Micro Block 5

Bacillus anthracis


  • Gram (+) rods
  • Produce endospores- allow for survival in adverse conditions
  • Aerobic
  • Capsule
    • Minor virulence factor
    • Composed of polypeptides (D-glutamic acid)
    • Anti-phagocytic
    • Inhibits completment fixation
  • Extotoxins-each protein is non-toxic but are toxic in combination
    • Edema factor( EF)- calmodulin depedent adenylate cyclase → ↑ cAMP
      • Causes extreme edema
      • Inhibits functional activity of phagocytic cell (lethargic)
    • Lethal Factor (LF)- protease that cleaves MAP kinase and disrupts signal transduction
      • Triggers apoptosis of many cell types including phagocytic cells
    • Protective Antigen (PA)- Binds to host cell surfaces, facilitates entry of EF and LF
    • EF + PA = Edema
    • LF + PA = Cell Death
  • Found in soil with large amplification through animal infections
  • Transmission through direct contact with spores or contaminated animal products or with sick animals.  Transmission via inhalation of dust containing anthrax spores
  • Biological warfare
    • Mass anthrax vaccination of all active duty and selected reserve members of the military

Clinical Manifestations of

Bacillus anthracis

Cutaneous Anthrax

  • Most common form (95% of infections)
  • Skin lesion at site of entry or spores into a cut or scrape
  • Small painless papule develops into a enlarging black eschar
  • Edema in the surrounding tissue
  • Usually found on hands, forearms, head
  • Low fatality because of localized infection and antibiotic therapy after daignosis

Pulmonary anthrax (woolsorter’s disease)

  • Symptoms begin 1-40 days after exposure
  • Initial symptoms are non-specific and may include sore throat, mild fever, myalgia, coughing, and chest discomfort
    • Lasting a few days
  • Second stage develops abruptly
    • Sudden onset of fever
    • Acute Respiratory distress
    • Pulmonary Edema
    • Pleural effusion
    • Cyanosis
    • Shock
    • Coma
    • Meningitis
    • Mortality with treatment approaches 90%

Pulmonary anthrax Disease Pathogenesis

  • Inhalation of spores
  • Spores that enter the alveoli are phagocytosed by alveolar macrophages with germination
    • Spores that land on the mucosal surface or the respiratory tract remain inert but still infectious
  • Alveolar macrophages begin to migrate to the draining mediastinal lymph nodes
  • Inside the macrophages the spores/bacteria are processed into a phagolysome but lyse the membrane and enter the cytoplasm
  • Intracellular replication kills and lyses the macrophages
  • The released bacteria now replicate as extracellular pathogens with their full armament of capsule and exotoxins
  • Extracullular replication locally
  • Spread into the bloodstream
  • Massive local inflammation (mediastinitis)- appears as widened mediastimum. Massive edema
  • Fluid accumulation in the lungs, and repiratory failure
  • Bloodstream invasion leads to septic shock and meningitis
  • Capsule prevents phagocytosis and toxins kill and inactive phagocytes.;

Bacillus anthracis


  • Appropriate Sample-Skin biopsy, fluid, blood, CSF
  • Gram Stain- aerobic, spore forming Gm (+) rod
  • Culture-biosafety level 3 lab- easy to grow, typical colonies. Non-hemolytic
  • Inhalation Treatment: IV ciprofloxin, levofloxin, doxycycline, + rifampin or clindamycin
  • Cutaneous Treatment: Oral cipro or levo (used for prophylaxis also)
  • ABthrax (raxibacumab)- mAb against anthrax PA
    • 2009
    • Submitted for FDA approval not yet approved
    • US strategic National Stockpile
  • Vaccine
    • Licensed by FDA in 1970
    • Trade name: BioThrax
    • Purified PA from culture filtrate of an avirulent non-encapsulated strain known as V770-NP1-R
    • Five Doses (0, 4 weeks, 6 months, 12 months, 18 months) plus annual booster thereafter
    • Used by military
    • Thought to be assocaited with Gulf War Syndrome



Bacillus cereus

  • Gm (+) rods
  • Form endospores
  • Aerobic
  • Hemolytic
  • Strains produce one or other or neither enterotoxins
    • Heat stable entertoxin- vomiting
    • Heat labile entertoxin- diarrhea
  • Found in soil
  • Transmission via contamination of food with airborne spores
    • Germination of spores in fried rice
    • Production of entertoxin in food
    • Infegestion of bacteria + toxin
  • Emetic form-nausea and vomiting- incubation period 2-4 hours (ingested toxin)
  • Diarrheal form- diarrhea and abdominal cramps-incubation period of 10-18 hr (bacterial growth);
    • Enterotoxin production in intestines
  • Can also infect eye, IV catheters, CNS shunts, and can cause pneumonia and bacteremia in welders

