Gram Negative Bacteria of Medical Significance Flashcards
Whats the difference in the cell wall of gram pos and neg bacteria?
2
Thin peptidoglycan layer of the cell wall (Gram + have a much thicker peptidoglycan layer) is sandwiched between an inner cytoplasmic cell membrane and the bacterial outer wall membrane
Do not form spores
All have a lipopolysaccharide outer membrane of cell wall. What does this often act as?
endotoxin
Medically relevant gram negative cocci include three species responsible for:
Gonorrhea
Meningitis
Pneumonia
Medically relevant gram negative bacilli include a multitude of species responsible for:
3
Respiratory illness
Urinary infections
GI problems
….and many other ailments
If gram neg bacteria enter the blood stream, the LPS can cause a toxic reaction which results in what?
3
What could this lead to?
fever, increased respiratory rate, low blood pressure
endotoxic sepsis and shock
The presence of LPS also triggers what?
- an innate immune response and
2. production of cytokines, which in turn, leads to inflammation, which can also produce host toxicity
Gram Negative Cocci
2 genera?
Neisseria
Moraxella catarrhalis
Where does M. cat reside (1)and what can it cause?2
resides in respiratory tract
-causes tracheobronchitis and pneumonia
Describe Neisseria species?
movement?
grouping?
oxygen?
Non-motile, Gram negative
Usually diplococci
Aerobic
Neisseria meningitidis causes?2
Neisseria gonorrhea causes?
Neisseria meningitidis - Meningitis/septiceimia
Neisseria gonorrheae - Gonorrhea
Gonorrhea causes what in women and what in men?
1 in each and 2 shared
Infection of cervix
Infection of urethra (men, inflammatory response => purulent discharge)
Pain and fever
Gonorrhea infections in men can extend to what?
In women can extend to what?
Male infection may extend to prostate and epididymis, causing sterility
Can extend to fallopian tubes and create scar tissue and ectopic pregnancy
Gonnorrhea can Progresses to systemic disease:
3
Neonatuem
arthritis, endocarditis, meningitis
Only natural reservoir for Neisseria meningitidis?
How is it transferred?
human nasopharyngeal mucosa
direct contact or droplet
Describe the Subclinical/minimal disease of Neisseria meningitidis?
transient meningococcemia, short febrile flu-like episode, cleared spontaneously
Describe Fulminant meningeal sepsis (FMS)?
Will the blood culture be pos?
Symtpoms?
9
massive and rapid proliferation in bloodstream
blood culture positive, usually also involves meninges
rapid clinical deterioration
Fever, severe headache, vomiting, neck/back pain, stiffness, petechial rash, altered mental status, shock, organ failure
Describe the symtpms of meningitis?
7
Fever, headache, vomiting, neck/back pain, irritability, skin rash, AMS
What does bacteria invade in menigitis?
What products cause much of the damage in menigitis?
bacterial invasion of meninges, rapid proliferation in CSF
Endotoxins and PMN products/inflammatory mediators
FMS/Meningitis shock is when what happens?
4
endotoxin
causes capillary leakage, poor vascular tone, intravascular microthrombi, myocardial dysfunction
FMS/Meningitis caused DIC can lead to what? 2
What two things are released that causes this?
endothelial damage => hemorrhages, microthrombi
Endotoxin AND cytokines
Early diagnosis of FMS or meningitis is difficult, but crucial
What are the later stages of FMS?
What are the later stages of menigitis?
skin lesions appear after 6 - 12 h, easier to recognize disease
Meningitis: skin lesions 12 - 18 h after onset, no lesions in 20% of patients
Bacteriologic diagnosis of
FMS?
Bacteriologic diagnosis of menigitis?
FMS: Gram stain of skin lesion biopsy specimen
Meningitis: only CSF positive
Most important therapeutic principles of meningitis?
2
- therapy should never be delayed by diagnostic procedures
2. antibiotics are the most important part of treatment
What is the first line treatment for menigitis?3
How would we treat pts in contanct with menigitis prophylactically?
Cefotaxime or ceftriaxone plus vancomycin
Patients in contact……………prophylactic ABX Rocephin (cefatriaxone)
Mortality with treatment for meningitis?
without treatment?
