Paradoxical effect of Klebsiella pneumoniae OmpK36 porin deficiency

Molecular insights of Carbapenem resistance Klebsiella pneumoniae isolates with focus on multidrug resistance from clinical samples

BACKGROUND

Carbapenem are the last-line antibiotic, defence against Gram-negative extended spectrum ß-lactamases producers (ESBLs). Carbapenem resistance Enterobacteriaceae especially Carbapenem resistant-Klebsiella pneumoniae (CR-KP) is recognized as one of the well-known public health problem, which is increasingly being reported around the world. The present study was focused to analyse the prevalence and characterization of antibiotic resistance K. pneumoniae in centre region of Tamil Nadu, India.

METHODOLOGY

Totally 145 suspected K. pneumoniae isolates [Urine, Pus, Sputum, Blood and Biopsy] obtained from hospitals of Central South India. The isolates were subjected to biochemical and molecular identification technique, following with antibiotic resistance pattern by standard antibiotic sensitivity test. Multidrug resistance (MDR) with β-lactamase producing Carbapenem resistant K. pneumoniae (CR-KP) strains were screened by classical sensitivity method and also drug resistance encoded gene. Also, molecular typing of the MDR strains were characterized by Pulsed-Field Gel Electrophoresis (PFGE). Further, the outer membrane protein (OmpK35 and 36) related Carbapenem resistance were characterized.

RESULTS

Totally, 61% of isolates were confirmed as K. pneumoniae, 75 % of isolates were MDR including 58% carbapenem and 97% ESBL antibiotics and grouped into 17 distinct resistant patterns. The MDR KP isolates shows positive for blaCTXM-1 (92 %) gene followed by blaSHV (43 %), blaTEM (36 %), blaNDM-1 (26 %), blaGES (20 %) and blaIMP-1 (8 %). Moreover, 62 % CR-KP isolates loses OmpK36 and 33% isolates loses OmpK35.

CONCLUSIONS

Loss of OmpK36 were highly an influence the cefoxitin and carbapenem resistance. Sixteen different PFGE patterns have been observed among the 18 MDR isolates. Eventually, ESBL as well as CR-KP were diverse in genetic makeup and often associated with hyper virulence hvKP should be of serious concern.

Rapid identification of pathogens using molecular techniques

Real-time PCR is the traditional face of nucleic acid detection in the diagnostic microbiology laboratory and is now generally regarded as robust enough to be widely adopted. Methods based on nucleic acid detection of this type are bringing increased accuracy to diagnosis in areas where culture is difficult and/or expensive, and these methods are often effective partners to other rapid molecular diagnostic tools such as matrix-assisted laser desorption ionisation-time of flight mass spectrometry (MALDI-TOF MS). This change in practice has particularly affected the recognition of viruses and fastidious or antibiotic-exposed bacteria, but has been also shown to be effective in the recognition of troublesome or specialised phenotypes such as antiviral resistance and transmissible antibiotic resistance in the Enterobacteriaceae. Quantitation and high-intensity sequencing (of multiple whole genomes) has brought new opportunities as well as new challenges to the microbiology community. Diagnostic microbiologists currently training might be expected to deal less with the culture-based techniques of the last half-century than with the high-volume data and complex analyses of the next.

Contribution of β-lactamases and porin proteins OmpK35 and OmpK36 to carbapenem resistance in clinical isolates of KPC-2-producing Klebsiella pneumoniae

Fifty-seven carbapenem-resistant Klebsiella pneumoniae isolates belonging to ST11 (50 isolates), ST423 (5 isolates), and two other sequence types were studied. All were positive for blaKPC-2, blaTEM-1, and blaCTX-M-14. SDS-PAGE analysis of six representative isolates demonstrated varied porin expression. Nevertheless, when blaKPC-2 was deleted, carbapenem resistance was markedly reduced. Additionally, SHV-12, DHA-1, and/or VIM-1 appeared to contribute to accessory carbapenemase activity. In contrast, OmpK35 and/or OmpK36 deficiency seemed to serve only as a minor cooperative factor.

