Enterobacteriaceae.pptx

Overview on Enterobacteriaceae

1. Enterobacteriaceae Gram-Negative Rods Basic bacteriology 2021/1/23

2. Outlines Enterobacteriaceae : Overview I. Escherichia coli : General characteristics II. Salmonella : General characteristics III. Shigella : General characteristics IV. OTHER ENTEROBACTERIACEAE General Diagnosis

3. Enterobacteriaceae : Overview Are a large heterogeneous group of Gram-negative rods. Natural habitat is the human or animal intestinal. Many also have alternative habitats in soil or water. The family includes many genera. Are facultative anaerobes or aerobes. Ferment a wide range of carbohydrates. possess a complex antigenic Structure, and produce a variety of toxins.

4. Enterobacteriaceae : Overview Many as part of the normal flora . Grow well on MacConkey agar. Catalase positive. Oxidase negative (except for Plesiomonas ). Reduce nitrate to nitrite. Non spore forming. Motile And Non-Motile. Some has capsule. Some are nosocomial infections.

5. Enterobacteriaceae Disease Overview.

6. Enterobacteriaceae: Classification Gram-negative rods related to the enteric tract include a large number of genera. These genera have therefore been divided into three groups depending on the major anatomic location of disease, namely, pathogens both within and outside the enteric tract. pathogens primarily within the enteric tract. pathogens outside the enteric tract. Source of Site of Infection Enteric tract Genus Both within and outside Escherichia, Salmonella Primarily within Shigella, Vibrio, Campylobacter, Helicobacter Outside only Klebsiella–Enterobacter–Serratia group, Proteus- Pseudomonas, Bacteroides, Prevotella , Fusobacterium Providencia– Morganella group CHAPTER 18-levinson

7. Classification according biochemical characteristics Ewing grouped bacterial species with similar biochemical characteristics. Within the tribes.

8. Enterobacteriaceae: Classification Lippincot-ch12

9. Lactose fermented rapidly Escherichia coli: metallic sheen on differential media; motile; flat, nonviscous colonies Enterobacter aerogenes: raised colonies, no metallic sheen; often motile; more viscous growth Enterobacter cloacae: similar to Enterobacter aerogenes Klebsiella pneumoniae: very viscous, mucoid growth; nonmotile Lactose fermented slowly Edwardsiella , Serratia, Citrobacter, Salmonella Arizona subgroup, Erwinia, some strains of Shigella sonnei (on extended incubation) Lactose not fermented Shigella species: nonmotile; no gas from dextrose Salmonella species: motile; acid and usually gas from dextrose Proteus species: “swarming” on agar; urea rapidly hydrolyzed (smell of ammonia) Providencia species, other than P. stuartii Morganella species. Yersinia species Rapid, Presumptive Identification of Gram-Negative Enteric Bacteria- jawtez

10. I. Escherichia coli : General characteristics Escherichia  is the most important genus in Enterobacteriaceae and has many species, Escherichia coli (E.coli) is the most medical important species. Most used in applied b iotechnology . M otile  by peritrichous flagella. Habitat GI tract, is part of the normal flora. Facultative anaerobes. Has fimbriae or pili. Opportunistic pathogenic. Some species: E. albertii , E. fergusonii , E. hermannii E. marmotae , E. vulneris .

11. Functions of E.coli as normal flora Protects the intestinal tract from bactreial infection Produce our main source of vitamins B12 and K . Lives symbiotically. Aids in digestion.

12. Antigenic structure and Virulence factor 1. The O antigens : (somatic or cell wall antigens) are found on the polysaccharide portion of the LPS. These antigens are heat-stable , and may be shared among different Enterobacteriaceae genera. 2. The H antigens : are associated with flagella; therefore, only flagellated (motile)Enterobacteriaceae such as E. coli have H antigen. 3. The K antigen : are most often associated with the capsule or, less commonly, with the fimbriae . The antigenic classification of Enterobacteriaceae often indicates the presence of each specific antigen; for example, the antigenic formula of an E. coli may be O55:K5:H21

13. Enterobacteriaceae have a complex antigenic They are classified by more than 150 different heat-stable somatic O (lipopolysaccharide) antigens, more than 100 heat-labile K (capsular) antigens, more than 50 H (flagellar) antigens Antigenic structure Although each genus of Enterobacteriaceae is associated with specific O groups, a single organism may carry several O antigens. Thus, most shigellae share one or more O antigens with E. coli

14. Clinical significance: E. coli-associated diarrheal diseases Transmission of intestinal disease is commonly by the fecal/oral route . At least five types of intestinal infections that differ in pathogenic mechanisms have been identified .

