For BIO120lec1 2011-2012

1. Chemical control
Microbial control part 2
Lani Manahan January 27,2012

2. Chemical Agents
1. PHENOLICS
2. ALCOHOLS
3. HALOGENS
4. HEAVY METALS
5. QUATERNARY
AMMONIUM
COMPOUNDS
6. ALDEHYDES
7. STERILIZING GASES

3. Chemical Agents
Chemical agent Effectiveness against
Endospores Mycobacteria
Phenolics Poor Good
Quats None None
Chlorines Fair Fair
Alcohols Poor Good
Glutaraldehyde Fair Good

4. PHENOLICS
• First widely used antiseptic and disinfectant
• Joseph Lister (1867): reduced the risk of infection during
operations
• Act by denaturing proteins and disrupting cell membranes
• Phenol / Phenolics: Lysol
• Bisphenols: Hexachlorophene, Triclosan

5. PHENOLICS
PHENOLICS
• ADVANTAGES: effective in the presence of organic material
and remain active on surfaces long after application
• DISADVANTAGE: disagreeable odor and can cause skin
irritation and in some instances brain damage
(hexachlorophene)

6. ALCOHOLS
• Ethanol, Isopropanol
(70-80% concentration)
• Act by denaturing
proteins and possibly by
dissolving membrane
lipids
• 10-15 soaking in alcohol
is sufficient to disinfect
thermometers and small
instruments

7. HALOGENS
• Iodine
– Kills by oxidizing cell constituents and iodinating cell
proteins
– Kill spores at high concentrations
– DISADVANTAGE: a stain may be left (answer = iodophor)
• Chlorine
– Usually for water supply
– Kills by oxidation of cellular materials and destruction of
vegetative bacteria, fungi
– Will not kill spores
– Death within 30 minutes

8. HEAVY METALS
• Mercury, Arsenic, Zinc, Copper
• Used as germicides
• How do they Kill:
– Heavy metals combine with proteins, often with their
sulfhydryl groups and inactivate them
– May also precipitate cell proteins

9. QUATERNARY AMMONIUM COMPOUNDS
• DETERGENTS
– Amphipathic (both polar and non-polar ends)
– Kill by disrupting microbial membranes and denature
proteins
– ADVANTAGE: stable, non-toxic
– DISADVANTAGE: inactivated by hard water
Soap Degerming
Acid-anionic
Sanitizing
detergents
Quaternary ammonium
Bactericidal, Denature proteins,
compounds
disrupt plasma membrane
Cationic detergents

10. ALDEHYDES
• FORMALDEHYDES
– Very reactive molecules that combine with proteins and
inactivate them
– Sporicidal and can be used as sterilants

11. EVALUATION OF ANTIMICROBIAL AGENT EFFECTIVENESS
PHENOL COEFFICIENT TEST
– Best-known disinfectant screening test
– Potency of a disinfectant is compared with that of phenol
– The highest dilution that killed bacteria after a 10 minutes
exposure are used to calculate phenol coefficient
– The higher the phenol coefficient value, the more effective
the disinfectant under this conditions
• The reciprocal of the appropriate test disinfectant dilution is
divided by that for phenol to obtain the coefficient
• Example: phenol dilution = 1/90 and the maximum effective
dilution for disinfectant X = 1/450
• Phenol coefficient = 5

12. EVALUATION OF ANTIMICROBIAL AGENT EFFECTIVENESS
THE USE DILUTION TEST
– Metal rings dipped in test bacteria are dried
– Dried cultures placed in disinfectant for 10 min at 20°C
– Rings transferred to culture media to determine whether
bacteria survived treatment

13. EVALUATION OF ANTIMICROBIAL AGENT EFFECTIVENESS
• Disk diffusion

14. Chemotherapy
Chemotherapeutic agent:
Antibiotic

15. ANTIBIOTICS
• An antibiotic is a product produced by a microorganism or a
similar substance produced wholly or partially by chemical
synthesis, which in low concentrations, inhibits the growth of
other microorganisms
– Antibiotics are medicines used to treat infections caused by
bacteria only
– Infections are usually caused by bacteria or viruses
– Antibiotics, therefore, do not cure all infections
– Many infections like the common cold, flu, mild sore throat
or diarrhea are caused by viruses

