Identification, Susceptibility

1
Identification, Susceptibility Resistance
Dr Caroline B. Moore Mycology Reference
Centre University Hospital of South
Manchester The University of Manchester
2
Yeasts
3
Why bother with identification susceptibility
testing?

• Significant number of invasive fungal infections
• Increase in at-risk patient population

4
Why bother with identification susceptibility
testing?

• Significant number of invasive fungal infections
• Increase in at-risk patient population
• Increase in non-C. albicans species
• Increase in rarer species

5
Proportion of nosocomial Candida infections
caused by different species in a teaching hospital
Berrouane et al. J Clin Micro 1999 37531
6
Why bother with identification susceptibility
testing?

• Significant number of invasive fungal infections
• Increase in at-risk patient population
• Increase in non-C. albicans species
• Increase in rarer species
• Increase in drug resistance

7
Increasing fluconazole resistance in Intensive
Care Unit
Moore et al. ECMM 1998
8
Why bother with identification susceptibility
testing?

• Significant number of invasive fungal infections
• Increase in at-risk patient population
• Increase in non-C. albicans species
• Increase in rarer species
• Increase in drug resistance
• More drug choices available
• Informed therapeutic choice

9
How do we identify yeasts?

• Culture morphology

Chromagar
10
How do we identify yeasts?

• Germ tube test

• Microscopic morphology

Terminal chlamydospores
Arthrospores

• Other tests

11
How do we identify yeasts?

• Traditional methods
• Wickerham tests

Auxacolor

• Commercial kits
• numerous!

Vitek-2
API ID 32C

• Molecular methods

12
MICs
He uses statistics like a drunken man uses
lamp-posts ...
For support rather than illumination
13
Do we have a good test of susceptibility for
yeasts?

• CLSI (NCCLS) M27-A3 method
• USA standard
• EUCAST Document E-Def 7.1 method
• European standard

Extensive clinical correlation work
14
Do we have a good test of susceptibility for
yeasts?

• Disc diffusion
• no MIC obtained
• screening method

• E-test strips
• MIC value obtained
• problematic endpoints

15
Do we have a good test of susceptibility for
yeasts?

• An array of commercial formats
• Vitek-2
• YeastOne
• Fungitest
• Others

Some are more equal than others!

• Molecular methods

16
Candida albicans

• Most common cause of candidosis (50-70)
• Can cause a wide range of diseases
• May cause vaginal and oral/oesophageal thrush
• Produces germ tubes
• Attributable mortality (18-25)
• differences in patient age and underlying illness

17
Candida albicans

• Azole susceptibility can depend on HIV status

FLU ITR VOR POS AMB 5FC CASP
C.albicans

C.albicans - FLU-resistant
-

Rates of resistance seen in our laboratory
1992-2006 flucytosine 6 fluconazole 1.2
5 of C. albicans with reduced susceptibility
18
Candida parapsilosis complex

• Candida parapsilosis, Candida orthopsilosis,
  Candida metapsilosis
• 2nd most common species in blood, related to
  catheters and glucose solutions including TPN
• Often seen in neonates
• Generally do not cause thrush
• Less pathogenic than C. albicans

19
Candida parapsilosis complex
FLU ITR VOR POS AMB 5FC CASP
C.parapsilosis
-
Rates of resistance seen in our laboratory
1992-2006 fluconazole 0.4
20
Candida glabrata

• 3rd or 4th most common species in blood
• Increasing in many institutions
• Common cause of thrush, particularly vaginal
• Generally thought as unable to produce
  pseudohyphae in vitro
• Evidence of ability to grow as filamentous
  organism

21
Candida glabrata

• Usually reduced susceptibility to fluconazole
• Responds poorly to amphotericin B

FLU ITR VOR POS AMB 5FC CASP
C.glabrata

Rates of resistance seen in our laboratory
1992-2006 fluconazole 53
22
Candida tropicalis

