Invasive Klebsiella pneumoniae Infections, California, USA

To the Editor: A distinctive form of tissue-invasive community-associated Klebsiella pneumoniae infection, typifi ed by primary liver abscess and bacteremia, has been well known in Asia for 2 decades (1–4). Association of these infections with a hypermu-coviscous phenotype was discovered in 2004 (5). Certain genetic and viru-lence features were elucidated in that and subsequent reports (6). The phenotype, easily detected at the bench by the string test (5), has been associated with a chromosomal gene, the mucoviscosity-associated gene A (magA), and a plasmid gene, the regulator of the mucoid phenotype A gene (rmpA). Usually serotypes K1 and K2 can be demonstrated. Hypermucovis-cous isolates demonstrate increased virulence in mice, are serum insensitive , and resist phagocytosis (5). Reports of such infections from Europe and North America are rare. Recently 2 of us (L.L and B.F.) reported 4 cases in persons seeking care at (7). We report 9 more cases, 7 from Alameda County Medical Center and 2 from St. Rose Hospital in Alameda County. The 13 cases are described in aggregate. Cambodia, and Yemen), but all had emigrated years earlier. Two patients were born in the United States (1 Filipino and 1 African American); the birth site of 1 Filipino was unknown. Five patients had no underlying illness. Seven had diabetes mellitus, 1 had α-thalassemia, 2 had uncontrolled cancer, and 1 had preexisting multiple organ failure. Three patients had gallstones. Case-patients exhibited diverse clinical features. The site of infection was easily detected by dramatically abnormal results of computed tomo-graphic scan or magnetic resonance imaging (Figure). Seven patients had liver abscesses. One of these patients also had cholecystitis and choledo-cholithiasis. One other patient with healthcare-associated bacteremia most likely had multiple small liver abscesses that were superinfected cancer metastases. Two patients had neck abscesses, 1 complicated by extensive descending mediastinitis (Figure). One patient had kidney abscesses complicated by septic and bland pulmonary emboli and numerous brain abscesses detected by magnetic resonance imaging (Figure). Healthcare-associated bacteremia occurred in 3 patients. One patient had sustained bacteremia without a clear source on hospital day 115. Two patients with uncontrolled cancer also had healthcare-associated bacteremia. Venous thrombotic complications occurred in 6 patients, most diagnosed at admission. Two patients had bland pulmonary emboli, and 1 patient with uncontrolled cancer had thrombosis of an upper extremity vein and both femoral veins. Two other patients had septic pulmonary emboli suggested by computed to-mographic scan. One patient with α-thalassemia had kidney …