Epidemiology and control of Streptococcus pyogenes in the health care setting

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Epidemiology and control of Streptococcus
pyogenes in the health care setting

• Dr Elisabeth Ridgway
• Consultant Microbiologist
• Royal Hallamshire Hospital, Sheffield

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Lecture outline

• The organism
• The scale and spectrum of streptococcal infection
• Historical association with health care
• How common is GAS HCAI?
• Control measures
• Recognising a problem when to take action
• Dealing with staff patients
• The role of the environment

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Streptococcus pyogenesMicroscopic appearance
colonial morphology
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Infections caused by Streptococcus pyogenes (GAS)

• Superficial diseases
• pharyngitis, skin soft tissue infn, erysipelas,
• impetigo, vaginitis, post-partum infn
• Deep infections
• bacteraemia, necrotising fasciitis, deep soft
• tissue infn, cellulitis, myositis, puerperal
  sepsis,
• pericarditis, meningitis, pneumonia, septic
• arthritis
• Toxin-mediated
• scarletina, toxic shock-like syndrome
• Immunologically mediated
• rheumatic fever, post-streptococcal GN,
• reactive arthritis

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Group A streptococcal infection Overall disease
burden

• Each year
• 1.8 million new cases of serious infection
• at least 500,000 deaths
• 110 million cases of soft tissue infection
• 610 million cases of pharyngitis
• At least 18 million people suffer the
  consequences of serious GAS diseases

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Invasive group A streptococcal infection UK

• UK surveillance historically based on laboratory
  bacteraemia reports - underestimates invasive
  infection.
• 1990 563 reports in EW
• PHLS enhanced surveillance of iGAS disease
• (EW) 1994-97
• ? 650-700 bacteraemia cases p.a

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European enhanced surveillance of iGAS disease

• From January 2003
• for 2 years
• in 11 countries

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Bacteraemia iGAS

• Bacteraemia
• 2002 1025 reports
• 2003 1866 (Enhanced surveillance began)
• 2004 1604
• Rate 2.9/100,000
• (1.9 - 4.1/100,000)
• iGAS (strep-EURO)
• 2.95/100,000 (EWNI)

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Group A streptococcal infection and health care
Alexander Gordon (1752-1799) ... seized such
women only as were visited, or delivered, by a
practitioner or nurse, who had previously
attended patients affected by the disease.a
specific contagion, or infection.... I could
venture to foretell what women would be affected
with the disease, upon hearing by what midwife
they were to be delivered.. 1795
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Group A streptococcal infection and health care
Ignaz Philipp Semmelweis (1818-1865) All
students or doctors who enter the wards for the
purpose of making an examination must wash their
hands thoroughly in a solution of chlorinated
lime which will be placed in convenient basins
near the entrance of the wards. This disinfection
will be considered sufficient for this visit.
Between examinations the hands must be washed in
soap and water. 1847
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Group A streptococcal infection and health care
Louis Pasteur (1822-1895) It is the nursing
and medical staff who carry the microbe from an
infected woman to a healthy one. This water,
this sponge, this lint with which you wash or
cover a wound, may deposit germs which have the
power of multiplying rapidly within the
tissue.... If I had the honour of being a
surgeon....not only would I use none but
perfectly clean instruments, but I would clean my
hands with the greatest care... 1879
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How common is GAS cross infection?
Bacteraemia and surveillance data
Percent HAI
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strep-EURO data on GAS HAI
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Features of GAS HCAI

• Ontario 1992-2000
• Secondary cases significantly more likely after
  HA than CA infection.
• 10 of HA-iGAS associated with in-hospital
  transmission.
• Overall Mortality 17. 37 if non-surgical,
  non-obstetric.
• 67 within 72 hours of first positive sample.
• 15 hospital outbreaks
• Duration 1-13 days (median 7days)
• 60 involved only 2 cases (range 1-10)
• Only 1 outbreak had symptomatic staff
• 60 had at least one asymptomatic HCW
• Clin Infect Dis 200541334-42

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GAS cross infection Principles of management

• Isolate admissions with CA-infection
• Prompt recognition of the cross-infection
  episodes
• Identification and control of the source of
  infection
• Identification and treatment of cases and
  carriers
• Appropriate isolation IC precautions
• Environmental decontamination
• CDC recommendations (CID 2002 35950-9)
• Not always as straightforward as it should be!

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GAS on a Burns Unit
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GAS in hospitals When to take action?

