Bacterial Diseases

A.Airborne Bacterial DiseasesB.Foodborne & Waterborne Bacterial DiseasesC.Soil borne Bacterial DiseasesD.Arthropod borne Bacterial DiseasesE.Sexually Transmitted Bacterial DiseasesF.Miscellaneous Bacterial Diseases

Airborne Bacterial Diseases

1.Streptococcal Diseases

2.Diphtheria

3.Pertussis

4.Meningococcal Infections

5.Haemophilus influenzae Infections

6.Tuberculosis

7.Pneumococcal Pneumonia

8.Primary Atypical Pneumonia

9.Legionellosis

Foodborne & Waterborne Bacterial Diseases

1.Foodborne Intoxications vs Infections

2.Botulism

3.Staphylococcal Food Poisoning

4.Clostridial Food Poisoning

5.Typhoid Fever

6.Salmonellosis

7.Shigellosis

8.Cholera

9.Diseases associated with Escherichia coli

10.Camphylobacteriosis and Helicobacteriosis

Soil borne Bacterial Diseases

1.Anthrax2.Tetanus3.Gas Gangrene4.Leptospirosis5.Listeriosis

Arthropod borne Bacterial Diseases

1.Plague2.Lyme Disease3.Rocky Mt. Spotted Fever4.Epidemic Typhus5.Endemic Typhus

Sexually Transmitted Bacterial Diseases

1.Syphilis2.Gonorrhea3.Chlamydia4.Chanchroid

Miscellaneous Bacterial Diseases

1.Leprosy2.Staphylococcal Infections3.Pseudomonas aeruginosa Infections

Bacterial infection

Viral infection

BACTERIA VIRUS

SPECIAL TECHNIQUES FOR DIAGNOSING INFECTIOUS AGENTS.

Techniques Infectious Agents

Gram stain Most bacteria

Acid-fast stain Mycobacteria, nocardiae (modified)

Silver stains Fungi, legionellae, pneumocystis

Periodic acid-Schiff Fungi, amebae

SPECIAL TECNIQUES.Mucicarmine Cryptococci

Giemsa Campylobacteria, leishmaniae, malaria parasites

Antibody probes All classes

Culture All classes

DNA probes All classes

• A, Gram stain of sputum from a patient with pneumonia. There are gram-positive cocci in clusters (Staphylococcus aureus) with degenerating neutrophils.

• B, Gram stain of sputum from a patient with pneumonia. Gram-positive, elongated cocci in pairs and short chains (Streptococcus pneumonia) and a neutrophil are seen.

• C, Gram stain of Clostridium sordellii grown in culture. A mixture of gram-positive and gram-negative rods, many of which have sub terminal spores (clear areas), are present.

• Clostridia species often stain as both gram-positive and gram-negative, although they are true gram-positive bacteria.

• D, Gram stain of a bronchoalveolar lavage specimen showing gram-negative intracellular rods typical of Enterobacteriaceae such as Klebsiella pneumonia or Escherichia coli.

• E, Gram stain of urethral discharge from a patient with gonorrhea. Many gram-negative diplococci (Neisseria gonorrhoea) are present within a neutrophil.

• F, Silver stain of brain tissue from a patient with Lyme disease meningoencephalitis.

Clinical or Microbiologic Category Species

Frequent Disease Presentations

1.Infections by pyogenic cocci

Staphylococcus aureus, S. epidermidisStreptococcus pyogenesStreptococcus pneumoniae (pneumococcus)Neisseria meningitidis (meningococcal)Neisseria gonorrhoea (gonococcus)

Abscess, cellulitis, pneumonia, sepsisPharyngitis, erysipelas, scarlet feverLobar pneumonia, meningitisMeningitisGonorrhea

2.Gram-negative infections

Escherichia coli,* Klebsiella pneumonia*Enterobacter (Aerobacter) aerogenes*Proteus spp. (P. mirabilis, P. morgagni)*Serratia marcescens,* Pseudomonas spp. (P. aeruginosa)*

