3 Parvobacteria Gram stain of E. coli Gram stain of Haemophilus influenzae
4 H. influenzae Small, non-sporing, non-motile bacterium Encapsulated strains isolated from cerebrospinal fluid are gram-negative coccobacilliNon encapsulated organisms from sputum are pleomorphicRequires preformed growth factors that are present in blood, specificallyX factor (i.e., hemin – from iron containing pigments)V factor (NAD or NADP).Usually grown on chocolate blood agar
10 Epidemiology:Only found in humansNormally found in the pharynx (conjunctiva, genital tract)Spread by airborne droplets or direct contact with respiratory secretionsBoth extra and intracellular pathogen
11 Virulence and Immunity Some strains are encapsulated with polyribosylribitolphosphate (PRP)Subdivides H. influenzae into groups a-fType B is a major virulence factor95 percent of bloodstream and meningeal Haemophilus infections in children are caused by type B organismsEncapsulated organisms penetrate the epithelium of the nasopharynx and invade the blood capillaries directlyResist phagocytosis and complement-mediated lysis in the the nonimmune host
13 The age incidence of H. influenzae meningitis is inversely proportional to the titre of bactericidal antibody in the bloodPassively acquired from the mother or actively formedIn children aged 2 months to 3 years, antibody levels are minimal
14 Relation of the age incidence of bacterial meningitis caused by Haemophilus influenzae to bactericidal antibody titres in the blood
15 Clinical Manifestations HibBacteraemiaMeningitisNo particular features to distinguish HiB meningitis from other causesMay be fulminant but usually presents with several days of mild URTI followed by deteriorationMortality <5% but neurologic sequelae are commonSeptic arthritisPreviously common in children <2 yearsSingle weight-bearing joint
16 EpiglottitisAcute respiratory obstruction caused by cellulitis of supraglottic tissuesUsually children aged between 2 and 7 but also occurs in adultsSore throat, fever, pooling of secretions, restless, anxious, sitting in characteristic position – sitting up, tongue sticking out, drooling, inspiratory stridor
27 Bordetella pertussis Gram-negative coccobacillus Nutritionally fastidious, normally cultivated on medium containing bloodPrimarily a human pathogenOther members of the genus Bordetella can cause disease in animalsCauses Pertussis (Whooping cough)Serious, highly communicable acute tracheobronchitis
28 Whooping cough - Epidemiology Estimated 285,000 deaths in 2001 worldwide131 cases in Ireland in 20028296 cases in U.S.Previously mainly in childrenNow a number of reports of increasing pertussis in adults because of the limited duration of protection from pertussis vaccine
30 Virulence factors Filamentous Hemagglutinin (Fha) Pertussis Toxin (PT) ability to agglutinate RBCsBinds to galactose on sulfated glycolipids (in membranes of ciliated cells)Antibodies to Fha protect against infectionPertussis Toxin (PT)may act as an adhesin and toxinTwo toxin subunits (S2 and S3) mediate adherenceAnti-Pt-antibody prevents colonization of ciliated cells, protects vs infection
31 Adenylate cyclase toxin (ACT) Mainly cell-associated, can be releasedactivated adenylate cyclase leads to impaired white cell functionTracheal cytotoxin (TCT)Peptidoglycan fragmentReleased by lysisKills ciliated cellsStimulates release of IL-1 (produces fever)Dermonecrotic toxin (DNT)Causes smooth muscle contraction leading to ischaemic necrosis
32 Pathogenesis Ciliostatsis and damage to epithelium mediated by TCT Attachment to respiratory epithelium mediated by FHA and possibly PTCiliostatsis and damage to epithelium mediated by TCTInhibition of phagocytsosis mediated by ACT, PT AND DNTSystemaic manifestations probably manifested by PT
33 Pertussis (whooping cough) Spread by aerosol/direct contactEarly symptoms - nonspecific - seldom diagnosed until paroxysmal stage - most contagious earlyStages - Incubation period: 7-10 days - Catarrhal stage:Symptoms like common cold, lasts 1-2 weeksParoxysmal stage:dry nonproductive cough, paroxysmalexcess mucus production, vomiting, convulsions, cyanosis, paroxysms separated by inspiratory whoopLasts 4-6 weeks
34 Children who are too young to be fully vaccinated andthose who have notcompleted the primaryvaccination series are athighest risk for severe illness
35 Complications Pneumonia Neurological damage Either caused by B. pertussis or secondary bacterial infectionBronchiectasisNeurological damageSeizures in 1.4%, encephalopathy 0.2% (seizures and mental retardation)Raised intrathoracic and intrabdominal pressure leading to intracranial bleeds, conjunctival haemorrhages, petichiae, pneumothorax, inguinal hernia etc.