Neurological sequelae in 8 - 20% of survivors: What are these?
3
deafness,
mental retardation, concentration disturbances
Moraxella catarrhalis
is a gram negative cocci that causes infections of what?
5
- Upper and lower respiratory
- Middle ear
- Eye
- CNS
- Joints
Moraxella catarrhalis infections of the upper and lower respiratory tract are particularly important in what populations?2
particularly important cause of bronchopulmonary infection in elderly,
patients with chronic lung disease
Moraxella catarrhalis is resistant to what?
3
Resistant to PCNs, SMX/TMP, tetracyclines
What should we treat M. Cat with?
4
Treated with fluoroquinolones,
most 2nd and 3rd ceph, macrolides and
Augmentin
Name the Aerobic Gram-Negative Nonenteric Bacilli?
7
- Pseudomonas and
- Burkholderia – an opportunistic pathogen
- Brucella and
- Francisella – zoonotic pathogens
- Bordetella and
- Legionella – mainly human pathogens
- Alcaligenes – opportunistic pathogen
What are Small Gram-negative rods with a single polar flagellum?
pseudomonas
pseudomonas bacteria are freeliving. Where can they be found?
4
primarily in soil,
sea water, and
fresh water;
also colonize plants and animals
Important decomposers and bioremediators in nature
Where is pseudomonas a frequent contaminant in?
2
homes and clinical settings
What does pseudomonas produce?
3
Produce oxidase and catalase
water soluable pigments
Pseudomonas aeruginosa
is a common inhabitant of what?
soil and water?
pseudomonas is an intestinal resident in what percent of poeple?
What is it resistant to?6
10%
Resistant to soaps, dyes, quaternary ammonium disinfectants, drugs, drying
Pseudomonas is a Frequent contaminant of what in hospitals?
3
ventilators,
IV solutions,
anesthesia equipment
Opportunistic pathogen
Common cause of nosocomial infections in hosts with?3
burns,
neoplastic disease,
cystic fibrosis
Complications caused by pseudomonas cause?
8
pneumonia, UTI, abscesses, otitis, and corneal disease Endocarditis, meningitis, bronchopneumonia
What kind of odor and pigment does pseudomonas have?
Grapelike odor
Greenish-blue pigment (pyocyanin)
What do we treat pseudomonas with?
6
Treated with
- cephalosporins,
- aminoglycosides,
- carbenicillin,
- polymixin,
- quinolones (for ear infections), and
- monobactams
Brucella and Brucellosis
are shaped how?
What are its two species?
Brucellosis is spread how?
How does it present?
How do we treat it?3
Tiny Gram-negative coccobacilli
Brucella abortus (cattle) Brucella suis (pigs)
a zoonosis transmitted to humans from infected animals
Fluctuating pattern of fever……weeks to a year
UNDULANT FEVER
Treated with combination of tetracycline and rifampin or streptomycin
The bacteria can spread to humans with contact with what?
3
- infected meat or
- the placenta of infected animals, or from
- unpasteurized milk or cheese.
Brucellosis in humans is usually associated with the consumption of what?
Clinically manifests how?
unpasteurized mildk and soft cheeses made from the milk of infected animals.
Can be insidious and may present in many atypical forms
UNDULANT FEVER
but may persist and progress to a chronically incapacitating disease with severe complications.
Francisella tularensis and Tularemia is shaped how?
How is it transmitted?3
Clinical manifestations?
10% death rate in which forms? 2
Treatment?3
facultative intracellular coccobacillus
a zoonotic disease. Transmitted by contact with infected animals, water and dust or bites by vectors
Headache, backache, fever, chills, malaise and weakness
in systemic and pulmonic forms
Tx: gentamicin or tetracycline
Attenuated vaccine
Bordetella pertussis
shape?
What does it cause?
Who is it most dangerous in?
Transmission?2
Minute, encapsulated coccobacillus
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 or inhalation of aerosols
Bordetella pertussis
virulence factors?
2
- receptors that recognize and bind to ciliated respiratory epithelial cells
- toxins that destroy and dislodge ciliated cells
What is the pathology of Bordetella pertussis?
