Disbiosis bacteriana y su efecto en enfermedades bucales: una revisión bibliográfica / Bacterial dysbiosis and its effect on oral diseases: a review bibliographic

Objetivo: actualizar la información sobre la disbiosis bacteriana oral y su efecto en enfermedades bucales. Material y métodos: se realizó una revisión bibliográfica detallada, donde la búsqueda de artículos comenzó desde el 2014 con trabajos de investigación relacionados con el tema. Se aplicaron palabras clave para facilitar y delimitar el tema. En los resultados obtenidos se observa información específica de disbiosis bacteriana y los problemas y enfermedades que causan en la cavidad bucal. Conclusión: la cavidad oral es un ecosistema muy complejo e interactivo donde se desarrollan variedades de hábitats que establecen relaciones entre los microorganismos en los distintos medios bucales. Por lo general, el cuerpo humano vive en simbiosis con dichas bacterias, esta relación hospedador-huésped es producto de años de evolución y convivencia para poder tolerar a dichas especies y por medio de años de investigación, determinar a los agentes patógenos y a los simbióticos, lo que permitirá en un futuro tener enfoques terapéuticos y científicos, para así solucionar, mejorar y evitar problemas relacionados con la salud (AU)

Objective: this review aimed to update the information on oral bacterial dysbiosis and its effect on oral diseases. Material and methods: a detailed literature review was performed, where the search for articles began in 2014 with research papers related to the topic. Keywords were applied to facilitate and delimit the topic. The results obtained show specific information on bacterial dysbiosis and the problems and diseases they cause in the oral cavity. Conclusion: the oral cavity is a very complex and interactive ecosystem where a variety of habitats develop and establish relationships between microorganisms in different oral environments. Generally, the human body lives in symbiosis with these bacteria, this host-guest relationship is the product of years of evolution and coexistence to be able to tolerate these species and through years of research to determine the pathogens and symbiotics, which will allow in the future to have therapeutic and scientific approaches, to solve, improve and avoid health-related problems (AU)

Potentially multidrug-resistant non-fermentative Gram-negative pathogens causing nosocomial pneumonia.

Owing to its high morbidity and mortality, nosocomial pneumonia represents a particularly serious illness and one of the most frequent complications in ventilated patients admitted to the Intensive Care Unit. Gram-negative microorganisms, such as Pseudomonas aeruginosa, Acinetobacter baumannii and Stenotrophomonas maltophilia, are the most relevant pathogens responsible for particularly difficult-to-treat nosocomial pneumonia. The intrinsic resistance of these bacteria to many antimicrobial agents and, in addition, the variety of their increasingly recognised acquired resistance mechanisms make their management in the hospital setting problematic. Antimicrobials that retain the best activity against P. aeruginosa include carbapenems, piperacillin, cefepime, ceftazidime, ciprofloxacin and certain aminoglycosides, whilst carbapenems and sulphamethoxazole/trimethoprim remain the most active agents against A. baumannii and S. maltophilia, respectively. However, the growing emergence among these microorganisms of multidrug-resistant (MDR) isolates and the severity of associated infections call for potential alternative drugs. Sulbactam alone or in combination with ampicillin may represent an acceptable option for MDR A. baumannii as well as colistin, which also covers MDR P. aeruginosa. Newer fluoroquinolones and some tetracyclines may be alternative drugs both for MDR S. maltophilia and A. baumannii. However, large-scale controlled clinical trials are needed to confirm these promising therapeutic options.

Genetic characterization of RRS1, a recessive locus in Arabidopsis thaliana that confers resistance to the bacterial soilborne pathogen Ralstonia solanacearum.

The soilborne, vascular pathogen Ralstonia solanacearum, the causative agent of bacterial wilt, was shown to infect a range of Arabidopsis thaliana accessions. The pathogen was capable of infecting the Col-5 accession in an hrp-dependent manner, following root inoculation. Elevated bacterial population levels were found in leaves of Col-5, 4 to 5 days after root inoculation by the GMI1000 strain. Bacteria were found predominantly in the xylem vessels and spread systematically throughout the plant. The Nd-1 accession of A. thaliana was resistant to the GMI1000 strain of R. solanacearum. Bacterial concentrations detected in leaves of Nd-1, inoculated with an hrp+ strain of R. solanacearum, were only slightly higher than those detected in the susceptible accession, Col-5, following inoculation with a strain whose hrp gene cluster was deleted. Leaf inoculation of the GMI1000 strain on the resistant accession Nd-1 induced the formation of lesions in the older leaves of the rosette whereas the same strain of R. solanacearum provoked complete wilting of Col-5. Resistance to strain GMI1000 of R. solanacearum segregated as a simply inherited recessive trait in a genetic cross between Col-5 and Nd-1. F9 recombinant inbred lines generated between these two accessions were used to map a locus, RRS1, that was the major determinant of resistance between restriction fragment length polymorphism markers mi83 and mi61 on chromosome V. This region of the A. thaliana genome is known to contain many other pathogen recognition capabilities.

