In Vitro Activity of Dalbavancin and Fourteen Other Antimicrobial Agents Against Toxigenic Clostridioides Difficile Clinical Isolates in a Greek Tertiary-Care Hospital.

OBJECTIVE: Clostridioides difficile is a major cause of healthcare-associated diarrhea worldwide. For years, metronidazole and vancomycin were considered the standard treatment for C. difficile infection (CDI). However, they are increasingly being associated with treatment failure and recurrence. In this study we investigated the in vitro activity of dalbavancin and fourteen other antimicrobials against 155 toxigenic C. difficile isolates originating from patients with C. difficile-associated diarrhea. MATERIALS AND METHODS: Antimicrobial susceptibility was evaluated by the MIC Test Strip and the results were interpreted using both the Clinical and Laboratory Standards Institute (CLSI) and the European Committee on Antimicrobial susceptibility Testing (EUCAST) breakpoints. RESULTS: C. difficile isolates were fully susceptible to metronidazole, vancomycin, amoxicillin/ clavulanate, piperacillin/tazobactam, and tigecycline. All isolates were dalbavancin susceptible by the CLSI breakpoint (≤ 0.25 µg/ml) compared with 97.4% susceptibility by the EUCAST breakpoint (≤ 0.125 µg/ml). Dalbavancin demonstrated significantly lower MIC50 and MIC90 values compared to vancomycin (0.047 vs. 0.38 and 0.125 vs. 0.5, respectively, p < 0.001). Resistance rates to penicillin, ampicilin, cefoxitin, imipenem, meropenem, clindamycin, moxifloxacin, chloramphenicol, and tetracycline were 20%, 14.2% , 100%, 75.5%, 0.6%, 51%, 36.1%, 3.2%, and 14.8%, respectively. Multidrug-resistant (MDR) phenotypes were detected among 41.3% of the isolates. CONCLUSION: Dalbavancin exhibited potent activity against the isolates tested. As C. difficile is an important healthcare-associated pathogen, continued surveillance is required to monitor for development of resistance.

Prevalence and antimicrobial resistance of bacterial enteropathogens in Crete, Greece, during 2011-2022.

Diarrheal diseases are of great concern worldwide and are responsible for considerable morbidity and mortality. This study investigated the epidemiology and the antibiotic susceptibility of bacterial enteropathogens among diarrheal patients of all ages in Crete, Greece during 2011-2022. Stool specimens were tested by conventional cultural methods for Salmonella, Shigella, Campylobacter, diarrheagenic Escherichia coli (EPEC, STEC), Yersinia enterocolitica, Aeromonas species and Clostridioides difficile. Antimicrobial susceptibility was determined by the disk diffusion method for Enterobacterales, Campylobacter and Aeromonas, and by the gradient diffusion method for C. difficile. Of the 26,060 stool samples from patients of any age, 1,022 (3.9%) were positive for bacterial enteropathogens. Campylobacter spp. were the most commonly isolated bacteria (56.4%), followed by Salmonella enterica (32.3%), and E. coli (EPEC, STEC) (6.5%). Toxigenic C. difficile was isolated from 341 out of 8,848 diarrheal specimens examined (3.9%). Resistance to ampicillin was observed in 12.4% of Salmonella, 66.7% of Shigella and 34.8% of E. coli (EPEC, STEC) isolates. Resistance to trimethoprim/sulfamethoxazole was observed in 5.8% of Salmonella, 33.3% of Shigella, and 15.1% of E. coli (EPEC, STEC) isolates. High rates of ciprofloxacin resistance (77.3%) were detected among Campylobacter isolates, while resistance to erythromycin was observed in 2.4% of them. All C. difficile isolates were susceptible to vancomycin and metronidazole. Our findings suggest declining trends in prevalence of bacterial enteropathogens, except for Campylobacter spp. and changes in the susceptibility rates to antimicrobials. Continuous surveillance of prevalence and antimicrobial susceptibility of bacterial enteropathogens is mandatory for implementing targeted and effective prevention and infection control measures.

Antimicrobial Resistance of Streptococcus pneumoniae Clinical Serotypes between 2017 and 2022 in Crete, Greece.

