Acta microbiologica et immunologica Hungarica最新文献

The aim of this prospective pilot study was to compare culture and microbiome results of the removed tonsils of patients with assumed distant focal disease (11 patients) and those who underwent a tonsillectomy, due to other reasons, such as recurrent tonsillitis, tonsil stones or snoring (nine patients). Aerobic culture was carried out for samples taken from the surface of the tonsils by swabs before tonsillectomy for all 20 patients. The squeezed detritus and the tissue samples of removed tonsils, taken separately for the right and left tonsils, were incubated aerobically and anaerobically. The microbiome composition of tissue samples of removed tonsils was also evaluated. Based on the culture results of the deep samples Staphylococcus aureus was the dominating pathogen, besides a great variety of anaerobic and facultative anaerobic bacteria present in the oral microbiota in those patients who underwent tonsillectomy due to distant focal diseases. Microbiome study of the core tissue samples showed a great diversity on genus and species level among patients of the two groups however, S. aureus and Prevotella nigrescens were present in higher proportion in those, whose tonsils were removed due to distant focal diseases. Our results may support previous findings about the possible triggering role of S. aureus and P. nigrescens leading to distant focal diseases. Samples taken by squeezing the tonsils could give more information about the possible pathogenic/triggering bacteria than the surface samples cultured only aerobically.

Pseudomonas aeruginosa has been in the center of attention for several years as an opportunistic human pathogen implicated in many severe acute and chronic infections particularly in immunocompromised patients. Its high persistence and resistance against many antimicrobial agents are mostly attributed to biofilm formation. Biofilms are microbial communities mainly consisting of extracellular polymeric substances that encapsulate bacteria together and protect them from extracellular stresses. This cell aggregation is a stress response that P. aeruginosa employes as a survival strategy during growth with the toxic detergents. This process has shown to involve several operons such as psl, pel, and alg. Here we used P. aeruginosa strain PAO1 in control group, 40 P. aeruginosa strains from sink and 40 strains from surface of public places. Biofilm formation and gene expression were measured before and after exposure to sub minimum inhibitory concentration (sub-MIC) of biocides chlorhexidine diacetate and benzalkonium chloride. The qRT-PCR and biofilm formation results demonstrated an increase in biofilm formation ability and gene expression of pslA/B and pelA/B in two groups collected from sink and surface in contrast to the control group. A remarkable increase was observed in the biofilm formation and expression of pslA in the bacterial strain collected from the sink after exposure to biocides chlorhexidine diacetate. Both Pel and Psl appeared to have redundant functions as structural scaffolds in biofilms. Sub-MIC levels of detergents can improve biofilm formation ability of P. aeruginosa and therefore trigger resistance.

The present study aimed to explore the genomic characteristics of eight New Delhi metallo-β-lactamase-1 (NDM-1)-producing carbapenem-resistant Pseudomonas aeruginosa (CRPA) isolates from a Bulgarian tertiary hospital (2021-2023) in comparison to blaNDM-1-positive strains originating from the Balkans. Antimicrobial susceptibility testing, phenotypic assays for carbapenemase activity, PCR screening, whole-genome sequencing (WGS), and phylogenomic analysis were performed. Seven of the CRPA isolates investigated (Minimum inhibitory concentration values of imipenem and meropenem >32 mg L-1) were also resistant to piperacillin-tazobactam, ceftazidime, ceftazidime-avibactam, cefepime, ceftolozane-tazobactam, amikacin, tobramycin, ciprofloxacin, and levofloxacin, but were susceptible to colistin (0.5-2 mg L-1) and cefiderocol (0.25-1 mg L-1). The P. aeruginosa Pae57 isolate (designated Pae57) remained susceptible to aminoglycosides as well. WGS uncovered the co-existence of blaNDM-1 and blaGES-1. The isolates belonged to the ST654 high-risk clone, except for Pae57 (ST611). Alignment against reference sequences revealed the presence of a Tn21 transposon harboring bleMBL-blaNDM-1-ISAba125. It was similar to that found in the P. aeruginosa ST654 NDM1_1 strain (GCA_020404785.1) from Serbia. Phylogenomic analysis of our isolates indicated that seven of them (ST654) differed from each other in no more than 44 single-nucleotide polymorphisms (SNPs). Pae57 (ST611) was strikingly different (>21,700 SNPs) compared to all Balkan strains. In conclusion, to our knowledge this is the first report of blaNDM-1-positive P. aeruginosa ST611 isolation, which indicates the transmission dynamics of this determinant between high-risk and potentially high-risk P. aeruginosa clones. Obtained results unveil the dissemination of clonally related NDM-1-producing P. aeruginosa strains in the monitored hospital for approximately a 2-year period.

