Typhoid Fever and Septicaemia
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Questions and Answers

What is the primary mode of transmission for Tuberculosis?

inhalation of infected bacilli

What are common symptoms of Pulmonary Tuberculosis (PTB)?

  • Fever and weight loss
  • Chronic cough longer than 3 weeks
  • Haemoptysis
  • All of the above (correct)

    • Culture on solid medium is a rapid diagnostic method for Tuberculosis.

    False

    The most accurate way to diagnose leprosy is through ______________.

    <p>tissue biopsy</p> Signup and view all the answers

    Match the type of leprosy with its characteristic description:

    <p>Tuberculoid leprosy = CMI is good and nerves are not affected Lepromatous leprosy = Low CMI with heavy bacterial load and nerves are often destroyed</p> Signup and view all the answers

    What is the definition of Typhoid fever?

    <p>TF is defined as acute febrile systemic illness caused by a bacterium called Salmonella enterica serotype typhi</p> Signup and view all the answers

    Which bacteria causes Typhoid fever?

    <p>Salmonella typhi</p> Signup and view all the answers

    Typhoidal salmonella induce ____________ in their host macrophages to attract more macrophages.

    <p>apoptosis</p> Signup and view all the answers

    Match the Mycobacterial species with their characteristics:

    <p>Pathogenic mycobacterial species = Always cause diseases Opportunistic mycobacterial species = Cause diseases when immunity is low Mycobacterium tuberculosis complex = Includes M.tuberculosis, M.bovis, M.africanum M.leprae = Pathogenic obligate mycobacterial specie</p> Signup and view all the answers

    Tuberculosis is one of the poverty-related diseases.

    <p>True</p> Signup and view all the answers

    What are Streptococci?

    <p>Gram-positive spherical bacteria that form pairs or chains during growth.</p> Signup and view all the answers

    What are the classifications of streptococci based on hemolysis?

    <p>All of the above</p> Signup and view all the answers

    Streptococci are sporing bacteria.

    <p>False</p> Signup and view all the answers

    ______ are group B Streptococci known for causing neonatal sepsis and meningitis.

    <p>S.agalactiae</p> Signup and view all the answers

    Match the Streptococcus group with important diseases:

    <p>S.Pyogenes = Pharyngitis, Impetigo, Rheumatic fever S.agalactiae = Neonatal sepsis and meningitis, Bacteremia in adults S.dysgalactiae = Pharyngitis, pyogenic infections Enterococcus feacalis = Endocarditis, abdominal abscess, UTI</p> Signup and view all the answers

    What is the most serious infection caused by the Viridans Group?

    <p>subacute endocarditis</p> Signup and view all the answers

    Which of the following is a virulence factor of S.pneumoniae?

    <p>Capsules</p> Signup and view all the answers

    The Viridans Group bacteria are very invasive.

    <p>False</p> Signup and view all the answers

    What test is used to presumptively identify group A streptococci?

    <p>Bacitracin test</p> Signup and view all the answers

    Match the following tests with the streptococci they differentiate between:

    <p>Optochin Test = S.pneumoniae Bacitracin susceptibility Test = S.pyogenes (Group A) CAMP test = S.agalactiae (Group B)</p> Signup and view all the answers

    Study Notes

    Septicaemias and Typhoid Fever

    • Definition of Septicaemia: Presence or multiplication of bacteria with/without toxins in the blood stream, leading to clinical manifestations – systemic illness.
    • Bacteraemia: Presence of bacteria in the blood stream without clinical manifestations, usually transient.
    • Typhoid Fever (TF): Acute febrile systemic illness caused by Salmonella enterica serotype typhi, formerly known as Salmonella typhi.

    Aetiological Agent of Typhoid Fever

    • Salmonella typhi: A Gram-negative bacillus, member of the family Enterobacteriaceae.
    • Properties: Motile, produces hydrogen sulphide (H2S), making colonies black.

    Mode of Transmission of Typhoid Fever

    • Oral transmission: Via food or beverages handled by an often asymptomatic carrier, shedding bacteria through stool or urine.
    • Hand-to-mouth transmission: After using a contaminated toilet and neglecting hand hygiene.
    • Oral transmission: Via sewage-contaminated water or shellfish.

    Epidemiology of Typhoid Fever

    • Disease of the poor: Associated with poor environmental sanitation, poor water supply, poor personal hygiene, and poor waste disposal.
    • Common in rural areas and urban slums: High prevalence in under-developed/developing countries of Africa and Asia.
    • More common in children and young adults: Than in older patients.

    Pathogenesis of Typhoid Fever

    • Faeco-oral route: Ingestion of contaminated food or water, survival of bacteria in the stomach, and multiplication in the small intestine (terminal ileum).
    • Infection of Peyer's patches: Adherence of S. typhi to epithelium, induction of macrophages, and subsequent multiplication in the lymphatic system.
    • Bacteraemia and systemic infection: Breaking out into the bloodstream, infecting the rest of the body, and inducing clinical manifestations.

