Diplococci - aerobic Notes
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Chapter 2 Acyanotic Defects NOTES DIPLOCOCCI: AEROBIC MICROBE OVERVIEW ▪ Spherical-shaped bacteria (cocci), appear in pairs as joined cells (diplo) ▪ Gram-negative, aerobes/facultative anaerobes, non-motile, non-spore forming TYPES Moraxella catarrhalis ▪ Oxidase +, nitrate reduction + (characteristic) ▪ Part of normal respiratory ﬂora, causes opportunistic infections ▪ Virulence factors ▫ Beta-lactamase production → penicillin resistant ▫ DNase production ▪ Culture ▫ Isolation specimen: respiratory secretions, sputum ▫ Media: blood, chocolate agar (round, opaque colonies that turn pink after 48 hours; positive “hockey puck sign”: able to slide colonies across agar with wooden stick without disruption) Neisseria gonorrhoeae ▪ Facultatively intracellular ▪ Oxidase +, catalase + ▪ Fermentation ▫ Glucose; differentiation from N. meningitidis ▪ Virulence factors ▫ LOS/endotoxin: triggers inﬂammation; undergoes antigenic variation ▫ IgA1 protease: cleaves IgA antibodies; aids in evasion of humoral immune response ▫ Type IV pili: promote adhesion of bacteria to epithelium; undergo phase, antigenic variation ▫ Porins (PorA, PorB): allow movement of ions, nutrients into bacteria, promote invasion into cells ▫ Opa, Opc: promote adhesion, invasion; undergo phase, antigenic variation ▪ Culture ▫ Isolation specimen: urine, vaginal/ endocervical swab, urethral swab; pharyngeal, rectal swab ▫ Media: Thayer–Martin VCN, chocolate agar Neisseria meningitidis ▪ Facultatively intracellular ▪ Oxidase +, catalase + ▪ Fermentation ▫ Maltose, glucose ▪ Present as normal non-pathogenic ﬂora of nasopharynx in 10% of adults ▪ Virulence factors ▫ Capsule: prevents phagocytosis; N. meningitidis subdivided into 13 serogroups based on capsular polysaccharides; A, B, C, W135, Y account for most disease cases ▫ Lipooligosaccharide (LOS)/endotoxin: released in blebs/vesicle-like structures → sepsis, vascular necrosis, hemorrhage into surrounding tissue; levels of LOS closely correlate with prognosis ▫ IgA1 protease: cleaves IgA antibodies; aids in evasion of humoral immune response ▫ Pili: promote adherence of bacteria to nasopharyngeal epithelium; undergo phase, antigenic variation → protect against host immune response, vaccines ▫ Opacity proteins (Opa, Opc): promote adhesion, invasion OSMOSIS.ORG 369
▫ Factor H binding protein: downregulates alternative complement pathway ▪ Culture ▫ Isolation specimen: blood, cerebrospinal ﬂuid (CSF), petechial scrapings ▫ Media: Thayer–Martin vancomycin, colistin, nystatin (VCN), chocolate agar MORAXELLA CATARRHALIS osms.it/moraxella-catarrhalis PATHOLOGY & CAUSES ▪ Gram-negative diplococcus → respiratory tract infections, otitis media ▪ Infections caused by M. catarrhalis ▫ Respiratory tract infections (bronchitis, rhinosinusitis, laryngitis, bronchopneumonia, communityacquired bacterial pneumonia) ▫ Otitis media in children < three years of age ▫ Exacerbations of chronic obstructive pulmonary disease (COPD) RISK FACTORS ▪ Immunocompromised individuals ▪ Individuals with chronic respiratory disease 370 OSMOSIS.ORG (e.g. COPD, emphysema) ▪ Children < two years of age, elderly COMPLICATIONS ▪ Rare: bacteremia, septicemia, urethritis, septic arthritis SIGNS & SYMPTOMS ▪ Acute bacterial rhinosinusitis: fever, nasal obstruction, purulent nasal discharge, facial pain, headache ▪ Otitis media: fever, ear pain, bulging tympanic membrane ▪ Exacerbations of COPD: increased cough, sputum production/change in color, dyspnea
