- a common condition in which pores become clogged with dried sebum, flaked skin, and bacteria - leads to the formation of blackheads and whiteheads (collectively known as acne pimples) and inflamed, infected abscesses - most common among teenagers PATHOGENS - Propionibacterium acnes and other Propionibacterium spp. - anaerobic, Gram-positive bacilli RESERVOIRS AND MODE OF TRANSMISSION - Infected humans serve as reservoirs, although it is probably not transmissible

- also known as woolsorter’s disease - affect the skin - depressed blackened lesions called eschars form as a result of a necrotoxin (a toxin that kills cells) - lungs (inhalation or pulmonary ____) - gastrointestinal tract (gastrointestinal _____) - Inhalation and gastrointestinal ____ are often fatal, but cutaneous ____ usually is not It is not contagious PATHOGEN - Bacillus anthracis - an encapsulated, spore-forming, Gram-positive bacillus RESERVOIRS AND MODE OF TRANSMISSION RESERVOIR -infected animals, as well as spores that may be present in soil, animal hair, wool, animal skins and hides, and products made from them TRANSMISSION - entry of endospores through breaks in skin - inhalation of spores - ingestion of bacteria in contaminated meat - it is not transmitted from person to person

- Clostridium spores enter and germinate in a wound - the vegetative pathogens produce necrotizing exoenzymes and toxins - destroy muscle and soft tissue - allowing deeper penetration by the organisms. - Gases released from the infecting pathogens cause pockets of gas to develop in the infected tissue - Tissue destruction occurs rapidly, often necessitating amputation of the infected anatomic site - In its most severe forms, produces massive tissue destruction, shock, and renal failure PATHOGENS - Clostridium perfringens - most common cause of it RESERVOIRS AND MODE OF TRANSMISSION - Soil is the primary reservoir - Humans become infected when soil containing clostridial spores enters an open wound - Person-to-person transmission does not occur

more commonly known as Hansen disease TWO FORMS OF ______: 1. __________ - characterized by numerous nodules in skin and possible involvement of the nasal mucosa and eyes 2. __________ - few skin lesions occur - Peripheral nerve involvement tends to be severe, with loss of sensation - Hansen disease is named for G.A. Hansen who in 1873 - discovered the bacillus that causes ____ - _____ occurs primarily in warm, wet areas of the tropics and subtropics PATHOGENS - Mycobacterium leprae - an acid-fast bacillus RESERVOIRS AND MODE OF TRANSMISSION - Infected humans serve as reservoirs - M. leprae is present in nasal discharges and is shed from cutaneous lesions - The exact mode of transmission has not been clearly established - organisms may gain entrance through the respiratory system or broken skin - Leprosy does not appear to be easily transmitted from person to person - Prolonged, close contact with an infected individual appears to be necessary - Tuberculoid form of leprosy is not contagious

- occurs mainly in children - pus-filled blisters (pustules) may appear anywhere on the body. - ________ of the newborn (______ neonatorum) and staphylococcal scalded skin syndrome (SSSS) may occur as epidemics in hospital nurseries PATHOGEN - Staph. aureus, a Gram-positive coccus - may also be caused by Streptococcus pyogenes, which is another Gram-positive coccus. - S. aureus spreads through skin by producing hyaluronidase SSSS - produced by strains of S. aureus that produce exfoliative(or epidermolytic) toxin - causes the top layer of skin (epidermis) to split from the rest of the skin RESERVOIRS AND MODE OF TRANSMISSION - Infected humans serve as reservoirs - Persons with a draining lesion or any purulent discharge are the most common sources of epidemic spread TRANSMISSION - via direct contact with a person having a purulent lesion

usually superficial but may proceed through vesicular, pustular, and encrusted stages

- includes a widespread, pink-red rash, most obvious on the abdomen, sides of the chest, and in skin folds - Severe cases may be accompanied by high fever, nausea, and vomiting

- an acute cellulitis with fever, constitutional symptoms, and hot, tender, red eruptions (sometimes referred to as St. Anthony’s fire)

- caused by the so-called flesh-eating bacteria - inflammation of the fascia (fibrous tissue that envelops the body beneath the skin and also encloses muscles and groups of muscle PATHOGEN - S. pyogenes - Gram-positive coccus - also known as group A beta-hemolytic streptococcus, GAS, and “Strep A.