Urinary tract infection, wound infection, abscess, pneumonia, sepsis, shock, endocarditis

Bacteroides spp. (B. fragilis)Legionella spp. (L. pneumophila)

Anaerobic infectionLegionnaires disease

3.Contagious childhood bacterial diseases

Haemophilus influenzae

Meningitis, upper and lower respiratory tract infections

Bordetella pertussisCorynebacterium diphtheria

Whooping coughDiphtheria

4.Enteric infections

Enteropathogenic E. coli, Shigella spp.Vibrio cholerae,Campylobacter jejuni, C. coliYersinia enterocolitica,Salmonella spp. (1000 strains)

Invasive or non-invasive gastroenterocolitis

5.Clostridial infections

Clostridium tetaniClostridium botulinumClostridium perfringens, C. septicumClostridium difficile*

Tetanus (lockjaw)Botulism (paralytic food poisoning)Gas gangrene, necrotizing cellulitisPseudomembranous colitis

6.Zoonotic bacterial infections

Bacillus anthracisYersinia pestisFrancisella tularensisBrucella melitensis, B. suis, B. abortusBorrelia recurrentisBorrelia burgdorferi

AnthraxBubonic plagueTularaemiaBrucellosis (undulant fever)Relapsing feverLyme disease

• GRAM-POSITIVE BACTERIAL INFECTIONS• Common gram-positive pathogens include

Staphylococcus, Streptococcus, and Enterococcus, each of which causes many types of infections.

• Four less common diseases caused by gram-positive rod-shaped organisms are also discussed here: diphtheria, listeriosis, anthrax, and nocardiosis. Clostridia, which are gram-positive, are discussed with the anaerobes.

• All these infections are diagnosed by culture and some special tests mentioned below.

• Staphylococcal Infections• Staphylococcus aureus are pyogenic gram-positive cocci

that form clusters like bunches of grapes. • These bacteria cause skin lesions (boils, carbuncles,

impetigo, and scalded-skin syndrome) as well as abscesses, sepsis, osteomyelitis, pneumonia, endocarditis, food poisoning, and toxic shock syndrome (TSS) .

• S. epidermidis, a species that is related to S. aureus, causes opportunistic infections in catheterized patients, patients with prosthetic cardiac valves, and drug addicts. S. saprophytic us is a common cause of urinary tract infections in young women.

Toxins of S. aureus

• Hemolysins – lyse RBCs

• Leukocidin– damages cell membranes

• Enterotoxins– act in the gastrointestinal tract

• Exfoliative toxin– separates epidermal layers

• Toxic shock syndrome toxin (TSST)

The many consequences of staphylococcal infection

• Whether the lesion is located in the skin, lungs, bones, or heart valves, S. aureus causes pyogenic inflammation that is distinctive for its local destructiveness.

• A furuncle, or boil, is a focal suppurative inflammation of the skin and subcutaneous tissue, either solitary or multiple or recurrent in successive crops.

• Furuncles are most frequent in moist, hairy areas, such as the face, axillae, groin, legs, and submammary folds.

• A carbuncle is a deeper suppurative infection that spreads laterally beneath the deep subcutaneous fascia and then burrows superficially to erupt in multiple adjacent skin sinuses.

• Carbuncles typically appear beneath the skin of the upper back and posterior neck, where fascial planes favor their spread.

• Hidradenitis is a chronic suppurative infection of apocrine glands, most often in the axilla. Infections of the nail bed (paronychia) or on the palmar side of the fingertips (felons) are exquisitely painful.

• Staphylococcal lung infections have a polymorph nuclear infiltrate similar to that of pneumococcus but cause much more tissue destruction.

• S. aureus lung infections usually occur in people with a haematogenous source, such as an infected thrombus, or a predisposing condition such as influenza.

