Antimicrobial Sensitivity Testing

1. 10. SUSCEPTIBILITY TESTING
AND
RESISTANCE MECHANISMS

2. CONTENT
1- What is AST ?
2- Why and when to perform AST ?
3 - Evolution of the resistances
4- Classification of antibiotics
5- The different manual techniques
6- Disk diffusion
7- Antibiotics action mode
8- Resistance mechanisms of bacteria
8 - 1 Enterobacteriaceae
8 - 2 Staphylococci
8 - 3 Streptococci
9- Choice of antibiotics panel composition
10- Interest of Expert System
11- Study of phenotypes

3. WHAT IS IT ?
1 - Antimicrobial Susceptibility Testing

4. Recover
quickly
THE PATIENT

5. Rapid diagnosis
Effective treatment
THE CLINICIAN

6. Reliable answers
Least possible risk
THE MICROBIOLOGIST

7. Microbiologist's answer
The ideal result would be :
 Therapy with antibiotic A will be successful
 the bacteria is Susceptible to the antibiotic
 Therapy with antibiotic B will lead to a failure
 the bacteria is Resistant to the antibiotic

8. Microbiologist's answer
Failure
?
Success

9. Microbiologist's answer
Sucess of therapy depends on :
 Resistance of bacteria
 Site of infection
 Dosage
 Patient

10. Microbiologist's answer
Based on the :
 Activity of the antibiotic for this strain
 Pharmacokinetics of the drug
 Normal dosage
 Results of clinical studies

11. How to do it ?
 Determine antibiotic activity in vitro
 Interpret results for in vivo : potential risk of success
and failure

12. 2 - Why and when to perform a
susceptibility testing?

13. WHY PERFORM A SUSCEPTIBILITY TEST ?
In vitro susceptibility
is one of the prerequisites
for in vivo efficacy of antibiotic therapy
To orient individual therapeutic
decisions

14. WHY PERFORM A SUSCEPTIBILITY TEST ?
 To have an epidemiological follow-up
at different levels : wards, department, region or
country
 To adapt empiric antibiotic therapy
 To check the clinical spectrum of antibiotics
But also :
helps for healthcare decisions,
and prevention program

15. WHY PERFORM A SUSCEPTIBILITY TEST ?
THERAPY EPIDEMIOLOGY
DUAL INTEREST

16. WHEN TO PERFORM
A SUSCEPTIBILITY TEST ?
- Each time a bacteria considerated to be responsible for an
infection is isolated from a bacteriological specimen
- The technician selects the bacterium among normal flora
(if multimicrobial specimen)
 MICROBIOLOGIST APPROACH

17. WHEN TO PERFORM
A SUSCEPTIBILITY TEST ?
- SEVERE INFECTIONS : septicemia, meningitis,
pyelonephrititis, bronchopneumopathy....
- CHRONIC INFECTIONS : urinary infections, otitis
- INFECTIONS ON RISK PATIENTS : Old people, pregnant
women, kidney and cardiac failure,
immunosuppressed patients
- THERAPEUTIC FAILURE
- INFECTIONS ON RECENTLY HOSPITALIZED PATIENT :
multiresistant bacteria
 CLINICIAN APPROACH

18. Sometimes microbiologists cannot determine if AST is
required, without obtaining the clinical information that
only a clinician can provide.
WHEN TO PERFORM
A SUSCEPTIBILITY TEST ?
Example: a commensal bacterium can cause
an infection in an immunocompromised patient
or in a specific body site.
 importance of patients data information,
and clinical symptoms...

19. WHEN TO PERFORM
A SUSCEPTIBILITY TEST ?
NEED FOR CLOSE WORKING
RELATIONSHIP BETWEEN
MICROBIOLOGISTS CLINICIANS

20. CAN WE PREDICT
SUSCEPTIBILITY OR RESISTANCE
OF A BACTERIUM TO AN ANTIBIOTIC
?

21. Direct impact on patient recovery
The prescription of first-line
antibiotics is poorly adapted
Recovery ???
10 % of therapeutic failure

22. ANTIBIOTICS
Natural resistance Systematic sensitivity
ANTIBACTERIAL ACTIVITY SPECTRUM
Each antibiotic is characterized by a natural spectrum :
of some bacterial species of some bacterial species

23. NATURAL RESISTANCE
Permanent characteristic of all strains of the
same bacterial species
 stable
 predictable
 helps for confirmation of identification

24. EXAMPLES OF NATURAL RESISTANCE
Antibiotics
Amino penicillin
penicillin G
Cephalosporin 1st G
Cephalosporin 2nd G
Cephalosporin 3rd G
Nalidixic acid
E coli
Salmonella
Klebsiella
Enterob
Serratia
Natural Resistance
Amino penicillin
+ Betalactamase
inhibitor
Pseudo
aeruginosa
Entero
cocci
staph

25. NATURAL RESISTANCE
 Wild Strain :
= bacteria with just its natural resistance
= No acquired resistance yet

26.  Characteristic specific to some strains
 The genotype has been modified by gene
mutation or gene acquisition.
ACQUIRED RESISTANCE

27. ACQUIRED RESISTANCE
Evolutive and unpredictable characteristic
of the isolated bacterial strain
 justifys the use of susceptibility testing
Example :
E. coli  wild strain : Amoxicillin (S)
 Now : 30 - 60% Amoxicillin (R)

28. ACQUIRED RESISTANCE
Given the evolution of acquired resistance:
 the natural spectrum of activity is no longer sufficient to guide the
choice of treatment.
Example : Acute otitis caused by Pneumococci with
decreasing susceptibility to Penicillin G :
- 1985 : < 1%
- 1998 : 10 - 50% (depends on the country)

29. CLINICAL SPECTRUM OF ACTIVITY
Bacteriological data :
natural spectrum + acquired resistance
Pharmacokinetic data
Clinical data
 For each antibiotic, bacteria are divided in 3 classes : S, I, R
Frequent updates : take into account the evolution of the
resistances
=
+
+

30. 3 - Evolution of resistance

31.  Resistance must be monitored
 Today, the over-use of antibiotics increases the
frequency of resistant strains.
 The antibiotic does not create resistance
but selects resistant bacteria by eliminating the
commensal and susceptible bacteria.
EVOLUTION OF RESISTANCE

32. EVOLUTION OF RESISTANCE
LARGE ANTIBIOTIC USE
POORLY ADAPTED
TREATMENT
THERAPY FAILURE
INCREASE IN
RESISTANCE
PRESSURE OF SELECTION

33. Situation of Methicillin Resistant S. aureus in Europe
33.6%
0% 1.5%
0.3%
1.8%
5.5%
21.6%
25.1%
30.3% 34.4%
Marty, V. Jarlier- Surveillance des bactéries multirésistantes : Justification, rôle du laboratoire, indicateurs,
données françaises récentes - Path Biol April 1998 ; 217-26
A few figures on resistance...

