Embed Size (px)
Citation preview
SalmonellaEssential learning for Medical Students
Dr.T.V.Rao MD
Dr.T.V.Rao MD 1
Salmonella• Causes Infections in Humans and
vertebrates,• Enteric Fever ( Typhoid fever )• Gastroenteritis• Septicemias,• Carrier state a concern
Dr.T.V.Rao MD 2
Salmonella • A Very complex group• Contains more > 2,500 spp• Typed on the basis of Serotyping, and species
typing• Divided into two groups 1 Enteric fever group 2 Food poisoning group – 3 Septicemias
Dr.T.V.Rao MD 3
Key points
• There are more than 2500 different antigenic types of Salmonella; those pathogenic to man are serotypes of S. enterica.
• Most serotypes of S. enterica cause food-borne gastroenteritis and have animal reservoirs.
• S. enterica serotypes Typhi and Paratyphi cause typhoid fever.
Dr.T.V.Rao MD 4
Enteric FeverTyphoid Fever
• Caused by Salmonella typhi, and other Groups called as Paratyphoid A, B, C
• Salmonella typhi - Causes Typhoid• Salmonella Paratyphi A,B,C Causes Paratyphoid
fevers.• Food Poison group• Spread from Animals – Humans • Causes Gastroenteritis – Septicemias,
Localized InfectionDr.T.V.Rao MD 5
Salmonella typhi• The bacterium Salmonella typhi is
present only in human beings and is transmitted through contaminated food or water. People with this infection carry the bacterium in their intestines and bloodstream, and those who have recovered from the disease could still have the bacterium in their system; they are known as ‘carriers’ of the disease. Both ill people and carriers shed Salmonella typhi in their stool
Dr.T.V.Rao MD 6
Food handlers spread the infection
• Both ill people and carriers shed Salmonella typhi in their stool
• Infection is usually spread when food or water is handled by a person who is shedding the bacterium or if sewage water leaks into drinking water or food that is then consumed..
Dr.T.V.Rao MD 7
Typhoid fevers are prevalent in many regions in the World
Typhoid Mary Most Dangerous Woman in America
Dr.T.V.Rao MD 9
Typhoid Mary
• A famous example is “Typhoid” Mary Mallon, who was a food handler responsible for infecting at least 78 people, killing 5. These highly infectious carriers pose a great risk to public health.
Typhoid Mary• "Typhoid Mary," real name Mary Mallon,
worked as a cook in New York City in the early 1900s. Public health pioneer Sara Josephine Baker, MD, PhD tracked her down after discovering that she was the common link among many people who had become ill from typhoid fever She was traced to typhoid outbreaks a second time so she was put in prison again where she lived until she died.
French physician Pierre Charles Alexandre Louis first proposed the name “typhoid fever”
William Wood Gerhard who was the first to differentiate clearly between typhus fever and typhoid in 1837.
Carl Joseph Eberth who discovered the typhoid bacillus in 1880.
Georges Widal who described the ‘Widal agglutination reaction’ of the blood in 1896.
