Tuberculous meningitis

-Tuberculous meningitis occurs in persons of all ages

-After primary infection in the lungs, blood-borne bacilli travel to the meninges 

Symptoms & Signs 

-Gradual onset with headache, fever, irritability, vomiting, nuchal rigidity, neck stiffness, cranial nerve palsies 

-Meningeal involvement is prominent at the base of the brain, affecting the pons and optic chiasm, leading to cranial nerve (especially III, IV, and VI) palsies, which results in visual impairment and diplopia 

Diagnosis 

-Cornerstone of diagnosis: Lumbar puncture 

-CSF obeys the ‘500 rule’: Lymphocytic pleocytosis fewer than 500, protein less than 500 mg/dL; glucose less than 45 mg/dL 

-Pathology: Basal meningeal, white gelatinous exudate containing mononuclear cells  

Treatment 

Treatment with isoniazid, rifampin, and pyrazinamide

All three penetrate the cerebrospinal fluid wall 

Add corticosteroids for hydrocephalus.



Tuberculosis

Tuberculosis is a bacterial infection caused by Mycobacterium tuberculosis 

-M.tuberculosis is an obligate intracellular bacteria that is aerobic, acid fast, and nonencapsulated

-One-third of the world’s population is infected with TB

-TB usually affects the lung, but virtually all other organ systems may be involved

-Infection is transmitted by aerosolized respiratory droplet nuclei

Symptoms & Signs

Pulmonary tuberculosis: Fatigue, weight loss, fever, cough and night sweats; Primary tuberculosis may coalesce into a small granuloma in the upper lobe (Ghon complex) 

Spinal tuberculosis ( Pott disease):  Pain, deformity, the most common sites involved are the thoracic and lumbar vertebrae 

Lymph nodes(Scrofula): painless swelling of cervical and supraclavicular nodes

TB of the skin (Scrofuloderma): Skin ulcerations in the inguinal or cervical region with lymphadenopathy 

Urinary tract: urethral stricture, nephritis, hematuria, “sterile” pyuria 

Diagnosis 

Tuberculin skin test (TST)

Interferon gamma release assays (IGRAs): QuantiFERON, T-SPOT test

Culture of the sputum, urine, tissue, bone 

Biopsy: Granulomas with caseating necrosis 

Chest X-ray: Diagnostic test of choice; shows upper lobe infiltrates with cavitation and/or lymphadenopathy 

Treatment 

-Treatment is with standard multidrug regimens

-Antimicrobial therapy should be administered for 6–9 months

-Isoniazid, rifampin,Rifapentine, pyrazinamide,streptomycin and ethambutol 

-Pyridoxine should be given to patients taking isoniazid to reduce nervous system side effects 

-Test Visual acuity and red-green color vision before initiating ethambutol

-Perform audiometry before initiating streptomycin 

Prevention: BCG vaccine can prevent up to 50% of TB cases 



Plague

-Yersinia pestis is a nonmotile, non-spore forming, bipolar staining Gram-negative bacillus 

-Plague is a systemic zoonosis (infections in humans acquired by contact with animals) caused by Yersinia pestis, a gram-negative bacillus 

-It is a disease of rodents transmitted to humans by flea bites 

Symptoms & Signs 

Plague occurs in three common forms: 

Bubonic plague: sudden onset of fever, chills, prostration,headache, delirium,ulcer at the site of inoculation; regional lymphadenitis with suppuration of nodes (bubo) is the initial lesion

Pneumonic plague (Black Death): Cough, dyspnea, cyanosis, hemoptysis 

Septicemic plague: hemorrhage into skin and mucous membranes, shock

Diagnosis 

Aspirate from a bubo; culture of pus, sputum and blood; serologic testing 

Cultures show bipolar staining, Gram-negative coccobaccili (short rods with rounded ends with a ‘closed safety pin’ appearance) 

Treatment 

Doxycycline, ciprofloxacin,  levofloxacin, moxifloxacin, streptomycin, gentamicin, TMP-SMX


