Bacterial infections Diphtheria, Pertussis and Enteric fever. Dr Mubarak Abdelrahman Assistant Professor Jazan University

Transcription

1 Bacterial infections Diphtheria, Pertussis and Enteric fever Dr Mubarak Abdelrahman Assistant Professor Jazan University

2 Gram negative: Diplococci Bacilli Coccobacilli Gram Positive: Diplococci Chains Clusters Rods & cocobacilli

3 Diphtheria (Corynebacterium diphtheriae) An acute toxic infection caused by Corynebacterium diphtheriae A gram-positive bacilli.

4 Epidemiology C. diphtheriae : An exclusive inhabitant of human mucous membranes and skin. Spread by airborne respiratory droplets and direct contact. Can remain viable in dust for 6 months.

5 The exotoxin: Pathogenesis Inhibits protein synthesis and causes local tissue necrosis. In respiratory tract leads to pseudo-membrane. Absorption can lead to systemic manifestations: e.g. kidney tubule necrosis, thrombocytopenia, cardiomyopathy, demyelination of nerves,..

6 Clinical Manifestations The manifestations are influenced by: The anatomic site of infection. The immune status of the host. The production and distribution of the toxin.

7 Respiratory Tract Diphtheria Incubation period of 2-4 days (<7). Local signs and symptoms of inflammation. Soft tissue edema + enlarged lymph nodes causes a bull-neck appearance.

8 A B A: Bull neck B: pseudo membrane C: Skin diphtheria C

9 Diagnosis Differential diagnoses: - Epiglottitis. - Exudative pharyngitis caused by Streptococcus pyogenes or Epstein-Barr virus. Diagnosis: - Helped by the characteristic adherent membrane and relative lack of fever. - Specimens for culture from nose, throat and any other mucocutaneous lesion.

10 Complications Respiratory tract obstruction. Toxic cardiomyopathy In 10-25% of patients with respiratory diphtheria and is responsible for 50-60% of deaths. Toxic Neuropathy acutely or 2-3 weeks after onset of oropharyngeal inflammation: - Local paralysis: soft palate, pharynx, larynx,.. - Cranial neuropathies: oculomotor paralysis. - Symmetric polyneuropathy.

11 Specific antitoxin: Treatment Should be administered on the basis of clinical diagnosis. The antibiotics (Erythromycin or penicillin) - Stop toxin production. - Treat localized infection. - Prevent transmission of the organism to contacts. Supportive Care: - Bed rest is essential for 2 weeks (the period of risk for symptomatic cardiac damage).

12 Prevention Protection by immunization with toxoid. All contacts are: - Closely monitored through the incubation period. - Given Antimicrobial prophylaxis regardless of immunization status. Asymptomatic carriers also treated.

13 Pertussis (Bordetella pertussis and Bordetella parapertussis) Pertussis meaning intense cough. Also known as whooping cough. Etiology: by Bordetella organisms: - Gram-negative coccobacilli. - Colonize only ciliated epithelium.

14 Epidemiology Pertussis is extremely contagious. B. pertussis does not survive for prolonged periods in the environment. Chronic carriage by humans is not documented. Subclinical infection is around 80%. Neither natural disease nor vaccination provides complete or lifelong immunity.

15 Pathogenesis The exact mechanism of disease remains unknown. B. pertussis expresses pertussis toxin (PT) and other biologically active substances may be responsible for the local epithelial damage that produces respiratory symptoms and this facilitates absorption of PT.

16 Clinical Manifestations Incubation period 3-12 days. Classically divided into 3 stages: 1. The catarrhal stage (1-2 weeks) congestion, rhinorrhea, low-grade fever, sneezing, lacrimation,.. 2. The paroxysmal stage (2-6 weeks) the cough begins as dry, intermittent, irritative, paroxysmal followed by a loud whoop ± Post-tussive vomiting. 3. The convalescent stage ( 2 weeks) the number, severity and duration of episodes diminish.

17 Clinical Manifestations cont. Infants <3 months: - No classic stages. - Apnea may be the only symptom. - Cyanosis is common. - Sudden infant death. In non immunized infants: - Cough and whooping louder and more classic. Adolescents and previously immunized children: - Mild illness.