34. Evolution of bacterial resistances
Community - acquired in Europe
1975
90
30
20
10
0
1985 1998
% of resistant strains
Strepto A / Penicillin G
H . influenzae / Ampicillin
S. Pneumoniae/ Penicillin G
S .pneumoniae / Erythromycin
E . coli / Ampicillin
S. aureus / Penicillin G
40
80
70
Questions and answers on ST : J . louis Tissier

35. Evolution of bacterial resistances
Hospital - acquired in Europe
1975
40
30
20
10
0
1985 1998
% of resistant strains
Enterococcus / Vancomycin
K. pneumoniae / 3rd generation cephalo.
P. aeruginosa / Fluoroquinolones
E. cloacae / 3rd generation cephalo.
S. aureus / Oxacillin
E. coli / Ampicillin
Questions and answers on ST : J louis Tissier

36. 4 - Classification of antibiotics

37. DEFINITION OF AN ANTIBIOTIC
 Natural substance produced by molds and bacteria
 Inhibits or destroys other bacteria.
All substances with an antibacterial activity
(produced by synthesis or semi-synthesis)

38.  B- Lactams :
- Penicillins / Inhibitors
- Cephalosporins
- Carbapenems
- Monobactams
 Aminoglycosides
 Cyclins
 Quinolones
 MLSK
 Polypeptides
 Imidazoles
 Rifamycins
 Phenicols
 Glycopeptides
 Furanes
 Sulfonamides
 Miscellaneous
SIMPLIFIED CLASSIFICATION OF
ANTIBIOTICS
13 families

39. b LACTAMS
Marker Gram (+) Gram (-)
- PEN G Penicillin G Nat. R.
- PEN M Oxacillin Nat. R.
- PEN A Amox - Ampi
- PEN C Ticarcillin
- PEN-U Piperacillin
Penicillins
Systematic S of S. pyogenes

40. b LACTAMS
Marker Gram (+) Gram (-)
- 1st generation Cefalotin Nat R. of E. faecalis
Cefaclor
- 2nd generation Cefuroxime
- Cephamycins Cefoxitin
Cefotetan
- 3rd generation Cefotaxime
Ceftazidime
- 4th generation Cefepime
Cefpirome
Cephalosporins

41. These enzymatic inhibitors have no true antibacterial activity,
but a strong affinity for b-lactamases :
Clavulanic acid
Sulbactam
Tazobactam
Aim : blocks beta-lactamases
Combination b-lactams - b-lactamase inhibitor :
- Group 1 Amoxicillin + Clavulanic Ac.
Ampicillin + sulbactam
- Group 2 Ticarcillin + Clavulanic Ac.
Piperacillin + tazobactam
- Group 3 Sulbactam + 3rd generation cephalosporins
Never
alone !
INHIBITORS OF BETA-LACTAMASES

42. b LACTAMS
Carbapenem
 Imipenem
 Meropenem
Monobactam Marker Gram (+) Gram (-)
Aztreonam Nat. R.

43. AMINOGLYCOSIDES
Marker
Gentamicin, Tobramycin, Nat. R. of
Amikacin, Streptomycin, Streptococci
Kanamycin, Netilmicin, and Nat. R. of
Neomycin, Spectinomycin, Anaerobes
- G(-) Bacilli : test GEN, TOB, AKN, NET
- Enterococci and deficient Streptococci :
test STR HC, GEN HC, KANA HC
(Aminoglycosides high concentration)
- Staphylococci : test GEN, TOB, KAN
 NCCLS recommendations:

44.  Tetracycline
 Doxycycline
 Minocycline
Extended spectrum
 Tetracycline is the MARKER for all cyclines
but for certains organisms doxycycline and
minocycline are more susceptible than tetracycline
CYCLINES

45. QUINOLONES
Marker Gram (+) Gram (-)
Quinolones Nalidixic acid Nat. R.
Pipemidic acid
Norfloxacin
Pefloxacin
Fluoroquinolones Ofloxacin
Ciprofloxacin

46. M.L.S : MACROLIDES / LINCOSAMIDES /
STREPTOGRAMINS
Marker Gram (+) Gram (-)
Macrolides Erythromycin Nat. R. except
Haemophilus
Lincosamides Natural resistance
Clindamycin for Staph / Enterococci
Streptogramins Quinupristin/
dalfopristin*
 *Synercid

47. NITRO - IMIDAZOLES
 Metronidazole Active on anaerobes, parasites
RIFAMYCINS (ANSAMYCINS)
 Rifampicin Used in anti-stapylococci
eye lotions, gonococci, TB
POLYPEPTIDES
Marker Gram (+) Gram (-)
Colistin Nat. R. P. aeruginosa
Bacitracin = Syst. S.

48. PHENICOLS
 Chloramphenicol
Extended spectrum : Typhoid fever, Gonococci,
bronchopulmonary infections
GLYCOPEPTIDES
Marker Gram (+) Gram (-)
- Vancomycin Nat. R.
- Teicoplanin

49. FURANE
 Nitrofurantoin
Urinary infections : Gram (+) cocci, Enterobacteriaceae
Natural resistance for P.mirabilis
SULFONAMIDES (FOLATE PATHWAY INHIBITORS)
Marker Gram (+) Gram (-)
Cotrimoxazol P. aeruginosa
= Nat. R.
Sulfamides
Digestive, genital and urinary infections

50. MISCELLANEOUS
 Fusidic acid (French drug)
Local anti-staphylococcal treatment
 Fosfomycin
- Cystitis for Gram + cocci and Gram- bacilli : «Monuril»
- Systemic infection (multiresistant bacteria)
 Natural resistance for Staphylococcus saprophyticus

51. 5 - The different manual
techniques
 Reference technique
 Routine techniques

52. MIC DETERMINATION
Definition : Minimum Inhibitory Concentration of an
antibiotic inhibiting the visible growth of a bacterium
overnight in standardized conditions for rapid growth
bacteria.
 Bacteriostatic effect of an
antibiotic on a bacterium

53. Mueller
Hinton 1 ml
1 ml
0 0.5 1 2 4 8 16 µg/ml
107 CFU
35°C - 16 to 20 hrs
0 0.5 1 2 4 8 16 µg/ml
0 0.5 1 2 4 8 16 µg/ml
MIC DETERMINATION
liquid medium
Reference technique for NCCLS*
*National Committee for Clinical Laboratory Standarts
MIC =

54. MIC DETERMINATION

55. MBC DETERMINATION
Definition : Minimum Bactericidal Concentration
 Bactericidal effect of an
antibiotic on a bacterium