Typhoid Fever

Salmonellosis Typhoid fever 

-Typhoid fever is caused by Salmonella typhi 

-Salmonella is a facultative gram-negative rod

-it is transmitted by the fecal-oral route and by contamination of food or water 

Symptoms & Signs

-Headache, nausea, vomiting, abdominal pain, abdominal distension, “pea soup” diarrhea, erythematous maculopapular lesions that blanch on pressure (Rose spots), slow rise of fever to maximum and then slow return to normal (stepladder fever), relative bradycardia, splenomegaly, temperature pulse dissociation (bradycardia relative to fever)

Diagnosis 

Labs: leukopenia 

Culture: Culture of bacteria from blood, stool, urine, and bone marrow 

Treatment 

Ciprofloxacin, levofloxacin, chloramphenicol, azithromycin

Prevention

-Oral and intramuscular vaccines are available for travelers to endemic areas

-Vaccine repeated after 5 years 

Q. What are the most serious complications of typhoid fever? gastrointestinal hemorrhage and perforation


Moraxella catarrhalis

Introduction

-Moraxella catarrhalis are gram-negative cocci that pair as kidney-shaped diplococci and thus morphologically similar to Neisseria 

-In contrast to pathogenic Neisseria, Moraxella lacks antiphagocytic capsules and IgA proteases.

-It is found only in humans and is transmitted by respiratory aerosol.

Symptoms & Signs

-It causes otitis media and sinusitis primarily in children

-it causes bronchitis and pneumonia, primarily in older people with chronic obstructive pulmonary disease

Diagnosis 

-in culture, it grows as round, opaque colonies on blood and chocolate agar, which typically turn pink after 48 hours

-A characteristic feature of M. catarrhalis: its colonies slide across agar without disruption (hockey puck sign) 

Treatment 

-Antibiotics: amoxicillin-clavulanate, ampicillin-sulbactam, trimethoprim-sulfamethoxazole, macrolides (azithromycin, clarithromycin) fluoroquinolones (ciprofloxacin), and cephalosporins

-M.catarrhalis produces a β-lactamase and is resistant to ampicillin.


Haemophilus influenza

Haemophilus influenzae are pleomorphic, oxidase positive, gram-negative coccobacilli rods that commonly colonize and infect the human respiratory tract. 

-H. influenzae are found on the mucous membranes of the upper respiratory tract in humans with the nasopharynx as the most common site of long-term colonization 

-Clinically, H. influenzae is similar to S. pneumoniae, with a slower onset.

-it is spread by airborne droplets or by direct contact with secretions or fomites. 

-its most serious manifestation is meningitis 

-the most prominent strain is Type b 

-risk factors include alcoholism, smoking, chronic lung disease, advanced age, and HIV infection 

Symptoms & Signs 

H influenzae may cause sinusitis, otitis, bronchitis, epiglottitis, pneumonia,pericarditis, cellulitis, arthritis, meningitis, and endocarditis. 

Diagnosis 

Diagnosis can be established by showing gram-negative coccobacilli in culture

Treatment 

Antibiotics: Beta-lactams (amoxicillin, amoxicillin-clavulanate), cephalosporins, fluoroquinolones, macrolides, and tetracyclines

-In Hib meningitis, administration of glucocorticoids reduces the incidence of neurologic sequelae 

Prevention

All children should be immunized with an Hib conjugate vaccine with the primary series at 2–6 months of age, and a booster dose at 12–15 months of age.


Diphtheria

Diphtheria is an acute toxin-mediated infection of the upper respiratory tract or skin caused by toxin-producing Corynebacterium diphtheriae

-Corynebacteria are gram-positive, non-spore forming, club-shaped rods with a beaded appearance on Gram stain

-it has largely been eradicated in developed nations through widespread vaccination

-It is transmitted from person to person through respiratory secretions or skin lesions. 

Symptoms & signs

Respiratory diphtheria: fever, sore throat with a gray pseudomembrane, malaise, dysphagia, barking cough, stridor, hoarseness, swollen cervical lymph nodes, brawny edema of the neck (bull neck), tachycardia out of proportion to fever

Cutaneous diphtheria: Ulcerative lesions  

Diphtheritic myocarditis:  rapid, thready pulse, arrhythmias, circulatory collapse

Diphtheritic neuropathy: Paralysis of the muscles of the soft palate and pharynx, Peripheral neuritis

Diagnosis 

-Diagnosis is clinical

-Diagnosis is confirmed by isolation of bacteria by culture of a nasopharyngeal swab

-Culture shows club-shaped gram-positive rods in clusters of parallel rays (palisades), in V or L shaped formations referred to as “Chinese characters.” 