The rate of pandrug-resistant Acinetobacter baumannii strains is on the rise in all continents. This bacterium can acquire resistance to all antibiotics, even to colistin. Alterations in the lipid A or/and the two-component pmrAB were earlier detected in colistin resistance. We investigated and analyzed two strains of A. baumannii (ABRC1 and ABRC2) isolated from two patients admitted to intensive care unit with a septic shock. Both strains were resistant to all tested antibiotics including colistin with a MIC >256 mg L-1. Colistin resistance genes (pmrA, pmrB, lpxA, lpxC, lpxD, and lpsB) of two strains (ABRC1 and ABRC2) were investigated by PCR and sequencing. Obtained nucleic acid sequences were aligned with reference sequences of ATCC 19606 and 17987. In this study two amino acid mutations, N287D in the lpxC gene and E117K in the lpxD gene, were detected in both ABRC1 and ABRC2 strains. ABRC1 had an additional H200L mutation in the pmrA gene. Both colistin resistant strains harbored the same A138T mutation in the pmrB gene. The ABRC2 strain also had an alteration in the kinase domain, specifically an R263S substitution of the histidine kinase domain. Three identical mutations were found in the lpsB gene of both A. baumannii strains: Q216K + H218G + S219E. As a result, a newly deduced protein sequence in both ABRC1 and ABRC2 strains differed from those described in ATCC 17978 and 19606 strains was determined. Colistin resistance is multifactorial in A. baumannii. In our study we detected novel mutations in colistin resistant A. baumannii clinical isolates.

Carbapenem-resistant Enterobacterales (CRE) have become a major public health problem worldwide. The aim of this study was to investigate efficacy of ceftazidime/avibactam and plazomicin on carbapenem-resistant Klebsiella pneumoniae and Escherichia coli isolates. Susceptibility of imipenem, meropenem, ertapenem, ceftazidime/avibactam and plazomicin was investigated by broth-microdilution method. Major carbapenemases NDM, VIM, IMP, KPC, OXA-48 as well as other β-lactamases namely, TEM, SHV, OXA-1-like, CTX-M, ACC, FOX, MOX, DHA, CIT, EBC, VEB, GES, PER were investigated by PCR. A total of 120 carbapenem-resistant isolates (60 E. coli and 60 K. pneumoniae) were included in this study and blaOXA-48-like was found in 78.33%, blaNDM in 26.66%, blaKPC in 7.5%, blaIMP in 5.83%, and blaVIM in 5%. Among 94 isolates with the blaOXA-48-like gene, 22.3% were resistant to ceftazidime/avibactam and 51.1% were resistant to plazomicin. Of 32 isolates with blaNDM, 31 (96.9%) were resistant to ceftazidime/avibactam and 30 (93.75%) were resistant to plazomicin, and both antibiotics had limited effects against blaNDM carriers (P < 0.001). Of the 12 isolates with blaNDM+OXA-48 combination, 11 (91.7%) were resistant to ceftazidime/avibactam and plazomicin. The effect of both antibiotics was significantly lower in strains with blaNDM+OXA-48 combination (P < 0.005).The most common carbapenemase genes in this study were blaOXA-48-like and blaNDM. Ceftazidime/avibactam demonstrated a good efficacy among OXA-48 producing K. pneumoniae and E. coli, however, plazomicin had a significantly lower antibacterial effect in our study. Both antimicrobial agents should be considered as an option by evaluating combined susceptibility results and gene patterns obtained by regional and global molecular data in the treatment of CRE infections.

