MRSA– Methicillin resistant Staphylococcus Aureus –

Florian Schneider – med in spe –

Current Health Problems in Students‘ Home Countries

Univerzita Karlova v Praze - Department of Hygiene

Lékařská Fakulta v Hradci Králové

Šimkova 870

500 01 Hradec Králové

MRSA – General Problem

• Bacteria found in hospitals are special majority developed a resistance against antibiotics used there! patient’s original bacterial flora (natural & sensitive to antibiotics) becomes gradually replaced (contaminated) by these resistant bacteria (artificially evolved by continuous exposure to antibiotics)

• One certain bacterial strain is again and again mentioned in this relation: the Staphylococcus aureus, which is tagged by resistancy to methicillin antibiotics. Thus: Methicillin (also: Oxacillin) Resistant Staphylococcus Aureus (MRSA // ORSA)

• Example: Patients coming to the hospital for first time have only 20 % of their skin bacteria resistant to antibiotics. Patients coming for a second or third time (the patients who were in the hospital previously) already have 60% of their skin bacteria resistant to antibiotics!

To “escape” the contamination with bacteria resistant to antibiotics, limit the stay in a hospital to the shortest possible!

I. Staphylococcus AureusII. MethicillinIII. Clinical relevanceIV. Preventive Strategies

Staphylococcus – The Variants

Two types of staphylococcus: (related to colour in Agar medium)

• White pigmented type „Staphylococcus pyogenes albus“ spheric, clusters, most frequent skin bacterium, gram-positive, low plasmacoagulase-activity, (present in 30% of all clean orthopedic operation wounds all without complications!)

not dangerous in this configuration relevant mainly in operations of joints

• Yellow pigmented type „Staphylococcus pyogenes aureus“ (aureus (gr.) = golden)

high plasmacoagulase-activity high pathogenity and also high letality clinically a major problem!

Plasmacoagulase: activation-factor for prothrombin (analogous to Factor V & X or Ca2+ ) condensation of fibrin-network serve as protection of s.aureus bacteria (the bacteria become hidden under layer of fibrin and other plasma proteins)

Test for plasmacoagulase-activity needs at least 24 hours (too long for emergency situations); Clumping-Factor test (physiologically similar function of CFs and plasmacoag.) gives results within 1-2 min

Staphylococcus Aureus – Clinical Relevance

Importance of tests:

• Antibiotics are optimal only for a certain type / strain of bacteria; e.g the gram-behavior (gram-positive or -negative)

• MRSA: total determination of strain comprises - mecA-gene, - mecR- & mecI-gene, - femA-D gene- 10-12 other genetic

too time consuming for immediate treatment in urgent cases (up to 3-4 days)

Most important test for immediate treatment: gram-test

Staphylococcus Aureus – Characteristics

Microscopy / Culture:

• Bacterium, gram-positive (blue staining in Lugol-solution due to presence of mureinshell (peptidoglycans))

• Formation of clusters (staphyle (gr.) = bunch of grapes)

• Size: 0,8 – 1,2 μm• Nonmotile, no spore-formation

Growth:

• Fakultative anaerob• @ [10 ; 45]°C , in wide pH-Spectrum, also in high NaCl-

conc. (up to 10%)• 1 – 2 mm big & pigmented colonies

gram-negative gram-positive

S.aureus in clusters

Staphylococcus Aureus – Natural Resistance

Resistance to environ-mental influences Survival possible*

• High salt-resistance 7,5 – 10 % [NaCl]• High temperature-resistance 60°C / 15-30 min• High Resistance in environment:

- artificially contaminated plastic slab: > 7 days- matrices: > 70 days- cotton cloth: > 100 days- blankets: > 200 days

• High tolerance to dehydration:- contaminated, dried pus: ~ 70 days

* Microbial Survival in the Environent, Mitscherlich/Marth, 1984

Staphylococcus Aureus – Characteristics

Pathogenic factors:• Cellular Factors:- Protein A- Clumping-Factor- Mureinshell (Polysaccharides)

• Extracellular Factors:- Plasmacoagulase- Fibrinolysin- Hemolysin- Leukocidine- Hyaluronidase- Extracellular polymeric substances- Exfoliative-toxins- Toxic-Shock-Syndrome-toxins- Enzymes: lipases, nucleases, proteases- Bacteriocine

