Transcript P. aeruginosa

Pseudomonas and related organisms
Aerobic gram-negative nonfermentative rods
Pseudomonas aeruginosa: opportunistic infections of
multiple sites
Burkholderia cepacia: RT infection in cystic fibrosis
patients, UTI, opportunistic infections
Burkholderia pseudomallei: opportunistic pulmonary
infections or sepsis
Stenotrophomonas maltophilia: opportunistic infections
Acinetobacter baumannii: opportunistic infections of RT
Moraxella catarrhalis: opportunistic RT infections
Pseudomonas
Structure and
Physiology
Gram-negative rods.
Motile with polar flagella.
Obligate aerobe.
Oxidase-positive.
Do not ferment carbohydrates.
Resistant to multiple drugs.
P. aeruginosa
Forms round colonies with a
fluorescent greenish color, sweet
odor, and b-hemolysis.
Pyocyanin- nonfluorescent
bluish pigment;
pyoverdin- fluorescent
greenish pigment;
pyorubin, and pyomelanin
Some strains have a prominent
capsule (alginate).
Identification of P. aeruginosa is usually based on oxidase test
and its colonial morphology: b-hemolysis, the presence of
characteristic pigments and sweet odor, and growth at 42 oC.
P. aeruginosa
Pathogenesis and Immunity
This organism is widely distributed in nature and is commonly
present in moist environments in hospitals. It is pathogenic only
when introduced into areas devoid of normal defenses, e.g.,
1. Disruption of mucous membrane and skin.
2. Usage of intravenous or urinary catheters.
3. Neutropenia (as in cancer therapy).
P. aeruginosa can infect almost any external site or organ.
P. aeruginosa is invasive and toxigenic. It attaches to and colonizes
the mucous membrane or skin, invade locally, and produces
systemic diseases and septicemia.
P. aeruginosa is resistant to many antibiotics. It becomes dominant
when more susceptible bacteria of the normal flora are suppressed.
P. aeruginosa
Pathogenesis
Antigenic structure,
enzymes, and toxins
Pili and nonpilus adhesins.
Capsule (alginate, glycocalyx):
seen in cultures from patients
with cystic fibrosis.
LPS- endotoxin, multiple
immunotypes.
Pyocyanin: catalyzes
production of toxic forms of
oxygen that cause tissue
damage. It also induces IL-8
production. Pyoverdin: a
siderophore.
Proteases
Serine protease,
metalloprotease and alkaline
protease cause tissue
damage and help bacteria
spread.
Phospholipase C: a hemolysin
Exotoxin A: causes tissue
necrosis and is lethal for animals
(disrupts protein synthesis);
immunosuppressive.
Exoenzyme S and T: cytotoxic to
host cells.
P. aeruginosa
Clinical Diseases
Infection of wounds and burns Ear infections
(blue-green pus). Patients with
Otitis externa: mild in
severe burns may develop into
swimmers; malignant (invasive)
bacteremia.
in diabetic patients.
Skin and nail infections
Chronic otitis media
Meningitis (when introduced by
Osteochondritis of the foot.
lumbar puncture).
Urinary tract infection
Pulmonary infection
Tracheobronchitis
Necrotizing pneumonia in CF
patients: diffuse, bilateral
bronchopneumonia with
microabscess and necrosis.
Eye infections: corneal ulcer.
Sepsis: most cases originate
from infections of lower RT, UT,
and skin and soft tissue.
Ecthyma gangrenosum
(hemorrhagic necrosis of skin)
may be seen in some patients.
P. aeruginosa
Laboratory Diagnosis
Specimen: skin lesions, pus, urine, blood, spinal fluid, sputum.
Culture: blood agar plate and differential media. Identification
of P. aeruginosa is described above.
Several subtyping methods, including phage typing and
molecular typing, are available for epidemiologic purposes.
Treatment
Combined antibiotic therapy is generally required to avoid
resistance that develops rapidly when single drugs are
employed. Avoid using inappropriate broad-spectrum
antibiotics, which can suppress the normal flora and permit
overgrowth of resistant pseudomonads.
P. aeruginosa
Prevention and Control
Pseudomonas spp. normally inhabit soil, water, and
vegetation and can be isolated from the skin, throat, and
stool of healthy persons.
Spread is mainly via contaminated sterile equipments and
cross-contamination of patients by medical personnel.