Chapter 68 Diplococci: Aerobic DIAGNOSIS OTHER DIAGNOSTICS ▪ Clinical presentation ▫ Sufﬁcient for diagnosis ▪ Microbiologic diagnosis TREATMENT MEDICATIONS ▪ ▪ ▪ ▪ Amoxicillin-clavulanate Trimethoprim-sulfamethoxazole Third-/second-generation cephalosporins Macrolides (e.g. azithromycin, clarithromycin) NEISSERIA GONORRHOEAE osms.it/neisseria-gonorrhoeae PATHOLOGY & CAUSES ▪ Gram-negative diplococcus → gonococcal disease (gonorrhea, disseminated gonococcemia, gonococcal ophthalmia neonatorum) ▪ Portal of entry ▫ Unprotected sex (vaginal, oral, anal): bacteria attaches, invades genitourinary, rectal, oral epithelium via Opa, Opc, pili → gonorrhea ▫ Rare: invades bloodstream → disseminated gonococcemia, septic arthritis ▫ Perinatal transmission: birth canal of infected mother → gonococcal ophthalmia neonatorum TYPES ▪ Gonorrhea ▫ Urethritis, cervicitis, proctitis, pharyngitis ▪ Disseminated gonococcemia ▫ Result of spread, intravascular multiplication of N. gonorrhoeae; joints, skin (dermatitis-arthritis syndrome) ▪ Gonococcal ophthalmia neonatorum ▫ Causes gonococcal conjunctivitis RISK FACTORS ▪ Unprotected sex ▫ Individuals with multiple sexual partners, sex between individuals who are biologically male (MSM), recent new sexual partner ▪ Low educational, socioeconomic levels ▪ Substance abuse ▪ History of gonorrhea COMPLICATIONS Gonorrhea ▪ Epididymitis, prostatitis, penile lymphangitis, urethral strictures in individuals who are biologically male; cervical gonorrhea → pelvic inﬂammatory disease → infertility in individuals who are biologically female Gonococcal ophthalmia neonatorum ▪ Corneal scarring/perforation, blindness SIGNS & SYMPTOMS Gonorrhea ▪ Some individuals who are biologically male, most individuals who are biologically female (50–80%) asymptomatic ▪ Urethritis: dysuria, urinary urgency, purulent foul-smelling urethral discharge ▪ Cervicitis: lower abdominal discomfort, dyspareunia (pain during sexual intercourse), vaginal pruritus, purulent foulsmelling vaginal discharge OSMOSIS.ORG 371
▪ Proctitis: anal pruritus, tenesmus, rectal fullness, constipation, purulent anorectal discharge, bleeding ▪ Pharyngitis: sore throat, swollen lymph nodes Disseminated gonococcemia ▪ Fever, chills, generalized malaise ▪ Polyarthralgia (multiple joint pain) ▪ Tenosynovitis (tendon inﬂammation) ▪ Pustular/vesiculopustular lesions on skin Gonococcal ophthalmia neonatorum ▪ Purulent conjunctival discharge ▪ Swollen eyelids ▪ Conjunctival hyperemia, chemosis DIAGNOSIS LAB RESULTS Blood tests ▪ ≥ two white blood cells in urethral secretions ▪ ≥ 10 white blood cells on microscopic examination of ﬁrst void urine ▪ Disseminated gonococcemia ▫ Positive blood culture ▫ Synovial ﬂuid leukocyte count: increased values (50,000 cells/microL) Gram stain ▪ Polymorphonuclear leukocytes with intracellular gram-negative diplococci Nucleic acid ampliﬁcation testing (NAAT) ▪ For initial diagnosis TREATMENT MEDICATIONS Figure 68.1 A neonate with gonococcal ophthalmia neonatorum. ▪ Uncomplicated gonorrhea ▫ Intramuscular injections of ceftriaxone + azithromycin/doxycycline (in case of gonococcal resistance to cephalosporins, potential chlamydia regardless of chlamydial coinfection status) OTHER INTERVENTIONS ▪ Prophylaxis ▫ No vaccines ▫ Extensive antigenic variations of bacterial components (pili, LOS, opa proteins) prevents development of immunological memory Figure 68.2 Creamy discharge emanating from the external urethral meatus is typical of genital gonorrhea infection. 372 OSMOSIS.ORG
