Lecture 19 Nosocomial infections

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Lecture 19Nosocomial infections

• Aims
• To be able to define the term nosocomial
  infections
• to become aware of the nature of microbes
  associated with nosocomial infections
• To become aware of the clinical procedures which
  increase the risk of nosocomial infections
• To be aware of the control measures that can b
  used to minimize the risk of developing
  nosocomial infections

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Nosocomial infections

• In the US about 5 of patients develop an
  infection in hospital even though they entered
  hospital without an infection

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Nosocomial infections defined

• Generally a nosocomial infection may be defined
  as
• An infection arising in patient (usually at least
  48 post admission) that was not present or
  incubating on admission
• It may include infections post discharge if the
  infection started whilst the patient was admitted

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Nosocomial infections 1

• Characteristics
• many infections are endogenous in nature
• some exogenous infectious agent may only occur in
  the healthcare setting (exceptions occur)

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Infectious disease control

• Microbes mainly found in hospitals
• 3 main groups
• MRSA
• GRGNs
• GN endotoxaemia (/- associated with GRGN)

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MRSA

• Multi (Methicillin) resistant S.aureus
• MRSA is endemic in many Australian hospitals
• The treatment of choice for S.aureus is
  fluclocxacillin (methicillin)
• MRSA is sensitive essentially only to (with few
  exceptions) vancomycin
• Alternative drugs are generally not recommended
  unless excepional circumstances

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MRSA

• MRSA in terms of pathogenicity is generally
  regarded the same as S.aureus
• MRSA can be associated with seriius infections
  in
• orthopaedic patients
• lung infections in ICU patients
• ss wound infections

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MRSA

• Infections can be transmitted from carriers
• Includes health care professions and previously
  colonized patients
• may transiently colonize the nares, groin and
  axillae
• Recent reports indicate that MRSA has been
  detected in some WA and NT aboriginal
  communities- epidemiology not fully understood

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MRSA

• Patients being transferred between health care
  institutions should be screened for
  MRSA(Methicillin MSA plate)
• Patients known to be colonized with MRSA should
  receive prophylactic vancomycin if undergoing
  surgery
• VRE has been reported and some suggestion that
  VRSA is known overseas

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Gentamicin Resistant Gram negative bacteria

• GRGNs may arise due to the extensive use of
  gentamicin for the treatment of G-e infections
• Includes bacteria which which may display
  multiresistance eg to betalactams such as the
  cephalosporins
• eg Pseudomonas sp
• Enterobacter sp
• Acinetobacter sp

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GRGNs

• Can be screened for eg faecal swab on Gentamicin
  containing plates
• GRGNs are not as prevalent in Australian
  hospitals, but are becoming an increasing problem
• Can cause severe and difficult to treat
  infections in compromised hosts eg
• Burns patients
• Para/quadraplaegic patients
• long term ICU patients

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Gram negative sepsis leading to endotoxamia

• This is an emerging problem for ICU patients on
  parenteral feeding
• Seems that without bulk feeding that the gut may
  become leaky to endotoxins or GN bacteria -gt
  endotoxaemia
• poor prognosis (death rate 20-80)
• bacteria may also derive from prior lung, GI or
  UTI/genital tract infection

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Endotoxaemia

• E.coli is by far the greatest cause (gt80)
• other enteric gram negative bacteria include
• Enterobacter sp
• Klebsiella sp
• Proteus sp
• may also include Pseudomonas sp
• P.aeruginosa
• P.cepacia

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Why do nosocomial infections occur?

• Question is complex
• The patients are compromised in some way
• We may have to interfere with the patients
  immunity (non specific and specific)
• We may expose sterile sites to endogenous
  /exogenous bacteria
• Exogenous bacteria (including a/b resistant
  forms) are present in the environment on on
  health care providers

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Specific procedures that increase the risk of NIs
and their control measures

• Central and venous cannulation
• Risk Factors
• duration of cannulation
• catheters are readily colonized by bacteria
  proximate to the site
• Staphlococci
• Streptococci
• G-e bacteria if proximate to the groin

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Central and venous cannulation

• Control measures
• Choice of site and device
• central v peripheral
• arm v groin
• Care during insertion (minimize trauma)
• Aseptic method
• maintaining hygiene (surveillance)
• phlebitis, cellulitis
• Reduce duration ASAP

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Urinary catheters

• Risk factors
• Provides a common route for ascending infection
• Mainly G- bacteria (staphs and streps can be
  involved)
• Main G-e bacteria include
• E.coli, Proteus sp., Klebsiella sp Psuedomonads
• Bacteraemia may occur even at times if the
  patient appears asymptomatic
• The longer the catheter is in place the more
  inevitable a UTI seems

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Urinary catheters

• Control
• Aseptic and no traumatic insertion
• Appropriate choice of catheter
• Closed rater than open bag systems
• Good site hygiene
• Removal of catheter ASAP

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Intubation

• Risk factors
• Intubation bypasses the respiratory mucous
  escalator
• Long term intubation is often associated with a
  progression from lung infection with initially G
  bacteria to G- to resistant Gram negative
• Risks are increased as these patients are usually
  cannulated as well (IV, UT)

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Intubation

• Control Measures
• Surveillance is essential-
• pyrexia hypotension cloudy urine bags
• Microbiological monitoring eg B/C, urine
• Removal of devices ASAP
• Maintenance of devices
• Level of isolation commensurate with risk
• Nasogastric feeding v parenteral
• Review of antibiotic regimen