Anaerobic Infections 2026 Past Paper

MPY2B10L3 DAGÍTAB 2026 WVSU – COLLEGE OF MEDICINE Anaerobic Infections Lecturer: Dr. Analyn Jumeras l 10/02/ 2023 l 10:00 AM – 12:00 NN OUTLINE Several vit...

MPY2B10L3 DAGÍTAB 2026 WVSU – COLLEGE OF MEDICINE Anaerobic Infections Lecturer: Dr. Analyn Jumeras l 10/02/ 2023 l 10:00 AM – 12:00 NN OUTLINE Several vital diseases are caused by anaerobic organisms, either originating from the environment, I. Anaerobic vs Aerobic Bacteria A. Introduction such as Clostridium, or from the normal flora. These B. Characteristics organisms can lead to well-known conditions, C. Metabolic Systems including tetanus, skin and soft tissue infections as D. Human Infections severe as gas gangrene, and can also cause food II. Anaerobic Bacterial Infections of Clinical Significance poisoning and Pseudomembranous colitis. A. Gram-Positive Cocci a. Peptostreptococcus B. Gram-Positive Bacilli From Jawetz a. Actinomyces Polymicrobial Nature of Anaerobic Infections b. Propionibacterium Most anaerobic infections are associated with c. Clostridium contamination of tissue by normal microbiota of the C. Gram-Negative Bacilli a. Bacteroides mucosa of the mouth, pharynx, gastrointestinal b. Prevotella tract, or genital tract. c. Porphyromonas Oropharyngeal, pleuro-pulmonary, abdominal, and d. Fusobacterium female pelvic infections associated with e. Garnerella vaginalis - Bacterial Vaginosis contamination by normal mucosal microbiota have III. Diagnosis of Anaerobic Infections IV. Treatment of Anaerobic Infections a relatively equal distribution of anaerobes and SUMMARY facultative anaerobes as causative agents; about REVIEW QUESTIONS 25% have anaerobes alone, about 25% have TRANS COMM facultative anaerobes alone, and about 50% have REFERENCES APPENDICES both anaerobes and facultative anaerobes. Aerobic bacteria may also be present, but obligate Note: Text inside boxes were transcribed from the lecture aerobes are much less common than anaerobes but not present in the PowerPoint slides of Doc Jumeras. and facultative anaerobes. I. ANAEROBIC VS AEROBIC BACTERIA B. CHARACTERISTICS A. INTRODUCTION The Functional Definition of anaerobes is that they require reduced oxygen tension for growth and they fail to grow on the surface of a solid medium in 10% CO2 in ambient air. e.g. Bacteroides and Clostridium Meanwhile, aerobic bacteria require oxygen as a terminal electron acceptor, and they will not grow in anaerobic conditions or in the absence of oxygen. Obligate aerobes: Bacillus, Mycobacterium tuberculosis C. METABOLIC SYSTEM OF AEROBES 1. Cytochrome systems for the metabolism of O2. Figure 1. Anaerobic vs Aerobic Bacteria 2. Superoxide dismutase (SOD) which catalyzes the following reaction: Aerobes and anaerobes are found all throughout the O2- + O2- + 2H+ -> H2O2 + O2 human body: the skin and mucosal surfaces. They 3. Catalase, which catalyzes the following reaction: have high concentrations in the mouth and the 2H202 -> 2H2O + O2 (gas bubbles) gastrointestinal tract. The infection results when they contaminate the sterile body sites.  B. GRAM-POSITIVE BACILLI Obligate anaerobes block both superoxide dismutase and catalase and are very susceptible to ACTINOMYCES lethal doses of oxygen. Normal flora of mouth and female genital tract Facultative anaerobes grow as well or better under Opportunistic pathogen anaerobic conditions than they do under aerobic → Actinomyces israelli conditions. → Actinomyces gerencseriae E.g. Escherichia coli – can consume all available oxygen and change to anaerobic environment. D. CLASSIFICATION Figure 4. Actinomyces israelli Elongated branching Nonspore forming Slow growth on blood agar (4-7 days) Disease: Actinomycosis Chronic suppurative and granulomatous infection that Figure 2. Flowchart of Anaerobic Bacteria produces pyogenic lesions with interconnecting sinus tracts that contain granules composed of II. ANAEROBIC BACTERIAL INFECTIONS OF microcolonies of the bacteria embedded in tissue elements. CLINICAL SIGNIFICANCE Three common forms: cervicofacial, thoracic and A. GRAM-POSITIVE COCCI abdominal PEPTOSTREPTOCCOCUS Infections of the groin, urogenital area, breast and axilla and postoperative infections of the mandible, eye and head and neck Treatment: → Penicillin (6-12 months) → Clindamycin → Erythromycin Three common forms: → Cervicofacial – usually around the mouth and neck area → Thoracic Figure 3. Peptostreptococcus → Abdominal → Other forms also include: Groin and genital