• Usually 4th most common species in blood, much
  commoner in some institutions
• Generally does not cause thrush
• More invasive than other Candida species
• High attributable mortality (33-50)
• High frequency (80-100) of infection if
  coloniser during neutropenia

23
Candida tropicalis

• Usually fluconazole susceptible, but may develop
  resistance quickly

FLU ITR VOR POS AMB 5FC CASP
C.tropicalis

Rates of resistance seen in our laboratory
1992-2006 flucytosine 20 fluconazole 46
24
Candida krusei

• 5th most common species in blood
• Does not cause thrush, except in late-stage AIDS
• High mortality in leukaemic patients

25
Candida krusei

• May be a breakthrough species
• Always fluconazole resistant and amphotericin
  intermediate

FLU ITR VOR POS AMB 5FC CASP
C.krusei -
26
Cryptococcus neoformans

• Neurotropic fungus
• Most common predisposing factor is AIDS
• Also organ transplant recipients or cancer
  patients receiving chemotherapeutics
• Produces a polysaccharide capsule - major
  virulence factor

27
Cryptococcus neoformans

• Combination therapy generally used

FLU ITR VOR POS AMB 5FC CASP
Crypto. neoformans
-
28
Rhodotorula mucilaginosa
Image Courtesy of Carsten Kettner
Saccharomyces species
Malassezia species
High degree of mortality
29
Species of.TrichosporonGeotrichumBlastoschizo
myces
Can be intrinsically resistant to some antifungal
drugs
30
Moulds - the Aspergilli
31
Increasing incidence of invasive aspergillosis in
hematopoietic stem cell transplant recipients
Marr et al. Clin Infect Dis 2002 34909
32
What tests do we have to identify moulds?

• morphology
• microscopy
• additional tests
• molecular methods

Experience!
33
Aspergillus

• Wide spectrum of disease dependent on immune
  status

• Allergic bronchopulmonary aspergillosis
• Pulmonary aspergilloma
• Invasive aspergillosis

Can be a secondary pathogen in cases of carcinoma
or TB
34
Aspergillus fumigatus complex
most common cause of aspergillosis90 of cases
35
Aspergillus niger complex
Common cause of ear infections
36
Aspergillus terreus complex
Cause of superficial, eye, ear and systemic
infections
37
Aspergillus flavus complex
Cause of pulmonary and sinus infections
38
In vitro susceptibility of filamentous fungi
ITR VOR POS AMB 5FC CASP FLU
Asp. fumigatus /- -
Asp. niger - -
Asp. terreus - - -
Asp. flavus - -
39
Azole resistance in A. fumigatus complex

• Itraconazole
• recent literature 0 - 5
• 7 RMLM 1992 2007 (n 519)
• significant increase in resistance since 2004
  now 13
• Itraconazole resistant isolates
• 58 cross-resistant to voriconazole
• 66 cross-resistant to posaconazole

Data from Dr Susan Howard
40
Azole cross resistance of Asp. fumigatus complex
MIC mg/L
Mosquera Denning. Antimicrob Agents Chemother
2002 46556
41
Other Aspergilli
Klich MA. Identification of common Aspergillus
species (2002). CBS.
42
Non-Aspergillus moulds
43
Increasing frequency of non-Aspergillus mould
infections in hematopoietic stem cell transplant
recipients
Marr et al. Clin Infect Dis 2002 34909
44
Fusarium spp.
Range of disease from cutaneous through to
disseminated infection
45
Scedosporium spp.
Can cause subcutaneous infections but
dissemination may occur in immunocompromised host
46
Mucorales
Cunninghamella Rhizomucor Rhizopus Absidia
Mucor etc
47
In vitro susceptibility of filamentous fungi
ITR VOR POS AMB 5FC CASP FLU
Asp. fumigatus /- -
Asp. niger - -
Asp. terreus - - -
Asp. flavus - -
Fusarium - /- /- - - -
Scedosporium /- /- - - /- -
Mucorales - - - - -
48
Others
Acremonium
Penicillium
Plus many more
49
Take time to know the fungus in your hospital.
Better the devil.