CENTRAL NERVOUS SYSTEM INFECTIONS
BASICS
An acute inflammation and infection of the meninges which surround the brain and spinal cord
ETIOLOGY
Children: group B streptococci and E. coli, Streptococcus pneumoniae, Neisseria meningitidis, Hib
Adults: S. pneumoniae, N. meningitidis, group B streptococci
SIGNS AND SYMPTOMS
Fevers, headache, nausea, vomiting, meningismus, altered mental status (AMS)
Kernig sign:
• Pain or resistance with passive knee extension with hip flexion
Brudzinski sign:
• Passive flexion of neck causes hip flexion
DIAGNOSTICS
Consider head CT if neurologic deficits
Lumbar puncture (LP)
• Elevated white blood cell (WBC), protein
• Decreased glucose in cerebrospinal fluid (CSF)
• Often xanthochromia present
TREATMENT
ABCs (airway, breathing, circulation), intravenous fluids, supplemental oxygen
Seizure treatment as needed, consider steroids
Mannitol 1 g per kg IV for increased intracranial pressure (ICP)
Antibiotics:
• Infants to 3 months: ampicillin 200 mg per kg and cefotaxime or ceftriaxone 100 mg per kg
• Three months and older: cefotaxime or ceftriaxone 100 mg per kg and vancomycin 15 mg per kg
• Adults 18 to 50 years old: ceftriaxone 2 g IV Q12 and vancomycin or rifampin if S. pneumoniae resistance
• Adults older than 50 years old: consider coverage for gram negative: ceftriaxone 2 g IV Q12 and ampicillin 2 g IV Q4 plus vancomycin or rifampin if S. pneumoniae resistance
Prophylaxis is considered for those in close contact
BASICS
Inflammation of meninges
Less severe than bacterial meningitis, also called aseptic meningitis
It can be severe or fatal depending on the virus causing the infection, the person’s age, or if immunocompromised
ETIOLOGY
Enterovirus is most common
Epstein–Barr virus (EBV), herpes simplex viruses (HSVs), and Varicella zoster virus (VZV)
Influenza, measles
SIGNS AND SYMPTOMS
Headache, fever, stiff neck, photophobia
DIAGNOSTICS
LP for CSF: WBC low to 1,000, low to normal protein, normal to high glucose
HSV considered if AMS, or history of HSV virus
TREATMENT
ABCs, IV fluids
Consider antivirals (acyclovir)
Fungal is considered for immunocompromised patients and those immunosuppressed from recent surgery, prednisone use
• Cryptococcus is the most common
• Fungal treatment is amphotericin B, flucytosine, and fluconazole
BASICS
Inflammation of brain parenchyma with inflammation of meninges or spinal cord
ETIOLOGY
Most commonly caused by viral infection:
• Herpes (HSV, VZV, cytomegalovirus [CMV])
• Arboviruses (eastern equine encephalitis [EEE], West Nile virus)
• Enteroviruses
Less likely caused by bacterial or fungal pathogens
Hematogenous versus neuronal spread to central nervous system (CNS), less often spreads through respiratory or gastrointestinal (GI) routes, blood transfusion, or organ transplantation
SIGNS AND SYMPTOMS
Fever, headache, AMS
Neurologic or psychiatric symptoms, cognitive deficits, focal neurologic deficits, or seizure
DIAGNOSTICS
ABCs, supportive, IV fluids
Head CT prior to LP
MRI more sensitive and preferred imaging modality if high suspicion
Head CT often normal but may show diffuse cerebral edema or focal edema
If HSV encephalitis: parenchymal hemorrhages in frontal and/or temporal lobes with CSF normal or similar to that seen with viral infections causing aseptic meningitis
TREATMENT
Empiric treatment with ceftriaxone, vancomycin, acyclovir, dexamethasone, after cultures but no need to wait for CT and LP
Admit due to high mortality
BASICS
Infection in brain tissue coming from local source
ETIOLOGY
Usually polymicrobial
Most common causes: Staphylococcus aureus, aerobic, and anaerobic streptococci
One-third of cases are due to sinus, otic, or odontogenic
Ten percent are due to direct implantation by neurosurgery or trauma
SIGNS AND SYMPTOMS
Headache, fever, AMS, or neurologic deficit
Seizures, increased ICP (confusion, vomiting, somnolence)
DIAGNOSTICS
CT scan with contrast
MRI is highly sensitive
TREATMENT
ABCs, supportive, IV fluids
Broad-spectrum antibiotics, including cefotaxime and Flagyl
Neurology, neurosurgery, and ID consult
Possible surgery needed
BASICS
Acute gastroenteritis is a common illness that is due to a variety of bacterial, viral, parasitic, and toxin-mediated causes
Infection is spread easily through fecal–oral contamination and through person-to-person contact
