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Bacteriology > Enterococcus 2 > Flashcards

Enterococcus 2 Flashcards

1
Q

What is the Gram staining characteristic of Yersinia?

A

Yersinia is a Gram-negative coccobacillus, which means it appears as a rod-shaped bacterium with rounded ends.

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2
Q

How does Yersinia metabolize in terms of oxygen requirements?

A

Yersinia is a facultatively anaerobic bacterium

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3
Q

What is the oxidase reaction result for Yersinia?

A

Yersinia is oxidase negative, meaning it does not produce the enzyme oxidase.

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4
Q

What are the components of the lipopolysaccharide (LPS) in Yersinia?

A

The lipopolysaccharide (LPS) in Yersinia consists of somatic O polysaccharide, core polysaccharide (common antigen), and lipid A (endotoxin). LPS is an important component of the outer membrane of Gram-negative bacteria.

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5
Q

Which species of Yersinia is covered with a protein capsule?

A

Yersinia pestis, the causative agent of plague, is covered with a protein capsule.

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6
Q

Name the three different species of Yersinia.

A

The three different species of Yersinia are Yersinia pestis (plague), Yersinia enterocolitica, and Yersinia pseudotuberculosis.

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7
Q

What is the unique growth characteristic of some Yersinia species at cold temperatures?

A

Some Yersinia species, such as Yersinia enterocolitica, can grow at cold temperatures. They can grow to high numbers in contaminated, refrigerated food or blood products.

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8
Q

How can the plague bacteria be transmitted to humans through fleas?

A

Flea bites can transmit the plague bacteria to humans. The bites of infected fleas can cause bubonic or septicemic plague.

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9
Q

What is another way that humans can acquire bubonic or septicemic plague?

A

Humans can become infected by coming into contact with contaminated fluid or tissue of an animal infected with the plague. This can also lead to bubonic or septicemic plague.

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10
Q

How is pneumonic plague transmitted?

A

Pneumonic plague, the most severe and highly contagious form of the plague, can be transmitted through infectious droplets. When an infected individual coughs or sneezes, the bacteria can be released into the air and inhaled by others.

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11
Q

What is the function of the (F1) gene in Yersinia?

A

The (F1) gene codes for the capsule of Yersinia, which inhibits phagocytic migration and engulfment. The capsule helps the bacteria evade the immune system.

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12
Q

What happens to the F1 gene once it enters the human body?

A

The F1 gene gets activated at 37°C

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13
Q

What is the function of the plasminogen activator (Pla) protease gene in Yersinia?

A

The Pla protease gene in Yersinia produces a protease enzyme that inhibits platelet aggregation and prevents opsonization by inhibiting the binding of C3b. This helps the bacteria evade the immune response.

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14
Q

What is the function of Type III secretion in Yersinia?

A

Yersinia possesses a Type III secretion system, which allows the bacteria to inject proteins into host cells. These secreted proteins (Yops) suppress cytokine production, which helps Yersinia avoid detection and modulate the immune response.

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15
Q

What virulence factor allows Yersinia to acquire iron?

A

Siderosphores

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16
Q

What is the role of Yops (Yersinia outer proteins) in Yersinia pathogenesis?

A

Yops are a group of proteins produced by Yersinia that have various functions. They can dephosphorylate several proteins, disrupt actin filaments, and inhibit phagocytosis. They can also induce apoptosis (programmed cell death) in host cells.

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17
Q

What is the most common form of plague caused by Yersinia pestis?

A

The most common form of plague caused by Yersinia pestis is bubonic plague.

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18
Q

Describe the progression of bubonic plague.

A

Infected flea bite —after 7 days IP—> Yersinia pestis proliferation on bite —> Vesico-pustular lesions —-> Dissemination odd bacteria through lymphatic system —-> enlargement and swelling of lymph nodes (bubo) in groin, armpit or neck and high fever

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19
Q

What is septicemia plague?

