zChapter 12 Clinical Bacteriology

S. aureus
skin, subcutaneous infections, bacteremia,endocarditis, toxic shock, food poisoning

catalase +, facultative anaerobes

S. epidermidis
opportunistic, nosocomial infections
normal skin flora and an opportunist that causes endocarditis of artificial heart valves

catalase +, facultative anaerobes

Streptococcus pyogenes
?-hemolytic
Streptococcus agalactiae
Group B
Beta hemolytic
Normal flora of GI urogenital tracts
Infection acquired in utero at birth
Neonatal bacteremia, pneumonia, meningitis
Streptococcus pneumoniae
Alpha hemolytic
Lancet shaped in pairs
Inhabitant of oropharynx
Antiphagocytic capsule
Diseases
Otitis media
Sinusitis
Pneumonia
Meningitis
Enterococcus species
?-hemolyti
Viridans streptococci
Normal oral flora
Several species
Disease
Endocarditis
During dental work, they can gain entrance to the blood and have a predilection for heart valves causing endocarditis. This is why a dentist often prescribes antibiotics for those undergoing extensive dental work
Enterococcus faecalis
Normal large bowel flora
Opportunists
Urinary and biliary tract infections
Neisseria gonorrhoeae
“gonococcus’
Gonorrhoeae
Sexually transmitted disease
Neonatal conjunctivitis
Associated with chlamydial infection
Pili promote adherence
Neisseria meningitidis
Colonizes nasopharynx
Meningitis
Aerosol droplet transmission
Antiphagocytic capsules
Carriers
Waterhouse-Friderichsen syndrome
Bacillus anthracis-
Gram positive bacilli
Spore formers
Ubiquitous- soil, water
Exotoxin producers
anthrax
Bacillus cereus
Gram positive bacilli
Spore formers
Ubiquitous- soil, water
Exotoxin producers
poisoning
Listeria monocytogenes
Gram positive coccobacillus
Normal animal GI flora
Transmission via contaminated food and dairy products
Intracellular growth with cell to cell transfer
Septicemia and meningitis
Granulomatosis infantiseptica
Corynebacteria diphtheriae
Gram positive, small club shaped bacillus
Oral cavity /throat infection
Exotoxin inhibits protein synthesis
Phage carries toxin gene
Diphtheroids normal throat inhabitants
Diphtheria
Aerosol droplet transmission
Vaccine
Antitoxin
Clostridium tetani
causes tetanus or lockjaw. It is the “step on a rusty nail” bacteria that vegetates in the host and produces a tetanospasm exotoxin that interferes with the nervous system leading to skeletal muscle contraction and eventual death by respiratory failure. Immunization with the toxoid is extremely effective, DPT. Antitoxin can be effective if administered before the toxin attaches to its receptors, but is usually too late.

Gram positive bacilli
Anaerobic
Spore forming
Exotoxin producing
Ubiquitous
Four medically important species

Clostridium botulinum
the cause of food poisoning with one of the deadliest toxins known. The exotoxin blocks release of acetycholine leading to flaccid paralysis. Spores in foodstuffs germinate under anaerobic conditions producing the toxin. Preformed toxin is often the cause of disease in home canned foods. Contaminated honey eaten by infants allows the organisms to grow in the GI tract but is a milder disease

Gram positive bacilli
Anaerobic
Spore forming
Exotoxin producing
Ubiquitous
Four medically important species

Clostridium perfringens
responsible for gas gangrene often seen in wounds. It is not only found in soil , but is a normal flora of the intestinal tract and can invade wounds contaminated with soil or human waste. It produces many virulence factors of which alpha toxin is very important in causing lysis of host cells. Gas production by the organism results in the bubbly formations of infected tissue. Antitoxin and antibiotics along with debridement of infected tissue are treatment.

Gram positive bacilli
Anaerobic
Spore forming
Exotoxin producing
Ubiquitous
Four medically important species

Clostridium difficile
part of the normal intestinal flora that acts as an opportunist when antibiotics kill off other normal flora allowing it to proliferate. It is frequently a nosocomial infection but is becoming more common in the general population. It produces an enterotoxin that causes diarrhea and destroys intestinal lining thereby producing a pseudomembranous colitis. Laboratory diagnosis requires the toxin to be identified since the organisms are normal flora.
Gram positive bacilli
Anaerobic
Spore forming
Exotoxin producing
Ubiquitous
Four medically important species
Escherichia coli
Gram negative bacilli
Normal flora of large intestine
Ubiquitous, soil, vegetation, water
LPS important endotoxin
Transmission- self inoculation, person to person, food, water
Become pathogenic via transfer of DNA
Antigenic classification
Diseases

Many strains categorized by pathology
Strains have acronym names
Pathology followed by E coli is sequence for names
EHEC
ETEC
EPEC, EIEC, EAEC