-Laboratory must be notified of suspicion in advance

Treatment 

The treatment of choice is antitoxin

To be effective, diphtheria antitoxin should be administered within 48 hours 

Treatment includes antitoxin, antibiotics (Procaine penicillin, erythromycin) , and respiratory support as needed


Influenza

Influenza is an acute respiratory illness caused by influenza A or B viruses

-Transmission occurs primarily by droplet nuclei

-The incubation period is 1–4 days

-The average duration of influenza virus shedding in immunocompetent patients: 5 days 

Symptoms & Signs

-Sudden onset of fever, rhinorrhea, chills, pharyngitis, hoarseness, nonproductive cough,malaise, myalgias, enlargement of cervical lymph nodes, tracheal tenderness 

-The major complication of influenza is pneumonia (most common is  Pneumococcal pneumonia, most serious is staphylococcal pneumonia

Diagnosis

The best specimens for diagnostic testing: nasopharyngeal swabs and nasal aspirate or lavage fluid 

RT-PCR, rapid molecular assays, antigen detection assays, viral culture 

Treatment 

Treatment is supportive

Antiviral therapy: Oseltamivir, inhaled zanamivir (it can cause bronchospasm),peramivir, baloxavir 

Prevention

Annual administration of influenza vaccine is the most effective measure for preventing influenza and its complications. 


Ebola virus disease

-Ebola virus is a single-stranded, nonsegmented, negative-polarity RNA virus

-It causes Ebola hemorrhagic fever (EHF)

-the virions have ‘shepherd’s crook’ appearance 

Symptoms & Signs 

-Transmission from human to human occurs via blood and body fluids

-Fever, headache, sore throat, myalgia, arthralgia, vomiting, diarrhea, rash, uveitis, shock, multiorgan failure 

Diagnosis 

-Virus is detected with a real-time RT-PCR, ELISA, and IgM antibody serum tests 

Treatment 

-There are no approved antiviral medications for treatment of Ebola virus disease

-Supportive therapy with intravenous fluids and electrolytes 

Q. What are the most common complications of EVD? Hypovolemic shock and multiorgan failure


Zika infection

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 

Anthrax bacillus

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 


Gas Gangrene

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 


Staphylococcus epidermidis Endocarditis

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.


staphylococcus aureus food poisoning

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

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 


Staphylococcal Scalded Skin syndrome (SSSS)

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.


Folliculitis due to Staphylococcus

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

Photo by Anna Shvets on Pexels.com

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

 

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. 

Cellulitis may present with or without purulence


Tick-borne encephalitis (TBE)

Introduction

-Tick-borne encephalitis (TBE) is a flaviviral infection caused by TBE virus with three subtypes: European, Siberian, and Far Eastern. 

-Flaviviruses are positive-sense, single-stranded RNA, icosahedral capsid, enveloped viruses

-The principal reservoirs and vectors for TBE virus are ticks

-The virus is transmitted to humans by ticks.

-Outbreaks happened after ingestion of unpasteurized milk from infected sheep and goat  

Symptoms & Signs 

-The incubation period is 7–14 days for tick-borne exposures and only 3–4 days for milk ingestion.

-Most cases are subclinical

-The disease is characterized by a biphasic illness.

Fever-myalgia phase: Fever, arthralgia, headaches, nausea

CNS phase: headaches, meningitis, encephalitis, paralysis  

-Post-encephalitic syndrome: headaches, balance disorders, fatigue, hearing defects, attention deficits, depression, learning impairment 

Diagnosis 

Labs: leukocytosis, neutrophilia, hyponatremia 

CSF: pleocytosis 

PCR: Virus detection by RT-PCR in ticks from TBE patients 

ELISA: TBE virus IgM and IgG are detected by ELISA

Treatment 

Treatment is supportive.

Prognosis 

Complete recovery in most cases 

Prevention 

-There is no available TBE vaccine in the United States

-Effective vaccines are available in Europe, Canada and China