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Bacteriology > Pseudomonas, Acinobacter, Vibrio, Aeromonas (Ch1) > Flashcards

Pseudomonas, Acinobacter, Vibrio, Aeromonas (Ch1) Flashcards

1
Q

Name the characteristics of Pseudomonadacae bacteria

A
  • Gram-negative bacilli (1.5 to 3 mm in length)
  • Aerobes, and most strains can grow with nitrate as a terminal electron acceptor
  • Rapid grower
  • Singly, in pairs or in short chains
  • Motile (a single polar flagellum).
  • They are oxidase-positive
  • Non capsulated organism (except in cystic fibrosis)
  • Pigment producer (pyoverdin (yellow-green), pyocyanin (blue specific for P. aeruginosa) and pyorubin (brown-red))
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2
Q

Which pigment is specific for Pseudomonas aeruginosa?

A

Pyocyanin (blue pigment)

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3
Q

Where is Pseudomonas found growing in the environment?

A

Pseudomonas is a ubiquitous saprophyte ( found in soil, ground, plant material in the environment)

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4
Q

What are the nutritional requirements of Pseudomonas aeruginosa?

A

Pseudomonas aeruginosa has minimal nutritional requirements, allowing it to survive in various environments.

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5
Q

What are the mechanisms that allow Pseudomonas to survive in various environments?

A

Pseudomonas aeruginosa has mechanisms that allow it to tolerate harsh physical conditions, such as high temperatures, low nutrient availability, and exposure to disinfectants.

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6
Q

Is Pseudomonas aeruginosa frequently found among the mixed flora?

A

No, Pseudomonas aeruginosa is infrequently found among the mixed flora.

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7
Q

How does colonization by Pseudomonas aeruginosa occur in hospitals?

A

Colonization happen during a long time duration in the
hospital

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8
Q

How does Pseudomonas aeruginosa attach and colonize?

A

Pseudomonas aeruginosa attaches and colonizes through the use of pili or fimbriae.

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9
Q

What is the mechanism of local invasion by Pseudomonas aeruginosa?

A

Pseudomonas aeruginosa uses extracellular proteases, elastase (breaks down elastin), lipase, cytotoxin, hemolysin, and pyocyanin (kills competing microbes) to facilitate local invasion.

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10
Q

How does Pseudomonas aeruginosa cause dissemination and systemic disease?

A

Pseudomonas aeruginosa produces exotoxin A, which contributes to the development of systemic disease.

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11
Q

What are the adhesins used by Pseudomonas aeruginosa?

A

Flagella, fimbriae (specifically N-methyl-phenylalanine pili), polysaccharide capsule (glycocalyx), and alginate slime (aids in biofilm formation in respiratory diseases).

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12
Q

What are the invasins produced by Pseudomonas aeruginosa?

A

Pseudomonas aeruginosa produces several invasins, including elastase, alkaline protease, hemolysins (phospholipase C and lecithinase), cytotoxin (leukocidin), pioverdin (siderophores and siderophore uptake systems), and pyocyanin (a diffusible pigment that catalyzes the production of superoxide and hydrogen peroxide, induces the release of chemoattractant IL8).

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13
Q

What is the motility/chemotaxis mechanism used by Pseudomonas aeruginosa?

A

Pseudomonas aeruginosa utilizes flagella for motility and chemotaxis

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14
Q

What are the toxins produced by Pseudomonas aeruginosa? What do these toxins do?

A

Pseudomonas aeruginosa produces exoenzyme S and exoenzyme T, which contribute to tissue invasion, epithelial cell damage, bacterial dissemination, and necrosis.
Additionally, it produces exotoxin A, which inhibits protein synthesis and leads to necrosis.
Lipopolysaccharide (LPS) is also considered a toxin and acts as a lipid A endotoxin.

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15
Q

What are the antiphagocytic surface properties of Pseudomonas aeruginosa?

A

Pseudomonas aeruginosa possesses capsules and slime layers, as well as LPS, which help to resist phagocytosis by the host immune cells.

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16
Q

How does Pseudomonas aeruginosa defend against the serum bactericidal reaction?

A

Pseudomonas aeruginosa employs slime layers, capsules, LPS, and protease enzymes to defend against the serum bactericidal reaction, which is a part of the host immune response.

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17
Q

What are the different infections caused by Pseudomonas?

