Gram Negative Bacteria

Gram Negative Bacteria

1)  Some procedures are performed in vitro and some are performed in vivo. What does that mean? / In vitro means the procedure is done in a lab, such as injecting a sperm cell into an egg in a Petri dish to fertilize the egg.
In vivo means the procedure is in a live organism, such as implanting a fertilized egg into a woman.
2)  What characteristics do Enterobacteriaceae have? / Gram negative rods
Most are motile (peritrichous flagella)
Encapsulated
Virulence factors include LPS, O, H, and K antigens
Many have “serum resistance” (Ab’s can’t attack)
3)  What diseases are Enterobacteriaceae associated with? / Enteric (GI) infections
Bacteremia
UTI’s
4)  Who is at high risk for acute diarrhea? / Travelers
Consumers of certain foods
Immunocompromised
Daycare participants
Institutionalized persons (nosocomial infections)
5)  What foods put a person at risk for getting acute diarrhea? / -  Chicken, mayonnaise, creams, eggs (Salmonella, Campylobacter, Shigella)
-  Hamburger undercooked (EHEC – enterohemorrhagic E. coli
-  Fried rice (B. cereus)
-  Seafood (Salmonella, Vibrio, Hepatitis A)
-  Fermented tofu (C. botulinum)
6)  What Gram negative bacteria most commonly cause acute diarrhea? / ETEC – enterotoxigenic E. coli
Shigella
Salmonella
Campylobacter
Giardia
7)  What are the treatments for GI diseases such as acute diarrhea? / -  Fluid/electrolyte replacement
Dehydration is the most common cause of death from diarrhea
-  Antibiotics are not used after onset of symptoms unless systemic/severe
-  Antibiotic prophylaxis when traveling to high-risk countries
8)  Enteric infection symptoms / Non-inflammatory
-  Nausea
-  Vomiting
-  Diarrhea
Inflammatory
-  Dysentery (severe diarrhea containing mucus and/or blood)
Invasive
-  Typhoid Fever (enteric fever)
I / II / III
Mechanism: / Non-inflammatory
(enterotoxin) / Inflammatory (invasive, cytotoxin) / Penetrating
(invasive, spread)
Location: / proximal small bowel / colon / distal small bowel
Illness: / Diarrhea / Dysentery / Enteric fever
Stool exam: / no fecal leukocytes / blood, fecal PMNs
(polymorphonuclear leukocytes = neutrophils) / fecal mononuclear leukocytes (monocytes, lymphocytes)
Example organisms: / E. coli
Salmonella
V. cholerae
Campylobacter
Giardia
Cryptosporidium
Rotavirus / Shigella
Invasive E. coli
S. enteritidis
C. difficile
E. histolytica
B. coli / Salmonella typhi
Yersinia enterocolitica
9)  What is the mode of transmission (MOT) of most enteric bacteria? / fecal-oral contamination
10) What are 3 factors the host might have that increase risk of infection by enteric bacteria? / Low gastric acidity
low numbers of normal enteric microflora
immunocompromised
11) Pathogenicity of enteric bacterial toxins: / usually ingested as preformed toxins
12) Example of a Gram positive organism that makes toxins / Staphylococcal toxins (Staph. aureus)
13) Example of neurotoxin / Botulinum toxin (Clostridium. botulinum)
14) Enteric Toxins
15) What are 2 examples of Enterotoxins? / having a direct effect on intestinal mucosa (elicit fluid secretions)
Cholera toxin (Vibrio. cholerae)
E. coli toxins
16) What are attributes of Cytotoxins
17) What are examples of Cytotoxins? / mucosal destruction (often see dysentery)
Shigella dysenteriae
Clostridium perfringens
S. aureus
Clostridium difficile
18) What are attributes of Enterobacteriaceae? / Ubiquious (they are everywhere) - soil, water, vegetation, normal intestinal flora
Gram negative, facultative anaerobic rods
