ENTEROBACTERIACEAE.pptx..................

Micro

1. ENTEROBACTERIACEAE

2. Introduction Enterobacteriaceae are large and diverse family of gram-negative rods, members of which are both free-living and part of the normal flora of humans and animals. They are the most common cause of urinary tract infections (UTI), some species are important etiologic agents of diarrhoea, spread to the bloodstream causes gram-negative endotoxic shock & often fatal complications.

3. ENTEROBACTERIACEAE Enterobacteriaceae are among the largest bacteria, range from large coccobacilli to elongated, filamentous rods. The cell wall, cell membrane, and internal structures are morphologically similar for all Enterobacteriaceae The outer membrane lipopolysaccharide (LPS) is called the (O antigen), cell surface polysaccharides are termed the (K antigen). Motile strains have flagella (H antigen).

4. GROWTH AND METABOLISM Enterobacteriaceae grow readily on simple media, often with only a single carbon energy source. Growth is rapid under both aerobic and anaerobic conditions after 12 to 18 hours of incubation. All Enterobacteriaceae ferment glucose, reduce nitrates to nitrites, and are oxidase negative.

5. CLASSIFICATION Genus and species designations are based on phenotypic characteristics, such as patterns of carbohydrate fermentation & amino acid breakdown . The O, K, and H antigens are used to divide some species into serotypes , such as Escherichia coli O157:H7, the cause of numerous food-borne outbreaks . In recent years, DNA and RNA homology data have been used to validate these relationships and establish new ones.

6. TOXINS The LPS endotoxin is common to all Gram-negative bacteria. Some Enterobacteriaceae also produce exotoxins , which act on host cells by damaging membranes, inhibiting protein synthesis, or altering metabolic pathways. The end result of these actions may be cell death or physiologic alteration on the function of the affected cell.

7. PATHOGENESIS 1.Opportunistic Infections Due to their presence in the environment and normal flora, they can produce disease when they gain access to normally sterile body sites. Surface structures such as pili aid this penetration, once in deeper tissues, their ability to persist and cause injury due to the action endotoxin , exotoxins or capsules. In UTI, it gain access to the urinary bladder due to minor trauma or instrumentation, strains able to adhere to uroepithelial cell can persist and multiply in the nutrient-rich urine, sometimes spreading through the ureters to the renal pelvis and kidney

8. 2. Intestinal Infections Some intestinal pathogens have invasive properties or virulence factors which correlate with the type of diarrhoea they produce. The invasive and cytotoxic strains produce an inflammatory diarrhoea called dysentery . The enterotoxin -producing strains cause a watery diarrhoea. For a few species, the intestinal tract is the portal of entry, but the disease is systemic due to spread of bacteria to multiple organs as Enteric (typhoid) fever caused by Salmonella Typhi

9. Enterobacteriaceae, a public health problem. Contamination of water supply by sewage is detected by their presence of mainly E.coli . E.coli colony count above 4/dl in municipal drinking water is unacceptable. Disinfection of public water by chlorination.

10. Laboratory diagnosis Selective & differential medias. Sugar fermentation tests. Urea test. Motility test. Agglutination tests.

11. Antibiotic therapy A wide range of antibiotics are potentially effective, penicillins , cephalosporins , aminoglycosides and others. Perform antibiotic sensitivity tests Many isolates are highly antibiotic resistant due to enzymes production e.g. β - lactamase . Genes for these enzymes can be acquired by plasmids.

12. A.Pathogens both within and outside the enteric tract Escherichia coli : It causes a)Intestinal tract infection b)Systemic infection c)Urinary tract infection 2. Salmoella sp . It causes: a) Enterocolitis b)Typhoid fever c)Septicemia

13. B.Pathogens primarily within the enteric tract Shigella sp . Human disease only, it causes enterocolitis with bloody diarrhea ( dysentry ) Vibrio sp . V.cholerae causes cholera, others causes diarrhea & sepsis 3. Campylobacter sp . causes enterocolitis . 4. Helicobacter causes gastritis & peptic ulcer.

14. C.Pathogens outside the enteric tract Klebsiella sp . Causes UTI , pneumonia , sepsis and meningitis. 2. Proteus sp . Causes UTI. 3. Psuedomonas sp . Causes infections in patients with lowered immunity e.g. sepsis, pneumonia & UTI. 4. Bacteroides sp . Causes serious anaerobic infections e.g. sepsis, peritonitis and abscesses.

15. D.Gram – ve bacteria related to Respiratory Tract Haemophilus sp. Causes meningitis ,upper respiratory tract incection and sepsis. 2. Bordetella pertussis Causes whooping cough. 3. Legionella sp. Causes pneumonia.

16. E.Gram – ve bacteria related to Animal Sources Brucella sp. Causes Brucellosis (undulant fever) 2. Yersinia pestis : Causes Plaque. 3. Others.

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