typhoid.pptx lecture in 4th yr medicine in homoeopathy

Typhoid Infectious disease lecture

1. TYPHOID

2. Typhoid fever is also called enteric fever.  It is caused by  Salmonella typhi  and  Salmonella paratyphi .  Enteric fever is a cumulative term that illustrates both typhoid and paratyphoid fever. Paratyphoid is clinically indistinct from typhoid fever; thus, enteric and typhoid fever are used mutually.  Typhoid fever is one of the major causes of mortality and morbidity in overcrowded and unhygienic areas The disease course ranges from early gastrointestinal distress to nonspecific systemic illness but ultimately may lead to multiple complications. Salmonella is said to spread by the 'four Fs" (flies, fingers, feces, fomites ). Fever characteristically comes in a step-wise pattern (i.e., rises and falls alternatively) followed by headache and abdominal pain.  

3. ETIOLOGY :- The main causative agent of typhoid fever is  Salmonella   typhi  and  Salmonella paratyphi , both are members of the Enterobacteriaceae family.  Salmonella  is a genus that has 2 species   Salmonella   enterica   serovar  and  enteritidis  classified through extensive analysis by multiplex quantitative polymerase chain reaction (PCR).  Both  Salmonella typhi  and  Salmonella paratyphi  (A, B, C) are  Salmonella   enterica  serotypes. Nontyphoidal salmonella (NTS) is more typical in children and is mostly limited to gastroenteritis.

4. Salmonella  is transmitted by the fecal-oral route through contaminated water, undercooked foods, fomites of infected patients, and is more common in areas with overcrowding, social chaos, and poor sanitation. It is only transmitted from an infected person to another person, as humans are its only host.  Normal flora of the gut is protective against the infection. The use of antibiotics such as streptomycin destroys the normal flora, which heightens its invasion. Malnutrition decreases normal gut flora and thus increases the susceptibility to this infection as well.

5. EPIDEMIOLOGY A cases each year since 2008, enteric fever remains an important cause of illness worldwide. Approximately 215,000 deaths result from over 26 million cases of typhoid fever and 5 million cases of paratyphoid infection each year worldwide. Salmonella  typhi  is more common than  Salmonella paratyphi ,  and  Salmonella paratyphi  A is more prevalent than  Salmonella paratyphi  B infections. Up to 4% of patients with typhoid fever go on to become chronic carriers.  These patients remain asymptomatic after their acute treatment, but they may excrete  Salmonella  for up to 1 year in their stool, or less frequently their urine.

6. PATHOGENESIS The pathogenesis of typhoid fever depends upon a number of factors, including infectious species, virulence, host's immunity, and infectious dose. The larger the infectious dose, the shorter the incubation period, and the higher the attack rate. Typhoid fever is more severe in debilitated and immunocompromised patients. Salmonella  is an acid-sensitive bacteria except for a few resistant strains, so typically it is destroyed in the stomach by gastric acid unless a large dose is ingested.  In patients with achlorhydria , intake of antacids and antihistamines, colonization of  Salmonella  occurs even with smaller doses. Food and beverages also act as buffers against gastric acid that facilitates bacteria reaching the small gut.

7. The virulence of  Salmonella  is determined by typhoid toxin, Vi antigen (polysaccharide capsule), liposaccharide O antigen, and flagellar H antigen. Strains positive for Vi antigen have an attack rate twice that of Vi negative strains, even for the same dose of micro-organisms . One of the main differences between  Salmonella  typhi  and non- typhoidal salmonella (NTS) is the presence of Vi antigen in  Salmonella   typhi  but absent in NTS . The main role of the Vi antigen is to act as an antiphagocytic agent preventing the action of macrophages, thus shielding the O antigen from antibodies that confer the serum resistance . The flagellar H antigen provides bacterial mobility and adherence upon the gut wall mucosa. Invasion of the gut wall is assisted by flagella .

8. Salmonella  also produces a molecule that stimulates the epithelial release of chemoattractant eicosanoid , which sequesters neutrophils into the lumen and potentiates mucosal damage . Bacteria induce proliferation of Payer patches via recruitment of lymphocytes and mononuclear cells and induce necrosis and eventually, ulceration that complicates the symptoms. Pathogens reach the reticuloendothelial system via both lymphatic system and bloodstream, including other multiple organs, most commonly gallbladder in almost all cases. The early bacteremic phase (24 hours to 72 hours) is asymptomatic and transient as these bacteria are phagocytosed by macrophages and monocytes in the reticuloendothelial system called primary bacteremia .

9. The capacity of pathogens to grow in these immune cells makes them characteristic, and intracellular multiplication of bacteria in the reticuloendothelial system enforces them to re-enter the bloodstream causing continuous bacteremia for several days and weeks known as secondary bacteremia . Secondary bacteremia is the phase in which disease symptoms manifest .  Like in other gram-negative bacteria, an endotoxin has an important role in the pathogenesis. The lipopolysaccharide induces the shock-like reaction, and endotoxemia leads to vascular hyperactivity and catecholamine release, which causes focal necrosis and hemorrhage .

