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Questions and Answers
What type of hemolysis is associated with Streptococcus pyogenes?
Which virulent factor does Streptococcus pyogenes possess that interferes with phagocytosis?
Which of the following is a complication associated with streptococcal pharyngitis?
What treatment is preferred for streptococcal pharyngitis?
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Which symptom is common in both streptococcal pharyngitis and scarlet fever?
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What is a characteristic symptom of Scarlet fever?
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What is the primary antibiotic used for treating rheumatic fever?
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Which organism is responsible for causing Vincent’s angina?
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What is a common complication of pneumonia caused by Streptococcus pneumoniae?
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Which treatment is recommended for infections caused by Mycoplasma pneumoniae?
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How is Corynebacterium diphtheriae primarily transmitted?
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What is a common symptom of Pontiac fever?
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How is Bordetella pertussis primarily transmitted?
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What type of bacteria is Chlamydophyla psittaci classified as?
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Which treatment is used for Bordetella pertussis infection?
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What is a key feature of Mycobacterium tuberculosis?
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Which organism is responsible for psittacosis or ornithosis?
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What is the primary method of transmission for Mycobacterium tuberculosis?
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What distinguishes Nocardia from other bacteria mentioned?
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What is the primary treatment for lung abscesses and infections of the female genital tract?
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Which Salmonella species is primarily associated with enteric fevers?
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What is a common symptom of Shigellosis?
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What is the main source of contamination for Salmonella enterocolitis?
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Which treatment is specifically indicated for Shigella dysenteriae infections?
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What is a characteristic feature of Enterohemorrhagic E. coli infections?
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What is the major complication of enteric fevers caused by Salmonella typhi?
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What is the primary characteristic of Shigella species?
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What is the primary cause of vomiting and diarrhea associated with Vibrio parahaemolyticus?
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What is a common symptom of cholera in severe cases?
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Which of the following bacteria are considered part of the normal flora of the intestinal tract?
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What is the most potent beta-lactam drug mentioned for treatment?
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What is the most effective prevention method for Staphylococcus aureus food poisoning?
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Which organism is associated with causing inflammatory diarrhea through colonization of the intestinal lining?
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For Clostridium botulinum food poisoning, which treatment is primarily administered?
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What is the primary complication associated with prolonged antibiotic therapy leading to Clostridium difficile infection?
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Which of the following features distinguishes Escherichia coli in the context of genitourinary tract infections?
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What is the treatment of choice for severe cases of Campylobacter jejuni infections?
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What is the characteristic feature of Staphylococcus saprophyticus in clinical diseases?
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What is a primary characteristic of Bacteroides fragilis in clinical infections?
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Which organism is primarily responsible for causing gonorrhea?
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What is the resistance profile of Enterococcus faecalis?
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Which treatment is considered the drug of choice for Treponema pallidum infections such as syphilis?
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What is a characteristic feature of Proteus mirabilis that aids in its diagnosis?
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Which organism is resistant to Penicillin and Cephalosporin, requiring the use of Metronidazole instead?
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Study Notes
Gram-positive cocci
- Staphylococcus and Streptococcus are examples of gram-positive cocci.
Gram-negative cocci
- Neisseria is an example of a gram-negative coccus.
Gram-positive rods
- Corynebacterium, Listeria, Bacillus, Clostridium, Actinomyces, and Nocardia are examples of gram-positive rods.
Gram-negative rods
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Enteric Tract Organism
- Pathogenic inside and outside the enteric tract: Escherichia and Salmonella
- Pathogenic primarily inside the enteric tract: Shigella, Vibrio, and Campylobacter.
- Pathogenic outside the enteric tract: Klebsiella-Enterobacter-Serratia group and Pseudomonas-Providencia-Morganella group.
- Respiratory Tract Organism: Haemophilus, Bordetella, Legionella, and Yersinia.
- Organism From Animal Sources: Brucella, Francisella, Pasteurella, and Yersinia.
Non-Obligate Intracellular Parasite
- Mycobacterium, Mycoplasma, Treponema, and Leptospira are non-obligate intracellular parasites.
Obligate Intracellular Parasite
- Chlamydia and Rickettsia are obligate intracellular parasites.
Upper Respiratory Tract Infection
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Streptococcus pyogenes
- Gram-positive cocci arranged in pairs or chains, non-motile, non-spore forming, facultative anaerobe, and catalase-negative.
- Possesses M proteins, a virulent factor that interferes with phagocytosis.
- Produces two hemolysins: Streptolysin S and Streptolysin O
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Types of Hemolysis
- Alpha hemolysis: Incomplete lysis with green pigment in the colony.
- Beta hemolysis: Total lysis with a clear area around the colony.
- Gamma hemolysis: Absence of lysis.
