MOD 14 Bacterial Infections of the CVS and Lymphatics 1 PDF

MICROBIOLOGY AND PARASITOLOGY 11/06/2024. MOD 14: BACTERIAL INFECTIONS OF THE CVS AND LYMPHATICS 1...

MICROBIOLOGY AND PARASITOLOGY 11/06/2024. MOD 14: BACTERIAL INFECTIONS OF THE CVS AND LYMPHATICS 1 Dr. Carlo Gabriel R. Macapagal MD Trans Group/s: 2A, 3A OUTLINE I. DEFINITIONS 1. BACTEREMIA I. Definitions Presence of bacteria in the blood. II. Staphylococci Bacteria usually enter the bloodstream through the A. Staphylococcus aureus lymphatic system. B. Staphylococcus epidermidis When organisms multiply at a local infection site and are then drained by the lymphatics to reach the C. Laboratory Diagnosis bloodstream, it is referred to as bacteremia. D. Treatment Common portals of bacterial entry include the E. Prevention gastrointestinal tract, respiratory tract, and other III. Streptococci sites. Bacteria may also gain access through surgical wound A. Group A Streptococci (Streptococcus pyogenes) infections, abscesses, the biliary tract, and 1. General Characteristics miscellaneous sites. 2. Virulence Factors and Its Associated Diseases In most individuals, bacteria in the bloodstream are effectively and rapidly cleared by the 3. Streptococcus pyogenes - Endocarditis reticuloendothelial system. 4. Laboratory Diagnosis 5. Treatment 2. SEPTICEMIA/SEPSIS 6. Prevention Presence of bacteria and toxins in the blood. B. Viridans Streptococci This condition arises when bacteria or their toxins cause harm to the host. 1. General Characteristics Signs and symptoms of Septicemia 2. Virulence Factors and Its Associated Diseases ○ Fever 3. Viridans Streptococci - Endocarditis ○ Hypothermia 4. Laboratory Diagnosis ○ Chills ○ Hyperventilation 5. Differential Tests ○ Change in mental status 6. Treatment ○ Diarrhea 7. Prevention 3. SEPTIC SHOCK IV. Group D Streptococci A. Streptococcus bovis (Non-Enterococci) Complications of sepsis, including hypotension and organ failure 1. General Characteristics Mediated by cytokine production from activated 2. Laboratory Diagnosis mononuclear cells, such as tumor necrosis factor B. Enterococci (TNF) and interleukins. 1. General Characteristics Clinical Manifestations of Septic Shock: ○ Drop in blood pressure (hypotension) 2. Associated Diseases ○ Increase in heart rate (tachycardia) 3. Laboratory Diagnosis ○ Organ failure 4. Treatment 5. Prevention C. Enterococci & Non-Enterococci Comparison OBJECTIVES At the end of the lecture, the student must be able to: 1. Identify the etiologic agent based on the general characteristics and laboratory findings 2. Determine the associated clinical diseases, risk factors, and transmission of a specific etiologic agent 3. Identify the appropriate management and control measures for a given infectious agent Microbiology - Mod 14 Bacterial Infections of the CVS and Lymphatics 1 1 of 9 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited.  II. STAPHYLOCOCCI A. STAPHYLOCOCCUS AUREUS General characteristics: ○ Gram (+) cocci in clusters ○ Coagulase (+) ○ Facultative anaerobe ○ Part of the normal microbiota of the anterior nares, nasopharynx, perineal area, skin, and Vegetations colonizer of the mucosa. ○ Transmitted via person to person, fomites, and RISK FACTORS FOR THE DEVELOPMENT OF traumatic introduction (usually through surgical S. AUREUS ACUTE ENDOCARDITIS wound or microabrasion). 1 Persistent bacteremia 2 Implanted cardiac devices (pacemakers) 3 Prosthetic heart valves 4 Intravascular catheter 5 Pre-existing cardiac conditions 6 Diabetes mellitus 7 Hemodialysis B. STAPHYLOCOCCUS EPIDERMIDIS Gram (+) cocci in clusters Coagulase (-) Virulence Factors and Spectrum of Diseases of S. aureus Facultative anaerobes Normal flora of skin and mucous membranes Professor’s Notes: This figure shows that S. aureus has a Transmitted from person to person (nosocomial lot of virulence factors and associated diseases. However setting and during implantation of medical devices for this module, we will be focusing on Bacteremia and Endocarditis. 1. VIRULENCE FACTORS May be spread via the lymphatics or bloodstream from 1. Biofilm (or exopolysaccharide “slime” or slime layer) any focus of infections If bacteremia ensues, it may result in endocarditis. Its formation promotes protection from phagocytic systems (antiphagocytic) and adherence to plastic Risk Factors polymers. ○ Formed by Polysaccharide Intercellular Adhesin 1 Nasal colonization (PIA) found on staphylococcal cell surfaces. 