Gram Negative Bacilli PDF

Gram negative bacilli: Gastrointestinal: Food poisoning, diarrhea, dysentery, Cholera. Microbiology Department Dr. Mohamed Elmutasim Mon. Feb. 21. 2023 Objectives: To Study: -Gastrointestinal Diseases: Food poisoning, diarrhea, dysentery, Cholera: causes, diagnosis & prevention Gram-Negative Rods...

Gram negative bacilli: Gastrointestinal: Food poisoning, diarrhea, dysentery, Cholera. Microbiology Department Dr. Mohamed Elmutasim Mon. Feb. 21. 2023 Objectives: To Study: -Gastrointestinal Diseases: Food poisoning, diarrhea, dysentery, Cholera: causes, diagnosis & prevention Gram-Negative Rods: Enterobacteriaceae Enterobacteriaciae properties; - Gram-negative rods - Ferment glucose with acid production - Reduce nitrates into nitrites - Oxidase negative Enterobacteriaceae divided into TWO main groups according to action on LACTOSE Lactose Non-Fermenters (LNF) Lactose Fermenters (LF) Lactose fermenter: 1-Escherichia coli Diseases: -Urinary tract Infection (UTI) -Sepsis -Neonatal meningitis -Traveler's diarrhea Habitat is the human colon Transmission: -It colonizes the vagina and urethra ascends UTI -Acquired during birth in neonatal meningitis -Fecal–oral route in diarrhea. Lactose fermenter: 1-Escherichia coli Diagnosis: -Gram-negative rods -Ferment lactose. -Indole positive 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 -Colonization of the vagina neonatal meningitis. Lactose fermenter: 2-Klebsiella pneumoniae Diseases: -Pneumonia -UTI -Sepsis. Habitat is the human upper respiratory & enteric tracts. Transmission: Organism is transmitted to the lungs by: - Inhalation of respiratory droplets. -It is transmitted to the urinary tract by ascending spread of fecal flora. Lactose fermenter: 2-Klebsiella pneumoniae Diagnosis: -Facultative gram-negative rods -Polysaccharide capsule -Citrate positive Predisposing factors: -Chronic pulmonary disease predisposes to pneumonia -Catheterization predisposes to UTI. 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. Non Lactose: Salmonella typhi Disease: Typhoid fever. Habitat is the human colon only. Transmission is by fecal–oral route. Diagnosis: -Facultative gram-negative rods. -Non–lactose-fermenting. -Produces H2S.  Salmonella typhi Predisposing factors: -Decreased stomach acid resulting from ingestion of antacids or gastrectomy. -Chronic carrier state established in gallbladder. Organism excreted in bile fecal–oral spread to others. Salmonella enteritidis (Salmonella enterica) Diseases: Enterocolitis. Sepsis with metastatic abscesses. Habitat is the enteric tract of humans & animals, e.g., chickens & domestic livestock. Transmission is by the fecal–oral route. Diagnosis: Facultative gram-negative rods. Non–lactose-fermenting. Produces H2S. Motile Shigella Species (e.g., S. dysenteriae, S. sonnei) Disease: Enterocolitis (dysentery). Habitat is the human colon only No animal carriers Transmission is by the fecal–oral route. Diagnosis: Facultative gram-negative rods. Non–lactose-fermenting. Nonmotile Shigella Species (e.g., S. dysenteriae, S. sonnei) Pathogenicity: -Invades the mucosa of the ileum and colon sepsis (rare) Endotoxin in cell wall. -The infectious dose of Shigella is low (1–10 organisms) because it is resistant to stomach acid. -Children in mental institutions & day care centers experience outbreaks. -No chronic carrier. Proteus Species (e.g., P. vulgaris, P. mirabilis) Diseases: -UTI -Sepsis Habitat is the human colon & environment (soil & water). Transmission to urinary tract is by ascending spread of fecal flora. Diagnosis: Facultative gram-negative rods. Non–lactose-fermenting. Highly motile. Produce urease. Proteus Species (e.g., P. vulgaris, P. mirabilis) Pathogenesis: Endotoxin causes fever and shock associated with sepsis. Urease degrades urea to produce ammonia Ph. This leads to stones -Organism is highly motile facilitate entry into bladder. Predisposing factors are: -Colonization of the vagina -Urinary catheters -Abnormalities of urinary tract (strictures, valves & stones)  Yersinia pestis Disease: Bubonic & pneumonic plague. Bubo is a swollen inflamed lymph node, located in the region of the flea bite Habitat: Reservoir is wild rodents, e.g. rats. Transmission is by flea bite. Diagnosis: Small gram-negative rods with bipolar ("safety pin") staining. One of the most virulent organisms (very low ID50) Thank You