15. 1.Enterotoxigenic Escherichia coli. ETEC In the United States and other Western industrialized nations, ETEC diarrhea is the most common cause of a diarrheal disease sometimes referred to as traveler’s diarrhea. ETEC spread commonly via consumption of contaminated food or water. Poor hygiene. A high infective dose (10* 6 10* 10 organisms) is necessary to initiate disease. They produce a heat-labile toxin (LT), which is similar in action and amino acid sequence to cholera toxin from Vibrio cholerae

16. During infection, the A portion activates cellular adenylate Cyclase causing an increase in the conversion of adenosine triphosphate to cyclic adenosine monophosphate (cAMP). The consequence of accumulation of cAMP is hypersecretion of both electrolytes and fluids into the intestinal lumen, resulting in watery diarrhea similar to cholera .

17. 2.Enterohemorrhagic Escherichia coli EHEC The EHEC strain serotype O157:H7 has since been associated with hemorrhagic diarrhea, colitis, and hemolytic uremic syndrome (HUS). HUS is characterized by low platelet count, hemolytic anemia, and kidney failure. E. coli O157:H7 produces two cytotoxins: verotoxin I and verotoxin II. ( Verotoxin I is a phage-encoded cytotoxin identical to the Shiga toxin ( Stx ) produced by Shigella dysenteriae ). In EHEC t he stool contains no leukocytes , which distinguishes it from dysentery caused by Shigella spp. or EIEC infections.

18. 3.Enteroinvasive Escherichia coli. EIEC EIEC differs greatly from EPEC and ETEC strains, less commonly in developing countries than others two. EIEC strains produce dysentery with direct penetration , invasion , and destruction of the intestinal mucosa. This diarrheal illness is very similar to that produced by Shigella spp . The organisms might be easily misidentified because of their similarity to shigellae . EIEC strains can be nonmotile and generally do not ferment lactose the infective dose of EIEC necessary to produce disease is much higher (106) than that of shigellae (about 100 bacterial cells).

19. Clinical significance: extraintestinal disease The source of infection for extraintestinal disease is frequently the patient's own flora , in which the individual’s own E. coli is non pathogenic in the intestine. However, it causes disease in that individual when the organism is found, for example, in the bladder or bloodstream . Urinary tract infections (UTI): E. coli is the most common cause of UTI, including cystitis and pyelonephritis. Women are particularly at risk for infection. Uncomplicated cystitis (the most commonly encountered UTI). The E. coli strains that cause UTIs usually originate in the large intestine as resident biota.

20. Neonatal meningitis : E. coli is a major cause of this disease occurring within the first month of life. The K1 (capsular) antigen is particularly associated with such infections. Sepsis: When normal host defenses are inadequate, E. coli may reach the bloodstream and cause sepsis. Newborns may be highly susceptible to E. coli sepsis because they lack IgM antibodies. Hemolytic uremic syndrome (HUS): is a condition that can occur when the small blood vessels in your kidneys become damaged and inflamed. This damage can cause clots to form in the vessels. The clots clog the filtering system in the kidneys and lead to kidney failure, which could be life-threatening. 5. pneumonia.

21. Laboratory Diagnosis

22. Prevention Practice proper hygiene, especially good handwashing. Wash your hands thoroughly after using the bathroom. ash your hands thoroughly after contact with animals or their environments Wash your hands thoroughly before and after preparing or eating food. Avoid raw milk, unpasteurized dairy products, and unpasteurized juices (such as fresh apple cider ). Cook meats thoroughly.

23. II. SALMONELLA General characteristics Most strains of Salmonella are Lac– produce acid and gas during fermentation of glucose . They also produce H2S from sulfur-containing amino acids. Salmonellae possess multiple types of pili. Salmonellae are both commensal as well as pathogenic . cause of enteritis and systemic infection. transmitted via contaminated water or food from animals and animal products to humans. Salmonella are widely distributed in nature .

