1. Medical Microbiology
overview & normal
flora
Dr.Ahmed MD

4. Introdution

5. Microorganism are natural existence in the word !
It is necessary for existence of microorganisms
It is necessary for existence of microorganisms in the world !

6. About microorganisms Questions What groups do microorganisms include?
What are the differences among bacteria, viruses and fungi?
What is medical microbiology and why we have to study the course ?

7. Major classification Based on the shape, structure and composition
Eukaryotic microorganisms
Prokaryotic microorganisms
Non-cellular microorganisms

8. Eukaryotes / eukaryotic microorganisms
Cell structures
Cell wall
Cell membrane
Cytoplasm
Nucleus
Nucleic acid
both DNA and RNA
Examples
Fungi

9. 2.FUNGI
Fungi are nonphotosynthetic, generally saprophytic, eukaryotic organisms.
Some fungi are filamentous and are commonly called molds, whereas others (that is, the yeasts) are unicellular.
Fungal reproduction may be asexual, sexual, or both, and all fungi produce pores.
Pathogenic fungi can cause diseases, ranging from skin infections (superficial mycoses) to serious, systemic infections (deep mycoses).

10. Prokaryotes / prokaryotic microorganisms
Cell structures
Cell wall
Cell membrane
Cytoplasm
Nucleoid
Nucleic acid
both DNA and RNA
Six groups
bacteria, mycoplasma, rickettsiae, chlamydiae, spirochetes, and actinomyces
核仁 nucleolus

11. Some bacteria have more than one circular molecule as their genome
Some bacteria have more than one circular molecule as their genome. Vibrios, for example, have two circular chromosomes. Borrellia have linear chromosomes and a wide array of different sized plasmids.

12. Characteristics of prokaryotic and eukaryotic cells
Bacterial Cells
Eukaryotic
Fungal Cells
DNA within a nuclear membrane No
Yes
Mitotic division
DNA associated with histones
Chromosome number 1 ＞1
Membrane-bound organelles
Size of ribosome
70S
80S
Cell wall containing peptidoglycan
histones are highly alkaline proteins found in eukarotic cell nuclei that package .

13. Typical bacteria Bacteria shapes rod, sphere, or corkscrew.
Prokarytoic cells are smaller than eukaryotic cells.
Nearly all bacteria, with the exception of the mycoplasma, have a rigid cell wall surrounding the cell membrane that gives the shape.
The cell wall also determines whether the bacterium is classified as gram positive or gram negative .
External to the cell wall may be flagella, pili, or a capsule.
binary fission.
However, many bacteria exchange genetic information carried on plasmids (small, specialized genetic elements capable of self-replication) including the information necessary for establishment of antibiotic resistance.

14. Atypical bacteria
Atypical bacteria include groups of organisms such as Mycoplasma, Chlamydia, and Rickettsia that, although prokaryotic, lack significant characteristic structural components or metabolic capabilities that separate them from the larger group of typical bacteria.

15. clinically important bacteria according to six distinguishing characteristics.

16. Non-cellular microorganisms
No cell structure
nucleic acid
capsid
Nucleic acid
DNA or RNA
Obligate intracellular parasites
Viruses, prions

17. VIRUSES
Viruses are obligate intracellular parasites that do not have a cellular structure. Rather, a virus consists of molecule(s) of DNA (DNA virus) or RNA (RNA virus), but not both, surrounded by a protein coat.
A virus may also have an envelope derived from the plasma membrane of the host cell from which the virus is released.
Viruses contain the genetic information necessary for directing their own replication but require the host’s cellular structures and enzymatic machinery to complete the process of their own reproduction.
The fate of the host cell following viral infection ranges from rapid lysis and release of many progeny virions to gradual, prolonged release of viral particles.

18. Medically important virus families.

19. Eukaryotes, prokaryotes, and non-cellular microorganisms
内质网Endoplasmic reticulum 线粒体 mitochondrion 血红蛋白 hemoglobin
Prokaryotes

20. Microorganisms (microbes)
Bacteria
related organisms
1-5 m
Prokaryotes
(原核细胞型微生物)
Fungi
Eukaryotes
(真核细胞型微生物)
3-10m
Naked 内质网 endoplasmic reticulum
Genitourinary tract
Non-cell type
Organism（非细胞型微生物）
Viruses nm

21. Relative size of organisms and molecules.

22. colonization
Most infectious disease is initiated by colonization (the establishment of proliferating microorganisms on the skin or mucous membranes). The major exceptions are diseases caused by introduction of organisms directly into the bloodstream or internal organs.

24. Microbial colonization may result in
1) elimination of the microorganism without affecting the host;
2) infection in which the organisms multiply and cause the host to react by making an immune or other type of response or
3) a transient or prolonged carrier state. Infectious disease occurs when the organism causes tissue damage and impairment of body function.

25. Microbiology
The study on living organisms of microscopic size and their relationship with host and environment.

26. Medical microbiology
The study on microbes as pathogens related to human infectious diseases and related infections
The relationship between pathogen
and human host
The agents of infectious diseases belong to five major
groups of organisms: bacteria, viruses, fungi and
parasites (protozoa and helminths)

27. Developments & advances
Discoveries in medical microbiology
Eradication of smallpox
Understanding of relationship between microbes and host at the levels of not only body or tissue but also cells and molecular mechanisms
Progress on methodology in diagnosis, therapy and prevention of lots of infectious diseases
Morbidity incidence mortality

28. Challenges
At least a quarter of all illnesses in the world are infective, 1/10 in developed countries,1/3 in developing or underdeveloped area
Emerging and reemerging infectious diseases or infections
AIDS , SARS , tuberculosis, viral hepatitis …
Hospital infection
Mutations of microbes
Drug resistance
As a medical student, what are you needed to know about the speciality of medical

29. Most basically Important points for a student as following questions:
What microrobes cause what human diseases or infections ?
Why do people get infected with microbes and become ill ? --- pathogenesis !
What about basic properties of microbes ? what do you know strategies for diagnosis, treatment and prevention of infections ?
重点 focal point

53. 1 The primary effect of lactobacilli in the adult vagina is to
A. maintain an alkaline environment.
B. maintain an acidic environment.
C. produce a protective mucus layer.
D. increase fertility.
E. keep the menstrual cycle regular.

54. Correct answer = B.
Lactobacilli produce acid that, in turn, inhibits the growth of potential pathogenic bacteria and fungi. None of the other answers are known to be attributed to lactobacilli

55. 2.A patient presents with severe colitis associated with an overgrowth of Clostridium difficile in the lower bowel.The most likely cause of this condition is
A. botulinum food poisoning.
B. a stomach ulcer.
C. a compromised immune system.
D. antibiotic therapy.
E. mechanical blockage of the large intestine.

56. Correct answer = D.
Antibiotic therapy can reduce normal flora in the bowel, allowing pathogenic organisms normally present in low numbers to overgrow. None of the other answers explains the overgrowth of Clostridium difficile.

57. 3 The predominant bacterial species that colonizes the human skin is
A. Lactobacillus.
B. Candida albicans.
C. Streptococcus pneumoniae.
D. Staphylococcus epidermidis.
E. Bacterioides fragilis

58. Correct answer = D.
Human skin normally contains up to 10,000 Staphylococcus epidermidis per cm2. Other colonizing bacteria may be present but in much lower numbers. Candida albicans is a yeast-like fungus, not a bacterium