S. aureus after 1day-cultivation in a Petri dish

Strongly virulent (Virulence = capability to cause infections by prodution of bact. poisons

Staphylococcus Aureus – DiseasesI. Inflammatory & pyogenic diseases:

Details: http://www.infektionsnetz.at/InfektionenHautinfektionenBakterien.phtml (Roche AG)

• Carbuncle • Abscesses(collection of pus)(perifollicular, inflammated spot) (=group of furuncles, with deep purulent inflammation)

• Furuncle

Staphylococcus Aureus – Diseases• Emphysem • Parotitis • Pneumonia

(=loss of elastic recoil of lungs and following collapse of pulmon. bronchioles & alveoli)

Staphylococcus Aureus – Diseases• Mastoiditis• Otitis Media • Osteomyelitis

• Endocaditis

(acute or chronic) (might arise from otitis media) (Interesting: http://osteomyelitis.stanford.edu/pages/case06.html)

Sono + Doppler

• Sepsis

Staphylococcus Aureus – Diseases

II. Toxinmediated Diseases:

• Toxic Shock Syndrome (TSS): high fever, low blood pressure, confusion, coma, mulit-organ failure, death characteristic rash ressembles sunburn & can involve any region of the

body (lips, mouth, eyes, palm, soles) desquamation occurs after 10-14 days

• Staphylococcal Scalded Skin Syndrome (SSSS) (Dermatitis exfoliativa)

itching, lethargy, fever, hypothermia detach of epidermis from dermis due to exotoxins A + B fluid filled blisters (thin walled easily rupture) Ritter‘s Disease of the Newborn most severe form of SSSS

• Nutritional intoxication nausea, cramps, vomiting, diarrhoe, hallucinations, …

Staphylococcus Aureus – Misc. information

• Transmission pathways:- endogenously (S.aureus is spread throughout the infected pacient‘s body by body fluids; are

able to overcome bbb or bmb by impairement of these structures)- exogenously (e.g. contact with contaminated hands, skin, instruments)

• Strong adherence to synthetic surfaces (development of „disinfective synthetics“ surfaces that prevent adherence)

• Resistant to many environmental factors

• Colonisation of skin and mucosa (colonisation infection)- 10 – 40 % of healthy population (nose, pharynx, perineum)- 45 – 65 (80) % of clinical personal (62% vestibulum nasi, 5 % on hands)

• Great importance in nosokomial infections (secondary infections)

Staphylococcus Aureus – Misc. information

• Multiresistance (insensitivity to more than one class of antibiotics) very narrow variety of treatment pathogen-specific therapy, Anti-biogramm

• High incidence with growing tendency (28 103 cases*)

• Significantly increased mortality for Sepsis (1108 avoidable deaths*)

• Very cost intensive (427 Mio. €*)- 1 MRSA-colonisation 1647,94 €*- 1 MRSA-infection up to 14 360 $*

• Escalating situation (Spain, Italy, France, GB, Japan & USA almost uncontrollable) world-wide problem *Data related to Germany, 2005; Source: Martin

Wernitz, Klinikum Friedrichshain, Berlin

Methicillin – Discovery of Antibiotics

Timetable• 1928: Discovery of Penicillin

• After 1940: General use of Penicillin

• 1944: Resistance to Penicillin

Remark: before the discovery of antibiotics infections with S.aureus were in 90% of all cases lethal! („preantibiotic stage“)

Alexander Flemming, St.Mary‘s Hospital, London

Penicillin saved many lives during 2nd World War

Methicillin – New Type of Antibiotics

• Beecham, 1959: development of penicillinase- resistant Penicillin

Methicillin optimally workes/ed against bacteria, that produce enzymes for inactivation of antibiotics β-lactam-ring is stearically blocked, so penicillin-ases are hardly able to bind it instable in acidic environment (parenterally applied) subgroup with narrower field of treatment optimal: grampositive & β-lactamresistant bact. today‘s derivatives used: Oxacillin, Dicloxacillin, Flucloxacillin

Chemical stucture of Methicillin; β –lactam-ring is in the centre!