Main stay of disease prevention is hand hygiene
ETIOLOGY
Ingestion of pathogen that leads to the development of acute diarrhea (Table 15.1)
| Causes of Acute Infectious Diarrhea |
| Nonbloody | Bloody |
Viral | Norovirus, rotavirus, adenovirus, astrovirus |
|
Bacterial | E. coli, Shigella, Salmonella, Yersinia, Campylobacter | E. coli O157:H7, Shigella, Salmonella, Yersinia |
Parasitic | G. lamblia, Cryptosporidium, Cyclospora | E. histolytica |
Toxin | Clostridium difficile, S. aureus, Clostridium perfringens, Bacillus cereus |
|
SIGNS AND SYMPTOMS
Diarrhea may be bloody or nonbloody
May be associated with vomiting
Abdominal pain
Fevers and chills
DIAGNOSTICS
Stool studies for immunocompromised individuals, those at high risk for spread of infection (nursing home resident, health care worker, day care worker, food handler)
Clostridium difficile toxin assay if suspecting C. difficile
If healthy individual with nonbloody diarrhea and low risk for spread, no diagnostic stool studies are needed
TREATMENT
Supportive therapy
Geared toward specific pathogen responsible for infection
BASICS
Most common cause of acute gastroenteritis in the United States
People can become infected with norovirus many times in their lives
Easily and rapidly spread virus
Virus spread rapidly in nursing homes, day care facilities, and cruise ships
Outbreaks common in the United States from November to April
ETIOLOGY
Virus spread through ingestion of food contaminated by norovirus
Fecal–oral route
SIGNS AND SYMPTOMS
Fever
Abdominal pain
Nausea and vomiting
Nonbloody diarrhea
DIAGNOSTICS
Clinical diagnosis
TREATMENT
Supportive care
Infants, young children, and the elderly more likely to become dehydrated
Treat with IV fluids for dehydration
BASICS
Viral cause of acute gastroenteritis
Children affected more often
Infection more likely to occur in December through June
Symptoms appear about 2 days after exposure to rotavirus
ETIOLOGY
Spread through fecal–oral route
SIGNS AND SYMPTOMS
Fever
Abdominal pain
Nausea and vomiting
Watery diarrhea
DIAGNOSTICS
Clinical diagnosis
TREATMENT
Supportive care
Infants, young children, and the elderly more likely to become dehydrated
Treat with IV fluids for dehydration
BASICS
Many types of E. coli bacteria normally live in the human intestines
Certain types have the ability to cause severe diarrhea
E. coli O157:H7 causes illness by producing a Shiga toxin
ETIOLOGY
Infection occurs primarily through the fecal–oral route or consumption of unclean drinking water
SIGNS AND SYMPTOMS
Low-grade fever
Abdominal pain
Bloody diarrhea
DIAGNOSTICS
Stool studies for Shiga toxin
TREATMENT
Supportive therapy
No antibiotics or antidiarrheal agents as this will increase the risk for hemolytic uremic syndrome (HUS)
BASICS
Bacterial cause of acute diarrhea
ETIOLOGY
Infection occurs through consumption of contaminated meat, poultry, or raw milk
Symptoms can occur 2 to 5 days after exposure to the pathogen
SIGNS AND SYMPTOMS
Fever
Abdominal pain
Nonbloody or bloody diarrhea
Nausea and vomiting
DIAGNOSTICS
Stool studies
TREATMENT
Supportive care
Symptoms can last for 10 days
Ciprofloxacin or azithromycin for immunosuppressed individuals or severe cases
BASICS
Bacterial cause of acute diarrhea
Causes illness 12 to 72 hours after exposure
Illness lasts about 4 to 7 days
Salmonella typhi can lead to bacteremia and typhoid fever
ETIOLOGY
Ingestion of undercooked foods such as chicken or eggs
SIGNS AND SYMPTOMS
Fever
Crampy abdominal pain
Nausea, vomiting
Watery diarrhea
Diarrhea may be bloody
About 30% of people develop reactive arthritis weeks to months after diarrhea resolves
DIAGNOSTICS
Stool studies
TREATMENT
Supportive care
Consider antibiotics (Cipro) for outpatient management
Salmonella bacteremia is treated with ciprofloxacin IV or ceftriaxone IV
BASICS
Shigella dysenteriae is responsible pathogen for worldwide deadly epidemics
Shigella is a gram-negative bacteria similar to E. coli
Symptoms begin 1 to 2 days after exposure to bacteria
Illness lasts 5 to 7 days
ETIOLOGY
Fecal–oral route of transmission
Ingestion of food contaminated by person infected with Shigella
Ingestion of water contaminated by person infected with Shigella
SIGNS AND SYMPTOMS
Fever
Abdominal pain
Bloody diarrhea
