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Purpose: Pseudomonas aeruginosa infections in hospitals constitute an important problem due to the increasing multidrug resistance (MDR) and carbapenems resistance. The knowledge of resistance mechanisms in Pseudomonas strains is an important issue for an adequate antimicrobial treatment. Therefore, the objective was to investigate other antimicrobial resistance mechanisms in MDR P. aeruginosa strains carrying bla IMP , make a partial plasmids characterization, and determine if modifications in oprD gene affect the expression of the OprD protein. Methodology: Susceptibility testing was performed by Kirby Bauer and by Minimum Inhibitory Concentration (presence/absence of efflux pump inhibitor); molecular typing by Pulsed-field gel electrophoresis (PFGE), resistance genotyping and integrons by PCR and sequencing; OprD expression by Western blot; plasmid characterization by MOB Typing Technique, molecular size by PFGE-S1; and bla location by Southern blot. IMP Results: Among the 59 studied P. aeruginosa isolates, 41 multidrug resistance and carbapenems resistance isolates were detected and classified in 38 different PFGE patterns. Thirteen strains carried bla IMP; 16 bla GES and four carried both genes. This study centered on the 17 strains harboring bla IMP . New variants of β-lactamases were identified (bla GES-32, bla IMP-56, bla IMP-62 ) inside of new arrangements of class 1 integrons. The presence of bla IMP gene was detected in two plasmids in the same strain. The participation of the OprD protein and efflux pumps in the resistance to carbapenems and quinolones is shown. No expression of the porin OprD due to stop codon or IS in the gene was found. Conclusions: This study shows the participation of different resistance mechanisms, which are reflected in the levels of MIC to carbapenems. This is the first report of the presence of three new variants of β-lactamases inside of new arrangements of class 1 integrons, as well as the presence of two plasmids carrying bla IMP in the same P. aeruginosa strain isolated in a Mexican hospital.

Purpose. Haemophilus influenzae is a commensal organism found in the upper respiratory tract of humans. When H. influenzae becomes a pathogen, these bacteria can move out of their commensal niche and cause multiple respiratory tract diseases such as otitis media, sinusitis, conjunctivitis and bronchitis in children, and chronic obstructive pulmonary disease in adults. However, H. influenzae is currently considered a non-flagellate bacterium. Methodology and Results. In this study, 90 clinical isolates of H. influenzae strains (typeable and non-typeable) showed different degrees of the swarm-motility phenotype in vitro. Keys findings. One of these strains, NTHi BUAP96, showed the highest motility rate and its flagella were revealed using transmission electron microscopy and Ryu staining. Moreover, the flagellar genes fliC and flgH exhibited high homology with those of Actinobacillus pleuropneumoniae, Escherichia coli and Shigella flexneri. Furthermore, Western blot analysis, using anti-flagellin heterologous antibodies from E. coli, demonstrated cross-reaction with a protein present in NTHi BUAP96. Conclusion. This study provides, for the first time, information on flagellar expression in H. influenzae, representing an important finding related to its evolution and pathogenic potential.

Acinetobacter calcoaceticus-baumannii complex isolates have been frequently associated with hospital and community infections, with A. baumannii being the most common. Other Acinetobacter spp. not belonging to this complex also cause infections in hospital settings, and the incidence has increased over the past few years. Some species of the Acinetobacter genus possess a great diversity of antibiotic resistance mechanisms, such as efflux pumps, porins, and resistance genes that can be acquired and disseminated by mobilizable genetic elements. By means of whole-genome sequencing, we describe in the clinical Acinetobacter haemolyticus strain AN54 different mechanisms of resistance that involve blaOXA-265, blaNDM-1, aphA6, aac(6’)-Ig, and a resistance-nodulation-cell division-type efflux pump. This strain carries six plasmids, of which the plasmid pAhaeAN54e contains blaNDM-1 in a Tn125-like transposon that is truncated at the 3′ end. This strain also has an insertion sequence IS91 and seven genes encoding hypothetical proteins. The pAhaeAN54e plasmid is nontypable and different from other plasmids carrying blaNDM-1 that have been reported in Mexico and other countries. The presence of these kinds of plasmids in an opportunistic pathogen such as A. haemolyticus highlights the role that these plasmids play in the dissemination of antibiotic resistance genes, especially against carbapenems, in Mexican hospitals.

