1. Dr. Mona, Chiu Lai Shan, 趙麗珊 Specialist in Dermatology and Venereology
Treatment of Skin Bacterial Infections in the Era of Community Associated Methicillin Resistant Staphylococcus Aureus (CA-MRSA)
Dr. Mona, Chiu Lai Shan, 趙麗珊
Specialist in Dermatology and Venereology

2. Lecture outline S. aureus skin infection
Epidemiology and clinical characteristics of CA-MRSA
Approach to CA-MRSA skin infection

3. Some facts about S. aureus
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

4. Skin infections caused by S. aureus
Local
Cellulitis
Abscess
Carbuncle
Furuncle
Impetigo
Necrotizing fasciitis
systemic
Staphylococcus scalded skin syndrome
Toxic shock syndrome

5. When should we suspect that’s CA-MRSA
Epidemiology
-local prevalence
-occupation
-hobby
-travel history
Clinical features
Laboratory
-antibiotic resistance profile

6. Background
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”

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

9. Mechanism of methicillin resistant in S. aureus
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)

10. Mechanism of methicllin resistance in S. aureus
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

11. 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

12. Epidemiology-MRSA
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

13. Epidemiology of MRSA
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

14. Epidemiology of MRSA-China
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

16. Prevalence of CA-MRSA
The incidence of CA-MRSA in children with skin and soft tissue infections was 1.1–4% in Beijing
Similar in other major provinces

17. CA-MRSA in Hong Kong
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

18. CA-MRSA in Hong Kong
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

21. CA-MRSA in Hong Kong
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

22. Dermatological presentation of CA-MRSA
Most common complain “spider bite” lesions
Morphology:
Papules
Pustules
Erythematous or crusted erosions
Plaques
Nodules
Distribution
Legs
Knees
Thighs
Feet
Buttock

23. Dermatological manifestation
Abscess
Cellulitis
Folliculitis
Furunculosis
Impetigo
Paronychia

24. Dermatological manifestation
Severe infection:
Necrotizing fasciitis
Bullous erysipelas
Staphylococcus scalded skin syndrome and staphylococcus toxic shock syndrome
Purpura fulminans
Ecthyma gangrenosum

25. Antibiotic resistance profile of CA-MRSA
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

26. Antibiotic resistance profile of CA-MRSA-China
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

27. Antibiotic resistance profile of CA-MRSA in Taiwan Y. -C. Huang, C. -J
Antibiotic resistance profile of CA-MRSA in Taiwan Y.-C. Huang, C.-J. Chen / International Journal of Antimicrobial Agents 38 (2011) 2–8

28. Antibiotic susceptibilities of community-acquiredStaphylococcus aureus isolates recovered from children at Texas Children's Hospital from 1 August 2001 through 31 July 2004.
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:
© 2005 by the Infectious Diseases Society of America

29. Antibiotic resistant profile of S. aureus in AD patients in Korea
Chung HJ et al. Journal of Clinical Microbiology (3):

30. When to suspect CA-MRSA infection:
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

31. Basic steps in evaluation and treatment of CA-MRSA
Thorough medical history and social history
Clinical examination: abscess, cellulitis
Risk evaluation: life threatening condition (necrotizing fasciitis)
Appropriate culture before empirical antibiotic treatment
Drainage of collections
Review culture results and clinical response
Report any confirmed case and contact tracing
Follow up and decontimination

32. Decolonization of CA-MRSA
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

33. Conclusions 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

34. Thank you