بسم الله الرحمن الرحيم 1 1 1

Ass . Professor of of Medical Microbiology Gram-Negative Rods Enterobacteriaceae Dr. Manal El Said Ass . Professor of of Medical Microbiology

Characters of Enterobacteriaceae All Enterobacteriaciae - Gram-negative rods - Ferment glucose with acid production - Reduce nitrates into nitrites - Oxidase negative

Characters of Enterobacteriaceae Enterobacteriaceae divided into TWO main groups according to action on LACTOSE Lactose Fermenters (LF) Lactose Non-Fermenters (LNF) E. coli Citrobacter Klbesiella Enterobacter Salmonella Shigella, Proteus, Yersinia

Lactose fermenter: 1-Escherichia coli ` Lactose fermenter: 1-Escherichia coli Diseases Urinary tract infection (UTI) Sepsis Neonatal meningitis Traveler's diarrhea Characteristics Facultative gram-negative rods Ferment lactose.

Habitat and Transmission Lactose fermenter: 1-Escherichia coli Habitat and Transmission Habitat is the human colon It colonizes the vagina and urethra ascends UTI Acquired during birth in neonatal meningitis Fecal–oral route in diarrhea.

Lactose fermenter: 1-Escherichia coli Pathogenesis 1- Endotoxin It causes septic shock. Two enterotoxins are produced. 1- Heat-labile toxin 2- Heat-stable toxin 2- Pili For attachment to mucosal surfaces

Lactose fermenter: 1-Escherichia coli Pathogenesis 3- Capsule It impedes phagocytosis. 4-Verotoxin (Shiga-like toxin) It is enterotoxin produced by O157:H7 serotype E. coli It causes bloody diarrhea and hemolytic-uremic syndrome associated with eating undercooked meat.

Lactose fermenter: 1-Escherichia coli Pathogenesis Predisposing factors to UTI in women include: - Proximity of the anus to the vagina & urethra - Short urethra. Abnormalities e.g., strictures, valves & stones. In-dwelling urinary catheters UTI Intravenous lines sepsis Colonization of the vagina neonatal meningitis.

Lactose fermenter: 1-Escherichia coli Laboratory Diagnosis 1-Gram-stained smear

Lactose fermenter: 1-Escherichia coli Laboratory Diagnosis Lactose-fermenting colonies on Eosin Methylene Blue EMB (Green) or MacConkey's agar. Uninoculated plate

Lactose fermenter: 1-Escherichia coli Laboratory Diagnosis Triple Sugar Iron agar shows acid slant and acid butt with gas but no H2S. Biochemical reactions. Type organism by O & H antigens by using antisera.

Lactose fermenter: 1-Escherichia coli Treatment Urinary tract infections: Ampicillin or sulfonamides Meningitis and sepsis: Third-generation cephalosporins Traveler's diarrhea: - Rehydration - Trimethoprim-sulfamethoxazole Antibiotic resistance mediated by plasmid-encoded enzymes: - β-lactamase - Aminoglycoside-modifying enzymes.

Lactose fermenter: 1-Escherichia coli Prevention Prevention of UTI : Limit the frequency and duration of urinary catheterization. Prevention of sepsis : Remove or switch sites of intravenous lines. Prevention of Traveler's diarrhea : - Eating only cooked food and drinking boiled water. - Prophylactic doxycycline. There is no vaccine.

2-Klebsiella pneumoniae ` Lactose fermenter: 2-Klebsiella pneumoniae Diseases Pneumonia UTI Sepsis. Characteristics Facultative gram-negative rods Polysaccharide capsule

2-Klebsiella pneumoniae Habitat and Transmission Lactose fermenter: 2-Klebsiella pneumoniae Habitat and Transmission Habitat is the human upper respiratory & enteric tracts. Organism is transmitted to the lungs by: - Aspiration from upper respiratory tract - Inhalation of respiratory droplets. It is transmitted to the urinary tract by ascending spread of fecal flora.

2-Klebsiella pneumoniae Lactose fermenter: 2-Klebsiella pneumoniae Pathogenesis Endotoxin causes fever and shock associated with sepsis. Capsule : impedes phagocytosis. No exotoxin known. Chronic pulmonary disease predisposes to pneumonia Catheterization predisposes to UTI.

2-Klebsiella pneumoniae Lactose fermenter: 2-Klebsiella pneumoniae Laboratory Diagnosis 1-Gram-stained smear

2-Klebsiella pneumoniae Lactose fermenter: 2-Klebsiella pneumoniae Laboratory Diagnosis 2- Lactose-fermenting on MacConkey's agar Mucoid colonies (polysaccharide capsule)

2-Klebsiella pneumoniae Lactose fermenter: 2-Klebsiella pneumoniae Laboratory Diagnosis 3- Differentiated from Enterobacter and Serratia by biochemical reactions.

2-Klebsiella pneumoniae Lactose fermenter: 2-Klebsiella pneumoniae Treatment Cephalosporins alone or with aminoglycoside. Resistance is mediated by plasmid-encoded enzymes. Prevention No vaccine or drug is available. Urinary & intravenous catheters should be removed .

3-Enterobacter cloacae &Serratia marcescens Lactose Fermenter: 3-Enterobacter cloacae &Serratia marcescens Enteric gram-negative rod similar to K. pneumoniae. but they are motile They causes : - Hospital-acquired pneumonia - UTI - Sepsis Highly antibiotic-resistant.

Lactose fermenter: Citrobacter Enteric gram-negative rod similar to E. coli except being citrate positive. Found in faeces of humans and may be isolated from a variety of clinical specimens. C. koseri occasionally causes neonatal meningitis.