Methanol-consuming culturable bacteria were isolated from the plant surface, rhizosphere, and inside the stem of Neobuxbaumia macrocephala. All 38 isolates were facultative methylotrophic microorganisms. Their classification included the Classes Actinobacteria, Sphingobacteriia, Alpha-, Beta-, and Gammaproteobacteria. The deduced amino acid sequences of methanol dehydrogenase obtained by PCR belonging to Actinobacteria, Alpha-, Beta-, and Gammaproteobacteria showed high similarity to rare-earth element (REE)-dependent XoxF methanol dehydrogenases, particularly the group XoxF5. The sequences included Asp301, the REE-coordinating amino acid, present in all known XoxF dehydrogenases and absent in MxaF methanol dehydrogenases. The quantity of the isolates showed positive hybridization with a xoxF probe, but not with a mxaF probe. Isolates of all taxonomic groups showed methylotrophic growth in the presence of Ce3+ or Ca2+. The presence of xoxF-like sequences in methylotrophic bacteria from N. macrocephala and its potential relationship with their adaptability to xerophytic plants are discussed.

Acinetobacter calcoaceticus-baumannii complex isolates have been frequently associated with hospital and community infections, with A. baumannii being the most common. Other Acinetobacter spp. not ...

Purpose Pseudomonas aeruginosa infections in hospitals constitute an important problem due to the increasing multidrug resistance (MDR) and carbapenems resistance. The knowledge of resistance mechanisms in Pseudomonas strains is an important issue for an adequate antimicrobial treatment. Therefore, the objective was to investigate other antimicrobial resistance mechanisms in MDR P. aeruginosa strains carrying blaIMP, make a partial plasmids characterization, and determine if modifications in oprD gene affect the expression of the OprD protein. Methodology Susceptibility testing was performed by Kirby Baüer and by Minimum Inhibitory Concentration (presence/absence of efflux pump inhibitor); molecular typing by Pulsed-field gel electrophoresis (PFGE), resistance genotyping and integrons by PCR and sequencing; OprD expression by Western blot; plasmid characterization by MOB Typing Technique, molecular size by PFGE-S1; and blaIMP location by Southern blot. Results Among the 59 studied P. aeruginosa isolates, 41 multidrug resistance and carbapenems resistance isolates were detected and classified in 38 different PFGE patterns. Thirteen strains carried blaIMP; 16 blaGES and four carried both genes. This study centered on the 17 strains har-boring blaIMP. New variants of β-lactamases were identified (blaGES-32, blaIMP-56, blaIMP-62) inside of new arrangements of class 1 integrons. The presence of blaIMP gene was detected in two plasmids in the same strain. The participation of the OprD protein and efflux pumps in the resistance to carbapenems and quinolones is shown. No expression of the porin OprD due to stop codon or IS in the gene was found. Conclusions This study shows the participation of different resistance mechanisms, which are reflected in the levels of MIC to carbapenems. This is the first report of the presence of three new variants of β-lactamases inside of new arrangements of class 1 integrons, as well as the presence of two plasmids carrying blaIMP in the same P. aeruginosa strain isolated in a Mexican hospital.