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Clinical Disease
- Streptococcal Pharyngitis: Characterized by a sore throat, fever, headache, nausea, cervical lymphadenopathy, and leukocytosis. May lead to tonsilar abscesses, mastoiditis, septicemia, osteomyelitis, and rheumatic fever. Transmitted via respiratory droplets. Treated with Penicillin.
- Scarlet Fever: Symptoms resemble those of Streptococcal pharyngitis accompanied by a rash caused by erythrogenic toxins. Presents with pinkish-red skin rashes and strawberry tongue. Treated with Penicillin.
- Rheumatic Fever: Occurs after streptococcal throat infections. Damages heart muscle and valves with mitral stenosis as a lesion hallmark. Treated with Penicillin.
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Haemophilus influenzae
- Gram-negative pleomorphic bacteria containing endotoxin. Cultured on chocolate agar. Possesses IgA protease which facilitates upper respiratory tract colonization.
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Clinical Disease
- Common Infections: Occurs in older children and adults and includes chronic otitis media, sinusitis, and bronchitis. May cause acute bacterial meningitis.
- Rare Infections: Acute bacterial epiglotitis in young children and pneumonia.
- Mode of Transmission: Respiratory droplets.
- Treatment and Prevention: Ceftriaxone used for acute meningitis. Ampicillin or Cephalosporin treatment for URTI
- Otitis media, sinusitis, and epiglotitis are complications caused by this bacteria.
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Corynebacterium diptheriae
- Gram-positive club-shaped rod often occurring in V and L shaped arrangements or clumps sometimes called “Chinese characters”. Produces diphtheria exotoxin.
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Clinical Disease
- Respiratory Tract Diphtheria (Membranous Pharyngitis): Very rare, begins as a mild pharyngitis with slight fever and chills. Spreads to nasopharynx or down to the larynx and trachea. Produces a firmly adherent, dirty gray, pseudomembrane. May lead to myocarditis, cardiotoxicity, asphyxiation due to the pseudomembrane, and paralysis of the soft palate.
- Mode of Transmission: Respiratory droplets.
- Treatment and Prevention: Treated with antitoxin and antibiotics. Prevented by vaccination with toxoid in DPT followed by boosters.
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Fusobacterium nucleatum
- Gram-negative, polymorphic, long, slender filaments and fusiform rods. Non-spore forming anaerobes that can be easily killed by oxygen. Occurs normally in the mouth (gingival crevice) and occasionally in the stool.
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Clinical Disease:
- Vincent’s Angina or Trench Mouth: Ulcerating, necrotizing gingivitis. May cause head, neck, and chest infections and is commonly isolated in brain abscesses.
- Treatment and Prevention: Treated with Penicillin and Cephalosporin (Penicillin G is preferred).
Lower Respiratory Tract Infections
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Streptococcus pneumoniae
- Part of the normal oropharyngeal flora, gram-positive alpha-hemolytic, lancet-shaped diplococcus.
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Clinical Disease:
- Pneumococcal Pneumonia: Abrupt onset of fever, chills, chest pain, and productive cough. May lead to bacterial meningitis. Other complications may include otitis media and septicemia in infants older than 2 months of age.
- Mode of Transmission: Respiratory droplets.
- Treatment and Prevention: Treated with Penicillin. A vaccine is available for adults.
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Mycoplasma pneumoniae
- The simplest and smallest of the self-replicating prokaryotes, lacking a cell wall. Forms distinctive colonies with a “fried egg” appearance. Mucous membrane pathogen that does not invade other tissues.
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Clinical Disease:
- **Atypical Pneumonia (Walking Pneumonia): ** Slow onset of fever, throbbing headache, malaise, and non-productive cough. Over several weeks, bronchopneumonic pneumonia develops. X-rays reveal segmental lobar pneumonia. Highest incidence in children 5 - 15 years of age. Accounts for 1/3 of all pneumonia cases in teenagers.
- Mode of Transmission: Respiratory droplets.
- Treatment and Prevention: Tetracycline or erythromycin over a prolonged period of time to help resolve manifestations. M.pneumoniae is still shed by treated patients. Reinfections are common.
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Legionella pneumophila
- Poorly staining gram-negative, rod-shaped bacterium that may form longer filaments. Aquatically-based organism. Facultative intracellular parasite. Produces beta-lactamase and endotoxin.
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Clinical Disease:
- Pneumonia (Legionnaire’s disease): Acquired by inhalation of the organism from environmental sources. Most common in smokers, organ transplant recipients, and patients with chronic lung disease. Abrupt onset of fever and chills, initially non-productive cough, headache that may lead to mental confusion, and diarrhea. Not transmitted person-to-person.
- Pontiac Fever: Mild, self-limiting disease consisting of headache, fever, and myalgia without pneumonia.
- Mode of Transmission: Habitat is environmental water sources (e.g. cooling towers). Transmission is via aerosol.
- Treatment and Prevention: Treated with Erythromycin, concurrently given with Rifampin therapy for immunocompromised patients. Contaminated sources should be decontaminated with hyperchlorination, other disinfectants or heat.
