Title: Nosocomial Infections
1Nosocomial Infections
2Today we are going to cover
- The factors that contribute to nosocomial
infections - Examples of nosocomial infections and the
organisms which cause them - Control of nosocomial infections
- Surveillance of nosocomial infections
3(No Transcript)
4Nosocomial infections are
- Infections that are acquired in hospital (48
hours or more after admission) - Approx 9 of patients will suffer from an
infection whilst in hospital risk increases
with length of stay - Significant financial burden on NHS
5Impact of nosocomial infections
- 100,000 infections per year in UK
- 5,000 deaths with nosocomial infections playing a
role in 15,000 others - Costs the NHS 1 billion 9 of its in-patient
budget - Cannot eradicate but its thought they could be
reduced by up to 30 (saving 300,000,000!)
6(No Transcript)
7Best to be proactive rather than reactive!!
8Why are we more likely to get an infection in
hospital?
- Consider 4 important factors
- The host
- The microbes
- The environment
- Treatment
9The host 1
- People in hospital are already sick!
- They may have poor general resistance to
infection - Lack of immunity
- Extremes of age
- Immunocompromised (eg HIV, cancer chemotherapy)
10The host 2
- Reduced immunity
- Diabetes, severe burns
- Poor local resistance
- Poor blood supply to tissues
- Surgery
- Wounds, sutures
- Medical devices
- Catheters, prostheses, tubing etc
11(No Transcript)
12The microbes
- Virtually any infection can be acquired in
hospital - However a number of usual suspects predominate
- What are they, where do they come from and why do
they cause nosocomial infection?
13Opportunistic infections
- Nosocomial infections are often caused by
opportunistic pathogens i.e. those which do not
normally cause infection in healthy people - May be a reflection of reduced defences of host
or access to sites not normally colonised by
organisms - May be from normal flora or environment
- Antibiotic resistance is a problem
14Opportunistic pathogens
- Pseudomonas aeruginosa
- staphylococci
- E. coli and other coliforms
- streptococci and enterococci
- Bacteroides fragilis
- Candida albicans
- Herpes simplex virus
- Cytomegalovirus
15Biofilms
- Biofilms are microbial communities (cities)
living attached to a solid support eg catheters/
other medical devices - Biofilms are involved in up to 60 of nosocomial
infections - Antibiotics are less effective at killing
bacteria when part of a biofilm
16The Environment
- There are many different sources of pathogens
when in hospital - Own normal flora (endogenous)
- Infected patients
- Traffic of staff and visitors
- Environment e.g. fungi, Legionella
- Blood products
- Surgical instruments eg vCJD
17Treatment
- There is continuous usage of antibiotics in
hospitals especially in ICU - As a result there will be a natural selection for
strains that are antibiotic resistant
infections are getting harder to treat - This has led to problems with multi-resistant
bacteria e.g. MRSA, VRE, ESBLs - Antibiotic treatment can also lead to alterations
in normal flora and allow pathogens cause
infection eg C. difficile
18(No Transcript)
19Types of nosocomial infection and their causes
- Data from a single study 1992-97 from a
paediatric ICU and excluding viral infections - Source http//www.emedicine.com/ped/topic1619.ht
msectionclinical
20Bloodstream nosocomial infections
- Coagulase-negative staphylococci, 40
- Enterococci, 11.2
- Fungi, 9.65
- Staphylococcus aureus, 9.3
- Enterobacter species, 6.2
- Pseudomonads, 4.9
- Acinetobacter baumannii with substantial
antimicrobial resistance - Reported with
increasing frequency
21Urinary Tract Infections
- Gram-negative enterics, 50
- Fungi, 25
- Enterococci, 10
22Surgical site infections
- S aureus, 20
- Pseudomonads, 16
- Coagulase-negative staphylococci, 15
- Enterococci, fungi, Enterobacter species, and
Escherichia coli, less than 10 each
23Causes of death
- Primary bloodstream infection
- Pneumonia
- Infection of surgical site
24MRSA
- Methicillin (Meticillin) Resistant Staphylococcus