    Clinical Manifestations of Typhoid Fever

    • Incubation period: 3-30 days, depending on inoculum size and host defense.
    • Classical onset: Daily remittent fever pattern, with temperature variation, chills, headache, and malaise.
    • Intestinal manifestations: Constipation, diarrhoea, and abdominal tenderness.
    • Fever: Prolonged and persistent in untreated patients.

    Laboratory Diagnosis of Typhoid Fever

    • Gold standard: Isolation of the organism in pure culture from clinical specimens.
    • Microbiological tests: Blood culture, urine culture, and stool culture.
    • Widal test: An agglutination reaction, detecting antibodies against S. typhi.

    Treatment and Prevention of Typhoid Fever

    • Supportive treatment: Rehydration, correction of electrolytes imbalance, and nutrition.
    • Definitive treatment: Antimicrobial therapy, using 3rd and 4th generation cephalosporins or fluoroquinolones.
    • Prevention and control: Based on WASH strategy, including provision of potable water, sanitation, and personal hygiene.

    Mycobacterial Infections

    • Definition: Infections caused by pathogenic mycobacterial species.
    • Classification: Divided into two categories: obligate and opportunistic mycobacterial species.
    • Obligate mycobacterial species: Always cause disease, e.g., M. tuberculosis, M. leprae, and M. ulcerans.
    • Opportunistic mycobacterial species: Cause disease when immunity is low, e.g., M. kansasii, M. simiae, and M. avium complex.

    Characteristics of Mycobacterial Species

    • Acid-fastness: Retain the color of the initial stain when stained with Zeihl-Neelsen reagents.
    • Growth rate: Slow-growing, requiring long periods of incubation.
    • Temperature of growth: Grow best at 35-37°C.
    • Pigment production: Divided into three classes: scotochromogen, photochromogen, and non-chromogen.

    Tuberculosis (TB)

    • Definition: Chronic inflammatory granulomatous infection with central area of caseation necrosis.
    • Aetiology: Caused by Mycobacterium tuberculosis complex (MTBC), including M. tuberculosis, M. bovis, and M. africanum.
    • Epidemiology and burden: TB is a major public health problem, closely related to poverty, overcrowding, and malnutrition.

    Pathogenesis of TB

    • Primary infection: Inhalation of infected droplets, affecting the apical portion of the lungs.
    • Ghon focus: Formation of chronic inflammatory granulomatous lesions.
    • Latency and reactivation: Healing of primary infection, followed by reactivation of latency phase to active TB lesion.

    Manifestations of TB

    • Pulmonary TB: Fever, weight loss, chronic cough, haemoptysis, night sweats, and finger clubbing.
    • Extra-pulmonary forms: TB meningitis, renal TB, disseminated TB, etc.

    Management of TB

    • DOTS strategy: Directly observed treatment, short course, using a combination of antibiotics.

    Laboratory Diagnosis of TB

    • Smear microscopy: Acid-fast staining, using Ziehl-Neelsen or auramine staining.
    • Culture: Isolation of the organism from clinical specimens, using solid or liquid media.
    • Growth-based detection: Using automated BACTEC MGIT 960 TB system.
    • Line probe assay (LPA): Rapid detection of MTBC and drug resistance.
    • Gene Xpert/Rif: Point of care diagnostic tool.### TB Diagnosis and Treatment
    • PCR-based machine used for rapid diagnosis of TB, especially in HIV co-infected patients
    • Detects rifampicin resistance, which is an indicator of MDR-TB in about 90% of cases
    • DOTS (Directly Observed Treatment, Short-course) centers and ART clinics must collaborate
    • Treatment divided into two phases:
      • Initial phase: combination therapy for 2 months based on DOTS (Isoniazid, Rifampicin, Ethambutol, Pyrazinamide) to render patient non-infectious
      • Continuation phase: use of Isoniazid and Rifampicin for additional 6 months to kill remnant bacilli and prevent relapse or development of resistant strains

    Complications of TB

    • Development of resistant strains: MDR-TB, XDR-TB, and TDR-TB
      • MDR-TB: resistant to Isoniazid and Rifampicin
      • XDR-TB: resistant to MDR-TB and second-line drugs, quinolone, and injectable antibiotics
      • TDR-TB: resistant to all known anti-TB drugs
    • Miliary TB

    Prevention and Control of TB

    • Good and well-ventilated housing
    • Well-balanced nutrition
    • Immunization at birth with BCG (Bacille Calmette-Guérin)
    • Adequate treatment of infectious cases

    Leprosy

    • Chronic infectious disease caused by Mycobacterium leprae
    • Mainly affects skin, peripheral nerves, mucosa of the upper respiratory tract, and eyes
    • Two forms: Tuberculoid leprosy and Lepromatous leprosy
    • Transmitted via droplets from the nose and mouth during close and frequent contacts with untreated cases

    Pathology of Leprosy

    • Two extremes of cases: Tuberculoid leprosy (good cell-mediated immunity, few bacterial loads, and unaffected nerves) and Lepromatous leprosy (low cell-mediated immunity, heavy bacterial load, and affected nerves)

