Enteric fever – part 3 – Paratyphoid fever, Salmonella paratyphi

Definition
- Salmonellae are flagellate, gram-negative bacteria that causes a self-limited disease that is food-borne and water-borne gastroenteritis or may cause life-threatening systemic disease caused by S. Typhi (Enteric fever or Typhoid fever).
- Salmonella paratyphi causes less severe disease than Salmonella typhi.
- Salmonella infections are divided into:
- Typhoidal infection caused by S.typhi and S.paratyphi.
- Salmonella paratyphi is also a type of Enteric fever.
- Non-typhoidal infection most common in the USA caused by:
- S.typhimurium.
- S. enteritidis.
- 95% of cases are food-born, and the rest are nosocomial infections.
- Salmonella is relatively uncommon in the USA; 70% are acquired from abroad.
- Humans are the only source of this infection, and the spread is from person to person or via contaminated foods or water.
Paratyphoid fever is caused by:
- S. paratyphi A.
- S. paratyphi, B.
- S. paratyphi, C.
Sample
- Samples are taken like typhoid fever.
- Blood complete examination.
- Stool for culture.
- Blood for culture.
- Urine for culture.
- For the culture, roughly 105 to 109 organisms are required, but this count may be low in infants and older adults.
- This count may be low in patients taking antacids and H2 receptor blockers.
Pathogenesis of Salmonella paratyphi infection:
- The incubation period is 6 to 30 days.
- This is caused by Salmonella enterica, which has serotypes of Paratyphi A, B, and C.
- The spread is eating or drinking contaminated water or food by the patient’s feces or the carrier.
- Humans are the only animals infected.
- Occasionally this may spread sexually.
- Most cases are due to Paratyphi A in comparison to Paratyphi B and C.
- Paratyphi B is more common in Europe.
- This will have S/S like typhoid fever.
- Diagnosis by isolation of the bacteria or antibodies (anti BH) in the widal test.
- Paratyphi C is a rare infection and is mostly seen in the Far East.
- It presents as septicemia with the formation of an abscess.
- Culture usually makes the diagnosis.
- These bacterias are internalized by the intestinal epithelial cells present over Peyer’s patches and are abundant in the ileum.
- These are transported to the peyer patches; from there, these bacteria enter the blood circulation.
- S.typhi often settles in the liver and biliary tree.
Signs and symptoms
- These are like typhoid fever.
- S/S are milder than typhoid fever.
- There are weaknesses and loss of appetite.
- Headache is quite common.
- Some patients may develop skin rashes that are rose-colored.
- Only 20% to 40% of the patient develops abdominal pain.
- The duration is shorter.
- There may be transient diarrhea and symptomless infection.
- Without treatment, S/S may persist for weeks or months.
- Carrier state is less common.
Lab Diagnosis
- CBC shows:
- Low TLC, leucopenia.
- Blood culture: This is the gold standard for the diagnosis.
- Positive in the first week of infection in 80% of the cases. But blood culture may reach 90% of the cases, decreasing to 50% in the third week.
- Blood culture is positive in 80% of the cases in the first week of infection.
- Blood culture is considered 100% specific.
- Buffy coat may decrease the time for isolation.
- This is subcultured on the MacConkey media.
- Bone marrow culture, if taken, will be positive and may have a high yield of up to 90% sensitivity.
- Stool culture will be a positive but not reliable test. This will be positive within the first 7 days of infection.
- This is negative in 60% to 70% of the cases during the first week if the patient is untreated, then positive in these patients in the third week.
- The chronic carrier may have stool culture positive even up to one year.
- Feces cultures on solid selective media:
- Desoxycholate citrate agar where there are non-lactose fermenting colonies.
- McConkey medium shows non-fermenting colonies.
- There is no gas and no fermentation of the sugar.
- Widal test will be positive after 7 to 10 days of infection.
- An agglutination test is done for flagellar H and somatic O antigen with antisera (Salmonella paratyphi A and B).
- Typhidot test claimed by the manufacturing companies that it would be positive after 2 to 3 days.
- The urine culture may be done and is positive in the case of enteric fever but is less sensitive.
- This is done on the MacConkey media.
- Bacteriophage typing is done to identify the different strains of S.typhi and also Paratyphi.
- This is useful for the epidemiological investigation in case of the source of the outbreak.
- Identification of S. paratyphi:
- Biochemical tests like there are no gas formation on the fermentation of the sugar.
- Blood culture and a urine culture can also identify these organisms.
- Serology shows H and O antisera positive tests.
- Bacteriophage typing identifies the different types of salmonella paratyphi.
Treatment:
- Ciprofloxacin and Co-trimoxazole can be given.
- The drug of choice is chloramphenicol but not used because of its complication.
- Treatment of carrier:
- The chronic carrier is less common but can be treated by ampicillin, chloramphenicol, ciprofloxacin.
- Ultimately can advise cholecystectomy.
- Control: The following methods can do this.
- Public health, including general hygiene, should be discussed with the public.
- The carrier should not be employed in the food industry. They should be taught public hygiene like washing hands, and clean water supply,
- Vaccination will also help to decrease the incidence of the disease.