A
  • Skin and musculoskeletal tissues
    > including wound infections, folliculitis, pyoderma and dermatitis (via burn wounds)
  • Respiratory infections
    > Chronic infections in cystic fibrosis patients
    > Acute pneumonia in other patients
  • CNS infections (systemic) (via joint/hip replacements)
    > Bone and joint infections, such as osteochondritis.
  • Localized infections
    > External otitis (swimmer’s ear), especially in swimmers, diabetics, and the elderly.
    > Eye infections, particularly following corneal trauma or exposure to contaminated water.
  • UTI via catheters
  • Gastrointestinal infections (rare)
  • Bacteremia
    > particularly in neutropenic patients, often preceded by infections in the lower respiratory tract, urinary tract, or skin.
  • Endocarditis
    > particularly in IV drug abusers.
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18
Q

Who are at risk of infection with Pseudomonas aeruginosa?

A
  • People with cystic fibrosis (v. sensitive to lung infection)
  • High antibiotic usage (disrupted normal flora)
  • Mechanical ventilation equipment (direct lung invasion)
  • Burn victims (penetration via skin)
  • Individuals with cancer
  • Patients requiring extensive stays in intensive care units (HA)
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19
Q

What is the characteristic manifestation of cystic fibrosis?

A

Blockage of organs by thick, sticky mucus linings especially in the airways.

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20
Q

What is the severity range of Pseudomonas aeruginosa pulmonary infections?

A

Asymptomatic colonization —> Benign tracheobronchitis —> Severe necrotizing bronchopneumonia

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21
Q

Specimen for Pseudomonas aeruginosa isolation

A
  • Pus
  • Blood
  • Biopsy
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22
Q

Microscopy appearance of Pseudomonas aeruginosa

A
  • Gram-negative rod
  • Singly and in pairs
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23
Q

Culture methods for Pseudomonas aeruginosa

A
  • MacConkey agar
  • Blood agar
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24
Q

Growth characteristics of Pseudomonas aeruginosa

A
  • Optimal growth at 37~42℃
  • No growth at 4℃
  • Obligate aerobic
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25
Q

Identification tests for Pseudomonas aeruginosa

A
  • Oxidase positive
  • Non-fermenter of carbohydrates (NLF), but oxidizes glucose
  • Beta hemolytic on blood agar
  • Grapelike odor
  • Green pigmentation
  • Production of pigments on Muller-Hinton agar or trypticase soy agar
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26
Q

What is the best method to control the spread of Pseudomonas infections?

A

Cleaning and disinfecting medical equipment

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27
Q

What is the treatment approach for Pseudomonas infections in burn patients?

A
  • Topical therapy with antimicrobial agents (e.g., silver sulfadiazine)
  • Surgical debridement
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28
Q

What is the importance of susceptibility testing in Pseudomonas infections?

A

Susceptibility testing is essential to determine the most effective antibiotics for treatment

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29
Q

What is an effective antibiotic combination for acute Pseudomonas aeruginosa infections

A

Gentamicin and carbenicillin combination

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30
Q

Prevention strategy for Pseudomonas infections?

A
  • Avoid misuse of antibiotics
  • Prevent nosocomial infections (infections acquired in a healthcare setting)
31
Q

What are some gram-negative, oxidase-positive bacilli other than Pseudomonas aeruginosa?

A
  • Burkholderia cepacia Complex
  • Burkholderia pseudomallei
32
Q

What are the modes of transmission for Burkholderia cepacia Complex?

A
  • Personnel: Hands, antiseptic soaps, hand lotion
  • Respiratory equipment and/or fluids: Respirator tubing condensate, ultrasonic nebulizers, inhalation medications
  • Intravenous lines and/or fluids: Intravenous solutions, central venous catheters
  • Pressure-monitoring devices: Pressure transducer fluids
  • Urine and/or fluids: Indwelling Foley catheters, urometers, irrigation solutions
33
Q

Diseases associated with Burkholderia cepacia Complex

A
  • Pulmonary infections: Range from colonization to bronchopneumonia, primarily in patients with cystic fibrosis or chronic granulomatous disease
  • Opportunistic infections: Urinary tract infections in catheterized patients; infections in immunocompromised patients with contaminated intravascular catheters
34
Q

Characteristics of Burkholderia pseudomallei

A
  • Hazardous and highly infectious
  • Can cause pulmonary infections
  • Susceptible populations: Alcoholics, diabetics, and individuals with chronic renal or lung disease.
35
Q

What are the characteristics and colonization sites of Stenotrophomonas maltophilia (in the hospital setting)?

A
  • Fluids used in the hospital setting: Irrigation solutions, intravenous fluids
  • Patient secretions: Respiratory secretions, urine, wound exudates
36
Q

Opportunistic infections associated with Stenotrophomonas maltophilia

A

Bacteremia and Pneumonia are common in immunocompromised patients previously exposed to broad-spectrum antimicrobial therapy.

