Marys Medicine


Clostridium difficile diagnostik

How to treat

Reno Frei, M.D.
Klinische Mikrobiologie
Universitätsspital Basel
4031 Basel
[email protected]
Restricted Use in Children -1
Fluoroquinolones (Cipro-, Levo-, Moxifloxacin)
Not approved for children age <18 years
based on joint cartilage injury in immature animals
Ciprofloxacin in special indications:
- P. aeruginosa in CF (each age)
- complicated UTI as drug of 3rd choice age >1 year

Tetracycline, Doxycycline, Minocycline
Only for children age >8 years
Contraindicated in infants age <3 months*
Daptomycin (Cubicin™)
Safety & efficacy in children <18 years not established
* risk of hemolytic anemia due to immaturity of enzyme activity Restricted Use in Children -2
Tigecycline (Tygacil™)
Not approved in children <18 years
FDA warning: increased mortality in adult patients
Ceftaroline Fosamil (Zinforo™)
Safety and efficacy not established in children
Not yet marketed in Switzerland
Quinupristin-Dalfopristin (Synercid™)
Not registered in Switzerland
No data for pediatric use
Phenotypic susceptibility testing is
based on the minimum inhibitory
concentration (MIC)

The MIC is the reference for all other
phenotypic tests
The MIC breakpoint is valid only in a
standardised method
G. Kahlmeter, ECCMID 2010

Routine Susceptibility Testing
in the Clinical Laboratory
MIC measurements
• (Macrobroth dilution: reference) • Microbroth dilution: reference • Automated systems (Vitek®, Phoenix® etc.) • Gradient diffusion methods: Etest®  Disk diffusion test (Kirby-Bauer)

Interpretive Standards
1975: Proposal for disk test
1980: Proposal for MIC test
2013: CLSI: 23rd update

1997: founded
2010-2011: Clinical Breakpoint

Tables for MIC and disk test
2013: version 3.0
*European Committee on Antimicrobial Susceptibility Testing 6
Breakpoints mainly based on MIC distributions,
PK-PD properties and clinical data
Mouton JW. Clin Microbiol Infect. 2012,18:E37-45
Documents available for free
Clinical Breakpoints
Expert rules:
- intrinsic resistances - exceptional resistance phenotypes - interpretive rules Approach to MDR
Question: intrinsic or acquired/mutational resistance
or exceptional / unusual phenotype?
See Leclercq et al. Clin Microbiol Infect 2013,19:141–160
(EUCAST expert rules)
E.g. intrinsic resistance in non-fermentative Gram-negative bacteria

Intrinsic (inherent) Resistance
Drug is clinically useless
Antimicrobial susceptibility testing (AST) unnecessary
«susceptible» results: error in identification or AST,
even if confirmed: avoid the drug or use with caution

also intrinsically resistant to Benzylpenicillin,
glycopeptides, Fusidic acid, macrolides (with some
exceptions), Clindamycin, Rifampicin, Daptomycin,
and Linezolid

Non-fermentative Gram-negative bacteria
additionally R to Cefuroxime and Cefamandole
Multidrug-Resistant Pathogens (MDR)
E Enterococcus faecium
S Staphylococcus aureus
K Klebsiella pneumoniae
ESBL, KPC & others
A Acinetobacter baumannii Carbapenem-resistant
P Pseudomonas aeruginosa MDR
E Enterobacter Species

J Infect Dis 2009,48:1-12
General Rules
Treatment of MDR microorganisms should be based
on in-vitro susceptibility testing results,
ideally on MICs (quantitative results)

Testing of combinations of antimicrobial agents is
not feasible in the routine lab and still experimentally
in the research lab