Morphology of Salmonella
• Gram negative bacilli
• 1-3 / 0.5 microns,
• Motile by peritrichous flagella
Dr.T.V.Rao MD 14
S.typhi with Flagella
Dr.T.V.Rao MD 15
Bacteriology –Typhoid fever
• The Genus Salmonella belong to Enterobacteriaceae
• Facultative anaerobe• Gram negative bacilli• Distinguished from
other bacteria by Biochemical and antigen structure
Dr.T.V.Rao MD 16
Different types of Salmonella
I - entericaII - salamaeIIIa -arizonaeIIIb -diarizonaeIV - houtenaeV - bongoriVI - indica
Cultural Characters • Aerobic / Facultatively anaerobic• Grows on simple media – Nutrient agar,• Temp 15 – 41ºc / 37º c• Colonies appear as large 2 -3 mm, circular, low
convex,• On MacConkey medium appear Colorless ( NLF )Selective Medium - Wilson Blair Bismuth sulphide
medium. Produce Jet black colonies H2 S produced by Salmonella typhi
Dr.T.V.Rao MD 18
Enrichment MediumLiquid Medium
• Selenite F medium• Tetrathionate broth • Above medium are used for
isolation of Salmonella from contaminated specimens
• Particularly stool specimens..Dr.T.V.Rao MD 19
Identifying Enteric Organisms
• Isolates which are Non lactose fermenting • Motile, Indole negative• Urease negative• Ferment Glucose,Mannitol,Maltose• Do not ferment Lactose, Sucrose• Typhoid bacilli are anaerogenic• Some of the Paratyphoid form acid and gas• Further identification done by slide
agglutination testsDr.T.V.Rao MD 20
Biochemical Characters • Glucose ,Mannitol ,Maltose produce A/G• Salmonella typhi do not produce gas• Lactose/Salicin/sucrose not fermented.• Indole –• Methyl Red +• V P -• Citrate +• Urea –• H2S – produced by Salmonella typhi• Paratyphi A do not produce H2S
Dr.T.V.Rao MD 21
Resistance of Salmonella
• 55º c – 1 hour• 60º c – 15 MT• Boiling ,Chlorination,
Pasteurization Destroy the Bacilli.
Dr.T.V.Rao MD 22
SalmonellaAntigenic Structure
• H – Flagellar antigens• O – Somatic antigen,• Vi – Surface antigen in some species only• H antigens also called flagellar antigens, heat
labile protein,• Boiling destroys antigenicity• When mixed with Antiserum produces agglutination
and fluffy clumps are produced• H antigens are strongly immunogenic Induces
antibodies rapidly,
Dr.T.V.Rao MD 23
Antigenic structure of Salmonella
• Two sets of antigens• Detection by serotyping• 1 Somatic or 0 Antigens contain long
chain polysaccharides ( LPS ) comprises of heat stable polysaccharide commonly.
•
Dr.T.V.Rao MD 24
Flagellar Antigens • Flagellar or H Antigens are strongly
immunogenic and induces antibody formation rapidly and in high titers following infection or immunization. The flagellar antigen is of a dual nature, occurring in one of the two phases.
•
Dr.T.V.Rao MD 25
Antigens – Salmonella ( cont )
Dr.T.V.Rao MD 26
• O Antigens • Forms integral part of Cell wall,• Like Endotoxin• 0 Antigens unaffected by boiling.• When mixed with antiserum produce chalky
clumps are formed, take more time reaction, at high temp 50º – 55º c
• O antigens are less immunogenic. than H antigens
Antigen (Vi) – Salmonella ( contd )• Vi antigens • Many strains in S.typhi covers the O antigens-
prevents agglutination.• Resembles like K antigens • Destroyed after boiling at 60º c / 1 hour.• Vi a polysaccharide • Acts as virulence factor, protects the bacilli against
Phagocytosis and activity of Complement• Poorly immunogenic• Low titer of antibodies are produced, Not diagnostic
Dr.T.V.Rao MD 27
Classification of Salmonella
• Classified on the basis of Kauffmann-White Scheme
• Structure of 0 and H antigens are taken into consideration,
• More than 2000 species characterized.
