S.aureus

1. Juanita Escobar Martínez
Rodrigo Herrera Caro
III Semestre
PATRÓN DE RESISTENCIA
ANTIBIÓTICA -
STAPHYLOCOCCUS AUREUS

3. INTRODUCTION
Staphylococcus:
• Bacteria  Gram-positive cocci formed in grape-like clusters.
• Facultative anaerobes.
• Resistant to hostile conditions.
• Rapid development.
• Ferments carbohydrates and produce pigments (white
• to yellow).
• Catalase positive.
• At least 40 species  S. epidermidis, S. saprophyticus, S.
aureus.
• Commensal  nostrils, skin and mucous membranes.

4. INTRODUCTION
S. aureus:
• "Golden staph" or Oro staphira.
• Stationary and non-spore.
• Capsule  slime or mucoid (polysaccharid).
• Coagulase positive.
• Pathogen  polymorphic mucocutaneous infections, shock toxic syndromes,
toxic food-borne infections, nosocomial infections.

5. INTRODUCTION
Product Effect
Capsule Inhibits phagocytosis
Coagulase May prevent the progression of
leukocytes in the infected area produce
clots in neighboring capillaries
Exfoliatin Separates the layers of the epidermis,
causing Scalded skin Syndrome
Hyaluronidase Decomposes hyaluronic acid of
tissues and promotes spread of
infection
Leukocidin Destroys leukocytes producing holes in
the cytoplasmic membrane
Lipase Descomposes fats hydrolyzing the
bond between glycerol and fatty acids
Proteases Degrades collagen and other tissue
proteins

6. INTRODUCTION
Product Effect
A Protein Binds to the Fc portion of the antibody
inhibiting phagocytosis
Septic shock
Syndrome Toxin
Causes rash, diarrhea and shock
Clumping factor Binds bacteria to fibrin, fibrinogen and
plastic elements
Fibronectin
binding protein
Binds bacteria to the acellular tissue
substance, epithelium, endothelium, blood
clots, plastic elements to stay.
α, β, γ and δ toxins Dermonecrotic effect
Leukocidin Destroys neutrophils or cause release of
their enzymes
Enterotoxins Superantigens. Cause food poisoning if
they are ingested
TSST-1 Superantigen. If they are systemic causes
toxic shock

7. INTRODUCTION
MRSA resistance:
•Methicillin-resistant Staphylococcus aureus.
•SCCmec  mecA, psm-mec, ccrA and ccrB genes.
•Strains, ACME, mecA.
•mecA  encodes PBP2a.
•HA-MRSA and CA-MRSA.
•Any strain of S. aureus that has developed resistance to beta-
lactam antibiotics (penicillins and cephalosporins).

8. OBJECTIVE
“To detect antibiotic
resistance pattern,
MRSA, SCCmec types
and accessory gene
regulator (agr)
groups among
isolates of S. aureus.”

9. MÉTODOS
Aislamiento de bacterias :
• Funda
Prueba Fundamento Objetivo Imagen
Catalasa Descomposición del
peróxido de hidrógeno
Distinguir de especies de
Streptococcus,
Enterococcus y
Lactococcus.
Coagulasa Reacciona con
protrombina  fibrinógeno
se convierte en fibrina
Diferenciar de
Staphylococcus
coagulasa- negativa
MSA Alta concentración
de NaCl, manitol y rojo de
fenol (pH)
Identificar
Staphylococcus
coagulasa-positivos
Test
Dnasa
Agar
Detección de enzimas
desoxirribonucleasas.
Diferenciación entre
especies de
Staphylococcus

10. MÉTODOS
Prueba de susceptibilidad antibiótica
• AST  Método de Kirby Bauer.
• Fundamento  determina la sensibilidad de
un agente microbiano frente a un antibiótico
o quimioterápico.
• Antibiograma o prueba de susceptibilidad
bacteriana frente a drogas específicas.
• Objetivo  determinar a cuál de los
antibióticos es resistente la bacteria.
• Sensible (S), Intermedio o Moderadamente
sensible (I) y Resistente (R).

11. MÉTODOS
Extracción de DNA genómico
1. Lisis de bacterias Gram-positivas  lisostafina.
2. Degradación del RNA  opcional.
3. Precipitación de proteínas  ácido acético.
4. Precipitación de DNA  isopropanol.
5. Almacenamiento en TE  buffer ácido etilendiaminotetraacético (EDTA).
6. Marcación con FISH  hibridación fluorescente in situ.


12. MÉTODOS
PCR
• Obtención de muchas copias de una fragmento de DNA particular 
amplificación de un fragmento de DNA.
• Fundamento  propiedad natural de los ADN polimerasas para replicar
hebras de ADN  ciclos de altas y bajas temperaturas alternadas 
separar hebras de ADN recién formadas  dejar que las hebras de ADN
vuelvan a unirse para poder duplicarlas nuevamente.
• Sensibilidad, Especificidad, Eficiencia,
Fidelidad.
• Desnaturalización, alineamiento,
extensión, elongación final, conservación.

13. SCCmec III
325 pb
280pb94,2%
SCCmec V
5,8%
RESULTADOS

14. RESULTADOS
Tetraciclina Eritromicina
ClindamicinaTrimetoprim
Gentamicina
Ciprofloxacina
Amoxicilina

15. RESULTADOS

16. Author Conclusion Yes or not
Shittu All of the isolates were susceptible to vancomycin and
linezolid.
YES
Sharma All clinical isolates were susceptible to vancomycin YES
Japoni 74.3% of isolates in south of Iran were SCCmec type
III
YES
Ho 91.6% of clinical isolates belonged to arg group I YES
DISCUSSION

17. • Staphylococcus aureus has particular ways of
manifestations and resistances that could complicate a
infection´s treatment.
• Strain type is determinant in the expression of resistant
genes that are a challenge when a treatment will be
developed.
CONCLUSIONS

18. • Although there are two antibiotics which can treat the
infection by S. aureus could cause a resistance because
of chronic use.
• The knowledge of the kind of Strain that cause the
infection is important to guide a treatment plan, avoiding
the use of ineffective antibiotics.
CONCLUSIONS

21. • COSSART, Pascale; BOQUET, Patrice; NORMARK,
Staffan; RAPPUOLI, Rino. Cellular Microbiology. 2nd
edition. ASM Press. Washington, DC. 2005. Pags 22-
23.
• NESTER, Eugene; ANDERSON, Denise; ROBERTS,
C. Evans Jr; NESTER, Martha. Microbiología humana.
5ta edición (traducción). Manual Moderno. México.
2007. Pags 317-318, 562-563, 582-585, 613-614, 912-
913.
BIBLIOGRAFÍA