oxidase negative - no cytochrome oxidase
19) Enterobacteriaceae are members of family commonly associated with human disease: / Escherichia
Salmonella
Shigella
Yersinia
Klebsiella
Serratia
Proteus
20) Enterobacteriaceae pathogens are associated with what opportunistic infections? / septicemia
pneumonia
meningitis
urinary tract infections (UTI)
can also be primary pathogens (unrelated to immune status)
21) Are E. coli and the serotypes Lactose positive or Lactose negative? / Lactose positive
note: many intestinal pathogens are lactose negative
ex. Salmonella, Shigella, Yersinia
22) How are E. coli and the serotypes grouped? / grouped based on surface antigens (serotypes)
O antigen (lipopolysaccharide)
H antigen (flagellar)
K antigen (capsular)
O157:H7 (EHEC – enterohemorrhagic E. coli)
O148:H28 (ETEC – enterotoxigenic E. coli)
23) Describe E. coli serotype differentiation / immunologic assay
growth on MacConkey agar with sorbitol (called S-Mac media)
most E. coli can ferment sorbitol (form pink colonies)
E. coli O157:H7 does not ferment sorbitol (colonies are clear/colorless)
24) Describe E. coli pathology / most strains of the pathogenic E. coli are capable of pathology only within the intestinal tract (some exceptions)
most pathogenic strains associated with disease in developing countries (except EHEC is common in the USA)
dependent upon strain, different disease severity/symptoms (e.g. pathotype)
25) Pathogenic strains produce virulence factors found on: / Plasmids (a DNA molecule that is separate from, and can replicate independently of, the chromosomal DNA)
Bacteriophages (viruses that infect bacteria
26) Virulence factors include: / Fimbriae (allow bacteria to stack up on each other to shelter themselves from immune system
secretion systems (the process of toxin release) and toxins
27) Pathogenic strains of E. coli include: / EPEC (enteropathic)
ETEC (enterotoxic)
EHEC (enterohemorrhagic)
EIEC (enteroinvasive)
EAEC (enteroaggregative)
UPEC (uropathogenic)
28) What happens when there is destruction of the surface microvilli (small intestines) / fever
diarrhea (infantile)
malabsorption of fluids
vomiting/nausea hard to replace fluids
non-bloody stools
common in developing countries (rare in U.S.)
29) Since EPEC pathology - diarrhea is primarily a disease of the young (less the 6 months old), what must be replaced? / fluid replacement is important
30) What are symptoms of EPEC pathology- diarrhea? / ~intense vomiting - i.v. fluids are usually required
~disease self-limiting (antibiotics usually not required)
breast feeding seems to have a strong protective effect
IgA and other factors decrease bacterial attachment
31) Enterotoxigenic E. coli (ETEC) is also known as? / “Traveler’s diarrhea”
32) What are the types of ETEC toxins? / heat labile toxins (LT)
similar to cholera toxin (although not as severe)
lack of absorption of fluids = watery diarrhea
heat stabile toxins (ST)
no inflammation, self-limiting
33) ETEC strains are / disease is self-limiting, watery diarrhea common symptom
exposure provides immunity
adults living in endemic areas, often immune
children, through exposure to the many strains, eventually develop immunity
34) Therapy for ETEC includes: / ~fluid replacement
~bismuth subsalicylate tablets (Pepto-Bismol, etc.)
~provide antibiotics to travelers in the event they get sick while abroad
35) Enterohemorrhagic E. coli (EHEC) is usually classified as: / usually O157:H7
strain must have virulence/toxin genes.