36 Laboratory DiagnosisLeucocytosis with absolute lymphocytosis at end of catarrhal and beginning of paroxysmal stageCulture: pernasal swab early in course of illness, plate on Bordet-Genou or charcoal mediumPCRSerology
38 Management and Prevention effect of antimicrobial therapy on the severity and duration of the illness is debated but erythromycin x 14 days (clarythromycin and azithromycin are alternatives) is recommended as it may reduce the spread of diseaseAntimicrobial prophylaxis (erythromycin x 14 d) should be offered to all family members and other close contactsThere is no evidence of any benefit from chemoprophylaxis given more than 21 days from the date of onset of the primary case.Chemoprophylaxis should be considered if a case has a household contact who is at greatest risk from pertussis – primarily young
39 VaccinationWhole-cell pertussis vaccination is associated with rare serious events such as acute encephalopathy, estimated to occur at per million doses1996 several new acellular pertussis vaccines developedmulticomponent vaccines contain combinations of pertussis toxoid, filamentous hemagglutinin, pertactin, and the two types of fimbriaefewer side effects than the whole cell vaccine
41 Brucella species Gram-negative coccobacillus Facultative intracellular parasitesSix speciesB. abortus - cattleB. suis - pigsB. melitensis - goatsB. canis - dogsB. ovis - sheepB. neotomae - desert wood ratsCause zoonoses worldwideB. abortus is still prevalent in cattle in Republic and Northern Ireland
42 B. abortusDisease in cattle - causes abortion, mammary infection (not mastitis) - transmission to humans by ingestion (infected milk) or inhalation (aborted material)Disease in humans - long incubation period (weeks, months) - malaise, chills, fever, sweats - weakness, myalgia, headache - nervous symptoms (psychoneurosis) - difficult to diagnose due to vagueness of symptoms
43 B. melitensis Primary hosts are sheep and goat Sir David Bruce ( ) isolatedthe bacterium of Malta fever in 1887.B. melitensisPrimary hosts are sheep and goatDisease in goat similar to B. abortus in cattleEarly localization in mammary gland, shedding in milk leads to human infectionGastroenteritis - Malta/Mediterranean feverpotential agent of bioterrorism
45 Pathogenesis Ingestion. Most common. Inhalation. Certain occupations e.g. laboratory workers, abbattoir workers.Enter the body through skin wounds.Slaughterhouses or meat packing plants or for veterinarians.Invades mucous membranes and transported (free or in phagocytes) to lymph nodes enter phagocytic cells.Spread via circulation to other organs liver, spleen, bone marrow, kidney: cause granulomas .
46 Clinical presentation Extremely variable.Any system can be affectedIn the acute form (<8 weeks from illness onset)nonspecific and "flu-like," including fever, sweats, malaise, anorexia, headache, myalgia, and back pain. Lymphadenopathy, splenomegalyChronic (>1 year from illness onset), may include chronic fatigue syndrome-like, depressive episodes, and arthritis.
47 Laboratory Diagnosis B. melitensis: blood cultures B. abortus: serology SAT, CoombsFour-fold rise in titre
48 TreatmentTetracycline +/- rifampicin for 6 weeks
49 Yersinia species Y. pestis Causes plague –bubonic/pneumonic Transmitted by flea bite, occasionally from aeroslisationperiodic disease outbreaks in rodent populations, hungry infected fleas that have lost their normal hosts seek other sources of bloodRat-borne epidemics continue to occur in some developing countries, particularly in rural areas.Potential bioterrorist agent
57 FIGURE 226-3. Transmission of plague FIGURE Transmission of plague. The wide arrows indicate common modes of transmission, the medium arrows indicate occasional transmission, and the thin arrows indicate rare kinds of transmission.
58 Clinical features Bubonic plague: Septicemic plague: Pneumonic plague: enlarged, tender lymph nodes, fever, chills and prostrationSepticemic plague:fever, chills, prostration, abdominal pain, shock and bleeding into skin and other organsPneumonic plague:fever, chills, cough and difficulty breathing; rapid shock and death if not treated earlyTREATMENTStreptomycin/gentamicin, ciprofloxacin, doxycycline
59 Plague axillary bubo(CDC Public Health Image Library No:2061)
60 Plague inguinal buboCDC Public Health Image Library No:2044
62 Peripheral blood smear of septicaemic plague showing FIGURE Peripheral blood smear of septicemic plague patient showing large numbers of bipolar-staining bacilli. (Courtesy of the Centers for Disease Control and Prevention, Fort Collins, CO.)Peripheral blood smear of septicaemic plague showingbipolar staining bacilli
63 Y. pseudotuberculosis Y. enterocolitica Both can cause abdominal symptomsOccurs most often in young children. Fever, abdominal pain, and diarrhoea, which is often bloodyMay mimic appendicitisEating contaminated food, especially raw or undercooked porkOutbreaks are describedUsually self-limitedTetracyclines
64 Pasteurella multocida Cause of animal bite infectionsPresent in dog/cat oropharynxTreat with penicillin
65 Dog and cat bites Common Nearly all infections are mixed Aerobes S. aureus, streptococci, Pasteurella etc. and anerobesConsider tetanus and rabies
66 Antimicrobial prophylaxis Debride and irrigateTetanus prophylaxisAntimicrobial prophylaxisCo-amoxyclav for 5- 7 daysEspecially forsevere early infectionslate (>8 h) presentationWounds of face, hand, genitalsBone or joint involvementImmunosuppressed host
67 Francisella tularensis Small, fastidious Gram-negative bacillusZoonosesPredominantly North America – type APotential bioterrorist agent – no person-person spreadTransmission:Bite of an infected arthropodContact with infected animals (small rodents)AerosolClinical:Mainly ulceroglandular or respiratory
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