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Strep and entero
- 2. Group B Streptococcus Introduction Pathogenisis Laboratory diagnosis Enterococcus Introduction Clinical mainifestation Vancomycin resistance Enterococci 2 Contents
- 3. 3
- 4. Introduction Gram-positive cocci Chains Encapsulated Non-motile Facultative anaerobes Lactic acid production Multiple nutritional requirements 1-4 mm diameter, grey- white, flat, mucoid Selective Broth Media (SBM) or Lim broth 4
- 5. 5 • Divided into the following serotypes based on capsular polysacchride. types Ia, Ib,II and III through VII. • All serotypes can cause infections in newborns but Ia,II,III,V account for 90%. • Late onset dx and early-onset meningitis is due to type III.
- 6. 6 β-hemolysis RBCs surrounding the colony are completely lysed “Hemolysin" toxins Narrow hemolysis zones CAMP factor enhances hemolysis Carbohydrate Antigens (C substance) Lancefield Group B Group specific antigen Polysaccharide Capsule Serotypes 150 oligosaccharide subunits with mono-, di-, tri- side chains Ia, Ib, II-VIII III and V completely sequenced Classification
- 7. 7 Epidemiology Approx. 10%-35% of pregnant women are asymptomatic carriers of GBS in the genital and Gastro Intestinal tract. At birth 1 in 2 infants born to colonized mothers are colonized. 98% of colonized infants are without symptoms, but 1%-2% developed GBS. Nearly 50% of sexual partners of colonized women are colonized themselves.
- 8. 8 • Incidence rate of 0.2 – 3.7/1000 live births. • Mortality rate of 5-15/1000 live births. • More recent surveillance shows a decrease in Incident rate to 0.8 per 1000 live births-reflection of use of maternal antibiotic prophylaxis • Direct cost of treating neonate with proven GBS – 300 million dollars/year.
- 9. 9 Virulence Factor GBS Surface Polysaccharide Capsule Antiphagocytic properties Sialic acid residues on capsule inhibit the binding of active C3 component of complement to the cell surface blocking activation of the alternative pathway Transplacental passage of type-specific anti- capsular IgG antibody from mother to infant is an important protective factor against invasive disease
- 10. 10 GBS β-hemolysin Cytotoxic to pulmonary epithelial and endothelial cells Pulmonary injury and alveolar protein exudate in early-onset pneumonia Activity is blocked by surfactant phospholipid Increased risk of premature, surfactant-deficient neonates for severe pneumonia Induces cytokine release and nitric oxide production in macrophages Stimulate elements of the sepsis cascade
- 11. 11 C5a-peptidase Cleaves and inactivates the complement-derived neutrophil chemoattractant C5a C5a-peptidase-deficient mutants are more rapidly cleared from the lungs of infected animals when compared to the isogenic wild- type strain
- 13. 13 What does group B Streptococcus do? Colonisation Asymptomatic and intermittent Intestinal (<30% of adults) Vaginal (<25% of women) Infection Newborn babies Adults: the elderly, pregnant/postpartum women, others with underlying disease IN MOTHER LOWER GENITAL TRACT ANORECTUM URINARY TRACT IN NEONATES EXTERNAL EAR (IN FIRST 24 H ) ANTERIOR NARES, THROAT ANORECTUM UMBILICUS
- 14. 14 Risk Factors for Colonization Heavily colonized mothers Mothers younger than 20 African Americans Lower socioeconomic groups PROM Prolonged labor Maternal Chorioamnionitis Previous delivery with GBS disease
- 15. 15 Early onset vs. Late onset Occurs in 1st week. Usually before 72hrs Pathophysiology. -Colonization. -Immature host defense mechanism particularly among low birth weight infants. 1week to 6months. Usually at 3-4 weeks. Pathophysiology. - Alteration of the mucosa barrier by a viral respiratory tract infection. - weakened host defense - decrease amount of maternal antibodies.
- 16. 16 Early onset vs. Late onset Transmission: - aquired through vertical transmission. - during passage through a colonized birth canal. Transmission: - aquired through horizontal transmission: -nurseries -hospital personnel -community
- 17. 17 Early onset vs. Late onset Clinical Manifestation - Pneumonia - respiratory distress - cyanosis, - hypoxaemia - apnea - Shock - Poor feeding -Less often meningitis - Abnormal temprature Clinical manifestation: Occult bacteremia Meningitis Ventriculitis other focal infections, e.g. septic arthritis, osteomyelitis.
