Acta microbiologica et immunologica Hungarica最新文献

Acinetobacter baumannii is a significant nosocomial pathogen recognized for its multidrug-resistance (MDR) and capacity to endure in hospital settings. This study aims to investigate the clonal relationships of A. baumannii isolates from diverse clinical samples, identify the sequence types of MDR isolates, and examine biofilm formation activity and biofilm-associated genes that contribute to persistence in hospital settings. A total of 90 A. baumannii isolates were analyzed. Bacterial identification and antibiotic susceptibility testing were conducted with MALDI-TOF MS and Vitek-2. REP-PCR was utilized to evaluate clonal connections, MLST was employed for specific isolates. Biofilm formation activity was assessed using the XTT reduction assay, and biofilm-associated genes were identified by PCR. REP-PCR revealed 29 genotypes, with Genotype A being identified as the endemic clone in 59% of isolates. Two isolates representing this genotype were found to belong to the ST2 clone. The majority of A. baumannii isolates possess biofilm-related genes and exhibit strong biofilm activity. In MDR isolates, ompA and csuE positivity were significantly higher than those non-MDR isolates (P = 0.003, P = 0.001). The csuE positive isolates were found to have significantly stronger biofilm activity than negative ones (P = 0.009). This study emphasizes the prevalence of a hospital-endemic, MDR A. baumannii genotype A, ST2 clone, and the genetic variability across isolates. No direct correlation was noted between MDR status and biofilm formation; however, some biofilm-related genes, notably csuE, were linked to stronger biofilm activity. These findings underscore the necessity for ongoing molecular surveillance and infection control measures to avert the dissemination of MDR A. baumannii in healthcare environments.

Infections caused by colistin resistant Klebsiella pneumoniae are a major global health challenge linked to high mortality rates worldwide. Increased incidence of hypervirulent and drug-resistant Klebsiella causing life-threatening infections in young healthy individuals and asymptomatic carriage in the community has been largely reported in the Asian-Pacific Rim. This study conducted a molecular analysis of two morphologically distinct variants of K. pneumoniae that caused bacteremia and sepsis in a patient. Colony morphology of the isolates was characterized in various growth media, and the morphological variants differed in their mucoviscosity. The isolates were found to be serotype K2 (highly associated with hypervirulent Klebsiella) by molecular serotyping using specific PCR primers. The multidrug-resistant nature of the colony variants was evaluated by antibiotic susceptibility testing and it was found to have a similar antibiogram pattern in in vitro. An increased minimum inhibitory concentration (MIC) of colistin (>64 μg mL-1) was detected in both isolates using broth microdilution, and they were found to be highly resistant to colistin. Molecular analysis revealed that the isolates possessed a chromosomal mutation in mgrB, which causes colistin resistance. The increased incidence of infection caused by colistin-resistant K. pneumoniae requires continuous monitoring, and appropriate measures are necessary to control its adaptive evolution in healthcare settings.

In this study, we evaluated the performance of modified rapid antimicrobial susceptibility test (mRAST) with 150 mm Mueller Hinton Agar (MHA) plates which was earlier standardized for 90 mm MHA by EUCAST. Blood culture bottles spiked with ATCC quality control strains were prepared. For quality control Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 29213, and Enterococcus faecalis ATCC 29212 strains were used. By calculating and proportioning the surface areas of the plates comparing with 90 mm plates, 350 ± 50 µL undiluted blood culture samples were inoculated in 150 mm MHA, and 12 disks were placed. This process was repeated independently for three days and three times on each day for reproducibility. The mRAST test was performed on 50 samples with positive signals and gram-negative bacilli on Gram-stained samples (20 Klebsiella pneumoniae, 15 E. coli, 10 Acinetobacter baumannii, and five P. aeruginosa).Comparison of 90 mm MHA and 150 mm MHA showed that the categorical agreement of ATCC strains and 50 gram negative isolates was 100% and >95%, respectively, for all antibiotics. For K. pneumoniae, only 0.4 major error (ME) was detected at 4 h. For E. coli, 3.2, 1.6, and 1.5 ME were detected at 4, 8, and 20 h, respectively, whereas 1.6 very major error (VME) was detected at 4 h and 1.0 VME was detected at both 8, and 20 h, respectively. No errors were detected for P. aeruginosa or A. baumannii.These results indicated that 350 ± 50 µL of undiluted blood culture in 150 mm MHA was suitable for the mRAST test in vitro.

