Bacillus anthracis is a gram-positive spore-forming aerobic rod
-Spores are the infectious form of the organism
-They cause a zoonotic infectious disease called Anthrax
-the spores are inoculated through the skin, ingested, or inhaled
-Anthrax occurs naturally in mammals and human anthrax follows exposure to infected animals or animal products or rarely bioterrorism
Symptoms & Signs
Clinically, the disease occurs in three forms: Cutaneous, inhalational, and gastrointestinal
Cutaneous anthrax: the most common and the least morbid form of anthrax.
A painless papule progressing through vesicular, pustular, and escharotic phases resulting in painless, umbilicated ulcer (black eschar/malignant pustule); It can be associated with fever, headache, chills, cough, dyspnea, chest pain, vomiting, and fatigue.
Clostridium perfringens is a large,spore-forming, gram-positive, nonmotile rod with square ends.
-It is commonly found in the environment and intestines.
-It produces α-toxin, a phospholipase, which causes hemolysis, tissue destruction, and shock.
-It can cause wound infections, soft tissue infections, and gas gangrene
-knife or gunshot wounds, vehicular accident wounds, surgical wounds are particularly susceptible to this bacteria
Symptoms & Signs
Sudden onset of excruciating pain at the affected site, brawny edema, tissue death, foul-smelling serosanguineous discharge, blisters with clear to purplish fluid, gas bubbles, crepitance, fever, hypotension, shock, and multiorgan failure
SSSS is caused by hematogenous dissemination of exfoliative toxin produced by S.aureus, a toxin-producing staphylococcus
-Bullous impetigo is caused by the same exfoliative toxins when they affect the skin locally.
-SSSS is most common in neonates and children under the age of 5 years
Symptoms & Signs: Tender, macular erythema develop abruptly over the face, axilla, and groin; as they spread, they form blisters over all parts of the body; the blisters enlarge to slough and give ‘rolled up’ sandpaper-like texture to skin
-Lateral traction of the skin reveals the splitting of the epidermis from the dermis (Nikolsky sign)
Diagnosis: can be established by skin biopsy and isolation of Staph aureus from the lesions
Treatment: Antistaphylococcal antibiotics, intravenous fluids and supportive measures
Pneumococcal meningitis is caused by Streptococcus pneumoniae and is characterized by fever, neck stiffness, bulging fontanelle, irritability, and lethargy.
-S pneumoniae is the most common cause of meningitis in adults and children
-Individuals with splenectomy, sickle cell disease, cochlear implants are at higher risk for pneumococcal meningitis
Symptoms & Signs: nuchal rigidity, irritability, confusion or altered mental status, headache, photophobia, nausea, vomiting, Brudzinski (neck flexion) and Kernig (straight leg raise) signs
Diagnosis: CSF culture
Treatment: Start antibiotics within 60 minutes if bacterial meningitis is suspected; A 2-week course of intravenous antimicrobial therapy with vancomycin, ceftriaxone, cefotaxime, Penicillin G, Ampicillin
-Survivors should be followed for neurologic sequelae like hearing loss, motor and cognitive impairment
–Erysipelas is a sharply demarcated superficial dermal bacterial infection, most often caused by invasion of the superficial lymphatics by β-hemolytic group A streptococci (Streptococcus pyogenes) and rarely by S.aureus
-The most common areas of infection: Legs, followed by the face
-The most common ages affected: Infants and elderly adults
-The lesions are red, raised, rapidly advancing with sharply demarcated margins between involved and normal tissues
-Lesions are painful with bright red edematous indurated appearance giving rise to “peau d’orange” appearance.
-Facial lesions can have ‘butterfly’ pattern
-Milian ear sign: Complete involvement of the ear by erysipelas
-Nearly always unilateral
Erysipelas vs.Cellulitis: Erysipelas is painful, raised, indurated plaque with sharply demarcated margins. It is superficial.
Scarlet fever is a syndrome characterized by exudative pharyngitis, fever, and scarlatiniform rash.
-It is caused by toxin-producing group A β-hemolytic streptococci
-Symptoms and signs include sore throat, fever, rash, strawberry tongue, flushed face, and circumoral pallor
-Rash: Diffusely erythematous rash resembling a sunburn; superimposed fine red papules give the skin a sandpaper consistency; it blanches on pressure, moves from torso to extremities, prominent on the face, chest, palms, fingers and toes; fades in 2-5 days
-Forchheimer spots: Petechiae and punctuate red macules on the soft palate and uvula
-Pastia lines are pink or red lines seen over the elbows and axilla during scarlet fever
Chlamydia pneumoniae: Chlamydia pneumoniae infects only humans; it can cause upper and lower respiratory infections
Chlamydia psittaci: Chlamydia psittaci infects birds, humans and other animals; it causes psittacosis
Symptoms & Signs
Genital infection: Dysuria, urethritis, discharge, which is clearer and less purulent than seen with gonorrhea; Chlamydial infection is asymptomatic in 75% of females
Nucleic acid amplification test (NAAT): is the recommended test for screening asymptomatic at-risk and symptomatic individuals
Culture: In culture, C. trachomatis forms intracytoplasmic inclusions containing glycogen, whereas C. psittaci and C. pneumoniae form inclusions that do not contain glycogen.
Serologic tests: mainly to diagnose infections by C. psittaci and C. pneumoniae
-All chlamydiae are susceptible to tetracyclines, such as doxycycline, and macrolides, such as erythromycin and azithromycin.
