KPC with ESBL: A multistarrer tragedy

Background: One of the most dangerous carbapenemase is Klebsiella pneumoniae Carbapenemase or KPC, possessing the ability to hydrolyze the Carbapenems, and other beta-lactams as well like Penecillins, Cephalosporins, and aztreonam. Many members of the family Enterobacteriaceae and few other non-fermenters contain the gene blaKPC, which codes for the enzyme KPC, and hence this is transferrable. Although the reports of KPC producers are scanty from India, it is still a dark cloud on the horizon, with the ability to overcast the sky. Our main aim was to identify KPC producing isolates of Klebsiella pneumoniae in our Tertiary care Medical Institution. Materials and Methods: Over a 3 months period, we collected 54 isolates of Klebsiella pneumoniae from different samples. We performed sensitivity against a variety of antibiotics including 3 Carbapenems , 3 extended spectrum Cephalosporins, and co-amoxyclav, both by disc diffusion and E-test against Ertapenem. Results: Out of 54 isolates of Klebsiella pneumoniae, 38 (70.37%) showed resistance towards Ertapenem. Among these 38 isolates, 8 (14.81%) were found to be KPC producers. They were ESBL producers also. Conclusions: Ertapenem resistance is the most sensitive phenotypic marker for detecting KPC. Also, KPC shows resistance to the extended spectrum Cephalosporins. We found 38 isolates showing reduced susceptibility to Ertapenem (by MIC) – thus raising the chance of harbouring the enzyme. Truly, 8 among were confirmed as KPC and ESBL producers. All the microbiology laboratories should routinely search for KPC producers, using Ertapenem as a marker followed by confirmation with the three extended spectrum Cephalosporins.

Keywords: Ertapenem resistance, extended-spectrum cephalosporin resistance, Klebsiella pneumoniae carbapenemase (KPC)

Resistance to broad spectrum antimicrobials, such as the extended-spectrum cephalosporins, is a well-recognized problem among Enterobacteriaceae. ^[1] Carbapenems have served as an important antimicrobial class for the treatment of these organisms and until recently, resistance to carbapenems was unknown among Enterobacteriaceae. However, the emergence of novel β-lactamases with direct carbapenem hydrolyzing activity has contributed to an increased prevalence of carbapenem-resistant Enterobacteriaceae (CRE). ^[2] CRE are particularly problematic, given the frequency with which Enterobacteriaceae cause infections, the high mortality associated with CRE infections, and the potential for widespread dissemination of Carbapenem resistance via mobile genetic elements. ^[3],[4],[5]

One of the most dangerous mechanisms of carbapenem resistance is by a novel enzyme – Klebsiella pneumoniae carbapenemase (KPC). KPC is an enzyme produced by certain bacteria that offer resistance to carbapenem antibiotics and other β-lactam antibiotics. KPC production occurs most commonly in the Enterobacteriaceae family, most commonly in Klebsiella pneumoniae, and also in K.oxytoca, Citrobacter freundii, Enterobacter spp, Escherichia coli, Salmonella spp, and Serratia spp. The non-Enterobacteriaceae members producing this enzyme are Pseudomonas aeruginosa, Pseudomonas putida, and Acinetobacter spp. ^[6]

KPC was first described in 2001 from a clinical isolate in North Carolina, USA. Sporadic occurrences have been reported from several states of USA. KPC-producing organisms contain the gene bla_KPC that codes for production of a plasmid mediated β-lactamase. KPC hydrolyses the carbapenems (ertapenem, meropenem, and imipenem) destroying their activities. Thus, KPC can be considered as a threat due to its ability to render the β-lactam agents, including penicillin, cephalosporins, and aztreonam, ineffective as well. ^[6]

Our main purpose was to outline the sensitivity pattern toward carbapenems shown by Klebsiella as well as to detect the KPC producer, if any, among them in an apex medical institution. There are no new antibiotics at present to combat carbapenem resistance, and worldwide spread of the resistance gene is considered to be a potential nightmare.