Dr.T.V.Rao MD 28
Kauffmann – White scheme• Serotype 0 antigens H antigens Phase 1 21.Typhi 9,12,(Vi) d 1,22 Paratyphi A 1,2.12 a -3 Paratyphi B 1,4,5,12 b 1,24 Typhimuruim 1,4,5,12 I 1,75 Enteritidis 1,9,12 g m 1,2
Dr.T.V.Rao MD 29
Antigenic Variation in Salmonella
• May be phenotypic / Genotypic• H to O = loss of Flagella May be phase variation from I to II V to W variation S to R variation
Dr.T.V.Rao MD 30
Pathogenicity • Salmonella are definite parasites to
humans.• Eg S.typhi.• S.paratyphi A, B ,C• Other groups Salmonella • The important clinical syndromes 1. Enteric fever, Septicemias,
gastroenteritis.Dr.T.V.Rao MD 31
Enteric Fever: S. typhi• Ileocecal penetration• intraluminal multiplication• mononuclear response (macrophages)• Salmonella remains alive• 2nd week - lymphoid hyperplasia (mesenteric
lymph nodes)• back to bowel
Enteric FeverTyphoid
• Typhoid – caused by S.typhi• Paratyphoid Caused by
Paratyphi A,B,C• Typhoid --- Like Typhus• Infective dose ID50 / 107,
Dr.T.V.Rao MD 33
Fever• All the events coincides with Fever and other
signs of clinical illness• From Gall bladder further invasion occurs in
intestines• Involvement of peyr’s patches, gut lymphoid
tissue• Lead to inflammatory reaction, and infiltration
with monocular cells• Leads to Necrosis, Sloughing and formation of
chacterstic typhoid ulcers
Typhoid fever
Rashes in Typhoid• May present with rash,
rose spots 2 -4 mm in diameter raised discrete irregular blanching pink maculae's found in front of chest
• Appear in crops of upto a dozen at a time
• Fade after 3 – 4 days
Dr.T.V.Rao MD 37
Events in a Typical typhoid Fever
Dr.T.V.Rao MD 38
Pathology and Pathogenesis
• Bacilli enter through ingestion,• Bacilli attach to Microvilli,ileal mucosa,
penetrate to Lamina propria and sub mucosa • Phagocytosis by Polymorphs and
Macrophages• Enters the mesenteric lymph nodes • Enter the thoracic duct – Blood stream
Dr.T.V.Rao MD 39
Infective Dose
• For human infections, the number of bacteria that must be swallowed in order to cause infection is uncertain and varies with the serotype. In most of these the median infective dose for most serotypes, including Typhi, has varied from 106 to 109 viable organisms.
Dr.T.V.Rao MD 40
Pathology and Pathogenesis
• Bacteremia Spread to Liver, Gall bladder, Spleen, Bone marrow, Lymph nodes, Lungs, Multiply in kidneys
Once again spill into Blood streamCauses clinical illness.
Dr.T.V.Rao MD 41
Ingestion of contaminated food or water
Salmonella bacteria
Invade small intestine and enter the bloodstream
Carried by white blood cells in the liver, spleen, and bone marrow
Multiply and reenter the bloodstream
Pathology and Pathogenesis• Multiply abundantly in Gall bladder,• Bile rich source of Bacteria • Spill into Intestine, infects payers patches,
Lymph follicles • Inflammation – Undergo necrosis, Slough off• Typhoid ulcers• Typhoid ulcers can cause perforation and
hemorrhage • Duration of Illness 3 – 4 weeks• Incubation 7 -14, ( 3-56 days )
Dr.T.V.Rao MD 43
What is Enteric Fever Typhoid Fever
• Enteric fever is caused by strains of S. Typhi or S. Paratyphi A, B or C; although S. Paratyphi B, which gene sequence analysis suggests is a variant of S. Java, is more likely to cause non-typhoidal diarrhoea.
Dr.T.V.Rao MD 44
S.typhi more serious• The clinical features tend to be more
severe with S. Typhi (typhoid fever). After penetration of the ileal mucosa the organisms pass via the lymphatic's to the mesenteric lymph nodes, whence after a period of multiplication they invade the bloodstream via the thoracic duct.
Dr.T.V.Rao MD 45
Manifest with
Rose spots
High fever
Diarrhea
Typhoid Meningitis
Aches and pains
Chest congestion
Symptoms• No symptoms - if only a mild exposure; some people become "carriers" of
typhoid. • Poor appetite, • Headaches, • Generalized aches and pains, • Fever, Lethargy, Lethargy, • Lethargy, • Diarrhea,• Have a sustained fever as high as 103 to 104 degrees Fahrenheit (39 to 40
degrees Celsius),• Chest congestion develops in many patients, and abdominal pain and
discomfort are common,• Constipation, mild vomiting, slow heartbeat.