A regulatory locus, pehSR, controls polygalacturonase production and other virulence functions in Ralstonia solanacearum.

We previously identified a locus that regulates production of polygalacturonase (PG), an extracellular plant cell wall-degrading enzyme important in bacterial wilt of plants caused by Ralstonia (Pseudomonas) solanacearum. The DNA sequence of this locus, called pehSR, was determined and two consecutive open reading frames (ORFs) of 1,905 and 1,680 bp were identified. The amino acid sequences predicted to be encoded by these ORFs are similar to those of regulators of pilin synthesis in Pseudomonas aeruginosa and Myxococcus xanthus and to a regulator of flagellin synthesis and adhesion in P. aeruginosa, as well as to other two-component regulators of the NtrB/C subfamily. pehSR mutants produced negligible levels of endo-PG activity, while exo-PG activity was reduced by 50%. Northern (RNA) blot analysis showed that PehSR regulates endo-PG expression at the transcriptional level. pehSR mutants grew normally in culture and in planta but were dramatically reduced in virulence; this loss of virulence was substantially greater than that observed for endo-PG structural gene mutants, suggesting that pehSR regulates additional factors important in virulence. Although pehSR mutants were essentially nonmotile, like the wild-type strain, multiple copies of pehSR conferred motility on the bacterium. Reporter gene studies indicated that pehSR expression increased when bacteria grew in plant tissue, and that the pehSR locus was itself negatively regulated by the global virulence gene regulator PhcA.

PopP1, a new member of the YopJ/AvrRxv family of type III effector proteins, acts as a host-specificity factor and modulates aggressiveness of Ralstonia solanacearum.

A functional analysis of an 11-kb-long region of the genome of the plant-pathogenic bacterium Ralstonia solanacearum, previously identified as an alternative codon usage region (ACUR), reveals that it was probably acquired through horizontal gene transfer. This ACUR encodes an insertion sequence and eight potential proteins, one of which is partially homologous with a host-specificity factor from a plant-pathogenic Erwinia sp., and another, PopP1, which is homologous to members of the YopJ/AvrRxv family of type III-secreted bacterial effectors controlling interaction between bacteria and their hosts. The analysis of mutants affecting all except one of the genes identified in the ACUR showed that only the popP1-deficient strain had an altered phenotype in plant infection tests. This mutant strain became pathogenic to a Petunia line that is resistant to the wild-type strain. Therefore, popP1 behaves as a typical avirulence gene. We demonstrate that PopP1 protein is secreted and that secretion of this protein requires a functional type III-secretion pathway. In contrast to the structural genes for other type III-secreted proteins identified in R. solanacearum, transcription of the popP1 gene is not coregulated with transcription of hrp genes but is constitutive.

A signal transfer system through three compartments transduces the plant cell contact-dependent signal controlling Ralstonia solanacearum hrp genes.

Ralstonia solanacearum hrp genes encode a type III secretion system required for disease development in host plants and for hypersensitive response elicitation on non-hosts. hrp genes are expressed in the presence of plant cells through the HrpB regulator. This activation, which requires physical interaction between the bacteria and the plant cell, is sensed by the outer membrane receptor PrhA. PrhA transduces the plant cell contact-dependent signal through a complex regulatory cascade integrated by the PrhJ, HrpG, and HrpB regulators. In this study, we have identified two genes, named prhI and prhR, that belong to the hrp gene cluster and whose predicted products show homology with extracytoplasmic function sigma factors and transmembrane proteins, respectively. Strains carrying a mutation in prhIR show a delayed pathogenic phenotype toward host plants. PrhIR control the plant cell contact-dependent activation of hrp genes. prhIR gene expression is induced by a signal present in the plant cell coculture that is not PrhA-dependent. Genetic evidence shows that PrhIR act upstream of PrhJ in the regulatory cascade, likely transducing the signal sensed by PrhA through the periplasm as described for signal transfer systems through three compartments. This is the first report of such a surface signaling mechanism activating pathogenicity determinants in response to a nondiffusible plant cell wall signal.

