Zika disease is caused by a flavivirus originally described in monkeys in the Zika Forest of Uganda in 1947

-It is transmitted by Aedes mosquitoes, sexual intercourse, and vertically from mother to child during pregnancy 

Symptoms & Signs

-Most infected individuals are asymptomatic, others can develop maculopapular rash, arthralgia,myalgia, conjunctivitis, headaches, and fever. 

-There is an increased risk of Guillain-Barré syndrome following Zika infection.

-Congenital fetal infection: greatest risk of serious fetal sequelae is with first-trimester infection; microcephaly, ventriculomegaly, intracranial calcifications, intrauterine growth restriction

Diagnosis: offer testing to any pregnant women traveling from Zika-affected regions (Central America, South America, Caribbean and Pacific Islands) 

-Real-time reverse-transcription polymerase chain reaction (rRT-PCR) testing for Zika viral RNA (in serum, urine, or whole blood) or serology

Treatment

-No specific treatment 

-Only supportive treatment: analgesics, antipyretics, mosquito prevention strategies

-Pregnancy Care: serial fetal ultrasounds every 3 to 4 weeks 

-Unlike dengue, Zika does not lead to hemorrhage or shock

Prevention

-Male patients should avoid attempts at conceiving with their partner for 6 months following symptoms or exposure

-Avoid travel to endemic areas

-Avoid mosquitoes using repellents and wearing protective clothing 

Fever, maculopapular rash + Guillain-Barré syndrome + microcephaly + history of travel to South America + caused by flavivirus which can be active in semen for up to 6 months after infection = Zika

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. 

Inhalation anthrax: Fever, cough, dyspnea, respiratory failure, pleural effusion, hemoptysis, mediastinal edema and widening 

Gastrointestinal anthrax: nausea, vomiting, ulcers, bloody diarrhea, abdominal pain, ascites, and shock 

Diagnosis 

Culture of skin lesions, sputum, blood, and CSF

CXR: a widened mediastinum and pleural effusions

Treatment 

-Supportive care 

-Antibiotics: Ciprofloxacin, Doxycycline, Amoxicillin, Penicillin, Rifampin, Clindamycin, Clarithromycin, Erythromycin, Vancomycin, Imipenem 

Q. What is the most sensitive test for inhalational disease? Chest radiograph

Q.What is the most accurate predictor of inhalation anthrax on chest radiograph?     Mediastinal widening 

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 

Diagnosis: clinical history, physical examination, surgical exploration, 

Gram’s staining, and histopathologic examination. Biopsy shows gram-positive or gram-variable rods and a paucity of leukocytes. Radiographs may show gas bubbles in the tissues 

Treatment 

Gas gangrene is an emergency and requires immediate surgical debridement (excision of all devitalized tissue); administration of penicillin and clindamycin for 10–14 days

Hyperbaric oxygen therapy is controversial .

Q. What is the most effective method of prevention of gas gangrene? Surgical debridement of traumatic injuries 

Q. What is the most common adverse effect of HBO treatment? Middle ear barotrauma 

Staph epidermidis thrive as Gram-positive cocci in clusters. 

-They are Coagulase-negative. Catalase-positive.

-Coagulase negative Staph are the most common cause of nosocomial bloodstream infections 

-They reside on the human skin and can enter the bloodstream at the site of intravenous catheters 

-They cause pyogenic infections on prosthetic implants such as heart valves, pacemakers, and hip joints

St-Treatment: Vancomycin plus either rifampin or an aminoglycoside.

Staph aureus gastroenteritis is a common cause of food poisoning when food is left at room temperature (e.g.at picnics) 

-Foods rich in sugar (custard, cakes, ice creams), dairy, mayonnaise, potato salads, meats such as ham favor Staph growth and enterotoxin production 

-After ingestion, patients develop nausea, vomiting, abdominal cramps, diarrhea and rarely fever.

-incubation period is around 6 hours 

-Diagnosis is by history or/and by isolating S aureus or enterotoxin from the suspected food, vomitus or stool 

-Recovery is rapid usually within 24 hours; hydration if there is dehydration 

Staphylococcal toxic shock syndrome (TSS) is a toxin-mediated clinical illness characterized by rapid onset of fever, diffuse macular rash, hypotension, and multiorgan system involvement. 

-associated with tampon use, S aureus colonization of nasopharynx, vagina, rectum, wounds, abscesses 

-Symptoms are due to the production and release of exotoxins by S.aureus

Symptoms & Signs 

-Tongue is usually reddened (Strawberry tongue) 

-Subconjuntival hemorrhages 

-Fever, vomiting, watery diarrhea 

-Diffuse macular rash followed by desquamation particularly on palms and soles 

Diagnosis: Blood cultures are negative in most cases because symptoms are due to the effects of the toxin; wound cultures show S.aureus  

Treatment: Treatment of shock, antibiotic therapy, Removal of sources of toxin (eg, removal of tampon, drainage of abscess), surgical debridement 

Staph TSS vs Strep TSS: Unlike Staph TSS, Strep TSS generally lack a rash, have bacteremia and have an associated soft-tissue infection 

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 

Healing occurs in 7 to 10 days.

Staphylococci are spherical gram-positive cocci arranged in irregular grapelike clusters 

-All staphylococci produce catalase, whereas no streptococci do 

-Three important species: S. aureus, S. epidermidis, and S. saprophyticus 

Staphylococcus aureus is Coagulase positive; S. epidermidis and S.saprophyticus are coagulase-negative staphylococci.

– The nose is the main site of colonization of S. aureus 

-Staphylococcus aureus causes abscesses, endocarditis, septic arthritis, and osteomyelitis, food poisoning, skin and soft-tissue infections, pneumonia, septicemia, wound infections, conjunctivitis, scalded skin syndrome, and toxic shock syndrome. 

-It is the most common cause of bacterial conjunctivitis.

Treatment: 

Abscesses: incision and drainage 

Antimicrobials: Clindamycin, trimethoprim-sulfamethoxazole, doxycycline, minocycline, dicloxacillin, cephalexin 

Folliculitis

Folliculitis is an inflammatory condition of the hair follicle characterized by groups of papules and dome-shaped pustules with central hairs 

-It can be superficial or deep 

-It can be infectious or non-infectious 

-Infections can be bacterial, viral or fungal 

-Most common bacteria causing folliculitis is Staphylococcus aureus 

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