Progress in Enteric Fever• The liver, gall bladder, spleen, kidney and bone
marrow become infected during this primary bacteraemic phase in the first 7-10 days of the incubation period. After multiplication in these organs, bacilli pass into the blood, causing a second and heavier bacteraemia, the onset of which approximately coincides with that of fever and other signs of clinical illness.
Dr.T.V.Rao MD 48
Progress in Enteric Fever
• From the gall bladder, a further invasion of the intestine results. Peyer's patches and other gut lymphoid tissues become involved in an inflammatory reaction, and infiltration with mononuclear cells, followed by necrosis, sloughing and the formation of characteristic typhoid ulcers occurs.
Dr.T.V.Rao MD 49
Immunity in Typhoid
• Typhoid bacilli are Intracellular pathogens
• Cell mediated immunity is crucial
Dr.T.V.Rao MD 50
Early symptoms of Typhoid Fever
• The incubation period is usually 1-2 weeks, and the duration of the illness is about 3-4 weeks. Symptoms include:
• Poor appetite• Headaches• Generalized aches and pains• Fever as high as 104 degrees Farenheit• Lethargy• Diarrhea
Dr.T.V.Rao MD 51
Diarrhea Nausea Vomiting Stomach pain Headache Fever Onset 12-72 hours after
infection
Clinical manifestation• Head ache, malise,anorexia ,coated tongue • Abdominal discomfort,• Constipation / Diarrhea • Step ladder type fever,• Relative bradycardia,• A soft palpable spleen• Hepatomegaly• Rose spots appear
Dr.T.V.Rao MD 53
Events in a Typical typhoid Fever
Dr.T.V.Rao MD 54
Complications of Enteric fever
• Intestinal perforation,• Hemorrhage,• Circulatory collapse.• Bronchitis Bronchopneumonia,• Meningitis,• Cholecystitis,• Arthritis,Periostitis / Nephritis,• Osteomyletis,
Dr.T.V.Rao MD 55
Relapses in Typhoid Fever
• Apparent recovery can be followed by relapse in 5-10% of untreated cases. Relapse is usually shorter and of milder character than the initial illness, but can be severe and may be fatal. Severe intestinal haemorrhage and intestinal perforation are serious complications that can occur at any stage of the illness.
Dr.T.V.Rao MD 56
Other complications• Causes relapses in
particular to patients treated with chloramphenicol.
• S.paratyphi produce septicemias.
Dr.T.V.Rao MD 57
Typhoid carriers • Salmonella enterica causes
approximately 16 million cases of typhoid fever worldwide, killing around 500,000 per year. One in thirty of the survivors, however, become carriers. In carriers the bacteria remain hidden inside cells and the gall bladder, causing new infections as they are shed from an apparently healthy host.
Carriers may be Carriers may be temporary or chronic. Temporary (convalescent or incubatory)
carriers usually excrete bacilli up to 6-8 weeks. By the end of one year, 3-4 per cent of cases continue to excrete typhoid bacilli.
Persons who excrete the bacilli for more than a year after a clinical attack are called chronic carriers.
Carrier Stage in Typhoid Fever• Most people infected with salmonella
continue to excrete the organism in their stools for days or weeks after complete clinical recovery, but eventual clearance of the bacteria from the body is usual. A few patients continue to excrete the salmonellae for prolonged periods. The term chronic carrier is reserved for those who excrete salmonellae for a year or more.
Dr.T.V.Rao MD 60
Carrier Stage in Typhoid Fever• Chronic carriage can follow symptomatic
illness or may be the only manifestation of infection. It can occur with any serotype, but is a particularly important feature of enteric fever: up to 5% of convalescents from typhoid and a smaller number of those who have recovered from paratyphoid fever become chronic carriers, many for a lifetime.