Ectopic expression of Ralstonia solanacearum effector protein PopA early in invasion results in loss of virulence.

Ralstonia solanacearum OE1-1 (OE1-1) is pathogenic to tobacco. The type III-secreted effector protein popA of OE1-1 showed 97.6% identity to popA of R. solanacearum GMI1000, which is not pathogenic to tobacco. Reverse transcription-polymerase chain reaction analysis showed that popA in OE1-1 was expressed at 3 h after inoculation (HAI), but not before, in infiltrated-tobacco leaves. Pathogenicity analysis using a popABC operon-deleted mutant of OE1-1 (deltaABC) showed that popABC is not directly involved in the pathogenicity of OE1-1. When Papa, which constitutively expresses popA, was infiltrated into tobacco leaves, popA was expressed by 0.5 HAI. Papa could no longer multiply or spread in tobacco leaves and was no longer virulent. Moreover, the hypersensitive response (HR) and expression of HR-related genes were not induced in Papa-infiltrated leaves. Papa was also avirulent in a tobacco root-dipping inoculation assay. These results suggest that the expression of popA in Papa immediately after invasion triggers the suppression of bacterial proliferation and movement, resulting in loss of virulence. However, Papa retained its virulence when directly inoculated into xylem vessels. This result suggests that tobacco plants can recognize PopA when it is expressed early in disease development, and respond with an effective defense in the intercellular spaces.

Characterization of a Ralstonia solanacearum operon required for polygalacturonate degradation and uptake of galacturonic acid.

The bacterial wilt pathogen Ralstonia solanacearum produces three extracellular polygalacturonases (PGs): PehA, PehB, and PehC. All three PGs hydrolyze pectin's polygalacturonic acid backbone, but each releases different reaction products. PehA and PehB contribute significantly to pathogen virulence, probably by facilitating root invasion and colonization. To determine the collective contribution of PGs to virulence and saprophytic survival, we cloned, characterized, and mutated the R. solanacearum pehC gene, which encodes a distinctive monogalacturonate-releasing exo-PG. The virulence of a pehC mutant on tomato was indistinguishable from that of its wild-type parent; thus, this exo-PG alone does not contribute significantly to wilt pathogenesis. Unexpectedly, a completely PG-deficient triple pehA/B/C mutant was slightly more virulent than a pehA/B mutant. PehC may degrade galacturonide elicitors of host defense, thereby protecting the pathogen from plant antimicrobial responses. A galacturonate transporter gene, exuT, is immediately downstream of pehC and the two genes are co-transcribed. It has been hypothesized that galacturonic acid released by PGs from plant cell walls nourishes bacteria during pathogenesis. To separate the pectolytic and nutrient-generating roles of the PGs, we made an exuT mutant, which still produces all three isozymes of PG but cannot uptake PG degradation products. This exuT mutant had wild-type virulence on tomato, demonstrating that metabolism of galacturonic acid does not contribute significantly to bacterial success inside the plant.

Oral flora and pathogenic organisms.

Oral microbial flora consist of numerous bacterial taxa, ranging from aerobes through fastidious anaerobes, and fungi, viruses, and protozoa. Many of these bacteria are unique to the oral cavity. The organisms exist in a complex interrelationship that is regulated and maintained by physical and metabolic microbial interactions, and by environmental factors, such as saliva and diet. Many of these organisms are relatively harmless, although others are significant pathogens, producing local and systemic diseases in healthy and compromised individuals.

Ornithobacterium rhinotracheale, a primary pathogen in broilers.

Field strains of Ornithobacterium rhinotracheale were tested on their virulence in different chicken breeds. Ornithobacterium rhinotracheale was able to induce lesions after aerosol challenge without a previous priming with virus, and thus O. rhinotracheale was proven to be a primary pathogen. The virulence of Dutch strains, isolated between 1995 and 1998, did not increase, but the Dutch isolates and a South African strain were more pathogenic compared with an American strain of O. rhinotracheale. White specific-pathogen-free leghorns were less susceptible to O. rhinotracheale infection than broilers, whereas there was no difference in susceptibility between commercial broilers and specific-pathogen-free broilers.

Development, characterization, and preliminary evaluation of a temperature-sensitive mutant of Ornithobacterium rhinotracheale for potential use as a live vaccine in turkeys.