Reiter syndrome (arthritis, eye irritation, and painful urination) may occur in some individuals after Shigella infection
DIAGNOSTICS
Stool studies for Shigella
TREATMENT
Supportive care
Antibiotic treatment for severe cases with ciprofloxacin, Bactrim, or azithromycin
Avoid antidiarrheal medications
BASICS
Acute diarrhea caused by Yersinia enterocolitica
Symptoms develop 4 to 7 days after exposure
Illness lasts 1 to 3 weeks
ETIOLOGY
Consumption of undercooked or raw pork products
Drinking unpasteurized milk or contaminated water supplies
Direct person-to-person transmission due to poor hand hygiene
SIGNS AND SYMPTOMS
Fever
Abdominal pain; pain typically in right lower quadrant
Bloody diarrhea
Symptoms can mimic appendicitis
Erythema nodosum can develop after infection and will self-resolve
Around 2% to 3% risk of development of reactive arthritis that occurs after diarrhea resolves and this is also self-limiting
DIAGNOSTICS
Stool studies for Y. enterocolitica
TREATMENT
Supportive care for mild cases
Ciprofloxacin, levofloxacin, or Bactrim for severe cases
BASICS
Microscopic parasite that causes diarrheal infection
Most common intestinal parasitic infection causing human illness in the United States
Symptoms begin 1 to 3 weeks after infection
ETIOLOGY
Primarily causes infection through the ingestion of contaminated drinking water
Often seen in campers who drink from streams and lakes
SIGNS AND SYMPTOMS
Abdominal cramping
Abdominal bloating
Excessive flatulence
Diarrhea
Greasy stools
DIAGNOSTICS
Stool studies to look for Giardia
TREATMENT
Supportive therapy
Metronidazole or tinidazole
BASICS
Ameba that is responsible for GI infection as well as extra intestinal infections
Occurs more often in tropical countries and places with poor sanitation
ETIOLOGY
Ingestion of dormant cysts from fecally contaminated water causes infection
SIGNS AND SYMPTOMS
Stomach cramping
Bloating
Flatulence
Diarrhea with intermittent constipation
DIAGNOSTICS
Stool studies for Entamoeba
TREATMENT
Supportive therapy
Metronidazole plus paromomycin or iodoquinol
BASICS
Parasite that causes acute diarrhea
ETIOLOGY
Ingestion of oocysts from fecally contaminated water
Ingestion of contaminated fruits and vegetables
Illness may take 1 to 2 weeks to appear after ingestion of contaminated water
SIGNS AND SYMPTOMS
Watery diarrhea
Fatigue, weight loss
Abdominal cramping and bloating
Flatulence
Decreased appetite
DIAGNOSTICS
Stool studies to look for Cyclospora
TREATMENT
Supportive care
Bactrim
BASICS
Microscopic parasite responsible for acute diarrheal illness
Symptoms begin about 7 days after infection
Illness lasts 1 to 2 weeks
ETIOLOGY
Illness caused by drinking fecally contaminated water supplies
Can also become infected through contaminated soil or food
SIGNS AND SYMPTOMS
Fever
Abdominal pain
Nausea and vomiting
Diarrhea
DIAGNOSTICS
Stool studies to look for Cryptosporidium
TREATMENT
Supportive care
Nitazoxanide
BASICS
S. aureus is a bacteria commonly found on the skin of individuals
It does not cause GI illness unless the bacteria is ingested
Symptoms begin as quickly as 1 to 6 hours after ingestion of bacteria
ETIOLOGY
Primary route of transmission is through food contamination by food handlers with S. aureus on their hands
Typical foods are unpasteurized milk and cheeses, sliced meats, and pastries
Cooking food will not kill bacteria or toxin and prevent infection
SIGNS AND SYMPTOMS
Abdominal cramping
Nausea and vomiting
Nonbloody diarrhea
DIAGNOSTICS
Clinical diagnosis
TREATMENT
Supportive care
Self-limiting disease
Antibiotics not indicated
BASICS
Bacteria that causes colitis infection, which can be severe and prolonged
Very young and elderly at risk for severe complications
Complications include toxic megacolon, pseudomembranous colitis, and sepsis
ETIOLOGY
Inappropriate or prolonged use of antibiotics can lead to change in gut flora, causing over proliferation of C. difficile
Can be spread through hand contamination via health care workers or individuals with C. difficile infection
SIGNS AND SYMPTOMS
Fever
Abdominal pain
Nausea and vomiting
Watery diarrhea
Weight loss
DIAGNOSTICS
Test for C. difficile toxin
TREATMENT
Supportive care
Metronidazole for mild to moderate disease
Metronidazole IV and vancomycin po for severe complicated disease
