Four-year overall survival update from the phase III HIMALAYA study of tremelimumab plus durvalumab in unresectable hepatocellular carcinoma

BACKGROUND

In the phase III HIMALAYA study (NCT03298451) in unresectable hepatocellular carcinoma (uHCC), STRIDE (Single Tremelimumab Regular Interval Durvalumab) significantly improved overall survival (OS) versus sorafenib; durvalumab monotherapy was noninferior to sorafenib for OS. Results reported herein are from a 4-year updated OS analysis of HIMALAYA.

PATIENTS AND METHODS

Participants with uHCC and no previous systemic treatment were randomized to STRIDE (n = 393), durvalumab (n = 389), or sorafenib (n = 389). The updated data cut-off was 23 January 2023. OS and serious adverse events (AEs) were assessed. Additionally, baseline characteristics and subsequent therapies were analyzed in long-term survivors (≥36 months beyond randomization).

RESULTS

For STRIDE, durvalumab, and sorafenib, median [95% confidence interval (CI)] follow-up was 49.12 months (46.95-50.17 months), 48.46 months (46.82-49.81 months), and 47.31 months (45.08-49.15 months), respectively. OS hazard ratio (95% CI) for STRIDE versus sorafenib was 0.78 (0.67-0.92). The 36-month OS rate for STRIDE was 30.7% versus 19.8% for sorafenib. The 48-month OS rate remained higher for STRIDE at 25.2%, versus 15.1% for sorafenib. The long-term OS benefit of STRIDE was observed across clinically relevant subgroups and was further improved in participants who achieved disease control. Long-term survivors with STRIDE (n = 103) included participants across clinically relevant subgroups, and 57.3% (59/103) had no reported subsequent anticancer therapy. No new serious treatment-related AEs occurred with STRIDE from the primary analysis (17.5%; 68/388). Durvalumab maintained OS noninferiority to sorafenib and no late-onset safety signals were identified.

CONCLUSIONS

These data represent the longest follow-up to date in phase III studies in uHCC. The unprecedented 3- and 4-year OS rates reinforce the sustained long-term OS benefit of STRIDE versus sorafenib. STRIDE maintained a tolerable yet differentiated safety profile from other current uHCC therapies. Results continue to support the long-term benefits of STRIDE in a diverse population, reflective of uHCC globally.

Integration of membrane processes for the recovery and separation of polyphenols from winery and olive mill wastes using green solvent-based processing

Winery and olive mill industries generate large amounts of wastes causing important environmental problems. The main aim of this work is the evaluation of different membrane separation processes like microfiltration, ultrafiltration, nanofiltration, and reverse osmosis for the recovery of polyphenols from winery and olive mill wastes in aqueous solutions. Membrane processes were tested separately in a closed-loop system, and by an integration in a concentration mode sequential design (open-loop). Feed flow rate was varied from 1 to 10 mL min^-1, and permeate samples were taken in order to measure the polyphenols concentration. The separation and concentration efficiency were evaluated in terms of total polyphenol content, and by polyphenols families (hydroxybenzoic acids (HB), hydroxycinnamic acids (HC), and flavonoids (F)), using high performance liquid chromatography. Results showed that MF and UF membranes removed suspended solids and colloids from the extracts. NF was useful for polyphenols separation (HB rejections were lower than for HC and F: HB rejections of 50 and 63% for lees filters and olive pomace extracts, respectively), and RO membranes were able to concentrate polyphenols streams (86 and 95% rejection from lees filters and olive pomace, respectively). Membranes sequential designs for lees filters and olive pomace extracts, using a selective membrane train composed by UF, NF and RO membranes, were able to obtain polyphenol rich streams and high-quality water streams for reuse purposes.

Management of meat by- and co-products for an improved meat processing sustainability

Large amounts of meat by- and co-products are generated during slaughtering and meat processing, and require rational management of these products for an ecological disposal. Efficient solutions are very important for sustainability and innovative developments create high added-value from meat by-products with the least environmental impact, handling and disposal costs, in its transition to bioeconomy. Some proteins have relevant technological uses for gelation, foaming and emulsification while protein hydrolyzates may contribute to a better digestibility and palatability. Protein hydrolysis generate added-value products such as bioactive peptides with relevant physiological effects of interest for applications in the food, pet food, pharmaceutical and cosmetics industry. Inedible fats are increasingly used as raw material for the generation of biodiesel. Other applications are focused on the development of new biodegradable plastics that can constitute an alternative to petroleum-based plastics. This manuscript presents the latest developments for adding value to meat by- and co-products and discusses opportunities for making meat production and processing more sustainable.

