Molecular and biochemical characterization of the natural chromosome-encoded class A beta-lactamase from Pseudomonas luteola

Antibiotic Resistant Pseudomonas Spp. Spoilers in Fresh Dairy Products: An Underestimated Risk and the Control Strategies

Microbial multidrug resistance (MDR) is a growing threat to public health mostly because it makes the fight against microorganisms that cause lethal infections ever less effective. Thus, the surveillance on MDR microorganisms has recently been strengthened, taking into account the control of antibiotic abuse as well as the mechanisms underlying the transfer of antibiotic genes (ARGs) among microbiota naturally occurring in the environment. Indeed, ARGs are not only confined to pathogenic bacteria, whose diffusion in the clinical field has aroused serious concerns, but are widespread in saprophytic bacterial communities such as those dominating the food industry. In particular, fresh dairy products can be considered a reservoir of Pseudomonas spp. resistome, potentially transmittable to consumers. Milk and fresh dairy cheeses products represent one of a few "hubs" where commensal or opportunistic pseudomonads frequently cohabit together with food microbiota and hazard pathogens even across their manufacturing processes. Pseudomonas spp., widely studied for food spoilage effects, are instead underestimated for their possible impact on human health. Recent evidences have highlighted that non-pathogenic pseudomonads strains (P. fluorescens, P. putida) are associated with some human diseases, but are still poorly considered in comparison to the pathogen P. aeruginosa. In addition, the presence of ARGs, that can be acquired and transmitted by horizontal genetic transfer, further increases their risk and the need to be deeper investigated. Therefore, this review, starting from the general aspects related to the physiological traits of these spoilage microorganisms from fresh dairy products, aims to shed light on the resistome of cheese-related pseudomonads and their genomic background, current methods and advances in the prediction tools for MDR detection based on genomic sequences, possible implications for human health, and the affordable strategies to counteract MDR spread.

Profiling of VOCs released from different salivary bacteria treated with non-lethal concentrations of silver nitrate

Considering the shortcomings related to antibiotics usage, the introduction of other bacteriostatic and bactericidal agents that present synergetic effects or standalone properties is urgently needed. AgNO₃ is an important bactericidal agent, which imparts various functions on bacteria dependent on its concentration. Therefore, an understanding of its mechanisms of action in infinitesimal concentrations plays an important role which can ultimately lead to AgNO₃ involvement in the pharmaceutical industry. The monitoring of VOC (volatile organic compound) profiles emitted by bacteria is a simple method to assess changes occurring in bacterial metabolism. In this study, VOCs of Hafnia alvei, Pseudomonas luteola and Staphylococcus warneri cultures were analyzed both in the absence and in the presence of three concentrations of AgNO₃. Headspace solid-phase microextraction gas chromatography/mass spectrometry (HS-SPME-GC/MS) was employed for extraction and analysis. After supplementation with AgNO₃, changes in the emitted fingerprints were investigated. Odorants associated with mouth-related and systemic diseases, like dimethyl trisulfide, indole (halitosis) and 2-hexanone (celiac disease), were also affected by addition of AgNO₃. Statistical tests proved discrimination between obtained profiles with more that 90% variability. Moreover, physiological states of bacteria after dosage with various concentration of stressing agent were investigated and explained by the mechanisms of action.

Post-surgical Gangrene with Pseudomonas luteola Resulting in Limb Amputation: A Case Review

Pseudomonas luteola is a rare infective agent with a variable resistance-sensitivity panel. Clinical suspicion and appropriate empiric treatment is necessary for resolution of such infections. We report a case of post-surgical gangrene as a result of Pseudomonas luteola culminating in limb amputation.

Microbial characterisation of the edible grasshopper Ruspolia differens in raw condition after wild-harvesting in Uganda

This research aimed at establishing the chemical intrinsic properties and the microbial quality of an edible grasshopper Ruspolia differens and the effect of its source (geographical area) in Uganda, trading point, swarming season and plucking on these parameters. The intrinsic properties of the grasshopper can support the growth of a wide variety of microorganisms. High counts of total aerobic microbes, Enterobacteriaceae, lactic acid bacteria, total aerobic spores, and yeasts and moulds were obtained. Metagenetic analyses yielded 1793 Operational Taxonomic Units (OTUs) belonging to 24 phyla. Actinobacteria, Bacteroidetes, Firmicutes, Fusobacteria and Proteobacteria were the most abundant phyla, while members of the genera Acinetobacter, Buttiauxella, Lactococcus, Staphylococcus and Undibacterium were the most abundant OTUs. A number of genera harbouring potential pathogens (Acinetobacter, Bacillus, Buttiauxella, Campylobacter, Clostridium, Staphylococcus, Pseudomonas and Neisseria) were identified. The geographical area, trading point, swarming season and plucking significantly influenced microbial counts and bacterial diversity. The high microbial counts predispose R. differens to fast microbial spoilage, while the presence of Clostridium and Campylobacter makes this grasshopper a potential source of food borne diseases. Further research should identify the specific spoilage microorganisms of R. differens and assess the characteristics of this grasshopper that support growth of food pathogens.

