Pseudomonas, Burkholderia, Stenotrophomonas and Acinetobacter Flashcards
General Features of Pseudomonas aeruginosa
Gram –
Rod shape
Habitat- normal skin flora, but also in soil and water
Motile- single polar flagellum
Biochemical Properties of Pseudomonas aeruginosa
Oxidase +
Catalase +
Obligate aerobic
Pseudomonas thrives in aquatic, moist environment
Pathogenesis of Pseudomonas aeruginosa
Nosocomial infection:
Opportunistic pathogen
Biofilm formation
Resistant to high salt concentration, dyes, weak antiseptics or common antibiotics
Exotoxin A: (like diphtheria toxin, but less potent)
Ribosylation of Elongation Factor 2 (EF-2) which inhibit it, causing cell death
Clinical Features of Pseudomonas aeruginosa
Pneumonia (#1 nosocomial) and respiratory failure in cystic fibrosis patients
Osteomyelitis in diabetic patients and IV drug users
Infection associated with burning injuries (e.g. burned patient in hospital)
Nosocomial Urinary Tract Infection (UTI)- infecting urine catheter
Skin lesions:
Pruritic papular pustular folliculitis- associated with people using under-
chlorinated hot tubs (known as “hot tub folliculitis”)
Ecthyma gangrenosum- bacteria enter blood causing sepsis. Then release toxins
that damage the tissues. Seen as cutaneous necrosis with black spots
Otitis externa (“swimmer’s ear”)
Diagnosis of Pseudomonas aeruginosa
Culture on agar plate:
Produces blue-green pigment (pyocyanin and pyoverdin)
Fruity, grape-like pleasant odor
Beta-hemolysis on Blood agar
Treatment of Pseudomonas aeruginosa
Very often multi-resistant (MBL, resistant to all beta-lactam)- antibiogram is essential
Piperacillin in combination with Tazobactam (together known as Tazocin)
Aminoglycoside or Fluoroquinolone
Can use Colistin (but it is toxic antibiotic)- against ESBL and MBL
General features and habitat of Burkholderia, Stenotrophomonas and Acinetobacter
All organisms are ubiquitous in nature and commonly contaminate moist hospital sites (nosocomial)- such as sinks, showers, and respirators.
Burkholderia mallei
Glanders disease- usually cause horses, donkeys or mules disease (Asia, Africa, East), which is highly infectious. Clinical features:
Ulcers of skin or mucous membrane
Inhalation of it causes primary pneumonia
Lymphangitis and sepsis (lethal)
Burkholderia pseudomallei
Found in tropical soil of southeast Asia, India, Africa, Australia. Highly infectious, Infections may be dormant for years and only re-occur in stress situations. Peritrichous polar flagella.
Melioidosis- endemic glanders-like disease of animals and humans.
Clinical features:
Chronic lung disease
Fulminant upper lobe pulmonary disease
Acute bacteremia (from localized, suppurative cutaneous infection)
Burkholderia Cepacia Complex
Plant pathogen but opportunistic pathogen in cystic fibrosis, otherwise quite rare.
Very resistant to antibiotics.
Motile with peritrichous polar flagella.
Stenotrophomonas maltophilia
3rd most common gram negative pathogen isolated from sputum of cystic fibrosis patients.
Common nosocomial opportunistic pathogen- in dwelling IV catheters; IV devices; contaminated disinfectant solutions.
Causing: lung infection and sepsis.
Treatment- often is multi-resistant; antibiotics usually used are Trimethoprim and Sulfamethoxazole (TMP-SMX).
Acinetobacter baumanii
Gram negative, coccobacilli, obligate aerobic, oxidase negative, non-fermenting.
Ubiquitous saprophytes (processing decayed food, type of chemoheterotrophic).
Opportunistic pathogen – nosocomial: (patients on broad spectrum antibiotics, recovering from surgery or ventilated)
Respiratory tract infections (RTI) Urinary tract infection (UTI) Wounds infection Sepsis (Catheter in vein: Acinetobacter forms a biofilm on canules and other plastics, which allows it to enter the blood stream)
Resistant to different antibiotics and disinfectants: MACI (Multi-resistant Acinetobacter baumanii) or PACI (Pan-resistant Acinetobacter baumanii)
Therapy: upon in vitro susceptibility tests (e.g. disc diffusion).