37
Q

What is the prevalence of Stenotrophomonas maltophilia in catheter-associated infections?

A
  • It is a common cause of catheter-associated bacteruria in hospitalized patients
  • Rare cause of nosocomial pneumonia
38
Q

What is the significance of the recovery of Stenotrophomonas maltophilia from respiratory secretions?

A

Represents colonization rather than infection

39
Q

What are the two Acinetobacter species?

A

A.baumannii and A. lwoffii

40
Q

Characteristics of Acinetobacter species

A
  • Pleomorphic aerobic gram-negative coccobacillus
  • Oxidase-positive
  • A. baumannii preferentially colonizes aquatic environments
  • Common colonization sites: Skin, oropharynx secretions, respiratory secretions, urine
  • Low virulence
  • Capable of causing infection in organ transplants and febrile neutropenia patients
41
Q

Types of infections associated with Acinetobacter species

A
  • Pulmonary infections: Opportunistic pathogen in patients receiving respiratory therapy
  • Wound infections: Nosocomial infections in soldiers with traumatic wounds (rare)
42
Q

Antibiotic resistance of A. baumannii

A
  • Inherently resistant to multiple antibiotics
  • Multidrug-resistant organism
43
Q

Common source of cholera contamination

A

Water or food sources contaminated with feces from an infected person

44
Q

What are the conditions favorable for the spread of cholera?

A
  • Inadequate water treatment
  • Poor sanitation
  • Inadequate hygiene
45
Q

What is the temperature range for Vibrio growth?

A

Warm months: 14 to 40 degrees Celsius

46
Q

Likelihood of person-to-person spread of cholera. Rare or common?

A

Rare

47
Q

What is the infectious dose of Vibrio cholera?

A

High infectious dose (Ability to resist acidity)

48
Q

What are the serogroups of Vibrio cholerae?

A
  • Approximately 206 serogroups identified
  • Clinical cholera is associated with serogroups O1 (Classical and EL tor) and O139
49
Q

What method is used used to differentiate and classify Vibrio cholerae strains based on their phenotypic characteristics?

A

Phenotypic fingerprinting

50
Q

What are the characteristics of Vibrio cholera?

A
  • Gram negative
  • Facultative anaerobic
  • Ferment glucose
  • Oxidase positive
  • Polar flagella
  • Curved rods
  • Comma shaped
  • Sheathed
51
Q

What are the virulence factors of Vibrio cholerae?

A
  • Pili (adherence)
  • Flagella
  • Lipopolysaccharide
  • Cholera Toxin (O1 and O139) - responsible for epidemics of cholera
  • Zonula occludens toxin
  • Accessory cholera enterotoxin
52
Q

What are three other species of Vibrio bacteria that can cause infection?

A

Vibrio vulnificus
Vibrio parahaemolyticus
Vibrio fisheri

53
Q

What are the virulence factors of Vibrio vulnificus?

A

Polysaccharide capsules

54
Q

What are the virulence factors of Vibrio parahaemolyticus?

A

Kanagawa hemolysin: an enterotoxin that induces chloride ion secretion in epithelial cells by increasing intracellular calcium

55
Q

What is the transmission route for Vibrio cholerae?

A
  • Ingestion of contaminated water, particularly water contaminated with algae, shellfish, and seawater
  • Ingestion of contaminated food, such as leftover rice, raw fish, cooked crabs, seafood, raw oysters, and fresh vegetables and fruits
56
Q

What is the transmission route for Vibrio parahaemolyticus?

A

Ingestion of contaminated shellfish and seawater

57
Q

What is the transmission route for Vibrio vulnificus?

A

Ingestion of contaminated shellfish and seawater

58
Q

What is the transmission route for Vibrio fisheri?

A

Ingestion of contaminated shellfish and squid

59
Q

Transmission routes for Vibrio cholerae, Vibrio parahaemolyticus, Vibrio vulnificus, and Vibrio fisheri

A
  • Fecal-oral route: Ingestion of 108-1010 organisms
  • Contact with feces or vomitus of infected people
  • Ingestion of fecally contaminated water and foods

• Vibrio cholera: Algae, Shelfish, seawater
• Vibrio parahaemolyticus: Shelfish, seawater
• Vibrio vulnificus: Shelfish, seawater
• Vibrio fisheri: Shelfish, squid

60
Q

What is the pathogenesis of Vibrio species, specifically Vibrio cholerae?