16. ANTIBIOTICSTests
Susceptibility
1. Broth dilution - MIC test
2.Agar dilution - MIC test

17. ANTIBIOTICS
Minimal Inhibitory Concentration (MIC)
32 ug/ml 16 ug/ml 8 ug/ml 4 ug/ml 2 ug/ml 1 ug/ml
Sub-culture to agar medium
MIC = 16 ug/ml

18. ANTIBIOTICSTests
Susceptibility
3. Agar diffusion
 Kirby-Bauer Disk Diffusion Test

19. ANTIBIOTICSTests
Susceptibility
“Kirby-Bauer Disk-plate test”
Diffusion depends upon:
1. Concentration
(cont’d)
2. Molecular weight
3. Water solubility
4. pH and ionization
5. Binding to agar

20. ANTIBIOTICS
Susceptibility Tests
“Kirby-Bauer Disk-plate test”
(cont’d)
Zones of Inhibition (~ antimicrobial activity)
depend upon:
1. pH of environment
2. Media components
– Agar depth, nutrients
3. Stability of drug
4. Size of inoculum
5. Length of incubation
6. Metabolic activity of organisms

21. Antibiotic Mechanisms of Action
Alteration of Cell
Membrane
Polymyxins
Bacitracin
Neomycin
Transcription
Translation
Translation

22. • When bacteria are exposed to an antibiotic, they either
die or adapt
• Those that survive carry genes that protect them
against the antibiotic and pass those genes on to other
bacteria
• Since bacteria multiply very quickly and can be easily
spread among people, resistant bacteria can easily
occur in places like hospitals and nursing homes, where
a lot of people are gathered and antibiotic use is high

23. ANTIBIOTICS
Emergence of Antimicrobial Resistance
Susceptible Bacteria
Resistant Bacteria
Resistance Gene Transfer
New Resistant Bacteria

24. Selection for Antimicrobial-
Resistant Strains
Resistant Strains
Rare
Antimicrobial
Exposure
Resistant Strains
Dominant

26. Resistance
Physiological Mechanisms
1. Lack of entry – tet, fosfomycin
2. Greater exit
– efflux pumps
– tet (R factors)
3. Enzymatic inactivation
– bla (penase) – hydrolysis
– CAT – chloramphenicol acetyl transferase
– Aminogylcosides & transferases
4. Altered target
– RIF – altered RNA polymerase (mutants)
– NAL – altered DNA gyrase
– STR – altered ribosomal proteins
– ERY – methylation of 23S rRNA
5. Synthesis of resistant pathway
– TMPr plasmid has gene for DHF reductase; insensitive to TMP

27. Mechanism of Action
CELL WALL SYNTHESIS INHIBITORS
Resistance to β-Lactams – Gram pos.
(cont’d)

28. Mechanism of Action
CELL WALL SYNTHESIS INHIBITORS
Resistance to β-Lactams – Gram neg.
(cont’d)

30. Danger of spread of antibiotic resistant bacteria

31. Danger of spread of antibiotic resistant bacteria
• Antibiotics revolutionised medicine
• The first antibiotic, penicillin, was discovered by Alexander
Fleming in 1929
• It took less than 20 years for, bacteria to show signs of
resistance
• Staphylococcus aureus, which causes blood poisoning and
pneumonia, started to show resistance in the 1950s
• Today there are different strains of S. aureus resistant to
every form of antibiotic in use (MRSA)

32. Danger of spread of antibiotic resistant bacteria

33. Where do we get antibiotic resistant bacteria
• If a patient taking a course of antibiotic treatment does not
complete it
• Or forgets to take the doses regularly, then resistant strains
get a chance to build up
• When antibiotics are used on a person, the numbers of
antibiotic resistant bacteria increase in other members of the
family
• In places where antibiotics are used extensively
e.g. hospitals and farms
antibiotic resistant strains increase in numbers