Incidence of hepatocellular carcinoma in patients with non-alcoholic fatty liver disease: A meta-analysis and meta-regression

Objective

Nonalcoholic fatty liver disease (NAFLD) may be a risk factor for hepatocellular carcinoma (HCC), but the extent of this association still needs to be addressed. Pooled-incidence rates of HCC across the disease spectrum of NAFLD have never been estimated by meta-analysis.

Methods

In this systematic review, we searched Web of Science, Embase, Pubmed, and the Cochrane library from January 1st, 1950 through July 30th, 2020. We included studies reporting on HCC incidence in patients with NAFLD. The main outcomes were pooled HCC incidences in patients with NAFLD at distinct severity stages. Summary estimates were calculated with random-effects models. Sensitivity analyses and meta-regression analyses were carried out to address heterogeneity. The protocol for this review was registered in Prospero (CRD42018092861).

Results

Eighteen studies, with a total of 470,404 patients were included. In patients with NAFLD at a stage earlier than liver cirrhosis, HCC incidence was of 0.03 per 100 person-years (PYs) (95% confidence interval 0.01-0.07, I2=98%). This rate rose to 3.78 per 100PYs (2.47-5.78, I2=93%) when considering studies that only included patients with liver cirrhosis. Among the latter patients, those undergoing regular HCC screening displayed an incidence of 4.62 per 100PYs (2.77-7.72, I2= 77%).

Conclusion

Patients with NAFLD-related liver cirrhosis have a risk of developing HCC similar to that reported for patients with cirrhosis from other etiologies. Evidence documenting the risk in patients with NASH or simple steatosis is limited, but HCC incidence in these populations may lie below thresholds used to recommend HCC screening. Well-designed prospective studies in these subsets of patients are needed.

Valorisation options for Zn and Cu recovery from metal influenced acid mine waters through selective precipitation and ion-exchange processes: promotion of on-site/off-site management options

Acid mine waters (AMWs), generated in the processing of polymetallic sulphides, contain copper and zinc as the main valuable transition metal ions, which are typically removed by liming, due to their great environmental impact. In this context, this work proposes the integration of selective precipitation (SP) and ion-exchange (IX) processes for the separation and recovery of both valuable metals to encourage on-site and off-site management options promoting valorisation routes. Thus, the main objectives of this work were (i) the selective removal of Fe(III) and Al(III), using NaOH under pH control (pH < 5) to avoid the precipitation of Cu(II) and Zn(II) and (ii) the evaluation of a solvent-impregnated resin (Lewatit VP OC 1026, named VP1026) and a cation IX resin (Lewatit TP 207, named TP207) for the sequential extraction of both metal ions from AMW (batch and column experiments). Results indicated that the metallic pollution load was mostly removed during the SP process of Fe(III) (>99%) and Al(III) (>90%) as hydroxylsulphates (e.g., schwertmannite and basaluminite). The metal extraction profiles were determined for both metals from pH 1 to pH 5 by batch experiments, and indicated that the best extraction of Zn(II) was obtained using VP1026, being higher than 96% (pH = 2.6-2.8), whereas TP207 extraction performance was optimal for Cu(II) extraction (>99%) at pH = 3-4. Moreover, in dynamic experiments using a fixed-bed configuration, it was possible to separate and concentrate Zn(II) (concentration factor = 10) and Cu(II) (concentration factor = 40) using VP1026 and TP207, respectively. Overall, the integration of SP and IX processes showed a great potential in the separation and recovery of valuable metals from mine waters to promote a circular economy, based on the management proposal for non-ferrous metallurgical industries. The recovered Zn-rich and Cu-rich sulphuric concentrated streams were theoretically evaluated for further on-site or off-site re-use treatments (e.g., electrowinning, precipitation, crystallization).