• Staphylococcal scalded-skin syndrome, also called Ritter disease.

Staphylococcal abscess of the lung with extensive neutrophil infiltrate and destruction of the alveoli .

• Antibiotic resistance is a growing problem in treatment of S. aureus infections.

• Methicillin-resistant S. aureus (MRSA) are resistant to all currently available beta-lactam cell-wall synthesis inhibitors (which include the penicillins and cephalosporins).

• Until recently, MRSA was mainly found in healthcare-associated infections, but community-acquired MRSA infections have now become common in many

• Community-acquired MRSA commonly produce a potent membrane damaging toxin, which kills leukocytes and may make these strains of S. aureus particularly virulent.

• Enzymes. Bacteria secrete a variety of enzymes (proteases, hyaluronidases, coagulases, fibrinolysins)

• Neurotoxins produced by Clostridium botulinum and Clostridium tetani inhibit release of neurotransmitters, resulting in paralysis.

• Super antigens are bacterial toxins that stimulate very large number of T lymphocytes by binding to conserved portions of the T-cell receptor, leading to massive T-lymphocyte proliferation and cytokine release.

• The high levels of cytokines can lead to capillary leak and shock. Super antigens made by S. aureus and S. pyogenes cause toxic shock syndrome (TSS).

SPECTRUM OF INFLAMMATORY RESPONSES TO INFECTION

• There are five major histologic patterns of tissue reaction in infections.

• Suppurative (Purulent) Inflammation• Mononuclear and Granulomatous Inflammation• Cytopathic-Cytoproliferative Reaction• Tissue Necrosis• Chronic Inflammation and Scarring.

Pneumococcal pneumonia. Note the intra-alveolar polymorph nuclear exudate and intact alveolar sept

Streptococcus pneumonia

• Small, lancet-shaped cells arranged in pairs and short chains

• Culture requires blood or chocolate agar

• Growth improved by 5-10% CO2

• Lack catalase & peroxidases – cultures die in O2

Streptococci

• Gram-positive spherical/ovoid cocci arranged in long chains• Non-spore-forming, nonmotile• Can form capsules & slime layers• Facultative anaerobes• Sensitive to drying, heat • & disinfectants • 25 species

Streptococcal erysipelas.

StreptococciSkin infections• Impetigo (pyoderma)

– superficial lesions that break and form highly contagious crust

– often occurs in epidemics in school children

• Erysipelas – pathogen enters through a break in

the skin • eventually spreads to the dermis and

subcutaneous tissues– can remain superficial or become

systemicThroat infections• Streptococcal pharyngitis

– strep throat

S. pyogenes• Causes streptococcal

pharyngitis – Strep throat – enters the upper

respiratory tract through respiratory droplets

• Some patients with strep throat may develop scarlet fever– exhibiting a rash caused by

erythrogenic exotoxins

S. pyogenes• Rheumatic fever

– serious complication affecting the joints and heart– causes permanent heart damage called rheumatic heart disease

• Acute glomerulonephritis – rare inflammatory response to M proteins – may lead to renal damage

• Diphtheria• Diphtheria is caused by Corynebacterium

diphtheriae, a slender gram-positive rod with clubbed ends, that is passed from person to person through aerosols or skin exudate.

• C. diphtheria may be carried asymptomatically or cause illnesses ranging from skin lesions in neglected wounds of combat troops in the tropics, and a life-threatening syndrome that includes formation of a tough pharyngeal membrane and toxin-mediated damage to the heart, nerves, and other organs.

• C. diphtheriae produces only one toxin, which is a phage-encoded A-B toxin that blocks host cell protein synthesis.

Membrane of diphtheria (arrow) lying within a transverse bronchus.

• Listeriosis

• Listeria monocytogenes is a gram-positive, facultative intracellular bacillus that causes severe food-borne infections. Mini-epidemics of L. monocytogenes infection have been linked to dairy products, chicken, and hot dogs.