BACKGROUND: Pneumococcal disease is still considered a global problem. With the introduction of pneumococcal conjugate vaccines (PCVs) serotype epidemiology changed, but antimicrobial resistance persists constituting a serious problem. The current study aimed to determine the serotype distribution and the antimicrobial susceptibility of recent Streptococcus pneumoniae isolates, following implementation of the 13-valent conjugate vaccine (PCV13). MATERIALS AND METHODS: From January 2017 to December 2022 we evaluated 116 nonduplicate S. pneumoniae isolates collected from adult patients (21 - 98 years) cared for in the University Hospital of Heraklion, Crete, Greece. Pneumococcal isolates were serotyped by the Quellung reaction, and antimicrobial susceptibility testing was performed using E-test. Multidrug resistance (MDR) was defined as non-susceptibility to at least one agent in ≥3 classes of antibiotics. RESULTS: Among the 116 isolates, 31% were recognized as invasive pneumococcal strains, while 69% were non-invasive. The isolates tested belonged to 25 different serotypes. The most prevalent serotypes were 11A (10.3%), and 35B (10.3%), followed by 3 (9.5%), 15A (7.8%), 25F (6.9%), 19A (5.3%), 35F (5.3%), and others (44.6%). The coverage rates of PCV13 and the pneumococcal polysaccharide vaccine (PPSV23) were 26.7% and 57.8%, respectively. PCV13 and PPSV23 serotypes decreased between 2017 - 2019 and 2020 - 2022, with a parallel increase in the non-vaccine types. Resistance rates to erythromycin, clindamycin, trimethoprim/sulfamethoxazole, penicillin, levofloxacin, and ceftriaxone, were 40.5%, 21.6%, 13.8%, 12.1%, 3.4%, and 0%, respectively. All isolates were susceptible to vancomycin, linezolid, and daptomycin. MDR was observed among 36 (31%) S. pneumoniae isolates. CONCLUSION: The increasing levels of resistance in S. pneumoniae in Crete, Greece, highlight the need for continuous surveillance of antimicrobial resistance and development of strategies for its reduction, including antimicrobial stewardship programs, increased pneumococcal vaccination, and development of next generation PCVs with a wider serotype coverage.

Clinical and microbiological characteristics of nocardiosis: A 5-year single-center study in Crete, Greece.

Nocardiosis is a rare disease affecting both immunocompromised and immunocompetent hosts, presented in various clinical forms ranging from localized to disseminated infection. Aim of the present study was to investigate the clinical and microbiological characteristics of nocardiosis, antimicrobial resistance profiles, treatment, and outcomes of Nocardia infection over the last 5 years at our institution. The medical records and microbiological data of patients affected by nocardiosis and treated at the university hospital of Heraklion, Crete, Greece, between 2018 and 2022, were retrospectively analyzed. The isolates were identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and through sequencing of 16S rRNA. Antimicrobial susceptibility for 17 agents was determined by E-test and results were interpreted according to CLSI guidelines. Among the 28 Nocardia isolates, eight species were identified, with Nocardia brasiliensis being the most prevalent (32.1%), followed by Nocardia otitidiscaviarum (25%), and Nocardia farcinica (14.3%). Skin and soft tissue infections were the most common presentations, noted in 13 (50%) patients, followed by pulmonary infection presented in 10 (38.5%) patients. Fifteen patients (57.7%) had at least one underlying disease, and 11 (42.3%) were on immunosuppressive or long-term corticosteroid treatment. Susceptibility rates of linezolid, tigecycline, amikacin, trimethoprim-sulfamethoxazole, moxifloxacin, and imipenem were 100, 100, 96.4, 92.9, 82.1, and 42.9%, respectively. The 26 patients in this study were treated with various antibiotics. Mortality rate was 3.8%, and the patient who died had disseminated infection. Since epidemiology and antimicrobial susceptibility are evolving, continuous surveillance is mandatory in order to initiate appropriate treatment in a timely manner.

A 60-Year Literature Review on Hepatic Actinomycosis.

Hepatic actinomycosis (HA) is a rare infection with an indolent course, atypical clinical manifestations, nonspecific laboratory and imaging findings, and challenging diagnosis. We describe a case of a 35-year-old female who developed HA 2 weeks after gastrectomy. In addition, we analyzed clinical characteristics and outcome of 157 additional cases of HA identified in a 60-year literature review. Patients with HA were predominantly male (57%) and more than one-half were between 40 and 70 years of age. The infection was cryptogenic in 80.8% of cases. Risk factors for HA were identified in 63.1% of the patients. Clinical presentation included fever (57.7%), abdominal pain (52.1%), weight loss (45.1%), anorexia (27.5%), fatigue and chills (12.7% each), and malaise (12%) over a 2.35 ± 3.5 months period. Leukocytosis, elevated alkaline phosphatase, erythrocyte sedimentation rate, and C-reactive protein were the most frequent laboratory findings. Radiologic imaging revealed that the right lobe was more frequently affected (62.5%) with a single lesion found in two-thirds of cases. Diagnosis was achieved by histopathologic examination in 70.6% of cases. Cultures yielded Actinomyces in 45 instances, with A. israelii being the most frequent species. Less than one-half of the patients were treated only with antibiotics, while the others received combined medical and surgical treatment. The median duration of antibiotic therapy was 135 days. The presence of multiple lesions or solid tumor-like lesions (without liquefaction) was significantly associated with medical therapy alone. The outcome was favorable in most cases (94%). Although rarely encountered, HA should be considered in patients with a chronic or subacute inflammatory process of the liver to promptly diagnose and treat.