- 18. 18 Laboratory Diagnosis Colony morphology Grayish-white, mucoid, creamy, narrow zone of b- hemolysis Presumptive Identification tests Catalase-negative Bacitracin- resistant
- 19. 19 Presumptive identification tests Bile-esculin- hydrolysis– negative Does not grow in 6.5% NaCl CAMP-test– positive Hippurate test- positive Latex agglutination test
- 20. 20 “Gold Standard” test for GBS carriage When? 35-37 weeks of pregnancy Where & who? Low vagina & anorectal swab/s (no speculum) Health care professional or pregnant woman What culture method? Enriched Culture Medium (ECM) - 24-48 hours to grow HPA BSOP58 Processing Swabs for GBS carriage
- 21. Pigmented Broth — Positive Result Positive color change Photo courtesy of Dr. Lesley McGee, CDC Inoculate into enrichment broth Non-pigmented broth Lim broth, TransVag broth TransVag broth should be supplemented with 5% defibrinated sheep blood OR Pigmented broth StrepB carrot broth, Granada biphasic broth
- 22. 22 Antibiotic Recommendations —Intrapartum Prophylaxis Standard: Penicillin (PCN) or ampicillin Alternatives: • PCN-allergic and low risk for anaphylaxis: cefazolin • PCN-allergic but high risk for anaphylaxis depends on susceptibility to clindamycin & erythromycin – If susceptible to clindamycin (including lack of inducible resistance) clindamycin – If unknown or not susceptiblevancomycin
- 23. Introduction to Enterococci Enterococci are gram- positive cocci which often occur in pairs (diplococci) Two species are common commensal organisms in the intestines of humans: E. faecalis and E. faecium 23
- 24. Characters of Enterococci Gram(+) , Catalase(－) Cocci Can grow in media : 6.5% sodium chloride E. faecalis and E. faecium (90%) Part of the normal bowel flora. the prominent cause of nosocomial infections. 24
- 25. Habitat of Enterococci Enterococci normally inhabit the bowel. They are found in the intestine of nearly all animals, from cockroaches to humans. Enterococci are readily recovered outdoors from vegetation and surface water In humans, typical concentrations of enterococci in stool are up to 108 CFU per gram . 25
- 26. normal flora of the intestinal tract. Enterococcus faecalis frequently causes infections within the peritoneal cavity especially following penetrating trauma such as gunshot wounds and surgical wounds urinary tract infections prostate infections infections of damaged or compromised skin, such as diabetic or decubitus ulcers, burns, and surgical wounds. Other opportunistic fecal streptococci include E. faecium and E. durans. Growing Importance of Enterococci 26
- 27. Prominent Cause of Nosocomial Infections The enterococci have become the second most common bacterium isolated from nosocomial urinary and wound infections, and the third most common cause of nosocomial bacteremia. Furthermore, the enterococci are among the most antibiotic resistant of all bacteria, with some isolates resistant to all known antibiotics 27
- 28. Clinical Manifestation Infections with VRE do not differ from other enterococcal infections other than in their therapy. The most common sites of infection : The urinary tract and bloodstream. In addition, enterococci may cause endocarditis due to their ability to adhere to heart valves. They rarely cause respiratory tract infections. 28
- 29. 29 Identification PYR-positive which differentiates them from S.bovis Bile esculin agar test positive
- 30. 30
- 31. Glycopeptides Mechanism of Action Vancomycin and teicoplanin inhibit cell wall synthesis by forming complexes with peptidyl-D- alanyl-D-alanine termininal vanA and vanB resistance phenotypes are associated with the acquisition of gene clusters that lead to the production of peptidoglycan ending in D- alanyl-D-lactate 31
- 32. Vancomycin-resistant enterococci (VRE), first reported in Europe in 1988, are emerging as a global threat to public health . The incidence of VRE infection and colonization among hospitalized patients has increased rapidly in the last few years. From 1989, the year VRE was first identified in the United States, through 1993. Infection with VRE may be associated with increased mortality , and no effective antimicrobial therapy is available for many VRE . Vancomycin Resistance Increases Morbidity and Mortality 32