General Properties of Neisseria

  • Gm (-) diplococci
  • Obligate parasites of the respiratory and genital tracts of humans
  • Obligate aerobes-do not ferment carbohydrates
  • Catalase(+)
  • Oxidase (+)
  • Sensitive to environmental conditions
  • Chocolate agar with increased CO2

Neisseria meningitidis

  • Gm (-) diplococci
  • LPS-endotoxin bu no O antigen
  • Pili-minor virulence factor
  • Capsule-antiphagocytic, manjot virulence factor, major surface antigen
    • 13 Serogroups
    • A
    • B-poorly immunogenic-not present in vaccinations
    • C
    • Y and W 135
  • IgA protease- prtects against IgA on mucosal surfaces
  • No exotoxins
  • Found on the mucosal surfaces of humans (URT)
  • Carrier state-asymptomatic
    • Important in transmission
  • Person to person transmission via respiratory droplets, shared secretions
  • Most susceptible
    • 6-24 months
    • College students
    • Military recruits
  • 10-15% death rate even with antibiotics
  • 11-19% will lose their arms, legs become deaf, have problems with their nervous systems, become mentally retarded or suffer seizures, strokes
    • Significent mobidity and mortality
  • Local Infection
    • Typical URT or asymptomatic
    • Rare pneumonia with serogroup Y
    • May not progress and can becoem carrier
  • Meningococcemia
    • Spread to bloodstream via draining lymphatics resulting in sepsis
    • Endotoxin shock, DIC (causes loss of tissue and amputations)
    • Waterhouse-Friderichsen syndrome- hemorrhaging of the adrenal gland
  • Meningitis
    • May spread from blood to meninges
    • Can occur without prior sepsis
    • 80% fatal if untreated
    • 10-15% fatal with treatment
    • Permanent CNS damage
    • Possible necrosis or large areas of skin and tissue
  • Always consider this organism when a pateint goes from relative health to near deaht in 24 hrs


Neisseria Meningitis


  • Gm stain of CSF
    • Gm(-) diplococci, neutrophils
    • Often shows nothing early in disease and must repeat
  • Antigen detection in CSF-latex agglutination kids-not sensitive
  • Cluture-blood/CSF
    • Chocolate agar, 37 C, CO2
  • Oxidase (+)
  • Treat with Penicillin G (IV) or ceftriaxone
    • Kills on bacteria no effect on toxins
  • Supportive therapy for septic shock and DIC
    • Xigris-activated protein C
      • pulled from market
      • Treatment of DIC
    • Steroids
  • Menomune (MPSV 4)
    • Old vaccine
    • Still recommended for persons ; 55
    • Purified capsule polysaccharide (A,C,Y,W135)
    • Not recommended for children under 2 (poor response)
    • Serogroup B not effective in vaccine
  • Menactra (MCV 4)
    • conjugate vaccine
    • New vaccine
    • Purified capsular polysaccharide (A, C, Y, W 135) conjugated to protein
    • Capsule conjugated to diptheria toxoid
    • In 2005 approved from immunization for 11-12 yrs
    • Catch up for college students
    • April 2011 FDA approved use in infants- two dose schedule 9 months and 23 months
    • Serogroup B not in vaccine
  • Chemoprophylaxis-house hold or other close contacts
      • ciprofloxacin or rifampin
      • NOT penicillin

Viral Meningits

General Characteristics

  • Much more common than bacterial meningitis
  • Less severe than bacterail meningitis-not life threatening
  • Viral diagnosis allows termination of IV antibiotics
  • Non-polio enteroviruses are the major cause of meningitis
    • Summer/Fall peak incidence
  • HSV is the main cause of “sporadic, necrotizing encephalitis”
    • Morbidity and mortality can be reduced by prompt anti-viral therapy


Viral Meningitis

  • aseptic meningitis
  • Inflammation of the meninges covering the brain and spinal cord
  • Symptoms: Fever, Headache, nuchal rigidity (stiff neck), vomiting, and photophobia
  • Typically self limited, non-fatal even in absence of antiviral therapy
  • Major cause are non-polio enteroviruses (echo, coxsackie A and B, entero serotypes)
  • Cells: 10-500
  • Neutrohils early, lymphocytes late in infection
  • Normal Glucose
  • CSF/Serum glucose: ; 0.6
  • Protein ; 100 (mild elevation)
  • Normal to mildly elevated opening pressure

Viral Encephalitis

  • Inflammation of the brain
  • Symptoms: Fever, Headache, Confusion, Altered Consciousness, seizures, and coma in severe cases
  • Higher morbidity and mortality than viral meningitis
  • HSV 1, HSV 2, Rabies (100% fatal), and encephalitis arboviruses (mosquito borne)