10. HISTORY & PHYSICAL EXAMINATION:- Clinical presentations of both  Salmonella typhoid  and  Salmonella paratyphoid  are similar, though arthralgia is more common with typhoid . Incubation :- 10-14 days. Insidious onset Typhoid is an infectious disease that presents with nonspecific symptoms . Patients complain of enterocolitis after 12 hours to 48 hours of inoculation . Often, they initially present with nausea, vomiting that progresses to diffuse abdominal pain, bloating, anorexia, and diarrhea , which can vary from mild to severe diarrhea with or without blood, followed by a short asymptomatic phase that gives way to bacteremia and fever with flu-like symptoms . Enterocolitis is more prominent in  Salmonella   typhi .

11. Immunocompromised patients with HIV, particularly those with low CD4 counts, more commonly present with severe diarrhea and tend to have more serious metastatic infections . Classic typhoid fever starts about one week after the ingestion of the organism. Fever follows a “step-ladder” pattern (i.e., fever rises one day, falls the subsequent morning, and continues to form peaks and troughs with insidious onset). Drowsiness, headache, malaise and aching in limbs. Abdominal distress is frequently seen in typhoid fever. Due to the hypertrophy of Payer patches , nd swelling of lymphoid tissue around ileocecal region, constipation may predominate over diarrhea in some cases .

12. PHYSICAL EXAMINATION In the first week, a documented fever may be accompanied by a decreased heart rate.  In the second week, findings are more common, including abdominal distention. When typhoid is complicated by ileal perforation, tenderness, rigidity, and guarding of the abdomen may be present. Visible rose spots (rose-colored macules on the abdomen) are associated with typhoid fever but occur only rarely . The patient looks pale, mildly distressed, and dehydrated with sunken eyes, dry skin, and lethargy . Some patients have jaundice with yellowish skin and sclera, pale stool, and dark urine when the patient has associated gallstones and other biliary pathology .  Enlarged spleen on palpation may also be present.

13. If the diagnosis is delayed until the third week, the patient is more toxic, anorexic, and with notable weight loss. COMPLICATIONS:- Chances of bowel perforation increase with time, which worsens abdominal distension and peritonitis. The patient becomes tachypneic with crackles over the lung base on auscultation. Signs of metastatic complications appear .  Dry cough due to pneumonia can also be present as well as neck rigidity due to meningitis, or rarely, chest pain due to myocarditis and pericarditis .

14. FIRST WEEK END OF FIRST WEEK END OF 2 ND WEEK FEVER ROSE SPOTS ON TRUNK DELIRIUM HEADACHE SPLENOMEGALY COMPLICATIONS, COMA & DEATH MYALGIA COUGH RELATIVE BRADYCARDIA ABDOMINAL DISTENSION CONSTIPATION DIARRHOEA DIARRHOEA & VOMITING IN CHILDREN SYMPTOMS

15. PARATYPHOID FEVER:- Course tends to be shorter and milder than typhoid. Onset is often more with acute enteritis. Rash is more abundant and less GI symptoms.

16. EVALUATION The approach to typhoid patients should be clinical. Patients residing in areas with poor sanitation or impure drinking water or history of travel from endemic areas presenting with febrile illness for more than three days along with gastrointestinal manifestations (pain, constipation, or diarrhea) are highly suspicious . Diagnosis in the first week is difficult, but a variety of laboratory studies assist in making the diagnosis . NEUTROPENIA IN FIRST WEEK Blood culture:  Blood culture remains the primary mechanism of confirmation of a typhoid fever diagnosis . Blood cultures done during secondary bacteremia (i.e., clinical manifestations) are more reliable though 30% to 50% of cultures may be falsely negative depending on the technique and time series .

17. Stool culture:  Stool culture is less effective in the bacteremic phase of the disease. Stool culture is diagnostic in the second and third weeks . The sensitivity of stool culture depends upon the amount of stool sample taken and the duration of illness. Chronic carriers intermittently pass pathogens in the fecal matter for a long time so, several samples should be taken. Widal test:  The Widal test   is a serological test for enteric fever, which detects antibodies against O (surface) and H ( flagellar ) antigens. An antibody titer of greater than 1:160 and greater than 1:80 for anti-H antigen and anti-O antigen respectively are considered as cut off levels to predict recent infection of typhoid fever. When the convalescent titer is four times greater than the acute titer, the study is considered positive.

18. Polymerase chain reaction (PCR) Assay:   Polymerase Chain Reaction (PCR) can provide DNA-based gene identification of several serotypes such as the H antigen gene and O antigen gene .   Enzyme-Linked Immunosorbent Assay (ELISA ):   ELISA identifies antibodies to the capsular polysaccharide Vi antigens that may be helpful in identifying carriers but is rarely useful in acute illness.

19. MANAGEMENT:- Antibiotics Vaccine prophylaxis Miscellaneous treatment:  Symptomatic and supportive care is essential. Maintaining adequate hydration during diarrhea, as well as appropriate ventilation and oxygenation for pulmonary complications, should be provided along with analgesics and antipyretics as supportive care for metastatic complications. Corticosteroids have been suggested for severe cases with encephalitis . Surgery:  When gallstones accompany a carrier state, cholecystectomy can be curative. Surgical repair is indicated for complications, including peritonitis and ileal perforation . Prevention through sanitation : Epidemiological data reveals that typhoid is more prevalent in low and middle-income countries, in areas with poor drinking water, and lack of sanitation. Safe drinking water, sanitation, and avoidance of overcrowding contribute remarkably to the reduction in the number of cases.

20. HOMOEOPATHIC THERAPUTICS:- BAPTISIA BRYONIA COLCHICUM RHUS TOX PHOSPHROUS SULPHURIC ACID MURATIC ACID OPIUM