High risk population: patients receiving broad-spectrum
antibiotics, with leukemia, burns, cystic fibrosis, and
immunosuppression.
Methods for control of infection are similar to those for other
nosocomial pathogens. Special attention should be paid to
sinks, water baths, showers, hot tubs, and other wet areas.
P. aeruginosa
Prevention and Control
Control:
1. Patients at high risk should not be admitted to a ward
where cases of pseudomonas infection are present.
2. Patients infected with P. aeruginosa should be isolated.
3. Sterilize
all instruments, apparatus, and dressing;
antimicrobial and other therapeutic substances.
4. Monitor clinically relevant isolates of P. aeruginosa by a
suitable typing system to identify epidemic strains.
Stenotrophomonas maltophilia
A common nonfermentative, gram-negative isolate.
It infects debilitated or immunocompromised persons,
and causes a wide spectrum of diseases, including
wound infections, UT infections, pneumonia, sepsis,
meningitis, etc.
It is resistant to many commonly used antibiotics, and
patients receiving long-term antibiotic therapy are
particularly at risk for acquiring infections.
Infections may be acquired from iv catheters,
contaminated disinfectants, respiratory therapy and
monitoring equipment, and ice machines.
Burkholderia
They colonize the moist environmental surfaces and are
commonly associated with nosocomial infections.
B. cepacia complex (of 9 species), B. gladioli and B. pseudomallei
are important pathogens.
B. cepacia complex causes RT infections particularly in cystic
fibrosis patients, UT infections and septicemia. Usually non-fatal
except for RT infections in CF patients.
B. pseudomallei usually causes opportunistic infections (called
melioidosis), but may sometimes infect previously healthy
persons. Infection by this organism may result in asymptomatic
infection, acute suppurative cutaneous infection, and chronic
pulmonary infection ranging in severity from mild bronchitis to
necrotizing pneumonia. All may progress to sepsis.
2005/7/30 台南高雄疑似發生類鼻疽疫情，疾病管制局提
醒民眾，皮膚如有傷口，請勿接觸污染的土壤或水源
疾病管制局今天公佈今年自七月11日至29日以來，類鼻疽累計通
報16例，其中高雄縣9例、台南市4例、高雄市2例、台南縣1例。
其中6例死亡，3例在加護病房，另7例住普通病房。類鼻疽係由
類鼻疽伯克氏菌 Burkholderia pseudomallei 所造成的臨床感染
症，屬假單孢菌屬革蘭氏陰性桿菌，此菌在土壤、水池及積水環
境中存在，會感染馬、羊、豬等動物以及人類。其流行地域為東
南亞地區及澳洲北部的熱帶地域。該局自89年即將此病納入監測。
89年通報病例1例、90年15例、91年9例、92年5例、93年13例。
本次疫情發生原因，疾病管制局初步調查研判可能係因日前南部
豪大雨，將土壤中之病菌沖刷出來，所造成的民眾感染事件，病
例多發生在二仁溪流域。該局鄭重呼籲在二仁溪流域附近居民，
若有發燒等症狀者，務必迅速就醫。並告訴醫師居住地區，疾病
管制局呼籲，醫師對於上述地區發燒病患，應先排除感染此病的
可能性，若有懷疑應立即以抗生素治療，並採檢送驗。
Corynebacterium
C. diphtheriae: causes diphtheria.
Other Corynebacterium spp. (> 100 species) and related
genera (coryneform) may cause opportunistic infections.
Gram-positive, irregularly-shaped rods. "Club shaped".
Strains of this genus contain short mycolic acid in the cell wall.
In stained smears, individual rods tend to lie parallel or at acute
angles to one another (palisades). Metachromatic granules
(often near the poles) give the rod a beaded appearance.
Grow aerobically on most media.
Corynebacteria grow on Löffler's
serum medium more readily than
other respiratory pathogens, and
show typical morphology in
smears.
Non-motile; noncapsulate.
C. diphtheriae
Pathogenesis and Immunity
C. diphtheriae occurs in the respiratory tract, in wounds, or on the
skin of infected persons or normal carriers. It is spread by droplets
or skin contact.
Portal of entry: respiratory tract or skin abrasions.