    Diagnosis of Leprosy

    • Diagnosis made clinically, although laboratory testing can be important in some cases
    • Health workers trained to diagnose leprosy based on finding at least one of three cardinal signs:
      • One or more hypo-pigmented, anaesthetic skin patches
      • One or more thickened peripheral nerves
      • A positive skin smear
    • Most accurate way to diagnose leprosy is tissue biopsy
    • Development of new diagnostic tests for leprosy is a global research priority

    Treatment of Leprosy

    • A blend of drugs known as Multi-Drug Therapy (MDT) is effective in killing all known strains of leprosy bacteria
    • MDT given to patients for 6 months to 2 years, depending on the severity and progression of the disease

    Buruli Ulcer

    • Caused by Mycobacterium ulcerans
    • Presents as ulcers at the extremities, especially feet
    • Mainly seen in areas with poor environmental sanitation

    Streptococci

    • Gram-positive spherical bacteria that form pairs or chains during growth
    • Catalase negative, non-sporing, non-motile, and facultative anaerobes
    • Complex nutritional requirements (blood or serum enriched media)

    Classifications of Streptococci

    • Alpha-hemolytic (incomplete lysis of RBCs with reduction of Hb and formation of green pigment around bacterial growth)
    • Beta-hemolytic (complete disruption of RBCs with clearing of blood around bacterial growth)
    • Non-hemolytic (some are non-hemolytic)

    Streptococcus pyogenes

    • Consists of Lancefield group A Streptococci
    • Associated with infections in man and causes a wide range of suppurative infections in the respiratory tract, skin, and life-threatening soft tissue infections
    • Associated with non-suppurative sequelae due to adverse immunological reactions

    Virulence Factors of Streptococcus pyogenes

    • Adhesion: interactions with F-proteins and fibronectin of the host tissue mediate adherence and internalization of the bacteria
    • M Protein: appears as hair-like projections of the streptococcal cell wall, anti-phagocytic, and immunogenic
    • Capsules: some strains form a capsule composed of hyaluronic acid
    • Toxins and enzymes: streptokinase, deoxyribonucleases, hyaluronidase, and streptococcal pyrogenic exotoxins (SPEs)

    Pathogenic Pathways of Streptococcus pyogenes

    • The organism enters via the respiratory tract and/or skin breach
    • Non-invasive infections: pharyngitis, scarlet fever, and skin infections
    • Invasive soft tissue infections: necrotizing fasciitis, streptococcal toxic shock syndrome, and bacteremia
    • Non-suppurative sequelae: rheumatic fever and acute glomerulonephritis

    Laboratory Diagnosis of Streptococcus pyogenes

    • Specimens collection: sputum, CSF, blood, synovial fluid, and laryngeal swab
    • Gram stain: gram-positive cocci in chains
    • Culture on standard laboratory media: growth is inhibited by bacitracin
    • Pharyngitis: rapid antigen detection test (RADT) is specific for Streptococcus pyogenes and immunologically detects group A carbohydrate antigen

    Identification of Streptococcus pyogenes

    • Catalase test: Streptococcus pyogenes is catalase negative
    • Bacitracin sensitivity test: Streptococcus pyogenes is sensitive to bacitracin

    Treatment of Streptococcus pyogenes

    • Penicillin G, Penicillin V, and Penicillinase-resistant penicillin
    • Following rheumatic fever: patients are placed on continuous prophylactic antibiotics to prevent repeat strep throat infection
    • For invasive S.pyogenes infections: consider adding Clindamycin

    Other Streptococci

    • Streptococcus agalactiae (Group B): β-hemolytic, and part of normal vaginal flora and lower GIT in 5-30% of women
    • Streptococcus C and G: share some virulence properties with Streptococcus pyogenes
    • Enterococci: group D Streptococci, normal colonists of human large intestine, and cause opportunistic urinary, wound, and skin infections
    • Viridans Group: large complex group, normal residents of the gums and teeth, oral cavity, and also found in nasopharynx, genital tract, and skin### Bacitracin Disk Test
    • Inoculate Blood Agar Plate (BAP) with a heavy suspension of the tested organism
    • Apply a Bacitracin disk (0.04 U) to the inoculated BAP
    • The presence of a zone of inhibition around the disk indicates susceptibility to Bacitracin

    CAMP Test

    • Group B streptococci (S.agalactiae) produce an extracellular protein called CAMP factor
    • CAMP factor acts synergistically with staphylococcal β-lysin to cause lysis of Red Blood Cells (RBCs)
    • The test involves streaking the Streptococcus to be tested and Staphylococcus aureus perpendicular to each other, with a 3-5 mm distance between the two streaks
    • A positive result appears as an arrowhead-shaped zone of complete hemolysis
    • S.agalactiae is CAMP test positive, while non-group B streptococci are negative

    Optochin Susceptibility Test

    • The Optochin (OP) test is a presumptive test used to identify Streptococcus pneumoniae (S.pneumoniae)
    • S.pneumoniae is inhibited by the Optochin reagent

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    Description

    This quiz covers the definition, aetiological agent, pathogenesis, clinical manifestations, laboratory diagnosis, treatment, and complications of typhoid fever, a type of septicaemic illness. It's an important topic in medical microbiology and parasitology.

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