Methicillin – Discovery of Antibiotics

Timetable• 1928: Discovery of Penicillin

• After 1940: General use of Penicillin• 1944: Resistance to Penicillin

• 1959: Discovery of penicillinase-resistant Penicillins• 1961: resistance to penicillinase-resistant Penicillins

Methicillin Resistant Staphylococcus Aureus – MRSA –

Background• Synonym: Oxacillin-resistant S.aureus (ORSA) ( in laboratory tests mainly

search for oxacillin (comprises resistance to methicillin))• „Multi-resistant S.aureus“ (commonly for resistances for other non-β-lactam-

antibiotics• History:

– 1959: Introduction Methicillin– 1961: First discovery of MRSA

• Global distribution• Increasing significance as a pathogen for nosokomial infections

– Percentage of all S.aureus isolates in Germany: 22,6 %

• Some MRSA-strains: increased capability for epidemic spreading („epidemic Virulence“)

• Quick colonisation of contact persons (patients)

MRSA – Development in Germany

MRSE – Development in Germany

Development of Penicillin-Resistance

Methicillin – Resistancemechanism

Resistencemechanism• Mutations in mecA-Gene• Structural different Penicillin-Binding-Protein (PBP 2 PBP 2a)• Small affinity for Methicillin/Oxacillin/β-lactam-antibiotics• Cross-resistance to all β-lactam-antibiotics (including Cephalosporines &

Carbapenemes

Staphylococcus Aureus – Genetic Background of Methicillin-Resistancy

Normal procedure: β-Lactam-antibiotics (ABs) bound stable to the active centre of a PBP (Penicillin-Binding-Protein) disturb the synthesis of the cellmembrane stop of bacterial growth autolysis / apoptosis

PBPs are membrane bound enzymes, responsible for the formation of peptidoglycans of the cellcoat//wall normal: PBPs 1-4 (sorted by weight)

Mutations of PBP-determining genetic areas give raise to new PBP structure: PBP 2a is formed (coded by mecA-gene, significant lower affinity to β-Lactam-antibiotics); takes over the physiologic function of PBPs 1-4 AB ineffective bacterial wall remains intact

such resistant bacteria produce an enzyme breaking down attached ABs, the β-Lactamase „intrinsic resistance“

• In case of MRSA a total determination of strain comprises:1. mecA-gene (78 kDa, most important PBP 2a)2. mecR- & mecI-gene (regulatory genes, repressor-fct. on transcription of mecA-gene!)3. femA-D gene ( ‘‘ ‘‘ )4. auxiliary genes (10-12 other genetic elements that influence the expression of PBPs )

PBP 2a is major genetic feature for MRSA-Detection !!!

MRSA – Resistant Phenotypes in Germany

Epidemic Strain 2002* 2003* 2004**

Northern Germany (general) ST 247 0,4 % 0,1 % 0,1 %

Southern Germany (general) ST 228 15,2 % 13,8 % 11,8 %

Hannover ST 254 0,7 % 0,5 % 0,3 %

Rhein-Hessen-MRSA ST 5 23,0 % 24,5 % 26,5 %

Berlin ST 45 18,2 % 13,8 % 10,2 %

Barnim ST 22 28,0 % 29,0 % 35,3 %

others 14,0 % 18,1 % 15,5 %

Epidemic MRSA in german hospitals (Resistancephenotypes)

*Epid. Bull. 42/2004

** Epid. Bull. 41/2005

*Epid. Bull. 41/2004

MRSA-strains, localisation,Germany, 2004*

MRSA – Analysis of Resistance to different Antibiotics, Erlangen, 2004

Resistance of MRSA to tested antibiotics• Penicillin 100 %• Ampicillin 100 %• Oxacillin 100 %• Amoxicillin/Clavulansäure 100 %• Cefazolin 100 %• Cefotiam 100 %• Imipenem 100%• Ciprofloxacin 94 %• Erythromycin 89 %• Clindamycin 89 %• Gentamicin 33 %• Cotrimoxazol 4 %• Fosfomycin 3 %• Vancomycin( Linozolin) 0 %

Clinical Relevance – Other Antibiotic Resistances

Abbreviations• MSSA methicillin-sensitive S.aureus• MRSA methicillin-resistant S.aureus• VISA vancomycin-intermediate sensitive S.aureus• GISA glycopeptid-intermediate sensitive S.aureus• VRSA vancomycin-resistant S.aureus

Timetable• 1956: Discovery Vancomycin• 1958: Introduction of Vancomycin• 1996: Discovery of VISA• 2002: Discovery of VRSA actual „reserve-antibiotic“ is Linozolid (last

line of defence); only in severe cases development of resistance must be restricted!

