LECTURE Flashcards
are those that catabolize carbohydrates anaerobically in which inorganic ions other than oxygen can serve as the final electron acceptor, or by both aerobic and anaerobic pathways.
Fermentative organisms (fermenters)
are those that do NOT ferment carbohydrates
Nonfermentative organisms (nonfermenters)
use carbohydrates aerobically to derive energy for their metabolism
oxidizers
do not break down carbohydrates at all
nonoxidizers or asaccharolytic.
are ubiquitous and found in moist environments, typically in soil and water, on plants and decaying vegetation, and in many foodstuffs
nonfermentative gram-negative bacilli (NFGNB )
isolated from nebulizers, dialysate fluids, saline, catheters, and other devices
nonfermentative gram-negative bacilli (NFGNB )
rarely, if ever, part of the normal host microbiota but can easily colonize hospitalized patients, especially those who are immunocompromised; have become clinically significant because of the increasing numbers of immunocompromised patients
nonfermentative gram-negative bacilli (NFGNB )
account for about 15% of all gram-negative bacilli isolated from clinical specimens
nonfermenters
Four groups of nonfermenters make up most isolates routinely seen in clinical laboratories:
Pseudomonas aeruginosa, Burkholderia spp., Acinetobacter spp., and Stenotrophomonas maltophilia.
accounts for the largest percentage of all nonfermenters isolated from clinical specimens.
Pseudomonas
The pseudomonads have been classified based on
rRNA/DNA homology and common culture characteristics.
It is now known that each of the five rRNA groups represents taxonomically distinct genetic groups, and as a result different genus names have been assigned to each of the [?].
rRNA groups
Only the members of [?] retain the genus designation of Pseudomonas.
rRNA group I
produce pyoverdin
P. aeruginosa, P. fluorescens, P. putida
occurs widely in soil, water, plants, and animals, and grows to very high numbers in moist environments.
P. aeruginosa
• It is an uncommon part of the normal flora of the colon in about 10% of humans, and gets in on the skin from fecal organisms
P. aeruginosa
• Sources of infections include:
- contaminated catheters, humidifiers, ventilators, intravenous solutions, anesthesia and resuscitation equipment in hospitals;
- raw vegetables, and cut and potted flowers;
- in sink drains, and if not properly maintained, in pools, and hot tubs
P. aeruginosa
• P. aeruginosa is primarily an
opportunist
P. aeruginosa is unlikely to cause infections in healthy people with
intact anatomical barriers.
Severe infections occur in people with [?] (e.g., when mucous membranes and skin are disrupted by direct tissue damage as in the case of burn wounds; or when neutropenia is present, as in cancer chemotherapy)
weakened host defenses
P. aeruginosa is primarily a [?] (accounting for 5% to 15% of all hospital-acquired infections) causing infections after invasive medical procedures (e.g., when intravenous or urinary catheters are used).
nosocomial pathogen
P. aeruginosa is notorious for its resistance to many [?] therefore becomes dominant and important when more susceptible bacteria of the normal flora are suppressed.
antimicrobial agents
Is the third most common cause of gram-negative bacillary bacteremia, after E. coli and Klebsiella pneumoniae
Bacteremia/ septicemia
Poor prognostic factors associated with P. aeruginosa
bacteremia include septic shock, granulocytopenia,
inappropriate antimicrobial therapy, and the presence of septic metastatic lesions.
Bacteremia/ septicemia
can give rise to grave conditions such as endocarditis, meningitis, and bronchopneumonia.
Pseudomonas septicemia
are cutaneous papules which progress to black, necrotic ulcers that are surrounded by erythema and often do not contain pus. This result from direct invasion and destruction of blood vessel walls by the P.aeruginosa and is uncommon in bacteremia caused by organisms other than P. aeruginosa.
Ecthyma gangrenosum
P. aeruginosa is the leading cause of nosocomial respiratory infections
Pneumonia/ventilator-associated pneumonia
Respiratory tract infections are often linked with contaminated respirators and results in necrotizing pneumonia.
