Last Minute Final Exam Quickie Review


Actinobacillus actinomycetemcomitans

Colonize human and animal oropharynx

Juvenile periodontitis or human bite wound infections with secondary endocarditis


Bacillus anthracis

Antiphagocytic polypeptide capsule

Three component exotoxin (protective antigen, edema factor, lethal factor)

Heat-resistant spore formation

Survive in soil and on vegetation for prolonged periods due to spore formation

Herbivores are natural hosts and humans accidental hosts

Human disease acquired by direct inoculation (95% of cases), inhalation (Woolsorter's disease), or ingestion of spores from contaminated soil or infected animal products


Bacillus cereus

Most common cause of traumatic eye injury with three toxins implicated (necrotic toxin, cereolysin, and phospholipase C)

Organisms inoculated into eye from soil contamination of the penetrating object or from endogenous flora colonizing the surface of the eye

Panopthalmitis rapidly progresses with complete loss of light perception within 48 hours with massive destruction of the vitreous and retinal tissues

Two forms of food poisoning mediated by heat stable enterotoxin (usually in improperly stored, cooked rice) causing vomiting (emetic form) or heat labile enterotoxin causing diarrhea.


Bordetella pertussis, Bordetella parapertussis

Very small, nonmotile, strictly aerobic, fastidious, gram-negative coccobacillus

Does not grow on common laboratory media without supplementing with nicotinamide and charcoal, starch, blood, or albumin to absorb toxic substances

Oxidizes amino acids, but does not ferment carbohydrates

Fimbriae present, but not primarily involved in adherence

Exotoxin and hemagglutinin mediate attachment

Virulence factors include: pertussis toxin (a.k.a., histamine sensitizing factor, lymphocytosis promoting factor, islet cell activating factor and pertussigen), adenylate cyclase toxin, tracheal cytotoxin, dermonecrotic toxin, filamentous hemagglutinin, LPS (lipid A and lipid X)

Disease is highly communicable (highly infectious), person-to-person spread via inhalation of infectious aerosols

Three distinct stages of disease: i) catarrhal, ii) paroxysmal, and iii) convalescent

Incidence in U.S.A. significantly reduced with required DPT vaccine


Bordetella brochiseptica

Bronchopulmonary disease


Borrelia burgdorferi

Lyme disease with white-footed deer mouse, rodents, deer, domestic pets, hard-shelled tick reservoirs and hard-shelled tick vector

Characterized by three stages:

i) Initially a unique skin lesion (erythema chronicum migrans (ECM)) with general malaise, lesions periodically reoccur

ii) Subsequent stage (in 5-15% of patients) have neurological or cardiac involvement

iii) Third stage involves migrating episodes of non-destructive, but painful arthritis


Borrelia recurrentis

Epidemic relapsing fever with human reservoir and body louse vector

Endemic relapsing fever with rodents and soft-shelled tick reservoris and soft-shelled tick vector

Following transmission by infected arthropods, these organisms are disseminated in the bloodstream and seeded intracellularly in multiple organs where they are able to undergo antigenic variation as a means of avoiding the host immune response and resulting in periodic febrile and afebrile episodes, with each subsequent relapse generally less severe and of shorter duration

Causes borreliosis infection also known as, relapsing fever, tick fever, borreliosis, famine fever

An acute infection characterized by a 2-14 day (usually 6 day) incubation period followed by recurring febrile episodes, constant spirochaetemia that worsens during febrile stages

Brucella spp.

Four species: Brucella abortus (cattle), Brucella suis (swine), Brucella melintensis (goats, sheep), Brucella canis (dogs)

Clinical disease associated with contact with infected cattle, cattle products, or dogs is a milder form than that associated with contact with goats and sheep (acute, severe, complications common) or swine (chronic, suppurative, destructive) with localization in cells of the reticuloendothelial system (RES)

500,000 human cases per year caused by this organism with worldwide distribution, but less than 100 annual cases in the U.S. due to successful control of the disease in livestock and the animal reservoir (cattle, goats, sheep, swine, buffalo, bison, dogs, foxes, coyotes) including identification and destruction of infected animals/herds and animal vaccination

Protective clothing for abattoir workers, avoidance of unpasteurized dairy products


Burkholderia cepacia

Like Pseudomonas aeruginosa, colonizes moist environmental surfaces and associated with nosocomial infections

Respiratory tract infections in immunocompromised patients, particularly those with cystic fibrosis

Urinary tract infections, septic arthritis, peritonitis, septicemia and other opportunisitic infections


Burkholderia pseudomallei

Saprophyte found in soil, water and vegetation and prevalent in Southeast Asia, India, Africa and Australia

Recognized as cause of melioidosis during Vitenam War when soil suspended in air by helicopter blades was inhaled by military personnel