2 Prosthetic devices 2. Exotoxins: Delta Toxin 3 Intravascular catheters Not discussed by the lecturer 4 Intravenous drug use 2. CLINICAL DISEASES (Spectrum of Diseases and Infections) Causes nosocomial infections, such as: 5 Immunocompromised state Most common cause of ACUTE ENDOCARDITIS nosocomial bacteremia 1 Bacteremia S.aureus causes an acute endocarditis which may Due to indwelling vascular rapidly develop. catheters ○ < 2 weeks Right-sided, tricuspid valve involvement is affected Most common cause of early among IV drug users. 2 Endocarditis prosthetic valve endocarditis Localized growth on native or prosthetic heart valves, Involving prosthetic cardiac valves called vegetations. ○ It consists of platelets, fibrin, inflammatory cells, 3 Intravenous At intravascular catheter sites; and entrapped organisms. catheter commonly leading to bacteremia After bacterial colonization, the surface will rapidly be infections covered with a protective layer of fibrin and platelets. 4 Ventricular shunt infections ○ This is a protective environment favorable for further bacterial multiplication. 5 Infections associated with CSF shunts, prosthetic joints, vascular grafts, Others post-surgical ocular infections, and bacteremia in neonates under intensive care Microbiology - Mod 14 🏠 Bacterial Infections of the CVS and Lymphatics 1 2 of 9 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited. 1. Bacteremia 3. COAGULASE TEST One of the most common causes of nosocomial Differentiates coagulase (+) S. aureus from other infections, particularly in surgical patients with staphylococci species indwelling medical devices or implants Coagulase is an enzyme needed to make blood clot May result in endocarditis 1 Slide coagulase test (+) result: presence of clumps 2. Endocarditis 2 Tube coagulase test (+) result: formation of clot Presents with localized growth or vegetations Occur after: ○ Cardiac valve replacement → early prosthetic valve Coagulase (+) Coagulase (-) endocarditis ○ Previously damaged valves → subacute Other Staphylococcus endocarditis S. aureus species including Recall: biofilm facilitates adherence to prosthetic S. epidermidis materials RISK FACTORS FOR S. EPIDERMIDIS ENDOCARDITIS 1 Prosthetic valves 2 Immunosuppression 3 Malignancy 4 Chemotherapy Slide and Tube Coagulase Test 5 Bone marrow transplantation 4. NOVOBIOCIN SUSCEPTIBILITY TEST S. aureus and S. epidermidis have a zone of inhibition → susceptible to novobiocin Novobiocin Susceptible Novobiocin Resistant S. aureus and other clinically relevant coagulase S. saprophyticus (-) staphylococci such as S. epidermidis Vegetations present in prosthetic valves C. LABORATORY DIAGNOSIS 1. GRAM STAIN Gram (+) cocci in clusters Novobiocin Susceptibility Test 2. CATALASE TEST 5. HEMOLYSIS S. aureus: Beta-hemolytic Catalase (+) Catalase (-) ○ Colonies are frequently surrounded by zones of Staphylococci Streptococci clear, beta-hemolysis S. epidermidis: Non-hemolytic Catalase Test Beta-hemolysis of S. aureus on BAP Microbiology - Mod 14 🏠 Bacterial Infections of the CVS and Lymphatics 1 3 of 9 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited. 6. MANNITOL SALT AGAR (MSA) TEST III. STREPTOCOCCI Contains a high concentration of salt, mannitol (sugar), and phenol red (pH indicator) A. GROUP A STREPTOCOCCI Streptococcus pyogenes MSA (+) MSA (-) 1. GENERAL CHARACTERISTICS S. aureus: ferments mannitol, and S. epidermidis: no Gram (+) cocci in chains produces yellow colonies with a fermentation, white Catalase (-) yellow halo due to the production of colonies with pink Facultative anaerobe acid that alters pH coloration Inhabits skin and upper respiratory tract of humans; carried on nasal, pharyngeal, and sometimes anal mucosa. Transmission via ○ Direct Contact: person to person ○ Indirect Contact: aerosolized droplets from coughs or sneezes 2. VIRULENCE FACTORS AND ITS ASSOCIATED DISEASES Mannitol Salt Agar Test Streptococcus also possesses virulence factors 7. BACITRACIN TEST Bacitracin-impregnated discs are placed on the surface VIRULENCE FACTORS OF S. PYOGENES of 5% sheep blood agar streaked in 3 