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Bordetella pertussis
- Strict aerobic, gram-negative coccobacillus, causes whooping cough.
-
Classifications:
- Bordetella pertussis: Causes classic whooping cough.
- Bordetella parapertussis: Causes a mild form of whooping cough.
- Bordetella bronchiseptica: Primarily an animal pathogen that occasionally causes mild whooping cough.
- Clinical Manifestations: Localized only in the respiratory tract and is highly contagious. Characterized by paroxysmal cough.
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Stages:
- Catarrhal Stage: Mild upper respiratory tract infection (URTI) with sneezing, slight cough, low fever, and runny nose. Lasts 1 to 2 weeks.
- Paroxysmal Stage: Severe cough (5-20 coughs per 20 seconds), little time to breathe causing anoxia and vomiting. Tissue damage makes the patient more susceptible to secondary bacterial infections and pneumonia. Lasts 1 to 6 weeks.
- Convalescent Stage: Less severe cough that may persist for several months.
- Mode of Transmission: Respiratory droplets.
- Treatment and Prevention: Erythromycin is used to eradicate B.pertussis. Supportive measures (removal of secretions, oxygen and humidity, and monitoring electrolytes). Vaccination with DPT.
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Chlamydophila psittaci
- Obligate intracellular parasite. Has a cell wall that lacks peptidoglycan. Resembles gram-negative bacteria. Exists in two forms, an elementary body, which is infectious, and a reticular body, which is the intracellular reproductive form.
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Clinical Disease:
- Psittacosis or Ornithosis: Natural disease of birds, particularly psittacine birds. Zoonotic human disease of the lower respiratory tract that ranges from subclinical to fatal pneumonia. Occupational disease associated with raising and processing of poultry.
- Mode of Transmission: Inhalation of the organism in bird droppings. Birds may present with diarrhea, ruffled feathers, respiratory illness, and a droopy appearance.
- Treatment and Prevention: Treated with Tetracycline and Erythromycin. Destruction of sick birds; Addition of Tetracycline in bird feeds, and improved hygienic standards.
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Mycobacterium tuberculosis
- Slender, slightly curved, rod-shaped bacterium. Cell wall contains mycolic acid. Resistant to acid and alkali, drying, and many disinfectants. Slow-growing bacterium.
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Clinical Disease:
- Tuberculosis: Caused by M.tuberculosis and M.bovis. Most common in those in lower socio-economic classes and individuals infected with HIV. Infections begin in the lungs with a mild inflammatory reaction.
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Progression:
- Phagocytosed organisms replicate rapidly.
- A small Ghon lesion forms in the lung and regional lymph nodes.
- Tissue response produces granulomas containing the infectious agent.
- Exudative and gaseous response with cavitary disease and bronchogenic spread.
- Mode of Transmission: Inhalation of organism in droplet nuclei from another individual or through ingestion of contaminated food (M.bovis).
- Treatment and Prevention: Treated with Isoniazid, Rifampin, Pyrazinamide, and Ethambutol for 2 months followed by 4 months of Isoniazid and Rifampin. Improved hygienic standards and BCG vaccines.
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Mycobacterium avium-intracellulare
- Environmental organism found in water, soil, birds, and other animals. Acid fast with a cell wall similar to M.tuberculosis. Opportunistic organism causing diseases similar to tuberculosis in compromised patients. Not considered contagious.
- Clinical Disease:
- Occurs as chronic bronchopulmonary disease in adults.
- Occurs as overwhelming disseminated infections in AIDS patients.
- Treatment and Prevention: Treatment in AIDS patients is challenging with limited efficacy and organisms may have underlying drug resistance.
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Nocardia
- Filamentous soil bacterium that fragments into rods. Gram-positive and partially acid-fast. Aerobic with relatively slow growth. Related to Corynebacterium, Mycobacterium, and Actinomyces.
- Clinical Disease: Causes pulmonary infections through inhalation of Nocardia organisms. May metastasize to the brain.
- Treatment and Prevention: Treated with sulfonamides. Surgically draining abscesses and removal of necrotic tissues.
- Prevotella melaninogenica - Small, gram-negative coccobacillus with occasional long forms. Has a distinctive black colonial appearance on agar. Part of normal flora of the mouth. Also found in low numbers in the gastro-intestinal and genito-urinary tracts. - Clinical Disease: Causes lung abscesses and infections of the female genital tract. - Treatment and Prevention: Treated with metronidazole and clindamycin. Carbapenems are the most potent beta-lactam drugs.
Gastro-Intestinal Tract Infections
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Salmonella
- Gram-negative, facultative anaerobic, motile rods. Wide host range including humans, animals, and birds. Normal habitat is the intestinal tracts of humans and animals. Categorized into more than 2000 serotypes.
