Abstract
In Klebsiella pneumoniae liver abscess (KP-LA), K. pneumoniae K2 is the most frequently isolated serotype after K1, but this serotype has been much less studied. In the present study, the molecular types sequences type (MLST) of serotype K2 isolates from three different regions in Asia were identified and the virulence of these isolates was investigated. Eight different MLSTs were found among 26 isolates (ST 65, 66, 86, 373, 374, 375, 380, and 434). There were two major MLST groups, ST-65-like (42%) and ST86-like (46%). No isolates contained allS while all isolates contained rmpA. The prevalence of aerobactin gene and kfu were 25/26 (96%) and 3/26 (11.5%) respectively. Although liver abscess isolates were generally more resistant (11/15 isolates) to serum killing, there was no specific distribution of serum killing resistant or susceptible ST types between stool carriage and liver abscess isolates. Neutrophil phagocytosis showed that the liver abscess and carriage isolates varied in their susceptibility to phagocytosis. Strains with resistance to both neutrophil phagocytosis and serum killing were generally hypervirulent with lethality at LD50 < 103 colony forming units by intraperitoneal injection. In conclusion, Anti-phagocytosis and resistance to serum killing are two parameters that most predict hyperviurlence in serotype K2 isolates. Unlike serotype K1 KP-LA that mainly belong to ST-23, ST-65-like and −86-like are the two major MLST types among serotype K2 isolates from Singapore, Hong Kong and Taiwan.
Highlights
Klebsiella pneumoniae liver abscess (KP-LA) has becoming a global emerging disease [1,2]
Bacterial strains K. pneumoniae strains that were isolated from liver abscess and stool from healthy subjects, hospitalized patients without history of liver abscess or patients admitted with noninfectious diseases were collected at Prince of Wales hospital in Hong Kong, Singapore General Hospital, National University hospital in Singapore and Tri-Service General Hospital in Taiwan from 2002 to 2009
molecular types sequences type (MLST) profiles of isolates from Hong Kong, Singapore and Taiwan A total of 26 serotype K2 isolates were confirmed by serotyping and PCR and selected for this study
Summary
Klebsiella pneumoniae liver abscess (KP-LA) has becoming a global emerging disease [1,2]. We determined the molecular types (MLST) of K. pneumoniae serotype K2 isolates from liver abscesses and from carriers without a history of KP-LA and assessed the virulence of isolates with different MLST types from Hong Kong, Singapore, and Taiwan. To determine the number of viable bacteria after exposure to serum, an aliquot of each bacterial suspension was removed at the designated time point, diluted 10-fold by addition of MuellerHinton broth, plated on Mueller-Hinton agar, and assayed as described immediately below.
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