Pneumonia
Since P. aeruginosa can colonize mucosal surfaces, such as the oropharynx, patients in the intensive care unit (ICU) who are mechanically ventilated may quickly become colonized.
Pneumonia
P.aeruginosa is a major threat to hospitalized patients with
cystic fibrosis
an inherited defect in chloride ion transport that causes severe damage to the lungs, digestive system and other organs of the body. It affects the cells that produce mucus, digestive juices, and sweat. The
defective gene responsible for CF leads to the creation of thicker and stickier mucus than is usual. The colonization of the bronchi then becomes
a biofilm with microcolonies of bacteria and debris imbedded in the alginate. Instead of acting as a lubricant, the secretions plug up the ducts and passageways leading to severe lung infections
Cystic Fibrosis (CF)
For P. aeruginosa, the selective advantages of the biofilm include [?] (complement, antibody, phagocytes)
and [?].
inaccessibility of the immune system
antimicrobial agents
resulting to exudation of “blue-green pus (associated to pyocyanin production) with a “grapelike odor”.
Infection of wounds and burns
detected in infected wounds, or burns by ultraviolet fluorescence
pyoverdin
occurs when P. aeruginosa is introduced by contaminated catheters and instruments or in irrigating solutions.
Urinary tract infection
results when the organism is introduced by lumbar puncture or during a neurosurgical procedure through contaminated instrumentation
Meningitis
an inflammation of the external ear canal, is
often found in a less severe form (mild otitis external) in swimmers (“swimmer’s ear”) and in invasive form (malignant otitis externa) in patients with diabetes
Otitis externa
occurs most commonly after injury or surgical procedures that can be fulminant and threaten permanent loss of vision
Eye infections
P. aeruginosa attaches to and colonizes the mucous membranes or skin, invades locally, and produces
systemic disease
Capsular polysaccharide that allows infecting bacteria to adhere to lung epithelial cell surfaces and form biofilms which, in turn, protect the bacteria from antibiotics and the body’s immune system.
Alginate
Surface appendages that allow adherence of organism to GM-1 ganglioside receptors on host epithelial cell surfaces
Pili
Removes the sialic acid residues from GM-1 ganglioside receptors on host epithelial cells, facilitating binding of pili
Neuraminidase
Responsible for many of the endotoxic properties of the organism that plays a direct role in causing fever, shock, oliguria, leukocytosis and leukopenia, disseminated intravascular coagulation, and adult respiratory distress syndrome
Lipopolysaccharide
Inhibits protein synthesis and causes tissue necrosis by a mechanism of action identical to that of diphtheria toxin, although the structures of the two toxins are not identical
Exotoxin A (ExoA)
Interrupts normal gastrointestinal activity, resulting to
diarrhea
Enterotoxin
- Inhibits protein synthesis
Exoenzyme S (ExoS)
- Entry into the cytoplasm of the host cell is facilitated by a Type III secretion system of the organism
Exoenzyme S (ExoS)
A heat-labile hemolysin that degrades lipids thereby
destroying the host cell cytoplasmic membrane; which
favors spread of the organism to contiguous tissues
Phospholipase C
Destroys pulmonary surfactant and inactivates opsonins
Phospholipase C
Cleaves immunoglobulins and complement components, and disrupts neutrophil activity
Elastase
Degrades proteins that allow the organism to acquire nutrients from the host and disseminate from the local site
Elastase
Inhibits neutrophil and lymphocyte function
Leukocidin
Suppress other bacteria and disrupt respiratory ciliary activity
Pyocyanins
Cause oxidative damage to tissues, particularly oxygenated tissues such as that of the lungs
Pyocyanins
P. aeruginosa binds and secretes the [?], which acts on protein synthesis by the same mechanism as diphtheria toxin
Exotoxin A (ExoA)
a type III injection secretion system delivers [?] to the cell cytoplasm.
