[Investigation of Virulence Genes and Carbapenem Resistance Genes in Hypervirulent and Classical Isolates of Klebsiella pneumoniae Isolated from Various Clinical Specimens]

Klebsiella pneumoniae is a global pathogen that can cause hospital-acquired and community-acquired infections and is known for its resistance to antibiotics. The pathotype, which is defined as hypervirulent K.pneumoniae (hvKp) is more lethal than classical K.pneumoniae (cKp) isolates and causes many community-acquired infections such as liver abscess, endophthalmitis, pneumonia in healthy young adults. There are no clear clinical or microbiological criteria to define hvKp. String test showing hypermucoviscosity and the iucA gene encoding aerobactin, a siderophore, were used to demonstrate hypervirulence. In this study, it was aimed to investigate the presence of various virulence genes and carbapenem resistance genes in the isolates of K.pneumoniae isolated from various clinical samples in our laboratory and classified as classical and hypervirulent by string test and also to detect the presence of various virulence and carbapenem resistance genes in hvKp isolates. Presence of four virulence genes (fimH-1, rmpA, magA, iucA), K1-K2 serotypes in all isolates and five carbapenem resistance genes (blaOXA-48, blaKPC, blaIMP, blaVIM, blaNDM-1) in carbapenem resistant isolates were investigated with polymerase chain reaction (PCR) method. Forty-five percent of the isolates were defined as hvKp and 55% as cKp. The fimH-1 gene was found to be positive in 94% of the isolates, the iucA gene in 37%, the magA gene (K1) in 34%, the rmpA gene in 5%, and the K2 serotype in 3% of the isolates. iucA gene was positive in 68.9% of hvKp isolates and 10.9% of cKp isolates, and the presence of iucA gene in hvKp isolates was statistically significant compared to cKp isolates (p<0.05). magA gene and K1 serotype were detected in 28.9% of hvKp isolates and 38.2% of cKp isolates. Although the magA gene ratio was high in cKp isolates, this difference was not statistically significant (p> 0.05). fimH-1 gene was found positive in 93.3% of hvKp isolates and 94.5% of cKp isolates. The rmpA gene was positive in 8.9% of hvKp isolates and 1.8% of cKp isolates. The K2 serotype was positive in 4.4% of hvKp isolates and 1.8% of cKp isolates. Although there was no statistical difference in antibiotic susceptibility between hvKp and cKp isolates; ceftriaxone, cefuroxime, ceftazidime, amikacin, cefoxitin, ertapenem, cefuroxime axetil were found to be more sensitive in hvKp isolates. Ciprofloxacin and trimethoprim sulfamethoxazole were found to be more sensitive in hvKp isolates than cKp isolates, and the difference was statistically significant (p<0.05). Although gentamicin, amoxicillin, piperacillintazobactam were not statistically significant in the cKp group, they were more sensitive than the hvKp group (p> 0.05). Carbapenem resistance were found to be 65.7% in cKp and 34.3% in hvKp isolates. Although not statistically significant, hvKp isolates were found to be more sensitive to carbapenems. The most common gene among 35 carbapenem resistant isolates was blaOXA-48 detected in 29 isolates. While the blaKPC gene was detected in five isolates, blaIMP, blaVIM and blaNDM-1 were not detected in any isolates. Sixty nine percent of blaOXA-48 positive samples were found to be in cKp isolates and 31% in hvKp isolates. It was determined that all of the blaKPC positive isolates were hvKp isolates. It was concluded that the string test and virulence factors alone would not be sufficient to show hypervirulence, and that more than one virulence factor combination should be shown in the presence of clinical features of hypervirulent infections to show hypervirulence.

Antimicrobial Activity of Garlic Derivatives on Common Causative Microorganisms of the External Ear Canal and Chronic Middle Ear Infections

Objective

Today, antibiotic resistance is increasing and evolving into an important health problem. Therefore, it is important to research on alternative therapies to antibiotics. This study aimed to investigate the inhibitory effect of four garlic derivatives on microorganisms commonly isolated in ear infections.

Methods

The antimicrobial activities of allicin, s-allyl cysteine (SAC), diallyl disulfide (DADS), and s-allyl mercaptocysteine (SAMC) were investigated on standard strains of commonly isolated microorganisms using the broth microdilution method. The test strains were selected among the microorganisms responsible for chronic suppurative otitis media and otitis externa. These microorganisms were Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii, Staphylococcus aureus, Enterococcus faecium, Candida albicans, and Candida tropicalis.

Results

Minimum inhibitory concentration (MIC) values of allicin and SAC ranged from 0.125 to 20 μg/mL for fermentative bacteria (E. coli and K. pneumoniae), 20 to 80 μg/mL for non-fermentative bacteria (P. aeruginosa and A. baumannii), 5 to 10 μg/mL for gram-positive cocci (S. aureus and E. faecium), and 40 to 80 μg/mL for yeasts (C. albicans and C. tropicalis). MIC values of DADS ranged from 40 to 80 μg/mL for fermentative bacteria, 40 to 160 μg/mL for non-fermentative bacteria, 40 to 80 μg/mL for gram-positive cocci, and 20 to 40 μg/mL for yeasts. The MICs of SAMC were >640 μg/mL for the tested bacteria and yeasts.

Conclusion

Both allicin and SAC showed antimicrobial activity against the tested microorganisms, even at low concentrations. These two derivatives may be used to treat infections in the future.