Combinations theoretically beneficial to prevent
further development of resistance
Use only regimens (including combinations) that are
clinically proven (no «fantasy regimens»)
Do not force the laboratory to test drugs lacking
established breakpoints for a certain microorganism
Enterococcus spp.
E. faecalis: nearly all S to Amoxicillin, Imipenem
E. faecium: mostly MDR → R to Amoxi →
R to all beta-lactam agents → Vancomycin
Vancomyin-resistant enterococci = VRE*
Acquired: VanA, VanB; intrinsic: VanC  Alternatives
Linezolid*, Teicoplanin,
Nitrofurantoin (uncomplicated UTI and E. faecalis)
TMP-SMX (in contrast to USA/CLSI)
 (Daptomycin*, Quinupristin/Dalfopristin, Tigecycline)
* Review: Whang DW. AAC 2013,57:5013-8
Enterococcus faecium
Today E. faecium often MDR
Primary: Vancomycin
For UTI: Nitrofurantoin, TMP-SMX*
For bactericidal action of Amoxicillin or Vancomycin
aminoglycoside is needed (e.g. in endocarditis) →
combination with Gentamicin or Streptomycin

Vancomycin-resistant enterococci (VRE):
Linezolid, (Tigecycline), possibly Teicoplanin (if S)

* Trimethoprim-Sulfamethoxazole, Cotrimoxazole Enterococcus spp. Combination with Aminoglycoside
Penicillins and glycopeptides show bacteriostatic
rather than bactericidal activity
Enterococci are intrinsically resistant to aminoglyco-
sides and aminoglycoside monotherapy is ineffective
There is likely to be synergy between aminoglyco-
sides and penicillins or glycopeptides against E.
without acquired high-level resistance (HLR)

Test for Gentamicin HLR (MIC >128 mg/L):
If negative → assume synergy / bactericidal activity
If positive: avoid Gentamicin and other aminoglycos.
→ test for Streptomycin HLR (MIC >512 mg/L)
Methicillin-/Oxacillin-resistant S. aureus
crossresistant to all beta-lactam agents (except Ceftaroline)
IDSA guidelines for adults and children:
Clin Infect Dis 2011,52:e18-55  Primary: Vancomycin (esp. for severe infections)
Alternatives if strain is susceptible:
Linezolid (esp. for pneumonia)
TMP-SMX, Clindamycin, Minocycline, Doxicycline
Only in combination: Rifampicin, Fusidic acid
 (Teicoplanin, Daptomycin, Ceftaroline)
S. aureus / MRSA
If resistant to macrolides MLSB* induction test
If positive resistant mutants can be selected by
clindamycin clinical failure may occur
If negative clindamycin may be used
D-Zone Test
* macrolides, lincosamides and streptogramins B
Clin Infect Dis 2005, 40:280-5
S. aureus, MRSA VISA, VRSA
Vancomycin S: MIC ≤2 mg/l
Vancomycin-intermediate VISA: 4-8 mg/L: very rare
Vanco-resistant VRSA: >8 mg/L: <20 strains reported
High failure rates with vancomycin in MRSA found
particulary in isolates with MIC 2.0 mg/l (>1 mg/L)
in bacteremia (BSI)
van Hal SJ. CID 2012, 54:755-71
Reasons unclear
Holmes NE. J Infect Dis 2011, 204:340-7  Best treatment unknown
Target trough levels of 15-20 mg/L recommended
Severe Infections due to K. pneumoniae ESBL Failure of Cephalosporin Treatment
% failure
MIC (mg/l)
J Clin Microbiol 39:2206, 2001 Susceptibility Testing Paradigm Change
After lowering the breakpoints 2011
Both EUCAST and CLSI: Report as tested irrespective
of resistance mechanisms Treat as reported
However, doubts on the efficacy of e.g.
- cephaloporins or Amoxi/clav. against ESBL
- carbapenems against carbapenemase-producers