Klebsiella pneumoniae is one of the most prevalent bacteria causing urinary tract infections (UTIs). Its increasing resistance to a wide array of antibiotics limits available treatment options. This study investigated the characteristics and trends of antimicrobial resistance in K. pneumoniae isolated from UTIs in Crete, Greece, during 2017 and 2022. Among the 11,946 Enterobacteriaceae isolated from urine specimens, a total of 1,771 K. pneumoniae isolates were identified (14.8%), with an isolation frequency secondary to Escherichia coli (66.3%). K. pneumoniae isolates increased over the years, with a peak in the year 2022. Higher resistance rates were detected in ciprofloxacin (41%), trimethoprim/sulfamethoxazole (TMP/SMX) (38.1%) and nitrofurantoin (33.9%). Resistance to ciprofloxacin, amoxicillin/clavulanic acid, tigecycline, and TMP/SMX significantly increased from 33.7%, 24%, 6%, and 33.1%, respectively, over the years 2017-2019, to 47.8%, 34.2%, 14.3% and 42.8%, respectively, over the period 2020-2022. ESBL production and carbapenem resistance were decreased by 2.2% and 3.7%, respectively, over the two three-year periods (2017-2019 and 2020-2022). Among the 278 carbapenem-resistant K. pneumoniae (CRKP) isolates, 164 (59%), 66 (23.7%), 18 (6.5%) and 16 (5.8%) were positive for KPC, NDM, VIM and OXA-48 enzymes, respectively. Only 14 (5%) isolates harboured two carbapenemase genes, namely 10 (3.6%) both blaNDM and blaVIM, and 4 (1.4%) both blaKPC and blaNDM. Females, inpatients and the elderly were more frequently affected by CRKP. The frequency of multidrug-resistant (MDR) and extensively drug-resistant (XDR) isolates were 32.6% and 7.7%, respectively. Continuous surveillance of local microbial prevalence and monitoring of antimicrobial resistance patterns provide critical information to guide the empiric therapy for UTIs and control the spread of MDR bacteria.

The worldwide burden of disease of bacterial meningitis remains high, despite the decreasing incidence following introduction of routine vaccination campaigns.The aim of our study was to evaluate the epidemiological and bacteriological profile of paediatric bacterial meningitis (BM) in Tunisian children, during the period 2003-2019, following the implementation of Haemophilus influenzae type b (Hib) vaccine (April 2011) and before 10-valent pneumoccocal conjugate vaccine (PCV10) introduction to the childhood immunization program.All bacteriologically confirmed cases of BM admitted to children's hospital of Tunis were recorded (January 2003 to April 2019). Serogroups of Neisseria meningitidis (Nm) and serotypes of Streptococcus pneumoniae (Sp) and H. influenzae (Hi) and antibiotic resistance were determined using conventional and molecular methods.Among 388 cases, the most frequent species were Sp (51.3%), followed by Nm (27.5%) and Hi (16.8%). We observed a significant decrease in Hi BM rate during the conjugated Hib vaccine use period (P < 0.0001). The main pneumococcal serotypes were 14, 19F, 6B, 23F and 19A and the serotype coverage of PCV10, PCV13, PCV15 and PCV20 was 71.3 and 78.8%, 79.4 and 81.9% respectively. The most frequent Nm serogroup was B (83.1%). Most Hi strains were of serotype b (86.9%). High levels of resistance were found: Sp and Nm to penicillin (respectively 60.1 and 80%) and Hi to ampicillin (42.6%). All meningococcal and Hi isolates were susceptible to third-generation cephalosporins and 7.2% of pneumococcal strains had decreased susceptibility to these antibiotics.The Hib conjugate vaccine decreased the rate of BM. Sp dominated the aetiology of BM in children in Tunisia. Conjugate vaccines introducing decreases not only BM cases but also antimicrobial resistance.

The JN.1 sub-variant is a new variant of the SARS-CoV-2 Omicron strain, derived from the BA.2.86 sub-variant. It was first detected in late 2023 and has quickly spread to many countries, becoming the most prevalent variant in some regions. JN.1 exhibits a unique mutation (L455S) in the spike protein compared to the BA.2.86 lineage, which may affect its transmissibility and immune evasion capabilities. JN.1 has been designated as a "variant of interest" by the World Health Organization due to its rapidly increasing spread and is being closely monitored for its impact on the COVID-19 pandemic. This study describes the emergence of SARS-CoV-2 JN.1 sub-variant in Tunisia, and reports its mutation profiles.Nasopharyngeal samples collected over a four-month period (October 2023 to January 2024) were subjected to RNA extraction and real-time RT-PCR confirmation of SARS-CoV-2 infection. The whole-genome sequencing was performed by an iSeq 100 sequencer and COVIDSeq kit reagents (Illumina, USA).Mutation analysis, using the NextClade platform and GISAID database, revealed the presence of JN.1 in 15 out of 80 positive cases (18.75%) during the study period.The emergence of JN.1 highlights the ongoing evolution of SARS-CoV-2 and the need for continued surveillance and research to better understand the characteristics and impact of emerging variants.