- is caused by erythrogenic toxin, produced by some strains of S. pyogenes - It can be a complication (sequela) of untreated strep throat(streptococcal pharyngitis) RESERVOIRS - Infected human serve as reservoirs TRANSMISSION - occurs from person to person via large respiratory droplets or direct contact with patients or carriers - Transmission rarely occurs by indirect contact through objects

- often develops as a complication of the common cold. Manifestations - persistent and severe earache - temporary hearing loss - pressure in the middle ear - bulging of the eardrum (tympanic membrane) - Nausea, vomiting - Diarrhea - fever - may lead to rupture of the eardrum, bloody discharge, and pus Severe complications - bone infection, permanent hearing loss, and meningitis - most common in young children, particularly those between 3 months and 3 years of age PATHOGENS - may be caused by bacteria or viruses The three most common bacterial causes 1. Streptococcus pneumoniae (a Gram-positive diplococcus) 2. Haemophilus influenzae (a Gram-negative bacillus) 3. Moraxella catarrhalis (a Gram-negative diplococcus) Less common bacterial causes - Streptococcus pyogenes and S. aureus Viral causes - measles virus, parainfluenza virus, and RSV

- Ear Canal Infection, Swimmer’s Ear - because it often results from swimming in water contaminated with Pseudomonas aeruginosa. - an infection of the outer ear canal - Itching - Pain - malodorous discharge - Tenderness - Redness - Swelling - impaired hearing - most common during the summer swimming season - trapped water in the external ear canal can lead to wet, softened skin, which is more easily infected by bacteria or fungi PATHOGENS • Escherichia coli • Pseudomonas aeruginosa • Proteus vulgaris • Staphylococcus aureus - Fungi - Aspergillus spp. are less common causes of otitis externa. Reservoirs - contaminated swimming pool water - sometimes indigenous microflora - or articles inserted into the ear canal for cleaning out debris and wax

- potentially serious upper respiratory tract disease - acute, contagious bacterial disease primarily involves the tonsils, pharynx, larynx, and nose, and occasionally involves other mucous membranes, skin, conjunctivae, and the vagina characteristic lesion: a tough, asymmetrical, adherent gray-white membrane in the throat, with surrounding inflammation (pseudomembrane) • Swollen and tender cervical lymph nodes • Tonsillitis • swelling of the neck are common (Bull neck) • The membrane may cause airway obstruction Pathogen - toxigenic (toxin- producing) strains of Corynebacterium diphtheriae - The exotoxin(diphtheria toxin) is coded for by a bacteriophage gene. - Infected humans serve as reservoirs Transmission - via airborne droplets, direct contact, and contaminated fomites

- an acute bacterial infection of the throat - Soreness - Chills - Fever - Headache - beefy red throat - white patches of pus on pharyngeal epithelium - enlarged tonsils - enlarged and tender cervical lymph nodes - may spread to the middle ear, sinuses,or the organs of hearing - If untreated, can lead to complications (sequelae) • scarlet fever (caused by erythrogenic toxin) • rheumatic fever • glomerulonephritis - The latter two conditions result from the deposition of immune complexes beneath heart and kidney tissue, respectively - Some strains produce a pyrogenic exotoxin that causes toxic shock syndrome and some strains (the so-called flesh-eating bacteria) can cause necrotizing fasciitis Pathogen • Streptococcus pyogenes beta-hemolytic, catalase-negative, • Gram-positive coccus in chains • also known as group A streptococcus, GAS, or Strep A. • Infected humans serve as reservoirs Transmission • human to human by direct contact, usually hands • aerosol droplets • secretions from patients and nasal carriers • contaminated dust, lint, or handkerchiefs • contaminated milk and milk products have been associated with foodborne outbreaks of streptococcal pharyngitis

- an acute nonspecific infection of the small air sacs (alveoli) and tissues of the lung - fever, productive cough (meaning that sputum is coughed up) - acute chest pain - Chills - shortness of breath - It is clinically diagnosed by abnormal chest sounds and chest radiographs - Pneumonia is often a secondary infection that follows a primary viral respiratory infection PATHOGENS - may be caused by Gram-positive or Gram-negative bacteria, mycoplasmas, chlamydias, viruses, fungi, orprotozoa - Community-acquired bacterial pneumonia • Streptococcus pneumoniae (pneumococcal pneumonia) • S. pneumoniae is the most common cause of pneumonia in the world