56. MBC - PROCEDURE
10 µl
0 µg/ml
4 µg/ml
8 µg/ml
16 µg/ml
MBC =
0 0.5 1 2 MIC = 4 8 16 µg/ml
35°C - 16 to 20 hrs

57. Sub-cultured
MBC - PROCEDURE

58. MIC - MBC
MIC MBC
Bactericidal
MIC MBC
Bacteriostatic
1 2 8 16 32 64 128
4
1 2 8 16 32 64 128
4

59. CATEGORIZATION OF STRAINS
 2 concentrations set by the NCCLS :
 c = low breakpoint
 C = high breakpoint
 According to the following criteria :
- Bacteriological studies
- Pharmacokinetics
- Clinical experience
Breakpoints :

60. c C
S I R
MIC < c c < MIC < C MIC > C
CATEGORIZATION OF STRAINS

61. ROUTINE TECHNIQUES
 Disk diffusion
 ATB Strips
 ViteK 2
Compact
 E test

62. DISK DIFFUSION

63. DIFFUSION
CHARACTERISTICS
Diffusion
Radial
in depth
surface
base
Agar
(4mm)
Diffusion of antibiotic

64. DIFFUSION
READING
Measure
MIC
Zone
Diameter
Sensitive Intermediate Resistant

65. DIFFUSION
Methodology
1 hour
< 15 mins
Streak twice
5-15 mins
10 mins
30°C
37°C
37°C
CO2
4°C
0.5 McF

66. DIFFUSION CONTROL
 Control of each cartridge of antibiotics
 Stability after opening the cartridge :
1 week
(CLSI and CA-SFM recommendations)

67. DIFFUSION
Summary
 Not ready to use
 Flexibility of antibiotics to be tested
 Solid technique
 Visual reading
 Indirect technique

68. 24 Hrs ATB STRIPS
bioMérieux

69.  Thermoformed transparent plastic strip consisting
of 32 cupules
 Cupules containing dehydrated antibiotics
 Inoculation medium : ATB medium
(semi solid Mueller-Hinton)
 2 empty cupules for individual antibiotic tests
24 Hrs ATB STRIPS

70. 24 Hrs ATB STRIPS
 READING OF A BACTERIAL GROWTH : turbidity
 DETERMINATION OF S-I-R DIRECTLY
 READING : VISUAL OR AUTOMATIC
 For manual customers
 Or customers equipped with mini API or ATB Expression system
(automatic reading)

71. 24 Hrs ATB STRIPS
 Principle :
Each antibiotic (A, B,
C, D…) is tested at 2
different
concentrations
(Breakpoints: c, C)
c C
C
B
A
0 Growth control
S (Susceptible)
R (Resistant)
I (Intermediate)
= No bacterial
growth
= Bacterial
growth

72. 24 Hrs ATB STRIPS
 Susceptible strain : MIC < c
The antibiotic tested is active on the bacteria
 Intermediate strain : c < MIC < C
The bacteria is not affected by the treatment at usual
doses,
but may be affected by a high-dose intravenous or local
treatment.
 This is the risk range.
 Resistant strain : MIC > C
The bacteria resists to the strongest concentrations.
The antibiotic will not be active in vivo.

73. 24 Hrs ATB STRIPS
8
32
32
32
8
8 MIC < 8 (S)
8 < MIC  32 (I)
MIC > 32 (R)
 example : CFT 8 - 32 mg/l

74. VITEK 2 COMPACT
BIOMERIEUX

75. MICROSCAN 24 Hrs CHARACTERISTICS
 Broad range of MIC concentrations is tested for
each antimicrobic which gives information on
emerging and low level resistance.
20 antimicrobics in each card let the lab give a
wide response. This is also a good basis for the
deduction function of AES:3 - 6 concentrations for
each antibiotics
A rapid response can be used by clinicians when
they are making the change from empiric to
directed therapy.

76. SYSTEM CONFIGURATION
CAPACITY= 15/30 /60 cards
PC WINDOWS XP DENSICHEK
inoculum Standardisatio
CODE BARR

77. E-TEST

78. ME
E
256
6
3
1.5
.75
.38
.19
.094
.047
.023
192
128
64
32
16
8
4
2
1.0
.50
.25
.125
.064
.032
.016
96
48
24
12
E-TEST : CHARACTERISTICS
reading scale
exponential and continuous
antibiotic gradient
antibiotic code

79. E.TEST
READING

80. E-TEST PROCEDURE
McF regarding ID
5 mins at 37 °C
Streak twice
< 15 mins
saline water
30°C
37°C
37°C
CO2

81. 6 -DISK DIFFUSION

82. The way the microbiologist thinks :
 the reference method
 reliable
 easy-to-use
 cheap
 flexible

83. LET’S LOOK AT EACH POINT ...

84. Disk diffusion is a commonly used
method
not the reference one
REFERENCE METHOD ?

85. MIC is the REFERENCE
Disk Diffusion is an INDIRECT
METHOD
REFERENCE METHOD ?

86. REFERENCE METHOD ?
Do not use disk diffusion
for
Anaerobes
Yeasts

87. "For generation of reproducible results, all technical
details of the test procedure must be carefully
standardized and controlled"
NCCLS Dec. 93 - Vol.13 N°24 P.1
RELIABILITY ?

88. RELIABILITY ?
 Depends on :
 Choice of media
 Agar thickness
 Standardization of the inoculum
 Disk stability

89. Mueller Hinton
HTM
GC Supplement
MH + 5% Sheep
Blood
Chocolate
8
Chocolate +
Supplement 8
Enterobacteriaceae
Pseudomonas aeruginosa
Staphylococci
Enterococci
Haemophilus
Gonococci
Pneumococci Others
8
NO
1- Choice of the medium
NO
NO

90. Diffusion of the
antibiotic
Agar
(4 mm)
2- Agar thickness

91. Media too thin
excessive diffusion
Media too thick
too little diffusion
Media sloping
uneven diffusion
Disk not flat
too little diffusion
Plate too wet
surface diffusion
2- Agar thickness

92. 0.5 Mac Farland
3- Standardization of the inoculum

93. Inoculum too heavy
Inoculum too light
Inoculum uneven
3- Standardization of the inoculum

94. Time (months)
1 18
2 weeks
70%
150%
% Antibiotic activity
4 - Disk stability

95. - Use disks within 5 days
- Daily quality control for each disk
4 - Disk stability

96.  Adequate media
 4 mm-thick media
 Standardized inoculum
 Daily quality control
RELIABILITY ?

97. RELIABILITY ?
 Correct reading ?
Measure the diameter

98. RELIABILITY ?
Human error
and subjectivity
make
standardization
difficult

99. Interpretation is SUBJECTIVE
About 5% of discrepancies
RELIABILITY ?

100. Difficult to perform
EASY-TO-USE ?

101. CHEAP ?
 Cost of disk diffusion =
Reagent cost
(media + disks)
Labor cost
QC cost
+ +

102. When you can report on so many
antibiotics by testing few, why do
you need more flexibility?
FLEXIBILITY ?

103. Drug Tested Drug reported
Penicillin G All Penicillin G
Ampicillin All Penicillin A
Cephalothin All Cephalosporins 1st Gen.
Piperacillin Mezlocillin
Cefuroxime Cefamandole, Cefomicin
Cefotaxime Ceftriaxone, Ceftizoxime
Oxacillin All beta-lactams
Norfloxacin Ofloxacin, Lomefloxacin
(Urinary Tract Infection)
Tetracycline All Tetracyclines
Use of markers
FLEXIBILITY ?

