Microbial Secondary Metabolites Production and Strain Improvement
MOSullivan Microbial Strain Typing - Ministry of Health
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Microbial strain typing in surveillance and outbreak investigation Matthew O'Sullivan Staff Specialist in Infectious Diseases and Clinical Microbiology Senior Lecturer, Sydney Medical School SYDNEY MEDICAL SCHOOL CENTRE FOR INFECTIOUS DISEASES & MICROBIOLOGY, WESTMEAD HOSPITAL,
Transcript of MOSullivan Microbial Strain Typing - Ministry of Health
Microbial strain typing in surveillance and outbreak investigationMatthew O'Sullivan
Staff Specialist in Infectious Diseases and Clinical Microbiology
Senior Lecturer, Sydney Medical School
SYDNEY MEDICAL SCHOOL
CENTRE FOR INFECTIOUS DISEASES & MICROBIOLOGY, WESTMEAD HOSPITAL,
Overview
› What is strain typing?
› Why do strain typing?
› Strain Typing in Infection Control
› Strain Typing Methods
› Typing Method Characteristics
› Strain Typing Interpretation
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What is strain typing?
Taxonomic Classifications
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What is strain typing?
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What is strain typing?
› Phenotype
Much variation is evident even within species
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What is strain typing?
› Phenotype
Much variation is evident even within species
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What is strain typing?
› Genotype
Much variation is evident even within species
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What is strain typing?
› Dividing organisms into groups below species level
- Using phenotypic or genotypic methods
What is strain typing?
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Why Do Strain Typing?
1. Study the evolution and population genetics
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Why Do Strain Typing?
1. Study the evolution and population genetics
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Why Do Strain Typing?
› Eg: Clostridium difficile ribotype 027
2. Detect strains of increased virulence
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EID 2012 17(6):976
Why Do Strain Typing?
3.Identify source of infection
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Strain typing in infection control
› Incidence of organism
- A patient develops MRSA bacteraemia in the ICU 5 days after admission to
hospital after one negative MRSA screen. The prevalence of MRSA colonisation
in ICU patients is 25%
- A patient develops bacteraemia with KPC-producing Klebsiella pneumoniae 5
Is strain typing required to identify source of infection?
- A patient develops bacteraemia with KPC-producing Klebsiella pneumoniae 5
days after admission to hospital. The patient in the adjacent bed is known to be
colonised with KPC-producing Klebsiella pneumoniae. KPC producing organisms
have never been identified at the hospital before.
› Other characteristic markers?
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Strain Typing in Infection Control
Approaches
Retrospective
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Prospective
Retrospective Strain Typing
Traditional way of utilising strain
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utilising strain typing in infection control
Strain Typing
Case Definition
› Diagnosis
› Time
› Place
› Epidemiologic Parameters
› Strain type
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Prospective Strain Typing
Strain Typing
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Prospective typing increasingly utilised
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New MRSA isolates per day for hospital inpatients
Prospective Strain Typing
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New MRSA isolates per day for hospital inpatients
Prospective Strain Typing
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New Strain A MRSA isolates per day for hospital inpatients
Prospective Strain Typing
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New Strain G MRSA isolates per day for hospital inpatients
Prospective Strain Typing
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Strain typing methods
› Phenotypic
- Serotyping
- Streptococcus pneumoniae
- Phage typing
- Salmonella enterica
› Genotypic
- Pulse-field gel electrophoresis (PFGE)
- Many organisms (MRSA, VRE, MRAB)- Many organisms (MRSA, VRE, MRAB)
- PCR-ribotyping
- Clostridium difficile
- Multilocus variable number of tandem repeats analysis (MLVA)
- Salmonella enterica
- Binary typing
- Staphylococcus aureus
- Single locus sequence typing
- Stapylococcus aureus (spa)
- Multilocus sequence typing (MLST)
- Many organisms
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Typing Method Characteristics
› Discriminatory power
› Reproducibility
› Stability
› Typeability
› Ease of interpretation
› Ease of use
› Portability of results
› Turnaround time
› Throughput
› Cost
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Interpreting Strain Typing Results
A. Yes
B. No
Typing Results: All Part of Outbreak?
Maybe: Depends on discriminatory
power of typing system,
background prevalence of the strain
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background prevalence of the strain
type
Maybe: Depends on stability of the
typing system, how ‘different’ are
the strains
A. Yes
B. No
Interpreting Strain Typing Results
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Interpreting Strain Typing Results
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Transmissible Resistance
Need to consider typing transmissible element as well as the ‘host’
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Conclusions
› Strain typing not necessary for infection control surveillance for all organisms
› Strain typing in infection control may be retrospective or prospective
› Characteristics of the available typing method must be considered before deciding to perform typingdeciding to perform typing
› Characteristics of the typing method must be considered in interpreting the results
› Typing does not provide a ‘Yes’ – ‘No’ answer, but a likelihood
› Transmissible resistance requires a different approach
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