HUMAN IMMUNODECIENCY VIRUS (HIV)
BASICS
Blood-borne virus transmitted via semen, vaginal secretions, blood products, or transplacental transmission
ETIOLOGY
Infection with HIV-1 or HIV-2 virus results in immune deficiency by depletion of helper T-cells (CD4)
SIGNS AND SYMPTOMS
Acute seroconversion:
• Flu-like symptoms: fever, malaise, rash, lymphadenopathy
Asymptomatic phase:
• May last for up to 10 years
• When the CD4 count falls to 500, patients more susceptible to opportunistic infections
Symptomatic HIV infection:
• Fever, weight loss, night sweats, malaise
TREATMENT
Multiple regimens of highly active antiretroviral therapy (HAART) available
MANIFESTATIONS
Cutaneous manifestations:
• Multiple skin disorders are associated with HIV
• Kaposi sarcoma:
AIDS defining illness
Manifests as macular, papular, nodular, palpable lesions, sometimes with mucosal, pulmonary, and GI involvement
Brown, pink, red, or violaceous
• Bacterial infections:
Cellulitis, abscess, folliculitis, bullous impetigo
Mycobacterial infections: Mycobacterium avium-intracellulare complex (MAC) infections present as disseminated rash with plaques, pustules, and ulcers
• Syphilis:
Common coinfection with HIV
Primary syphilis presents with painless chancre
Secondary syphilis: disseminated mucocutaneous rash, involving palms and soles
• Viral infections:
Herpes simplex and herpes zoster
EBV: oral hairy leukoplakia
CMV: perineal ulcers
Molluscum contagiosum
Human papillomavirus: condyloma accuminata
• Fungal infections:
Candidal infections common
Neurologic manifestations:
• Toxoplasmosis:
Leading cause of CNS disease in patients with AIDS
Infection by parasite Toxoplasma gondii
Can occur in patients with CD4 <200, but patients <50 at greatest risk
Signs and symptoms:
– Headache, fever, focal neurologic symptoms, AMS
Diagnostics:
– Serum anti-T. gondii IgG/IgM, polymerase chain reaction (PCR) of CSF
– CT/MRI: MRI more sensitive than CT. Single or multiple hypodense lesions that may be ring-enhancing
Treatment:
– Pyrimethamine + folinic acid + sulfadiazine, or intravenous Bactrim
• HIV-associated dementia:
End stages of the disease
Involves decreased cognitive function, memory impairment, decreased inhibition
• Cryptococcus:
Most common fungal CNS infection
AIDS defining illness
Patients with CD4 <100 at risk
Signs and symptoms:
– Headache, fever, malaise, stiff neck, AMS
Diagnostics:
– CT, MRI (better test)
– May see cryptococcal pseudocysts on CT
– MRI may show meningeal enhancement or mass lesion (cryptococcoma)
– CSF: CSF antigen, CSF culture (almost 100% positive)
Treatment:
– Intravenous amphotericin B plus flucytosine for 2 weeks followed by po fluconazole × 2 weeks
• HSV encephalitis:
Mortality is six times higher in immunocompromised patients
Signs and symptoms:
– Fever, headache, vomiting, AMS
Diagnostics:
– CSF viral culture, CSF PCR
Treatment:
– IV acyclovir
– Role of steroids remains unclear
• Tuberculosis meningitis:
Mortality is high
Signs and symptoms:
– Fever, headache, vision change, AMS, focal neuro deficits
– Myelopathy/ascending paralysis in spinal meningitis
Diagnostics:
– Hyponatremia secondary to syndrome of inappropriate secretion of antidiuretic hormone (SIADH) common
– Purified protein derivative (PPD) of limited utility
– CSF with elevated protein
– CT/MRI: may show hydrocephalus, infarcts, edema, and tuberculoma
Treatment:
– Early antibiotics improve mortality
– Isoniazid + rifampin + pyrazinamide
Ophthalmologic manifestations:
• CMV retinitis:
Slowly progressive
Suspect in patients with CD4 <50
• Signs and symptoms:
Floaters, decreased visual acuity
Sclera/conjunctiva noninjected
• Diagnostics
Visual acuity
Dilated slit lamp exam
Exam with “cheese pizza” appearance
Lesions typically peripheral
• Treatment:
Consult ophthalmology and ID
Most important treatment is optimizing HAART
Pulmonary manifestations:
• Pneumocystis jiroveci (formerly phencyclidine):
Most common opportunistic infection in patients with HIV
• Signs and symptoms:
Fever, exertional dyspnea, nonproductive cough, chills, weight loss
• Diagnostics:
Lactate dehydrogenase elevation, serum quantitative PCR, serum β-D-glucan
Sputum induction with inhaled hypertonic saline
Chest x-ray: diffuse bilateral perihilar infiltrates
• Treatment
Bactrim or clindamycin plus primaquine