- a type of pneumonia caused by Chlamydia psittaci - normally acquired by inhalation of respiratory secretions and desiccated droppings of infected birds (e.g., parrots, parakeets) Pathogens - Fungi - Histoplasma capsulatum (histoplasmosis) - Coccidioides immitis (coccidioidomycosis) - Candida albicans (candidiasis) - Cryptococcus neoformans (cryptococcosis) - Blastomyces (blastomycosis) - Aspergillus (aspergillosis) - Pneumocystis jiroveci (previously considered to be a protozoan) - etiologic agents of pneumonia, especially in immunocompromised individuals Reservoirs - infected humans - infected psittacine birds (parrots and parakeets) in psittacosis, soil, and bird droppings in histoplasmosis and cryptococcosis Transmission - droplet inhalation - direct oral contact - contact with contaminated hands and fomites - inhalation of yeasts and fungal spores

- an acute bacterial pneumonia - usually affects elderly persons - people with preexisting respiratory disease - diabetes mellitus - renal disease - Malignancy - people who are immunocompromised - people who smoke or drink heavily. PATHOGEN • Legionella pneumophila • Gram-negative bacillus • As of 2003, 40 species of Legionella were known. Reservoirs • environmental water sources, such as ponds, lakes, and creeks • hot-water and air-conditioning systems • cooling towers • evaporative condensers • whirlpool spas • hot tubs • shower heads • Humidifiers • tap water • water distillation systems • decorative fountains • dust Transmission • aerosols of Legionella spp. that have been produced by vegetable misting devices in supermarkets. • It is not transmitted from person to person

- has a gradual onset with headache, malaise, dry cough, sore throat, and less often, chest discomfort - amount of sputum the patient produces is scant at first, but may increase as the disease progresses - Illness may last from a few days to a month or more - It is most common in people 5–35 years of age. - Pneumonias produced by mycoplasmas and chlamydias are the most common types of atypical pneumonias PATHOGEN - Mycoplasma pneumoniae - a tiny, Gram-negative bacterium, lacking cell walls - Infected humans serve as reservoirs Transmission - occurs via droplet inhalation - direct contact with an infected person - articles contaminated with nasal secretions or sputum from an ill, coughing patient

- an acute or chronic mycobacterial infection of the lower respiratory tract - malaise, fever, night sweats, weight loss, and productive cough - Shortness of breath, chest pain, hemoptysis (coughing up blood), and hoarseness may occur in advanced stages Widespread tuberculosis - known as miliary tuberculosis - involves many lesions throughout the body Pathogen - Mycobacterium tuberculosis (a slow-growing, acid-fast, Gram- positive to Gram-variable bacillus) - is sometimes referred to as the tubercle bacillus - Infected humans are the primary reservoirs - rarely, primates, cattle, and other infected mammals can serve as reservoirs Transmission - airborne droplets produced by infected people during coughing, sneezing, and even talking or singing - usually following prolonged direct contact with infected individuals • Infected patients show a positive delayed hypersensitivity skin test - Mantoux purified protein derivative [PPD] tuberculin skin test - pulmonary tubercles may be seen on chest radiograph

- a highly contagious, acute bacterial childhood (usually) infection first stage - the prodromal or catarrhal stage - involves mild, cold-like symptoms second stage - the paroxysmal stage - produces severe, uncontrollable coughing fits - coughing often ends in a prolonged, high-pitched, deeply indrawn breath (the “whoop,” from which whooping cough gets its name) - coughing fits produce a clear, tenacious mucus and vomiting - may be so severe as to cause lung rupture, bleeding in the eyes and brain, broken ribs, rectal prolapse, or hernia third stage - the recovery or convalescent stage - usually begins within 4 weeks of onset PATHOGEN Bordetella pertussis

- involves irritation and reddening of conjunctiva, edema of eyelids, mucopurulent discharge, and sensitivity to light - The disease is highly contagious Pathogens - Haemophilus influenzae - Streptococcus pneumoniae • Infected humans serve as reservoirs • Human-to-human transmission occurs via contact with eye and respiratory discharges, contaminated fingers, facial tissues, clothing, eye makeup, eye medications, ophthalmic instruments, and contact lens-wetting and lens-cleaning agent

- is associated with an acute redness and swelling of conjunctiva and purulent discharge - Corneal ulcers, perforation, and blindness may occur if the disease is untreated. Pathogen - Neisseria gonorrhoeae - a kidney bean–shaped, Gram-negative diplococcus • Infected humans—specifically, infected maternal birth canals—serve as reservoirs Transmission - contact with the infected birth canal during delivery - Adult infection can result from finger-to-eye contact with infectious genital secretions

- found on the mucus-secreting epithelial cells of the stomach. No other bacteria are known to grow in the extremely acidic stomach. • It is suspected when a person has upper abdominal pain with nausea or heartburn • Infected humans serve as reservoirs • Transmission probably occurs via ingestion • presumed to be either oral–oral or fecal– oral transmission. urea breath test - patient ingests radioactively labeled urea and his or her breath is analyzed 60 minutes later for radioactively labeled CO2 - The enzyme urease, produced by H.pylori, splits the urea into ammonia and CO2 - the presence of radioactively labeled CO2 indicates the presence of H.pylori

