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Monday, May 21, 2018

NIPAH VIRUS INFECTION


  • A newly emerging zoonosis 
  • RNA virus of the family Paramyxoviridae, genus Henipavirus, and closely related to Hendra virus.
  • Gets its name from the village in Malaysia where the person from whom the virus was first isolated succumbed to the disease. 
Spread- 
  • Natural host - fruit bats of the Pteropodidae Family, Pteropus genus. (Grey-headed flying foxes - Pteropus poliocephalus)
  • The virus is present in bat urine and potentially, bat faeces, saliva, and birthing fluids. 
  • Transmission may be due to fomites – or carrying the virus on clothing, equipment, boots, vehicles.
Outbreaks- 
  • First outbreak - in Kampung Sungai Nipah, Malaysia, 1998. Intermediate hosts- Pigs. 
  • In 2004, Bangladesh - humans became infected with NiV as a result of consuming date palm sap that had been contaminated by infected fruit bats. 
  • Human-to-human transmission - documented. 
  • Can cause disease in pigs and other domestic animals
Clinical features- 
  • incubation period of 5 to 14 days
  • Presenting symptoms - 3-14 days of fever and headache, followed by drowsiness, disorientation and mental confusion. 
  • Can progress to coma within 24-48 hours.
  • Ranges from asymptomatic infection to acute respiratory syndrome and fatal encephalitis. 
  • Some patients have a respiratory illness during the early part of their infections, and half of the patients showing severe neurological signs showed also pulmonary signs.
  • Long-term sequelae noted -persistent convulsions and personality changes.
  • Latent infections with subsequent reactivation of Nipah virus and death have also been reported months and even years after exposure.
Treatment -
  • No specific treatment 
  • Intensive supportive care 
  • No vaccine 
Ref -
WHO 
CDC 

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Friday, May 18, 2018

Burkholderia

Historically, considered  Pseudomonas  species - previously known as  Pseudomonas  multivorans  and  Pseudomonas  kingie.

  • Aerobic gram-negative bacteria
  • Acquire motility via multitrichous polar flagella.
  • Do not ferment glucose 
  • Many clinical isolates give a weak oxidase reaction. 
  • Slow-growing morphotypes, may go undetected in routine cultures
  • Free-livingorganisms present in most aquatic and humid environment, including hospital drinking water. 
  • nine  genomovars  grouped  under  “B.  cepacia  complex”  (BCC)
  • Burkholderia cenocepacia and Burkholderia multivorans are the prominent bacterial strains isolated from patients with cysticfibrosis.

Infection- 

  1.  Lung - 

  • B. cepacia  gained notoriety as the cause of a rapidly fatal syndrome of respiratory distress and septicemia (the “cepacia syndrome”) in CF patients.
  • B.  cepacia  regarded  as  important  multi-drug resistant  gram-negative  bacteria  in  the  immunosuppressed  cancer  and transplant  populations.
  • Nebulizer-associated  BCC  pneumonia  outbreaks  have  occurred  in patients  with  lymphoid  and  myeloid  neoplasms  receiving  aerosolized antimicrobial  prophylaxis
  • The risk for  nosocomial  BCC  pneumonia  includes  patients  in  a  critical  care  unit for  longer  than  1  week,  those  requiring  assisted  ventilation,  and  those on  broad-spectrum  antimicrobial  therapy. 
  • Hospital  fomites  and  ventilator  humidification  system  may be  potential  sources

      2. Skin,  Skin  Structure,  and  Joint  Infection - 

  • Risk  factors - patients receiving  care  in  burn  units  and  those  in  critical  care  units  exposed  to contaminated  disinfectants  or  unsterilized  skin  moisturizing  products.
  • Hematogenous  B.  cepacia  dissemination  may  present  as ecthyma  gangrenosum–like  skin  lesions,  particularly  in  patients  with underlying  cancer  or  other  immunosuppression.
  • B.  cepacia  septic  arthritis  via  hematogenous  seeding  is  serious,  although  a  rare  complication.

      3. Genitourinary  Tract  Infection - 

  • Iatrogenic  infection  from  manipulation  of  the  genitourinary  tract  such as  with  transrectal  prostate  biopsy  and  a  cystoscopy-related  intramural bladder  wall  B.  cepacia  abscess  have  been  rarely  observed.
  • In  critical  care  units,  nosocomial  B.  cepacia  genitourinary  tract  infection arises  from  prior  colonization  of  a  urinary  catheter.

Diagnosis-

  • Antibiotic-containing  media  can  be  used  to  promote  selective  growth (e.g.,  Pseudomonas  cepacia  agar,  oxidation-fermentation  polymyxin bacitracin  lactose  agar,  and  B.  cepacia  selective  agar).  These  culture media  containing  gentamicin,  polymyxin  B,  and  vancomycin  can  be used  to  isolate  over  90%  of  BCC  within  48  to  72  hours.
  • Upto 36% of Burkholderia speciesmay be misidentified by automated systems as other nonfermentativebbacteria,such as Achromobacter or Ralstonia.

Resistance patterns - 

  • Drug-resistance  pathways  include  efflux  pumps  (including  adenosine triphosphate–binding  cassette  transporters),  antimicrobial  degradation  and/or  modifying  enzymes,  and  altered  membrane  function.

Rx- 

  • Monotherapy not recommended as high chances of failure and infection relapse
  • Carbapenems, TMP/SMX, chloramphenicol, and tetracycline
  • Susceptible to minocycline(38%), meropenem(26%), and ceftazidime(23%).
  • Ceftazidime, tobramycin, and ciprofloxacin retain antimicrobial activity against planktonic and biofilm-embedded organisms.
  • Tigecycline  is  less  effective  compared  with  minocycline,  and  overexpression  of  efflux  pumps  may  result  in  development  of  de  novo  drug resistance.
  • Combination therapy for serious pulmonary infection (e.g., in CF) is suggested when multidrug-resistant strains are implicated. 
  • The combination  of  meropenem  and TMP-SMX  may be antagonistic, however. 

Ref-

Mandell - Principles and practice of Infectious Diseases , 8th edition 


Harrison’s Principles of Internal Medicine, 19th edition 

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