Gram Negative Bacteria

Gram Negative Bacteria

1. cocci

   • neisseria
     • nonmotile, aerobic, fimbriae, polysaccharide capsules
     • oxidase positive
     • lipooligosaccharide
       • composed of lipid A (endotoxin) and sugar
       • attach and invade human cells
       • trigger shock, blood coagulation, petechiae (minute hemorrhaging skin lesions)
     • fastitdious growth requirements, susceptible to drying, extreme temps
     • n. gonorrhoeae
       • disease: gonorrhea
         • only in humans
         • STD
         • more likely in women
         • adhere to epithelial cells of mucous membranes, cleaves IgA in mucus, survive and multiple within neutrophils
         • symptoms: acute inflammation, infection in urethra, painful urination, purulent discharge, infertility
           • usually asymptomatic in women
         • infect uterus and fallopian tubes via sperm triggering PID
         • infection of urethra, proctitis, pharyngitis, gingivitis, arthritis, meningitis, endocarditis
       • ophthalmia neonatorum
         • inflammation of conjuctiva in newborns
       • treatment: broad spectrum cephalosporins
       • diagnosis: Thayer-Martin agar
     • n. meningitidis
       • polysaccharide capsules resist lytic enzymes of phagosomes
       • normal microbiota of upper respiratory tract
       • transmission: respiratory droplets in people living in close contact
       • symptoms: sore throat, fever, headache, stiff neck, vomiting, convulsions, arthritis, partial loss of hearing
       • disease: meningitis, septicemia
       • diagnosis: spinal tap
       • treatment: IV antibiotics ceftriaxone, ciprofloxacin, rifampin

2. bacillus

   • facultative anaerobes
     • enterobacteriacea
       • intestinal microbiota
       • oxidase negative, peritrichous flagella, reduce nitrate, anaerobic glucose fermentation
       • pathogenicity: common antigen (core polysaccharide), O polysaccharide, lipid A
       • virulence factors: capsules, fimbriae, adhesins, exotoxins, iron binding compounds (siderophores), hemolysins, type III secretion system
       • coliform (lactose fermenting)
         • escherichia coli
           • disease: septicemia, UTI, neonatal meningitis, pneumonia, gastroenteritis, endocarditis, acute pyelonephritis, hemolytic uremic syndrome
             • symptoms: watery diarrhea, cramps, nausea, vomiting, fever, flank pain, bacteriuria, profuse perspiration, nausea, vomiting
           • O157:H7
             • consumption of undercooked beef, unpasteurized milk, fruit juice contaminated with feces
           • shiga like toxin
             • inhibits protein synthesis
           • enterotoxigenic, enteropathogenic
             • traveller's disease
           • enterohemorrhagic, enteroinvasive
             • bloody diarrhea
         • klebsiella pneumoniae
           • nonmotile
           • diseases: pneumonia, bacteremia, wound infection, UTI, meningitis
             • bloody sputum
         • serratia marcescens
           • red pigment
           • grows on hospital supplies
           • resistant to antimicrobial drugs
       • noncoliform (non lactose fermenting)
         • proteus mirabilis
           • facultative anaerobe, few polar flagella,concentric wavelike pattern on agar
           • disease: UTI in patients with catheters, kidney stones
           • resistant to many antimicrobial drugs
       • true pathogens
         • salmonella enterica
           • motile, lactose negative, oxidase negative
           • infection from contaminated food, especially eggs, poultry
           • salmonellosis
             • nonbloody diarrhea, nausea, vomiting, fever, myalgia, headache, abdominal cramps
             • bacteria attach to cells lining small intestine
               • type III secretion systems, nonphagocytic cells endocytize bacteria
                 • kill host cell inducing signs and symptoms
                   • moves into bloodstream
             • treatment: fluid and electrolyte replacement
           • typhoid fever
             • symptoms: fever, headache, muscle pains, malaise, loss of appetite, peritonitis
         • shigella dysenteriae
           • nonmotile
           • shigellosis
             • symptoms: abdominal cramps, fever, diarrhea, pus containing bloody stools
             • similar mechanism to salmonellosis but in colon
             • treatment: replacement of fluid, electrolytes, ciprofloxacin, solfonamides, penicillin, cephalosporins
         • yersinia
     • pasteurellaceae
       • oxidase positive