Carbapenem and cefoxitin resistance of Klebsiella pneumoniae strains associated with porin OmpK36 loss and DHA-1 β-lactamase production

Clinical isolates of carbapenem-resistant Klebsiella pneumoniae (K. pneumoniae) strains are being increased worldwide. Five pan-resistant K. pneumoniae strains have been isolated from respiratory and ICU wards in a Chinese hospital, and reveal strong resistance to all β-lactams, fluoroquinolones and aminoglycosides. Totally 27 β-lactamase genes and 2 membrane pore protein (porin) genes in 5 K. pneumoniae strains were screened by polymerase chain reaction (PCR). The results indicated that all of 5 K. pneumoniae strains carried blaTEM-1 and blaDHA-1 genes, as well as base deletion and mutation of OmpK35 or OmpK36 genes. Compared with carbapenem-sensitive isolates by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), the resistant isolates markedly lacked the protein band of 34-40 kDa, which might be the outer membrane proteins of OmpK36 according to the electrophoresis mobility. In addition, the conjugation test was confirmed that blaDHA-1 mediated by plasmids could be transferred between resistant and sensitive strains. When reserpine (30 μg/mL) and carbonyl cyanide m-chlorophenylhydrazone (CCCP) (50 μg/mL) were added in imipenem and meropenem, the MICs had no change against K. pneumoniae strains. These results suggest that both DHA-1 β-lactamase and loss or deficiency of porin OmpK36 may be the main reason for the cefoxitin and carbapenem resistance in K. pneumoniae strains in our hospital.

Characterization of multidrug-resistant Klebsiella pneumoniae from Australia carrying blaNDM-1

blaNDM genes, encoding metallo-β-lactamases providing resistance to carbapenems, have been reported in many locations since the initial report in 2008, including in several Enterobacteriaceae isolates in Australia/New Zealand. Here, we compare 4 additional carbapenem-resistant Klebsiella pneumoniae carrying blaNDM-1 isolated in Australia. Two are sequence type ST147, previously associated with blaNDM in Australia and elsewhere. They carry blaNDM-1 and different 16S rRNA methylase genes (armA or rmtC) on different conjugative plasmids, in 1 case with an IncFIIY replicon. One isolate belongs to the globally important ST11 but did not transfer a plasmid to Escherichia coli. The fourth isolate belongs to the novel ST1068 and transferred blaNDM-1, armA, and an IncA/C plasmid. Amplification and sequencing of ompK porin genes suggest that, unlike the case for other carbapenemase genes, ompK36 defects may not be required for NDM to cause clinically relevant levels of carbapenem resistance.

Different culture medium formulations induce variant protein expression patterns of outer membrane porins in Klebsiella pneumoniae

Outer membrane porin (OMP) expression has been shown to play an important role in antimicrobial resistance. In this study, we observed that OmpK35 of Klebsiella pneumoniae had varied expression profiles in different nutrient broths. the potential factors that could influence protein expression were assessed. K. pneumoniae (ATCC 13883) was cultured into two commercial available nutrient broths and also into solutions of the individual ingredients. To ensure that OmpK35 was detected, an OmpK35 deficient mutant was generated as control. When OmpK protein expression profiles were analyzed by SDS-PAGE, OmpK35 exhibited two different isoforms. Expression of an additional isoform-like OmpK35 protein was identified in one of the broths. No OmpK35 isoforms were observed when the individual ingredients of beef extract, casein or gelatin were used as culture medium. OmpK35 isoform expression could be repressed by adding more beef extract. In summary, OmpK can exhibit varied protein expression profiles when growing in different nutrient broths. The isoform-like protein expression of OmpK35 may lead to confusion in OmpK protein analysis.

Klebsiella pneumoniae outer membrane porins OmpK35 and OmpK36 play roles in both antimicrobial resistance and virulence

OmpK35 and OmpK36 are the major outer membrane porins of Klebsiella pneumoniae. In this study, a virulent clinical isolate was selected to study the role of these two porins in antimicrobial resistance and virulence. The single deletion of ompK36 (ΔompK36) resulted in MIC shifts of cefazolin, cephalothin, and cefoxitin from susceptible to resistant, while the single deletion of ompK35 (ΔompK35) had no significant effect. A double deletion of ompK35 and ompK36 (ΔompK35/36) further increased these MICs to high-level resistance and led to 8- and 16-fold increases in the MICs of meropenem and cefepime, respectively. In contrast to the routine testing medium, which is of high osmolarity, susceptibility tests using low-osmolarity medium showed that the ΔompK35 mutation resulted in a significant (≥ 4-fold) increase in the MICs of cefazolin and ceftazidime, whereas a ΔompK36 deletion conferred a significantly (4-fold) lower increase in the MIC of cefazolin. In the virulence assays, a significant (P < 0.05) defect in the growth rate was found only in the ΔompK35/36 mutant, indicating the effect on metabolic fitness. A significant (P < 0.05) increase in susceptibility to neutrophil phagocytosis was observed in both ΔompK36 and ΔompK35/36 mutants. In a mouse peritonitis model, the ΔompK35 mutant showed no change in virulence, and the ΔompK36 mutant exhibited significantly (P < 0.01) lower virulence, whereas the ΔompK35/36 mutant presented the highest 50% lethal dose of these strains. In conclusion, porin deficiency in K. pneumoniae could increase antimicrobial resistance but decrease virulence at the same time.