Chapter 68 Diplococci: Aerobic NEISSERIA MENINGITIDIS osms.it/neisseria-meningitidis PATHOLOGY & CAUSES SIGNS & SYMPTOMS ▪ Gram-negative diplococcus → meningococcal disease (meningitis, meningococcemia) ▪ Portal of entry ▫ Inhalation of respiratory droplets → bacteria attaches to respiratory epithelium via Opa, Opc, pili → nasopharynx colonization → usually resolves asymptomatically (carriers) ▫ Invades bloodstream → meningococcal disease (rare) Meningococcemia ▪ Petechial rash caused by destruction of blood vessels, hemorrhage due to endotoxin release; fever, chills; joint, muscle pain RISK FACTORS Meningitis ▪ Infants ▫ Early nonspeciﬁc: irritability, vomiting, inactivity, poor feeding, temperature instability ▫ Late speciﬁc: bulging anterior fontanelle, seizures ▪ Children, adolescents, adults ▫ Early nonspeciﬁc: sudden onset of fever, headache, nausea, vomiting, myalgia ▫ Late speciﬁc: altered mental status, lethargy, neck stiffness (nuchal rigidity), photophobia ▫ First speciﬁc symptoms of sepsis: abnormal skin color (pallor/mottling) which can evolve from nonspeciﬁc rash to petechial to hemorrhagic over several hours; cold hands, feet; leg pain ▪ Signs upon physical examination ▫ Positive Kernig’s sign: inability to straighten leg when hip ﬂexed to 90º ▫ Positive Brudzinski’s sign: ﬂexing of neck by examiner → ﬂexing of hips, knees COMPLICATIONS Fulminant meningococcemia ▪ Abrupt onset ▪ Rapid enlargement of petechiae/ ecchymoses ▪ Hypotension, tachycardia due to vascular collapse, shock TYPES ▪ Meningococcemia ▫ Result of intravascular multiplication of N.meningitidis; can occur alone/in conjunction with meningitis ▪ Meningitis ▫ Most common; occurs upon spreading of bacteria to meninges during meningococcemia; usually affects children, adolescents ▪ Fulminant meningococcemia ▫ AKA Waterhouse–Friderichsen syndrome; most severe form of meningococcal sepsis; massive bilateral hemorrhage into adrenal glands ▪ Infants 6–24 months (due to immature immune system, inability to vaccinate) ▪ Living in close quarters (military barracks, dormitories) ▪ Adrenal insufﬁciency; disseminated intravascular coagulation (DIC); purpura fulminans (cutaneous hemorrhage, necrosis due to vascular thrombosis, DIC); acute respiratory distress syndrome (ARDS); coma, death OSMOSIS.ORG 373
DIAGNOSIS LAB RESULTS ▪ Fulminant meningococcemia ▫ Adrenal insufﬁciency signs: ↓ blood glucose, ↑ K+, ↓ Na+, adrenocorticotropic hormone (ACTH) stimulation test (low response) ▫ Thrombocytopenia due to DIC ▫ Metabolic acidosis ▪ Meningococcemia and meningitis ▫ Blood culture and CSF analysis OTHER DIAGNOSTICS ▪ Physical examination ▫ Characteristic ﬁndings of meningitis TREATMENT MEDICATIONS Prophylaxis ▪ Quadrivalent immunization with puriﬁed capsular polysaccharides from serogroups A, C, Y, W135 (group B not available) Figure 68.3 A petechial rash can be seen in the late stages of meningococcal septicemia. Meningococcal disease ▪ Antibiotics ▫ Third-generation cephalosporins (e.g. cefotaxime, ceftriaxone)/penicillin G ▪ Chloramphenicol ▫ In case of beta-lactam antibiotics hypersensitivity ▪ Chemoprophylaxis of individuals in close contact with the infected ▫ Rifampin of ciproﬂoxacin ▪ Hydrocortisone ▫ For adrenal insufﬁciency SURGERY ▪ Plastic surgery, skin grafting, amputation to treat tissue necrosis 374 OSMOSIS.ORG Figure 68.4 The brain of an individual at post mortem following death from bacterial meningitis. Nesseiria meningitidis is the most common causative organism amongst adolescents and young adults.
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