34. Antimicrobial Resistance Among Pathogens Causing
Hospital-Acquired Infections
Methicillin (oxacillin)-resistant Vancomycin-resistant
Staphylococcus aureus enterococci
30
60
Percent Resistance
25
Percent Resistance
50 20
40
15
30
10
20
10 5
0 0
89
90
91
92
93
94
95
96
97
98
99
00
89
90
91
92
93
94
95
96
97
98
99
00
19
19
19
19
19
19
19
19
19
19
19
20
19
19
19
19
19
19
19
19
19
19
19
20
Non-Intensive Care Unit Patients
Intensive Care Unit Patients
Source: National Nosocomial Infections Surveillance (NNIS) System

35. Antimicrobial Resistance Among Pathogens Causing
Hospital-Acquired Infections
3rd generation cephalosporin- Fluoroquinolone-resistant
resistant Klebsiella pneumoniae Pseudomonas aeruginosa
30
14
Percent Resistance
25
Percent Resistance
12
20
10
8 15
6 10
4
5
2
0 0
89
90
91
92
93
94
95
96
97
98
99
00
89
90
91
92
93
94
95
96
97
98
99
00
19
19
19
19
19
19
19
19
19
19
19
20
19
19
19
19
19
19
19
19
19
19
19
20
Non-Intensive Care Unit Patients
Intensive Care Unit Patients
Source: National Nosocomial Infections Surveillance (NNIS) System

36. Myths & Facts about
Antibiotics and
Respiratory Illness

37. Myths and Facts
• Myth: Taking antibiotics means I or my child
can return to work or childcare sooner
• Fact: Antibiotics do not shorten the duration
of viral illnesses
Everyone should stay home until they are
fever-free and well enough to participate in
activities whether they have a viral or
bacterial illness.

38. Myths and Facts
• Myth: Cold and flu symptoms will feel better
or get better faster on antibiotics
• Fact: Antibiotics cannot ease the symptoms
of viral illnesses; these infections resolve on
their own
Children and adults need extra rest and care,
extra fluids…not antibiotics, symptomatic
relief is helpful

39. Myths and Facts
• Myth: Illnesses with the same symptoms
require antibiotics
• Fact: Illnesses with similar symptoms can be
caused by different germs
Let a healthcare provider decide if the illness is
caused by a virus or bacteria - and if antibiotics
are needed

40. Myths and Facts
• Myth: If I take an antibiotic, I won’t spread my
illness to others
• Fact: Viral illnesses (colds, flu, etc.) usually
spread from person to person before the onset
of symptoms; before a person appears ill
Antibiotics cannot stop the spread of viral
illnesses

41. How do we Stop Antibiotic
Misuse?
• Don’t ask for antibiotics – let your doctor
decide if you need them
• Always take antibiotics exactly as prescribed
• Finish the whole prescription - do not stop
when you feel better
• Never save antibiotics for a future illness –
or share with others

42. ANTIMICROBIAL RESISTANCE:
KEY PREVENTION STRATEGIES
Susceptible Pathogen
Antimicrobial-Resistant Pathogen
Pathogen
Prevent Prevent
Transmission Infection
Antimicrobial Infection
Resistance
Effective
Optimize Use Diagnosis
and
Treatment
Antimicrobial Use

43. 12 Steps to Prevent Antimicrobial
Resistance: Hospitalized Adults
Use Antimicrobials Wisely
Prevent Infection 5. Practice antimicrobial control
1. Vaccinate 6. Use local data
7. Treat infection, not
2. Get the catheters out contamination
8. Treat infection, not colonization
9. Know when to say “no” to vanco
Diagnose and Treat
Infection Effectively 10. Stop treatment when infection
is cured or unlikely
3. Target the pathogen
Prevent Transmission
4. Access the experts 11. Isolate the pathogen
12. Contain the contagion