Gram Negative Pathogens Flashcards
1
Q
Gram Negative Cell walls
A
- consists of thin layer of peptidoglycan surrounded by cell membrane
- outer membrane composed of lipids, lipoproteins and LPS
- no teichoic acids
2
Q
LPS
A
- three parts: lipid A, core polysaccharide, O side chain (O antigen)
- lipid A embedded in outer membrane
- core polysaccharide, O side chain extend out from cell
3
Q
Cocci - gram neg
A
- residents of mucous membranes if warm blooded animals
- genera: Neisseria (gonorrhoeae and meningitidis)
4
Q
Neisseria - cocci - Gram neg
A
- bean-shaped, diplococci
- nome develop flagella so they are non-motile
- capsules on pathogens
- pill
- strict parasites, do not survive long outside host
- aerobic or micro aerophilic
- catalase +
- oxidase + ( produce cytochrome oxidase)
- pathogenic species require enriched complex media (chocolate agar)
5
Q
Neisseria gonorrhoeae
A
- causes gonorrhea
- contains fimbriae, other surface molecules for attachment; slows phagocytosis
- IgA protease - cleaves secretory IgA
- strictly a human pathogen
- in top 5 STD
- infectious dose 100-1,000
- does not survive more than 1-2 hours on fomites
- genital gonorrhea in males: urethritis ( yellowish discharge, scarring, and infertility)
- 10% of men are asymptomatic
- genital gonorrhoeae in women: vaginitis, urethritis, salpingitis (PID) mixed anaerobic abdominal infection, common cause of sterility and ectopic tubal pregnancies
- 50% of females are asymptomatic
- anal intercourse can cause proctitis, and oral sex can result in pharyngitis and gingivitis
- careless personal hygiene can account for self-inoculation of the eyes and a serious form of conjunctivitis
- in small number of cases the gonococcus enters the bloodstream and is the joints and skin - chronic arthritis and rash on the limbs
- rare complications are meningitis and endocarditis
- infants born to gonococcus carriers are in d aged of being infected as they pass through the birth canal - eye inflammation, blindness, pharynx and respiratory tract or neonates might also be affected - prevented by prophylaxis immediately after birth
- 20-30% of new cases are penicillinase-producing PPNG or tetracycline resistant TRNG
- combined therapies indicated
- recurrent infections can occur
- reportable infectious disease
6
Q
Neisseria Meningitidis
A
- virulence factors: capsule, adhesive fimbriae, IgA protease, endotoxins
- 12 strains, serotypes A, B, C cause most cases
- prevalent cause of meningitis; sporadic or epidemic
- human reservoir - nasopharnyx; 3-30% of adult population - High risk individuals: those living in close quarters, children 6 mo-3 yr, children and young adults 10-20 years
- when bacteria enter bloodstream, cross the blood-brain barrier, permeate the meninges, and grow in the cerebrospinal fluid
- very rapid onset; neurological symptoms
- the release of endotoxins during meninggoccemia may cause hemorrhage, coagulation, and vascular damage, leading to necrosis of tissue, especially in the extremities
- crops of lesions called petechiae develop on the trunk and appendages in about half of the cases (DIC)
- diagnoses through gram stain CSF, blood or nasopharyngeal sample - culture for differentiation - rapid tests for capsular polysaccharide
- immunity, treatment, and prevention of meningococcal infection: treated with IV penicillin G and cephalosporin - prophylactic treatment of family members, medical personnel, or children in close contact with patient - primary vaccine contains specific purified capsular antigens
7
Q
Aerobic nonenteric Bacilli - gram neg
A
- large diverse group of non-spore-forming bacteria
- wide range of habitants, large intestines (enteric),zoonotic, respiratory, soil, water
- most are not medically important; some are true pathogens, some are opportunistis
- all have outer membrane LPS of the cell wall - endotoxin
- pseudomonas and burkholderia - opportunistic pathogens
- bordetella and legionella - mainly human pathogens
8
Q
Pseudomonas aeruginosa - bacilli - aerobe - gram neg
A
- common inhabitant of soil and water (everywhere)
- intestinal resident in 10% normal people
- resistant to soaps, dyes, quats, ammonium disinfectants, drugs, drying
- frequent contaminant of ventilators, IV solutions, anesthesia equipment
- opportunistic pathogens
- common cause of nosocomial infections in hosts with burns, neoplasticism disease, CF
- complications include pneumonia, UTI, abscesses, otitis, and corneal disease
- endocarditis, meningitis, bronchopneumonia
- grapelike odor and greenish-blue pigment (pyocyanin)
- multi drug resistance
9
Q
Bordetella pertussis - bacilli -aerobe - gram neg
A
- minute encapsulated cocccobascillus
- causes pertussis or whooping cough, a communicable childhood affliction
- acute respiratory syndrome
- often severe, life-threatening complications in babies
- reservoir - apparently healthy carriers
- transmission by direct contact of inhalation of aerosols
- virulence factors: receptors that recognize and bind to ciliated respiratory epithelial cells
- toxins that destroy and dislodge ciliated cells
- adhesions and toxins mediate disease: pertussis toxin, adenylate Cyclase toxin, dermonecrotic toxin, tracheal cytotoxin
- loss of ciliary mechanism leads to buildup of mucus and blockage of the airways
- vaccine: DTaP (accellular vaccine with toxoid and other antigens)
10
Q
Progression of Pertussis
A
- Incubation: no symptoms
- Catarrhal: rhinorrhea, sneezing, malaise, fever
- Paroxysmal: repetitive cough with whoops, vomiting, exhaustion
- Convalescent: diminishing cough, possible secondary complications.