directions with a cotton-tipped swab that has been dipped in bacterial Class I (M Protein) Class I or II (M Protein) suspension S. epidermidis has no zone of inhibition → resistant to Associated with rheumatic Associated with bacitracin fever glomerulonephritis 8. SUMMARY OF LABORATORY DIAGNOSIS Rheumatic fever is Acute glomerulonephritis is manifested as fever, characterized as edema, S. aureus S. epidermidis endocarditis, subcutaneous hypertension, hematuria, nodules, and polyarthritis and proteinuria Catalase (+) (-) Coagulase (+) (-) Usually follows Usually follows respiratory tract respiratory or cutaneous Hemolysis (BAP) Beta-hemolytic Non-hemolytic infections infections MSA (Mannitol + - Believed to be mediated by Mediated by Fermentation) (yellow colonies) (pink colonies) antibodies produced antigen-antibody against S. pyogenes M complexes that deposit in Phosphatase + - protein that cross-react glomeruli, causing damage with human heart tissues Lysostaphin Susceptible Resistant Novobiocin Susceptible Susceptible Note: Take note of the M protein when assessing for the virulence factors of Streptococcus pyogenes D. TREATMENT 3. STREPTOCOCCUS PYOGENES - ENDOCARDITIS 1 Removal of infected prosthesis or devices RISK FACTORS FOR S. PYOGENES ENDOCARDITIS 2 Methicillin-sensitive Nafcillin Staphylococcus Oxacillin 1 Surgery aureus Cefazolin 2 Trauma 3 Methicillin-resistant Staphylococcus Vancomycin (recommended) 3 Immunosuppression aureus (MRSA) 4 Malignancy 4 Daptomycin Alternatives Linezolid 5 IV drug use Quinupristin-Dalfopristin 6 Varicella infection E. PREVENTION Cleanliness, hand hygiene, and aseptic management of lesions. Application of topical antiseptics such as mupirocin to nasal or peripheral carriage sites Survey for anterior nares colonization in high-risk patients, such as those in intensive care units and in chronic care facilities. Microbiology - Mod 14 🏠 Bacterial Infections of the CVS and Lymphatics 1 4 of 9 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited. 4. LABORATORY DIAGNOSIS OF S. PYOGENES B. VIRIDANS STREPTOCOCCI 1. Gram Stain 1. GENERAL CHARACTERISTICS S. pyogenes appear as gram (+) cocci in chains Alpha-hemolytic, but may also be non-hemolytic Optochin resistant (uninhibited growth) Bile insoluble (colonies are not soluble in bile) Most prevalent members of the normal microbiota of the upper respiratory tract Classified into the following groups: S. mitis, S. sanguinis, S.anginosus, S. mutans, S. salivarius, and S. bovis 2. VIRULENCE FACTORS AND ITS ASSOCIATED DISEASES VIRULENCE FACTORS OF VIRIDANS STREPTOCOCCI Spectrum of Diseases and Virulence Factors Infections Gram Stain for Streptococcus pyogenes Generally Slowly evolving (sub-acute) considered to be endocarditis, particularly in 2. Blood Culture of low virulence patients with previously Beta hemolytic Production of damaged heart valves; ○ There is complete lysis of red cells around and extracellular Bacteremia and infections of under the colonies complex other sterile sites do occur in ○ These areas will appear lightened or yellow or polysaccharides immunocompromised transparent. (e.g., glucans and patients; dextrans) enhance Meningitis can develop in attachment to host patients suffering trauma or cell surfaces, such defects that allow upper as cardiac respiratory flora to gain endothelial cells or access to the central tooth surfaces in nervous system; the case of dental S. mutans plays a key role caries. in the development of dental caries Beta Hemolysis in Blood culture 3. VIRIDANS STREPTOCOCCI - ENDOCARDITIS 3. Bacitracin Sensitivity Test Usually subacute endocarditis often involves abnormal Presence of zone of inhibition surrounding bacitracin in valves (e.g. congenital deformities, rheumatic or the sheep agar plate shows positive result atherosclerotic lesions) ○ Bacitracin susceptible Clinical course is gradual but the disease is invariably fatal in untreated cases Risk factors: ○ Dental caries ○ Poor oral hygiene Can accidentally reach the bloodstream after dental extraction May cause late prosthetic valve endocarditis (+) Result of Bacitracin Sensitivity Test 5. TREATMENT OF S. PYOGENES Drug of choice: Penicillin Alternatives: Macrolides (e.g., Azithromycin, Erythromycin, and Clarithromycin) Vancomycin is reserved for