Abstract
BackgroundThe heteroresistance of polymyxin B, a last-resort antibiotic used to treat many serious bacterial infections, may lead to antibiotic treatment failure. However, polymyxin B-heteroresistant isolates are rare in individuals living in the community. We report a polymyxin B-heteroresistant hypervirulent Klebsiella pneumoniae (hvKP) isolate from an individual in the community with asymptomatic bacteriuria.ResultsThe NYTJ35 isolate had multiple virulence genes that encoded a mucoid phenotype regulator (rmpA), aerobactin (iucABCD-iutA), salmochelin (iroBCDN), yersiniabactin (irp1–2 and ybtAEPQSTUX), and a truncated rmpA2. Infection of galleria mellonella larvae indicated the isolate was hypervirulent. Antimicrobial susceptibility testing showed it was susceptible to all tested antibiotics except polymyxin B. The proportion of surviving bacteria was 1.2 × 10− 7 based on the population analysis profile (PAP) method, suggesting the presence of polymyxin B heteroresistance. The isolate was not hypermucoviscous, but it was a strong biofilm producer. It had capsular serotype K1 and belonged to sequence type 23 (ST23). The isolate also had the D150G substitution in phoQ, which is known to confer polymyxin B resistance.ConclusionsWe identified the co-occurrence of hypervirulence and polymyxin B heteroresistance in a K. pneumoniae isolate from an individual with asymptomatic bacteriuria. We suggest the use of increased screening for hvKP in individuals living in the community.
Highlights
The heteroresistance of polymyxin B, a last-resort antibiotic used to treat many serious bacterial infections, may lead to antibiotic treatment failure
Characteristics and identification of the hypervirulent Klebsiella pneumoniae (hvKP) isolate During routine mass screening for kidney disease, we found a K. pneumoniae isolate (NYTJ35) in the urine sample of an asymptomatic male individual who was 34 years-old and living in the community
Antimicrobial susceptibility and gene resistance testing The antimicrobial susceptibility tests (Table 1) showed that NYTJ35 was sensitive to all tested antibiotics, including ceftazidime (CAZ), cefepime (FEP), imipenem
Summary
The heteroresistance of polymyxin B, a last-resort antibiotic used to treat many serious bacterial infections, may lead to antibiotic treatment failure. Polymyxin B-heteroresistant isolates are rare in individuals living in the community. We report a polymyxin B-heteroresistant hypervirulent Klebsiella pneumoniae (hvKP) isolate from an individual in the community with asymptomatic bacteriuria. Earlier studies reported that hvKP was susceptible to all antimicrobials with the exception of ampicillin, to which K. pneumoniae has intrinsic resistance. Polymyxin B was regarded as the last-resort antibiotic for the treatment of serious infections by multidrug resistant (MDR) Gram-negative bacteria. Several recent reports described nosocomial infections by polymyxin B-resistant hvKP [13, 14]. The cooccurrence of hypervirulence and MDR in K. pneumoniae is a significant clinical challenge
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