Consider corticosteroids
• Histoplasmosis:
Fungal infection endemic to Ohio, Mississippi, and Missouri River Valleys
Signs and symptoms
– Cough, fever, myalgia, arthralgia, dyspnea, chest pain
Diagnostics:
– Pancytopenia in acute, progressive disseminated histoplasmosis
– Sputum cultures, blood cultures, antibody titers, serum and urine antigen
– Chest x-ray: can see hilar lymphadenopathy or patchy infiltrates
Treatment:
– Mild cases: oral itraconazole 6 to 12 weeks
– Severe cases: intravenous amphotericin B
– May require surgical resection of pulmonary cavitary lesions if failed medical management
BASICS
Infectious, viral disease, also called the kissing disease
ETIOLOGY
Caused by EBV
Transmitted by saliva
SIGNS AND SYMPTOMS
Fever
Sore throat
Splenomegaly
Lymphadenopathy
Fatigue, malaise
DIAGNOSTICS
Leukocytosis with atypical lymphocytes in the peripheral blood smear
Monospot test showing heterophil antibodies
TREATMENT
Self-limiting
Symptomatic treatment
Avoid contact sports to prevent splenic injuries
ETIOLOGY
Ascaris lumbricoides
Larvae hatch from ingested eggs and migrate to the lungs
More common in children in underdeveloped countries due to exposure to feces
SIGNS AND SYMPTOMS
Fever, cough, shortness of breath, hemoptysis, and eosinophilia
DIAGNOSTICS
Stool studies
TREATMENT
Albendazole or mebendazole as a single dose
ETIOLOGY
Necator Americanus
Prevalent in the Southern United States
Eggs excreted in human feces → become filariform larvae → larvae penetrate skin of humans walking barefoot
SIGNS AND SYMPTOMS
Cough, fever, abdominal pain, weight loss, guaiac positive stools, eosinophilia
Marked by chronic anemia, as the worms feed on blood
DIAGNOSTICS
Stool studies
TREATMENT
Albendazole or mebendazole as a single dose
ETIOLOGY
Enterobius vermicularis, white nematode
Generally a pediatric condition
Eggs hatch within the ileum and colon. Females then migrate to perianal region
SIGNS AND SYMPTOMS
Anal pruritus or mild pain, generally worse at night or early morning
White female pinworms visible on exam of the perianal region
DIAGNOSTICS
Cellophane tape test:
• Apply cellophane tape to the unwashed perianal region in the morning and apply to a slide
Larvae and eggs can be seen on microscopy
Stool for ova and parasites may also be positive for pinworm
TREATMENT
Mebendazole
Treat the entire family, or risk recurrence
ETIOLOGY
Strongyloides stercoralis
More common in the Southeastern United States and Appalachia
Infestation of the small intestine
Parasite penetrates skin (usually through the feet or via fecal–oral contact)
Migrate to lungs via lymphatic system → up the trachea where they are swallowed and enter the GI tract
Immunocompromised hosts can develop disseminated Strongyloides, leading to invasion of all tissues (CNS, heart, urinary tract)
SIGNS AND SYMPTOMS
Causes erythematous rash with petechial hemorrhages (cutaneous larval migrans—very distinct)
Cough, hemoptysis, abdominal pain, weight loss, bloody diarrhea
DIAGNOSTICS
Stool for ova and parasite
TREATMENT
Thiabendazole and ivermectin
ETIOLOGY
Nematodal infection of genus Trichinella
Transmitted by ingestion of infected pork, beef, and walrus meat
Larvae penetrate intestinal wall, enter the lymphatic system, and invade striated muscle cells
SIGNS AND SYMPTOMS
Nausea, vomiting, diarrhea, urticaria, myalgia, periorbital edema, splinter hemorrhages, and headache
Cardioneurologic syndrome: encephalopathy, neurologic deficits, myocardial injury (infarction, myocarditis, congestive heart failure)
DIAGNOSTICS
Labs including complete blood count (CBC) with eosinophilia, creatine kinase, UA for myoglobinuria, parasite specific indirect IgG, muscle biopsy
TREATMENT
Mebendazole and albendazole, which are only helpful during intestinal phase
Prednisone/hydrocortisone for anti-inflammatory effects, decreased immunologic response to larvae
ETIOLOGY
Blood flukes of the genus Schistosoma
Snails act as hosts
More common in Africa, Caribbean, and Middle East
Larvae released by infected snails; penetrates the skin through contact with infected water, resulting in maculopapular rash; invades the venous system
SIGNS AND SYMPTOMS
Acute schistosomiasis (Katayama fever):
• Fever, myalgia, cough, headache
Chronic schistosomiasis