• Pregnant women, their neonates, the elderly, and immunosuppressed persons (e.g., transplant recipients or AIDS patients) are particularly susceptible to severe L. monocytogenes infection.

• In pregnant women (and pregnant sheep and cattle), L. monocytogenes causes an amnionitis that may result in abortion, stillbirth, or neonatal sepsis. In neonates, L. monocytogenes may cause disseminated disease (granulomatosis infantiseptica) and an exudative meningitis, both of which are also seen in immunosuppressed adults.

• Listeria monocytogenes has leucine-rich proteins on its surface called internalins, which bind to E-cadherin on host epithelial cells and induce internalization of the bacterium.

Bacillus anthracis

• facultative• large, block shaped

rods• central spores

– develop under all conditions except in the living body

• virulence factors – capsule & exotoxins

• Cutaneous anthrax, which makes up 95% of naturally occurring infections, begins as a painless, pruritic papule that develops into a vesicle within 2 days. As the vesicle enlarges, striking edema may form around it, and regional lymphadenopathy develops.

• Inhalational anthrax occurs when spores are inhaled. The organism is carried by phagocytes to lymph nodes where the spores germinate, and the release of toxins causes haemorrhagic mediastinitis.

• Gastrointestinal anthrax is an uncommon form of this infection that is usually contracted by eating undercooked meat contaminated with B. anthracis. Initially, the person has nausea, abdominal pain, and vomiting, followed by severe, bloody diarrhea. Mortality is over 50%.

• Anthrax lesions at any site are typified by necrosis and exudative inflammation with infiltration of neutrophils and macrophages.

• The presence of large, boxcar-shaped gram-positive extracellular bacteria in chains, seen histopathologically or recovered in culture, should suggest the diagnosis

Bacillus anthracis in the sub capsular sinus of a hilar lymph node of a patient who died of inhalational

anthrax

Nocardia asteroides in a Gram-stained sputum sample. Note the beaded, branched gram-positive

organisms and leukocytes

• Nocardia are aerobic gram-positive bacteria that grow in distinctive branched chains.

• In culture, Nocardia form thin aerial filaments resembling hyphae.

• Nocardia appear in tissue as slender gram-positive organisms arranged in branching filaments

• Irregular staining gives the filaments a beaded appearance. Nocardia stain with modified acid-fast stains (Fite-Faraco stain), unlike Actinomyces, which may appear similar on Gram stain of tissue.

• At any site of infection, Nocardia elicit a suppurative response with central liquefaction and surrounding granulation and fibrosis. Granulomas do not form.

• GRAM-NEGATIVE BACTERIAL INFECTIONS• Only a few gram-negative bacteria are considered

in this section.• A number of important gram-negative pathogens

are discussed in the appropriate chapters of organ systems, including bacterial causes of gastrointestinal infections and urinary tract infections.

• Gram-negative bacterial infections are usually diagnosed by culture.

Typhoid fever, also referred to as enteric fever, is caused by Salmonella typhi and Salmonella paratyphi.

It affects up to 30 million individuals worldwide each year. The majority of cases in endemic countries are due to S. typhi, while infection by S. paratyphi is more common among travellers,

Typhoid Fever

• caused by Salmonella enterica serotype Typhi – (S. typhi)– typhoid fever – ingested bacilli adhere to small intestine

• cause invasive diarrhea that leads to septicemia

• S. Typhi is transmitted by the five Fs: – Flies– Food– Fingers– Feces– Fomites

• Widal in 1896, and Widal & Sicard in 1896 described the Widal reaction, and this test has proved of value in cases where positive cultures have been unobtainable

Georges- Fernand- Isidor Widal

Shigella

• invades villus of large intestine– can perforate intestine or invade blood

• enters Peyer’s patches & instigates inflammatory response– endotoxin & exotoxins

• Neisserial Infections• Neisseria are gram-negative diplococci that are

flattened on the adjoining sides, giving the pair the shape of a coffee bean

• These aerobic bacteria have stringent nutritional requirements and grow best on enriched media such as lysed sheep's blood agar ("chocolate" agar). The two clinically significant Neisseria are N. meningitidis and N. gonorrhoeae.