Treatment?
Loss of ciliary mechanism leads to buildup of mucus and blockage of the airways.
Treatment- macrolides….Azithromycin
Legionella pneumophila and Legionellosis is widely distributed where?
Tranmitted?
They live in close association with what?
Other names for Legionella pneumophila and Legionellosis? 2
Who is it most prevavalent in?
Its a nosocomial disease in who?
water
Organisms inhaled in aerosolized mist
Live in close association with amoebas
Legionnaires disease and Pontiac fever
Most prevalent in males over 50
Nosocomial disease in elderly patients
Clinical manifestations of Legionella pneumophila and Legionellosis?
5
Fatality Rate?
What should we treat with?
Fever, cough, diarrhea, abdominal pain, pneumonia
fatality rate of 3-30%
Treat with azithromycin
What is The Most Prevalent Enteric Bacillus?
Most common aerobic and non-fastidious bacterium in gut?
Escherichia coli
Its needs are few
Some E. Coli have developed virulence through ?
2
plasmid transfer, others are opportunists.
Enterotoxigenic E. coli causes what?
Due to what?
What is a characteristic of the structure of this E. Coli?
severe diarrhea
due to heat-labile toxin and heat-stable toxin – stimulate secretion and fluid loss;
also has fimbriae (attachment pili)
Enteroinvasive E. coli causes what?
inflammatory disease of the large intestine.
Enteropathogenic E. coli linked to what?
wasting form infantile diarrhea
Enterohemorrhagic E. coli, O157:H7 strain, causes ?
2
hemorrhagic syndrome and kidney damage
Greatest cause of mortality among babies?
Pathogenic strains frequent agents of infantile diarrhea
Causes ~70% of what?
Causes 50-80% of what?
traveler’s diarrhea
UTI
What is Coliform count?
indicator of fecal contamination in water
Most strains of E. Coli will respond to what?
3
SMX/TMP, nitrofurantoin, fluoquinolones
Klebsiella pneumoniae is a normal inhabitant of where?
What should we know about its structure?
What does it cause?5
normal inhabitant of respiratory tract,
has large capsule,
cause of nosocomial pneumonia, meningitis, bacteremia, wound infections and UTIs
Enterobacter sp. infects what?2
UTIs, surgical wounds
Serratia marcescens produces what?
Causes what5
produces a red pigment;
causes pneumonia, burn and wound infections, septicemia and meningitis UTIs
Citrobacter sp. cause what?
2
opportunistic
UTIs and bacteremia
Yersenia Pestis (Plague) is spread by what?
What areas are hardest hit right now?
fleas through rodents
Eastern African nations are hardest hit.
Yersinia pestis and Plague
enteric or nonenteric?
Shape?
Virulence factors?3
nonenteric
Tiny, Gram-negative rod, unusual bipolar staining and capsules
- capsular and envelope proteins protect
against phagocytosis and foster intracellular growth - coagulase,
- endotoxin, murine toxin
Describe the pathology of Yersinia pestis?
Where does it replicate?
What does this cause and what does it block?
bacteria replicates in gut, coagulase causes blood clotting that blocks the esophagus;
flea becomes ravenous
Where does the plague enter after the flea bite?
What does this cause and what is it called?
lymph, causes necrosis and swelling called a bubo in groin or axilla
How does the plague become systemic?
2
- Septicemic – progression to massive bacterial growth; virulence factors cause intravascular coagulation subcutaneous hemorrhage and purpura – black plague
- Pneumonic – infection localized to lungs, highly contagious;
fatal without treatment
Diagnosis of plague depends on what?
3
Treatment?
4
How do we prevent it?2
history, symptoms, and lab findings from aspiration of buboes.
streptomycin, tetracycline or chloramphenicol
vaccine avilable
Prevention by quarantine and control of rodent population in human habitats
Yersinia enterocolitica is found where?
How does this infect the host?
How do they avoid the host defenses?