• Even one GAS infection is reason for concern and
  two or more cases in a short time period should
  alert the infection control team that a full
  scale epidemic investigation is warranted.
• High risk units eg. Maternity/neonatal/surgical
  wards Single case
• Know the epidemiology of your high risk units
• Be aware of activity in the community
• Store strains from cases and contacts
• Type strains to clarify the epidemiology
• React quickly start investigation before
  results come back incubation of cases is 1-3
  days.

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The hospital is part of the community it serves
Sheffield 2004
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GAS on a Burns Unit
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GAS in hospitals Case finding

• Identification of all cases and carriers is
  essential
• Passive surveillance is inadequate
• Well-taken throat swab 95 sensitive for GAS
• Undertake promptly because of rapid transmission.
• Screening of patients
• Nose, throat
• Breaches of skin mucous membranes

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Identifying staff cases carriers

• Cases
• Symptomatic infection uncommon compared to
  carriage
• CA-NF/pneumonia on ICU ? symptoms in 30 HCW
• (CID 20026 351353-9)
• Usually presents within 3-4 days of contact
• Illness reporting by staff important.
• Transmission to family members uncommon
• Carriers
• GAS carriage sites anus, vagina, skin, throat
• Dissemination is common

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Identifying managing staff carriers

• Initially screen those involved directly with the
  patient
• HCW present before during delivery
• HCW in theatre or dressing changes
• Sites anterior nares, throat, vagina, rectum and
  skin
• Positives off until 48 hours of antibiotics
• Antibiotic regimen depends on carriage site
• Pen/- rifampicin, clindamycin, oral vancomycin
  rifampicin
• Screen more widely depending on findings and
  typing

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Managing staff carriers

• Check for eradication 7-10 days after completing
  treatment
• Relapses common
• Household contacts
• Toothbrushes false teeth
• Periodic screens for 12 months
• Coordinated effort by ICT and Occupational Health
• Identification of contacts
• Information support
• Compliance with screening may be an issue

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GAS on a Burns Unit
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GAS cross infectionThe role of the environment

• GAS can remain viable in the environment for
  prolonged periods
• Inoculation of moistened contaminated dust led to
  infection as often as contaminated secretions
• (J Hyg Camb 1958 56 280-87)
• Contaminated blankets/ nasopharyngeal inoculation
  of dry contaminated dust did not lead to
  infection
• (Am J Hyg 1957 66 85-95 and 96-101)
• Damaged skin mucous membranes vulnerable to
  environmental transmission

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GAS cross infectionThe role of the environment

• Maternity unit Showerhead (JHI 1985 6 304-311)
• Dermatology ward Vinyl sheeting (JHI 1998 40
  135-140)
• Nursing home Shared wash cloth (EID 2003 9
  (10))
• Gloucestershire nursing home (JHI 1995 30162-4)
• Percent positive (no. tested)
  Percent positive (no. tested)
  before cleaning after
  cleaning
• Upholstered chairs 93 (15) 8 (12)
• Carpets 100 (8) 0 (6)
• Curtains 88 (16)
  13 (15)
• Thorough cleaning is essential to reduce the risk
  of environmental contamination

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GAS on a Burns Unit
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GAS cross infectionThe role of the environment

• Postoperative death from
• iGAS sepsis
• Same strain retrieved from
• anaesthetic trolley 48 hours
• after procedure
• All staff screened negative
• 3 members of extended family
• with strain of same serotype
• and 2 with different serotypes
• Probably pharyngeal carriage
• at time of procedure

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Group A streptococcal cross infectionAntibiotic
prophylaxis

• No longer routinely given on burns units
• Effective in controlling some outbreaks...
• Detention centre (BMJ 1982 285 95-6)
• Nursing homes (Arch Int Med 1992 152 1017-22
  EID 2003 9(10))
• ... but not others.
• Military camp (NEJM 1991 325 92-7)
• Semi-closed community (Lancet 1980 2 498-502)
• Need to give to all personnel to be effective
• Less acceptable for staff than patients (J Clin
  Micro 198419 366-70)
• Does not replace good infection control practice

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GAS HCAI Conclusions

• GAS HCAI is not a new problem
• iGAS infections increasing
• Recognise HA infection and act promptly
• Active management of patients and staff is
  required in outbreaks
• The environment may be implicated in transmission
• Consider the role of antibiotic prophylaxis
• Outbreaks in some settings may be difficult to
  control

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Thank you - Any questions?