Gram Negative Rods/Cocci

Gram Negative Rods/Cocci

1. The HACEK group (miscellaneous, fastidious, gram negative rods)

   • members of the normal flora of the oropharynx or urogential tract
   • rare causes of various human infections
   • most commonly associated with subacute infective endocarditis caused by bacterial vegetations on the heart valve
   • H:Haemophilus A:Actinobacillus C:Cardiobacterium E:Eikenella K:Kingella

2. Nonfermentative Gram Negative Rods

   • these bacilli dont metabolise glucose by fermentative pathways
   • Genus Pseudomonas
     • Pseudomonas Aeruginosa
       • a major pathogen
       • very resistant to antibiotics
       • causes otitis externa (swimmers ear)
       • nosocomial infections
         • colonises chronic skin ulcers in the elderly
         • colonises and infects burns
         • causes UTIs in people that have urinary catheters
         • lung infections in people with cystic fibrosis
         • septicaemia in those with leukaemia, organ transplants or IV drug abusers
   • Genus Stenotrophomonas
     • nosocomial infections in debilitated patients
       • debilitated patients/patients with cystic fibrosis: lower respiratory tract infection
       • septicaemia
   • Genus Burkholderia
     • Burkholderia Pseudomallei
       • causes Melioidosis (tropical infection)
   • Genus Acinetobacter
     • ubiquitous in soil and aquatic environments
     • colonisers of the human skin and respiratory tract
     • nosocomial infections
       • resistant to multiple antibiotics
     • Acinetobacter Baumannii
       • nosocomial infections in immunocompromised patients
         • pneumonia, IV/catheter related bacteraemia, UTIs
       • community acquired pneumonia in North and Central Australia
     • Acinetobacter Lwoffii
       • same nosocomial infections as A. Baumannii

3. Oxidase Positive Fermentative Rods

   • Genus Vibrio
     • Vibrio Cholerae
       • Causes pandemic cholera
     • V. Alginolyticus
       • lives in Australian water
       • skin and soft tissue ifections following wounds sustained in a marine environment
       • Otitis Externa
     • V. Parahaemolyticus
       • Gastroenteritis from contaminated seafood
     • V. Vulnificus
       • most virulent of the non-cholera Vibrios
       • severe septicaemic illness in immunocompromised hosts
       • severe cellulitis and skin necrosis after contamination of wounds with seawater
   • Genus Aeromonas
     • curved gram negative rods found in aquatic environments
       • also live in the gut of leeches
     • aggressive skin and soft tissue infection following complicating wounds sustained in a marine environment, or following leech therapy

4. Miscellaneous, fastidious, gram negative rods

   • Genus Pasteurella
     • Pasteruella Multocida
       • gram negative rod/coccobacillus
       • normal flora of animals mouths - particularly dogs and cats
         • causes bite wound infections
   • Genus Bordetella
     • Bordetella Pertussis
       • an important human pathogen
       • causes whooping cough.
     • small, gram negative coocobacilli
     • very fastidious
   • Genus Brucella
     • found in sheep, goats, cattle, swine and dogs
     • tiny gram negative coccobacilli
     • causes brucellosis: a zoonotic infection attained upon occuational exposure
   • Genus Bartonella
     • Bartonella Henselae
       • found in the saliva and nails of cats
       • "cat scratch disease"
   • Genus Campylobacter
     • food poisoning from poorly cooked chicken
     • a ubiquitous commensal of poultry and other animals
   • Genus Helicobacter
     • Helicobacter Pylori
       • helical gram negative rod
       • discovered by Barry J Marshall at UWA in 1984
       • major causative factor for duodenal ulcers, and most gastric ulcers
       • major causative factor in gastric adenocarcinoma and gastric lymphoma
   • Genus Legionella
     • a ubiquitous aquatic bacteria
     • L. Pneumophila
       • colonises in air conditioning
       • causes legionnaires disease
     • L. Longbeachae
       • colonises potting mix
       • causes severe pneumonia
   • Genus Haemophilus
     • Haemophilus Influenzae
       • type b
         • meningitis and septicaemia
         • epiglottitis
       • non-typeable
         • mucosal infections: bronchitis, sinusitis, otitis media
     • Haemophilus Ducreyi
       • causes chancroid

5. Gram negative cocci

   • Genus Neisseria
     • Neisseria Meningitidis
       • causes meningococcal infection
       • we currently have vaccinations against serotypes A, B, C, Y and W
     • Neisseria Gonorrhoeae
       • infection spread by sexual contact
         • causes urethritis; cervicitis; purulent discharge; salpingitis (fallopian tubes)
         • opthalmia neonatorum is caused in babies born through a vaginal canal infected with N. gonorrhoeae
   • Genus Moraxella
     • Moraxella Catarrhalis
       • gram negative diplococci
       • commensal of the upper respiratory tract and female genital tract
       • infections
         • lower respiratory tract infection in adults, with underlying lung disease e.g. exacerbation of chronic bronchitis
         • otitis media and sinusitis in children