104. Common Method
Cheap reagent
Reliable technique
Easy-to-use
Flexible
but
Depends on strictly
following the procedure
and the lab technologist
Quality control
difficult
Costly method
Time consuming
Everybody uses
a different technique
but
but
but
but
CONCLUSION

105. 7 - Antibiotics action mode

106. ANTIBIOTIC ACTION MODES
 Aminoglycosides
 Macrolides
 Tetracyclines
 Chloramphenicol
R
R
E
Chromosome
 Quinolones
 Nitro-imidazoles
 b Lactams
 Fosfomycin
 Glycopeptides
 Sulfonamides
1
2
3
4
= DNA gyrase
E
R = Ribosomes

107. External
membrane
Peptido
glycane
Cytoplasmic
Membrane
Cytoplasm
PS
PS
P P
PBP
PBP
PO
PS = Periplasmic space
P = Permeases
PBP = Penicillin binding proteins PO = porines
PO
Polysaccharides
Phospholipids
(Except Neisseria and Haemophilus)
Gram + Gram -
BACTERIA CELL-WALL

108. External
membrane
Hydrophilic
Antibiotic
Lipophilic
Antibiotic*
Lipophilic
Antibiotic*
Hydrophilic
Antibiotic
Peptido
glycane
Cytoplasmic
Membrane
Cytoplasm
PS
PS
P P
PBP
PBP
PO
* = fusidic acid, Macrolides, Rifampicin
Intracytoplasmic targets Intracytoplasmic targets
PO
Polysaccharides
Phospholipids
(Except
Neisseria and
Haemophilus)
Gram + Gram -
ANTIBIOTICS ACTION MODES
PS = Periplasmic space
P = Permeases
PBP = Penicillin binding proteins PO = porines

109. External
membrane
Antibiotic
active on PBP
Hydrophilic
Antibiotic
active on PBP
Peptido
glycane
Cytoplasmic
membrane
Cytoplasm
PS
PS
P P
PBP
PBP
PO
PO
Polysaccharides
Phospholipides
(Except
Neisseria and
Haemophilus)
Gram + Gram -
= b lactamases
ACTION MODE OF BETA-LACTAMS
PS = Periplasmic space
P = Permeases
PBP = Penicillin binding proteins PO = porines

110. External
membrane
Lipophilic
antibiotic *
Lipophilic
antibiotic *
Peptido
glycane
Cytoplasmic
membrane
Cytoplasm
PS
PS
P P
PBP
PBP
PO PO
Polysaccharides
Phospholipides
(Except Neisseria
and
Haemophilus)
Gram + Gram -
50S
50S
ACTION MODE OF MACROLIDES

111. Aminoglycosidases:
AAC
APH
ANT
External
membrane
Hydrophilic
antibiotic
Hydrophilic
antibiotic
Peptido
glycane
Cytoplasmic
membrane
Cytoplasm
PS
PS
P P
PBP
PBP
PO
PO
Polysaccharides
Phospholipids
(Except
Neisseria and
Haemophilus)
Gram + Gram -
30S
30S
ACTION METHOD OF AMINOGLYCOSIDES

112. External
membrane
Hydrophilic
antibiotic
Hydrophilic
antibiotic
Peptido
glycane
Cytoplasmic
membrane
Cytoplasm
PS
PS
P P
PBP
PBP
PO
PO
Polysaccharides
Phospholipids
(Except
Neisseria and
Haemophilus)
Gram + Gram -
DNA gyrase
DNA gyrase
ACTION METHOD OF QUINOLONES

113. 8 - Resistance mechanisms of
bacteria

114. RESISTANCE MECHANISMS
MODIFICATION OF THE TARGET
EFFLUX PHENOMENON
ENZYME PRODUCTION
IMPERMEABILITY
resistance of Enterobacteriaceae to
macrolides
1- b lactamases inactivating b lactams
2- Enzymes degrading aminoglycosides
resistance of Enterobacteriaceae to
tetracycline and quinolones
1- Penicillin binding proteins for b lactams
(PBP)
2- Ribosomes for macrolides
3- DNA gyrase for quinolones
R
R
E
Plasmid
Chromosome

115. RESISTANCE MECHANISMS
P P
PBP
PBP
PO PO
(Except
Neisseria and
Haemophilus)
Gram + Gram -
ENZYMES
ENZYMES
ENZYMES
ENZYMES
Hydrophilic
antibiotic
Hydrophilic
antibiotic
EFFLUX
EFFLUX
Antibiotic
active on PBP
Hydrophilic
antibiotic
active on PBP
Lipophilic
antibiotic
Decreasing size
of porine
Mutation of
DNA gyrase
Mutation of
DNA gyrase
Mutation of
ribosome
Mutation of
ribosome

116. GENETIC SUPPORT OF RESISTANCE
1) The chromosome
 stable
 vertical transmission (to descendants)
 no horizontal transmission
(not transferable from one bacteria to another)

117. GENETIC SUPPORT OF RESISTANCE
2) The Plasmid
 Unstable in the absence of the antibiotic which
selected it
 Transferable from one bacterium to another, sometimes
between different species

118. GENETIC SUPPORT OF RESISTANCE
CHROMOSOME
PLASMID
Natural resistance :
- stable
- no horizontal transmission
Acquired resistance :
- unstable
- risk of horizontal transmission

119. CROSS AND ASSOCIATED RESISTANCE
 Cross resistance
The same resistance mechanism affects several antibiotics within a
same family.
Eg : a Gentamycin-resistant staphylococci is resistant to all aminoglycosides.
 Associated resistance
affects several antibiotics in different families
Eg : Associated resistance of Enterobacteriaceae to b-lactams and aminoglycosides
(ESBL and AAC 6').