S dysenteriae
produces the most severe disease of the 4 species through Shiga toxin which inhibits protein synthesis, and is often epidemic in developing countries. Shigellosis or bacillary dysentery is the disease and entails profuse watery diarrhea, cramping, mucous and blood in stools and tenesmus. Shigella inject toxins directly into adjacent host cells using the type III secretion system
S sonnei
the species found most in the U S and is a milder form of the disease. Only a few hundred Shigella need to be swallowed to cause disease compared to other bacteria where thousands are necessary. This means Shigella can survive the acidic pH of the stomach. Dysentery: inflamed intestine, especially, colon with abdominal pain, tenesmus, frequent stools containing blood & mucous.
Salmonella typhimurium
the most common species. They cause nausea, vomiting, cramping and non-bloody diarrhea

Gram negative bacilli
Normal animal intestinal flora
Not normal human flora
Many serotypes based on surface antigens
Transmission via food and water
GI disease
Carriers

Salmonella enteritidis
the most common species. They cause nausea, vomiting, cramping and non-bloody diarrhea

Gram negative bacilli
Normal animal intestinal flora
Not normal human flora
Many serotypes based on surface antigens
Transmission via food and water
GI disease
Carriers

Salmonella typhi
invades colonic cells and is transported in macrophages to other parts of the body since it resists killing by the phagocytes. When this occurs, there is fever and inflammation of the infected organs and then the bacteria are returned to the intestine and cause GI disease. This scenario is termed typhoid fever. After recovery, in a small percentage of cases, the bacteria can remain in the gall bladder and be shed in the stool. This is the carrier state.

Gram negative bacilli
Normal animal intestinal flora
Not normal human flora
Many serotypes based on surface antigens
Transmission via food and water
GI disease
Carriers

Yersinia enterocolitica
Carried in livestock and wild animals
Transmission-food, water, blood
Bloody diarrhea long lasting
Yersinia pestis
Bubonic plague bacillus
Transmission-fleas and aerosol droplets
75% mortality rate
Haemophilus influenzae
without capsules are normal flora of the upper respiratory tract. The capsule, when present, is a critical virulence factor along with LPS. Organisms are transmitted via aerosol, invade the upper respiratory tract mucous membranes, enter the blood and then the CNS. There are 6 antigenic capsular types, a through f. Type b (Hib) is the most virulent and was a major cause of meningitis in infants until the current vaccine began to be used. An initial vaccine was made to react with the polysaccharide capsule of the organism, but didn’t work very well. Can you remember why this would be so? The current vaccine is conjugated to diphtheria toxoid (protein) and provides good immunity. Hib meningitis is still a significant disease in developing countrie
Infant meningitis
Erroneous blame for great pandemic of 1918
Haemophilus ducreyi
causes chancroid, a sexually transmitted disease that resembles syphilis in males but is often asymptomatic in females.
Legionella pneumophila
Gram negative coccobacilli, stains poorly
Facultative intracellular
American Legion outbreak, 1976
Atypical pneumonia
Pontiac fever
Inhibit phagolysosome fusion in phagocytes
Transmission aerosol from water sources
Bordetella pertussis
Small Gram negative, encapsulated ,coccobacilli
Whooping cough
Transmission- aerosol, person to person
Filamentous hemagglutinin
Exotoxins destroy ciliated epithelium of trachea
Vaccine (DPT) protection
Pasteurella multocida
Bites, scratches from dogs, cats
Cellulitis
Brucella animal disease, 4 species
Transmission to humans via skin GI or respiratory tracts
Undulant fever
Francisella tularensis
Capsule, intracellular growth
Very high infectivity
Tick bites and direct contact with ex rabbit, inhalation, ingestion
Bartonella henselae
causes cat scratch fever which consists of fever, abdominal pain and lesions around the scratch or bite.
Vibrio cholera
causes cholera which is a severe watery, non bloody diarrhea. The diarrhea is characterized by “rice water stools” indicating all fecal material is gone and mucous flecks give the liquid a milky appearance. In infants, dehydration is the immediate problem with electrolyte and fluid replacement necessary for survival. The fecal oral route is responsible for spread. Large inocula are necessary to establish infection, therefore direct person to person spread is unlikely, while drinking contaminated water or eating contaminated, uncooked shellfish are responsible for most disease. Pili and other adhesins permit the organism to attach to the mucosal epithelium and establish residency. Cholera toxin, seen in the next slide, is responsible for the severe diarrhea. Untreated cholera has a high mortality rate. Carriers who have recovered from the disease are a reservoir and shed organisms

Gram negative comma shaped
Halophilic (salt loving)

Vibrio parahemolyticus
found in estuary water is acquired primarily through ingestion of raw shellfish and produces an explosive watery diarrhea

Gram negative comma shaped
Halophilic (salt loving)

Vibrio vulnificus
also found in salt water, can be ingested and cause diarrhea, but also can cause serious disease via wound infection in contaminated water resulting in septicemia, necrosis of tissue and death.