penicillin-allergic patients with serious infections Viridans Streptococci - Endocarditis 6. PREVENTION OF S. PYOGENES Detection and early antimicrobial therapy of respiratory skin infections Lifetime chemoprophylaxis with penicillin, given either monthly (IM administration) or daily (oral administration) is recommended for patients with rheumatic heart disease to prevent the development of bacterial endocarditis on a damaged heart valve. Microbiology - Mod 14 🏠 Bacterial Infections of the CVS and Lymphatics 1 5 of 9 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited. 4. LABORATORY DIAGNOSIS OF VIRIDANS STREPTOCOCCI 3. Salt Tolerance Test No growth on 6.5% NaCl 1. Gram Stain Gram (+) cocci in chains Salt Tolerance Test 6. TREATMENT OF VIRIDANS STREPTOCOCCI Gram Stain of Viridans Streptococci Parenteral therapy with either penicillin G or 2. Blood Culture ceftriaxone with or without an aminoglycoside Vancomycin is used in cases of penicillin allergies and Alpha: Partial hemolysis beta-lactam resistance 7. PREVENTION OF VIRIDANS STREPTOCOCCI Maintenance of good oral health Antibiotic prophylaxis before dental procedures of patients who are high risk (with prosthetic heart valve or prior history of endocarditis) IV. GROUP D STREPTOCOCCI Blood Culture of Viridans Streptococci 5. DIFFERENTIAL TESTS FOR VIRIDANS STREPTOCOCCI Editor’s Notes: Based on Lancefield Classification which was published in 1950s, Group D Streptococci includes both 1. Optochin Susceptibility Test Non-Enterococci and Enterococci (the latter was still not known until 1984 when it was recognized as a separate genus from Optochin resistant Streptococci and named as Enterococci) [internet] There is no zone of inhibition around S. viridans. Based on the lecturer’s discussion, this portion should still be Therefore it is resistant to optochin. under the heading of Streptococci, however, to retain uniformity in the formatting (i.e., general characteristics, treatment, laboratory diagnosis, etc.) it was moved up in the hierarchy. Optochin Susceptible Optochin Resistant S. pneumoniae S. viridans A. STREPTOCOCCUS BOVIS (NON-ENTEROCOCCI) 1. GENERAL CHARACTERISTICS Associated with bacteremia and endocarditis in patients with significant biliary tract disease or colon pathology Treatment: IV penicillin G or ceftriaxone 2. LABORATORY DIAGNOSIS 1. L-Pyrrolidonyl-β-Naphthylamide (PYR) Test PYR (-) Optochin Test A qualitative procedure determining the ability of streptococci to enzymatically hydrolyze PYR 2. Bile Solubility Test ○ (+) Reaction: red color change ○ (-) Reaction: yellow (no color change) S. mitis does not show lysis in bile. Hence, it’s bile insoluble Bile Soluble = Lysis (+) Bile Insoluble = Lysis (-) S. pneumoniae S. mitis PYR (-) for Non-Enterococci Bile Insoluble Microbiology - Mod 14 🏠 Bacterial Infections of the CVS and Lymphatics 1 6 of 9 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited. 2. Bile Esculin Test Bile esculin (+) ○ Ability of the organism to hydrolyze esculin in the presence of bile ○ Esculin is converted to glucose and esculetin wherein the latter reacts with an iron salt in the medium forming an iron complex → dark brown or black color PYR Test indicating a positive result Bile esculin (+) for Non-enterococci NaCl showing good growth for Enterococci 3. Salt Tolerance Test No growth on 6.5% NaCl Positive Result for Bile Esculin Test 4. TREATMENT Salt Tolerance Test (-) for Non-enterococci Cell-wall active antibiotic (Ampicillin or vancomycin) B. ENTEROCOCCI with an aminoglycoside For Vancomycin-resistant infections, the following 1. GENERAL CHARACTERISTICS can be used as alternatives ○ Daptomycin Gram (+), catalase (-), and facultative anaerobic ○ Linezolid Oval-shaped and are arranged in pairs or short chains ○ Quinupristin-Dalfopristin Possess the Group D group-specific substance ○ Tigecycline Part of the normal enteric microbiota Out of at least 47 species of Enterococci, only less than 5. PREVENTION ⅓ are associated with disease in humans ○ Enterococcus faecalis and Enterococcus Careful and restrictive use of antibiotics faecium are most commonly isolated Implementation of infection-control practices to reduce the risk of colonization and/or infection with enterococci 2. ASSOCIATED DISEASES C. ENTEROCOCCI & NON-ENTEROCOCCI