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Classifications:
- Salmonella typhi
- Salmonella enteritidis
- Salmonella typhimurium
- Salmonella paratyphi A
- Salmonella schottmuelleri
- Salmonella choleraesuis
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Clinical Disease:
-
Enterocolitis (gastroenteritis or food poisoning): Most commonly caused by S.typhimurium and S.enteritidis. Occurs in multiple sources of contamination (e.g. food, human carriers, and exotic pets). Characterized by nausea, fever, vomiting, and diarrhea. Usually characterized by the following pattern:
- Ingestion of the organism in contaminated food.
- Colonization of the ileum and cecum.
- Penetration of epithelial cells in the mucosa, invasion leading to acute inflammation and ulceration.
- Increased fluid secretion in the intestines.
- Septicemic (extraintestinal) disease: Acute illness, most often of nosocomial origin. Transmitted via catheterization, contaminated IV fluids, abdominal or pelvic surgery. Characterized by chills, fever, and hypotension. May cause local abscesses, osteomyelitis, and endocarditis if organisms are disseminated widely. Caused by many Salmonella species.
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Enteric Fevers (Typhoid fever): Caused mainly by S.typhi. Transmitted via ingestion of contaminated food and water. Highly infectious even with small numbers of bacteria.
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Progression:
- During an incubation period of 7-14 days, the organism multiplies in the small intestine, enters the intestinal lymphatics, and is disseminated via bloodstream to multiple organs.
- Blood cultures become positive, and the patient experiences malaise, headache, and gradual onset of fever increasing during the day, reaching a plateau of 102F to 105F each day
- Multiplication occurs in the reticulo-endothelial system and lymphoid tissue of the bowel producing hyperplasia and necrosis of the Peyer’s patches.
- Characteristic rash (rose spots) may appear in the second to third week.
- Typically, the disease lasts 3-5 weeks. GI hemorrhage and bowel perforations with peritonitis are major complications.
- After recovery 3% of people become carriers, the organism is retained in the gallbladder and biliary passages.
- Cholecystectomy may be necessary.
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Progression:
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Enterocolitis (gastroenteritis or food poisoning): Most commonly caused by S.typhimurium and S.enteritidis. Occurs in multiple sources of contamination (e.g. food, human carriers, and exotic pets). Characterized by nausea, fever, vomiting, and diarrhea. Usually characterized by the following pattern:
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Treatment and Prevention:
- Enterocolitis: Requires no specific therapy except replacement of fluid loss.
- Septicemic disease: No specific therapy other than maintenance. Can be controlled with antibiotics.
- Enteric fevers: Chlorampenicol is the drug of choice, also Ampicillin.
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Shigella
- Gram-negative, facultative anaerobic, non-motile rods. Pathogenic in small numbers in humans. No known animal reservoir and not found in soil or water unless contaminated with human fecal material. Spread via poor sanitation, and transmitted from person-to-person via food, touch, feces, and flies.
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Classifications:
- Shigella dysenteriae
- Shigella flexneri
- Shigella boydii
- Shigella sonnei
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Clinical Disease:
- Shigellosis (bacillary dysentery): Characterized by acute inflammation of the wall of the large intestine and terminal ileum. Characterized by abdominal pain, cramps, 20+ diarrhea, and fever. Stools are liquid and scant containing mucus, pus, and occasionally blood.
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Treatment and Prevention:
- Only Shigella dysenteriae infections require antibiotic therapy, usually fluoroquinolones.
- Fluid replacement is the most important therapy.
- Vaccines are under development.
- Isolation of carriers, disinfection, and proper sewage disposal are effective.
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Escherichia coli
- Gram-negative, short rods. Facultative anaerobic member of Enterobacteriaceae. Normal flora of the colon.
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Clinical Disease (Diarrheas):
- Enteropathic E. coli: Affects mainly infants and children.
- Enterohemorrhagic E. coli: Contaminant in undercooked meats, cattle being the main reservoir. Secretes Shiga toxin that causes inflammation resulting in bloody diarrhea.
- Enteroinvasive E. coli: Causes bloody diarrhea similar to Shigellosis in children.
- Enterotoxigenic E. coli: Most common cause of traveler’s Diarrhea. Secretes heat-labile and heat-stable enterotoxins. Results in watery diarrhea.