A

Septicemia plague is a rapidly developing form of the disease that occurs if patients are not treated promptly. It is characterized by the widespread presence of Yersinia pestis in the bloodstream.

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20
Q

What is the clinical presentation of pulmonary plague?

A

Patients initially experience fever and malaise, followed by the development of pulmonary signs within 1 day. Pulmonary plague is highly infectious, and person-to-person spread can occur through aerosols.

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21
Q

What is the incubation period of pulmonary plague?

A

Pulmonary plague is a severe and rapidly progressing condition. The incubation period is shorter compared to other forms of plague, typically 2 to 3 days.

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22
Q

What is the Wright-Giemsa staining characteristic of Yersinia Pestis?

A

Peripheral blood smear of septicemic plague patien shows large numbers of bipolar-staining bacilli —> safety pin like stain

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23
Q

What are the appropriate diagnostic specimens for Yersinia pestis infection?

A

Blood, bubo aspirates (fluid obtained from the swollen lymph nodes), sputum, tracheobronchial washes (fluid obtained from the airways), swabs of skin lesions or pharyngeal mucosa, and CSF

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24
Q

How are Yersinia enterocolitica and Yersinia pseudotuberculosis acquired?

A

Yersinia enterocolitica and Yersinia pseudotuberculosis are acquired by ingestion, typically through contaminated food or water. After ingestion, the bacteria multiply in the mesenteric ganglia, which are clusters of nerve cells in the intestinal wall.

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25
Q

What are the clinical manifestations of Yersinia enterocolitica and Yersinia pseudotuberculosis infections?

A

Infections with Yersinia enterocolitica and Yersinia pseudotuberculosis can cause enterocolitis, characterized by symptoms such as diarrhea, fever and abdominal pain lasting for 1 to 2 weeks or longer if chronic.

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26
Q

What happens to fragile people infected with Yersinia enterocolitica or Yersinia pseudotuberculosis

A

The bacteria can cause septicemia, arthritis, abscess formation, hepatitis, and osteomyelitis particularly in individuals with weakened immune systems or underlying health conditions.

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27
Q

What are the characteristics of Yersinia enterocolitica and Yersinia pseudotuberculosis?

A

Yersinia enterocolitica and Yersinia pseudotuberculosis are pleomorphic gram-negative bacilli.

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28
Q

What is the typical incubation period for Yersinia enterocolitica and Yersinia pseudotuberculosis infections?

A

The incubation period for these infections is typically 1 to 10 days, with an average of 4 to 6 days.

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29
Q

What proportion of Yersinia enterocolitica infections are categorized as enterocolitis?

A

2/3

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30
Q

What disease can Yersinia pseudotuberculosis cause?

A

Yersinia pseudotuberculosis can produce an enteric disease with similar clinical features to Yersinia enterocolitica.

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31
Q

What are the three main species of Klebsiella?

A

Klebsiella pneumoniae, Klebsiella oxytoca, and Klebsiella granulomatis.

32
Q

What are the virulence factors of Klebsiella species?

A

Klebsiella species have several virulence factors, including
lipopolysaccharide (O antigen)
capsular polysaccharide (K antigen)
adhesins
siderophores

33
Q

Where can Klebsiella species colonize in humans?

A

Klebsiella species can colonize the skin, pharynx (throat), or gastrointestinal tract of humans.

34
Q

What are the risk factors for Klebsiella infections?

A

Klebsiella infections can occur in both community and hospital settings.
- In the community, the elderly and individuals with alcoholismare at higher risk.
- In hospitals, Klebsiella infections account for 8-10% of healthcare-associated infections (HAIs).

35
Q

What are the common types of infections caused by Klebsiella species?

A

Klebsiella species can cause urinary tract infections (UTIs), lower respiratory tract infections (LRTIs) such as pneumonia, surgical wound infections, and in the case of K. granulomatis, chronic genital ulcerative disease (granuloma inguinale or donovanosis).

36
Q

What are the characteristics of Klebsiella pneumoniae-associated LRT infections?