Dr.T.V.Rao MD 61
Carrier Stage in Typhoid Fever• The bacilli are most commonly present in
the gall bladder, less often in the urinary tract, and are shed in faeces and sometimes in urine. The long duration of the carrier state enables the enteric fever bacilli to survive in the community in non-epidemic times and to persist in small and relatively isolated communities.
Dr.T.V.Rao MD 62
Epidemiology• Developed countries - Controlled.• Water supply/ Sanitation /Economically
poor.• S.typhi and S.paratyphi are prevalent in India• Previously Typhi are more common
Paratyphoid A on raise.• Age 5 – 20 years, Sanitation
Dr.T.V.Rao MD 63
Epidemiology• Sanitation has great role• Source an active patient or a Carrier shed the
Bacilli.• Who are carriers. Convalescent carrier 3 weeks to 3 months Temporary carrier 3 months to 1 year Chronic carrier > 1 year,Women attain more carrier stage
Dr.T.V.Rao MD 64
Epidemiology (Contd)• Bacilli persist in the Gall bladder and kidney• Food handlers spread the infection• Cooks great role• S.typhi and S.paratyphi in humans• S.para B in Animals,• Typhoid spread through Water, Milk, FoodHIV patients potentially susceptible for Typhoid disease.
Dr.T.V.Rao MD 65
Dr.T.V.Rao MD 66
Bacteriological Diagnosis of Typhoid Fever
• Selective media, such as Deoxycholate-citrate agar or xylose-lysine Deoxycholate agar, are used for the isolation of salmonella bacteria from faeces. Fluid enrichment media, such as Tetrathionate or selenite broth, are also useful to detect small numbers of salmonellae in faeces, foods or environmental samples.
Dr.T.V.Rao MD 67
Bacteriological Diagnosis of Typhoid Fever
• Suspicious colonies from the culture plates are tested directly for the presence of Salmonella somatic (O) antigens by slide agglutination and subcultured to peptone water for the determination of flagellar (H) antigen structure and further biochemical analysis.
Dr.T.V.Rao MD 68
Bacteriological Diagnosis of Typhoid Fever
• A presumptive diagnosis of salmonellosis can often be made within 24 h of the receipt of a specimen, although confirmation may take another day, and formal identification of the serotype takes several more days. A negative report must await the result of enrichment cultures - at least 48 h.
Dr.T.V.Rao MD 69
How we Diagnose Typhoid Fever• Diagnosis is made by any blood, bone marrow or
stool cultures and with the Widal test (demonstration of salmonella antibodies against antigens O-somatic and H-flagellar ). In epidemics and less wealthy countries, after excluding malaria, dysentery or pneumonia, a therapeutic trial time with chloramphenicol is generally undertaken while awaiting the results of Widal test and cultures of the blood and stool.
Dr.T.V.Rao MD 70
Laboratory Diagnosis ofTyphoid Fever
• 1 Isolation of Bacilli. A Gold standard • 2 Diagnosis for presence of Antibodies,• Positive Blood culture – A gold standard• Isolation from Feces and Urine ?• Detection of Antibodies Inconclusive.• Newer methods Detection of antigen in Blood and Urine
Dr.T.V.Rao MD 71
Blood Culture1 st week Positive in 90 %2 nd week Positive in 75 %3 rd week Positive in 60 %> 3 weeks positive in 25 %Draw 5 – 10 cc of Blood by venipuncture. ADD to 50 -100 ml of Bile broth.Incubate at 37 c /Subculture in MacConkey At regular intervals
Dr.T.V.Rao MD 72
Blood Cultures in Typhoid Fevers• Bacteremia occurs early
in the disease • Blood Cultures are
positive in 1st week in 90%2nd week in 75%3rd week in 60%4th week and later in 25%
Dr.T.V.Rao MD 73
Castaneda’s method ofBlood Culture
• Double medium used Solid/Liquid medium in the same Bottle.