• N. meningitides is a significant cause of bacterial meningitis, particularly among children younger than 2 years of age.

Bacterial Meningitis

• Meninges of brain and spinal cord– cross the blood-brain barrier

• can be caused by several bacterial species– Neisseria meningitides – Streptococcus pneumonia– Haemophilus influenzae

Neisseria• Gram-negative diplococci• none develop flagella or spores• capsules on pathogens• Strict parasites

– do not survive long outside of the host• Residents of mucous membranes of warm-blooded animals• Aerobic or microaerophilic• Pathogenic species require enriched complex media and CO2• 2 primary human pathogens

– Neisseria gonorrhoeae– Neisseria meningitidis

1.Neisseria meningitidis

• Virulence factors – capsule, pili, IgA protease

• 12 strains– serotypes A, B, C, cause most cases

• Disease begins when bacteria enter bloodstream, pass into cranial circulation, multiply in meninges– very rapid onset– endotoxin causes hemorrhage and shock– can be fatal

2.Neisseria gonorrhoeae

• Causes gonorrhea• Virulence factors

– pili, other surface molecules, IgA protease• Strictly a human infection• In top 5 STDs• Infectious dose 100-1,000• Does not survive more than 1-2 hours on fomites• Infection is asymptomatic in 10% of males and

50% of females

Neisseria gonorrhea• Males

– urethritis, yellowish discharge, scarring & infertility

– Extra genital infections• anal, pharyngeal,

conjunctivitis, septicemia, arthritis

N.gonorrhea

• Females – vaginitis, urethritis,

salpingitis (PID) mixed anaerobic abdominal infection

– common cause of sterility & ectopic tubal pregnancies

Gonorrhea in Newborns

• Infected as they pass through birth canal

• Eye inflammation, blindness

• Prevented by prophylaxis after birth

Diagnosis

• Gram stain• 20-30% of new cases are

penicillinase-producing PPNG or tetracycline resistant TRNG

• Recurrent infections can occur

• Reportable infectious disease

• Whooping Cough• Whooping cough, caused by the gram-negative

coccobacillus Bordetella pertussis, is an acute, highly communicable illness characterized by paroxysms of violent coughing followed by a loud inspiratory "whoop."

• B. pertussis vaccination, whether with killed bacteria or the newer acellular vaccine, has been effective in preventing whooping cough

• The diagnosis is best made by PCR, because culture is less sensitive.

Whooping cough showing a haze of bacilli (arrows) entangled with the cilia of bronchial epithelial cells

• Pseudomonas Infection• Pseudomonas aeruginosa is an opportunistic aerobic gram-negative bacillus

that is a frequent, deadly pathogen of people with cystic fibrosis, severe burns, or neutropenia.

• 93 Many people with cystic fibrosis die of pulmonary failure secondary to chronic infection with P. aeruginosa. P. aeruginosa can be very resistant to antibiotics, making these infections difficult to treat.

• P. aeruginosa often infects extensive skin burns, which can be a source of sepsis. P. aeruginosa is a common cause of hospital-acquired infections; it has been cultured from washbasins, respirator tubing, nursery cribs, and even antiseptic-containing bottles.

• P. aeruginosa also causes corneal keratitis in wearers of contact lenses, endocarditis and osteomyelitis in intravenous drug abusers, external otitis (swimmer's ear) in healthy individuals, and severe external otitis in diabetics.

• Plague• Yersinia pestis is a gram-negative facultative

intracellular bacterium that is transmitted from rodents to humans by fleabites or, less often, from one human to another by aerosols.

• It causes an invasive, frequently fatal infection called plague.

