The mechanisms of antibiotic resistance in major pathogens of purulent-inflammatory complications in cancer patients

Abstract

The problem of microbial antibiotic resistance and investigation of its underlying mechanisms is of paramount importance for all fields of clinical medicine, including oncology. The aim of the study was to examine the mechanisms of antibiotic resistance for major pathogens causing purulent-inflammatory complications in cancer patients. Materials and methods. In 2012—2015 there was conducted a prospective examination of 184 cancer patients, including 67 patients at the Department of Surgery no. 1 and 117 patients at the Intensive Care Unit of the Krasnoyarsk Regional Clinical Oncology Center named after A.I. Kryzhanovsky. For this, we collected bronchoalveolar lavage fluid, wound discharge and investigated the material by using bacteriological method, as well as MALDI-TOF. Antibiotic sensitivity was studied as follows: disco-diffusion, double disc method, carbapenem inactivation method, staphylococcal sensitivity — by screening method, PCR, E-test method, and serial dilutions in Muller-Hinton broth. Genotyping and antibiotic resistance mechanisms study were performed by using PCR, M-PCR, and sequencing. The WHONET program (WHO) was used, with significance level set at p < 0.05. Results. Microbiological examination of bronchoalveolar lavage fluid and wound discharge samples allowed to uncover prevalent associations of multi-resistant (MDR) and extremely resistant pathogens (XDR). The microflora of the lower respiratory tract and in the wound secretion in cancer patients were found to be dominated by non-fermenting Gram-negative bacteria reaching up to 44.5% and 48%, respectively; as well as order Enterobacteriales found in 24% and 34.9%, respectively; Gram-positive bacteria — 24% and 17.1%, respectively. Imipenem- and/or meropenem-resistant P. aeruginosa and A. baumannii, K. pneumoniae strains, were assessed for MBL production phenotypically, as well as the genes of the most common VIM, IMP types, whereas A. baumannii — for OXA-23, OXA-40, and OXA-58; and K. pneumoniae — for OXA-48. 20 strains and 16 strains of P. aeruginosa and A. baumannii, respectively, were studied by PCR. It was found that A. baumannii strains formed no MBL, but 56.3% of A. baumannii isolates (9 strains) produced OXA-23 and OXA-40 carbapenemases. Among P. aeruginosa strains there were three of them which possessed VIM (15.0%), whereas the remaining strains formed no MBL, but were resistant to carbapenems being associated with other resistance mechanisms, e.g. efflux, decreased permeability of cell wall etc. Among 6 isolates of K. pneumoniae, 1 strain produced OXA-48. In cancer patients, the percentage of methicillin-resistant strains among all members of the genus Staphylococcus was 48.9% (4 strains belonged to MRSA). PVL- MRSA strains belonged to the clones ST239/spa3(t037)/SCCmecIIIA/tst,sek,seq+ (75%) and ST8/ spa1(t008)/SCCmecIVc/sea+ (25%). MRSA ST239 showed multiple antibiotic resistance: to aminoglycosides (aacA-aphD, aadD genes were detected), linkcosamides/macrolides (the ermA gene was detected), fluoroquinolones (mutations in the GyrA gene — Ser84Leu; in GrlA- Ser80Phe), rifampicin (MIC more than 128 gg/ml; mutations in the rpoB gene are His481Asn, Ile527Met), sulfamethoxazole, tetracycline (tetM gene), and chloramphenicol (66.7% of isolates, the cat gene encoding chloramphenicol acetyl transferase was detected); but sensitive to vancomycin (MIC 1.0 gg/ ml), linezolid in 100% of cases. MRSA ST8 are resistant to aminoglycosides (aacA-aphD, aadD genes), lincosamides/macrolides (ermC gene), tetracyclines (tetK gene), chloramphenicol (cat gene); and 100% sensitive to fluoroquinolones, rifampicin (MIC 0.006 gg/ml), sulfamethaxazole, vancomycin (MIC 1.0 gg/ml), daptomycin (MIC 0.094 gg/ml), linezolid (MIC 0.75 gg/ml). Conclusion. Thus, it was found that members of the order Enterobacteriales, A. baumannii, P. aeruginosa and MRSA retain high resistance to a large number of antibacterial drugs of almost all classes. These data should be taken into account while choosing proper antibiotic therapy, as well as controlling spread of nosocomial infections caused by multiresistant microorganisms.