Richard presented a patient from China with a history of diabetes not on medications who presents to the hospital with 4 days of lip swelling. He had a pimple just inferior to his nostrils, which he popped the day prior to onset of symptoms. He was feeling fine and he initially thought it was an allergic reaction after his lips became swollen and pruritic. His vitals were normal, but notable upper lip swelling and surrounding erythema were noted. Ultimately he underwent I&D after CT revealed gas within the soft tissues consistent with a necrotizing soft tissue infection. Cultures turned out to be hypermucoid klebsiella!

Risk Factors for necrotizing soft tissue infection

• Diabetes
• Chronic disease
• Immunosuppressive drugs (eg, prednisolone)
• Malnutrition
• Age > 60 years
• IVDU
• Peripheral vascular disease
• Renal failure
• Underlying malignancy
• Obesity
• Precipitating events (both traumatic and non-traumatic)
  • Traumatic: Surgery, procedures, acupuncture, IVDU, penetrating injuries
  • Non-traumatic: Soft tissue infection, childbirth

Presentation

• Pt in general are acutely ill.
• Most cases involve the limbs, perineum, or trunk. Head & neck involvement are only seen in 5% of cases

Organisms

• Type A Nec Fas: Most common, polymicrobial
• Type B Nec Fas: Less common, monomicrobial
• In general, the organisms involved in nec fas are:
  • Strep (group A) & staph (most common
  • Anaerobes
  • Gram negatives i.e. pseudmonas
  • Enterococcus
  • Vibrio vulnificus (especially in patients with cirrhotic with sea water exposure!!!)
  • Clostridium perfringens
  • Candida spp

How about hypermucoid klebsiella? A single center study in Taiwan in 2012 found that klebsiella accounted for 17% of monomicrobial nec fas, with 2/3 of them being the hypermucoid variant. In Asian countries, HvKP necrotizing infection is as common as those caused by staph and strep.

In North America though? The first case report of community acquired HvKP associated  was reported in 2015. See this article for details.

Hypermucoid variant Klebsiella (HvKP)

Epidemiology

• Usually community acquired, highly virulence strain of KP that is typically pan-sensitive.
• Primarily in SE and E Asian countries but seeing this strain increasingly in the US.
• From a necrotizing soft tissue infection stand point, it has been reported in SE Asia beginning in 1996. Most info published in the literature are case reports,
• KP itself, in a single center study done in Taiwan 2012 found that KP in general accounted for 17% of monomicrobial nec fas, and 2/3 of these cases are HvKP. vs 22% staph vs 18% strep.
  • Associated with higher mortality
  • Main risk factors are baseline immunocompromised status, and 80% of pts with HvKP had DM

Risk factor

• Primary risk factor seems to be just diabetes! But this can affect completely healthy patients in the community.

Presentation

• Pyogenic liver abscess
• Metastatic infection, likes to travel and stick to places.
• Associated infections
  • Primary liver abscess, usually in the right lobe for some reason
    • HvKP is the culprit organism in 9-12% in pts with primary liver abscesses
  • Splenic abscess, SBP, PNA, soft tissue infection, osteo, UTI
  • Associated endophthalmitis especially if bacteremic or presence of abscess in up to 50% of pts
    • Not so much if pulmonary or urine

Diagnosis

• String Test! > 5mm = diagnostic.
• 
• Capsular subtypes: some are more virulent, K1, K2, rmpAvirulence-associated gene

Management

• Fortunately, most are pan-sensitive
• Penicillin or cephalosporins = main stay, but if treating for a liver abscess, should cover for anaerobes as well.
• Surgical drainage if e/o abscess
• If concerned for metastatic infection, combination of surgical and medical therapy depending on location of the infection