A Structure-Based Classification of Class A β-Lactamases, a Broadly Diverse Family of Enzymes

For medical biologists, sequencing has become a commonplace technique to support diagnosis. Rapid changes in this field have led to the generation of large amounts of data, which are not always correctly listed in databases. This is particularly true for data concerning class A β-lactamases, a group of key antibiotic resistance enzymes produced by bacteria. Many genomes have been reported to contain putative β-lactamase genes, which can be compared with representative types. We analyzed several hundred amino acid sequences of class A β-lactamase enzymes for phylogenic relationships, the presence of specific residues, and cluster patterns. A clear distinction was first made between dd-peptidases and class A enzymes based on a small number of residues (S70, K73, P107, 130SDN132, G144, E166, 234K/R, 235T/S, and 236G [Ambler numbering]). Other residues clearly separated two main branches, which we named subclasses A1 and A2. Various clusters were identified on the major branch (subclass A1) on the basis of signature residues associated with catalytic properties (e.g., limited-spectrum β-lactamases, extended-spectrum β-lactamases, and carbapenemases). For subclass A2 enzymes (e.g., CfxA, CIA-1, CME-1, PER-1, and VEB-1), 43 conserved residues were characterized, and several significant insertions were detected. This diversity in the amino acid sequences of β-lactamases must be taken into account to ensure that new enzymes are accurately identified. However, with the exception of PER types, this diversity is poorly represented in existing X-ray crystallographic data.

Prevalence of Multidrug-Resistant Bacteria on Fresh Vegetables Collected from Farmers' Markets in Connecticut

This study determined the prevalence of multidrug-resistant (MDR) Acinetobacter baumannii on fresh vegetables collected from farmers' markets in Connecticut. One hundred samples each of fresh carrots, potatoes, and lettuce were sampled and streaked on selective media, namely Leeds Acinetobacter and MDR Acinetobacter agars. All morphologically different colonies from MDR Acinetobacter agar were identified by using Gram staining, biochemical tests, and PCR. In addition, susceptibility of the isolates to 10 antibiotics commonly used in humans, namely imipenem, ceftriaxone, cefepime, minocycline, erythromycin, colistin-sulfate, streptomycin, neomycin, doxycycline, and rifampin was determined by using an antibiotic disk diffusion assay. The results revealed that only two samples of potato and one sample of lettuce yielded A. baumannii. In addition, all carrot samples were found to be negative for the organism. However, several other opportunistic, MDR human pathogens, such as Burkholderia cepacia (1% potatoes, 5% carrots, and none in lettuce), Stenotrophomonas maltophilia (6% potatoes, 2% lettuce, and none in carrots), and Pseudomonas luteola (9% potatoes, 3% carrots, and none in lettuce) were recovered from the vegetables. Antibiotic susceptibility screening of the isolates revealed high resistance rates for the following: ceftriaxone (6 of 6), colistin-sulfate (5 of 6), erythromycin (5 of 6), and streptomycin (4 of 6) in B. cepacia; colistin-sulfate (11 of 11) and imipenem (10 of 11) in P. luteola; colistin-sulfate (8 of 8), ceftriaxone (8 of 8), cefepime (7 of 8), erythromycin (5 of 8), and imipenem (4 of 8) in S. maltophilia; and imipenem (3 of 3), ceftriaxone (3 of 3), erythromycin (3 of 3), and streptomycin (3 of 3) in A. baumannii. The results revealed the presence of MDR bacteria, including human pathogens on fresh produce, thereby highlighting the potential health risk in consumers, especially those with a compromised immune system.

Chromosome-encoded extended-spectrum class A β-lactamase MIN-1 from Minibacterium massiliensis

Minibacterium massiliensis strain CIP107820 is a recently discovered waterborne Gram-negative rod isolated from hospital water samples. It harbors a chromosomally located gene encoding an Ambler class A extended-spectrum β-lactamase termed MIN-1, sharing 56%, 54%, and 51% amino acid identities with β-lactamases LUT-1, KPC-2, and CTX-M-2, respectively. β-Lactamase MIN-1 hydrolyzes penicillins, narrow-spectrum cephalosporins, cefotaxime, and, less efficiently, cefepime, while ceftazidime and carbapenems are very poor substrates, and cephamycins and aztreonam are not hydrolyzed.