- 33. VRE Epidemiology Found world-wide, but rates vary greatly Hospital outbreaks often involve clonal spread Also seen in nursing homes and long term care facilities First described in Europe Primarily a nosocomial pathogen Alarming increase from 1989 to 1993 intensive care units & teaching hospitals 33
- 34. vanA and vanB Phenotypes vanA vanB Vancomycin MIC >64 4-1024 Teicoplanin MIC 16-512 0.5 Usual species faecium, faecalis faecium, faecalis Acquired Yes Yes Transferable Yes Yes
- 35. vanC, vanD, and vanE Phenotypes vanC vanD vanE Vancomycin MIC 2-32 128 16 Teicoplanin MIC 0.5 4.0 0.5 Usual species gallinarum, casseliflavis, flavescens faecium faecalis Acquired No Yes Yes Transferable No No No
- 36. MOLECULAR BASIS OF VANCOMYCIN RESISTNACE
- 37. Result Spreading Resistance Enterococci that acquire the vanA phenotype are highly resistant to vancomycin and to teicoplanin Enterococci can pass the vanA gene cluster to S. aureus E. faecalis rather tan E. faecium (so far) 37
- 38. Urinary tract infection (most common) Intra-abdominal and pelvic infection (also common) Surgical wound infection Bacteremia—bacteria in the blood Endocarditis —infection of the inner surface of the heart muscles and valves Neonatal sepsis —bacteria in the blood, occurring in infants Meningitis —infection of the membranes that surround the brain and spinal cord Infections Caused by Vancomycin Resistant Enterococci 38
- 39. 39
- 40. Detection of Vancomycin Resistance Susceptibility to vancomycin can be performed by Kirby-Bauer Disc Diffusion Method on Mueller Hinton Agar by using 30µg vancomycin disc Vancomycin resistance can also be determined by Vancomycin agar screen method using 6µg/ml of vancomycin incorporated in Brain Heart Infusion (BHI) agar. 40
- 41. Minimum Inhibitory Concentration (MIC) of all the isolates were done by Macro broth dilution method, using dilutions of vancomycin ranging from 2 µg/ml to 512 µg/ml. 41
- 42. Drug Resistance can be Established by E-Test 42
- 43. *Chromogenic Methods in Diagnosis of VRE Chromogenic medium for the detection of Vancomycin Resistant Enterococcus (VRE) E. faecalis and E. faecium * Colorex™ Prepared Chromogenic Media by BioMed Diagnostics 43
- 44. Genotypic Detection of VRE Rapid detection of vancomycin resistance by polymerase chain reaction (PCR). useful in epidemiologic studies PCR can`t be performed directly on clinical specimens. 44
- 45. Control and Prevention Limiting the use of certain broad spectrum antibiotics may also lead to a decrease in the rates of VRE colonization and infection. One study suggested that reduction of third- generation cephalosporins with the substitution of piperacillin/tazobactam could reduce the incidence of VRE in an intensive care unit setting Hospital Infection Control Practices Advisory Committee (HICPAC). Recommendations for preventing the spread of vancomycin resistance. Infect Control Hosp Epidemiol 1995; 16:105 45
- 46. The CDC has published recommendations for preventing the spread of vancomycin resistance Prudent use of vancomycin Education of hospital staff regarding the problem Rapid and accurate identification of VRE in the microbiology laboratory Aggressive infection control measures utilizing contact isolation and cohorting where necessary to prevent person-to-person transmission Hospital Infection Control Practices Advisory Committee (HICPAC). Recommendations for preventing the spread of vancomycin resistance. Infect Control Hosp Epidemiol 1995; 16:105 46
- 47. 47 Hand Washing can Reduce the Spread of VRE
- 48. Ananthanarayan & paniker`s , Textbook of Microbiology Koneman`s Color Atlas and Textbook of Diagnostic Microbilogy Topley`s and Wilson Textbook of Microbiolgy http://www.gbss.org.uk/filepool/BSOP58.pdf http://www.cdc.gov/groupbstrep References 48
Editor's Notes
- This is a close-up picture of a group B Streptococcus (GBS) enriched in pigmented enrichment broth (StrepB carrot broth). The tube on the right shows a positive color change, indicating the presence of beta-hemolytic Group B strep.