Epidemiology and control of
Streptococcus pyogenes in
the health care setting
Dr Elisabeth Ridgway
Consultant Microbiologist
Royal Hallamshire Hospital, Sheffield
Lecture outline
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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
Streptococcus pyogenes:
Microscopic appearance & colonial morphology
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
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
Invasive group A streptococcal
infection: UK
• UK surveillance historically based on laboratory
bacteraemia reports - underestimates invasive infection.
 1990: 563 reports in E&W
 PHLS enhanced surveillance of iGAS disease
(E&W): 1994-97
 650-700 bacteraemia cases p.a
European enhanced surveillance
of iGAS disease
From January 2003
for 2 years
in 11 countries
Bacteraemia & iGAS
 Bacteraemia
2002: 1025 reports
2003: 1866 (Enhanced surveillance began)
2004: 1604
4.5
NI
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rk
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 iGAS (strep-EURO)
2.95/100,000 (EW&NI)
Yo
Rate: 2.9/100,000
(1.9 - 4.1/100,000)
4
3.5
3
Rate per
2.5
100,000
2
popn
1.5
1
0.5
0
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
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
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
How common is GAS cross infection?
Bacteraemia and surveillance data
Boston 64-66
New York 60-68
Minnesota 71-77
Zagreb 1980s
London 70-97
Denmark 87-89
Riyadh 82-92
PHLS 94-97
Atlanta 94-95
Ontario 92-2000
0
10
20
30
40
Percent HAI
50
60
70
strep-EURO data on GAS HAI
Sweden 4%
Finland 10%
Denmark 0%
Czech Rep 26%
UK 8%
Germany 12%
Romania 4%
France 18%
Italy 14%
Greece 9%
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 2005;41:334-42
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; 35:950-9)
• Not always as straightforward as it should be!
GAS on a Burns Unit
Patients
4
3
2
1
Sept
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
1
2
Staff
Same patient
Jul
Aug
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.
The hospital is part of the
community it serves…
200
35
180
Number of
swabs
received
in RHH lab
30
160
140
Invasive
cases
25
120
% positive
for GAS
20
100
15
80
60
10
40
5
20
0
0
w/c w/c w/c
15/2 22/2 29/2
w/c
7/3
w/c w/c w/c
14/3 21/3 28/3
w/c
4/4
w/c w/c w/c
11/4 18/4 25/4
w/c
2/5
w/c
9/5
w/c
16/5
Week
Sheffield 2004
GAS on a Burns Unit
Patients
4
3
2
1
Sept
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
1
2
Staff
Same patient
Jul
Aug
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
Identifying staff cases & carriers
Cases
• Symptomatic infection uncommon compared to carriage
• CA-NF/pneumonia on ICU  symptoms in 30% HCW
(CID 20026; 35:1353-9)
• 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
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
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
GAS on a Burns Unit
STAFF SCREENING
Patients
4
3
2
1
Sept
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
1
2
Staff
Symptomatic
Symptomatic
Aug
GAS cross infection:
The 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
GAS cross infection:
The 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; 30:162-4)
Percent positive (no. tested)
before cleaning
Upholstered chairs
Carpets
Curtains
93 (15)
100 (8)
88 (16)
Percent positive (no. tested)
after cleaning
8 (12)
0 (6)
13 (15)
• Thorough cleaning is essential to reduce the risk of
environmental contamination
GAS on a Burns Unit
Patients
4
3
2
1
Sept
Oct
Nov
Dec
Jan
Feb
Mar
1
2
Staff
Environmental screening
Apr
May
Jun
Jul
Aug
GAS cross infection:
The 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
Group A streptococcal cross infection:
Antibiotic 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 1984;19: 366-70)
• Does not replace good infection control practice
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
Thank you - Any questions?