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Medycyna Doświadczalna i Mikrobiologia 2019, 71(2-4): 89-95

Oporność na imipenem wśród beztlenowych pałeczek Bacteroides sp. i Parabacteroides sp. izolowanych od pacjentów hospitalizowanych w Klinikach Szpitala Klinicznego Dzieciątka Jezus w Warszawie
[Resistance to imipenem among anaerobic bacilli of the genus Bacteroides and Parabacteroides isolated from patients hospitalized in clinics of The Infant Jesus Teaching Hospital in Warsaw]

M. Paśnik, M. Kierzkowska, A. Majewska, A. Sawicka-Grzelak, A. Młynarczyk, G. Młynarczyk

Streszczenie
Gatunki rodzajów Bacteroides i Parabacteroides posiadają największą liczbę determinant oporności na antybiotyki spośród bakterii beztlenowych.
Istotne jest oznaczanie lekowrażliwości i zastosowanie terapii celowanej w przypadku zakażeń mikroflorą beztlenową. Spektrum przeciwbakteryjne beztlenowych pałeczek Gram-ujemnych obejmuje: klindamycynę, metronidazol, karbapenemy, β-laktamy w połączeniu z inhibitorami β-laktamaz, czy też chloramfenikol. Niepokojący staje się fakt narastania oporności na karbapenemy.

ABSTRACT
Introduction: The aim of this study was to estimate prevalence of carbapenem-resistant strains among Gram-negative obligate anaerobic bacilli Bacteroides sp. and P. distasonis, as well as the frequency of their isolation from samples of different clinical materials from patients hospitalized in clinics of The Infant Jesus Teaching Hospital in Warsaw, and the presence of genes and insertion sequences responsible for exhibiting phenotypic resistance to carbapenems.
Materials and Methods: In the study, 57 bacterial isolates including 54 isolates of Bacteroides fragilis group and 3 strains of P. distasonis, were analyzed. The strains were isolated from 47 samples of clinical materials from 41 patients hospitalized in The Infant Jesus Teaching Hospital in Warsaw, in 2017. Identification of strains confirmed by MALDI-TOF MS (bioMérieux ® S.A, France). The MIC values of imipenem were detected by E-test (bioMérieux® S.A, France). The bacterial DNA was extracted using a commercial column set Genomic Mini (A&A Biotechnology, Poland). Amplification of cfiA genes and insertion sequences (IS942, IS1186, IS1187, IS1188) fragments were performed by polymerase chain reaction with using Thermal Cycler C-1000 (BioRad, USA). After amplification, agarose gel electrophoresis was performed. The PCR products were visualized with using Imager Gel DocTM XR+ (BioRad, USA).
Results: Among all tested isolates, the prevalence of strains from Bacteroides fragilis group was 94.7%, while the P. distasonis strains was 5.3%. 8 species of anaerobic bacilli were identified within the bacteria of genus Bacteroides. Most frequently isolated species were: B. fragilis (31.6%), B. thetaiotaomicron (29.8%) and B. vulgatus (14.0%).
The strains were isolated from 47 samples of clinical materials. These were swabs from wounds/abscesses (n = 36), fluids from the peritoneal cavity (n = 16) and the others, in less quantity. The rate of resistance to imipenem was 5.26%. Furthermore, 3.51% strains were intermediate to imipenem. The cfiA gene was detected only in B. stercoris strain (1.8%; 1).
However, this strain was sensitive to imipenem (MIC = 0.75 mg/L). Insertion sequences weren’t detected among cfiA-positive strain.
Conclusions: The most frequently isolated anaerobic Gram-negative bacilli from samples taken from patients was B. fragilis. The clinical samples were the most common from Department of General and Transplant Surgery. This study show how important is monitoring of anaerobic infections. The cfiA-positive strain was detected which may indicate the possibility the transmission of resistance determinants. The rate of transfer of resistance patterns between different, phylogenetically distant species of anaerobic bacteria is very high. Also, the use of an increasing number of antibiotics contributes to the development of resistance. Furthermore, genetic factors and environmental conditions favor the emergence of multidrug resistant strains that generate therapeutic problems with failure of treatment.

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