• Plague, also named Black Death, caused three great pandemics that killed an estimated 100 million people in Egypt and Byzantium in the sixth century;

• bubonic plague the infected fleabite is usually on the legs and is marked by a small pustule or ulcer. The draining lymph nodes enlarge dramatically within a few days and become soft, pulpy, and plum colored, and may infarct or rupture through the skin.

• In pneumonic plague there is a severe, confluent, haemorrhagic and necrotizing bronchopneumonia, often with fibrinous pleuritis.

• In septicemic plague lymph nodes throughout the body as well as organs rich in mononuclear phagocytes develop foci of necrosis.

• Fulminant bacteremias also induce DIC with widespread hemorrhages and thrombi.

• Chancroid (Soft Chancre)• Chancroid is an acute, sexually transmitted,

ulcerative infection caused by Hemophilus ducreyi.

• The disease is most common in tropical and subtropical areas among lower socioeconomic groups

• Chancroid is one of the most common causes of genital ulcers in Africa and Southeast Asia, where it probably serves as an important cofactor in the transmission of HIV infection.

•

• Granuloma Inguinale• Granuloma inguinale, or donovanosis, is a chronic

inflammatory disease caused by Klebsiella granulomatis (formerly called Calymmatobacterium donovani), a minute, encapsulated, coccobacillus.

• The organism is sexually transmitted.

• Clostridial InfectionsClostridium species are gram-positive bacilli that grow under anaerobic conditions and produce spores that are present in the soil.

• C. perfringens, C. septicum, and other species cause cellulitis and myonecrosis of traumatic and surgical wounds (gas gangrene), uterine myonecrosis often associated with illegal abortions, mild food poisoning, and infection of the small bowel associated with ischemia or neutropenia that often leads to severe sepsis.

• C. tetani, the cause of tetanus, proliferates in puncture wounds and in the umbilical stump of newborn infants and releases a potent neurotoxin, called tetanospasmin, that causes convulsive contractions of skeletal muscles (lockjaw). Tetanus toxoid (formalin-fixed neurotoxin) is part of the DPT (diphtheria, pertussis, and tetanus) immunization, which has greatly decreased the incidence of tetanus worldwide.

• C. botulinum grows in inadequately sterilized canned foods and releases a potent neurotoxin that blocks synaptic release of acetylcholine and causes a severe paralysis of respiratory and skeletal muscles (botulism).

• C. difficile overgrows other intestinal flora in antibiotic-treated people, releases toxins, and causes pseudomembranous colitis

Chlamydial Infections• Chlamydia trachomatis is a small gram-negative

bacterium that is an obligate intracellular parasite. C. trachomatis exists in two forms during its unique life cycle.

• The infectious form, called the elementary body (EB), is a metabolically inactive, spore like structure.

Rickettsial Infections

• Members of the order Rickettsiales are vector-borne obligate intracellular bacteria that cause epidemic typhus (Rickettsia prowazekii), scrub typhus (Orienta tsutsugamushi), and spotted fevers (Rickettsia rickettsii and others).

• These organisms have the structure of gram-negative, rod-shaped bacteria, although they stain poorly with Gram stain. Epidemic typhus, which is transmitted from person to person by body lice,

• .

Viral Infections

Viruses are the cause of many clinically important acute and chronic infections affecting virtually every organ system

Organ System Species Disease

Respiratory AdenovirusRhinovirusInfluenza viruses A, BRespiratory syncytial virus

Upper and lower respiratory tract infections, conjunctivitis, diarrheaUpper respiratory tract infectionInfluenzaBronchiolitis, pneumonia

1 Digestive system. Mumps virusRotavirusNorovirusHepatitis A virusHepatitis B virusHepatitis D virusHepatitis C virusHepatitis E virus

