Emergence of carbapenem resistant hypervirulent K.pneumoniae – a global threat?

Background:

There has been increasing reports of hypervirulent (hv) K.pneumoniae (Kp) from various parts of the world. Most studies till date reported these strains to be community acquired and susceptible to most antimicrobials. However, two recent reports from China describe carbapenem resistant hvKp. String test is the phenotypic test for hvKp while rmpA, rmpA2 and magA are molecular markers. The present study describes the prevalence of hv strains among the susceptible, ESBL and carbapenem resistant (CR) isolates. 

Methods:

The first 76 non-repetitive K.pneumoniae blood cultures obtained during 2015 were included in the study. For screening of hv strains, string test was performed. The three most important genes associated with hypervirulence such as rmpA, rmpA2 and magA were screened for by PCR. Isolates were classified into three groups based on antimicrobial susceptibility testing performed by disk diffusion. First group included isolates that were susceptible to first and second line antimicrobials. Second group comprised of ESBL producers and third group comprised of carbapenem resistant isolates. Clinical details of patients were obtained from electronic medical records.

Results: Table 1 shows results for string test, antimicrobial susceptibility and genes for hvKp. Among 76 isolates included, 30% (23) were string test positive. 9 were positive for rmpA and 17 for rmpA2 and 7 were positive for both rmpA and rmpA2. 14/17 (82%) of rmpA2 positives were health care associated infections. 8/17 (47%) were carbapenem resistant.

Conclusion:

String is not very specific and molecular markers are more reliable in identifying the hv strains. In this study only 18% of hvKp infections were community acquired which reflects on spread of these strains within the hospital posing a threat to treatment and management of infections. There has been an increase in incidence of hvKp among CR isolates.The hv strains are no longer restricted to susceptible phenotypes.

Table1: Characteristics of the K.pneumoniae isolates

Total n=76	String test positive	String test negative	rmpA	rmpA2	magA	Community acquired	Health care associated
Susceptible (n=28)	10	18	6	7	4	7	21
ESBL (n=18)	2	16	2	2	0	3	15
Carbapenem resistant (n=30)	11	19	1	8	0	0	30