Clinical manifestation can resemble?
domestic and wild animals, fish, fruits, vegetables, and water
bacteria enter small intestinal mucosa, some enter lymphatics and
survive in phagocytes;
inflammation of ileum can mimic appendicitis
Y. pseudotuberculosis clinically manifests how?
2
localized tissue necrosis and granulomas in the spleen, liver and lymph nodes
TB symtpoms
Y. enterocolitica causes what?
more lymph node inflammation
Pasteruella multocida
(Avian Cholera) found in what?
What kind of infection is it in humans?
How is it transmitted and where does it spread (3)?
Who is at greatest risk
How do we treat?
normal flora in animals
-Follows bird migration
Opportunistic infections in humans
Animal bites or scratches cause local abscess that can spread to joints, bones, and lymph nodes.
Immunocompromised are at risk for septicemia and complications.
Treatment: penicillin and tetracycline
Haemophilus
shape?
What kind of agar does it grow on?
tiny Gram-negative pleomorphic rods
Chocolate agar
H. influenzae causes what?
6
What has really helped with this infection?
acute bacterial meningitis, epiglottitis, otitis media, sinusitis, pneumonia, and bronchitis
subunit vaccine Hib
H. aegyptius causes?
–conjunctivitis, pink eye
H. ducreyi causes?
STD
H. parainfluenzae and H. aphrophilus are find where normally (2) and what does it cause when it becomes pathogenic?
normal oral and nasopharyngeal flora;
infective endocarditis
What do you treat H. Flu with?
5
Treated with
amoxicillin,
azithromycin,
cephalosporins, fluoroquinolones and clarithromycin
Most pathogenic anaerobes are usually commensals and originate where?
Predisposing Conditions?4
Originate from our own flora
1. Breeches in the mucocutaneous barrier → displace normal flora 2. Compromised vascular supply 3. Trauma with tissue destruction 4. Antecedent infection
Clues to Anaerobic Infection
6
- Infections in continuity to mucosal surfaces
- Infections with tissue necrosis and abscess formation
- Putrid odor
- Gas in tissues
- Polymicrobial flora
- Failure to grow in the lab
Classification of bacteria based on previous experiments allowing fast identification is called what?
What other tool is used in diagnosis of anaerobes?
API SYSTEM
GAS CHROMATOGRAPHY
Bacteroides fragilis
is most noted when?
Does it form spores?
Major disease causing strict anaerobic after abdominal surgery
no
Describe how Bacteroides fragilis evades body defenses?
3
Prominent capsule
- anti-phagocytic
- abscess formation
Bacteroides fragilis has an endotoxin affect but low toxicity. Why?
structure different than other lipolysaccharide
A leading cause of bacterial diarrheal illness?
How is it transmitted?
What is this bacteria associated with? 3
What should we treat with (what is it becoming resistant with)?
Campylobacter jejuni
oral/fecal route, ingestion of contaminated food and water, uncooked meat
Associated with feed lots, chicken houses, raw milk
Treated with azithromycin, increasing resistance to fluoroquinolones
What is Borrellia burgdorferi?
Early symtpoms include?4
(whats the buzz word?)
Lyme disease
fever, headache, and fatigue, bull’s eye rash
If lyme disease is left untreated later symptoms may involve what?
3
Usually treated by what well?
the joints, heart and central nervous system.
DOXY or Amox (2-4 weeks)
How do we diagnose Lyme?
3
Unique bull’s eye rash
Elisa
Western Blot
What should we treat Chlamydia trachomatis with?
3 options
What is a complication that could arise?
Treat both partners with azithromycin,
doxycycline or
ofloxocin
blindness
What is Lymphogranuloma venereum(LGV)?
What system does it affect?
Uncommon sexually transmitted infection caused by three invasive serovars of Chlamydia trachomatis
Chronic long term infection of the lymphatic system
Symptoms of Lymphogranuloma venereum(LGV)?
6
- Swollen inguinal nodes
- Drainage through the skin from buboes or abscesses in inguinal nodes
- Painful bowel movements (tenesmus)
- Small painless sore on the genitals
- Swelling of the labia
- Blood or pus from the rectum
HOw do we Lymphogranuloma venereum(LGV)?
How do we treat?
3 options
Diagnosis usually made serologically and by exclusion of other causes of inguinal adenopathy or genital ulcers
doxycycline, erythromycin, azithromycin
Buboes may require incision and drainage
Lymphogranuloma venereum(LGV) prognosis is more favorable with?