- acute bacterial enteric disease - asymptomatic to severe, with diarrhea, nausea, vomiting, fever, malaise, and abdominal pain • The disease is usually self-limiting, lasting 2–5 days • Stools may contain gross or occult (hidden) blood, mucus, and WBCs. Pathogens - Campylobacter jejuni - curved,S-shaped, or spiral-shaped Gram- negative bacilli, often having a “gull-wing” morphology (a pair of curved bacilli) following cell division Reservoirs are animals - poultry, cattle, sheep, swine, rodents, birds, kittens, puppies, and other pets - Most raw poultry is contaminated with C. jejuni, thus necessitating proper methods of cleaning and disinfecting in the kitchen Transmission - ingestion of contaminated food (e.g., chicken, pork), raw milk, or water - contact with infected pets or farm animals; or contaminated cutting boards

• an acute, bacterial diarrheal disease with profuse watery stools, occasional vomiting, and rapid dehydration • If untreated, circulatory collapse, renal failure, and death may occur. Pathogens - Vibrio cholerae - curved (comma-shaped) Gram-negative bacilli - secrete an enterotoxin - a toxin that adversely affects cells in the intestinal tract • called choleragen - Other Vibrio spp. (Vibrio parahaemolyticus, Vibrio vulnificus) also cause diarrheal diseases - Vibrios are halophilic (salt-loving) and thus are found in marine environments Reservoirs - infected humans and aquatic reservoirs (copepods and other zooplankton) Transmission - fecal–oral route - contact with feces or vomitus of infected people, ingestion of fecally contaminated water or foods (especially raw or undercooked shellfish and other seafood), or mechanical transmission by flies

- gastroenteritis with sudden onset of headache, abdominal pain, diarrhea, nausea, and sometimes vomiting - Dehydration may be severe - may develop into septicemia or localized - infection in any tissue of the body. Pathogens - Salmonella enterica (of which there are more than 2,000 serotypes or serovars) - Gram-negative bacilli invade intestinal cells, release endotoxin, and produce cytotoxins and enterotoxins - Salmonella enteritidis RESERVOIRS - wide range of wild and domestic animals, such as poultry, swine, cattle, rodents, reptiles (e.g., pet iguanas and turtles), pet chicks, dogs, and cats - Infected humans (e.g., patients, carriers) are also reservoirs TRANSMISSION - ingestion of contaminated food (e.g., eggs, unpasteurized milk, meat, poultry, raw fruits and vegetables) - fecal–oral transmission from person to person, food handlers, or contaminated water supplies

- a systemic bacterial disease with fever, severe headache, malaise, anorexia, a rash on the trunk in about 25% of patients, nonproductive cough, and constipation - Bacteremia; pneumonia; gallbladder, liver, and bone infection; endocarditis; meningitis, and other complications may occur Pathogen - Salmonella typhi (also known as the typhoid bacillus - Infected humans serve as reservoirs for typhoid - Some people become carriers following infection, shedding the pathogens in their feces or urine Transmission - via the fecal–oral route - food or water contaminated by feces or urine of patients or carriers - oysters harvested from fecally contaminated waters - fecally contaminated fruits and raw vegetables - from feces to food by mechanical transmission by flies

• bacterial infection of the lining of the small and large intestine, producing diarrhea • as many as 20 bowel movements a day • blood, mucus, and pus Other symptoms • nausea, vomiting, cramps, and fever • Sometimes toxemia (toxins in the blood) and convulsions (in children) occur • Other serious complications, such as hemolytic uremic syndrome, may occur. Pathogens • Shigella dysenteriae, Shigella flexneri, Shigella boydii, and Shigella sonnei • They are nonmotile Gram-negative bacilli that are members of the Enterobacteriaceae family • A plasmid is associated with toxin production and virulence • Infected humans serve as reservoirs • People become infected by direct or indirect fecal–oral transmission from patients or carrier • fecally contaminated hands and fingernails or fecally contaminated food, milk, and drinking water • Flies can mechanically transfer organisms from latrines to food

• the major cause of conditions known as antibiotic-associated diarrhea (AAD) and pseudomembranous colitis (PMC) • frequently occur in patients following antibiotic therapy • Antibiotics that have a profound effect on colonic flora, such as cephalosporins, ampicillin, amoxicillin, and clindamycin, are the drugs most frequently implicated • is a spore-forming anaerobic • Gram-positive bacillus - is a ember of the indigenous microflora in about 2%–3%of healthy, non hospitalized adults - Hospitalized patients frequently become colonized with this as a result of its presence in the hospital environment