18 On physical examination: No signs of lower respiratory tract disease. Can be complicated by secondary pneumonia. Conjunctival hemorrhage. Petechiae on the upper body are common.

19 Diagnosis A clinical case definition of cough of 14 days duration with at least 1 associated symptom of paroxysms, whoop, or post-tussive vomiting. Absolute lymphocytosis is characteristic in the catarrhal stage. Diagnosis confirmed by: 1. Isolation of B. pertussis in nasopharyngeal swab culture (main). 2. Serologic tests for detection of antibodies to B. pertussis.

20 Complications 1. Apnea. 2. Secondary infections (otitis media, pneumonia,..). 3. Physical sequelae of forceful coughing e.g: - conjunctival hemorrhages. - epistaxis. - hemorrhage in the central nervous system. - pneumothorax. - umbilical and inguinal hernias. 4. Bronchiectasis has been reported.

21 Treatment Infants <3 months of age with suspected pertussis are always admitted to hospital. Antibiotics are always given when pertussis is suspected or confirmed. Macrolides are the preferred agents (erythromycin, Azithromycin) Isolation of patients and prophylaxis antibiotics to all contacts regardless of age or immunization.

22 Prevention Immunization with pertussis vaccine, beginning in infancy with periodic reinforcing doses through adolescence and adulthood.

23 Enteric Fever (Typhoid Fever) Etiology: Typhoid fever is caused by Salmonella Typhi and S. Paratyph, a gram-negative bacilli.

24 Epidemiology In developed countries, the incidence is <15 cases/100,000 population. In the developing world, estimated rates bet. 100 to 1,000 cases/100,000 population. The highest incidence, complications and hospitalization in children <5 years of age. Direct or indirect contact with an infected person (sick or chronic carrier) is a prerequisite for infection.

25 Pathogenesis After ingestion, S. typhi invade through the gut mucosa to mesenteric lymphoid system then into the bloodstream causing bacteremia. The incubation period 7-14 days; (3-30)days.

26 Clinical Features Mild illness (low-grade fever, malaise, dry cough). Severe (high-grade fever, generalized myalgia, abdominal pain, hepatosplenomegaly, anorexia,..). The classic stepladder rise of fever is relatively rare. In children, diarrhea may be followed by constipation. Rose spots: - Macular/maculopapular rash. - appear around the 7-10 th day of the illness. - on the lower chest and abdomen. - last 2-3 days.

27 Complications Hepatitis and cholecystitis. Intestinal hemorrhage and perforation. Toxic myocarditis. Neurologic complications (delirium, psychosis, Guillain-Barre syndrome..). Others: DIC, hemolytic-uremic syndrome, nephrotic syndrome, meningitis and suppurative lymphadenitis.

28 Differential Diagnosis Acute gastroenteritis, bronchitis, and bronchopneumonia. Malaria and sepsis with other bacterial pathogens. Tuberculosis, brucellosis, Dengue fever, acute hepatitis, infectious mononucleosis. Others (malignancies, rheumatological, )

29 Diagnosis The mainstay is by a positive culture. - Blood cultures early. - Stool and urine culture after the 1st wk. Leukocyte counts frequently low in relation to fever and toxicity. Thrombocytopenia: severe illness (may accompany DIC). Liver function test. Widal test but many false-positive and false-negative results. Other diagnostic tests: PCR and monoclonal antibodies. In the developing world the mainstay of diagnosis is clinical.

30 Treatment Supportive: adequate rest, hydration, correct fluid and electrolyte. Antipyretic therapy. A soft, easily digestible diet if no abdominal distention or ileus. Antibiotic therapy (chloramphenicol or amoxicillin quinolones or third-generation cephalosporin)

31 Prevention Good sanitation services and central chlorination of water. Avoid consumption of street foods! Hand washing. Vaccination: (two vaccines) 1. An oral, live-attenuated preparation of S. Typhi, from 6 years of age. 2. The Vi capsular polysaccharide for 2 years of age. Intramuscular with a booster every 2 years.