- Enteraggregative E. coli: Characterized by persistent watery diarrhea, frequent bowel movements, abdominal cramps, and fever.### Enterotoxigenic E.coli
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Causes traveler’s diarrhea
Gastro-Intestinal Tract Infections
- Caused by Vibrio cholerae
- Gram-negative, slightly curved, single polar flagella
- Causes classic cholera
- Vibrio parahaemolyticus
- Causes mild gastroenteritis
- Symptoms:
- Ingestion of contaminated food or water
- Abrupt onset of intense vomiting and diarrhea
- Copious fluid loss (15-20L/day)
- Rapid acidosis and hypovolemic shock
- Sunken eyes and cheeks with diminished skin turgor
- Remission or death within 2-3 days
- Treatment:
- Prompt replacement of fluids and electrolytes
- Tetracycline to prevent infecting others
- Patient will recover, but shed the organism for a year
- Prevention:
- Proper sewage disposal and water purification
Gastro-Intestinal Tract Infections
- Caused by Staphylococcus aureus
- Beta-hemolytic, catalase-positive, gram-positive cocci
- Causes “food poisoning”
- Contamination of improperly refrigerated food (e.g., potato salad, ham, custard-filled pastries) by Staphylococcus from food handlers
- Toxin produces abdominal cramping, vomiting, and diarrhea in 2-6 hours
- Symptoms resolve quickly (generally in less than 24 hours)
- Treatment:
- No treatment is generally necessary
- Prevention:
- Properly refrigerate foods
- Wear gloves when handling food
Gastro-Intestinal Tract Infections
- Caused by Campylobacter jejuni
- Gram-negative, oxidase-positive, and catalase-positive curved rod with a polar flagella
- Microaerophilic
- Found in domestic and wild animals, transmitted to humans through dogs or poultry products
- Causes acute gastroenteritis through oral ingestion
- Colonization and invasion of the intestinal lining
- Inflammatory diarrhea
- Treatment:
- Erythromycin in severe cases
- Disease is generally self-limiting (less than 1 week)
- Prevention:
- Sanitation and pasteurization
Gastro-Intestinal Tract Infections
- Caused by Clostridium botulinum
- Gram-positive, anaerobic rod, spore-forming
- Spores are ubiquitous in soil and highly resistant
- Found in contaminated canned meats and vegetables
- Produces an exotoxin
- Acts at the myo-neural junction
- Produces flaccid muscle paralysis
- Suppresses acetylcholine from the axon terminals
- Clinical manifestations:
- Food poisoning:
- Nausea, vomiting, dizziness, cranial palsy, double vision, speech and swallowing problems, muscle weakness, respiratory paralysis, and death (20% cases)
- Intestinal (infant) botulism:
- Occurs in infants after spore ingestion and subsequent germination in the GIT
- Nausea, constipation, generalized weakness and loss of head and limb control
- Wound infection:
- Manifestations are similar to soft-tissue wounds
- Food poisoning:
- Treatment:
- Food poisoning: antitoxin, respiratory control, stomach lavage, and enemas
- Intestinal botulism in infants: supportive care only
- Prevention:
- Proper sterilization techniques for canning meats and vegetables
- Heat food to 80-100°C for 10 minutes to inactivate the toxin
Gastro-Intestinal Tract Infections
- Caused by Clostridium difficile
- Gram-positive, spore-forming anaerobic rod
- Component of normal intestinal flora of infants and some adults
- Produces 2 toxins:
- Enterotoxin – causes GI upset
- Cytotoxin – kills mucosal cells
- Causes pseudo-membranous colitis or antibiotic-associated colitis
- Caused by prolong antibiotic therapy (Ampicillin and Clindamycin)
- Severe gastroenteritis
- Yellow-white plaques in the colonic mucosa
- Treatment:
- Withdraw causative antibiotics
- Vancomycin or metronidazole
- Fluid replacement
Gastro-Intestinal Tract Infections
- Caused by Bacteroides fragiles
- Gram-negative, anaerobic rod, usually pleomorphic
- Grows rapidly under anaerobic conditions
- Stimulated by bile
- Foul smelling, non-communicable
- Causes:
- Gastro-intestinal abscess
- Pelvic inflammatory disease
- Brain abscesses and cellulitis
- Treatment:
- Metronidazole, Clindamycin, and Chloramphenicol
- Resistant to Penicillin and Cephalosporin
Genito-Urinary Tract Infections
- Caused by Escherichia coli
- Gram-negative, short rods
- Facultative anaerobic member of the Enterobacteriaceae
- Normal flora of the colon
- Clinical manifestations:
- Cystitis: painful frequent urination, hematuria and urgency
- Pyelonephritis: infection of the kidneys following ascending urinary tract infection, characterized by fever, flank pain, tenderness, possible endotoxin shock
- Prostatitis: occurs in older men, characterized by inflamed prostate gland
- Treatment:
- Penicillin and Ciprofloxacin
Genito-Urinary Tract Infections
- Caused by Staphylococcus saprophyticus
- Gram-positive cocci, clustered
- Non-hemolytic, coagulase-negative
- Novo-biocin resistant
- Cultured on blood agar
- Causes “Honeymoon Cystitis”
- In sexually active, young women
- Treatment:
- Penicillin
Genito-Urinary Tract Infections