36) What are VTECs? / Vero toxin (VTEC) = “shiga-like” toxin (cytotoxin) aka Shiga toxin-producing E. coli (STEC)
37) What does an AB toxin cause? / “A” inactivates 28S rRNA = stop protein synthesis. Death of epithelial cells
38) Characteristics of Streptococcus / •  Gram-positive cocci, arranged in pairs or chains, that are facultative anaerobes
•  Often categorized based on the Lancefield classification
Divides the streptococci into serotype groups based on the bacteria’s antigens
Lancefield groups A and B include the significant streptococcal pathogens of humans
39) Strep classification / Group A (GAS) Strep pyogenes
Group B Strep agalactiae
Group D Enterococcus faecalis
Viridans Strep mutans
40) Identification of S. pyogenes / Hemolysis - beta
Bacitracin - sensitive
41) Identification of S. agalactiae / Hemolysis – beta
Bacitracin - resistant
42) Identification of S. pnumoniae / Homlysis – Alpha
Bacitracin - resistant
43) Identification of E. faecalis / Hemolysis – Alpha or gamma
Bacitracin - resistant
44) Characteristics of Stre[tococcus Pyogenes / •  S. pyogenes forms white colonies surrounded by zone of beta-hemolysis on blood agar plates
•  Only GAS species
•  Pathogenic strains often form a capsule
45) Group A streptococci generally only cause disease in the following situations / •  Normal microbiota are depleted
•  Large inoculum enable the streptococci to establish themselves before antibodies are formed against them
•  Specific immunity is impaired
•  Direct contact with mucous
46) Group A streptococci Pathogenicity / •  Structural components
Protein M, which interferes with opsonization and lysis of the bacteria and a hyaluronic acid capsule, which acts to camouflage the bacteria
•  Enzymes
Streptokinases, deoxynucleases, and C5a peptidase all facilitate the spread of streptococci through tissues
•  Pyrogenic toxins that stimulate macrophages and helper T cells to release cytokines
•  Streptolysins lyse red blood cells, white blood cells, and platelets
47) Group A Streptococcal Dieseases / •  Pharyngitis (“strep throat”)-inflammation of the pharynx
•  Scarlet fever-rash that begins on the chest and spreads across the body
•  Pyoderma-confined, pus-producing lesion that usually occurs on the face, arms, or legs (Impetigo)
•  Streptococcal toxic shock syndrome-bacteremia and severe multisystem infections
48) What is the major species of Salmonella? / S. choleraesuis
49) Which organisms cause enteric fever? / S. choleraesuis ssp. Choleraesuis, serovar typhi (often just called S. typhi, or a better designation is Salmonella Typhi)
50) How is S. enterica ssp. enterica serotype typhimurium shorted? / It is shortened to S. typhimurium (Salomonella Typhimurium)
51) With Salmonella subtyping, how are serotypes determined? / 1. O antigen (LPS outer sugars)
2. Surface Vi antigen (only in sub-types)
Capsule antigens (vi=virulence antigens)
3. H antigens (flagella)
52) How do most clinical labs divide Salmonella into serogroups? / Serogroups (A, B, C1, C2, D, and E) based on O-antigen antisera
53) What causes Salmonella diseases? / Ingestion of bacteria from contaminated food/water and affects the human intestinal tract.
54) What happens when bacteria from Salmonella diseases get to the in the intestinal tract? / Organisms get to the small intestines, where the macrophages often ingest bacteria, however the bacteria are protected from host responses (e.g. complement, antibodies, etc)
55) How does Salmonella alter host cells? / changes host cell to allow for “bacteria-mediated endocytosis (absorbing a substance from outside the cell)”prevents lysosomal enzymes of macrophage from degrading bacteria
56) With Salmonella pathology, the bacteria is disseminated by macrophages to which areas? / The liver, spleen, lymph nodes and bone marrow.
57) What causes systemic symptoms? / These are due to host responses against pathogens
58) What are inflammatory cytokines? / Inflammatory cytokines are secreted by activated macrophages. (Cytokines are chemicals that call other WBCs to come to the area)
59) How rare is typhoid Salmonella infections? / It is very rare in the U.S., however 21 millions infections worldwide (~200,000 deaths)
60) Compared to typhoid Salmonella, how common is non-typhoid Salmonella? / Non-typhoid is much more common. Humans acquire infections from poultry/eggs, dairy, and contaminated work surfaces (cutting boards). In the U.S. ~40,000 reported cases (estimated 2 million)
61) What is Enteric (typhoid) fever? / It is a systemic disease caused by S. Typhi or S. Paratyphi. It is endemic (only occurs in developing countries. ~70% of U.S. cases are acquired from international travel)
62) How are Typhoid Fever and Enteric Fever similar and different? / Similar: Fever, nausea, rash and other systemic symptoms. Was originally called typhoid fever because of the similar symptoms to typhus.