Diphtheria bacilli colonize and grow on mucous membranes, and
start to produce toxin, which is then absorbed into the mucous
membranes, and even spread by the bloodstream.
Local toxigenic effects: elicit inflammatory response and necrosis
of the faucial mucosa cells-- formation of "pseudomembrane“ (composed of bacteria, lymphocytes, plasma cells,
fibrin, and dead cells), causing respiratory obstruction.
Systemic toxigenic effects: necrosis in heart muscle, liver, kidneys
and adrenals. Also produces neural damage.
C. diphtheriae
Clinical Diseases
Respiratory diphtheria
Incubation period: 2-4 days.
Inflammation begins in the respiratory tract, causing sore throat,
exudative pharyngitis that develops into pseudomembrane, and low
grade fever. Prostration and dyspnea soon follow, which may lead to
suffocation if not promptly relieved by intubation or tracheotomy.
Myocarditis causing cardiac arrhythmias develops in many patients.
Visual disturbance, difficulty in swallowing and paralysis of the arms
and legs also occur but usually resolve spontaneously.
Death may be due to asphyxia or heart failure.
Cutaneous diphtheria: mild (papule ulcer with grayish membrane)
with little toxigenic effects. Stimulates antitoxin production.
C. diphtheriae
Laboratory Diagnosis
Specific treatment should be given before the lab reports if the
clinical picture strongly suggests diphtheria.
Specimens: swabs from the nose, throat or suspected lesions.
Gram's stain: beaded rods in typical arrangement (unreliable).
Culture: inoculate specimen onto a blood plate, and a selective
medium like cysteine-tellurite blood plate.
Identification: biochemical tests.
Toxigenicity test:
1. Tissue culture neutralization assay.
2. in vitro test: immunodiffusion assay (Elek test ).
3. Detection of toxin gene by PCR.
C. diphtheriae
Treatment
Treatment of diphtheria rests on prompt
administration of antibiotics (penicillin or
erythromycin) and diphtheria antitoxin.
Maintenance of an open airway.
Vaccination of recovered patients with
toxoid is required because most patients
fail to develop antitoxin antibodies.
C. diphtheriae
Prevention and Control
Humans are the only known reservoir of C. diphtheriae.
Diphtheria was mainly a disease of small children.
This organism is maintained in the oroparynx or skin of
asymptomatic carriers.
The bacteria are spread directly from person to person.
To limit contact with diphtheria bacilli to a minimum,
patients with diphtheria should be isolated.
Prophylactic antibiotic treatment to unimmunized contacts.
C. diphtheriae
Prevention and Control
Active immunization in childhood with diphtheria toxoid (fromalininactivated toxin) yields antitoxin levels adequate until adulthood.
All children must receive an initial course (2, 4, and 6 months) of
immunizations and boosters (18 months and 6 years).
Regular booster with Td (tetanus and diphtheria) toxoids are
particularly important for adults who travel to developing countries.
Vero cell neutralization test can be used to measure antitoxin
antibodies in serum.
Toxoids for delayed absorption: Fluid toxoid absorbed onto
aluminum hydroxide or aluminum phosphate. Usually combined
with tetanus toxoid and pertussis vaccine (DPT vaccine).
Other Corynebacterium Species
They are ubiquitous in plants and animals. Many are found as
part of human normal flora on the skin and mucosal surfaces,
and may cause opportunistic infections in hospitalized or
immunocompromised patients.
C. jeikeium and C. amycolatum: sepsis, endocarditis,
wound infections, foreign body infections, pneumonia, and
UT infections.
C. urealyticum causes UT infections. It is a strong urease
producer, infection of UT may lead to formation of stones.
Some strains of C. ulcerans and C. pseudotuberculosis
may produce diphtheria toxin and cause diphtheria.
Resistant to many antibiotics. Treatment of bacteremia or
endocarditis must be guided by antibiotic susceptibility tests.
Listeria and Erysipelothrix
L. monocytogenes: meningitis and bacteremia
E. rhusiopathiae: erysipeloid (a zoonotic disease)
Structure and Physiology of Listeria
Small gram-positive coccobacilli; facultative
anaerobe.
Motile at room temperature but less so at 37 oC.
b-hemolytic (weak)
Grow on most conventional media in a wide pH and
temperature range (1 oC to 45 oC).