• Intestinal: diarrhea, portal hypertension, and esophageal varices
• Urogenital: dysuria, frequency, hematuria
• Cardiopulmonary: cough, dyspnea, cor pulmonale
• CNS: headache, seizures, transverse myelitis
DIAGNOSTICS
Labs including CBC and basic metabolic panel
Schistosoma may be isolated from urine, blood, and stool
TREATMENT
Praziquantel and corticosteroids for acute schistosomiasis
ETIOLOGY
Trichuris trichiura
Parasite found in rural areas of the United States
Spread by fecal–oral route
Eggs hatch in the small bowel and immature worms migrate to the colon, imbedding half their bodies in the intestinal mucosa
SIGNS AND SYMPTOMS
Anorexia, abdominal pain, diarrhea, fever, weight loss
Colitis and rectal prolapse in children
DIAGNOSTICS
Microcytic hypochromic anemia, stool for O&P
TREATMENT
Mebendazole, albendazole
ETIOLOGY
Taenia solium—pork tapeworm
Central America and Middle East
Ingestion of undercooked pork
Taenia saginata: beef tapeworm
SIGNS AND SYMPTOMS
Abdominal pain, anorexia, nausea, constipation
Most common complication is appendicitis
Larval cysts within the brain may cause seizure, headache, or psychiatric disturbance
DIAGNOSTICS
CBC with eosinophilia. Stool for O&P. Head CT may reveal cysts and granulomata, or edema consistent with dead worms
TREATMENT
Praziquantel, Niclosamide
Decadron in the event of increased ICP
Ocular, ventricular, and spinal lesions may require surgical management
BASICS
Flagellate protozoan G. lamblia
Most common parasitic intestinal infection in the United States
Endemic in regions with poor sanitation
ETIOLOGY
Cysts ingested via contaminated water → develop into trophozoites, which colonize the duodenum and jejunum
SIGNS AND SYMPTOMS
Watery diarrhea, flatus, abdominal cramping, nausea, weight loss
DIAGNOSTICS
Stool antigen testing
TREATMENT
Metronidazole, tinidazole
BASICS
Amebic dysentery
Protozoan E. histolytica
Endemic in developing countries with poor sanitation
ETIOLOGY
Ingestion of cysts from contaminated water/soil/hands from food handlers
Trophozoites inhabit the colon, causing mucosal destruction and ulceration
SIGNS AND SYMPTOMS
Bloody diarrhea, fever, abdominal pain, nausea, anorexia
Complications: liver, lung, brain abscesses, pericarditis, toxic megacolon, ameboma
DIAGNOSTICS
CBC generally without eosinophilia, liver function test elevation
Stool for ova and parasite, culture, and antigen
Serum IgG
Colonoscopy: scraping of ulcers may reveal trophozoites
TREATMENT
Metronidazole
BASICS
Protozoan parasite Trypanosoma cruzi causes Chagas disease
More common in the Southwestern United States and South America
ETIOLOGY
Humans come into contact with feces from infected blood-sucking insects
After entry into the skin, they invade the bloodstream and lymphatics
SIGNS AND SYMPTOMS
Acute phase:
• Chagoma (inflammatory lesion where T. cruzi enters the skin)
• Fever, headache, anorexia, conjunctivitis
• Resolves in 3 to 8 weeks
Chronic phase:
• GI complications: megacolon (abdominal pain and constipation), megaesophagus (dysphagia, chest pain)
• Cardiac: cardiomyopathy, atrioventricular block, thromboembolism
DIAGNOSTICS
Thick and thin smear, enzyme-linked immunosorbent assay
TREATMENT
Benznidazole or nifurtimox for the acute phase
Antiparasitic treatment not given to those with GI and cardiac complications from chronic infection
BASICS
Common, bacterial infection by Vibrio cholerae
Found in developing countries, specifically sub-Saharan Africa
ETIOLOGY
Water-borne, also through fecal–oral spread and person-to-person contact
SIGNS AND SYMPTOMS
Watery diarrhea, vomiting, dehydration
DIAGNOSTICS
Serum PCR, examination of stool under dark field microscopy, stool culture
TREATMENT
Aggressive rehydration and maintenance
Ciprofloxacin, erythromycin, doxycycline, and Bactrim
BASICS
Disease of mammals only
Once symptomatic: nearly 100% mortality
High-risk animals:
• Raccoons, skunks, foxes, coyotes
Assume rabid and always vaccinate
• Bats
Very high risk
Vaccinate for any other bite/scratch/saliva exposure or if patient wakes up with bat in bedroom
Other mammals
• Domestic cats and dogs
Confirm vaccination status of animal
Most are low risk
– Unknown rabies vaccine
– Observe animal for 10 days OR
– Vaccinate after consulting with Department of Public Health (DPH)
• Livestock, small rodents generally low risk