• Bottle contains Bile broth/agar slant,• For subculture the bottle is merely tilted.• A subculture into MacConkey at regular
intervals,• Reduces the chances of contamination• Increases the chances of isolation.
Dr.T.V.Rao MD 74
Salmonella on Mac Conkey's agar
Dr.T.V.Rao MD 75
Salmonella on XLD agar
Dr.T.V.Rao MD 76
Clot culture• Clot cultures are more
productive in yielding better results in isolation.
• A blood after clotting, the clot is lysed with Streptokinase ,but expensive to perform in developing countries.
Dr.T.V.Rao MD 77
Bactec and Radiometric based methods are in recent use
• Bactek methods in isolation of Salmonella is a rapid and sensitive method in early diagnosis of Enteric fever.
• Many Microbiology Diagnostic Laboratories are upgrading to Bactek methods
Dr.T.V.Rao MD 78
Biochemical Characters
• Non Lactose fermenter,• Motile• Indole – MR + VP - Citrate +• Ferment Glu/Mal/Man• Do not ferment Lactose/Sucrose
Dr.T.V.Rao MD 79
Slide agglutination tests• In slide agglutination
tests a known serum and unknown culture isolate is mixed, clumping occurs within few minutes
• Commercial sera are available for detection of A, B,C1,C2,D, and E.
Dr.T.V.Rao MD 80
Culturing other Specimens
• Feces Enrichment in Tetrathionate broth and Selenite broth
• Culturing in MacConkey/DCA/Wilson Blair medium – Large black colonies.
• Urine Culture – positive in 25 % • Other samples Bone Marrow,Bile,CSF/Sputum
Dr.T.V.Rao MD 81
Serology• WIDAL Test – Tube agglutination test.• Detects O and H antibodies• Diagnosis of Typhoid and Paratyphoid• Testing for H agglutinins in Dryers tubes, a
narrow tube floccules at the bottom• Testing for O agglutinins in Felix tubes, Chalky • Incubated at 37º c overnight
Dr.T.V.Rao MD 82
Widal Test• In 1896 Widal A professor of
pathology and internal medicine at the University of Paris (1911–29), he developed a procedure for diagnosing typhoid fever based on the fact that antibodies in the blood of an infected individual cause the bacteria to bind together into clumps (the Widal reaction).
Dr.T.V.Rao MD 83
Widal test• S.typhi O and H tubes• Paratyphi A/B H agglutinins only• Common antigens O in all Factor sharing
12• Significance • I st week negative.• Titers raise in 2nd week Raise of titers
diagnosticDr.T.V.Rao MD 84
Diagnosis of Enteric FeverWidal test
• Serum agglutinins raise abruptly during the 2nd or 3rd week
• The Widal test detects antibodies against O and H antigens
• Two serum specimens obtained at intervals of 7 – 10 days to read the raise of antibodies.
• Serial dilutions on unknown sera are tested against the antigens for respective Salmonella
• False positives and False negative limits the utility of the test
• The interpretative criteria when single serum specimens are tested vary
• Cross reactions limits the specificity
Widal Test• Single test not diagnostic.• Paired samples tests• Diagnostic. O > 1 in 80 H > 1in 160H agglutinins appear firstFalse positives in Unapparent infection, Immunization Previously infected
Dr.T.V.Rao MD 86
Widal test• Anamnestic response previous
infection and responding to unrelated infection
• Other Diagnostic tests CIE and ELISADetection of Circulating antigensCo agglutination test.
Dr.T.V.Rao MD 87
Limitation of Widal Test• The Widal test is time
consuming and often times when diagnosis is reached it is too late to start an antibiotic regimen.
• In spite of several limitation many Physicians depend on Widal Test
Dr.T.V.Rao MD 88
False Positive and Negative Reactions with WIDAL Test
• The Widal test should be interpreted in the light of baseline titers in a healthy local population. This is especially important when there is a high local prevalence of non-typhoid salmonellosis. The Widal test may be falsely positive in patients who have had previous vaccination or infection with S typhi.
