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.

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