Anaerobic Bacteria PDF

 Anaerobic Bacteria  Spore-forming Clostridium spp.  Non-spore forming:  Gram positive cocci Gram negative cocci  Gram positive bacilli Gram negative bacilli  Colonization Resistance Endogenous microflora forms a complex ecological system which 1. Protects both aga...

 Anaerobic Bacteria  Spore-forming Clostridium spp.  Non-spore forming:  Gram positive cocci Gram negative cocci  Gram positive bacilli Gram negative bacilli  Colonization Resistance Endogenous microflora forms a complex ecological system which 1. Protects both against colonization of body surfaces with exogenous microorganisms 2. Overgrowth of endogenous and potentially pathogenic microorganisms.  Non-Spore-Forming Gram positive Bacteria  Gram Positive Cocci = Peptostreptococcus  Gram Positive Rods = Actinomyces Propionibacterium Mobiluncus Lactobacillus Eubacterium Bifidobacterium  Non-Spore-Forming Gram positive Bacteria  Peptostreptococcus Oro-pharynx  Actinomyces Oro-pharynx; Female Genital tract  Propionibacterium Skin; Oro-pharynx Mobiluncus Female genital tract Lactobacillus Female genital tract; GI tract  Non-Spore-Forming Gram positive Bacteria  Colonize the oral cavity, gastro-intestinal tract, genito- urinary system and skin  Peptostreptococcus - Reclassified into six genera  Causes mixed infections – often to tissues adjacent to its habitat  Mobiluncus; Lactobacillus: Opportunistic pathogens  Propionibacterium: Colonizes the skin - A cause of Acne vulgaris and skin abscess  Bifidobacterium; Eubacterium: Rarely cause infection  Actinomyces spp.  Grows slowly on culture  Forms delicate filamentous Gram Positive rods  Colonize upper respiratory tract, GI tract, GU system  Produce chronic slowly developing infections Actinomyces spp  Actinomyces israelii  Produce chronic slowly developing painless granulomatous lesion that becomes suppurative and forms abscesses connected by sinus tracts  Cervicofacial : Hard woody swelling – Pus containing sulfer granules (micro colonies of A. israelii)  Other sites: Thoracic, Abdominal, CNS, Pelvic (IUCD) Actinomycosis Management of Actinomycosis  Diagnosis:  Macroscopic appearance of discharge = Sulfur granules  Gram smear of Pus: Filamentous Gram positive bacilli  Culture onto Blood Agar  Incubate anaerobically at 37 C up to 7 – 10 days  Examine cultures  Identify by morphology  Pelvic Actinomycosis  Copper IUCD  After an extended period of time > 1 year --- change of vaginal microbial ecology  Inhibition of normal habitat Lactobacillus spp  it gets colonized by A. israelii ----  Pelvic Inflammatory Disease (PID)  Non-spore-Forming Anaerobic Gram Negative Bacteria  Gram Negative Cocci= Veillonella  Gram Negative Rods = Bacteroides Fusobacterium Prevotella Porphyromonas  Non-spore-Forming Anaerobic Gram Negative Bacteria  Bacteroides G.I. Tract (Colon) Fusobacterium Oro-pharynx; Female Genital tract Prevotella Oro-pharynx; F. Genital tract Porphyromonas Oro-pharynx; F. Genital tract  Non-Spore-Forming Gram negative Bacteria  Bacteroides fragilis = Pleomorphic, capsulated Gram negative rod  Growth stimulated by 20% bile  Resistant to Penicillin  Prevotella & Porphyromonas = Gram negative rods. Susceptible to bile  Fusobacterium = large Gram negative rod  Prevotella = Saccharolytic; Pigmented & non-pigmented  Porphyromonas = Asaccharolytic ; Pigmented  Bacteroides fragilis  Lipopolysaccharide has little endotoxic activity  Adheres to peritoneal surfaces because of capsule  Capsular polysaccharide is antiphagocytic  Succinic acid (product of metabolism) inhibits phagocytosis and intracellular killing  Catalase inactivates hydrogen peroxide  Superoxide dismutase inactivates free Oxygen radicle  Collaginase causes tissue damage  Heparinase cause intravascular thrombosis  Anaerobic Infections  Mixed aetiology: Including aerobic and anarobic bacteria Infection adjacent to a mucous surface Abscess formation OR Necrotizing infection Foul smelling Specimen often contains gas  Infections of the oral cavity  Peptostrptococcus spp., Prevotella spp., Porphyoromonas spp. & Fusobacterium spp.; Bacteroides fragilis In addition to Streptococcus spp.  