Epidemiology and antibiotic susceptibility profiles of obligate anaerobes in a hospital of central Italy during a one-year (2019) survey.

OBJECTIVES: In this study, we report on the epidemiology and susceptibility profiles of anaerobic pathogens consecutively isolated from various clinical samples at an Italian hospital during a one-year survey. METHODS: The collection included all non-duplicated consecutively collected anaerobic clinical isolates during 2019 in San Luca Hospital (Lucca, Italy). Antimicrobial susceptibility testing was performed using MICRONAUT-S Anaerobes MIC lyophilized plates (MERLIN Diagnostika, Germany) and interpreted using EUCAST criteria (11.0). RESULTS: A total of 169 Gram-negative and 213 Gram-positive were collected. The most frequent anaerobes were Bacteroides spp. (120, 31.4%) followed by Finegoldia magna (62, 16.2%). External ulcers were the most common source of isolates (39%), followed by blood (25.7%). In 230 patients (65%) polymicrobial aerobic/anaerobic isolates were cultured from the same external ulcer specimen. High resistance rates to clindamycin were overall detected, with the highest values among the genera Parabacteroides, Bacteroides, Prevotella, Gram-positive anaerobic cocci and Clostridium. High resistance rates were also observed to metronidazole among both Gram-positive and Gram-negative species, ranging between 10.8-50% and 13.8-46.2%, respectively. CONCLUSIONS: Our findings revealed that anaerobes susceptibility patterns have become less predictable due to an increase of resistance and suggest that periodic resistance surveillance should also be carried out for anaerobes in order to guide empirical therapy.

Antibacterial and Anti-Inflammatory Activity of an Antimicrobial Peptide Synthesized with D Amino Acids.

The peptide SET-M33 is a molecule synthesized in tetra-branched form which is being developed as a new antibiotic against Gram-negative bacteria. Its isomeric form with D amino acids instead of the L version (SET-M33D) is also able to kill Gram-positive bacteria because of its higher resistance to bacterial proteases (Falciani et al., PLoS ONE, 2012, 7, e46259). Here we report the strong in vitro activity of SET-M33D (MIC range 0.7-6.0 µM) against multiresistant pathogens of clinical interest, including Gram-positives Staphylococcus aureus, Staphylococcus saprophyticus, and Enterococcus faecalis, and various Gram-negative enterobacteriaceae. SET-M33D antibacterial activity is also confirmed in vivo against a MRSA strain of S. aureus with doses perfectly compatible with clinical use (5 and 2.5 mg/Kg). Moreover, SET-M33D strongly neutralized lipopolysaccharide (LPS) and lipoteichoic acid (LTA), thus exerting a strong anti-inflammatory effect, reducing expression of cytokines, enzymes, and transcription factors (TNF-α, IL6, COX-2, KC, MIP-1, IP10, iNOS, NF-κB) involved in the onset and evolution of the inflammatory process. These results, along with in vitro and in vivo toxicity data and the low frequency of resistance selection reported here, make SET-M33D a strong candidate for the development of a new broad spectrum antibiotic.