Arsenic impact on the valorisation schemes of acidic mine waters of the Iberian Pyrite Belt: Integration of selective precipitation and spiral-wound nanofiltration processes

Arsenic and selenium presence in acid mine waters (AMWs) limits their disposal due to environmental regulations. The focus to solve the economic infeasibility is directed to sustainable solutions, promoting resource recovery. In fact, rare earth elements (REEs) recovery is proposed in most of the Iberian Pyrite Belt AMWs. However, the presence of arsenic and selenium may impact in the REEs recovery. Among different alternatives, nanofiltration (NF) provides a concentration stage on REEs recovery, reduces the nominal flow and removes hazardous species. In this work, Iberian Pyrite Belt AMWs with up to 10 mg/L REEs, containing arsenic (2 mg/L), were treated with a NF membrane. Firstly, AMWs were pre-treated with H₂O₂/NaOH, to oxidise Fe(II) to Fe(II) and As(III) to As(V), promoting their removal and avoiding their potential precipitation at the membrane. Subsequently, NF pressure effect (6-20 bar) was studied, removing metals (>95 %), whereas arsenic rejections ranged from 60 to 71 %. Then, water recovery potential was evaluated at 10, 15 and 22 bar by reproducing a 10-stages NF plant. Results showed that the proposed treatment could be an alternative for arsenic and selenium removal (70 μg/L and 0.5 μg/L permeate concentrations, respectively) to achieve mining discharge limits according to regulations.

Recent Progress in Enzymatic Release of Peptides in Foods of Animal Origin and Assessment of Bioactivity

There is a wide variety of peptides released from food proteins that are able to exert a relevant benefit for human health, such as angiotensin-converting enzyme inhibition, antioxidant, anti-inflammatory, hypoglucemic, or antithrombotic activity, among others. This manuscript is reviewing the recent advances on enzymatic mechanisms for the hydrolysis of proteins from foods of animal origin, including the types of enzymes and mechanisms of action involved, the strategies followed for the isolation and identification of bioactive peptides through advanced proteomic tools, and the assessment of bioactivity and its beneficial effects. Specific applications in fermented and/or ripened foods where a significant number of bioactive peptides have been reported with relevant in vivo physiological effects on laboratory rats and humans as well as the hydrolysis of animal food proteins for the production of bioactive peptides are also reviewed.

From nanofiltration membrane permeances to design projections for the remediation and valorisation of acid mine waters

Acidic Mine Waters (AMWs) are characterised by high acidity (pH < 3) as H₂SO₄ and elevated contents of metals (Al, Fe, Cu, Zn), including rare earth elements (REEs). Due to the exhaustion of minable REE containing-minerals, AMWs are increasingly regarded as an alternative source of REEs. Among the different alternatives for the pre-concentration of AMWs required to make the REE extraction possible, nanofiltration (NF) membranes emerge as a promising technology because they not only successfully reject multivalent ions (metals), allowing its concentration in the retentate stream, but also permit the transport of monovalent ones, such as H⁺ and HSO₄^-, allowing the recovery of sulphuric acid in the permeate. Despite this potential of NF, there is still a lack of modelling tools for predicting the performance of NF membranes because of its dependence on solution composition, membrane properties and interaction between both. In this study, a prediction tool based on the Solution-Electro-Diffusion model (including the effect of solution composition) was developed and experimentally validated for the application of two polyamide-based NF membranes (NF270 and Desal DL) for the recovery of REEs and H₂SO₄ from three different synthetic solutions mimicking AMWs (pH 1.0, 60 mg/L REEs and, 25-600 mg/L Al, Cu, Ca and Zn) differing in their Fe concentration (0-2125 mg/L). Metals were effectively rejected (>98%), whereas H₂SO₄ was transported across the membrane (H+ rejections <30%). The mathematical model was able to predict the performance of both membranes as well as the potential scaling events associated with Fe and Al hydroxides and hydroxy-sulphates.