120. 8.1 - Main resistance mechanisms of
Enterobacteriaceae

121. b-Lactamases
Inducible
Chromosomic
Constitutive
Plasmidic
ENZYMATIC
RESISTANCE
Enzymes produced by the bacteria to
inactivate the antibiotic

122. Constitutive : constant level
of prodution independent of
the presence of an inductor
Synthesis of b-Lactamases
Inducible : produced in small
quantities but increases in the
presence of the inductor
Eg : Cefoxitin, Imipenem
Presence of
the antibiotic
in the periplasmic space

123. b-Lactamases
 Penicillinase
 Cephalosporinase
 ESBL : Extended spectrum B-Lactamase
 IRT : TEM resistant to inhibitors

124. b-Lactamases
Pase
Case
ESBL
Chromosome Plasmid




IRT 

125. NATURAL RESISTANCE PHENOTYPES
Group I : E. coli, Proteus mirabilis, Salmonella, Shigella
 Wild strain : high level of susceptibility but very
low level of cephalosporinase for E. coli, Shigella
Group II : Klebsiella spp, Citrobacter koseri,
Citrobacter amalonaticus, Escherichia hermanii,
 Wild strain : natural penicillinase (Nat. Pase).
 K. oxytoca : hyper production of natural Pase

126. NATURAL RESISTANCE PHENOTYPES
Group III : Serratia spp, Citrobacter freundii,
Enterobacter spp, Pantoea agglomerans
Morganella morganii, Hafnia alvei,
Proteus vulgaris, Providencia spp,
 Wild strain : cephalosporinase (Nat. Case)
low level enzyme production
Group IV : Yersinia spp
 Wild strain : Penicillinase and cephalosporinase
( Nat. Pase and Case)

127. RESISTANCE PHENOTYPES :
WILD STRAINS
AMO AMC TIC CFT
S S S S
 Group 1 :
 No natural resistance
Except low level case for
E. coli and shigella
AMO AMC TIC CFT
R S R S
 Group 2 :
 Natural Pase
AMO AMC TIC CFT
R R* S R
 Group 3 :
 Natural Case
(* :for most Group 3 bacteria)
AMO AMC TIC CFT
R R R R
 Group 4 :
 Case + pase

128. ENTEROBACTERIACEAE
AMO AMC MEC TIC CFT CXT TET COL FUR
Escherichia coli S S S S S S S S S
I Shigella/Salmonella S S S S S S S S S
Proteus mirabilis S S S S S S R R R
Klebsiella pneumoniae/
II oxytoca R S S R S S S S S
Citrobacter diversus
(Lev. amalonatica) R S S R S S S S S
Enterobacter cloacae/
aerogenes R R S S R R S S S
Citrobacter freundii R R S S R R S S S
Proteus vulgaris R S R S R S R R R
III Serratia marcescens R R R S R In R R R
Morganella morganii R R R S R In R R R
Hafnia alvei R R R S R S S S S
Providencia rettgeri R R R S R S R R R
Providencia stuartii R R R S R S R R R
IV Yersinia enterocolitica R R S R R r S S S
Natural resistance
r = low level resistance, in = Inducible

129. WILD STRAINS
 Group 1 :
 Group 2 :
Natural Pase
 Group 3 :
Natural Case
 Group 4 :
Case + pase
Low case for E. coli, Shigella

130. Wild strains and acquired resistances
 Group 1 :
 Group 2 :
 Group 3 :
 Group 4 :
IRT
ESBL
ESBL
ESBL
Acquired PASE
Acquired Pase
Natural Pase
Natural Case
Acquired Pase
Natural
Case + Pase
HL case
(E. coli,
Shigella)
HL case
ESBL

131. GROUP 1: P.mirabilis / Salmonella
Observed phenotypes
AMO AMC TIC PIC IMI 1GC 3GC
Wild S S S S S S S
Acquired Pase I-R S-I-R I-R I-R S S-I S
ESBL R S-I I-R I-R S S-I-R S-I-R
Acquired resistance phenotypes : b lactams

132. GROUP 1: E.coli / Shigella
Observed phenotypes
Acquired resistance phenotypes : b lactams
AMO AMC TIC PIC TZP IMI 1GC CXT 3GC
Wild S S S S S S S S S
Low Case S-I S-I S S S S I-R S S
HL Case R R S S S S R R I
Acquired Pase I-R S-I I-R R S S S-I S S
Pase resistant
to inhibitors R R R R I-R S S-I S S
ESBL R S-I R R S S S-I-R S S-I-R
* Isolated R to Mecillinam possible for E. coli but impossible for the others
( inoculum too heavy)

133. GROUP 2 : Observed phenotypes
Acquired resistance phenotypes : b lactams
AMO AMC TIC PIC TZP 1GC 3GC
Wild (Natural Pase) I-R S R S-I-R S S S
Acquired Pase R S-I R I-R S I-S S
ESBL R S I-R S-I-R S I-R S-I-R
Hyper production of natural
Pase (for K. oxytoca) R I-R R I-R S-I I-R S

134. GROUP 3 : Observed phenotypes
Acquired resistance phenotypes : b lactams
AMO AMC TIC PIC TZP IMI 1GC 3GC
Wild: R (R) S S S S RS
(Nat Case)
Pase R (R) R R S-I S R S
HL Case R R I-R I-R I-R S R I-R
ESBL R R R R S-I-R S R S-I-R
( ) = possible S for Proteus vulgaris

135. b-Lactams and Enterobacteriaceae (SUMMARY)
Antibiotics PASE PASE IRT ESBL CASE CASE
NAT ACQUIRED NAT high level
Penicillins :
Amino P I/R R R R R R
Carboxi P I/R R R R S R
Ureido P S/I I-R R R S R
Cephalo :
C1G S S/I S/I/R R R R
C2G S S S/I/R R S/I/R R
C3G S S S S/I/R S R
Inhibitors: S S/I R S/I/R R R
Imipenem S S S S S S

136. Techniques for the detection of ESBL

137. WHAT ARE ESBL ?
 Extended Spectrum Beta-Lactamase
 mutation of a traditional Penicillinase
- plasmid-origin
- thus transferable
 Described for Enterobacteriaceae
80 % of cases concern Klebsiella pneumoniae
ALL BETA-LACTAMS ARE AFFECTED
except Cephamycins and Carbapenems

138. Techniques for the detection of ESBL
- CAZ at 1 mg/l on ATB G- 5
- Interpretative reading
- ATB BLSE
- Disk method (Champagne cork)
 DETECTION OF ESBL
 CONFIRMATION OF ESBL

139. Detection of ESBL using ATB G - 5
 Objective : Distinguish acquired Penicillinase
and ESBL when there is a doubt
Depends on the MIC to Ceftazidim
TEST CAZ 1 :

140. Detection of ESBL using ATB G - 5
Test CAZ 1 = Ceftazidim at 1 µg/ml enables the detection of
low level resistance of ESBL (Low MIC)
Breakpoints
N° of
strains
0.03 0.06 0.12 0.25 0.5 1 2 4 8 16 32 64 128
CAZ 1
1 µg/ml
R
S I
MIC to
Ceftazidim

141. DETECTION OF ESBL USING DIFFUSION:
«Champagne cork» or «key hole effect»
 Objective : Distinguish ESBL and HL Case
when there is a doubt
 Technique : Deposit 3 disks
(Distance to be adapted )
- Inhibitor of B-Lactamase
- 3rd gen. Cephalosporin
- Aztreonam
C3G
AZT
Inhibitor