Gram negative comma shaped
Halophilic (salt loving)

Campylobacter jejuni
Most common cause of bacterial gastroenteritis in US (2-3 million cases/year) not reportable
Reservoirs: GI tract of farm animals
Spread: Inadequately prepared food and drink (1000-10,000 organisms necessary for infection)
Organisms multiply in the small intestine, invade the epithelium and produce inflammation
Rapid onset of watery to bloody diarrhea,
abdominal cramping, slight fever
Heliobacter pylori
Reservoir – human gastric lumen
Grows in mucous layer near epithelial surface where pH is 7.4
Produces adhesins, acid inhibitors and urease, which breaks down urea yielding ammonia which buffers stomach acid
Responsible for gastritis, peptic ulcer, gastric adenocarcinoma
Often present without signs or symptoms and
presence increases with aging
Pseudomonas aerugenosa
Gram negative , encapsulated rod
Ubiquitous, opportunist
Does not ferment glucose “nonfermenter”
Opportunist, not normal flora but can persist in debilitated patients
Pyocyanin – blue pigment, fruity odor
Many diseases, nosocomial
Highly antibiotic resistant
Bacteroides fragilis
Anaerobic, encapsulated Gram negative bacilli
Comprise 50% of fecal matter, normal flora
Little or no endotoxin toxicity
Opportunist
Infection after bowel perforation
Most clinically significant of Gram negative rod normal flora
Treponema pallidum
Causes syphilis (sexually transmitted disease {STD}), venereal disease
Corkscrew (helical) shape
Motile via flagella
Gram negative
Too thin (0.1 micron) to be seen under brightfield microscope
Not cultivated on laboratory media
Borrelia burgdorferi
Gram negative, long, thick spiral
Lyme disease
Many manifestations
Zoonotic
Transmission: Ixodes tick saliva
Reservoir: Deer, mouse
Bulls eye (erythema chronicum migrans)
Serological diagnosis
C pneumonia
causes a bronchitis and pneumonia transmitted by person to person aerosol droplets.

Obligate intracellular bacteria
“Energy parasites” unable to make ATP
Life cycle with two forms
Small pleomorphic, Gram-negative
No peptidoglycan
Elementary body-infectious agent
Reticulate body-replicative form
Zoonotic

C psittaci
causes parrot fever or psittacosis. This disease is transmitted by inhalation of contaminated, dried, bird feces and causes illnesses ranging from a mild flu-like illness to serious pneumonia with CNS involvement.

Obligate intracellular bacteria
“Energy parasites” unable to make ATP
Life cycle with two forms
Small pleomorphic, Gram-negative
No peptidoglycan
Elementary body-infectious agent
Reticulate body-replicative form
Zoonotic

Rickettsia
RMSF,caused by Rickettsia, is seen most often in the eastern US as opposed to the rockies. Tick bite, fever and rash are the triad for RMSF clinical diagnosis. The disease is characterized by high fever, rash, headache and myalgias. Complications can lead to encephalitis, renal failure respiratory failure, DIC and death

Small, Gram negative bacilli
Obligate intracellular
Zoonotic-ticks, lice, fleas
Intracellular growth protects
Many species of each Genera and more Genera

Ehrlichia
cause a disease similar to RMSF, but without rash

Small, Gram negative bacilli
Obligate intracellular
Zoonotic-ticks, lice, fleas
Intracellular growth protects
Many species of each Genera and more Genera

Coxiella
cause Q fever which is an acute febrile illness with complications of pneumonia and endocarditis

Small, Gram negative bacilli
Obligate intracellular
Zoonotic-ticks, lice, fleas
Intracellular growth protects
Many species of each Genera and more Genera

Mycobacteria tuberculosis
Aerobic, acid fast bacilli
Facultative intracellular
Cell wall lipids-survival in macrophages
Slow grower
50% mortality in untreated
Transmission- aerosol droplets
Chronic disease

Symptomatic disease
– fever, coughing, bloody sputum - weight loss, loss of energy - progressive lung damage - bacteria may escape lungs ==> systemic disease

Organisms continue to multiply - macrophages die, organisms rephagocytosed
– macrophages fuse, yielding multinucleated giant cells - layers of macrophages, T-cells forms around damaged tissue, this walls off lesion with thick fibrin coat     * granuloma, specifically called tubercle     * calcification ==> lesions in chest X-rays

Mycoplasma pneumoniae
Smallest free living bacteria
Wall-less- pleomorphic
Resistant to cell wall inhibitors
Ubiquitous
Primary atypical pneumonia
Aerosol transmission
Mild, low grade fever
Nonproductive cough

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