L. monocytogenes
Pathogenesis and Immunity
Widely distributed in nature (soil, water, vegetation, and the
intestines of a variety of animals). Fecal carriage in healthy
people: 1%-5%.
Human disease is rare and is restricted to neonates and the
elderly, pregnant women, and immunocompromised patients
(particularly those with defective cell-mediated immunity, such
as AIDS patients).
Infection is initiated in the intestine.
Facultative intracellular pathogen. The intracellular survival and
spread of the bacteria are critically important in pathogenesis
and, therefore, cellular immunity is more important than humoral
immunity in host defense against this organism.
L. monocytogenes
Clinical Diseases
Neonates
Adults
Early onset disease (acquired
transplacentally in utero):
granulomatosis infantiseptica,
with disseminated abscesses
and granulomas in multiple
organs.
Infection in healthy adults:
asymptomatic or mild
influenza-like illness;
gastrointestinal symptoms in
some patients.
Late onset disease (acquired at
or soon after birth): meningitis or
meningoencephalitis with
septicemia, similar to that
caused by group B streptococci.
Meningitis; primary bacteremia
with chills and fever; high
fever and hypotension in
severe cases. Maybe fatal.
(High risk: organ transplant
patients, cancer patients,
pregnant women)
L. monocytogenes
Laboratory Diagnosis
Specimen: CSF and blood.
Gram stain: CSF typically show no Listeria because of the
low bacterial concentration.
Culture
Listeria grows on most conventional media.
Selective media and cold enrichment are used for
specimens contaminated with rapidly growing bacteria.
Hemolysis (CAMP-positive) and motility in liquid or
semisolid medium are useful for preliminary identification.
Identification
Biochemical and serological tests (13 serotypes).
L. monocytogenes
Treatment, Prevention, and Control
L. monocytogenes is resistant to multiple antibiotics (e.g.,
cephalosporin and tetracycline). Currently, gentamicin with
either penicillin or ampicillin is the treatment of choice.
Outbreaks have been associated with the consumption of
contaminated milk, soft cheese, undercooked meat, unwashed
raw vegetables, and cabbage. Refrigeration of contaminated
food products permits the slow multiplication of the organisms to
an infectious dose.
Because Listeria organisms are ubiquitous and most infections
are sporadic, prevention and control are difficult. High risk
people should avoid eating raw or partially cooked foods.
Erysipelothrix (Hair of red disease)
E. rhusiopathiae
Slender gram-positive, microaerophilic, with a tendency to form
filaments. Form small, grayish a-hemolytic colonies after 2 to 3 days
incubation.
Widely distributed in wild and domestic animals. Animal disease
(particularly in swine) is widely recognized, but human disease is
uncommon.
Causes zoonotic infections through an abrasion or wound:
Localized skin infection (erysipeloid): 1-4 day incubation; painful
and pruritic, slowly spreading inflammatory skin lesions on the
fingers or hands, violaceous with raised edge. Suppuration is
uncommon.
Diffuse cutaneous infection: rare and often associated with systemic
manifestation.
Septicemia: uncommon and frequently associated with endocarditis.
Erysipelothrix
Penicillin is the antibiotic of choice.
Specimen: full-thickness biopsy specimens or deep aspirates
(because the bacteria locate only on deep tissues).
Culture: grow on most conventional media in the presence of
5%-10% CO2.
Identification
Motility- and catalase-negative.
Biochemical tests.
People at occupational risk (butchers, meat processors, farmers,
poultry workers, fish handlers, and veterinarians) are prevented
by use of gloves and other coverings on exposed skin.
Vaccination is used to control disease in swine.
Bacillus
B. anthracis: anthrax of the animals and humans.
B. cereus: food poisoning; opportunistic infections.
Morphology and Physiology
Aerobic or facultatively anaerobic.
Large gram-positive rods, have
square ends, arranged in long
chains.
Spore is located in the center of
the cell.
Most are saprophytic (soil, water,
air, and on vegetation.)
B. anthracis
Physiology and Structure
B. anthracis is encapsulated and non-motile.
The capsule consists of polypeptide (poly-D-glutamic
acid) and is an important virulence factor.
The spores can withstand dry heat and certain
disinfectants for moderate periods, and persist for
years in dry earth. Animal products contaminated with
anthrax spores can be sterilized only by autoclaving.