Viral Meningoencephalitis

  • CNS symptoms that are a overlap of meningitis and encephalitis symptoms
  • Viruses that are common causes of meningitis are also rare causes of encephalitis
    • Mumps- winter/spring (pre-vaccine era)
  • Many viruses which cause encephalitis can also cause less-severe meningitis syndrome
    • Arbovirus
    • HSV 2-with recurrent genital herpes

Viral Encephalopathy

  • Brain infection without significant inflammation
  • PML syndrome with JC polyomavirus
    • Rare syndrome in children with influenza virus infection and associated with hyperactivated cytokine response rather than viral invasion of the brain.
  • Non-viral spongiform encephalopathies with prions

Viral Myelitis

Inflammation of spinal cord



Viral Encephalomyelitis

Inflammation of brain and spinal cord



Post-infectious syndrome with measles virus

Post-infectious encephalitis or encephalomyelitis

  • Rare occurrance ~ 1 week after acute infection with presumed immune mechanism being autoimmunity
  • Post-infectious with measles
  • Post-vaccinial encephalitis from smallpox vaccine

Necrotizing encephalitis
Acute syndrome associated with herpes simplex viruses
Non-polio Enteroviruses and aseptic/viral meningitis

  • Major cause of viral meningitis in the United States including multiple serotypes of echo, coxsackie A and B, or enterovirus 71
  • Highly contagious viruses with fecal-oral route as major route of transmission
  • Wide spectrum of localized and systemic infections with rare cases of encephalitis
  • Summer/Fall peak incidence
  • No specific antiviral therapy
  • Generally self-limited
  • Rare cases of encephalitis
  • Life-long aquired immunity to specific enteroviral serotype

Mumps and CNS disease in pre-vaccine era

  • Winter/Spring peak
  • Live attenuated vaccine Dec 1967
    • First dose at 12-15 months with a boster at 4-6 years
  • 10-40% of cases had symptoms of meningitis
  • Major problem in the UK and continental Europe bc of lack of immunization.; Those non-immunized US residents traveling to UK are at a significant risk

HSV: Encephalitis/Meningitis

  • “Sporadic”- no seasonal peaks
  • “Necrotizing”-Destructive nature in the brain, especially focal effects in the temporal lobe
  • Travel via retrograde sensory neuronal transport, traveling from the ganglia in primary or reactived form.
  • HSV 1 ; HSV 2
  • Bimodal: 30% ; 20 yrs, 50% ; 50 yrs
  • Perinatal/neonatal herpes encephalitis is mainly due to HSV-2 and primary genital infection of mother late in pregnancy
  • Prompt intravenous acyclovir can reduce morbidity and mortality

Encephalitic Arbovirus

  • West Nile Virus has a summer/fall peak incidence
    • Major arboviral cause in US
  • St. Louis Encehalitis virus has a sumer/fall peak incidence
  • Other important arboviral causes of human neuroinvasive disease in the US include California serogroup/La Crosse bunyavirus, St. Louis encephalitis, flavivirus, Eastern and Western Equine virus and tick born Powassan flavivirus (rare neuroinvasive)
  • Japanese encephalitis virus is the major global cause of arboviral encephalitis in humans with most of the cases in Asia
    • Inactivated vaccine for US residents traveling to Endemic or Epidemic areas

Complications of small pox vaccine (live naturally attenuated vaccinia virus)

  • Post-vaccinial encephalitis-a syndrome which may have an autoimmune mechanism
  • Prompt therapy of vaccinia complications include cidofovir (a nucleotide analogue licensed for cytomegalovirus) and vaccina immune globuline (VIG)

“Slow Viral” Diseases of CNS caused by Authentic Agents

  • 100% fatal
  • Subacute sclerosing panencephalitis (SSPE): Onset several years after acute measles and associated with rare persistance of mutated measles viral nucleocapsid in CNS
  • Progressice multifocal leukoencephalopathy (PML): Reactivated JC polyoma virus in severly immunocompromised persons, with increased incidence due to AIDS and recent rare cases presumably associated with some immunosupressice humanized monoclonal antibody used as therapy for atoimmune diseases

Creutzfeldt-Jakob Disease (CJD)

  • Transmissible spongiform encephalopathies caused by prions
  • 100% fatal
  • Agent: Cellular protein which is pathogenic in misfolded form (PrPsc) and induces similar misfolding of additional normal copies of the protein (PrPC) in the brain in a chain reaction like process
  • ;”Sc”-scrapie
  • Scrapie- disease name in sheep
  • Can occur spontaneously ~1 case per million population;in those ; 50
  • Kuru is human prion disease which was assocaited with ritualistic cannibalism in Fore tribe in New Guinea
  • iatrogenic CJD (iCJD): results from unintended transfer of prion-containing neurological tissues; (dura mater transplants) or pituitary derived growth hormone peparations from donorswho died of unrecognized CJD
  • varient CJD (vCJD): Exposure to bovine spongiform encephalopathy (BSE) agent in food, with brain and spinal cord of ffected cattle having highest concentration of BSE prion
    • Vast majority of cases in UK
    • Occurs at a younger age than sporadic CJD
  • Rare genetic form of human disease are assocaited with mutant forms of prion gene which encode prion protein that can more easily misfold into pathogenic protein, with different mutant protein genes causing distinct fatal pathologies
    • Gertsmann-Straussler-sceinker
    • Fatal Familia insominia
    • Famial CJD