A
  • Bacteria multiply in the lumen of the small intestine
  • Bacteria cross the mucus layer of the intestinal mucosa
  • Cholera toxin (enterotoxin: CT toxin) is produced, leading to watery diarrhea (similar to the heat-labile toxin of enterotoxigenic Escherichia coli, or ETEC)
  • Adherence is mediated by pili (adherence is necessary for infection to occur)
  • The acidity of the stomach partially protects against contamination
61
Q

Clinical features of toxigenic Vibrio cholerae O1 and O139 infection

A
  • Abrupt onset of the disease (2-3 days after ingestion)
  • Watery diarrhea without strain, referred to as “rice-water stools” (up to 20 L of fluids lost per day)
  • Vomiting
  • Rapid heart rate
  • Loss of skin elasticity
  • Dry mucous membranes
  • Low blood pressure
  • Thirst
  • Dehydration leading to metabolic acidosis and hypovolemic shock
  • Sunken eyes
  • Can lead to death if not treated
62
Q

Mortality rate of untreated cholera?

A

Untreated cholera has a 50% mortality rate

63
Q

What is the treatment for cholera?

A

Fluid and electrolyte replacement (oral rehydration therapy or intravenous fluids)

64
Q

Clinical features of Vibrio parahaemolyticus infection

A
  • Range from self-limited diarrhea to a mild, cholera-like illness
  • Typically occurs after ingestion of uncooked food and contaminated seafood
  • Common in Asia
65
Q

Clinical features of Vibrio vulnificus infection

A
  • Primary septicemia with a high mortality rate within hours after consumption of contaminated raw oysters
  • Rapidly progressive wound infection after exposure to contaminated seawater
  • Wound infection rapidly progresses to necrosis and can lead to death
66
Q

What are the diagnostic methods for Vibrio species

A
  • Gram stain (reveals gram-negative curved rods)
  • Wet mount of liquid stool, which may reveal comma-shaped bacteria
  • Oxidase positive
  • Cary Blair transport media is ideal for transport of fecal specimens
  • Isolation and identification of Vibrio cholerae serogroup O1 or O139 by culture of a stool specimen
  • Selective agar: Thiosulfate citrate bile salts sucrose (TCBS) agar (selective for V.cholera which shows green and V. parahaemolyticus which shows yellow)
  • Crystal VC® dipstick rapid test for outbreak warning (low sensitivity) - Culture confirmation is necessary
  • PCR (Polymerase Chain Reaction) is used more recently for diagnosis
67
Q

What is another diagnostic test that can identify the presence of V.cholera?

A
  • The string test is performed by emulsifying a bacterial colony in a 0.5% aqueous solution of sodium deoxycholate.
  • Positive test: If the bacterial suspension forms a string-like structure when a loop or inoculation needle is lifted from the solution.
68
Q

Treatment of Vibrio infections?

A
  • Fluid and electrolyte replacement to manage dehydration and electrolyte imbalances
  • Antibiotics (not always necessary): Macrolides such as Lincosamides or Azithromycin may be prescribed in certain cases
  • Prompt and aggressive treatment for V. vulnificus wound or septic infections is crucial
69
Q

What prevention techniques are appropriate for vibrio infections?

A
  • Preventing contamination of food and water, such as boiling water and covering food
  • Antibiotic prophylaxis may be considered in specific situations
  • Oral inactivated or non-live cholera vaccines are available and may be used during outbreaks
  • Education on personal and domestic hygiene practices
  • Prevention of contamination of water supplies
  • Improvement of sewage systems
70
Q

What are the characteristics of Aeromonas?

A
  • Gram-negative bacteria
  • Facultatively anaerobic
  • Found in fresh and brackish water and in cold-blooded animals
  • Includes species like Aeromonas hydrophila, Aeromonas caviae, and Aeromonas veronii
71
Q

What are the diseases associated with Aeromonas?

A
  • Diarrheal disease: Can cause both watery diarrhea and dysenteric diarrhea
  • Wound infection: Associated with traumatic injuries exposed to contaminated water, which may lead to fasciitis
  • Opportunistic systemic disease in immunocompromised individuals
72
Q

How do you identify Aeromonas?

A

String test negative: Unlike Vibrio cholerae, Aeromonas does not produce a string-like structure in a 0.5% aqueous solution of sodium deoxycholate.

73
Q

Treatment for Aeromonas infections

A

Drugs such as Penicillin, Cephalosporin, and Erythromycin are commonly used for treatment.

74
Q

A patient presents with a lesion surrounded by a green discoloration. What is the most probable causing agent of this?

A

Pseudomonas aeruginosa

Bacteriology (11 decks)

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