Dr.T.V.Rao MD 89
False Positive and Negative Reactions with WIDAL Test
• Widal titers have also been reported in association with the dysgammaglobulinaemia of chronic active hepatitis and other autoimmune diseases.64 '8 '9 False negative results may be associated with early treatment, with "hidden organisms" in bone and joints, and with relapses of typhoid fever. Occasionally the infecting strains are poorly immunogenic.
Dr.T.V.Rao MD 90
Diagnosis of Carriers and Environments
• Fecal carriers by isolation from specimens. or Bile aspirated.
• Sewer swabs• Bacteriophage
typing
Dr.T.V.Rao MD 91
Prophylaxis • TAB vaccine S.typhi 1,000 millions S Paratyphi A,B 750 millions. Injected subcutaneously 0.5 ml at 4 – 6 weeks.Live Oral Vaccine TyphoralMutant S.typhi strain Ty 2 1a Lacking enzyme UDP
galctose 4 epimerase 10 to9Viable bacilliGiven orally 1 – 3 – 5 days
Dr.T.V.Rao MD 92
Key points• Antibiotics have no place in the
management of salmonella gastroenteritis unless invasive complications are suspected.
• Clean water, sanitation and hygienic handling of foodstuffs are the keys to prevention.
Dr.T.V.Rao MD 93
Prevention• Vi Polysaccharide vaccine
– Administered subcutaneously or intramuscular– Confers protection seven days after injection– Approximately 50% efficacy after three years
• Ty 21 vaccine – Live attenuated strain of S. typhi– Administered orally in capsule form– Also available in liquid form which can be taken by
children as young as two years of age
Vaccines • An Inject able vaccine Typhium Vi• Contains purified Vi polysaccharide
antigen from S.typhi strain Ty2• A single dose, subcutaneous route • Given to children > 5 years• Immunity lasts for 2- 3 years.• Follow a booster
Dr.T.V.Rao MD 95
Treatment
• Chloramphenicol 1948 /1970 resistance.• Other Important drugs Ampicillin Amoxicillin, Furazolidine Cotromoxazole Chloramphenical resistance /Mexico Kerala
Dr.T.V.Rao MD 96
Antimicrobial Therapy in Typhoid• With prompt antibiotic therapy, more than
99% of the people with typhoid fever are cured, although convalescence may last several months. The antibiotic chloramphenicol Some Trade Names CHLOROMYCETINis used worldwide, but increasing resistance to it has prompted the use of other antibiotics BACTRIMSEPTRANor ciprofloxacin
Other Drugs• Fluroquinolones Ciprofloxacillin,
Pefloxacillin Ofloxacillin
Ceftazidime Ceftriaxone / Cefotoxaime
Dr.T.V.Rao MD 98
Coalition against Typhoid• Since May 2011, the
Coalition against Typhoid (CaT) has featured monthly articles in the WHO’s Global Immunization Newsletters (GIN). The articles, written by CaT members from around the world, highlight important work being done to accelerate adoption of typhoid vaccines.
Dr.T.V.Rao MD 99
Salmonella • WHO: 1,400,000 instances of salmonellosis in
USA• Salmonella costs per year US $3,000,000,000• 2,300 serotypes (S. enterica Typhimurium,
etc)– wide host range (humans, cattle, horses,
rodents, cats, dogs, birds, reptiles)• Multi-drug resistant S.e.Typhimurium DT104
101
Salmonella • Most common diseases caused by Salmonella:• gastroenteritis (self-limiting, 2-5 days)• enteric/typhoid fever (incubation 1-10/7-14
days, lasts 2-3 wks)• septicemia (incubation12-36 hrs, may lead to
chronic infection)• symptoms and disease manifestation differ in
hosts
Food Poisoning• The laboratory diagnosis of bacterial
food poisoning depends on isolation of the causal organism from samples of faeces or suspected foodstuffs. The more common food-poisoning serotypes, such as Enteritidis or Typhimuruim, may be characterized more fully by phage typing and antibiotic resistance typing (see above).