A

Klebsiella pneumoniae LRT infections can be severe and may produce thick mucoid sputum. This can lead to pneumonia with symptoms such as coughing up jelly-like or bloody sputum.

37
Q

What is a specific complication associated with K. oxytoca infection in neonates?

A

K. oxytoca has been implicated in neonatal bacteremia, particularly among premature infants and in neonatal intensive care units.

38
Q

What are some complications associated with Klebsiella infections?

A

Complications of Klebsiella infections can include bacteremia, thrombophlebitis (inflammation of a vein with blood clot formation), cholecystitis (inflammation of the gallbladder), osteomyelitis, and meningitis.

39
Q

What is the antibiotic resistance pattern of Klebsiella pneumoniae strains?

A

All strains of Klebsiella pneumoniae are resistant to ampicillin due to the presence of a chromosomal gene encoding a penicillin-specific β-lactamase.

40
Q

What are the two main species of Serratia?

A

The two main species of Serratia are Serratia marcescens and Serratia liquefaciens.

41
Q

How do Serratia species survive under harsh conditions?

A

Serratia species have the ability to survive under harsh conditions, including in a variety of disinfectants.

42
Q

How do infections caused by Serratia marcescens typically spread within or among hospitals?

A

Infections caused by Serratia marcescens may begin with exogenous contamination and can spread within or among hospitals on the hands of personnel.

43
Q

What are the common sites of infection caused by Serratia species?

A

The most common site of infection caused by Serratia species is the urinary tract. However, the organism is also frequently isolated from the respiratory tract and wounds. Serratia species contribute to about 2% of healthcare-associated infections (HAIs).

44
Q

What are the complications that can arise from Serratia infections?

A

Bacteremia

45
Q

Are Serratia species beta-lactamase producers?

A

Yes

46
Q

What are the three main species of Enterobacter?

A

The three main species of Enterobacter are Enterobacter cloacae, Enterobacter aerogenes, and Enterobacter sakazakii.

47
Q

How do Enterobacter strains commonly arise in hospitalized patients?

A

Enterobacter strains commonly arise from the endogenous intestinal flora of hospitalized patients. However, they can also occur in common source outbreaks or be spread from patient to patient.

48
Q

What are some common nosocomial infections caused by Enterobacter species?

A
  • Pneumonia
  • UTIs
    -Meningitis
  • Wound and burn infections
  • IV or Prosthetic device
49
Q

What are some virulence factors of Enterobacter species?

A

Enterobacter species possess a capsule, which can contribute to their virulence. Additionally, they are known to be beta-lactamase producers, which can confer resistance to certain antibiotics.

50
Q

Where in the body does Citrobacter usually colonize?

A

Citrobacter usually colonizes the urinary tract and its colonies can even be separated from the respiratory tract.

51
Q

What infections can Citrobacter cause?

A
  • Intra-abdominal infections
  • Soft tissue infections
  • Osteomyelitis
  • Bacteremia in case of invasive surgery
52
Q

What does Citrobacter koseri cause?

A

C. koseri causes a severe case of neonatal meningitis which is accompanied by necrotizing encephalitis and brain abscesses

53
Q

Which enterocobacteriaceae is a more familiar urinary tract isolate

A

Providencia Stuartiii

54
Q

Which enterobacteeiacieae is a less frequent nosocomial isolate, usually from urine or wounds?

A

Morganella morganii

55
Q

Which types of enterobacteriaceae are beta lactamase producers?

A

All

56
Q

Which enterobacteriacieae are occasional and transient bacteria of the digestive tract

A

Citrobacter, Serratia, Morganella, and Enterobacter

57
Q

What are the species of Proteus

A

Proteus mirabilis and Proteis vulgaris

58
Q

What is special about proteus when cultured on Macconkey agar

A

Proteus are swarming bacteria, meaning they tend to clump together are not distinguishable when seen on Macconkey agar.

59
Q

What are some consequences of Proteus infections?