Exoenzyme S (ExoS)
is secreted extracellularly. All toxins act to destroy the cell and the bacteria may enter the blood.
Elastase
Since most common nosocomial Pseudomonas infection occur in compromised hosts, scrupulous attention to [?], especially among health care workers, is necessary to prevent infections caused by this ubiquitous pathogen.
disinfection and hand washing
Because pseudomonas thrives in [?], special attention should be paid to sinks, water baths, showers, hot tubs, and other wet areas.
moist environments
Vaccines incorporating [?] from multiple P. aeruginosa serotypes have been developed and proved immunogenic in humans. The primary candidates for such preparations are [?]. Although some protection has been demonstrated, these preparations are still experimental.
somatic antigens
patients with burn injuries, CF, or immunosuppression
These include other gram-negative bacilli that are either asaccharolytic or oxidative in their metabolism.
Other Nonfermentative Gram-Negative Bacilli (NFGNB)
includes species that were formerly placed in the genus Pseudomonas.
Genus Burkholderia
is an obligate parasite of animals (primarily horses, mules, and donkeys) causing a respiratory tract infection known as glanders or farcy
B. mallei
manifests with prominent pulmonary involvement, subcutaneous ulcerative lesions, and lymphatic thickening with nodules; systemic disease also occurs.
Glanders in horses
Human disease is extremely rare; from an animal source, it can be transmitted to humans either by entry of the organism through an abrasion or break on the skin, or by inhalation of the organisms.
B. mallei
Human infections can be fatal which usually begins as an ulcer of the skin or mucous membranes followed by lymphangitis and sepsis. Inhalation of the organisms may lead to primary pneumonia.
B. mallei
is an environmental organism found in soil, streams, surface water, such as rice paddies.
B. pseudomallei
It causes infection in sheep, goats, swine, horses, and other animals, although animals do not appear to be a primary reservoir for the organism.
B. pseudomallei
Human infections can occur by inhalation of dust, ingestion of contaminated water, and contact with contaminated materials (e.g., soil).
B. pseudomallei
a disease that is clinically and pathologically similar to glanders
melioidosis
It is endemic in areas with tropical climates such as that of Southeast Asia (including Vietnam and Thailand), northern Australia, and Mexico.
B. pseudomallei
Incubation period is not clearly defined but may range from 2 days to many years.
B. pseudomallei
An important feature is its ability to produce latent infection that can reactivate many years after primary exposure.
B. pseudomallei
most common form of melioidosis; primary pneumonitis
pulmonary infection
clinical manifestations of melioidosis
(a) acute, localized infection
(b) acute bloodstream infection
(c. ) chronic suppurative infection involving various organs of the body
are considered potential agents for biologic warfare and biologic terrorism
B. pseudomallei and B. mallei
has been dubbed as “Vietnamese time bomb” as American veterans who aided in the Vietnam conflict has acquired the disease but may still be incubating at the time of their return in their homeland. Symptoms only became apparent several days up to years.
Melioidosis
consists of the prototypic species Burkholderia cepacia plus at least 18 other genomospecies which have been isolated in humans
B. cepacia complex
an environmental organism able to grow in water, soil, plants, animals, and decaying vegetable materials
B. cepacia complex
Human transmission is by exposure of medical
devices and solutions contaminated from the environment
B. cepacia complex
People with [?] and those patients with [?] are particularly vulnerable to infection with bacteria in B. cepacia complex.
cystic fibrosis (CF)
chronic granulomatous disease
They may have asymptomatic carriage, progressive deterioration over a period of months, or rapidly progressive deterioration with necrotizing pneumonia and bacteremia.
B. cepacia complex
It is likely that B. cepacia can be transmitted from one CF patient to another by
close contact
members have been reported to cause endocarditis (specifically in intravenous drug abusers), pneumonitis, UTIs, osteomyelitis, dermatitis, and other wound infections resulting from the use of
contaminated water
B. cepacia complex
are opportunists, and they are second to P. aeruginosa in frequency of isolation of all nonfermenters in the clinical microbiology laboratory.