- Diarrhea - consists of a hemorrhagic, watery diarrhea with abdominal cramping - patients have no fever or only a slight fever - children younger than age 5 and the elderly develop hemolytic-uremic syndrome (HUS), with anemia, low platelet count, and kidney failure - The first recognized outbreak of diarrhea caused by enterohemorrhagic E. coli (O157:H7) occurred in 1982, involving contaminated hamburger meat— hamburger meat contaminated with cattle feces - Not all of the outbreaks involved meat; some resulted from ingestion of unpasteurized milk or apple juice, lettuce, or other raw vegetables PATHOGEN - Reservoirs include cattle and infected humans - Transmission occurs via the fecal–oral route - inadequately cooked, fecally contaminated beef - unpasteurized milk - person-to-person contact - fecally contaminated water

- consists of a watery diarrhea with or without mucus or blood, vomiting, and abdominal cramping - Dehydration and low-grade fever may occur - most common cause of traveler’s diarrhea worldwide - common cause of diarrheal disease in children in developing countries. Pathogens - enterotoxigenic E. coli that producea heat-labile toxin, a heat-stable toxin, or both - Infected humans serve as reservoirs - Transmission occurs via the fecal–oral route; ingestion of fecally contaminated food or water.

- can be divided into upper and lower - Upper ___ include infections of the kidneys (nephritis or pyelonephritis) and ureters (ureteritis) - Lower ___ include infections of the urinary bladder (cystitis), the urethra (urethritis), and, in men, the prostate (prostatitis) - Most of it are acquired via the ascending route, whereby the pathogen moves up-ward from the urethra - These microorganisms can ascend the urethra and gain access to the urinary bladder - It may result from poor personal hygiene, sexual intercourse, the insertion of catheters, and other means - A patient with a ___ presents with dysuria (difficulty or pain on urination), lumbar pain, fever, and chills

- _______ trachomatis - considered to be the most common sexually transmitted pathogen major causes of: - nongonococcal urethritis (NGU) - epididymitis in men - cervicitis, urethritis, endometritis, and salpingitis in women - causing mucopurulent urethral discharge, urethral itching, and burning on urination - may also cause infertility - Genital chlamydial infection may be concurrent with gonorrhea - Infected humans serve as reservoir - Transmission occurs via direct sexual contact or mother-to-neonate during birth

- Urethral discharge and painful urination are common in infected men, usually starting 2–7 days after infection - Infected women may be asymptomatic for weeks or months, during which time severe damage to the reproductive system may occur PATHOGEN - Neisseria gonorrhoeae - Gram-negative diplococcus - Infected humans serve as reservoirs Transmission - direct mucous membrane-to-mucous membrane contact, usually sexual contact - adult-to-child (may indicate sexual abuse) - mother-to-neonate during birth

treponemal disease that occurs in four stages: (a) primary - a painless lesion known as a chancre which develops at the site where Treponema pallidum entered the genital mucosa or skin through a break in the surface (b) secondary - a skin rash (especially on the palms and soles) about 4–6 weeks later, with fever and mucous membrane lesions (c) a long latent period (as long as 5–20 years) (d) tertiary - with damage to the CNS, cardiovascular system, visceral organs, bones, sense organs, and other sites - Damage to the CNS or heart is usually not reversible PATHOGEN • Treponema pallidum • tightly coiled spirochete that is too thin to be seen with brightfield microscopy • Infected humans serve as reservoirs Transmission - direct contact with lesions, body secretions, mucous membranes, blood, semen, saliva, and vaginal discharges of infected people, usually during sexual contact - blood transfusions - transplacentally from mother to fetus • Primary can be diagnosed by darkfield microscopy • Venereal Disease Research Laboratory (VDRL), and fluorescent treponemal antibody absorption (FTA-Abs) tests - for detecting antibodies in serum or spinal fluid specimens and fluorescent antibody procedures for detecting antigen in material obtained from lesions or lymph nodes

- acute neuromuscular disease induced by a bacterial exotoxin called tetanospasmin, with painful muscular contractions, primarily of the masseter (the muscle that closes the jaw) and neck muscles, spasms, and rigid paralysis - Respiratory failure and death may result. Pathogen - Clostridium tetani - a motile, Gram-positive, anaerobic, spore- forming bacillus that produces a potent neurotoxin - called tetanospasmin