B. anthracis
Pathogenesis and Immunity
Primarily a disease of herbivores (sheep, cattle, horses);
humans are rarely affected.
Being used by the terrorists as a biological warfare.
In animals, portal of entry is mouth and GI tract. In humans,
scratches in the skin (95% of infection), ingestion or inhalation
lead to infection. Inhalation is the most likely route for infection
with biological warfare (LD50: 2,500-55,000).
The spores germinate in the tissue at the site of entry, and
growth of the vegetative forms results in gelatinous edema and
congestion. Bacillus spread via lymphatics to the blood and
other tissues.
B. anthracis
Pathogenesis and Immunity
Virulence factors
Capsule (encoded from a plasmid)
Exotoxins (A-B toxins encoded from another plasmid)
Edema toxin is composed of protective antigen (B-subunit)
and edema factor (EF; an adenylate cyclase). This toxin
complex increases vascular permeability which leads to
shock.
Lethal toxin is composed of protective antigen and lethal
factor (LF; a metalloprotease). This toxin causes cell death
and stimulates macrophages to release proinflammatory
cytokines.
B. anthracis
Clinical Diseases
Cutaneous anthrax (malignant pustule): develops in 12-36
hours. The papule rapidly changes into a vesicle, then a
pustule, and finally a necrotic eschar. The infection may
disseminate, giving rise to septicemia.
Inhalation anthrax (wool-sorters’ disease): long incubation
time (2 months or more). Mediastinitis (enlargement of
mediastinal lymph nodes), sepsis, and meningitis (50%
patients). Pulmonary disease rarely develops.
Gastrointestinal anthrax (very rare): symptoms vary
depending on the sites of infection. Can result in ulcers in
the mouth and esophagus, or abdominal pain, vomiting and
bloody diarrhea. Both rapidly progress to septicemia with a
mortality that can be 100%.
B. anthracis
Laboratory Diagnosis
Specimens: fluid or pus from local lesion, blood, or sputum.
Smears: long chains (a characteristic of B. anthracis) of large
gram-positive rods without spores can be seen. Immunofluorescence stain can be used for dried smears.
Culture: nonhemolytic gray colonies with dry “ground glass”
surface on blood agar plates (“Medusa head” morphology:
irregular edges with projections).
Identification: made in a reference lab by direct fluorescent Ab
test against capsular polypeptide or PCR test.
Serological tests: detection of antibodies to lethal toxin and
edema toxin.
B. anthracis
Treatment
Sensitive to penicillin but resistant to sulfonamides and
cephalosporins. Combined antibiotic treatment is used for
penicillin- and doxycycline-resistant strains.
Control
Proper disposal of animal carcasses (burning or deep burial
in lime pit).
Autoclaving of animal products.
Protective clothing and gloves for handling infected animals.
Vaccination of domestic animals.
Immunization of persons at high risk with a cell-free vaccine
based on the protective antigen is under investigation.
B. cereus and other bacillus species
Ubiquitous organisms; primarily opportunistic pathogens.
B. cereus: the most important among them.
Noncapsulated and motile, causing
gastroenteritis: emetic form and diarrheal form.
ocular infections: acute panophthalmitis occurs after
traumatic, penetrating injuries of the eye with a soilcontaminated object. A variety of toxins are involved.
intravenous catheter-related sepsis.
Other infections: endocarditis, pneumonitis, sepsis,
meningitis, etc. in immunosuppressed patients.
Symptomatic treatment is adequate for B. cereus gastroenteritis.
The treatment of other Bacillus is complicated because the course
is rapid and progressive and they are resistant to multiple drugs.
Food poisoning can be prevented by quick consumption and proper
storage of food.
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B. cereus food poisoning
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Diphtheria toxin is an A-B toxin expressed from a
temperate phage (b-phage) in the presence of low iron
concentrations.
This toxin binds to a receptor (heparin-binding
epidermal growth factor) on the surface of many
eukaryotic cells, particularly heart and nerve cells, and
results in inhibition of polypeptide chain elongation by
ribosylation of the elongation factor EF-2.
It can induce protective antibodies (antitoxin).
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Bull-neck
appearance
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Internalins
Listeriolysin O
Phospholipase C
ActA
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Spores in the soil
Spores from
Germination of
the carcasses
spores in the soil
Grazing animals infected through
injured mucous membrane
Infection in humans
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