11
Q
Enterobacteriaceae - facultative anaerobes - bacilli - gram neg
A
- two categories: opportunistic and true pathogens
- large family of small, non-spore-forming rods
- many members inhabit soil, water, decaying matter, and see common occupants of large bowel of animals
- most frequent cause of diarrhea through enterotoxins
- “enteric” along with pseudomonas account for almost 50% of nosocomial infections
- antigens: outer membrane (lipid A and O antigen [somatic/cell wall antigen] ), Type III secretion system, capsular/fimbrial antigen (K) and Vi in Salmonella, flagella antigens (H)
*not all have H and K, but all have O, implicated in endotoxins shock - the pathogen is of enterics is also tied to their production of endotoxins, exotoxins
- virulence factors: fimbriae, exotoxin, adhesion, plasmid (virulence genes), iron-binding protein, hemolysin
12
Q
Opportunistic Enterobacteriaceae
A
- e. Coli, klebsiella, Enterobacter, serratia, proteus, citrobacter
- divided into two categories: coliforms (lactose fermenters) and non-coliforms (non-lactose fermenters)
- enrichment, selective and differential media utilized for screening samples for pathogens
13
Q
Escheria coli - enteric bacillus - opportunistic - gram neg
A
- most common aerobic and non-fastidious bacterium in gut
- 150+ strains - some with virulence by plasma transfer, others are opportunists
- most clinical cases are transmitted exclusively among humans
- pathogenic strains frequent agents of infantile diarrhea - greatest cause of mortality among babies
- causes 70% of travelers diarrhea
- causes 50-80% UTI
- oral antimicrobials may be effective in the early phases of infection
- over the counter preparations for symptom relief slow gut motility, so it can also serve to retain the pathogen for longer
- peptobismal is more effective, as it counteracts the enterotoxin and also provides antimicrobic effect
- pathotypes
1. Enter-hemorrhagic (EHEC): hemorrhagic syndrome and kidney damage - shiva-toxin (STEC)
2. Entertoxigenic (ETEC): severe diarrhea due to heat-labile toxin and heat-stable toxin - stimulate secretion and fluid loss; also has fimbriae
3. Enter-invasive (EIEC): inflammatory disease of the large intestine
4. Enteropathogenic (EPEC) : linked to wasting form infantile diarrhea
5. Enteroaggregative (EAEC): common cause of pediatric diarrhea
6. Diffusley adherent (DAEC): minor cause of pediatric diarrhea
14
Q
E. Coli in food infections
A
O157:H7 (somantic O type 157 and flagellar H type 7)
- enter-hemorrhagic strain involved in infections from fast-food hamburgers in 1993 - reservoir in cattle intestine
- virulence due to a cell wall receptor that can fuse with the host cell membrane, creating a direct port into which the bacteria secrete toxins (TTSS)
- shiva toxin - the toxin enters the host cell, binds ribosomes, and disrupts protein synthesis, leading to death and shedding of intestinal cells
- shiga-toxin dissemination leads to hemolytic uremic syndrome (HUS) in 10% - often fatal
- testing in commercial meat is performed randomly - USDA requires that all fresh meat near warning labels to remind consumer of safer handling
15
Q
Klebsiella Pneumoniae - Coliform - obligate enteric - facultative anaerobe - gram neg
A
- most of these can infect nearly any organ, are opportunistic and drug-resistant
- normal inhabitant of respiratory tract - primarily GI large capsule, cause of nosocomial pneumonia, meningitis, bacteremia, wound infections, and UTIs
- in digestive and respiratory systems of humans and animals
- capsule protects the bacteria from phagocytosis
- can cause opportunistic infections
- lethal pneumonia at any age 18-30
- most commonly isolated pathogenic species
- causes chronic ulcerative bronchitis (pneumonia)