Dr.T.V.Rao MD 102
Salmonellosis• > 2000 known
serotypes• 200 serotypes are
detected each year in the United States
• Two most common (in most countries)– Salmonella Typhimurium
– Salmonella Enteritidis
Identification of pathogens
• Strains can be differentiated further by plasmid and pulsed-field gel electrophoresis typing so that the isolates from patients may be matched with those from the infected food and from a suspected animal source.
Dr.T.V.Rao MD 104
Salmonella Gastroenteritis• Zoonotic disease• S.enteritidis• S.typhimurium• S.halder• S. agana• S.indiana• Contaminated poultry, Meat Milk, Milk products.• Enters the shells of the Intact eggs – Chicken feed,
and Fecal droppings.
Dr.T.V.Rao MD 105
Nontyphoidal Salmonella
• General Incubation: 6 hrs-10 days; Duration: 2-7 days• Infective Dose = usually millions to billions of cells• Transmission occurs via contaminated food and water• Reservoir:
a) multiple animal reservoirsb) mainly from poultry and eggs (80% cases from eggs)c) fresh produce and exotic pets are also a source of contamination (> 90% of reptile stool contain salmonella bacterium); small turtles ban.
• General Symptoms: diarrhea with fever, abdominal cramps, nausea and sometimes vomiting
Dr.T.V.Rao MD 106
Mechanism of Pathogenicity Gastroenteritis
• ingestion• absorbed to brush border of epithelial cells of
small intestine and colon • migrate to lamina propria, Ileocecal• multiply in lymphoid follicles• Reticuloendothelial hyperplasia and
hypertrophy
Nontyphoidal Salmonella: Gastroenteritis
• Incubation: 8-48 hrs ; Duration: 3-7 days for diarrhea & 72 hrs. for fever
• Inoculum: large• Limited to GI tract• Symptoms include: diarrhea, nausea, abdominal cramps
and fevers of 100.5-102.2ºF. Also accompanied by loose, bloody stool; Pseudo appendicitis (rare)
• Stool culture will remain positive for 4-5 weeks• < 1% will become carriers
Dr.T.V.Rao MD 108
Nontyphoidal Salmonella:Bacteremia and Endovascular Infections
• 5% develop septicemia; 5-10% of septicemia patients develop localized infections
• Endocarditis: Salmonella often infect vascular sites; preexisting heart valve disease risk factor
• Arteritis: Elderly patients with a history of back/chest + prolonged fever or abdominal pain proceeding gastroenteritis are particularly at risk. - Both are rare, but can cause complications that may lead to death
Dr.T.V.Rao MD 109
Salmonella Gastroenteritis
• Can occur as cross infection• 24 hours• Manifest with Diarrhea, omitting• Abdominal pain mucous and blood in
stools• Last for 2 – 4 days• Some times may lead to septicemias
Dr.T.V.Rao MD 110
Diagnosis and Treatment
• Isolation by culturing
• Rarely need antibiotics.
• More frequent in Developed nations.
Dr.T.V.Rao MD 111
Salmonella septicemias• S.cholera suis• Deep abscess,
Endocarditis• Isolation from
Blood and Pus.• Chloramphenicol
highly effective
Dr.T.V.Rao MD 112
Don’t eat raw or undercooked food
Cross-contamination of foods should be avoided
Do not prepare food or pour water if you are infected with the bacteria
Wash hands, kitchen surfaces, and utensils with soap and water after they have come in contact with raw meat or poultry
Wash hands after contact with animal
feces
Avoid direct/indirect contact between reptiles and infants
Simple hand hygiene and washing can reduce several cases of Typhoid
• Program created by Dr.T.V.Rao MD for benefit of Medical and Paramedical Students in the
Developing World • Email
Dr.T.V.Rao MD 116