Viral Hemorrhagic Fever
Characterized by petechial exanthem (pinpoint hemorrhages) and massive bruising with severe cases involving shock and potential death
Characteristics of human arenaviruses

  • Virons in electron microscopy;look like sand due tonon-specific packaging of ribosome along with two segments of RNA genome
  • arena=sand this is where the name came from
  • Rodent reservoirs with persistent asymptomatic infection and shedding of virons in urine and saliva

Lymphocytic Choriomenigitis Virus (LCM)

  • Arena viruses in US
  • Viral hemorrhagic fever
  • Mice and per rodents
  • Can result in meningitis or meningoencephalitis
    • ; 1 % mortality in immunocompetent
  • Iatrogenic infections in immunocompromised organ transplant recipients
    • 1 survivor reported with treatment of ribavirin and reduction of immunosupressive drugs

Lassa Virus

  • Hemorrhagic Fever with or without hepatitis and or deafness
  • West Africa
  • Rodent reservoir-multimammate mouse
  • High morbidity and mortality in pregnant females in 3rd trimester
  • Some human to human transmission via blood
  • Intravenous ribavirin therapy can be benificial

Lujo arena virus

  • Discovered in South Africa in association with 5 human cases 4 of which were fatal
  • Ribavirin was given to surviror
  • Fever, headache; diarrhea, myalgia, rash, and hepatic dysfunction
  • Bleeding is not a major feature


Junin Virus

  • Hemorrhagic Fever
  • Argentine-South America
  • Agricultural areas

Machupo Virus

  • Bolivian Hemorrhagic Fever
  • Boliva-South America
  • Infection rate increased when the rodent population increased due to a reduction of cats.; Cats ate geckos, geckos had accumulated DDT that was used to control mosquitos
  • Outbreak ended with rodent control and reduced exposure of humans
  • Sporadic outbreaks still occur

General Properties of Hunavirus

  • Bunyavirdae family
  • Lipid-enveloped
  • 3 segments of (-) ssRNA in helical nucleopsids
  • Rodents as natural hosts and reservoirs
  • Humans are infected by inhalation of aerosolized rodent excretions (urine or salivia) or by direct contact with infected animals
  • No clear human to human transmission with exception of Andes virus in South America
  • Genus name derived from Hantaan virus from Korea
    • Cause of Hemorrhagic fever with renal syndrome (HFRS)
  • Puumala hantavirus from red bank vole in Finland associated with milder HFRS-like syndrome in infected humans known as nephropathia epidemica

Sin Nombre Virus

  • Hantavirus genus
  • Hantavirus pulmonary Syndrome (HPS) in US 1993-present
  • IgM or IgG capture ELISA of patient serum
  • RT-PCR of postmortum lung tissue
  • Antiviral antibody for immunohistochemistry of lung tissue
  • Deer mouse shown to be natural host for Sin Nombre
    • Found in Central and Western US


Filovirdae Family

  • Ebola and Marburg are in this family
    • Hemorrhagic Fever
  • Filamentous apprearance
  • Lipid-enveloped with (-)ssRNA in helical nucleocapsid


Marburg Virus

  • Filoviridae family
  • Discovered during outbreak in Marburg Germany in 1967 associated wtih lab personal working with Monkeys imported from Africa
    • 25 infected humans with 28% fatality rate
    • No fatality rate in 6 cases involving secondary human to human transmission
  • Transmission from infected non-human primates
  • Human to human transmission is via blood and blood contaminated fluids and tissue
  • Fruit eating bats in Africa seem to be natural host
  • Hemorrhage fever

Ebola Virus

  • Filoviridae family
  • West Africia
  • Outbreaks of hemorrhagic fever in West-Central Africia
  • High fatality rate
  • Transmission from infected and diseased non-human primates
  • Human to human transmission via blood and blood contaminated fluids and tissue
  • No natural host for any of the Ebola virus
  • Hot Zone book and Outbreak movie based on 1995 Ebola outbreak in Kitwik

Ebola-Reston Virus

  • Filoviridae family
  • Discovered near Washington DC in Reston VA in sick monkeys which were imported from the Philippines but is non-pathogenic to humans


Categories: Microbiology