- Caused by Proteus mirabilis
- Gram-negative, motile, short rod
- “Swarming” growth on blood agar
- Opportunist transmitted via catheters
- Causes:
- Urinary tract infections
- Renal stones and calculi causing urinary tract obstruction
- Treatment:
- Ampicillin and Cephalosporin
- Resistant to Tetracycline
Genito-Urinary Tract Infections
- Caused by Enterococcus faecalis
- Part of normal intestinal and oral flora of humans and animals
- Facultative, anaerobic, gram-positive cocci
- Produces beta-hemolysis on blood agar
- Causes:
- Urinary tract infections
- Septicemia and endocarditis
- Treatment:
- Antibiotic sensitivity testing
- Relatively resistant to many antibiotics
- Inhibited but not killed by Penicillin
Genito-Urinary Tract Infections
- Caused by Neisseria gonorrhoeae
- Oxidase-positive, gram-negative diplococcus
- Kidney-bean morphologic appearance
- Epidemic, highest incidence in the most sexually active groups
- Causes Gonorrhea
- Men: usually symptomatic, urethritis, dysuria, purulent discharge
- Women: usually asymptomatic, purulent vaginal discharge, intermenstrual bleeding, pelvic inflammatory disease
- Complications:
- Rectal infections (anal gonorrhea), in homosexual males, painful defecation, discharge, constipation, proctitis
- Pharyngitis (pharyngeal gonorrhea), purulent exudate, mimics sore throat and streptococcal sore throat
- Opthalmia neonatorum (infant eye infection), contracted during birth, purulent conjunctivitis, potential blindness
- Disseminated infection (bloodstream invasion), dermatitis, painful arthritis
- Treatment:
- Ceftriaxone
- Tetracycline for possible Chlamydial infection
- Prevention:
- Topical silver nitrate for infants
- Use of condom
Genito-Urinary Tract Infections
- Caused by Treponema pallidum
- Cork-screw-shaped, motile organism
- Causes chronic, painless infections (30-40 years)
- Causes Syphilis
- Primary: localized infection with erythema, induration with a firm base (chancre) and ulceration
- Secondary: disseminated infection with lesions in most tissues, muco-cutaneous rash
- Tertiary: aortitis and CNS problems may occur
- Treatment:
- Long-acting Penicillin
- Prevention:
- Use of condom and protected sex
Genito-Urinary Tract Infections
- Caused by Chlamydia trachomatis
- Obligate intracellular parasite
- Has a cell wall but lacks peptidoglycan
- Resembles gram-negative bacteria
- Causes:
- Subtypes D-K: non-gonococcal urethritis, pelvic inflammatory disease, neonatal pneumonia
- Subtype L1, L2, L3: lymphogranuloma venereum, suppurative inguinal adenitis
- Treatment:
- Doxycycline or erythromycin
- Prevention:
- Use of condom and protected sex
Central Nervous System Infections
- Caused by Streptococcus agalactiae
- Beta-hemolytic, gram-positive cocci
- Part of normal vaginal flora
- 5 serotypes (Ia, Ib, Ia/c, and III)
- Causes early onset of neonatal sepsis (birth – 7days) in newborns, 1 in 100 becomes chronically ill
- Associated with obstetric complications, premature birth, respiratory distress, fatality rate > 50%
- Causes late onset of neonatal sepsis (7 days – 4 months)
- Meningitis leading to permanent neurologic change
- Fatality rate of 15-20%
- Treatment:
- Penicillin G
CNS Infections
- Caused by Neisseria meningitidis
- Gram-negative, oxidase-positive, uses glucose and maltose
- Colonizes upper respiratory tract before causing meningococcemia
- Causes meningococcemia (via droplet transmission)
- Begins as mild pharyngitis with occasional slight fever
- Initial signs: vomiting, headache, stiff neck
- Petechial eruption progresses from erythematous macules to purpura
- Vasculitic purpura is the hallmark
- Waterhouse-Friderichsen syndrome: fulminating meningococcemia, hemorrhage, circulatory failure, adrenal insufficiency
- Treatment:
- High dosage IV Penicillin
- Prevention:
- Vaccine
CNS Infections
- Caused by Clostridium tetani
- Gram-positive, spore-forming anaerobe
- Terminal spore
- Tennis racket appearance
- Ubiquitous in soil
- Causes Tetanus
- Transmitted via woundsite
- Manifestations: muscle stiffness, tetanospasm of lockjaw and backarching
- Death occurs after several weeks from exhaustion and respiratory failure
- Treatment:
- Antitoxin and Penicillin
- Debridement of tissue
- Tracheostomy to aid breathing
- Prevention:
- Toxoid vaccination
- Booster every 10 years
CNS Infections
- Caused by Haemophilus influenzae
- Gram-negative pleomorphic bacteria
- Contains endotoxin
- Cultured on chocolate agar
- Causes Meningitis
- Unvaccinated children 3 months – 2 years of age
- Rapidly progressive, CNS deficits (hydrocephalus, mental retardation, speech and hearing problems)
- Treatment:
- Ceftriaxone or Cefotaxime (used with dexamethazone) for meningitis
- Prevention:
- Conjugated vaccine
Cardiovascular Infections
- Caused by Viridans Streptococci
- Alpha-hemolytic streptococci
- Predominate in the normal oral cavity
- Non-invasive opportunist, commonly disseminated intravascularly by dental manipulation
- Classified as:
- Streptococcus salivarius
- Streoptococcus mitis
- Streptococcus mutans
- Streptococcus sanguis
- Causes:
- Subacute bacterial endocarditis (SABE) - inflammation induced by deposition of viridans streptococci on heart valves
- Dental caries (tooth decay)
- Treatment:
- Penicillin
Cardiovascular Infections
- Caused by Staphylococcus aureus
- Beta-hemolytic, catalase-positive, gram-positive cocci
- Adheres to heart valves, including prosthetic valves
- Causes S.aureus bacterial endocarditis
- Rapid damage to the heart
- Toxins:
- Coagulase – forms platelet and fibrin clots, reducing phagocytic cell access to S.aureus
- Cytolytic toxins – damage cells
- Treatment:
- Penicillin
Skin and Soft Tissue Infections
- Caused by Staphylococcus aureus
- Beta-hemolytic, coagulase-positive, gram-positive cocci
- Causes:
- Skin infections: impetigo, folliculitis, boils, carbuncles, styes, surgical wound, burn and traumatic-lesion infection
- Scalded skin syndrome: bullae and desquamation of body surface (children < 5 years old)
- Toxic shock syndrome, food poisoning, pneumonia, osteomyelitis and endocarditis
- Treatment:
- Penicillin for sensitive isolates
- Cloxacillin or Nafcillin
- Prevention:
- Drainage of lesion
- Hand washing
Skin and Soft Tissue Infections
- Caused by Clostridium perfringens
- Anaerobic, spore-forming, large, gram-positive rod
- Heat-resistant spores, produce 12 exotoxins causing food poisoning
- Natural habitat is soil, contamination of home-canned goods
- Causes:
- Soft tissue (muscle) wound infection:
- Anaerobic cellulitis – destruction of traumatized tissue
- Myonecrosis (gas gangrene) – rapid progression to shock and renal failure
- Food poisoning: ingestion of contaminated food with preformed exotoxin, abdominal pain with severe cramps and diarrhea (1 day)
- Soft tissue (muscle) wound infection:
- Treatment:
- Anaerobic cellulitis: Penicillin and additional antibiotics, debridement of necrotic tissue
- Myonecrosis: Penicillin and antitoxin, debridement of necrotic tissue, hyperbaric oxygen
- Food poisoning: usually not necessary, self-limiting
Skin and Soft Tissue Infections
- Caused by Pseudomonas aeruginosa
- Small, polarly flagellated, gram-negative rod with pili
- Oxidase-positive, found in water and soil
- Natural habitat is soil, contamination of home-canned goods
- Causes:
- Cellulitis: patients with burns and wounds
- Blue-green pus, grape-like sweet odor
- Septicemia: hematogenous spread from local lesions or GIT, causes shock
- Distinctive skin lesion called ecthyma gangrenosum (dermal veins and tissue invaded)
- Lesions become necrotic
- Treatment:
- Combination therapy (aminoglycosides) and an antipseudomonal beta-lactam agent
- Prevention:
- Good sanitation
Skin and Soft Tissue Infections
- Caused by Streptococcus pyogenes
- Causes:
- Impetigo: exudative infection of the epidermis, primarily children
- Cellulitis and erysipelas: infection through a small break in the skin
- Cellulitis – lesion is confined
- Erysipelas – lesion spreads through lymphatics
- Fascitis: rapidly spreading, dangerous infection of the fascia, common in diabetic patients
- Treatment:
- Penicillin and debridement of necrotic tissues
Multi-System Infections
- Caused by Listeria monocytogenes
- Gram-positive, psychrophile, club-shaped bacillus
- Causes zoonosis (birds, fish, mammals)
- Transmitted via contact with animals and their feces, unpasteurized milk, contaminated vegetables
- Causes:
- Infections in pregnant women: flu-like symptoms, potential to pass Listeria to fetus transplacentally or during birth
- Granulomatosis infantiseptica: widely distributed abscesses and granulomas in the fetus
- Meningoencephalitis: neonates, patients with malignancy, immuno-compromised patients, adults > 40 years
- Septicemia: same population as for meningoencephalitis
- Treatment:
- IV Ampicillin
- Poor prognosis, high fatality rate in newborns
- Prevention:
- Animal reservoir is a major problem
- Milk pasteurization kills the microorganism
- Immediate treatment for pregnant women
Multi-System Infections
- Caused by Yersinia pestis
- Gram-negative, oxidase-negative, catalase-positive
- Facultative intracellular organism
- Transmitted via animal bite (squirrel, rat, prairie dogs)
- Causes:
- Bubonic plague: begins as a flea bite with regional lymph node swelling, necrosis and suppuration producing bubo
- Fever, bubos, conjunctivitis
- Organism may spread to the lungs to produce pneumonia
- Pneumonic plague: respiratory exposure to Y. pestis, rapidly necrotic pneumonia, death within days
- Treatment:
- Streptomycin
- Prevention:
- Vaccine for those at high risk
Multi-System Infections
- Caused by Borrelia burgdorferi
- Large, motile spirochete
- Carried by Ixodes tick
- Transmitted via tick bite
- Causes Lyme disease:
- Bloodstream infection that seeds other tissues (brain, heart, joints)
Lyme Disease
- The hallmark of early Lyme disease is erythema migrans, a circular rash that spreads outwards from the bite site.