142. DETECTION OF ESBL USING DIFFUSION:
Amoxicillin +
Clavulanic acid
Ceftazidime
Aztreonam
ESBL
HL CASE
«Champagne cork» or «key hole effect»
No action of inhibitor
Action of inhibitor

143. DETECTION OF ESBL USING DIFFUSION:
«Champagne cork» or «key hole effect»

144. Detection of ESBL using ATB BLSE
 Objective : Distinguish ESBL and HL Case
when there is a doubt
 Technique : Comparaison of
- MIC determination of 3rd gen. Cephalosporin
- MIC determination of 3rd gen. Cephalosporin +
Inhibitor of B-Lactamase
If at least 4 dilutions difference : ESBL +

145. Detection of ESBL using ATB BLSE
ref. 14 100 mg/l Example
1 ATM ATM+S Aztreonam Aztr.+Sulbactam 0.5 0.06 + +
2 ATM ATM+S Aztreonam Aztr.+Sulbactam 1 0.12 + + ESBL(+) : MIC range
3 ATM ATM+S Aztreonam Aztr.+Sulbactam 2 0.25 + + from 8 to 0.5 (4
4 ATM ATM+S Aztreonam Aztr.+Sulbactam 4 0.5 + - dilutions). Image + -
5 ATM ATM+S Aztreonam Aztr.+Sulbactam 8 1 - -
6 CAZ CAZ+S Ceftazidime Cefta+Sulbactam 0,5 0.06 + +
7 CAZ CAZ+S Ceftazidime Cefta+Sulbactam 1 0.12 + +
8 CAZ CAZ+S Ceftazidime Cefta+Sulbactam 2 0.25 + + ESBL(+) : MIC range
9 CAZ CAZ+S Ceftazidime Cefta+Sulbactam 4 0.5 + + from 32 to 1 (10
10 CAZ CAZ+S Ceftazidime Cefta+Sulbactam 8 1 + - dilutions).
11 CAZ CAZ+S Ceftazidime Cefta+Sulbactam 16 2 + - Image + -
12 CAZ CAZ+S Ceftazidime Cefta+Sulbactam 32 4 - -
13 CTT CTT Cefotetan 4 32 ESBL: S
14 IMI IMI Imipenem 4 8 ESBL: S
15 SCTX1 SCTX2 Cefotaxime + Sulbactam 0.06 0.12 Control of the recovery
activity

146. ENTEROBACTERIACEAE
GEN TOB NET AKN KAN
APH 3' S S S S R
AAC 3I R S S S S
AAC 3II R R R S R
AAC 6' S R R R R
AAC 2' R R R S S
ANT 2" R R S S S
Impossible S S S R S
Impossible S S R S S
Impossible S R S S S
NB : * AAC 6' : Often associated with an ESBL, except for S. marcescens
* P. stuartii has an AAC 2' in the wild state
Acquired resistance : Aminoglycosidases

147. 8.2 - Main resistance mechanisms
of Staphylococci

148. GRAM POSITIVE COCCI
 GRAM POSITIVE COCCI
 Natural resistance : Aztreonam
Nalidixic acid (QUINOLONES 1)
Polypeptides
 STAPHYLOCOCCI
 Natural susceptibility : Vancomycin
 At least one case of Staphylococcus aureus has been detected
VAN: I
Natural resistance and susceptibility

149. STAPHYLOCOCCI
 b lactams
PEN G OXA
S S Absence of pase
Check with chromogenic test
R S Acquired Pase
R R Modification of PBP
(MRSA)
Acquired resistance

150. PENICILLINASE TEST
 Cefinase 
For rapid detection of B-Lactamase production
 Chromogenic cephalosporin (= Nitrocefin)
Ref : 55 622
colony
(+)
5 mins to 1 hour
Also for H. influenzae, N. gonorrhoae, Enterococci, and anaerobes

151. Cefinase (+)  change Pen G : S to R
Cefinase (-)  do not change Pen G
PENICILLINASE TEST
 ATB Staph
 Cupule Pen G at 0.125 g/l
If Penicilline G is S, confirm by Cefinase  test

152. METICILLIN RESISTANCE :
OXACILLIN TEST
 NCCLS : broth or agar dilution
 Mueller Hinton+ 2% Nacl
 oxacillin 2 µg/ml
 24 h at 35°C
 MOLECULAR BIOLOGY
 "Mec A"gene detection
 Slidex MRSA detection
 PBP 2a detection
 ATB Staph
 Cupule Oxa ( 2 mg/l )
 ATB Na medium semi solid 5%Nacl
 18- 24 H at 37°C
Reference Method

153. 8.3 - Main resistance mechanisms
of Streptococci

154. STREPTOCOCCI
 Natural resistance to Aminoglycosides
 Usual susceptibility of Streptococcus pyogenes to PEN G
 Enterococcus faecalis - faecium :
Natural resistance to Cephalosporins (1st, 2nd, 3rd
Gen.), Penicillin M (OXA) and Lincosamides
E. faecium frequently Ampicillin : I or R
Natural resistance and susceptibility

155. PNEUMOCOCCI
 ATB STREP 5
PEP OXA
(0.06-1)
S S Wild
I - R I - R Decreased susceptibility to PEN G
by PBP mutation
Test MIC before treatment !
Acquired resistance
PEP = detection test of the susceptibility of
Pneumococci to Penicillin

156. STREPTOCOCCI
 Aminoglycosides : NATURAL RESISTANCE
Detection of resistance ruling out the association with
betalactams.
KANHC GENHC
R R No synergy blactams + Gentamycin
and Kanamycin
I I Synergy blactams + Gentamycin
and Kanamycin
I R Synergy blactams + Kanamycin
No synergy blactams + Gentamycin
Acquired resistance

157. 9 - Choice of antibiotic panel
compositions

158. HOW TO CHOOSE THE ANTIBIOTIC
PANEL ?
 Drugs with therapeutic interest
 Markers enabling an equivalence with other drugs
 Molecules tested for detection of natural and acquired
resistances

159.  Notion of markers
The molecule chosen in an antibiotic group must be the most
regularly affected by the resistance mechanism
 Notion of equivalence
Also enables results to be extended to other molecules.
Eg: cephalotin enables a result to be given for all first
generation cephalosporins.
HOW TO CHOOSE THE ANTIBIOTIC
PANEL ?

