Dr. Mona, Chiu Lai Shan, Dr. Mona, Chiu Lai Shan, 趙麗珊趙麗珊Specialist in Dermatology and Specialist in Dermatology and

Venereology Venereology

1. S. aureus skin infection 2. Epidemiology and clinical characteristics

of CA-MRSA3. Approach to CA-MRSA skin infection

Colonize the anterior nares in one third of healthy population

Colonize the skin of most atopic dermatitis patients (up to 100% in those with severe AD)

Common pathogen for skin infection Notorious for secretion of various toxins and

superantigens (TSST, enterotoxin) which can cause serious infection and promote inflammation

Local Cellulitis Abscess Carbuncle Furuncle Impetigo Necrotizing fasciitissystemic Staphylococcus scalded skin syndrome Toxic shock syndrome

Epidemiology -local prevalence-occupation-hobby-travel history Clinical features Laboratory -antibiotic resistance profile

1981-CA-MRSA outbreak was first described in United States in a group of intravenous drug users

1990s-multiple CA-MRSA outbreaks were documented among different states in the United States

1999-identify as a virulent pathogen after it was identified as the causative organism in the death of four previously healthy children in Minnesota and North Dakota

2004-CA-MRSA was referred as “ an emerging epidemic”

PR Cohen. International Journal of Dermatology 2007. 46:i-11

Methicillin resistance is mediated by the methicllin resistance gene: mecA gene

The gene is responsible for beta-lactam resistance by encoding the methicillin-resistant penicillin binding protein 2a (PBP2a) which has a low affinity for beta-lactam type antibiotics

The genetic elements that carries the mecA gene is the staphylococcal cassette chromosome (SCC)

HA-MRSA infection is associated with SCCmec type I, II, III

CA-MRSA infection is associated with SCCmec type IV and V which lacks other multidrug resistance genes

CA-MRSA is more frequently associated with exotoxins than the HA-MRSA counterpart

Panton-Valentine leukocidin (PVL) toxin is the most common toxin

It is lethal to neutophils and is a potent dermonecrotic toxin. It is also associated with necrotizing pneumonitis

HA-MRSA CA-MRSA

Patient population Acquired after staying more then 48 hours in the hospital

Community without exposure to the hospital environment

Pre-disposing factors Surgery, intubation, catheter, dialysis, prior MRSA infection, long term care facility

Members of military, IVDU, homosexual males, children, athletes, inmates, Pregnant women, chidren and infants

Virulent factors SCCmec type I to III SCCmec type IV or V, Panton-Valentine leukocidin

Clinical presentations Systemic infection such as UTI and pneumonia

Most common soft tissue and skin infection

Antibiotic resistance profile Resistant to most antibiotics except few (e.g.vancomycin, linezolid)

Resistant to beta-lactam group of antibiotic but susceptible to quinolones and trimethoprim. Topical fusidic acid and mupirocin. Some are susceptible to clindamycin

Large population based survey in the United States showed a 0.84% of overall MRSA colonization rate versus 31.6% of MSSA

Worldwide, the overall MRSA colonization rate range from 0.26% to 9.2%

The overall prevalence of MRSA is around 1.4% in our locale and most of them are associated with health-care exposure

The prevalence is similar in the United Kingdom (1.5%) and <1% in Italy, Portugal and Canada

The rate of MRSA colonization is higher in healthy school children in Asian countries: 5.1% in South Korea, 4.3% in Japan, and

1.9% in Taiwan

There were significant differences in the prevalence of MRSA among distinct regions of China, with the highest prevalence, 76.9%, in east China, 52.3% in the southwest and about 60% in other regions

The prevalence of MRSA in certain cities such as Shanghai, Beijing, and Guangzhou was high relative to other

32.7% of S. aureus isolated from pediatric patients was MRSA, which was about half that seen in adult patient

The incidence of CA-MRSA in children with skin and soft tissue infections was 1.1–4% in Beijing

Similar in other major provinces

MRSA among patients presenting to the emergency department with purulent SSTI were studied over a 4-month period from November 2006 to February 2007.

It involved the emergency departments in six regional hospitals estimated to provide service to half of the 6.6-million inhabitants in Hong Kong

Wound swabs were obtained for culture from all patients who present with purulent SSTIs of less than 7 days duration

A total of 298 patients aged 2 to 97 with purulent SSTIs were recruited

S. aureus was isolated from 126 (42%) patients Among patients with purulent SSTIs, 10%

(13/125) of all S aureus isolates was attributed to PVL-positive community-associated MRSA

MRSA was isolated from 5% (13/241) of abscesses, 13% (5/40) of infected wounds, and 17% (1/6) of purulent discharges associated with cellulitis

In univariate analysis, Filipino ethnicity was significantly more likely than Chinese to be infected by PVL-positive community- associated

All other clinical and epidemiologic features were not predictive of PVL- positive community-associated MRSA

Most common complain “spider bite” lesionsMorphology: Papules Pustules Erythematous or crusted erosions Plaques NodulesDistribution Legs Knees Thighs Feet Buttock

• Abscess• Cellulitis• Folliculitis• Furunculosis• Impetigo• Paronychia

Severe infection: Necrotizing fasciitis Bullous erysipelas Staphylococcus scalded skin syndrome and

staphylococcus toxic shock syndrome Purpura fulminans Ecthyma gangrenosum

All are resistance to Beta-lactam group of antibiotics

Most are susceptible to ciprofloxacin, rifampacin, cotrimoxazoles, vancomycin, mupirocin and fusidic acid

Most are resistance to erythromycin Some are resistance to Clindamycin Resistance to older generation of

fluoroquinolones is observed

Resistance rates of 57.1–85.7% to macrolides, clindamycin, aminoglycosides, sulfamethoxazole-trimethroprim, quinolones, and tetracycline

Resistance rate to rifampicin was 28.6%

Y.-H. Xiao et al. Drug Resistance Updates 14 (2011) 236–250

Antibiotic susceptibilities of community-acquiredStaphylococcus aureus isolates recovered from children at Texas Children's Hospital from 1 August 2001 through 31 July 2004.

Kaplan S L et al. Clin Infect Dis. 2005;40:1785-1791

© 2005 by the Infectious Diseases Society of America

Chung HJ et al. Journal of Clinical Microbiology 2008. 46(3):991-995

Clues for CA-MRSA infection- In area of high prevalence- Highly susceptible groups- Contact history - ?more pus and discharge due to presence

of PVL toxins- Antibiotic susceptibility profile

1. Thorough medical history and social history2. Clinical examination: abscess, cellulitis3. Risk evaluation: life threatening condition

(necrotizing fasciitis)4. Appropriate culture before empirical antibiotic

treatment 5. Drainage of collections6. Review culture results and clinical response7. Report any confirmed case and contact

tracing8. Follow up and decontimination

Decolonization in infected persons is indicated in preventing recurrence and transmission of CA-MRSA

Common decolonizing regime: 7.5%/10% povidine iodine soap, 4% chlorhexidine-gluconate liquid detergent, triclosan preparations, mupirocin

Active contact tracing and MRSA decolonisation with daily nasal mupirocin and chlorhexidine detergent for showers for 5 days are offered to all carrier is the current regime used in Hong Kong

CA-MRSA is an emerging epidemics Skin and soft tissue infection is the most

common site of CA-MRSA infection Prompt treatment is needed to prevent

bacteremia which can lead to life threatening conditions such as necrotizing pneumonia

Incision and drainage is the most effect treatment for abscesses

The choice of empirical antibiotics depends on different localities as resistance profiles varies a lot at different countries