Differ: Different bacteria, different mechanism of spreading
63) How is Enteric fever acquired and who are its host? / The disease is from ingesting contaminated food, and the only known host is humans.
64) Is the infectious dose low or high? / Dose is low. (~103 versus 106-108 for infections with other species of Salmonella)
65) What are the clinical manifestations? / -febrile illness
-disease more severe by S. typhi as compared to S. paratyphi
-after 10-14 days of initial infection, patients have gradually increasing fever, headache, myalgia (muscle pain), malaise (fatigue).
-at around 21 days after infection, GI symptoms present (not seen in all patients) – diarrhea
66) What is one reason why it is difficult to diagnose Typhoid Fever? / The variable numbers of bacteria throughout the infection
67) What are 3 potential cultures (specimens) that can be used to test a positive diagnosis for Typhoid Fever? / 1)  Stool
2)  Urine
3)  Bone marrow
68) What does MDR mean? / Multi-drug resistant
69) Are some strains of S. Typhi MDR? / YES
70) What causes gastroenteritis? / Salmonella
71) What are 4 symptoms of acute gastritis? / Vomiting, abdominal pain, fever, and diarrhea
72) What causes shigella? / Acute infectious inflammatory colitis
73) Is mortality from shigella more common in children or adults? / Children
74) Is shigella a pathogen of animals or humans? / Humans
75) Is it easy to spread shigella to others? / Yes, it is highly communicable
76) What are the clinical manifestations of Shigella? / abdominal cramps, diarrhea, fever, bloody stools and large numbers of WBC in stool
77) What do Shigella virulence proteins cause? / Ruffling of epithelial cells, allows for endocytosis of the bacteria, actin rearrangement allows for cell-to-cell spread.
78) S. dysenteriae produces what toxin? / S. dysenteriae produces shiga toxin (similar to EHEC)
79) What are the enteric pathogens of Yersinia? / Y. enterocolitica, Y. pseudotuberculosis
80) Y. pestis is also known as what? / The bubonic and pneumonic plague
81) The zoonotic disease Yersinia is primarily found in what animals? / Fleas, rodents, swine, cattle, etc
82) The formation of bubos is found in what disease? / Y. pestis
83) What is the mortality rate of untreated patients suffering from the pneumonic plague? / High mortality rate - 90%
84) Is Y. entrocolitica or Yersinia sp. more common? / Y. entrocolitica
85) Does Y. entrocolitica cause severe or acute enterocolitis? / acute enterocolitis and mysenteric lymphadenitis (can mimic appendicitis)
86) How many different serotypes of Y. enterocolitica are there? / Over 60 (serotypes 3,8, &9 account for most human infections
87) Y. entrocolitica is associated with what risk factors? / Ingestion of contaminated food/ milk (can grow at lower temperatures 4C), blood transfusion septicemia
88) Yersinia can be diagnosed from what type of samples? / Blood or stool
89) What is cold enrichment? / Growth culture at 4-7C for 28 days w/ weekly subculture on SS agar
90) What are the therapies for Yersinia? / Plague- antibiotics and rodent control Enteric- often self limiting
91) What are two major pathogenic species of Neisseria? / N.  gonorrheae- associated with STDS
N. meningitidis- associated with respiratory and CNS infections
92) In vitro growth is found in: / Obligate aerobes
Sensitive to drying ( delicate) and some products in blood(that is why one uses Chocolate agar for culture
fastidious-picky
Out-competed by normal flora so grow in presence of select antibiotics(Thayer-Martin agar)