160. 10 - Interest of the Expert
system

161. A CONTINUOUS QUALITY CONTROL
The Expert checks that
each observed result is possible
=
interpretative reading

162. EXPERT
 INTERPRETATIVE READING
 avoids therapeutic failure
 Rapid evolution of acquired resistance
mechanisms
 Weak expression of resistance «in VITRO»

163. EXPERT
Interpretative reading permits:
 To find out resistance mechanisms
 To deduce non tested drugs
 To realise epidemiological study

164. HOW THE EXPERT WORKS
 Needs ID
 Checks natural resistances
 Observes if acquired resistances
 Deduces mecanisms of resistance
 Sometimes
– correct : S  R, or I  R
– comment

165. HOW THE EXPERT WORKS
Raw results
IN VITRO IN VIVO
Interpreted
results for :
EXPERT

166. THEN
Incoherence
Phenotype
Identification
etc.
Ampicillin
Ticarcillin
Imipenem
R
R
R
If AMP = R
If TIC = R
If IMI = R
and
ID ....
= Fact base = Knowledge base
RAW RESULTS RULES Comments
HOW THE EXPERT WORKS

167. If
Klebsiella pneumoniae
R
R
THEN
S
Natural resistance
of K. pneumoniae
(Penicillinase)
S
S
AMOXICILLIN
TICARCILLIN
IMIPENEM
AMOX. CLAVU
CEFOTAXIM
Test CAZ 1 S
EXAMPLE

168. If
R
R
THEN
S
ESBL
I
I
R
EXAMPLE
Klebsiella pneumoniae
AMOXICILLIN
TICARCILLIN
IMIPENEM
AMOX. CLAVU
CEFOTAXIM
Test CAZ 1

169. If
R
R
THEN
R
Impossible
phenotype
S
S
R
EXAMPLE
Klebsiella pneumoniae
AMOXICILLIN
TICARCILLIN
IMIPENEM
AMOX. CLAVU
CEFOTAXIM
Test CAZ 1

170. DEDUCE DRUGS
 Testing MARKERS is essential
 to deduce non tested drugs
 So, the choice of drugs to be tested must
respond to rules and not (only) to the request
of physician

171. EPIDEMIOLOGICAL INTEREST
 Follow up evolution of resistance
 Epidemiological surveillance tools for local resistances
statistical analysis of resistance per species, type of specimen
 in order to adapt the initial choice of antibiotic
therapy
 Intra-hospital epidemics caused by multiresistant bacteria
 justify an appropriate infection control measures

172.  Non transferable mechanisms
 stable, chromosomic
 Transferable mechanisms
– Transmission of the resistance (plasmid)
– loose of the resistance possible
EPIDEMIOLOGICAL INTEREST
Not transferable
transferable

173. EPIDEMIOLOGY
ISOLATION OF PATIENT
NO ISOLATION OF PATIENT
Appropriate hygiene mesures
+
OR
Transferable
resistance
Ex : BLSE
Multiresistant
bacteria
Ex : MRSA
Not transferable
resistance
Ex : Natural case

174. THE EXPERT
Check
Validate
Correct
Expert analysis

175. THE EXPERT SYSTEMS
 Deduce resistance mechanisms
 Deduce results for antibiotics not tested
(equivalence)
 Make therapeutic corrections
 Base for Epidemiological studies

176. 11 - Study of phenotypes

177. Amoxicillin R
Amo / Clav Ac. S
Ticarcillin S
Ticar+ clav Ac. S
Piperacillin S
Pip / Tazobactam S
Imipenem S
Cefalotin S
Cefoxitin R
Cefotaxime R
Ceftazidime R
Ceftazidime - 1 R
Cefepime S
Cefpirome S
Tobramycin S
Gentamicin S
Amikacin S
Netilmicin S
Nalidixic Ac. S
Pefloxacin S
Ciprofloxacin S
Cotrimoxazole S
raw value raw value
1 - Enterobacter cloacae

178. Amoxicillin R
Amo / Clav Ac. S
Ticarcillin R
Ticar + clav. Ac S
Piperacillin S
Pip / Tazobactam S
Imipenem S
Cefalotin S
Cefoxitin S
Cefotaxime S
Ceftazidime S
Ceftazidime - 1 S
Cefepime S
Cefpirome S
Tobramycin S
Gentamicin S
Amikacin S
Netilmicin S
Nalidixic Ac. R
Pefloxacin S
Ciprofloxacin S
Cotrimoxazole S
raw value raw value
2 - Escherichia coli

179. Amoxicillin R
Amo / Clav Ac. R
Ticarcillin S
Ticar +clav Ac S
Piperacillin S
Pip / Tazobactam S
Imipenem S
Cefalotin R
Cefoxitin S
C efotaxime S
Ceftazidime S
Ceftazidime - 1 S
Cefepime S
Cefpirome S
Tobramycin S
Gentamicin S
Amikacin S
Netilmicin S
Nalidixic Ac. S
Pefloxacin S
Ciprofloxacin S
Cotrimoxazole S
raw value
raw value
3 - Pantoea agglomerans

180. Amoxicillin R
Amo / Clav Ac. S
Ticarcillin S
Ticar +clav Ac S
Piperacillin S
Pip / Tazobactam S
Imipenem S
Cefalotin I
Cefoxitin S
C efotaxime S
Ceftazidime S
Ceftazidime - 1 S
Cefepime S
Cefpirome S
Tobramycin S
Gentamicin S
Amikacin S
Netilmicin S
Nalidixic Ac. S
Pefloxacin S
Ciprofloxacin S
Cotrimoxazole S
raw value
raw value
4 - Proteus vulgaris

181. Amoxicillin R
Amo / Clav Ac. S
Ticarcillin S
Ticar +clav Ac S
Piperacillin S
Pip / Tazobactam S
Imipenem S
Cefalotin S
Cefoxitin S
C efotaxime S
Ceftazidime S
Ceftazidime - 1 S
Cefepime S
Cefpirome S
Tobramycin S
Gentamicin S
Amikacin S
Netilmicin S
Nalidixic Ac. S
Pefloxacin S
Ciprofloxacin S
Cotrimoxazole S
raw value
raw value
5 - Yersinia enterocolitica

182. Amoxicillin R
Amo / Clav Ac. R
Ticarcillin R
Ticar +clav Ac R
Piperacillin R
Pip / Tazobactam S
Imipenem S
Cefalotin I
Cefoxitin S
C efotaxime S
Ceftazidime S
Ceftazidime - 1 S
Cefepime S
Cefpirome S
Tobramycin S
Gentamicin R
Amikacin S
Netilmicin S
Nalidixic Ac. S
Pefloxacin S
Ciprofloxacin S
Cotrimoxazole R
raw value
raw value
6 - Klebsiella pneumoniae

183. Amoxicillin R
Amo / Clav Ac. R
Ticarcillin R
Ticar +clav Ac R
Piperacillin R
Pip / Tazobactam I
Imipenem S
Cefalotin R
Cefoxitin R
C efotaxime R
Ceftazidime R
Ceftazidime - 1 R
Cefepime S
Cefpirome S
Tobramycin S
Gentamicin S
Amikacin S
Netilmicin S
Nalidixic Ac. S
Pefloxacin S
Ciprofloxacin S
Cotrimoxazole R
raw value
raw value
7 - Enterobacter cloacae