aureus - S aureus carried by 30 of us (nose/ skin)
- MRSA is no more virulent than MSSA strains but
more difficult to treat - Resistance due to mecA gene encodes PBP2a,
doesnt react with Penicillins - Emerging Vancomycin resistance is a concern
- The Biomedical Scientist Jan 2008 p39-41
25MRSA bacteraemia
26Epidemic MRSA (EMRSA)
- 1984 EMRSA-1 identified in many hospitals in
London and south-east England. - Subsequent surveys showed further 13
multi-hospital MRSA (EMRSA-2 to -14) - Mid-1990s EMRSA-15 and -16 emerged and spread
widely - 591 MRSA isolates received between 1998 and 2000,
60 EMRSA-15, 35 EMRSA-16
27Rapid MRSA screening
- Current methods for screening for MRSA are based
on culture and take 48 hours - PCR-based screening can generate a result in 2
hours! - mecA is carried on a transferable gene cassette
called SCCmec but also found in
coagulase-negative staphylococci - PCR developed using primers for SCCmec and orfX
on the S. aureus chromosome
28Use of SCCmec/orfX PCR
MRSA
No PCR product
MSSA
orfX
No PCR product
MR CN-Staph
mecA
SCC 3 end
Cuny Witte Clin Microbiol Infect (2005)
11834-837
29Vancomycin Resistant Enterococci
30Extended spectrum ß-Lactamases
- ESBLs are responsible for resistance to 3rd
generation Cephalosporin antibiotics such as
Ceftazidime and Cefotaxime - Resistance is found in E. coli and other members
of the Enterobacteriacae - Often cross-resistance with other antibiotics
making treatment difficult use imipenem
31(No Transcript)
32Clostridium difficile
- Causes antibiotic-associated diarrhoea and
pseudomembranous colitis life-threatening
illnesses - Normally affects only the elderly, especially
those on long-term broad-spectrum antibiotics - Produces two powerful toxins and is a
spore-former difficult to eradicate, resistant
to alcohol - Reasons for recent increases still not known
33(No Transcript)
34Clostridium difficile
- Nosocomial disease spread primarily by hands of
staff and outbreaks are common - Patients generally respond to discontinuation of
the inciting agent or therapy with metronidazole
or vancomycin. Response is rapid but Mtz and Vanc
may also alter normal flora and may allow disease
to recur - Once the colon is injured it is more susceptible
to re-infection. Relapse rates are up to approx
20 - Almost impossible, at present, to rid the
environment of C. difficile spores - Some use 1000-10000ppm hypochlorite highly
caustic and damaging to surfaces. There may be
rapid re-contamination of environment.
35Nosocomial transmission of C. difficile
- Contamination rates after contact with CDAD
patients - Physicians medical Students
75 of the time - Dialysis Technicians
66 of the time - Nurses
56 of the time - Physiotherapists
50 of the time - Underside of fingernails
43 - Fingertips and Palms
37 - Underside of Rings
20 - C difficile spores remain in environment in
34-58 of sites after detergent cleaning - CDC 2005
36Success story
- Scunthorpe and Goole NHS trust looked at changing
their antibiotic prescribing policy to reduce the
incidence of C. difficile disease - Cost 12,000 extra to implement
- Saved 280,000 in staffing, bed occupancy,
treatment, use of isolation rooms etc, oh, and
some lives!
37Infection Control
- Infections may derive from endogenous
(auto-infection) or exogenous sources
(cross-infection) - We need to consider the chain of infection and
the transmission of an infectious agent
38(No Transcript)
39Transmission
- Contact most common
- Direct (physical contact)
- Indirect (via contaminated objects)
- Airborne Transmission
- Droplet respiratory secretions on surfaces
- Inhalation of infectious particles
- Blood-borne transmission
- Food-borne
40The Cycle of Contagion
41The Cycle of Contagion
42The Cycle of Contagion
Immunisation or prophylaxis
Immunisation or prophylaxis
Individual treatment
Infection control hygiene
43Role of infection control teams
- Education and training
- Development and dissemination of infection
control policy - Monitoring and audit of hygiene
- Clinical audit
44(No Transcript)
45The 5 pillars of infection control
46Tabloid sensationalism?