Melioidosis occurs as:

i) acute suppurative infection

ii) chronic pulmonary disease or

iii) localized suppurative cutaneous infection with lymphadenitis, fever, malaise


Corynebacterium jeikeium, Stenotrophomonas maltophilia

Opportunistic infections in hospitalized patients, particularly highly immunocomromised patients receiving broad-spectrum antibiotics (e.g., hematological disorders, intravascular catheterization)

Opportunistic nosocomial infections include bacteremia/septicemia, soft tissue infections, pneumonia, meningitis, or urinary tract infections

Therapy complicated by resistance to multiple antibiotics


Clostridium botulinum

Production of neurotoxin (seven antigenically distinct types) specific for cholinergic nerves by blocking release of excitatory neurotransmitter, acetylcholine, with irreversible binding to specific receptors on the nerve endings resulting in flaccid paralysis

Clinical botulism syndromes classified as:

(i) classical or foodborne (following ingestion, a 1 to 2 day incubation period culminating in flaccid paralysis and death attributed to respiratory paralysis)

(ii) infant (with in vivo production of neurotoxin after consumption of spores)

or (iii) wound (4 days or more incubation period with in vivo production of neurotoxin following direct inoculation of spores or vegetative organisms)


Clostridium difficile

Antibiotic use results in disruption of normal gastrointestinal flora and allows for overgrowth of endogenous organisms or greater susceptibility to infection with exogenous strains

Resultant overgrowth of these toxigenic organisms can result in range of antibiotic-associated diseases from mild diarrhea to potentially fatal, pseudomembranous enterocolitis


Clostridium perfringens

Large, uniformly rectangular, nonmotile, anaerobic, gram-positive bacilli

Can produce ovoid subterminal spores, but spores are rarely observed in vivo or in fresh culture

Although nonmotile, rapid, spreading growth on culture media resembles that of motile organisms

Typical double zone of hemolysis, a beta-hemolytic zone surrounded by a larger zone of incomplete hemolysis

Lecithinase hydrolyzes phospholipids in egg yolk agar (Nagler reaction).

Rapid growth with production of four major lethal toxins (alpha toxin (lecithinase C), beta toxin, epsilon toxin, iota toxin), an enterotoxin, and minor toxins (delta, theta, kappa, lambda, mu, nu, neuraminidase), metabolically very active

Bacteremia, histotoxicity with myonecrosis (gas gangrene), cellulitis, fasciitis, soft tissue infections, food poisoning (8 to 24 hour incubation period), or enteritis necroticans


Clostridium tetani

Small, motile, anaerobic, spore-forming bacilli

Gram-positive in young culture, but may stain gram-negative in older cultures or in smears from wounds

Round, terminal spore giving vegetative cell a "drumstick" or "tennis racket" appearance


Francisella tularensis

Extremely small, nonmotile, fastidious, slow-growing (2-3 days) gram-negative coccobacillus

Thin, lipid capsule present in pathogenic strains

Two biochemical varieties:

F. tularensis bv. tularensis (Jeliison A; nearctica) more common type in North America with rabbit and tick reservoirs and tick vectors that cause a severe form of tularensis

F. tularensis bv. palaearctica (Jellison B) with rodent reservoirs and transimission by contact with contaminated water that causes a mild form of tularensis


Haemophilus ducreyi

Genital ulcers (chancroid) are most commonly diagnosed in males (perhaps due to asymptomatic carriage in females) appearing 5 to 7 days after exposure

The lesion progresses to a painful ulcer with inguinal lymphadenopathy

Syphilis and herpes simplex disease must be excluded prior to diagnosis


Haemophilus influenzae

Small, sometimes pleomorphic, gram-negative bacilli with many strains of this species, but not all, covered with a polysaccharide capsule comprising six antigenic serotypes ("a" through "f")

Type b antigen associated with the highest level of virulence

In vitro growth requires supplementation of media with growth factors hematin (X-factor) and NAD or NADP (V-factor)

Obligate parasites on mucus membranes of humans and animal species

Prior to introduction of successful pediatric immunization program, most common cause of acute bacterial meningitis in infants and young children, as well as, other serious pediatric diseases, e.g., epiglottitis, cellulitis, as well as, chronic pulmonary disease in adults

Primary risk factor for invasive disease is the absence of protective antibody against the polysaccharide capsule

Grown on chocolate agar; blood is heated to inactivate inhibitors and to release factors from red blood cells required for growth of organisms

Requirement for heat-labile V-factor (NAD, NADP coenzymes) and heat-stable X-factor (precursor of hemin)


Leptospira interrogans

Icteric (jaundice) and anicteric (no jaundice) forms of leptospirosis

Causes mild flu-like febrile illness or severe systemic disease also called Weil's disease (icteric form)

Weil's disease characterized by acute febrile jaundice and nephritis with renal and hepatic failure due to damage to the endothelium of small blood vessels with shedding of the abundant organisms in the urine

Transmitted to humans from a variety of animal hosts (both wild and domestic mammals, e.g., dogs in the U.S.)