184. Amoxicillin R
Amo / Clav Ac. R
Ticarcillin S
Ticar+ clav Ac. S
Piperacillin S
Pip / Tazobactam S
Imipenem S
Cefalotin R
Cefoxitin S
Cefotaxime S
Ceftazidime S
Ceftazidime - 1 S
Cefepime S
Cefpirome S
Tobramycin S
Gentamicin R
Amikacin S
Netilmicin S
Nalidixic Ac. R
Pefloxacin I
Ciprofloxacin S
Cotrimoxazole S
raw value raw value
8 - Morganella morganii

185. Amoxicillin R
Amo / Clav Ac. R
Ticarcillin R
Ticar+ clav Ac. S
Piperacillin S
Pip / Tazobactam S
Imipenem S
Cefalotin R
Cefoxitin R
Cefotaxime I
Ceftazidime I
Ceftazidime - 1 R
Cefepime S
Cefpirome S
Tobramycin S
Gentamicin S
Amikacin S
Netilmicin S
Nalidixic Ac. S
Pefloxacin S
Ciprofloxacin S
Cotrimoxazole S
raw value raw value
9 - Serratia marcescens

186. Amoxicillin S
Amo / Clav Ac. S
Ticarcillin S
Ticar+ clav Ac. S
Piperacillin S
Pip / Tazobactam S
Imipenem S
Cefalotin I
Cefoxitin S
Cefotaxime S
Ceftazidime S
Ceftazidime - 1 S
Cefepime S
Cefpirome S
Tobramycin S
Gentamicin S
Amikacin S
Netilmicin S
Nalidixic Ac. S
Pefloxacin S
Ciprofloxacin S
Cotrimoxazole S
raw value raw value
10 - E.coli

187. Amoxicillin R
Amo / Clav Ac. I
Ticarcillin R
Ticar +clav Ac S
Piperacillin S
Pip / Tazobactam S
Imipenem S
Cefalotin R
Cefoxitin S
C efotaxime S
Ceftazidime S
Ceftazidime - 1 R
Cefepime S
Cefpirome S
Tobramycin R
Gentamicin S
Amikacin R
Netilmicin S
Nalidixic Ac. R
Pefloxacin S
Ciprofloxacin S
Cotrimoxazole R
raw value
raw value
11- Proteus mirabilis

188. Penicillin G S
Oxacillin S
AMPI/Sulbact S
Cefalotin S
Gentamicin S
Netilmicin S
Erythromycin S
Clindamycin S
Nitrofurantoïn S
Pefloxacin / Q2G S
Ciprofloxacin S
Rifampicin S
Vancomycin S
Teicoplanin S
Cotrimoxazole S
Tetracyclin S
raw value raw value
12 - Staphylococcus aureus

189. Penicillin G R
Oxacillin S
AMPI/Sulbact S
Cefalotin S
Gentamicin S
Netilmicin S
Erythromycin S
Clindamycin S
Nitrofurantoïn S
Pefloxacin / Q2G S
Ciprofloxacin S
Rifampicin S
Vancomycin S
Teicoplanin S
Cotrimoxazole S
Tetracyclin S
raw value raw value
13 - Staphylococcus aureus

190. Penicillin G R
Oxacillin R
AMPI/Sulbact S
Cefalotin S
Gentamicin R
Netilmicin S
Erythromycin R
Clindamycin S
Nitrofurantoïn S
Pefloxacin / Q2G R
Ciprofloxacin S
Rifampicin S
Vancomycin S
Teicoplanin S
Cotrimoxazole S
Tetracyclin S
raw value raw value
14 - Staphylococcus epidermidis

191. Penicillin G R
Oxacillin S
AMPI/Sulbact S
Cefalotin S
Gentamicin S
Netilmicin S
Erythromycin S
Clindamycin S
Nitrofurantoïn S
Pefloxacin / Q2G S
Fosfomycine S
Rifampicin S
Vancomycin S
Teicoplanin S
Cotrimoxazole S
Tetracyclin S
raw value raw value
15- Staphylococcus saprophyticus

192. Penicillin Pneumo R
Penicillin Strepto R
Ampicillin Strepto S
Penicillin entero R
Ampicillin entero S
Cefalotin S
Cefuroxime R
Piperacillin S
Oxacillin R
Ciprofloxacin S
Tetracyclin R
Erythromycin R
Clindamycin R
Cotrimoxazol S
Nitrofurantoïn S
Rifampicin S
Vancomycin S
Teicoplanin S
Kanamycin HC R
Gentamicin HC I
raw value raw value
16 - Enterococcus faecalis

193. Penicillin Pneumo S
Penicillin Strepto S
Ampicillin Strepto S
Penicillin entero S
Ampicillin entero S
Cefalotin S
Cefuroxime S
Piperacillin S
Oxacillin S
Ciprofloxacin S
Tetracyclin S
Erythromycin S
Clindamycin S
Cotrimoxazol S
Nitrofurantoïn S
Rifampicin S
Vancomycin S
Teicoplanin S
Kanamycin HC I
Gentamicin HC I
raw value raw value
17 - Streptococcus agalactiae

194. Penicillin Pneumo R
Penicillin Strepto R
Ampicillin Strepto R
Penicillin entero R
Ampicillin entero I
Cefalotin R
Cefuroxime R
Piperacillin S
Oxacillin R
Ciprofloxacin S
Tetracyclin R
Erythromycin R
Clindamycin R
Cotrimoxazol S
Nitrofurantoïn S
Rifampicin S
Vancomycin S
Teicoplanin S
Kanamycin HC R
Gentamicin HC I
raw value raw value
18 - Enterococcus faecium

195. Penicillin Pneumo S
Penicillin Strepto S
Ampicillin Strepto S
Penicillin entero S
Ampicillin entero S
Cefalotin S
Cefuroxime S
Piperacillin S
Oxacillin S
Ciprofloxacin S
Tetracyclin S
Erythromycin S
Clindamycin S
Cotrimoxazol S
Nitrofurantoïn S
Rifampicin S
Vancomycin S
Teicoplanin S
Kanamycin HC I
Gentamicin HC I
raw value raw value
19 - Streptococcus pyogenes

196. Penicillin Pneumo R
Penicillin Strepto S
Ampicillin Strepto S
Penicillin entero S
Ampicillin entero S
Cefalotin S
Cefuroxime S
Piperacillin S
Oxacillin R
Ciprofloxacin S
Tetracyclin S
Erythromycin R
Clindamycin S
Cotrimoxazol R
Nitrofurantoïn S
Rifampicin S
Vancomycin S
Teicoplanin S
Kanamycin HC I
Gentamicin HC I
raw value raw value
20 - Streptococcus pneumoniae