Hospital superbug 'out of control' as child
MRSA cases rise to 150
47Government response
Hospital superbug must be halved Bloodstream
infections with the hospital superbug MRSA must
be halved in three years, the government has
said. Health Secretary John Reid tasked NHS
hospitals with achieving a year on year reduction
up to and beyond March 2008.
48Government meddling??
- By forcing targets on NHS trusts for reduction of
MRSA numbers, has this led to an increase in
infections with other superbugs? - Hand washing with alcohol-based antiseptics is
fine for decontamination of MRSA but have no
effect on spores of C. difficile - need to wash
with soap and water
49Surveillance
- Continuous monitoring of the frequency and
distribution of infectious diseases - Determines the most important causes of
infectious diseases and identifies at risk groups
50Uses of surveillance
- Used to identify new problems
- Used to identify where resources are most needed
- Used to determine the burden of disease
- Used for strategic planning and policies
- Use surveillance for measuring outcomes of
intervention strategies
51Epidemiology
- Surveillance is also used to detect epidemics and
outbreaks - Epidemiologists at Centre for Infections analyse
data sent from laboratories throughout the
country
52- Surveillance reports published in CDR weekly
http//www.hpa.org.uk/cdr/index.html - But how do Biomedical Scientists help with this
work? - Isolating and identifying the pathogens -
hospitals - Typing specialist laboratories
53Typing of pathogens
- There are many different strains of a bacterial/
fungal/ viral species so in order to identify a
possible outbreak and identify the source we need
to discriminate between organisms of the same
species - This is called typing there are a number of
methods available - Those based on phenotype (traditional)
- Those based on genotype (recent)
54Typing methods
- Typing is usually performed at specialised
Reference Laboratories such as those at HPA
Centre for Infections - Different methods are used for different
pathogens use the one which gives best
discrimination - Pathogens of the same type may be part of an
outbreak, if they are of a different type an
outbreak can be ruled out
55Phage Typing
- Phage (bacteriophage) is a virus that infects and
kills bacteria - Different strains are susceptible to different
phages - Gives a fingerprint that can discriminate between
strains - Used in the typing of S. aureus and Salmonella
56Serotyping
- Used to detect variations in certain antigens
present on the pathogen - Use specific antisera and observe a
Antibody-Antigen reaction (usually a
precipitation or agglutination reaction) - Eg Streptococcus pyogenes M-protein typing M1
type is important in invasive infections (flesh
eating etc) - H and N typing of influenza eg H5N1
57Colicine typing
- Colicines (bacteriocins) are produced by certain
bacterial species that inhibit the growth of
other members of the same species - Look for patterns of sensitivity/ resistance with
different colicines - Eg Pseudomonas
58Biotyping
- Biotyping explores the metabolism of an organism
eg a particular enzyme activity or ability to
ferment a particular sugar - Eg. coagulase-negative staphylococci
59Genotyping
- There are a number of methods available most
rely on sequence variation in non-coding
(intergenic) DNA - This variation is characteristic of a particular
strain (or type) - Strains from an outbreak will be the same type
- Similar to DNA fingerprinting used in CSI and
paternity disputes
60Restriction Fragment Length Polymorphism (RFLP)
- DNA extracted from bacterial isolates is digested
(cut) with a restriction enzyme eg EcoR I - Produces DNA fragments of varying size gel
electrophoresis - Pattern of bands is strain-specific
61Pulsed Field Gel Electrophoresis
- Used to separate large DNA fragments gt10 kb
- Chromosomal DNA digested with restriction enzyme
and fragments separated by PFGE - Banding pattern is strain specific used e.g in
MRSA typing
62Summary 1
- Can you explain in detail why patients in
hospital are more prone to infection? - Can you define a primary and an opportunistic
pathogen? - Can you give examples of nosocomial infections,
with predisposing factors and examples of the
pathogens which cause them? - Can you discuss infections due to MRSA and C.
difficile in detail?
63Summary 2
- 5. Can you discuss the transmission of infection
in hospitals, uses of infection control and the
role of infection control teams? - Why is surveillance of nosocomial infections
important? - What is the role of the laboratory in the
diagnosis and surveillance of nosocomial
infections? - Can you give examples of the methods used in the
laboratory for diagnosis and surveillance of
nosocomial infections?