MICROBIOLOGY for medical students made easy.ppt

Definition of microbiology

1. Microbiology

2. Micro-organism
•A micro-organism is any living organism too small to
be perceived by the naked eye.
•Micro-organisms are capable of causing disease in
Humans
–Bacteria
–Chlamydiae
–Mycoplasmas
–Viruses
–Fungi
–Rickettsiae

3. •Normal Flora
Bacteria that normally
colonize the human
body without causing
disease are referred
as normal flora
•Pathogens
While those that
cause disease are
referred to as
pathogens.

4. Structure
of a
Bacterial
Cell

5. Types of
Bacteria
•As a single
•In pairs (diplococci)
•In chains (streptococci)
•In cluster (Staphylococci)
•Rod-shaped (bacilli)
•Short rounded (coccobacilli)
•Spirochetes

6. Classification of Bacteria
Gram Staining
•Gram Positive
•Gram Negative
Oxygen Requirement
•Aerobes
•Anaerobes
•Obligate
•Facultative

7. Gram Staining

8. Gram +ve Gram -ve

9. Common Pathogens
Gram-Positive Aerobes
Staphylococci
•S. aureus
•S.epidermidis
Sterptococci
•S.pyogenes
•S.pnemoniae
•S.agalatiae
Enterococci
•E.faecalis
•E.faecium
Bacilli
•Cornynebacterium sp.
•Listeria sp.

10. Common Pathogens
Gram-Negative Aerobes
Enterobacteriaceae
•Escherichia coli
•Klebsiella sp.
•serratia sp.
•Enterobacter sp.
•Proteus sp.
•Providencia sp.
•Citrobacter sp.
•Shigella sp.
•Salmonella sp.
Non-enteric
•Haemophilus
influenzae
•legionella sp.
•Neisseria sp.
•Moraxella catarrhalis
•Psedomonas sp.

11. Common Pathogens
Anaerobes
Gram-positive
•Clostridium sp.
•Peptostreptococcus sp.
•Peptococcus sp.
Gram-Negative
•Bacteriodes sp.

12. Infections
•Body infection is the term used to describe any
proliferation of pathogenic micro-organisms in the
human body.
Development of infectious disease
•Infection
•Incubation
•Prodrome
•Clinical illness
•Resolution

13. Classification of Infections
Duration of Symptoms
•Acute infection
•Chronic infection
Number and type of pathogens
•Unimicrobial infection
•Polymicrobial or mixed
infection.
Environment of exposure
•Community-acquired
infection
•Nosocomial infection
Source of Pathogens
•Primary infection
•Secondary infection
•Superinfection

14. Nomenclature of Infectious Diseases
Lower respiratory tract
•Bronchitis
•Pneumonia
Upper respiratory tract
•Otitis media
•Phyringitis
•Sinusitis
Bone and joint
•Oesteomyelits
•Septic arthritis
Cardiovascular system
•Endocarditis
•Septicaemia
Urinary tract
•Urethritis
•Cystitis
•Pylonephritis
•Prostatitis
Intra abdominal structures
•Appendicitis
•Peritonitis
•Diverticulitis
•Cholecystitis
•Cholangitis
Female Genitalia
•Endometritis
•Salpingitis
•Oophoritis
•Amnionitis
•Pelvic cellulitis
Skin and soft Tissues
•Dermatitis
•Cellulitis
•Fasciitis

15. Antibiotics
Chemical substance produce by one species of
organisms that are capable of suppressing the
growth of other microorganisms are called antibiotics.

16. Although there are technical definitions that distinguish
among them and are commonly used interchangeably to
refer to any agent that kills or inhibits the growth of
bacteria
•Antibiotic
•Antimicrobial
•Antibacterial
Antibiotics

17. Mechanisms of Antibiotic Action
Interference with bacterial cell wall synthesis
•Penicillin
•Cephalosporins
•Beta-lactamase inhibitor combination
•Monobactams
•Carbapenems
•Glycopeptides
Interference with bacterial protein synthesis
•Aminoglycosides
•Tetracycline
•Macrolides
•Lincomycins
Interference with genetic replication
•Quinolones
•Metronidazole
Interference with folic acid synthesis
•Sulfonamides
•Trimethoprim

19. Susceptibility Testing
•Test used to determine which antibiotic can provide
activity against a particular pathogen are called
susceptibility test.

