Epidemiology and control of Streptococcus pyogenes in the health care setting

Dr Elisabeth Ridgway

Consultant Microbiologist

Royal Hallamshire Hospital, Sheffield

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

Streptococcus pyogenes:Microscopic appearance & colonial morphology

Infections caused by Streptococcus pyogenes (GAS)

• Superficial diseasespharyngitis, skin & soft tissue infn, erysipelas,impetigo, vaginitis, post-partum infn

• Deep infectionsbacteraemia, necrotising fasciitis, deep softtissue infn, cellulitis, myositis, puerperal sepsis,pericarditis, meningitis, pneumonia, septicarthritis

• Toxin-mediatedscarletina, toxic shock-like syndrome

• Immunologically mediatedrheumatic 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

00.5

11.5

22.5

33.5

44.5

Rate per 100,000 popn

Bacteraemia2002: 1025 reports2003: 1866 (Enhanced surveillance began)2004: 1604

Rate: 2.9/100,000 (1.9 - 4.1/100,000)

iGAS (strep-EURO)

2.95/100,000 (EW&NI)

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?

O ntario 92 -2000

Atlan ta 94 -95

P HLS 94-97

Riyadh 82-92

D enm ark 87-89

London 70-97

Zagreb 1980s

B oston 64-66

M innesota 71-77

New Y ork 60-68

0 10 20 30 40 50 60 70

Percent HAI

Bacteraemia and surveillance data

strep-EURO data on GAS HAI

France 18%

Sweden 4%

Finland 10%

Romania 4%

Greece 9%

Czech Rep 26%

Italy 14%

UK 8%

Germany 12%

Denmark 0%

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

4

3

2

1

1

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Sept Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug

Staff

Patients

No

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col o

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Same patient

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…

Sheffield 2004

0

20

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160

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200

w/c15/2

w/c22/2

w/c29/2

w/c7/3

w/c14/3

w/c21/3

w/c28/3

w/c4/4

w/c11/4

w/c18/4

w/c25/4

w/c2/5

w/c9/5

w/c16/5

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35

Invasivecases

Week

Number ofswabsreceivedin RHH lab

% positive for GAS

GAS on a Burns Unit

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3

2

1

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Sept Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug

Staff

Patients

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Same patient

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

4

3

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Sept Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug

Staff

Patients

No

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Symptomatic Symptomatic

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) 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

GAS on a Burns Unit

4

3

2

1

1

2

Sept Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug

Staff

Patients

No

. in

fect

ed

or

col o

ni s

ed

Environmental screening

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?