepathogenmustovercomediversehostdefenses.
• Bacteriathathaveanouterpolysaccharidecapsule(forexample,StreptococcuspneumoniaeandNeisseriameningi1dis)haveabe>erchanceofsurvivingtheseprimaryhostdefenses
Mechanism of infectious process
• Adherenceenhancesvirulencebypreven@ngthebacteriafrombeingcarriedawaybymucusorwashedfromorganswithsignificantfluidflow,suchastheurinaryandtheGItracts.
• Escherichiacoli,usepilitoadheretothesurfaceofhostcells.
• Neisseriagonorrhoeaeinwhichstrainsthatlackpiliarenotpathogenic.
Mechanism of infectious process
• Invasivenessisfacilitatedbyseveralbacterialenzymes,themostnotableofwhicharecollagenaseandhyaluronidase.
• Theseenzymesdegradecomponentsoftheextracellularmatrix,providingthebacteriawitheasieraccesstohostcellsurfaces.
• Invasionisfollowedbyinflamma@on,whichcanbeeitherpyogenic(involvingpusforma@on)orgranulomatous
Mechanism of infectious process
• Inordertosurviveinsidethehost,bacteriahaveproper@esforironsequestering,havevirulencefactorsthatinhibitphagocytosis,andproducebacterialtoxins.
Bacterial Growth
Bacterial Growth
a single cell of E. coli can give rise to some 10 million cells in just 8 hours
Bacterial Growth
Growth of bacterial colonies on a solid, nutrient surface, for example, nutrient agar. [Note: The doubling time of bacteria is assumed to be 0.5 hr. in this example]
Mechanism of infectious process
Action of Exotoxin
Action of Exotoxin (cont.)
Mechanism of infectious process
Which is the pathogen?
*with several exceptions
Exceptions to Koch's Postulates
Some microbes are obligate intracellular parasites (like chlamydia or viruses) and are very challenging, or even impossible, to grow on artificial media.
Some diseases, such as tetanus, have variable signs and symptoms between patients.
Some diseases, such as pneumonia & nephritis, may be caused by a variety of microbes.
Some pathogens, such as S. pyogenes, cause several different diseases.
Certain pathogens, such as HIV, cause disease in humans only -- it is unethical to purposefully infect a human.
For example, Helicobacter pylori and Salmonella typhi did not satisfy (III) because initially there was no animal models, thus disease could not be reproduced. [To get around this, researchers used "model" pathogens in conjunction with "model" hosts. H. mustelae was used with ferrets as host, and S. typhimurium was used with mice as host. Human volunteer studies and the recent development of an animal model for H. pylori-induced ulcers have now satisfied Koch's 3rd postulate.
Chlamydia pneumoniae fails (I) because it is sometimes not found in diseased (atherosclerosis) individuals. However, the ability to culture Chlamydia pneumoniae from atherosclerotic plaques taken from experimentally infected animals was used to support the role of this bacterium in disease.
Also, Chlamydia sp. or Treponema pallidum are examples of bacteria difficult to grow (II). However, methods for culturing these organisms DO exist. C. botulinum toxin acts at a distance, so bacteria only recovered in stool (if at all), not in nervous system (postulate I). But the fact that toxin reproduces disease is important here, as toxin.
Strep. mutans: Miller originally failed to isolate this pathogen because of anaerobic and multi-species community requirements, thus (II) was initially not satisfied. However, Clark (1924) and Keyes & Fitzgerald (1960's) did succeed in culturing mutans streptococci and could transfer disease through contaminated feces or plaques.
Terima Kasih