Integration of liquid-liquid membrane contactors and electrodialysis for ammonium recovery and concentration as a liquid fertilizer

The accumulation of ammonia in water bodies can cause eutrophication and reduce water quality. Furthermore, 80% of the ammonia in the world is consumed as fertilizer, which makes it a resource that can be recovered under the circular economy concept. Then, ammonia from wastewater can be valorised for agricultural applications. Liquid-liquid membrane contactors (LLMCs) have been postulated as a novel and eco-friendly technology for ammonia recovery, because they can convert dissolved ammonia into ammonium salts by an acid stripping solution. The concentration of the ammonium salt produced is limited by the co-transport of water in LLMC. Further concentration by electrodialysis (ED) is presented as a solution to overcome this problem. In this work, ammonia streams with different initial ammonia concentrations (1.7-4.0 g/L) were treated by LLMCs to produce liquid ammonium salt fertilizers (as NH₄NO₃ and NH₄H₂PO₄). Then, these ammonium solutions were concentrated by ED in order to achieve the nitrogen content required for direct application in agriculture for fertigation. After the LLMC process, the fertilizer obtained was composed of approximately 5.1% or 10.1% (w/w) nitrogen, depending on the initial ammonia concentration. After that, it was possible to concentrate these ammonium salts by a factor of 1.6 ± 0.3 using ED with an optimal energy consumption of 0.21 ± 0.08 kWh/kg ammonium salt and 93.1 ± 4.2% of faradaic yield. This gave a liquid fertilizer composed of 15.6% (w/w) nitrogen as NH₄NO₃. Overall, it was possible to integrate two innovative membrane technologies for the valorisation and concentration of nutrients from ammonia wastewater streams.

Peptides with Potential Cardioprotective Effects Derived from Dry-Cured Ham Byproducts

The interest in using food byproducts as a source of bioactive peptides has increased significantly in the recent years. The goal of this work was to determine the presence and stability of peptides showing angiotensin I-converting enzyme (ACE-I), endothelin-converting enzyme (ECE), dipeptidyl peptidase-IV (DPP-IV), and platelet-activating factor-acetylhydrolase (PAF-AH) inhibitory activity derived from dry-cured ham bones, which could exert cardiovascular health benefits. ACE-I and DPP-IV inhibitory peptides were stable against heating typically used in Mediterranean household cooking methods and also to in vitro digestion. PAF-AH inhibitory activity significantly increased following simulated gastrointestinal digestion whereas ECE inhibitory significantly decreased ( P < 0.05). The mass spectrometry analysis revealed a notable degradation of hemoglobin-derived peptides after simulated digestion, and the release of a large number of dipeptides that may have contributed to the observed bioactivities. These results suggest that natural peptides from Spanish dry-cured ham bones could contribute to a positive impact on cardiovascular health.

Evaluating the response to locoregional and systemic treatment for hepatocellular carcinoma

Evaluating the response to different treatments is a decisive factor in the clinical management of patients with hepatocellular carcinoma because it can determine the efficacy of the treatment and because it can detect the recurrence of treated tumors or the appearance of new lesions that can be candidates for new treatments. When locoregional treatments that induce necrosis or molecular therapies are applied, the treated lesions usually change their behavior on imaging studies. It is important to point out that the size of the lesions does not usually decrease, at least initially, and some lesions can even appear to increase in size. For this reason, it is essential to know the mechanisms of action for each treatment applied and the spectrum of findings that these treatments can cause in the different imaging techniques used to assess the response.

Effect of cooking and in vitro digestion on the antioxidant activity of dry-cured ham by-products

Dry-cured ham by-products have been traditionally used in Mediterranean household cooking of broths and stews. The aim of this work was to evaluate the effect of cooking treatments and in vitro gastrointestinal digestion on the antioxidant activity of natural peptides found in bones from Spanish dry-cured hams. The antioxidant activity was tested using five different assays and results demonstrated that cooking using conventional household methods increased the antioxidant activity of ham by-products when assessed using different antioxidant assays with the exception of the ABTS radical scavenging measurement assay. Simulated gastrointestinal digestion showed no significant effect on the antioxidant activity of ham by-products and antioxidant activity decreased when assessed using the ORAC and β-carotene bleaching assays. Analysis by MALDI-TOF MS revealed a considerable breakdown of peptides due to the action of gastrointestinal enzymes, mainly in samples cooked at 100°C for 1h. In addition, 459 peptides derived from 57 proteins were identified and quantified using mass spectrometry in tandem, evidencing that peptides derived from collagen protein were responsible for the differences in antioxidant activities observed between the uncooked and cooked samples after digestion. The results show the potential of dry-cured ham bones as a source of antioxidant peptides that retain their bioactivity after household cooking preparations and gastrointestinal digestion.