24. Classification : according species & sup species The taxonomic classification of salmonellae is complex. The names ( eg , Salmonella Typhi and Salmonella typhimurium) were originally written as if they were genus and species; this form of the nomenclature remains in widespread but incorrect use . Currently, the genus Salmonella is divided into two species each with multiple subspecies and serotypes. The two species are Salmonella enterica and Salmonella bongori . Based on the phenotypic profiles, S. enterica is further subdivided into six subspecies, which are subspecies enterica (subspecies I)(subspecies II), (subspecies IIIa), (subspecies IIIb ),(subspecies IV)(subspecies VI). Most human illness is caused by S. enterica subspecies I strains .

25. Classification: According Antigenic Furthermore, salmonellae can be classified by their serotype ; serotypes are assigned according to antigenically diverse surface structures: somatic O antigens and flagellar H antigens . The 2 species of Salmonella and their respective subspecies consist of more than 2500 serotypes (serovars), including more than 1400 in DNA hybridization group I . Some spp. Has (Vi polysaccharide) is part of the  bacterial capsule . Vi capsular polysaccharide vaccine. present

26. Classification: Salmonella Typhimurium. The widely accepted nomenclature for classification at the present time is as follows: for example, S. enterica subspecies enterica serotype Typhimurium. which can be shortened to Salmonella Typhimurium. with the genus name in italics and the serotype name in roman type .

27. Classification: typhoidal and nontyphoidal. Based on their serotype, Salmonella species (specifically S. enterica) are further classified as “typhoidal” and “nontyphoidal”. 1. Typhoidal Salmonella: refers to those specific serotypes that cause typhoid (“enteric”) fever,and include the serotypes Typhi, Paratyphi A, Paratyphi B, and Paratyphoid C. 2. Non-typhoidal Salmonella: refers to all other serotypes.

28. Virulence Factors The role of fimbriae in adherence in initiating intestinal infection has been cited. Their ability to traverse(cut off) intestinal mucosa. Enterotoxin produced by certain Salmonella strains that cause gastroenteritis has been implicated as a significant virulence factor.

29. Clinical significance Gastroenteritis : This localized disease (also called salmonellosis ) is caused primarily by serotypes enteriditis and typhimurium (nontyphoidal salmonella). It is characterized by nausea, vomiting, and diarrhea (usually nonbloody ) which develop generally within 48 hours of ingesting contaminated food or water. Fever and abdominal cramping are common. In uncompromised patients, disease is generally self-limiting (48 to 72 hours), although convalescent carriage of organisms may persist for a month or more.

30. 2. Enteric (typhoid) fever: infection begins in the small intestine, but few gastrointestinal symptoms occur. The organisms enter, multiply in the mononuclear phagocytes of Peyer’s patches, and then spread to the phagocytes of the liver, gallbladder, and spleen . This leads to bacteremia , which is associated with the onset of fever and other symptoms, probably caused by endotoxin. Survival and growth of the organism within phagosomes in phagocytic cells are a striking feature of this disease, as is the predilection for invasion of the gallbladder , which can result in establishment of the carrier state and excretion of the bacteria in the feces for long periods . Typhoid fever remains a global health problem . In the United States, however, typhoid fever has become less prevalent, and is now primarily a disease of travelers and immigrants.

31. 3. Other sites of Salmonella infection Sustained bacteremia (Septicemia) is often associated with vascular Salmonella infections that occur when bacteria seed a therosclerotic plaque. Salmonella can also cause abdominal infections (often of the hepatobiliary tract and spleen), osteomyelitis , septic arthritis , and, rarely, infections of other tissues or organs . Chronic carriage may, rarely, develop.

32. Laboratory diagnosis

33. prevention Don’t kiss cats, dogs, chickens, turtles, lizards, or other pets or animals. Don’t put your hands in your mouth after petting or playing with animals. Take your pet to the veterinarian regularly. Wash your hands. Clean your pet’s bed, cage .

34. III. Shigella: General characteristics Non–lactose-fermenting. Non motile That can be distinguished from salmonellae by three criteria: they produce no gas from the fermentation of glucose , they do not produce H2S , and they are nonmotile . All shigellae have O antigens (polysaccharide) in their cell walls, and these antigens are used to divide the genus into four groups: A, B, C, and D. Spread from person to person, with contaminated stools serving as a major source of organisms. Flies and contaminated food or water can also transmit the disease Fewer than 200 viable organisms are sufficient to cause disease.