Often dismissed as contaminants in blood cultures, Corynebacterium species can also cause infective endocarditis, a severe condition. We report an unusual case of Corynebacterium propinquum endocarditis in a non-immunocompromised individual on a native valve. Conflicting clinical and microbiological data led to 16S ribosomal sequencing to confirm the causative agent. Our case illustrates C. propinquum as a cause of infective endocarditis, and it demonstrates the utility of ancillary molecular diagnostic techniques to identify etiologic agents in difficult cases of infective endocarditis. C. propinquum should be recognized as a potential cause of infective endocarditis even on a native valve.

There is a plethora of evidence that suggests infection may either directly or indirectly trigger chronic inflammatory processes which may then act as a risk factor for diabetes mellitus and atherosclerosis. Inflammatory periodontal disease like periodontitis, is among the most prevalent oral infectious disease. It affects the tissues that support the teeth and has reportedly been linked to systemic conditions like diabetes mellitus and atherosclerosis. The onset and progression of periodontitis is significantly influenced by the plaque-biofilm and the host-inflammatory response to it. Evidence from numerous studies included in this review supports the hypothesis that there is an association between periodontal pathogens and systemic conditions like diabetes mellitus and atherosclerosis. An overview of some of the periodontal pathogens associated with periodontitis and the proposed mechanisms by which these pathogens can evade and invade the human defence system triggering the onset of chronic diseases like diabetes mellitus and atherosclerosis are presented in this article.

The aim of the study was to detect carbapenemase genes in clinically significant carbapenemase-producing Enterobacterales (CPE) and assess their susceptibility to newer antibiotics: ceftazidime-avibactam, ceftolozane-tazobactam, imipenem/relebactam, meropenem-vaborbactam, and cefiderocol. From January 2018 to February 2019, 866 Gram-negative bacilli were isolated, and among them 775 were identified as Enterobacterales. Out of the tested Enterobacterales, phenotypic testing revealed potential carbapenemase production in 95 isolates. A total of 56 clinically significant isolates were selected for molecular analysis. Species identification and antimicrobial susceptibility for conventional antibiotics was done using the VITEK 2 system, while carbapenemase genes were detected via Multiplex PCR. Antimicrobial susceptibility for newer antibiotics was determined by the MIC test strips. The predominant genotypes were blaNDM (39.3%) and blaOXA-48 (37.5%), with Klebsiella pneumoniae as the most prevalent producer (71.42%). Cefiderocol showed 100% effectiveness against all isolates. Ceftazidime-avibactam demonstrated high activity against OXA-48 and KPC producers (95.5% and 100% susceptibility, respectively). Meropenem-vaborbactam significantly improved susceptibility among NDM-. OXA-48/NDM-, and OXA-48-producing isolates, and imipenem-relebactam among OXA-48 CPE. Statistically significant differences in susceptibility were observed for OXA-48 and NDM producers to imipenem (P < 0.01), imipenem-relebactam (P < 0.001), and ceftazidime-avibactam (P < 0.001). In conclusion, the high prevalence of NDM-producing CPE strains significantly reduces the effectiveness of newer antibiotics. Cefiderocol appears to be the most effective therapeutic option, particularly for NDM producers, where it often represents the only viable treatment choice, while ceftazidime-avibactam is an effective option for OXA-48 producers. Statistically significant differences in susceptibility highlight the need for early detection of carbapenemases in clinical practice.

This study aimed the identification of anaerobic bacteria isolated from blood cultures and the determination of antibacterial susceptibility of the isolates. The study material comprised of 5,282 blood samples taken between 2018 and 2020. The samples were incubated in a BacT/ALERT system. The species identification of the isolates was performed by three methods namely, BBL Crystal Anaerobe system, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), and 16S rRNA gene sequence analysis. Antibacterial susceptibility testing was performed using the disk diffusion method with benzylpenicillin, clindamycin, piperacillin-tazobactam, meropenem, and metronidazole disks. In the BacT/ALERT system, 45 anaerobic bacterial isolates were recovered from 39 (0.74%) of the samples that showed growth signs in blood culture bottles. The BBL Crystal Anaerobe system and 16S rRNA gene sequence analyses enabled the genus and species identification of all 45 isolates (100%), whereas with MALDI-TOF MS, only 37 (82.2%) of the isolates were able to be identified. Antibacterial resistance rates of the isolates to piperacillin/tazobactam, clindamycin, benzylpenicillin, meropenem, and metronidazole were detected as 100%, 73.8%, 40%, 9.8%, and 5.5%, respectively. MALDI-TOF MS showed a higher level of compatibility with 16S rRNA gene sequence analyses, compared to the BBL Crystal Anaerobe system. The high rates of susceptibility to meropenem and metronidazole suggested that these antibiotics are options for the empirical treatment of anaerobic bacterial infections.