area Anaerococcus, Finegoldia, Peptoniphilus Normal microbiota PROPIONIBACTERIUM ACNES Opportunistic Infections Diseases: → Brain Abscess → Pleuropulmonary → Necrotizing Fasciitis → Deep skin and soft tissue → Intraabdominal → Female Genital Tract Figure 5. Propionibacterium acnes MPY2B10L3⚡Anaerobic Infections Page 2 of 8  Normal microbiota of the skin, oral cavity, large The very important risk factor is antibiotic exposure. intestine, conjunctiva, and external ear canal Whether it is the duration, the number of antibiotics, Highly pleomorphic, showing curved, clubbed or and the type of antibiotic. pointed ends; long forms with beaded uneven ·The most common presentation of CDI is GI staining; and occasionally coccoid or spherical forms infection. Propionibacterium acnes 3 or more loose stools of the patient Opportunistic pathogen E.g. There is a patient in the hospital, presenting Disease: acne vulgaris; inflammatory conditions, with an acute onset of diarrhea, more than 3 postsurgical wound infections episodes, loose and very watery,. One of the Prosthetic joint infections: shoulder, CNS shunt differential diagnosis should be Clostridoides infections, osteomyelitis, endocarditis and difficile infection. endophthalmitis Postsurgical wound infections – especially when Table 1. Risk Factors for C. difficile Infection (CDI) there is a foreign body applied RISKS FOR DEVELOPMENT OF CLOSTRIDIODES Prosthesis in synthetic joint infections in the DIFFICILE INFECTION Any antibiotic versus no antibiotic shoulders Number of antibiotics (risk increases with Central nervous system – insertion of shunts number) Osteomyelitis – insertion of nails when there is Days of antibiotics (increased risk with increased days) trauma Endocarditis – valve replacement Type of antibiotic: Highest risk: Clindamycin, Fluoroquinolones, Cephalosporins of 2nd gen and higher CLOSTRIDIUM DIFFICILE Moderate risk: Penicillin, Macrolides, Penicillin Lactamase inhibitors, Carbapenems, Vancomycin, Metronidazole Lowest risk: Aminoglycosides, Tetracyclines, Trimethoprim, Sulfonamides, Rifampin Proton pump inhibitors and histamine type 2 blockers Patient Age (increased risk with increased age of the patient) Prior Hospitalization Severity of Underlying Illness Abdominal Surgery Figure 6. Clostridium difficile Nasogastric Tube Spore forming Duration of Hospitalization Produce 2 toxins – A and B Long-term care residency Other virulence factors → C. difficile binary toxin (CDT) CLOSTRIDIUM TETANI → Surface Layer proteins → Surface Polysaccharides → Flagella → Various adhesins Disease: C. difficile Infection (CDI) Treatment: → Vancomycin → Fidaxomicin → Metronidazole Figure 7. Clostridium tetani Previously, the treatment that Doc is giving is Metronidazole but the recommendation now of the Variable staining in older cultures or tissue samples CDC, it is an alternative treatment already and not Present in soil, in the intestinal tract, and feces of the primary treatment for CDI. various animals MPY2B10L3⚡Anaerobic Infections Page 3 of 8  2 toxins: Wound botulism Tetanospamin – called tetanus toxin Inhalational botulism Tetanolysin Clinical Manifestations: Resemble a squash racquet → Acute, bilateral cranial neuropathies Growth in culture is optimal at 37 degrees Celsius → Symmetrical descending weakness under strictly anaerobic conditions Treatment: Disease: Tetanus → Supportive care Persistent tonic spasm with violent brief → Heptavalent botulinum antitoxin (HBAT) – A to G botulinum toxin types equine-derived antibody exacerbations → For non-infant botulism Commences in the muscles of the neck and jaw, → Administered within 2 days of symptom onset causing closure of the jaw (trismus, lockjaw) → Current recommended dose is 50 mg/kg as an IV Involves muscles of the trunk more than the limbs infusion Acute in onset → Antibacterial therapy – untested Incubation period: 3-21 days Penicillin G (10-20 million units daily) is frequently 4 Clinical Type of Tetanus: recommended → Generalized - often seen in the hospital → Alternative: Metronidazole → Localized – involves rigidity of the muscles → Recovery – 1st 3 months up to 1 year associated with the site of spore inoculation → Cephalic – special form of localized disease CLOSTRIDIUM PERFRINGES AND CLOSTRIDIAL affecting cranial nerve musculature MYONECROSIS (GAS GANGRENE) → Neonatal – follows infection of the umbilical stump, most commonly caused by failure of aseptic technique if mothers are inadequately immunized