35. Classification : According Antigen Their serologic specificity depends on the polysaccharide. There are more than 40 serotypes. The classification of shigellae relies on biochemical and antigenic characteristics. The pathogenic species are S. sonnei S. flexneri S. dysenteriae S. boydii

36. Pathogenesis and clinical significance Shigella   invade and destroy the mucosa of the large intestine. Infection rarely penetrates to deeper layers of the intestine. does not lead to shigella bacteremia. Exotoxin (Shiga toxin) with enterotoxic and cytotoxic properties has been isolated from these organisms, and its toxicity may play a secondary role in development of intestinal lesions. Shigellae cause classic bacillary dysentery , characterized by diarrhea with blood, mucus, and painful abdominal cramping The disease is generally most severe in the very young and elderly, and among malnourished individuals, in whom shigellosis may lead to severe dehydration and sometimes death.

37. Toxins Endotoxin Upon autolysis: all shigellae release their toxic lipopolysaccharide. This endotoxin probably contributes to the irritation of the bowel wall. Shigella Dysenteriae Exotoxin: S. dysenteriae type 1 (Shiga bacillus) produces a heat-labile exotoxin that affects both the gut and the central nervous system. the exotoxin also inhibits sugar and amino acid absorption in the small intestine

38. IV. OTHER ENTEROBACTERIACEAE Klebsiella Enterobacter Proteus Serratia Citrobacter Providecia Morganella Hafnia and Erwinia Raoutella , Cronobacter , Pantoea which can be found as normal inhabitants of the large intestine, include organisms that are primarily opportunistic and often nosocomial pathogens . Widespread antibiotic resistance among these organisms necessitates sensitivity testing to determine the appropriate antibiotic treatment. Distribution of gram-negative pathogens.

39. 1.Klebsiella Klebsiellae are large nonmotile bacilli that possess a luxurious capsule They are Lac+ K. pneumoniae and K. oxytoca cause necrotizing lobar pneumonia in individuals compromised by alcoholism, diabetes, or chronic obstructive pulmonary disease. K. pneumoniae also causes urinary tract infections and bacteremia, particularly in hospitalized patients.

40. 2. Enterobacter motile and Lac+. They rarely cause primary disease in humans, but frequently colonize hospitalized patients, especially in association with antibiotic treatment, indwelling catheters, or invasive procedures. These organisms may infect burns, wounds, and the respiratory (causing pneumonia), or urinary tracts. E. cloacae and E. aerogenes are two most important Enterobacter species responsible for a variety of nosocomial infections .

41. 3. Serratia Serratia are motile and ferment lactose slowly, if at all. The species of Serratia that most frequently causes human infection is S.marcescens . Serratia can cause extraintestinal infections such as those of the lower respiratory and urinary tracts, especially among hospitalized patients.

42. Proteus, Providencia, and Morganella Are normal intestinal microbiota, and are recognized as opportunistic pathogens. Members of these genera are agents of urinary tract and other extraintestinal infections . Proteus species are relatively common causes of uncomplicated as well as nosocomial UTIs . Other extraintestinal infections, such as wound infections, pneumonias, and septicemias, are associated with compromised patients. Proteus organisms produce urease, which catalyzes the hydrolysis of ureato ammonia. The resulting alkaline environment promotes the precipitation of struvite stones containing insoluble phosphates of magnesium and phosphate.

43. Erwinia and Hafnia Erwinia organisms are usually found in soils and they cause infection in plants. Erwinia herbicola is the only species that has occasionally been isolated from respiratory and urinary infections in chronic debilitated(weaken) patients and in hospitalized patients. Hafnia Hafnia alvei is the only species of the genus Hafnia. It is found in human and animal feces, sewage, soil, and water. H. alvei is motile. It does not ferment lactose, The bacteria have been isolated from abscesses, wounds

44. Diagnosis of Enterobacteriaceae

45. Sources 1.Lippincot – chapter 13. third ed. 2. Jawetz -chapter 15. 28 th ed. 3. Levinson chapter-18. 14 th ed.