- Malaise, fever, fatigue, chills, and stiff neck can occur for several weeks.
- In stage 2, neurological and heart problems arise, including meningitis, cranial neuropathy, and some cardiac dysfunction.
- Stage 3 involves joint problems producing gout and arthritis which can last for 3-7 years.
- Neural dysfunction can lead to dementia and paralysis.
- Doxycycline, amoxicillin, or cefuroxime are used to treat primary infection.
- Ceftriaxone is used to treat carditis and meningitis.
- Doxycycline or azithromycin are used to treat arthritis.
- Protection from tick bites is key to prevention.
Rocky Mountain Spotted Fever
- Rickettsia rickettsii is a gram-negative obligate intracellular bacterium.
- It is transmitted through tick bites.
- The initial stage of Rocky Mountain Spotted Fever causes a rash on the extremities that spreads to the trunk.
- Fever, chills, headache, and myalgias occur.
- A hemorrhagic rash, stupor, delirium, and shock develop a few days later.
- The treatment of choice is Doxycycline.
- Avoiding ticks is key to prevention.
Q Fever
- Coxiella burnetii is a gram-negative intracellular organism that replicates in the cytoplasm.
- Transmission occurs via aerosols to humans aiding animals during birth.
- It can also be transmitted through milk or dust.
- Q Fever presents with fever, chills, and headache but no rash.
- There is pneumonia that can be mild.
- Hepatosplenomegaly also occurs.
- Complications include myocarditis, pericarditis, endocarditis, and encephalitis.
- Tetracycline is the drug of choice for treatment.
Tularemia
- Francisella tularensis is a gram-negative bacterium.
- It is transmitted to humans through bites of ticks, deer flies, black flies, mosquitoes, mites, or lice.
- It is mainly found in rabbits and rodents.
- Tularemia (rabbit fever or deer fly fever) is characterized by macrophage infiltration, granulomas, and necrosis of infected tissues.
- Regional lymph nodes become infected and suppurate, spreading to the lungs, liver, and spleen.
- Clinical manifestations vary depending on the site of organism entry.
- Ulceroglandular tularemia is a skin infection
- Oculoglandular tularemia is an eye infection.
- Pneumonic tularemia is a lung infection.
- Typhoidal Tularemia is a gastrointestinal infection.
- Streptomycin is used to treat Tularemia.
- Meat should be cooked thoroughly, especially rabbit meat.
- A vaccine is recommended for high-risk groups.
Brucellosis
- Brucella species cause zoonosis with most infections occurring in livestock farmers and meat processors.
- Brucella is transmitted to humans through direct contact with infected animals and the ingestion of unpasteurized milk and dairy products.
- The Brucella species include:
- Brucella suis (swine)
- Brucella melitensis (goats)
- Brucella abortus (cattle).
- Brucellosis (undulating fever) causes the organism to localize and cause granulomas in the spleen, liver, bone marrow, and lymph nodes.
- Patients exhibit intermittent fever and profound muscle weakness, chills, sweats, anorexia, headache, backache, depression, and nervousness.
- Tetracycline and Streptomycin are administered for 3-6 weeks for treatment.
- Milk pasteurization is a key preventive measure.
Anthrax
- Bacillus anthracis is prevalent in goats, sheep, and cattle.
- Transmission occurs through the inhalation of spores.
- Cutaneous anthrax results from the entry of spores into a cut or abrasion.
- A small pustule develops, turning into a large vesicle surrounded by an inflammatory ring at the base.
- The fatality rate for cutaneous anthrax is 10%.
- Pulmonary anthrax (Wool-Sorters' disease) results from spore entry into the lungs.
- Pulmonary anthrax has an abrupt onset with high fever, malaise, cough, myalgias, hemorrhagic necrosis of the lymph nodes, respiratory distress, and cyanosis.
- Penicillin is administered intravenously for treatment.
- Infected animals should be killed.
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Description
Test your knowledge on Streptococcus pyogenes and related bacterial infections with this microbiology quiz. It covers virulence factors, common complications, and treatment options associated with various bacterial pathogens. Ideal for students studying microbiology or healthcare professionals.