COMPARISON UTI – most common form of infections ○ Frequently associated with indwelling catheters, instrumentation, or structural abnormalities of the Test Enterococci Non-enterococci genitourinary tract Infections are acquired via person to person, access to PYR (+) (-) sterile sites, contaminated medical equipment Bile esculin (+) (+) Bacteremia and endocarditis are also common forms of enterococcal infections and are frequently associated Salt Tolerance with metastatic abscesses and high mortality rates Test (Growth on (+) (-) 6.5% NaCl) 3. LABORATORY DIAGNOSIS Usually non-hemolytic Optochin Optochin resistant ○ Occasionally α-hemolytic, or rarely β-hemolytic Susceptibility Optochin resistant Note: Optochin susceptibility for non-enterococci was not PYR (+) mentioned in the video lecture. Bile-esculin (+) Grows well in 6.5% NaCl REFERENCES Macapagal, C. (2024). Bacteria Associated with CVS & Lymphatics 1. Lecture Video Microbiology - Mod 14 🏠 Bacterial Infections of the CVS and Lymphatics 1 7 of 9 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited.  PRACTICE QUESTIONS Reminder: each individual is assigned to make two (2) practice questions each, with respective rationales. DISCLAIMER: Practice questions WERE NOT fact-checked and DID NOT undergo proofreading. Please be advised. You may comment on the specific question if you have any corrections. TITLE OF THE TOPIC QUESTION RATIONALE ANSWER Which of the following is NOT a common form of Enterococci are primarily associated with C infection caused by Enterococci? healthcare-associated infections, particularly in A. Urinary tract infections (UTIs) immunocompromised individuals or those with underlying B. Bacteremia medical conditions. While they can cause a variety of C. Pneumonia infections, pneumonia is not a common presentation. D. Endocarditis Enterococci are more frequently linked to: Urinary tract infections (UTIs): These are the most common type of enterococcal infection. Bacteremia: This occurs when enterococci enter the bloodstream, often from a site of infection like the urinary tract or a wound. Endocarditis: This is a serious infection of the heart valves. Which of the following tests is NOT typically used Optochin susceptibility is a test used to differentiate between D to identify Enterococci in the laboratory? Streptococcus pneumoniae and other alpha-hemolytic A. Gram stain streptococci. Enterococci are not alpha-hemolytic B. Catalase test streptococci, so this test is not relevant to their identification. C. Bile esculin test The other tests are commonly used to identify Enterococci: D. Optochin susceptibility test Gram stain: Enterococci are Gram-positive cocci. Catalase test: Enterococci are catalase-negative. Bile esculin test: Enterococci are bile-esculin positive. Microbiology - Mod 14 🏠 Bacterial Infections of the CVS and Lymphatics 1 8 of 9 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited.  ANNEX OVERVIEW OF STREPTOCOCCUS PYOGENES Virulence Factors Spectrum of Diseases and Infections Protein F mediates epithelial cell attachment (fibronectin binding); hyaluronic acid capsule inhibits phagocytosis; M protein is antiphagocytic (>100 serotypes). Produces several enzymes and hemolysins that contribute to tissue invasion and destruction, including Streptolysin O, Streptolysin S, streptokinase, DNase, and hyaluronidase. Acute pharyngitis, impetigo, cellulitis, erysipelas, necrotizing fasciitis, and myositis; bacteremia with potential for infection in various organs; pneumonia; scarlet fever; streptococcal toxic shock syndrome. Streptococcal pyrogenic exotoxins (SPEs) mediate the production of a rash (e.g., scarlet fever) or multisystem effects that may result in death. C5a peptidase destroys complement chemotactic factors. Cross-reactions of antibodies produced against streptococcal antigens can contribute to Rheumatic fever human heart disease. The deposition of antibody-streptococcal antigen complexes in the kidneys results in damage Acute post-streptococcal glomerulonephritis to the glomeruli. Microbiology - Mod 14 🏠 Bacterial Infections of the CVS and Lymphatics 1 9 of 9 The use of trans, practice questions, and evals ratio must be used discreetly and social media/public exposure of the aforementioned shall be strictly prohibited.