Plant growth-promoting rhizobacteria (PGPR) increase plant growth and crop productivity. The inoculation of plants with a bacterial mixture (consortium) apparently provides greater benefits to plant growth than inoculation with a single bacterial strain. In the present work, a bacterial consortium was formulated containing four compatible and desiccation-tolerant strains with potential as PGPR. The formulation had one moderately (Pseudomonas putida KT2440) and three highly desiccation-tolerant (Sphingomonas sp. OF178, Azospirillum brasilense Sp7 and Acinetobacter sp. EMM02) strains. The four bacterial strains were able to adhere to seeds and colonize the rhizosphere of plants when applied in both mono-inoculation and multi-inoculation treatments, showing that they can also coexist without antagonistic effects in association with plants. The effects of the bacterial consortium on the growth of blue maize were evaluated. Seeds inoculated with either individual bacterial strains or the bacterial consortium were subjected to two experimental conditions before sowing: normal hydration or desiccation. In general, inoculation with the bacterial consortium increased the shoot and root dry weight, plant height and plant diameter compared to the non-inoculated control or mono-inoculation treatments. The bacterial consortium formulated in this work had greater benefits for blue maize plants even when the inoculated seeds underwent desiccation stress before germination, making this formulation attractive for future field applications.

We describe a method to evaluate bacterial tolerance to air desiccation at 30 °C and 50% relative humidity.

Here we describe two methods for assessing the ability of one bacteria to inhibit the growth of another through the production of antimicrobial compounds. In the first assay, the double agar layer method, only the secreted substances but not the candidate antagonist bacteria interact with the sensitive microorganisms. In the second assay, the simultaneous inhibition method, both microorganisms are grown together allowing the competitive exclusion.

Pineapple is the second most important tropical fruit in international trade and Mexico ranks ninth in world production. Pink disease is asymptomatic in the field and is characterized by the production of dark discoloration (amber-reddish brown) and its initial effects are not recognized until the fruits are cored and canned. Hence pink disease is considered a major problem in the pineapple canning industry. Four hundred and eighty isolates of pineapple were tested for antagonistic activity vs. Tatumella , causal agent of pink disease, and strain UAPS07070 was selected for further assays. Population dynamics were explored in co-inoculation in vitro and in planta with strain UAPS07070 and T. ptyseos UAPS07007. The population of UAPS07007, the producer strain of the disease severely declined in comparison with the controls. This work contributes to the knowledge of the ecology of pink disease in pineapple, as well as to the comprehension of the interactions between microorganisms colonizing the habitat of the plant.

Pink disease is a major problem in the pineapple canning industry. Affected fruit acquire a brownish pigment after pasteurization and can contaminate non-affected fruit before they are released to the consumer. In the last few years, Pantoea citrea has been described as the causative agent of pink disease. In this study, over 300 bacterial isolates from pineapple plants, growing in Mexican commercial fields, and from soil close to plant roots were recovered. Over 250 isolates showed a very high similarity in their phenotypic and genotypic traits with Tatumella ptyseos, a close relative of Pantoea. These isolates exhibited typical pathogenicity reactions in pineapple juice tests, pineapple slices and fruit. On this basis, molecular identification procedures for the Tatumella isolates associated with pink disease were implemented. In affected fruit populations around 10 6 CFU/g of fresh tissue were recovered. This is first time that T. ptyseos is demonstrated as a causal agent of pink disease.

The genus Klebsiella belongs to the family Enterobacteriaceae, and is currently considered to be non-motile and non-flagellated. In the present work, 25 Klebsiella strains isolated from nosocomial infections were assessed for motility under different growth conditions. One Klebsiella isolate, KpBUAP021, demonstrated a swim-like motility phenotype. The K. pneumoniae genotype was confirmed by 16S rRNA and rpoB gene sequence analysis. Multilocus sequence typing analysis also revealed that the KpBUAP021 strain places it in the ST345 sequence type, and belongs to the phylogenetic Kpl group. Transmission electron microscopy and the Ryu staining technique revealed that KpBUAP021 expresses polar flagella. Finally, the presence of fliC, fliA and flgH genes in this K. pneumoniae strain was confirmed. This report presents the first evidence for flagella-mediated motility in a K. pneumoniae clinical isolate, and represents an important finding related to its evolution and pathogenic potential. © 2016 The Authors.