Small peptides hydrolysis in dry-cured meats

Large amounts of different peptides are naturally generated in dry-cured meats as a consequence of the intense proteolysis mechanisms which take place during their processing. In fact, meat proteins are extensively hydrolysed by muscle endo-peptidases (mainly calpains and cathepsins) followed by exo-peptidases (mainly, tri- and di-peptidyl peptidases, dipeptidases, aminopeptidases and carboxypeptidases). The result is a large amount of released free amino acids and a pool of numerous peptides with different sequences and lengths, some of them with interesting sequences for bioactivity. This manuscript is presenting the proteomic identification of small peptides resulting from the hydrolysis of four target proteins (glyceraldehyde-3-phosphate dehydrogenase, beta-enolase, myozenin-1 and troponin T) and discusses the enzymatic routes for their generation during the dry-curing process. The results indicate that the hydrolysis of peptides follows similar exo-peptidase mechanisms. In the case of dry-fermented sausages, most of the observed hydrolysis is the result of the combined action of muscle and microbial exo-peptidases except for the hydrolysis of di- and tri-peptides, mostly due to microbial di- and tri-peptidases, and the release of amino acids at the C-terminal that appears to be mostly due to muscle carboxypeptidases.

Patents for ELISA tests to detect antibiotic residues in foods of animal origin

The use of antibiotics in the European Union was banned since the 1(st) of January 2006. At present, and even though such ban, residues of drugs used in animal therapy or, illegally, as growth promoters might be found in food. Such residues may cause adverse health effects on consumers like allergic reactions in sensitive individuals develop transmissible antimicrobial resistance in food microflora, and have technological implications in the manufacture of fermented products. This is the reason why to check food for the presence of antibiotics residues is still necessary. ELISA test constitutes an attractive screening technique due to its simplicity, large number of samples per kit and possibility of automation. The aim of this manuscript is to provide a review of the numerous patents and applications for the analysis of antibiotic residues in foods.

Haemophilus influenzae bla(ROB-1) mutations in hypermutagenic deltaampC Escherichia coli conferring resistance to cefotaxime and beta-lactamase inhibitors and increased susceptibility to cefaclor

The clinical use of cefaclor has been shown to enrich Haemophilus influenzae populations harboring cefaclor-hydrolyzing ROB-1 beta-lactamase. Such a selective process may lead to the increased use of extended-spectrum cephalosporins or beta-lactams plus beta-lactamase inhibitors and, eventually, resistance to these agents, which has not previously been observed in H. influenzae. In order to establish which bla(ROB-1) mutations, if any, could confer resistance to extended-spectrum cephalosporins and/or to beta-lactamase inhibitors, a plasmid harboring bla(ROB-1) was transformed into hypermutagenic strain Escherichia coli GB20 (DeltaampC mutS::Tn10), and this construct was used in place of H. influenzae bla(ROB-1). Strain GB20 with the cloned gene was submitted to serial passages in tubes containing broth with increasing concentrations of selected beta-lactams (cefotaxime or amoxicillin-clavulanate). Different mutations in the bla(ROB-1) gene were obtained during the passages in the presence of the different concentrations of the selective agents. Mutants resistant to extended-spectrum cephalosporins harbored either the Leu169-->Ser169 or the Arg164-->Trp164 substitution or the double amino acid change Arg164-->Trp164 and Ala237-->Thr237. ROB-1 mutants that were resistant to beta-lactams plus beta-lactamase inhibitors and that harbored the Arg244-->Cys244 or the Ser130-->Gly130 replacement were also obtained. The cefaclor-hydrolyzing efficiencies of the ROB-1 variants were strongly decreased in all mutants, suggesting that if bla(ROB-1) mutants were selected by cefaclor, this drug would prevent the further evolution of this beta-lactamase toward molecular forms able to resist extended-spectrum cephalosporins or beta-lactamase inhibitors.