Epidemiology and in vitro activity of ceftazidime-avibactam, meropenem-vaborbactam, imipenem-relebactam, eravacycline, plazomicin, and comparators against Greek carbapenemase-producing Klebsiella pneumoniae isolates.

BACKGROUND: The increase in carbapenem-resistant Klebsiella pneumoniae (CRKP) infections is of great concern because of limited treatment options. New antimicrobials were recently approved for clinical therapy. This study evaluated the epidemiology of carbapenemase-producing K. pneumoniae isolates collected at a Greek university hospital during 2017-2020, and their susceptibilities to ceftazidime-avibactam (CAZ/AVI), meropenem-vaborbactam (M/V), imipenem-relebactam (I/R), eravacycline, plazomicin, and comparators. METHODS: Minimum inhibitory concentrations (MICs) were evaluated by Etest. Only colistin MICs were determined by the broth microdilution method. Carbapenemase genes were detected by PCR. Selected isolates were typed by multilocus sequence typing (MLST). RESULTS: A total of 266 carbapenemase-producing K. pneumoniae strains were isolated during the 4-year study period. Among them, KPC was the most prevalent (75.6%), followed by NDM (11.7%), VIM (5.6%), and OXA-48 (4.1%). KPC-producing isolates belonged mainly to ST258 and NDM producers belonged to ST11, whereas OXA-48- and VIM producers were polyclonal. Susceptibility to tigecycline, fosfomycin, and colistin was 80.5%, 83.8%, and 65.8%, respectively. Of the novel agents tested, plazomicin was the most active inhibiting 94% of the isolates at ≤ 1.5 µg/ml. CAZ/AVI and M/V inhibited all KPC producers and I/R 98.5% of them. All OXA-48 producers were susceptible to CAZ/AVI and plazomicin. The novel ß-lactam/ß-lactamase inhibitors (BLBLIs) tested were inactive against MBL-positive isolates, while eravacycline inhibited 61.3% and 66.7% of the NDM and VIM producers, respectively. CONCLUSIONS: KPC remains the predominant carbapenemase among K. pneumoniae, followed by NDM. Novel BLBLIs, eravacycline, and plazomicin are promising agents for combating infections by carbapenemase-producing K. pneumoniae. However, the emergence of resistance to these agents highlights the need for continuous surveillance and application of enhanced antimicrobial stewardship.

Ceftazidime-avibactam, meropenen-vaborbactam, and imipenem-relebactam in combination with aztreonam against multidrug-resistant, metallo-ß-lactamase-producing Klebsiella pneumoniae.

The spread of multidrug-resistant (MDR), metallo-ß-lactamase (MBL)-producing Klebsiella pneumoniae represents a major therapeutic challenge. The newly introduced ß-lactam-ß-lactamase inhibitors (BLBLIs), ceftazidime/avibactam (CAZ/AVI), meropenem/vaborbactam (M/V), and imipenem/relebactam (I/R) are inactive against MBLs. The aim of this study was to evaluate the in vitro efficacy of aztreonam (ATM) in combination with CAZ/AVI, M/V, and I/R against 40 MDR, MBL-producing, and serine-ß-lactamases co-producing Klebsiella pneumoniae using the Etest method. Synergy was defined as a fractional inhibitory concentration index ≤0.5. All isolates were resistant to ATM, CAZ/AVI, and I/R and 38/40 (95%) were resistant to M/V. Synergy was observed in 97.5% in the combinations CAZ/AVI-ATM, and I/R-ATM and in 72.5% in the combination M/V-ATM. Further clinical studies are required to confirm the efficacy of these antimicrobial combinations.

Antimicrobial susceptibility patterns of clinically significant Gram-positive anaerobic bacteria in a Greek tertiary-care hospital, 2017-2019.