-Treatment should be offered to sex partners
-Because of the high rate of coinfection with C.trachomatis and gonococci, any patient with a diagnosis of chlamydia should also be treated for gonorrhea and vice versa
-Chlamydia urethritis: Azithromycin 1 g orally in a single dose or Doxycycline 100 mg orally twice a day for 7 days
-The drug of choice for neonatal inclusion conjunctivitis and pneumonia caused by C. trachomatis is oral erythromycin.
-The drug of choice for C. psittaci and C. pneumoniae infections and for lymphogranuloma venereum is a tetracycline such as doxycycline.
Untreated chlamydia can cause serious complications
Men: Epididymitis, sterility
Women: PID, ectopic pregnancy, infertility
-There is no vaccine against any chlamydial disease
-Educate patients on safer sex practices.
Q.What are the tests of choice for the diagnosis of genital C.trachomatis infections? Nucleic acid amplification tests (NAATs) Q.What is the drug of choice for Chlamydia trachomatis sexually transmitted disease? Azithromycin
Rabies is a rapidly progressive, acute, fulminant, and fatal encephalitis in humans and animals that is caused by infection with rabies virus.
-Rabies virus is usually transmitted to humans by the bite of an infected animal.
-Live virus enters the nerve tissue at the time of the bite, multiplies at the site, and then spreads centripetally along peripheral nerves toward the spinal cord or brain stem via retrograde fast axonal transport. It replicates in gray matter and then spreads to the salivary glands, adrenal glands, and heart.
Symptoms & Signs
-The average incubation period is one to three months.
-The clinical spectrum can be divided into three phases
-The first symptom is usually the paresthesia at the bite site
-Patient later develops malaise, headache, photophobia, fever, anorexia, nausea, vomiting and sore throat
2.Acute neurologic phase:
–Hydrophobia (fear of water), Aerophobia (fear when feeling a breeze)
-Sympathetic overactivity (Increased salivation, ‘foaming at the mouth’, perspiration, lacrimation, pupillary dilatation, nervousness)
-Two acute neurologic forms of rabies are seen in humans:
the encephalitic (furious) form in 80% and
the paralytic form in 20%.
3.Coma: Convulsive seizures, coma and death
-The major cause of death is cardiorespiratory arrest.
1.Rabies antigens: diagnosis by rabies specific antigens
2.Serology: Diagnosis by rabies specific antibodies, detected by immunofluorescence or neutralization tests.
3.Viral isolation: Isolation of the virus in the brain neurons.
Negri bodies: the most characteristic pathologic finding in rabies; They are eosinophilic cytoplasmic inclusions in the brain or the spinal cord. They are composed of rabies virus proteins and viral RNA
‘Rabid or suspected rabid’ animals: should be killed humanely immediately after the bite and sent for laboratory examination of neural tissues
‘Normal’ animals: should be held for observation for 10 days
If they appear abnormal during or after 10 days: kill humanely and send tissues to laboratory
If they appear normal during or after 10 days:individualized treatment
–Avoid contact with any unfamiliar domestic animals and wild animals
–Immunize all household dogs and high risk pets
–Vaccination: Four 1-mL doses of rabies vaccine should be given IM in the deltoid area.
It involves wound cleaning, vaccination and passive immunity
-Thoroughly clean the wound with soap and antiseptics
-Animal bite wounds should not be sutured
Vaccination: Four doses of rabies vaccine over a 14 day period
-Give the vaccine only in deltoid region in adults or anterolaterial thigh in children
–Never administer the vaccine in the gluteal area because antibody responses have been lower after administration at this site
-Pregnancy is not a contraindication for immunization.
Passive immunity: One dose of HRIG along with the first dose of the vaccine
-HRIG is not indicated beyond the 7th day after vaccination is begun, because an antibody response is most likely occurred
-HRIG should never be administered in the same syringe or into the same injection site as the vaccine, because the antibody and vaccine will neutralize each other.
-HRIG should not be given to those with immunoglobulin A deficiency, because small amounts of immunoglobulin A present in HRIG might cause a severe allergic reaction.
-There is no successful treatment for clinical rabies.
-Symptomatic and Palliative treatment using sedatives, antipsychotics, anxiolytics, and pain killers
Poliomyelitis is a disease of the anterior horn motor neurons of the spinal cord and brainstem caused by the poliovirus.
-Anterior horn cells control the skeletal muscle cells of the trunk and limbs
-In up to 95% of cases, poliovirus infection is asymptomatic
-the viral transmission is oral to oral or fecal to oral
-Acutely, the polio virus enters the body through the GI tract, reproduces in the GI lymphoid tissue, and then spreads to the large motor nuclei of the spinal cord, the brainstem, reticular formation, hypothalamus, thalamus, cerebellum and cerebral cortex.
Symptoms & Signs
Thankfully, not every polio infection results in paralysis. It can be divided into following types based on the severity.
Guillain-Barré syndrome: Always think of GBS in the differential diagnosis of polio paralysis. GBS is distinguished from polio by its symmetry, disturbances in sensation, lack of preceding aseptic meningitis, absence of a CSF pleocytosis, presence of multifocal demyelination on electrodiagnostic testing
Virus isolated and typed from throat swabs and rectal swabs; PCR amplification of poliovirus RNA from the CSF
Treatment of poliomyelitis is supportive
-Pain relief, physical therapy
-Mechanical ventilation for respiratory failure
-Intubation or tracheostomy for secretion control
the trivalent live OPV, the inactive (Salk) parenteral vaccine is currently used in the United States for all four recommended doses (at ages 2 months, 4 months, 6–18 months, and at 4–6 years).