Mumps, pancreatitis, orchitisChildhood gastroenteritis Gastroenteritis Acute viral hepatitisAcute or chronic hepatitisWith HBV, acute or chronic hepatitisAcute or chronic hepatitisEnteric ally transmitted hepatitis

2.Systemic with Skin Eruptions

Measles virusRubella virusVaricella-zoster virusHerpes simplex virus 1Herpes simplex virus 2

Measles (rubeola)German measles (rubella)Chickenpox, shinglesOral herpes ("cold sore")Genital herpes

3.Systemic with Hematopoietic Disorders

CytomegalovirusEpstein-Barr virusHIV-1 and HIV-2

Cytomegalic inclusion diseaseInfectious mononucleosisAIDS

2.Systemic with Skin Eruptions

Measles virusRubella virusVaricella-zoster virusHerpes simplex virus 1Herpes simplex virus 2

Measles (rubeola)German measles (rubella)Chickenpox, shinglesOral herpes ("cold sore")Genital herpes

3.Systemic with Hematopoietic Disorders

CytomegalovirusEpstein-Barr virusHIV-1 and HIV-2

Cytomegalic inclusion diseaseInfectious mononucleosisAIDS

4.Arboviral and Haemorrhagic Fevers

Dengue virus 1-4Yellow fever virus

Dengue haemorrhagic feverYellow fever

5.Skin/Genital Warts

Papillomavirus Condyloma; cervical carcinoma

6.Central Nervous System

PoliovirusJC virus

PoliomyelitisProgressive multifocal leukoencephalopathy (opportunistic)

Measles giant cells in the lung. Note the glassy eosinophilic intranuclear inclusions.

• Measles (rubeola) virus is a leading cause of vaccine-preventable death and illness worldwide.

• More than 20 million people are affected by measles each year. In 2005, there were an estimated 345,000 deaths globally,

• the majority of them in children in developing countries.

• Because of poor nutrition, children in developing countries are 10 to 1000 times more likely to die of measles pneumonia than are children in developed countries.

Measles giant cells in the lung. Note the glassy eosinophilic intranuclear inclusions

• 1.

• The blotchy, reddish brown rash of measles virus infection on the face, trunk, and proximal extremities is produced by dilated skin vessels, edema, and a moderate, nonspecific, mononuclear perivascular infiltrate.

• Ulcerated mucosal lesions in the oral cavity near the opening of Stensen ducts (the pathognomonic Koplik spots) are marked by necrosis, neutrophil exudate, and neovascularization.

• The lymphoid organs typically have marked follicular hyperplasia, large germinal centers, and randomly distributed multinucleate giant cells, called Warthin-Finkeldey cells, which have eosinophilic nuclear and cytoplasmic inclusion bodies

• mumps parotitis, which is bilateral in 70% of cases, affected glands are enlarged, have a doughy consistency, and are moist, glistening, and reddish brown on cross-section.

• On microscopic examination the gland interstitium is edematous and diffusely infiltrated by macrophages, lymphocytes, and plasma cells, which compress acini and ducts. Neutrophils and necrotic debris may fill the ductal lumen and cause focal damage to the ductal epithelium.

• In mumps orchitis testicular swelling may be marked, caused by edema, mononuclear cell infiltration, and focal hemorrhages. Because the testis is tightly contained within the tunica albuginea, parenchymal swelling may compromise the blood supply and cause areas of infarction.

• Sterility, when it occurs, is caused by scars and atrophy of the testis after resolution of viral infection.

• In the enzyme-rich pancreas, lesions may be destructive, causing parenchymal and fat necrosis and neutrophil-rich inflammation. Mumps encephalitis causes perivenous demyelination and perivascular mononuclear cuffing.

• Poliovirus is a spherical, unencapsulated RNA virus of the enterovirus genus.

• Other enteroviruses cause childhood diarrhea as well as rashes (coxsackievirus A), conjunctivitis (enterovirus 70), viral meningitis (coxsackieviruses and echovirus), and myopericarditis (coxsackievirus B).