Antimicrobial resistance among anaerobic bacteria is increasingly recognized with geographic differences. In this study we analyzed the distribution and antimicrobial susceptibility profiles of 358 Gram-positive clinically significant anaerobes, isolated from 2017 to 2019, in a Greek tertiary-care hospital. The species identification was performed by Vitek 2 and conventional biochemical methods, and the antimicrobial susceptibility testing by the E-test method. The antimicrobial agents tested were penicillin, ampicillin, amoxicillin-clavulanic acid, piperacillin-tazobactam, cefoxitin, imipenem, meropenem, clindamycin, metronidazole, moxifloxacin, chloramphenicol, tigecycline and vancomycin. Clostridioides difficile isolates were also tested against tetracycline. The results were interpreted using the CLSI and the EUCAST breakpoints. Clostridium species accounted for 35.5% of the isolates, followed by Gram-positive cocci (GPAC) (33.2%) and non-spore-forming bacilli (31.3%). Beta-lactams, ß-lactam/ß-lactamase inhibitors, cefoxitin, carbapenems, chloramphenicol, tigecycline and vancomycin proved all effective against the GPAC tested. Clindamycin, moxifloxacin and metronidazole resistance varied among different species of GPAC. Clindamycin and moxifloxacin resistance observed was 10% and 5% for Cutibacterium acnes, 25% and 6.2% for Actinomyces odontolyticus and 40% and 5% for Clostridium perfringens. C. difficile isolates were fully susceptible to metronidazole, vancomycin, and tigecycline. Resistance rates to clindamycin, moxifloxacin and tetracycline were 62.9%, 30% and 24.3%, respectively. These data highlight the need for periodic surveillance to monitor changes in susceptibility profiles.

Surveillance of antimicrobial resistance in recent clinical isolates of Gram-negative anaerobic bacteria in a Greek University Hospital.

The aim of our study was to determine the antimicrobial susceptibility profiles of 267 Gram-negative clinically significant anaerobes, isolated between October 2016 and October 2019, in a Greek university hospital. The species identification was performed by conventional methods and using the Vitek 2 automated system. Antimicrobial susceptibility testing to determine the MICs was performed by the E-test method. The antimicrobial agents tested were penicillin, ampicillin, amoxicillin-clavulanic acid, piperacillin-tazobactam, cefoxitin, imipenem, meropenem, clindamycin, metronidazole, moxifloxacin, chloramphenicol and tigecycline. The results were interpreted using the CLSI and FDA breakpoints. The majority of the isolates belonged to Bacteroides fragilis group (58.8%), followed by Prevotella spp. (23.2%), Fusobacterium spp. (11.2%) and Veillonella spp. (6.4%). The most prevalent types of infection were skin and soft tissue infections (34.8%), and inta-abdomonal infections (29.6%). Among all isolates tested, the lowest rates of resistance (<5%) were detected to carbapenems, metronidazole, chloramphenicol and tigecycline. Resistance to piperacillin-tazobactam was observed in 5.4%, 24.6%, 3.3% and 17.6%, of B. fragilis, B. fragilis group, Fusobacterium spp. and Veillonella spp. isolates, respectively. Although a high prevalence of resistance to clindamycin, cefoxitin, and moxifloxacin, was detected particularly among members of the B. fragilis group, cefoxitin resistance was low for Prevotella spp. (3.2%), Fusobacterium spp. (3.3%) and Veillonella spp. (0%). Our findings underscore the need for periodic monitoring of antimicrobial resistance in order to guide empirical therapy.

Epidemiology and antifungal susceptibility patterns of Candida isolates from Greek women with vulvovaginal candidiasis.

Vulvovaginal candidiasis (VVC) is a common infection of the genital tract affecting millions of women worldwide. Data on epidemiological trends of VVC in Greece are scarce. This study was undertaken to evaluate the prevalence of VVC among symptomatic women in Crete, Greece, identify the Candida species involved and determine their susceptibility to antifungals. Over a 6-year period (2012-2017), 10 256 symptomatic women with vaginitis were evaluated. Isolation of yeasts was performed on Sabouraud dextrose agar with chloramphenicol, and the isolates were identified using the API 20 C AUX and/or the Vitek 2 YST card. Susceptibility of the isolates to amphotericin, fluconazole, voriconazole and flucytosine was determined by the Vitek 2 automated system. The results were interpreted according to Clinical and Laboratory Standards criteria. Vaginal swab cultures of 1217 (11.9%) women yielded Candida species. Recurrent VVC was documented in 62 (5.1%) of them. Candida albicans was the most frequently isolated species (75.6%), followed by Candida glabrata (13.6%). Overall, resistance rates to amphotericin B, fluconazole, voriconazole and flucytosine were 0.2%, 6.6%, 1.4% and 2.1%, respectively. Fluconazole resistance of C. albicans significantly increased in the second period of the study (2015-2017) (P = 0.031). This study demonstrated that VVC is a common infection among women in our region, with C. albicans being the predominant species involved. Although resistance to antifungals was infrequent, resistance to fluconazole among C. albicans isolates was found to significantly increase with time. Continued surveillance of changes in species distribution and susceptibility to antifungals are necessary to guide treatment.