Controversial issue
Livermore DM et al. JAC 2012, 67:1569-77 Are susceptibility tests enough, or should laboratories still seek ESBLs and carbapenemases directly?  In Switzerland: Labs continue to identify important
resistance mechanisms at least in the next 2 years
AmpC β-Lactamase
In Enterobacter spp., Citrobacter freundii,
Serratia spp. and Morganella morganii (and others):
If susceptible in vitro to Ceftriaxone or Ceftazidime
do not use these drugs in monotherapy
Selection of AmpC-derepressed cephalosporin-
resistant mutants may occur during therapy
Combination with an aminoglycoside may also lead
to failure (in contrast to quinolones)
Selection risk absent or much diminished for cefepime
Tamma PD et al. Clin Infect Dis 2013, 57:781-8  Piperacillin-Tazobactam: conflicting data
Chow JW et al. Ann Intern Med 1991,115: 585–90 20 Leclercq R et al. Clin Microbiol Infect 2013,19:141–160  Primary: Meropenem, Imipenem, Ertapenem
For uncomplicated UTI: Fosfomycin oral,
Nitrofurantoin (E. coli)
If susceptible: TMP-SMX, quinolones
Often categorized as susceptible to combinations
of a penicillin and a β-lactamase inhibitor
If susceptible to Amoxycillin–clavulanate or
Piperacillin–tazobactam or 3rd/4th generation
cephalosporin → uncertain therapeutic outcome

for infections other than UTIs

Pseudomonas aeruginosa
Primary: Ceftazidime, Pip-Tazo, Cefepime,
Meropenem, Tobramycin° (in combination)
Alternative: Imipenem, Aztreonam°, Ciprofloxacin,
(Levofloxacin), in combination Gentamicin or

For MDR: Colistin° + carbapenem or Rifampicin
Combination therapy: frequently recommended for
empiric therapy in severe infections esp. for MDR
For directed therapy: conflicting study results →
still unsettled and controversial *

° = also nebulized for inhalation * Review: Tamma PD. Clin Microbiol Rev 2012, 25:450-70
Stenotrophomonas maltophilia
EUCAST: «For Stenotrophomonas maltophilia the
only drug with clinical correlation between MICs and
clinical outcome is Trimethoprim-Sulfamethoxazole"

TMP-SMX: therapy of choice
"It may be that in the future one or two more drugs
may receive breakpoints, but current literature does
not clearly indicate another drug for which it is
reasonable to determine breakpoints."

CLSI: breakpoints also for Ceftazidime, Levofloxacin,
Minocycline, (Chloramphenicol, Ticarcillin-clav. acid)
Acinetobacter baumannii
In many countries MDR strains
including carbapenem-R, possibly panresistant
EUCAST: no breakpoints for penicillins and
cephalosporins defined
Primary: Meropenem, Imipenem (± Ciprofloxacin)
For MDR: Colistin combine with a carbapenem
even if the isolate is resistant in vitro1
If susceptible: Cefepime (tested according to CLSI),
Ciprofloxacin, Levofloxacin, Minocycline,
(TMP-SMX), and aminoglycosides in combination

General review: Fishbain J. CID 2010,51:79-84 24
1) Zusman O. AAC 2013, 57:5104-11
For MDR gram-positive bacteria:
For MDR gram-negative bacteria:
Meropenem, Ertapenem or Imipenem
For extensively MDR gram-negative bacteria:
possibly combined with a carbapenem

In severe infections, consider to use
cominations for empiric therapy, e.g.
• Vancomycin + Flucloxacillin in S. aureus • Vancomycin + Ceftriaxone in meningitis * Kapoor K. Pediatr Crit Care Med 2013,14:e268-72


Taylor, MC; Kelly, JM (2006) pTcINDEX: a stable tetracycline-regulated expression vector for Trypanosoma cruzi. BMC Biotechnol,6. p. 32. ISSN 1472-6750 DOI: 10.1186/1472-6750-6-32 Downloaded from: Please refer to usage guidelines at or alterna-tively contact Available under license: Research articlepTcINDEX: a stable tetracycline-regulated expression vector for Trypanosoma cruziMartin C Taylor* and John M Kelly


Scandinavian Journal of Gastroenterology, 2009; 44: 11861190 Effect of fat emulsion (Fabuless) on orocecal transit timein healthy men ARVO HAENNI1, BIRGITTA SUNDBERG2, NAHID YAZDANPANAH3,ANNIKA VIBERG4 & JOHAN OLSSON2 1Department of Public Health and Caring Sciences, Clinical Nutrition and Metabolism, Uppsala University, Sweden, 2KPLGood Food Practice AB, Uppsala, Sweden, 3DSM Food Specialties, Delft, The Netherlands, and 4DSM, Food Specialties,Stockholm, Sweden