Untreated chronic condition may cause?
Prognosis more favorable with early treatment
Untreated chronic condition may cause fistulas of the penis, urethra, vagina, uterus, rectum
Psittacosis is transmitted how?
Symptoms in humans range from what?2
zoonotic disease caused by Chlamydia pssitaci, contracted from parrots, pigeons, ducks, chickens, gulls
range from unapparent to systemic illness with severe pneumonia
Psittacosis may mimic what?
What are the symptoms?
7
As it progresses what does it mimic?
May mimic typhoid in early stages: high fever, arthralgias, diarrhea, conjunctivitis, epistaxis and neutropenia, splenomegaly
pneumonia as it progresses: dyspnea, high fever, cough, patchy infiltrates or whiteout on CXR
Psittacosis diagnosis. What is key??
3
Treatment?
- Diagnosis: exposure history is paramount!
- Microbiological cultures from respiratory secretions or
- serology from blood cultures
Doxycycline and chloramphenicol
What are the two types of Relapsing Fever?
What bacteria is it caused by?
Where is each one found most and which one is more severe?
What are the symtpoms?
Two types: tick borne (TBRF) and louse borne (LBRF)
Caused by Borellia spirochetes
TBRF occurs in western US, linked to sleeping in rustic, rodent infested cabins in mountainous areas
LBRF is transmitted by the human body louse and is generally restricted to refugee settings in third world. Occurs in epidemics, more severe than TBRF
Flu-like symptoms: sudden fever, chills, headaches, arthralgias, nausea. May develop a rash
HOw do we diagnose and treat relapsing fever?
2
1
One big thing to remember
Diagnosis on blood smear…spirochetes
Treatment: doxycycline.
May cause Jarisch-Herxheimer reaction in over half of those treated
Describe the strcuture of Salmonella sp.?
Motile, flagellated gram-neg
What can Salmonella sp. cause? 2
Whats the most common form?
Whats the main reservoir and how can it spread?
Common Salmonella gastroenteritis (diarrhea, abdominal cramps, fever) to enteric fevers (including typhoid fever) which can be life threatening
Most common form AKA “food poisoning” presents with uncomplicated gastroenteritis, usually self-limited disease
animals are main reservoir, usually food borne illness, can spread from person to person
Enteric Typhoid Fever-severe systemic disease, any species of salmonella may cause, S. typhi most studied.
What are the symtpoms? 6
How do we diagnose?3
How should we treat?3
N/V/D
septicemia
Fever, anorexia, headache, myalgias
Dx: stool and/or blood cultures, serology for antibodies
Often fatal if not treated
Replace fluids by oral or IV
Pain control and treating nausea and vomiting
Antibiotics…..ciprofloxacin
What is Shigella (clinical manifestations)?
What demographic is it commonly seen?
How is it transmitted?
Diagnosis?
Treatment?3
Intestinal disease
Bloody diarrhea, may have abdominal pain or cramps, fever
children 2-4
Passed through direct contact with stool
Dx: stool studies
Replace lost fluids, water or Pedialyte, may need IV fluids
Increasing resistance to abx…. ciprofloxocin or cefixime should be used if abx indicated
Vibrio sp. has two distinct groups?
Most non-cholera vibrio infections are associated with what?
Cholera infections
Non-cholera
improperly cooked contaminated food or eating raw shellfish
Non-cholera (vibro) wound infection or septicemia will need what for treatment?
doxycycline or a quinolone, aggressive fluid replacement, vasopressors for hypotension, fasciotomy, debridement of infected wound
Vibrio cholerae
buzzword?
Treatment?
profuse watery diarrhea
doxycycline or a quinolone, aggressive fluid replacement
Acinetobacter baumanni buzzword?
3 things
Commonly isolated from the hospital environment and hospitalized patients
Often cultured from sputum, respiratory secretions, wounds, urine….colonization vs infection
HOSPITAL ACQUIRED OFTEN
CULTURED FROM SECRETIONS
ICU
Acinetobacter baumanni treatment?
Multi-drug resistance……including carbapenems