• There are three major strains of poliovirus, each of which is included in the Salk formalin-fixed (killed) vaccine and the Sabin oral, attenuated (live) vaccine.

• .

• West Nile Virus• West Nile virus is an arthropod-borne virus

(arbovirus) of the flavivirus group, which also includes viruses that cause dengue fever and yellow fever.

• West Nile virus has a broad geographic distribution in the Old World, with outbreaks in Africa, the Middle East, Europe, Southeast Asia, and Australia.

• Viral haemorrhagic fevers (VHFs) are systemic infections. • VHF viruses produce a spectrum of illnesses, ranging from

relatively mild acute disease characterized by fever, headache, myalgia, rash, neutropenia, and thrombocytopenia to severe, life-threatening disease in which there is sudden hemodynamic deterioration and shock.

• Herpes Simplex Virus (HSV)• HSV-1 and HSV-2 differ serologically but are

genetically similar and cause a similar set of primary and recurrent infections.

• These viruses produce acute and latent infections. • Both viruses replicate in the skin and the mucous

membranes at the site of entrance of the virus (usually oropharynx or genitals), where they produce infectious virions and cause vesicular lesions of the epidermis

High-power view of cells from the blister in Figure 8-9 showing glassy intranuclear herpes simplex inclusion bodies.

CHRONIC LATENT INFECTIONS (HERPESVIRUS INFECTIONS)

• Fever blisters or cold sores favor the facial skin around mucosal orifices (lips, nose), where their distribution is frequently bilateral and independent of skin dermatomes. Intraepithelial vesicles (blisters), which are formed by intracellular edema and ballooning degeneration of epidermal cells, frequently burst and crust over, but some may result in superficial ulceration

• Gingivostomatitis, which is usually encountered in children, is caused by HSV-1. It is a vesicular eruption extending from the tongue to the retro pharynx and causing cervical lymphadenopathy.

• Swollen, erythematous HSV lesions of the fingers or palm (herpetic whitlow) occur in infants.

Cytomegalovirus (CMV)• Trans placental transmission can occur from a newly acquired or

primary infection in a mother who does not have protective antibodies ("congenital CMV").

• Neonatal transmission can occur through cervical or vaginal secretions at birth or, later, through breast milk from a mother who has active infection ("perinatal CMV").

• Transmission can occur through saliva during preschool years, especially in day care centers. Toddlers so infected readily transmit the virus to their parents.

• Transmission by the venereal route is the dominant mode after about 15 years of age, but spread may also occur via respiratory secretions and the fecal-oral route.

• Iatrogenic transmission can occur at any age through organ transplants or blood transfusions.

An owl’s eye cell diagnostic for cytomegalovirus infection

Figure 24.14

Hepadnaviridae• Hepatitis B Infections

– Causes hepatitis • Inflammation of the liver

– HBV is the only DNA virus that causes hepatitis– Viral infection can cause severe liver damage – Various symptoms

• Jaundice, liver enlargement, abdominal distress, and bleeding into the skin and internal organs

– Coinfection with hepatitis D virus increases risk of permanent liver damage

Hepatitis

Figure 24.21

Three types of viral particles produced by hepatitis B virus

Figure 24.23

Diseases associated with Epstein-Barr virus

Figure 24.13

• Morphology. The major alterations involve the blood, lymph nodes, spleen, liver, CNS, and, occasionally, other organs.

• The peripheral blood shows absolute lymphocytosis; more than 60% of white blood cells are lymphocytes.

• Between 5% and 80% of these are large, atypical lymphocytes, 12 to 16 μm in diameter, characterized by an abundant cytoplasm containing multiple clear vacuolations, an oval, indented, or folded nucleus, and scattered cytoplasmic azurophilic granules

• These atypical lymphocytes, most of which express CD8, are sufficiently distinctive to strongly suggest the diagnosis.

Thank you