Mycobacterium avium-intracellulare complex (MAC)

Overwhelming disseminated infections in immunocompromised patients

Particularly common in AIDS patients in the terminal stages of their disease as CD4 lymphocyte levels wane

May be referred to as atypical tuberculosis


Mycobacterium bovis

Formerly important cause of bovine tuberculosis transmitted by ingestion of contaminated milk

Uncommon in the United States, since the advent of pasteurization and herd surveillance

Important as species from which attenuated strain (Bacillus of Calmette and Guerin (BCG)) is used for preparation of tuberculosis BCG vaccine


Mycobacterium leprae

Range of clinical presentation is dependent on patient's immune response

At one end of the spectrum (tuberculoid leprosy), patients have a strong delayed hypersensitivity reaction and weak humoral antibody response with infected foci characterized by large numbers of lymphocytes and granulomas and relatively few bacilli in the tissues due to cytokine-mediated macrophage activation

At the other end of the spectrum (lepromatous leprosy), patients have a strong antibody response, but a specific defect in their cellular response with large numbers of organisms in dermal macrophages and Schwann cells of the peripheral nerves

Differences in clinical and immunological manifestations (type and number of skin lesions, histopathology, infectivity, and immune response including delayed hypersensitivity, immunoglobulin levels, and presence or absence of erythema nodosum leprosum) are used to identify the form of this disease that is diagnosed on a continuum from one end of the range to the other


Mycobacterium tuberculosis

Nonmotile, aerobic, fastidious, very slow-growing (12-30 days), acid-fast bacilli with a complex cell wall rich in lipids

Surface glycolipids include waxes, mycosides and cord factor (mycolic acids), the latter, responsible for the parallel arrangement of rows of bacilli in virulent strains ("cord formation")

Surface protein (15% of cell wall weight) stimulates host cell mediated immunity and is purified and used as a reagent to evaluate hypersensitivity in a skin test (PPD, purified protein derivative)

An estimated 1.7 billion people are infected worldwide and 10 million in the U.S.

Humans are the only natural reservoir with transmission via inhalation of infectious aerosols associated with close person-to-person contact

Spread to health care workers and the rise in antibiotic resistant and multiple-resistance strains pose particular public health hazards

Primary pulmonary infection with secondary infection of pulmonary or extra-pulmonary sites with host cellular immunity resulting in tissue destruction and fibrosis (fibrous walling off of lesions, i.e. granulomatous reaction), caseation, calcification, and ultimately cavitation caused by host response to infection (viewed by chest X-ray)

Microscopic detection of acid-fast bacilli in clinical specimens (particularly early morning sputum respiratory secretions) can be accomplished by carbol fuchsin stain (e.g., Kinyoun or Ziehl-Nielsen), fluorescent auramine-rhodamine dyes (Truant fluorochrome), followed by decolorization in an acid-alcohol solution, and counter staining


Neisseria gonorrhoeae

Capacity to invade intact mucus membranes or skin with abrasions

Most common sites of inoculation are the vagina or cervix in the female and the penis in the male

Only piliated cells (formerly, colony types T1 and T2) are virulent by attaching to intact mucus membranes, penetrating into and passing through mucosal cells, and establishing infection in the sub-epithelial layer

Seriously underreported, sexually transmitted disease found only in humans with strikingly different epidemiological presentations for females and males

Major reservoir is asymptomatic carriage in females

Microscopy reveals encapsulated, small, gram-negative diplococci inside polymorphonuclear leukocytes (PMN's) in urethral purulent discharge

Penicillin is no longer the drug of choice because MIC has steadily increased, and plasmid-mediated enzymatic hydrolysis and chromosomally-mediated resistance has risen to >10% of all strains

Ceftriazxone, cefixime, or a fluoroquinolone for uncomplicated cases and in combination with doxycycline or azithromycin for dual infections with other STD's


Neisseria meningitidis

Pili-mediated, receptor-specific colonization of nonciliated cells of nasopharynx

Antiphagocytic polysaccharide capsule allows systemic spread

Toxic effects mediated by hyperproduction of lipooligosaccharide (LOS) lacking O-side chain

Meningitis, meningococcemia, pneumonia, arthritis, urethritis following dissemination of virulent organisms from the nasopharynx

Large numbers (>10e7 organisms/ml) of encapsulated, small, gram-negative diplococci in the presence of polymorphonuclear leukocytes (PMN's) in cerebrospinal fluid (CSF)

Serogroups A, B, C, Y, W135

Transparent, non-pigmented, oxidase-positive, nonhemolytic colonies on chocolate blood agar with enhanced growth in moist atmosphere with 5% CO2

Although patients with systemic disease generally are bacteremic, commercial blood culture bottles contain toxic additives that may inhibit growth

Differentiated from other species in the genus by acid production from glucose and maltose, but not sucrose or lactose


Pasteurella multocida

Natural reservoir is upper respiratory tract of domestic animals (e.g., dogs, cats) with humans acquiring the infection with an animal bite or scratch

Subsequent suturing of the wound can exacerbate the infection, allowing for a reduction in the pO2 and growth of the facultative anaerobe.