The study was conducted in the microbiology laboratory of the First Affiliated Hospital of Hainan Medical University, Haikou, China, from January 2019 to December 2023. A total of 316 consecutive non-duplicate isolates were collected and identified, that belonged to the Bacteroides fragilis group. Identification of the isolated strains was performed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). The minimum inhibitory concentration (MIC) of seven antibiotics was determined by agar dilution method. The presence of cfiA, ermF, and nim genes was determined by polymerase chain reaction (PCR). Correlations between the presence of resistance genes and the MIC values of antibiotics were determined using the Pearson correlation coefficient. In the identification process, 214 isolates (67.7%) were identified as B. fragilis, 52 (16.4%) as Bacteroides thetaiotaomicron, 17 (5.4%) as Bacteroides ovatus, 12 (3.8%) as Bacteroides uniformis, 10 (3.2%) as Phocaeicola vulgatus (=Bacteroides vulgatus), 7 (2.2%) as Bacteroides stercoris, and 4 (1.3%) as Parabacteroides distasonis. The presence of cfiA gene moderately correlated with the MIC of imipenem and meropenem (r = 0.34 and r = 0.42, respectively), while resistance to clindamycin and the presence of ermF gene exhibited a very strong correlation (r = 0.72). In the current study, the most active antimicrobial agents against B. fragilis group bacteria were found to be meropenem, imipenem, metronidazole, and piperacillin/tazobactam; however, resistance to clindamycin renders its empirical use inappropriate.

The spread of NDM-1-harboring Klebsiella pneumoniae is a worldwide concern. In this study the whole-genome sequence (WGS) of a carbapenem- and colistin-resistant K. pneumoniae 838Gr strain is presented. This strain was isolated from a urine sample of a patient in the Intensive Care Unit (ICU) at Volos Hospital, Greece. The initial assembly produced 224 contigs with a combined genome size of 5,561,803 bp and a GC content of 57.21%. The K. pneumoniae strain carried IncR, IncFIA, IncC, and repB (R1701) replicons. Multilocus sequence typing (MLST) analysis revealed that the isolate belonged to the sequence type 11 (ST11) and serogroup KL24 and O2a. The WGS analysis identified several beta-lactamase genes (blaTEM-1B, blaCTX-M-15, blaNDM-1, blaOXA-1, blaVEB-1, blaOXA-10, and blaSHV-11) alongside resistance genes for other antibiotic classes, including floR2, cmlA1, cmlA5, catB3, arr-3, aph(6)-Id, aadA2. Colistin resistance was attributed to specific point mutations in pmrB (R256G, T140P). This is the first report of a carbapenem- and colistin-resistant K. pneumoniae ST11 strain in Greece. The findings of this study highlight the urgent need for increased surveillance and stringent infection control.

Treatment options are limited for infections caused by carbapenem-resistant Klebsiella pneumoniae (CRKP) isolates due to the production of metallo-β-lactamase (MBL). The ceftazidime-avibactam (CZA)/ aztreonam (ATM) combination represents a new therapeutic approach in MBL-positive isolates. Our study aims to determine distribution of carbapenemase genes in CRKP isolates and to investigate the in vitro synergistic effect of the CZA/ATM combination.Our study included 48 CRKP strains isolated from various clinical samples. Identification was performed using MALDI-TOF MS (bioMérieux, France), and susceptibility was tested with Vitek-2 (bioMérieux). The susceptibility to CZA and ATM was determined using CZA 30/20 µg and ATM 30 µg (Oxoid™,UK) disks. Carbapenemase genes VIM, NDM, IMP, KPC, OXA-23, OXA-58, OXA-48, and OXA-51 were investigated in only 44 isolates using the Bio-Speedy Carbapenem resistance qPCR (Bioexen, Turkiye) kit. Synergy testing was evaluated with double disk diffusion, gradient strip (bioMérieux)/disk diffusion, and broth disk elution methods.Out of 48 carbapenem-resistant isolates, 40 (83.3%) isolates showed resistance to CZA and 46 (95.8%) to aztreonam. Synergy was detected with all three methods in all isolates identified as resistant to CZA, CZA-sensitive isolates were not included in this evaluation. The most frequently detected carbapenemase genes were NDM+OXA-48, found in 28 (63.6%) of the isolates.Although the NDM+OXA-48 coexistence predominates in our center, in vitro synergy between CZA and ATM was detected in all of CZA-resistant isolates. Performing the CZA+ATM synergy test and reporting the result is crucial for choosing appropriate treatment in CRKP infection.