20. •Susceptible: Bacteria that are inhibited or killed
in vitro by an antibiotic are said to be susceptible
or sensitive
•Moderate or intermediate: Bacteria that are
susceptible only to a high dose of an antibiotic
are said to exhibit moderate or intermediate.
•Resistant: Bacteria that are unaffected by an
antibiotic are termed resistant
Susceptibility Testing

22. Two methods commonly used to
determine bacterial susceptibility
Disk diffusion method
Determine whether or not an
organism is susceptible to a
known concentration of
antibiotic
Serial dilution method
Determine the minimum
concentration of an antibiotic
that will inhibit the cultured
microorganism.

23. Disk diffusion method /
Serial dilution method

24. Mueller Hinton Blood Agar

27. Important Terms
•MIC: The lowest concentration of antibiotic that will inhibit the
growth of bacterial cells in a standardized sample.
•MBC: The lowest concentration of antibiotic that will kill 99.9%
bacterial cells in standardized sample
•Breakpoint: The breakpoint of antimicrobial agent is a standard
concentration below which all pathogens are considered
susceptible.
•Serum Dilution Conc: The lowest dilution of the patient’s
serum that kills a standard inoculum of the infecting organism.

28. Initiation of Antibiotic Therapy
•Empiric (Presumptive)
Begin prior to identification
Based on physician’s experience with similar infections.
•Prophylactic
Anticipation of infection or increased risk of infection.
Begin immediately prior to surgery and discontinued within 24 hours.
•Definitive
Based on laboratory identification / results.

29. Antibiotic Selection Criterion
•High clinical efficacy
•Effective against known
or suspected pathogens
•Low toxicity
•No drug allergic effect
•Minimal patterns of
resistance
•Patient’s underlying
medical conditions
•Condition of host
defenses
•Convenience of dosing
•Minimal drug interactions
•Cost of therapy
•Route of administration

30. Antibiotic Combination Therapy
Rationale
•Extend spectrum of antibacterial coverage
•Treat resistant organism
•Provide added coverage against opportunistic infection
•Prevent resistance
Synergistic combinations
•Effect of two agents administered together is greater than the sum
of their individual effects
•Clinically , evidenced by 4-fold reduction in MIC values
Antagonistic combinations
•Effect of two agents administered together is less than the sum of
their individual effects.
•Clinically, evidenced by 4-fold increase in MIC values

31. Antibiotic Resistance
•Some microorganisms have developed various
mechanisms that enable them to survive in the
presence of an antibiotic. This ability is called
antibiotic resistance or simply, resistance.

32. Primary Mechanisms of
Resistance
•Alteration in membrane permeability
•Alterations in antibiotic binding sites
•Production of enzyme capable of
inactivating antibiotic agents.

34. Secondary Mechanisms of
Resistance
The three mechanisms by which resistance
develops and spread among bacteria:
•The emergence of resistance as a result of
mutations in the bacterial chromosome
•The induction of resistance as a result of
exposure to antibiotics
•The transfer of resistance to previously
susceptible bacteria.

36. Latin America
MRSA 40%
VRE 12%
ESBL (K.pneumoniae) 46%
Asia Pacific *
MRSA 36%
VRE 15%
ESBL (K.pneumoniae) 23%
United States
MRSA 55%
VRE 28%
ESBL (K.pneumoniae) 14%
Europe
MRSA 27%
VRE 9%
ESBL (K.pneumoniae) 23%
AB Resistance Rates a Significant Problem in All Regions
Source: Unpublished SENTRY Data 2006; (*2004 published data)
Hospital-Wide Resistance Rates

37. Need for Newer & Stronger AB
•Effective against Resistant Organisms
•Single agent covers all
•Minimum side effects
•Better compliance
•Easier dosage schedule
•An option for empiric use

38. Alteration in membrane permeability

39. Alterations in antibiotic binding sites

40. Efflux

41. Production of enzyme capable of inactivating
antibiotic agents.