Clinical infection occurs either as:

i) cellulitis and lymphadenitis with pain and swelling from bites or scratches

ii) septicemia with systemic infection in immunocompromised patients or

iii) further pulmonary complications in patients with chronic respiratory disease


Pseudomonas aeruginosa

Virulence factors include: pili, polysaccharide capsule, endotoxin, exotoxin A, exoenzyme S, elastase, alkaline protease, phospholipase C, leukocidin

Ubiquitous, opportunistic pathogens that occupy a variety of moist environmental habitats with minimal nutritional requirements, an ability to tolerate a wide range of temperatures (4oC to 42oC), and resistance to most antibiotics and disinfectants

Found throughout hospitals in moist reservoirs

Immunocompromised patients, burn patients, IV drug abusers at highest risk

Burn wound infections, bacteremia, endocarditis, pulmonary infections, complication of cystic fibrosis, ear infections, urinary tract infections, gastroenteritis, eye infections, musculoskeletal infections


Stenotrophomonas maltophilia, Corynebacterium jeikeium

Opportunistic infections in hospitalized patients, particularly highly immunocomromised patients receiving broad-spectrum antibiotics (e.g., hematological disorders, intravascular catheterization)

Opportunistic nosocomial infections include bacteremia/septicemia, soft tissue infections, pneumonia, meningitis, or urinary tract infections

Therapy complicated by resistance to multiple antibiotics


Treponema pallidum ssp. pallidum

Very thin, very long, helically-coiled (spiral), motile, gram-negative "spirochetal" bacillus

Strict human pathogen (although, experimental disease has been established in a rabbit testes model) that cannot be grown in cell-free culture

Periplasmic flagella (axial fibrils) outside of protoplasmic core and surrounded by an outer envelope or sheath that are anchored at either end of the cell by insertion pores

Too thin to be able to be seen by light microscopy, so darkfield microscopy or fluorescent antibody staining are required

Once considered strict anaerobes, but are now known to be able to oxidatively metabolize glucose

Outer membrane proteins associated with adherence

Hyaluronidase facilitates perivascular infiltration (the hallmark presentation lesions at all stages of this disease, e.g., endarteritis and periarteritis)

Virulent strains capable of coating the bacterial cell with host cell fibronectin and effectively "masking" themselves

Organisms frequently survive following ingestion by phagocytic cells

Primary disease process involves invasion of mucus membranes, rapid multiplication, wide dissemination through perivascular lymphatics and systemic circulation occur prior to development of the primary lesion

10-90 days (usually 3-4 weeks) after initial contact the host mounts an inflammatory response at the site of inoculation resulting in the hallmark lesion, called the chancre (changes from hard to ulcerative), with profuse shedding of spirochetes; swelling of capillary walls and regional lymph nodes with draining; primary lesion is resolved by fibrotic walling-off

Primary stage followed by secondary, latent and tertiary syphillis (see Treponema)

Transmitted by direct sexual contact

STD has long incubation period during which time host is non-infectious

Useful epidemiologically for contact tracing and administration of preventative therapy

Prostitution for drugs or for money to purchase drugs remains central epidemiologic aspect of transmission


Treponema pallidum ssp. endemicum; ssp. pertenue; T. carateum

Acquisition of nonvenereal treponemal diseases is by contact with contaminated eating utensils (bejel), or by direct contact with infectious lesions (yaws, pinta)


Yersinia enterocolitica

Common cause of enterocolitis in Scandinavian and colder areas of North America

Some studies show increased incidence during colder months which leads to the speculation that this organism may be more clinically active in cold climates, a hypothesis that parallels the observed increased metabolic activity at 22oC to 25oC

Epidemic outbreaks have been associated with contaminated meat or milk

In 1987, blood-transfusion related bacteremia and endotoxic shock was reported with organisms apparently able to survive and grow in nutritionally rich blood products that are stored by prolonged refrigeration


Yersinia pestis

Two epidemiological cycles of plague:

Sylvatic cycle with wild rodent reservoirs (e.g., prairie dogs, rock squirrels) and wild rodent flea vectors

Urban or domestic cycle with domestic rat reservoir and Oriental rat flea vector

Two clinical forms of epidemic plague:

Bubonic plague with characteristic lymph node (buboes) swelling which may progress to secondary pneumonic plague

Primary pneumonic plague is spread by infectious respiratory aerosols and is highly contagious



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