[Comparative in vitro activity of ertapenem against aerobic and anaerobic bacteria]

The in vitro activity of ertapenem (MK-0826), a new carbapenem, was studied against 389 aerobic microorganisms (187 Enterobacteriaceae, 15 Aeromonas spp., 42 Staphylococcus spp., 43 Streptococcus spp., 15 Enterococcus spp., 30 Haemophilus spp., 15 Moraxella catarrhalis, 12 Neisseria gonorrhoeae, 15 Pseudomonas aeruginosa and 15 Acinetobacter spp.) and 54 anaerobic isolates (15 Clostridium spp., 12 Peptostreptococcus spp. and 27 fragilis group Bacteroides recovered from four Spanish hospitals. Ertapenem activity was compared with that of imipenem, piperacillin-tazobactam, cefoxitin, ceftriaxone, ceftazidime, cefepime, and norfloxacin. Ertapenem was the most active antibiotic against Enterobacteriaceae (MIC(90) < or =0.5 mg/l) particularly in the case of broad-spectrum, extended-spectrum and chromosomally encoded AmpC betalactamase-producing strains. Ertapenem exhibited less activity, even lower than that of imipenem, against P. aeruginosa, Acinetobacter spp. and enterococci (MIC(90) > or =16 mg/l). Ertapenem was active against methicillin-susceptible S. aureus and coagulase-negative staphylococci, beta-haemolytic streptococci, and Streptococcus pneumoniae (MIC(90) < or =1 mg/l). In the case of Haemophilus spp., M. catarrhalis and N. gonorrhoeae, ertapenem, with a MIC(90) < or =0.06 mg/l resulted the most active antibiotic tested. When considering the anaerobes, ertapenem displayed a broad spectrum of activity, similar to that of imipenem, against Clostridium spp. (MIC(90) 2 mg/l) and was slightly less active against Bacteroides fragilis (MIC(90) 0.5 mg/l). Both carbapenems were the most active among the tested compounds. Due to its activity against almost all pathogens studied, ertapenem appears to be an option for the treatment of mixed bacterial infections.

Macrolide resistance in Peptostreptococcus spp. mediated by ermTR: possible source of macrolide-lincosamide-streptogramin B resistance in Streptococcus pyogenes

Eighty percent (21 of 26) of macrolide-resistant Peptostreptococcus strains studied harbored the ermTR gene. This methyltransferase gene is also the most frequently found gene among macrolide-lincosamide-streptogramin B-resistant Streptococcus pyogenes strains. Transfer of the ermTR gene from Peptostreptococcus magnus to macrolide-susceptible S. pyogenes strains indicates that this resistance determinant may circulate among gram-positive aerobic and anaerobic species of the oropharyngeal bacterial flora.

ACI-1 from Acidaminococcus fermentans: characterization of the first beta-lactamase in Anaerobic cocci

Acidaminococcus fermentans belongs to the group of strictly anaerobic gram-negative cocci. All previously described Acidaminococcus strains are susceptible to beta-lactam antibiotics. An A. fermentans strain (RYC-MR95) resistant to penicillin and expanded-spectrum cephalosporin (amoxicillin and cefotaxime MICs, 64 microgram/ml) was isolated from a human perianal abscess. A fragment encoding a beta-lactamase from genomic DNA was cloned in Escherichia coli K-12 strain HB101, and the recombinant strain expressed resistance to amoxicillin (MIC, 1,024 microgram/ml) and cefotaxime (MIC, 4 microgram/ml). Clavulanic acid decreased the MICs to 8 and 0.03 microgram/ml, respectively. Analysis of the nucleotide sequence revealed a new class A beta-lactamase, ACI-1. In accordance with its biochemical properties, we propose to assign ACI-1 to functional group 2be. The ACI-1 enzyme (estimated pI 4.3) had <50% amino acid identity with any other class A beta-lactamases, the closest being ROB-1 from Haemophilus influenzae (44%). ACI-1 was closer to class A beta-lactamases from some gram-positive organisms (41 to 44% amino acid identity with Bacillus beta-lactamases) than to most class A enzymes from gram-negative organisms (TEM-1, 24.6%). The aci1 gene had a G+C content of 42.1%, in contrast with 56% G+C content for genomic DNA from A. fermentans, thus suggesting that aci1 may have been obtained by horizontal gene transfer.