Clinical Relevance – MRSA on ICUs

Types of Infections associated with MRSA (Jan/2003 – Dec/2003, acc. to KISS)*

Type of Infection Percentage________________________________________Pneumonia 48 %Bronchitis 10 %Sepsis 10%Postoperative woundinfections 18%Skininfections 5 %Infections of urinary tract 3 %others 6 %

*Epid. Bull 41/2004

Clinical Relevance – Nosokomial Infections

Frequency of S.aureus for nosokomial infections in Germany (KISS*)

1. Data for Intensive Care Units, Jan/1997 – Dec/2003**• Pneumonia assoc. to artificial ventilation: 24% rank 1• Bronchitis assoc. to artificial ventilation: 26% rank 1• CVF-assoc. Sepsis: 15% rank2

2. Data of postoperative woundinfections, Jan/1997 – Dec/2002***• Obstetrics: 19% rank1• Vascular surgery: 39% rank1• Heart surgery: 40% rank1• Traumatology/Orthopaedics 40% rank1• General-/Abdominal surgery 12% rank3

* KISS = Krankenhaus-Infektions-Surveillance-System ** Epidemiologisches Bulletin 41/2004 *** Epidemiologisches Bulletin 36/2003

Clinical Relevance – MRSA on ICUs*

according to KISS**• 1997: MRSA-percentage of all S.aureus: 8 %• 2003: MRSA-percentage of all S.aureus: 30 %

• Primary S.aureus – Sepsis- MRSA-percentage of all S.aureus: 37,8 %

• Nosokomial pneumonia- MRSA-percentage of all S.aureus: 21,5 %

*Epid. Bull. 5/2005**KISS = Krankenhaus Infektions Surveillance System

Staphylococcus Aureus – Situation in Europe – 2004* –

Staphylococcus aureus: proportion of invasive isolates resistant to oxacillin (equivalents) in 2004

* European Antibiotic Resistance Surveillance System (EARSS), Annual Report 2004

Staphylococcus Aureus – Situation in USA – Summary of 1993 - 2005*

MRSA – Preventive Strategies

• Identification, aquisition, evaluation

• Implementation of suitable hygienic sanctions

• Rehabilitation of MRSA-carriers

• Controlled & reasonable use of antibiotics

MRSA – Preventive Strategies

Identification, aquisition, evaluation• § 23 IfSG: Nosokomial Infections, Resistances

„(1) Chiefs of hospitals and facilities for ambulant operations are committed, to register and evaluate the designated nosokomial infections and the appearance of pathogenes with special resistances and multiresistances in a continuous transcript.

The records according to article (1) have to be stored for at least ten years.At request of the responsible public health department access has to be granted.“

According to law it is a duty to record all data on nosokomial and epidemic infections. This data is evaluated in each hospital; the main centre in germany for disease control is the Robert-Koch-Institute (RKI).

No warranty for the translation ;)

MRSA – Preventive Strategies

Implementation of hygienic sanctions*• Recommendation of the Commission for hospital hygiene and Infectionprevention,

e.g. relating to:- Accomodation- Protection against contamination- Disinfection- Patient-transfers

• Realisation can differ from hospital to hospital (but minimum standard must always be achieved)

Rehabilitation of MRSA-carriers• Antispetic / disinfective measures• Sometimes in combination with antibiotic measures Good results in countries with low MRSA-prevalence Result dependant on pre-existing defects

MRSA – Preventive Strategies

Controlled use of antibiotics

• Therapy only at Infection NOT in case of a colonisation

• Therapy (usually): Vancomycin (+ Combinative Partner Antibiotics)

decreased incidence of resistant subpopulations

• Decrease the pressure of selection (resistance-formation)

Sources

• www.wikipedia.com / .de• Google-picture-pool• Robert-Koch-Institut (www.rki.de) MRSA + S. aureus• Epidemiologisches Bulletin (RKI) 36/03, 41/04, 41/05• www.infektionsnetz.de (Roche AG)

• Dr. Bernd Kunz, Klinikum Erlangen• Martin Wernitz, Klinikum Friedrichshain, Berlin