A
  • Struvite stones
  • UTI
  • Urethritis
  • Pyelonephritis
  • Cystisis
  • Prostitis after UTI
60
Q

How does Proteus create struvite stones?

A

Proteus has an enzyme called urease which converts urea in urine into ammonia. This alkanizes the pH of urine, causing substances like Calcium carbonate and ammonium phosphate to precipitate.

61
Q

What is the most common clinical manifestation of Proteus?

A

UTI

62
Q

Who is at risk of UTI by Proteus

A

Normal hosts
Hosts with indwelling catheters
Hosts with abnormal urinary tracts

63
Q

Can proteus be separated from the bloodstream why?

A

Yes. Proteus can be disseminated until the bloodstream post UTI infection or post indwelling catheters

64
Q

Some enterobacteriaceae are motile. True or false?

A

True. (E.coli, Proteus, Salmonella, Klebsiella, Citrobacter….)

65
Q

What are the differential media used to identify enterobacteriaceae?

A
  • Blood agar (BA)
  • MacConkey agar (MAC) (not resistant to proteus swarming) (lactose fermenters)
  • Eosin Methylene blue agar (EMB) —-> Chromogenic (lactose fermenters)
  • Cystine- lactose-electrolyte- deficient (CLED) agar —-> against proteus swarming
66
Q

What are the selective enteric media used to identify enterobacteriaceae?

A
  • Xylose-lysine- desoxychocolate agar (XLD) agar (black colonies = Salmonella)
  • Salmonella- Shigella (SS) agar
  • Hektoen enteric agar
  • Sorbitol- MacConkey agar ——> Identifies EHEC O157:H7 (doesn’t ferment sorbitol)
  • Chromogenic
67
Q

Why is the use of selective enteric media important for the growth of stool specimens like Salmonella or Shigella?

A

Highly selective or organism-specific media are useful for the recovery of organisms such as Salmonella and Shigella in stool specimens, where an abundance of normal flora

68
Q

Which are the ONLY species that are oxidase positive and aerobic?

A

Neisseria and Moraxella

69
Q

What different laboratory tests are used for the identification of Enterobacteriaceae?

A

Oxidase test
Motility test
Citrate test
Indole test
Methyl Red test
Voges Proskauer test
Lysine decarboxylase agar (LDC)
Ornithine decarboxylase agar (ODC)
Kligler iron agar

70
Q

What are indicators of positive and negative Citrate test ?

A

Green —-> -
Blue ——> +

71
Q

What are indicators of positive and negative indole test?

A

Green —-> -
Purple ——> +

72
Q

What are the indicators of the Methyl Red test? Why?

A

Red —-> positive
Bacteria ferments glucose into acids. The acid production turns the yellow agar red.

73
Q

What are the indicators of the Voges Proskauer test? Why

A

Red—-> +
When Bacteria ferments glucose it forms a neutral end product called acetylmethyl carbinol (acetoin). In the presence of 40% KOH, acetoin is converted into diacetyl and alpha-napthol which give a pinkish red color

74
Q

What are the indicators of the LDC and ODC test? Why?

A

Purple —-> +

LDC:
1) Bacteria ferments glucose and the originally purple agar turns yellow upon acidification
2) In an acidic pH, lysine decarboxylase is activated and decarboxylates L-Lysine to form Cadaverine
3) This results in a purple color again

ODC:
1) Bacteria ferments glucose and the originally purple agar turns yellow upon acidification
2) In an acidic pH, ornithine decarboxylase is activated and decarboxylates Orthinine
3) This results in a purple color again

75
Q

How is enterobacteriaceae infection commonly treated?

A

Non-specific supportive therapy, including hydration, is important.

76
Q

What antibiotics might be given to someone with an enterobacteriaceae infection?

A

Quionolones, Beta lactam (Carbapenems (Imepenem) Cephalosporins), Aminoglycosides, trimethoprim-
sulfamethoxazole

Bacteriology (11 decks)

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