Resistance of Veillonella to Hydrosoluble Pristinamycins: A Possible Outer Membrane Barrier Effect

An in vitro study on 25 Veillonella strains showed a consistent clindamycin susceptibility with resistance to erythromycin and to the hydrosoluble pristinamycins, quinupristin and dalfopristin and its 30:70 combination, the synergistin RP59500. Double erythromycin-clindamycin disk tests did not show any inducible resistance pattern. The addition of 10 or 50 mug/mL of polymyxin B nonapeptide, an outer membrane permeabilizing agent, consistently reduced quinupristin and dalfopristin MICs in most strains. This result suggests that the Veillonella outer membrane may act as a permeability barrier to these antibiotics, as in the case of other Gram-negative bacteria.

Resistance of anaerobic bacteria to antimicrobial agents in Spain

As a consequence of antibiotic consumption, the entire microbial ecosystem attached to man is evolving towards resistance. In Spain, penicillin resistance (MIC > 0.5 mg/l) is found in about 10% of Peptostreptococcus, Clostridium perfringens and Eubacterium, and in 50% of Veillonella. Cefoxitin resistance ( > 2 mg/l) is present in 10 to 20% of Peptostreptococcus and Clostridium, and in 50% of Eubacterium; 21% of Bacteroides (fragilis group) strains are resistant to 16 mg/l. A very low rate of imipenem resistance (> or = 128 mg/l) is found among Bacteroides (1%), but for 5% of the isolates MICs of imipenem are 2 to 4 mg/l. Metronidazole resistance ( > 8 mg/l) is found in 5 to 10% of Peptostreptococcus, Clostridium and Veillonella, and in less than 1% of the Bacteroides fragilis group. Erythromycin resistance ( > 2 mg/l) is present in over two-thirds of the Peptostreptococcus, Veillonella and Fusobacterium isolates, and in 27% of the Clostridium perfringens strains. Clindamycin resistance ( > 4 mg/l) is found in 10 to 20% of the Peptostreptococcus, Clostridium and Eubacterium isolates, and in 20% of the Bacteroides of the fragilis group, this rate being higher (30%) among faecal isolates.

Antibiotic sensitivity of ribosomes from wild-type and clindamycin resistant Bacteroides vulgatus strains

The sensitivity to different antibiotics of in-vitro polyuridylic acid-dependent polypeptide synthesizing system from Bacteroides vulgatus RYC18F6 and two clindamycin-resistant derivatives was studied. The ribosomes from the resistant strains were not affected by concentrations of up to 0.1 mM clindamycin and lincomycin. In contrast, streptogramin B was found to cause strong stimulation of the clindamycin-resistant polymerizing systems. The modified ribosomes from the resistant strains were more sensitive to other antibiotics like sparsomycin and chloramphenicol. The data indicate that resistance in these B. vulgatus mutant strains is due to alteration of the ribosome structure.

Inducible expression of ribosomal clindamycin resistance in Bacteroides vulgatus

The abilities of erythromycin and clindamycin to act as inducers of clindamycin resistance in the strain Bacteroides vulgatus RYC18F6 is evaluated in vivo (efficiency of plating of inhibitory clindamycin concentrations) and in vitro [efficiency of poly(U)-directed polypeptide synthesis by ribosomes]. Uninduced cells failed to grow during the first 72 h, even at a very low clindamycin concentration (0.1 microgram/ml); after induction with erythromycin or clindamycin, cells were able to form colonies at 32 micrograms/ml after 48 h. The in vitro polymerization test with B. vulgatus RYC18F6 ribosomes (S-30 extract) showed that ribosomes from uninduced cells were fully sensitive to the inhibitory effect of clindamycin. Ribosomes obtained from erythromycin- or clindamycin-induced cells presented a reduced sensitivity to clindamycin inhibition. These results show that resistance to clindamycin in B. vulgatus RYC18F6 is an inducible phenomenon involving a ribosomal modification, probably similar to that previously described for gram-positive bacteria.

Resistance of Peptostreptococcus spp. to macrolides and lincosamides: inducible and constitutive phenotypes

The activities of erythromycin and clindamycin against 350 Peptostreptococcus strains were studied during a 5-year period (1986 to 1991). In 5.1% of the Peptostreptococcus strains, which presented dissociated resistance (clindamycin MIC, less than or equal to 1 microgram/ml; erythromycin MIC, greater than 8 micrograms/ml), evidence of inducible macrolide-lincosamide resistance was shown. A total of 17.7% of the strains presented a constitutive phenotype; the clindamycin and erythromycin MICs for these strains were greater than 8 micrograms/ml.