Acinetobacter species
is the species most commonly isolated in the • Genus Acinetobacter
A. baumannii
They are widely distributed in soil and water and can occasionally on the skin and mucous membranes (.e.g, pharynx) of healthy people.
Acinetobacter species
They are widely distributed in soil and water and can occasionally on the skin and mucous membranes (.e.g, pharynx) of healthy people.
Acinetobacter species
In the hospital environment, they have been associated with ventilators, humidifiers, catheters, and other devices
Acinetobacter species
Transmission in health care settings is usually aided by instrumentation.
Acinetobacter species
Infections primarily affect patients with weakened immune systems and coexisting diseases. These infections usually occur in areas with a high fluid content such as the urinary tract and respiratory tract, and in peritoneal fluids.
Acinetobacter species
Diseases with which they have been associated include UTIs; pneumonia, tracheobronchitis, or both; endocarditis; septicemia; meningitis, often as a complication chemotherapy; and cellulitis, usually as a result of contaminated indwelling catheters, trauma, burns, or introduction of a foreign body.
Acinetobacter species
They can be isolated from blood, sputum, skin, pleural fluid, and urine.
Acinetobacter species
Acinetobacter species are usually [?] in appearance.
coccobacillary or coccal
Acinetobacter species resemble [?] on smears, because diplococcal forms predominate in body fluids and on solid media.
neisseriae
also occur, and occasionally the bacteria may appear to be gram-positive as they can resist decolonization and retain the crystal violet stain, leading to misidentification.
Rod-shaped forms
is the third most common nonfermentative, gram negative bacillus isolated in the clinical laboratory.
S. maltophila
Before 1983, S. maltophila was a member of the genus Pseudomonas; it was later reclassified as a member of the plant pathogen genus [?].
After DNA homology and sequencing analysis, it was classified as a member of the genus [?], where it remains today.
Xanthomonas
Stenotrophomonas
is ubiquitous in the environment, being found in water, sewage, and plant materials.
S. maltophilia
It is a significant nosocomial pathogen; it is very common in the hospital environment, where they can be found contaminating blooddrawing equipment, disinfectants, transducers, and other equipment.
S. maltophilia
Risk factors for colonization or infection with this organism are mechanical ventilation, use of broad spectrum antibiotics, catheterization, and neutropenia.
S. maltophilia
Diseases attributed to this organism includes endocarditis, especially in a setting of prior intravenous drug abuse or heart surgery; wound infections, including cellulitis and ecthyma gangrenosum; bacteremia; and, rarely, meningitis, cholangitis, and UTIs.
S. maltophilia
BAM: No distinctive appearance.
MAC: NLF
Burkholderia mallei
BAM: Smooth and slightly raised; dirt-like odor.
MAC: NLF; colonies become dark pink to red because of oxidation of lactose after 4-7 days. Burkholderia cepacia selective agar (BCSA), Pseudomonas cepacia (PC) agar, or oxidativefermentative base-polymyxin Bbacitracin-lactose (OFPBL) agar: Smooth.
Burkholderia cepacia complex
BAM: Smooth, opaque, raised, creamy, and smaller than Enterobacteriaceae; some genospecies are beta-hemolytic.
MAC: NLF, but colonies exhibit a purplish hue that may cause the organism to be mistaken for LF.
Acinetobacter baumannii
Acinetobacter lwoffi
BAM: Large, smooth, glistening colonies with uneven edges and lavender-green to light purple pigment; greenish discoloration underneath growth; ammonia smell.
MAC: NLF
Stenotrophomonas maltophila
Acid production (yellow) is seen only in the open tube, indicating that the organism is capable of oxidizing glucose but incapable of fermenting glucose.
OXIDATIVE UTILIZATION OF GLUCOSE by: Pseudomonas species, Burkholderia species, A. baumannii, or S. maltophila.
does not produce acids from glucose either fermentatively or oxidatively
Acinetobacter lwoffi