Gingivitis & Periodontal Infections: Diseases involving the supporting structure of the teeth (periodontium)  Deep facial space infections:  Ludwig’s angina:  Infections involving sublingual, submaxillary and submandibular spaces Ludwig Angina Vincent’s Angina  Vincent’s Angina/Stomatitis  Fusobacterium fusiformis and Borellia vincentii  Acute necrotizing infection of the pharynx  Unilateral sore throat increasing over time  Gingivostomatitis (Trench mouth)  On Examination: Unilateral ulcer on one tonsil and submandibular lymphadenopathy  Diagnosis: Gentian violet-stained smear of pharyngeal exudate = Bacilli + Spirochaetes Lung Abscess  Lung Abscess  Predisposing factors:  Unconsciousness, alcoholism, diseased gums, absence of gag reflex  Clinical presentation:  Aspiration ----- Pneumonia --- 7 -12 days – Cavitation  Copious foul smelling sputum  Some develop pleural effusion (Empyema) Brain Abscess  Brain Abscess  Develops in association with:  1. Contagious suppurative lesion (47%)  2. Haematogenous spread  3. After Trauma  Temporal lobe Abscess: Associated with chronic otitis media and mastoiditis  Bacteroides fragilis + Gram negative aerobic bacteria.  Frontal lobe Abscess: Associated with sinusitis (Sphenoid, paranasal); Infection of Molar teeth  Peptostreptococcus + Aerobic & Anaerobic G –ve Bacilli  Intra-abdominal Sepsis Bacteroides is the main habitat of the large bowel (1011) Enterobacteriaceae e.g. E. coli = 104 Secondary Peritonitis: Escape of indigenous bowel bacteria into the peritoneal cavity (e.g. Appendicitis; Diverticulitis; Perforation) Active phagocytosis and clearance of most organisms Bacteroides fragilis and some Enterobacteria remain Peritonitis; Appendicular abscess; Subphrenic abscess; PID Synergistic Necrotizing Cellulitis  Variant of necrotizing fasciitis.  Involvement of skin, subcutaneous tissue, fascia and muscle.  Abdominal wall, lower extremities or perineum  Marked pain & tenderness.  Skin appears normal, despite underlying necrosis of subcutaneous tissue.  Skin ulcers draining foul smelling pus  Fournier gangrene  Scrotum and penis or vulva  Mean age 60 yr  DM, vascular diseases  Perianal or retroperitoneal infection, or UTI sec to urethral stricture. trauma to genital area.  Abrupt onset  Severe pain, skin necrosis  Testes, glans penis, spermatic cord spared  Rapid spread anterior abdominal wall, perineum. Fournier gangrene  Necrotizing Fasciitis  Type I = Polymicrobial (Anaerobes and facultative aerobic bacteria)  Type II = Group A -haemolytic Streptococcus; alone or in combination with Staphylococcus aureus  Type III = Gas Gangrene OR Clostridial Myonecrosis  Other = Salt water NF; Vibrio vulnificus  Necrotizing Fasciitis Pathogenesis  Decreased polymorph function under hypoxic conditions  B. fragilis inhibits phagocytosis and reduces interferon production  Facultative aerobic organisms grow along fascial planes  Synergistic action of toxins of aerobes and anaerobes on tissues  Vascular occlusion --- ischemia --- necrosis --- damaged nerves --- anaesthesia  Necrotizing Fasciitis Clinical Presentation  Onset may be subacute  Extremities (legs); Other parts may be affected  Swelling, erythema, PAIN ,hot, shiny ecchymosis,  Skin color changes red/ purple → blue/grey  Blister/ bullae /necrosis 3-5 d,  Tenderness ↓anaesthetic  Foul smelling → mixed infection  Mortality 20-47%, Necrotizing Fasciitis  Diagnosis  High index of suspicion  Necrotizing component essential Imaging studies: plain x ray: subcutaneous gas* US / CT / MRI: More specific, Increase thickness of fascial layer Microscopy & Culture Excisional deep skin biopsy Gram stain to define NF type Culture (Aerobic & Anaerobic)  Anaerobic Vaginosis  Synergistic condition  Gardnerella vaginalis; Prevotella spp.; Mobiluncus  Clinical Presentation:  Vaginal discharge and odour (Fishy)  Diagnosis:  Elevated pH > 4.5  Addition of 20% KOH to vaginal dischrge = fishy smell  Wet film shows “Clue Cells” = Epithelial cells studded with coccobacilli  Lactobacilli are supplanted by coccobacili Clue cells  Clues of Anaerobic Infection  Foul smelling discharge  Infection in proximity to a mucosal surface  Gas in tissues / specimen  Negative aerobic cultures  Diagnosis of Anaerobic Infection  Appropriate transport in anaerobic transport media  Processing in an anaerobic environment (Anaerobic cabinet)  Culture onto pre-reduced enriched culture media: Schaedler blood agar, Brucella agar with haemin, vitamin K and blood.  Selective media: Brucella agar as above with Gentamicin 80 mg/l Anaerobic transport media  Diagnosis of Anaerobic Infection  Incubate in an anaeobic incubator or anaerobic jars using gas packs  Include aerobic cultures  Incubate for 48 – 72 hours  Examine colonies growing only anaerobically for morphology, effect on agar  Examine Gram smears  GLC for volatile fatty acids  Api 20 A Anaerobic Cabinet Anaerobic Gas Pack Anaerobic jar Gas Liquid Chromatography GLC chart Api 20 A