SIGNS AND SYMPTOMS
Similar to the flu including general weakness, fever, headache
Late stages: delirium, abnormal behavior, hallucinations
The acute period of disease typically ends after 2 to 10 days
TREATMENT
If signs of clinical disease: ABCs, supportive, the disease is nearly always fatal
If animal bite and/or exposure:
• Clean wounds
• Vaccinate
Human rabies immune globulin (HRIG) 20 IU per kg on day 0
– Infiltrate full dose around wound if possible
Rabies vaccine 1.0 mL IM days 0, 3, 7, and 14
– Do not inject in same site as HRIG
BASICS
Bacterial sepsis is a clinical term used to describe symptomatic bacteremia, with or without organ dysfunction
Defined as the presence of infection in conjunction with systemic inflammatory response syndrome (SIRS):
• Body temp < 36°C (96.8°F) or > 38°C (100.4°F)
• Heart rate >90
• Tachypnea: respiratory rate >20 or arterial partial pressure of CO2 <32 mm Hg
• Leukocytes <4,000 cells per mm3 or >12,000 cells per mm3, or presence of >10% bands
Patients with diabetes mellitus, systemic lupus erythematosus, ETOH abuse, and chronic steroid use at higher risk
ETIOLOGY
Infectious versus noninfectious
Noninfectious include adrenal insufficiency, pulmonary embolism, aortic aneurysm/dissection, cardiac tamponade, anaphylaxis, drug overdose
DEFINITIONS
Sepsis
• SIRS plus documented infection
• Goals in the ED: early identification of sepsis with early administration of appropriate empiric antimicrobial therapy and surgical intervention are critical
Severe sepsis
• Sepsis-related organ dysfunction or signs of hypoperfusion (lactate >2 mmol/L, oliguria, AMS, hypoxia, elevated liver function tests)
• Hypotension: systolic blood pressure <90 or mean arterial pressure <60
Septic shock
• Severe sepsis with persistent hypotension refractory to fluid bolus
MODS: multiple organ dysfunction syndrome
• More than one major system failure, associated with >50% mortality
DIAGNOSTICS
Laboratory studies, including blood cultures and lactic acid, arterial blood gas/venous blood gas, urinalysis, and culture
Chest x-ray
TREATMENT
ABCs, IV fluids, supportive, transfusion if needed (if hematocrit <30)
Initiate appropriate broad-spectrum antibiotics, goal within 3 hours of arrival in the ED
Blood cultures prior to antibiotics
Early goal-directed therapy
• Antibiotics generally institution specific
• Consider Methicillin-resistant S. aureus, Pseudomonas coverage, especially if recently hospitalized (health care–associated pneumonia—2-day hospital admission in the last 90 days)
If hypotensive, give fluid bolus 20 to 40 mL per kg
If persistently hypotensive despite fluid bolus, initiate vasopressors via central line
BASICS
A serious bacterial infection affecting nervous system
Also called “lock jaw”
ETIOLOGY
Bacteria Clostridium tetani
Found in soil, dust, and animal feces
Bacteria produces a toxin (tetanospasmin) which impairs motor neurons
SIGNS AND SYMPTOMS
Muscle spasms
Difficulty breathing
Fever, hypertension, diaphoresis
DIAGNOSTICS
Clinical exam findings
TREATMENT
ABCs, supportive
Vaccine
• Tetanus vaccine nearly 100% effective after three doses
• Immunity declines after 5 to 10 years, booster recommended every 10 years
• Combined vaccine with diphtheria
• Recommended for all pregnant women (third trimester preferred)
TICK-BORNE AND VECTOR-BORNE ILLNESSES
Tick removal: Grab the head with forceps and gently pull away from the skin
BASICS
Most common tick-borne disease
ETIOLOGY
Spirochete Borrelia burgdorferi
Transmitted by deer tick, genus Ixodes nymph stage
Highest incidence in the Northeast
Tick must be attached >24 hours
SIGNS AND SYMPTOMS
Early localized:
• Erythema chronicus migrans
• Annular (target) lesions
• May include systemic symptoms: fever, chills, headache, malaise
• Symptoms occur 3 to 32 days after tick bite
Early disseminated:
• Longer than 4 weeks
• Neuro: headache, meningitis, facial nerve palsy, radiculoneuropathy
• Cardiac: atrioventricular block, all types
Late:
• Migratory polyoligoarthritis involving large joints (knee, shoulder, elbow), encephalitis
DIAGNOSTICS
Clinical exam findings
Serology: Lyme titer/antibody (not reliable)
CSF studies
TREATMENT
Stage I:
• Doxycycline 100 mg bid for 21 days
• Children and pregnant women: Amoxicillin, penicillin, or erythromycin