Treatment → Stabilization: Early tracheostomy is usually beneficial → Management of muscle spasms: Benzodiazepines as mainstay as symptomatic Figure 8. Clostridium perfringes therapy → Wound management Traumatic injury + Clostridial Spores → Passive immunization: Human tetanus immune C. perfringes Type A: most common in human stool globulin (HTIG) shortens the course of tetanus and Other species that can cause myonecrosis: C. may lessen its severity septicum, C. sordelli, C. novyi, C. bifermentans, C. → Antimicrobial Therapy: Metronidazole histolyticum TETANUS Production of exotoxin: lecithinase Risk factor for a high mortality in Tetanus is when it Contaminated wounds has a short incubation period. The shorter it is, the → Automobile accidents, postoperative GI/BT higher the mortality and morbidity. surgery, septic abortions The goal is prevention which is why we have a very → Lesions of vascular insufficiency, burns, good coverage of vaccination for Tetanus. malignancy If an adult has completed childhood immunizations, Lecithinase – alpha toxin -> rapid hemolytic anemia the booster dose depends on the age of the patient. Contaminated wound -> Invasion of Clostridial spores In the guidelines, it’s every 10 years but for severe -> Myonecrosis wounds it’s 5 years. Incubation period: 24-72 hours Clinical presentation: severe pain in the absence of obvious physical findings CLOSTRIDIUM BOTULINUM → Redness at the site of the wound -> rapidly Large, gram-positive, strictly anaerobic bacilli spreading brown to purple discoloration of the Subterminal spore: able to tolerate 100 °C at 1 atm skin -> hemorrhagic bullae, serosanguinous for several hours discharge with mousy odor Infant botulism Adult botulism MPY2B10L3⚡Anaerobic Infections Page 4 of 8  Diagnosis: Gram stain of discharge – gram positive Appear as slender rods or coccobacilli boxcar-shaped bacilli, few PMNs (earliest laboratory → Prevotella melaninogenica finding) → Prevotella bivia Treatment: → Urgent surgical debridement of infected tissues → Prevotella disiens → Abdominal wall: debridement + generous Brain and Lung Abscesses resection margin – prevention of recurrence or Empyema progression of infection PLUS Pelvic Inflammatory Disease → Antimicrobial therapy Tubo-ovarian abscesses → Early antibiotic intervention is essential → Penicillin PORPHYROMONAS → Alternative agents: Metronidazole, Clindamycin, Carbapenems C. GRAM NEGATIVE BACILLI 1. Bacteroides 2. Prevotella 3. Porphyromonas 4. Fusobacteria Figure 11. Porphyromonas BACTERIODES Normal oral microbiota Gingival and periapical tooth infections Breast and axillary infections Perianal and male genital infections FUSOBACTERIA Fusobacterium necrophorum Figure 9. Bacteroides Large group of bile-resistant, nonspore forming, slender gram-negative rods that may appear as coccobacilli Bacilli fragilis group Figure 12. Fusobacterium necrophorum Normal inhabitants of the bowel and other sites Very pleomorphic, long rod with round ends – make Disruption of the intestinal wall as occurs in bizarre forms perforations related to surgery or trauma, acute NOT a component of the healthy oral cavity appendicits, diverticulitis Severe infections of the head and neck Virulence factor: Capsular Polysaccharides – induce Complicated infection: Lemierre’s disease abscess formation Virulence factors: leukotoxin; a hemagglutinin, a Treatment: Gentamicin and Clindamycin hemolysin, and lipopolysaccharide (endotoxin) PREVOTELLA Fusobacterium nucleatum Figure 10. Prevotella Figure 13. Fusobacterium nucleatum MPY2B10L3⚡Anaerobic Infections Page 5 of 8  Thin rods with tapered ends (needle-shaped IV. TREATMENT OF ANAEROBIC morphology) INFECTIONS Significant component of gingival genital, Surgical drainage plus antimicrobial therapy gastrointestinal & upper respiratory tracts microbiota Antimicrobials: Pleuropulmonary infections, obstetric infections, chorioamnionitis, and brain abscesses complication → Clindamycin and Metronidazole periodontal disease Alternative Drugs: → Cefoxitin, Cefotetan, Piperacillin, Carbapenem GARDNERELLA VAGINALIS Bacteroides and Prevotella species: → Drug of choice: Penicillin G Isolated from the normal female genitourinary tract Inflammatory cells are not present “Clue cells” – vaginal epithelial cells covered with SUMMARY many gram-variable bacilli Anaerobic bacteria are organisms that do not grow in Vaginal discharge – “fishy” odor the presence of oxygen and require special handling pH > 4.5 (normal pH is