Fifty four different specimens of Klebsiella pneumoniae were collected over a 3-month period (June 2013 to August 2013) from samples of patients of all age groups. The samples giving growth of Klebsiella were urine (16 samples), pus (21), pleural fluid (2), sputum (11), debrided tissue (2), bone sequestrum (1), and central venous catheter tip (1). The species identification was done by biochemical testing. All the Klebsiella were subjected to Kirby-Bauer disc diffusion method and also Stokes method for the determination of antibiotic sensitivity pattern following the Clinical and Laboratory Standards Institute (CLSI) guidelines. ^[7] The antibiotics taken were extended-spectrum cephalosporins [i.e., ceftriaxone (30 μg), cefotaxime (30 μg), and ceftazidime (30 μg)], imipenem (10 μg), meropenem (10 μg), ertapenem (10 mcg), amikacin (30 μg), gentamicin (10 μg), ciprofloxacin (5 μg), and levofloxacin (10 μg). Then, the ertapenem-resistant isolates were subjected to ertapenem e-test for determination of minimum inhibitory concentration (MIC) value (EM085 Ertapenem Ezy MIC Strip; Lot No: 0000169502). Double disc approximation test was also carried out with ceftazidime and cefotaxime, keeping co-amoxiclav in the middle to find our extended spectrum beta-lactamase (ESBL) producers as well.

Out of 54 Klebsiella isolates, organisms showing resistance toward ertapenem were 40 (77.78%) by Kirby-Bauer disc diffusion method.

With these 40 ertapenem-resistant isolates, e-test and modified Hodge test were performed. All of these 40 isolates yielded positive results by the modified Hodge test but 38 (70.37%) showed ertapenem resistance by the e-test. Among these 38 isolates, 8 (14.81%) showed resistance to all the 3 extended spectrum cepahalosporins, thus fulfilling the criteria of being a KPC producer.

These very eight isolates were interestingly found to be showing susceptibility to co-amoxiclav. That they were ESBL strains was confirmed by double disc approximation test.

We tested 54 isolates of Klebsiella pneumoniae in this study. Imipenem, meropenem, and ertapenem susceptibility were determined by disc diffusion as well as by e-test (to meropenem and ertapenem). Quality control was performed with Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853. Ertapenem resistance has been found to be most sensitive clinical test for KPC production and is recommended by Centers for Disease Control and Prevention (CDC). ^[8] In two different studies, one involving 33 cases of KPC-producing Enterobacter spp. and the other involving 28 cases of KPC-producing Klebsiella pneumoniae determining the ertapenem MIC identified all the KPC producers correctly as ertapenem-resistant. ^[9] The modified Hodge test, although 100% sensitive for the detection of carbapenemase, is not a specific test to detect KPC production. ^[8] Still, we performed the test. However, we kept two conditions to be fulfilled to be a KPC producer: 1. a reduced susceptibility to ertapenem, preferably by e-test, and 2. resistance to all the three extended-spectrum cephalosporins.

Thirty eight isolates out of 54 showed reduced susceptibility to ertapenem and thus, raised the suspicion of harboring the KPC enzyme. Truly, eight of them were resistant to the entire three extended-spectrum cepahalosporins as well as ertapenem and could thus, be stamped as harboring KPC. Tragically, these eight isolates also met the CLSI ESBL criteria.

KPC-producing bacteria have been found across the world, posing challenges to clinicians. As they are not routinely identified by screening methods and as PCR is still a distant dream in many microbiology laboratories in our country, a way out should be made mandatory so as to routinely detect them and impose the necessary control measures. Clinical microbiology laboratories should be alert of ertapenem resistance as a signature marker for KPC production. Clinicians should, along the same lines, keep in mind that with increasing frequency of KPC producing bacteria, the number of effective antibiotics in hand are also on the wane.

The scenario we found was thus laden with severe consequences since these eight KPC producers were ESBL producers as well, thus taking away from us almost any possible therapeutic avenue.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/1755-6783.168709