Stage II:
• Ceftriaxone 1 g Q12H × 10 to 14 days
Stage III:
• Arthritis treatment doxycycline for 28 days
• Encephalitis requires IV treatment
Posttreatment Lyme disease syndrome:
• 10% to 20% of people previously diagnosed with Lyme develop chronic fatigue, myalgia, and arthralgia
• No evidence that patients who receive prolonged course of antibiotics for this do better than those who receive placebo
ETIOLOGY
Babesia: protozoal parasite that causes a malaria-like syndrome
Same tick vector as Lyme
Coinfection with Lyme is possible
More common in asplenic patients
SIGNS AND SYMPTOMS
Fever, malaise, anorexia, fatigue, headache
Exam: unremarkable, splenomegaly noted in 40% of patients
DIAGNOSTICS
Labs: mild hemolytic anemia
Thick and thin smear
TREATMENT
Healthy patients:
• Clindamycin and quinine po
• Quinine contraindicated in pregnant patients
Immunocompromised or elderly patients:
• IV clindamycin and oral quinine
• Or IV azithromycin and atovaquone
Severe cases:
• Consider exchange transfusion
ETIOLOGY
Ehrlichial anaplasma—gram-negative organism that resemble Rickettsia
SIGNS AND SYMPTOMS
Fever, headache, malaise, rigors, nausea, myalgias, nausea, vomiting
Rash is rare
Hepatosplenomegaly
DIAGNOSTICS
Ehrlichia titer
Coinfection with Rocky Mountain Spotted Fever and babesiosis possible
Hyponatremia found in 40% of patients
TREATMENT
Doxycycline × 10 to 14 days
Rifampin if doxycycline contraindicated
ETIOLOGY
Rickettsia rickettsii
Second most common tick-borne disease, primarily in the North west United States
SIGNS AND SYMPTOMS
Fever, maculopapular rash, eventually petechial
Involves palms and soles, flexor surfaces of wrists and ankles
Also nausea, vomiting, myalgia, HA, encephalitis
Triad: fever, headache, and rash in 55% to 65% of patients
DIAGNOSTICS
Titers often negative
Skin biopsy: immunofluorescent antibody staining very sensitive but less specific
TREATMENT
Doxycycline po for mild cases and IV for moderate-severe disease
Chloramphenicol in children and pregnant patients
ETIOLOGY
Infectious zoonosis caused by aerobic, gram-negative, bacillus F. tularensis
Transmission: tick-borne, mosquitoes, flies
Also from animal bites and exposure to contaminated water and mud
SYMPTOMS
Sudden onset of flu-like symptoms: fever, chills, headache, myalgias, malaise, cough, pharyngitis, abdominal pain
Fever lasts for several days, will cease briefly, then resume
Macular → maculopapular rash → pustular rash
Pulse temperature dissociation: relative bradycardia in the setting of fever (also seen in typhoid fever, dengue fever, avian flu, and Q fever)
DIAGNOSTICS
Labs including tularemia antibody titer
TREATMENT
Streptomycin is drug of choice
Fluoroquinolones can also be used (limited data)
ETIOLOGY
Flavivirus, mosquito-borne
Less than 1% of people infected go on to develop severe illness
SIGNS AND SYMPTOMS
Mild illness: fever, nausea, anorexia, malaise, myalgia, headache
Severe illness: muscle weakness, photophobia, seizures, flaccid paralysis, mental status changes
DIAGNOSTICS
Hyponatremia secondary to SIADH
Serum or CSF West Nile IgM
TREATMENT
Supportive
BASICS
Also called “sleeping sickness”
ETIOLOGY
Zoonotic alphavirus, mosquito-borne
SIGNS AND SYMPTOMS
Headache, nausea, vomiting, confusion, nuchal rigidity, seizures, somnolence, cranial nerve palsies (most commonly VI, VII, and XII), fever, chills, myalgia
DIAGNOSTICS
Hyponatremia due to SIADH, elevated WBC
Serum EEE IgM
Viral culture or PCR of CSF
TREATMENT
Supportive
ETIOLOGY
Zoonotic infection caused by Brucella
Most common zoonotic infection
Brucella melitensis most common and virulent worldwide
Transmission: from animals to humans through ingestion of infected food products or direct contact with affected animal
Most commonly from sheep, goats, pigs, cattle, and dogs
SIGNS AND SYMPTOMS
Fever, chills, arthralgia, sweats, anorexia
Hepatosplenomegaly common on exam
Neuro: meningoencephalitis with MS change, coma, neurologic defects, seizures, or coma
GI: dyspepsia, abdominal pain, hepatic abscess
DIAGNOSTICS
Tube agglutination test (other bacterial illnesses may trigger false positive), serum Brucella IgG or PCR
Isolation of Brucella organism: blood or bone marrow culture
CSF studies
TREATMENT
Mild cases: doxycycline po
Moderate to severe cases: multidrug IV regimens