A temperature-sensitive (Ts) mutant strain of Ornithobacterium rhinotracheale (ORT) was developed after exposure of the wild-type organism to N-methyl-N'-nitro-N-nitrosoguanidine. The Ts mutant strain grew at 31 C but had its growth inhibited at 41 C unlike wild-type parent strain. The Ts mutant and parent strains were characterized. Morphologic and biochemical properties of wild-type and mutant strains did not show any differences. The strains were also characterized by polymerase chain reaction (PCR)-based fingerprinting methods. Results showed similar patterns in repetitive sequences by repetitive PCR (enterobacterial repetitive intergenic consensus, highly conserved repeated DNA elements present in Streptococcus pneumoniae (BOX), repetitive extragenic palindromic, and Salmonella enteritidis repetitive element primers); however, random amplified polymorphic DNA fingerprinting was able to differentiate mutant and parent strains showing a unique pattern for each of the ORT strains. The rationale for the use of a Ts strain as a vaccine is based on the ability of the mutant to colonize the upper respiratory tract but not the lower respiratory tract and systemic system of the birds, where the wild-type strain causes severe lesions. In a preliminary evaluation, Ts strain of ORT was recovered from tracheas and choanae of Ts-treated turkeys for 13 days postadministration of the strain either in drinking water or by oculonasal instillation. Humoral immune response was detected in Ts-vaccinated but not in control group birds after 3 wk postadministration. Results suggest that Ts strain of ORT has promising potential use as a live vaccine for ORT.

Minimization of pathologic changes in Ornithobacterium rhinotracheale infection in turkeys by temperature-sensitive mutant strain.

The protection elicited by a temperature-sensitive (Ts) mutant of Ornithobacterium rhinotracheale (ORT) vaccine against challenge with pathogenic strain was investigated. In Experiment 1, specific serologic response to ORT was detected in 12%-19% of Ts-vaccinated birds at 3 wk postvaccination by either drinking water or oculo-nasal instillation. At 7 days postchallenge, 100% of Ts-vaccinated turkeys of all groups were able to respond with an ORT-specific antibody response, but the control group was not, suggesting the potential of Ts strain to evoke immune protection. The study also revealed a statistically significant ability of the Ts strain to protect vaccinated turkeys against gross lesions caused by the pathogenic strain of ORT in treated groups vs. control. In Experiment 2, seroconversion was detected by enzyme-linked immunosorbent assay in birds after they were given the Ts strain in drinking water in field conditions. The results of the field study showed mean scores of gross lesions of nonvaccinated/challenged groups to be up to seven times higher than those of the vaccinated/challenged group. In addition, reisolation rates and quantification of ORT colonies per gram of lung tissue were significantly lower for vaccinated/challenged than for nonvaccinated/challenged turkeys. In conclusion, results from laboratory and field experiments suggest that use of the Ts mutant strain of ORT as a live vaccine would be a suitable method to evoke protection against ORT infection in turkeys.

Characterization of nonfermenters from clinical samples.

OBJECTIVE: Nonfermenters are a group of aerobic non sporing gram-negative bacilli found primarily free in nature and as commensals, whose pathogenic potentials are well established. The current study was conducted to assess the role of these nonfermenters in various infections and to characterize these isolates. METHODS: One hundred nonfermenters isolated from various clinical specimens were grouped according to Weaver-Hollis scheme based on growth on MacConkeys agar, oxidase activity and oxidation/fermentation of glucose. Species level identification was attempted based on a battery of biochemical tests. All isolates were then subjected to antimicrobial sensitivity. RESULTS: Majority of the isolates were encountered from pus and urine (50%). These isolates belonged to six of the seven Weaver-Hollis groups. Fifty six per cent of the isolates belonged to genus Pseudomonas. Multidrug resistance with resistance to more than three antimicrobials was frequently seen. Amikacin and ciprofloxacin were found to be most effective. CONCLUSION: Nonfermenting gram negative organisms are responsible for variety of infective conditions. Amongst them genus Pseudomonas and Acinetobacter calcoaceticus were more frequently encountered. Amikacin or ciprofloxacin (for nonfermenters other than Pseudomonas) appears to be the drug of choice for treatment of such infections.

[The chemical composition and biological activity of the glyco polymers in Ralstonia solanacearum (Yabuchi et al., 1995)]. / Khimicheskii sostav i biologicheskaia aktivnost' glikopolimerov Ralstonia solanacearum (Yabuchi et al., 1995).

Lipopolysaccharide and extracellular glyco polymers were isolated from cells of phytopathogenic bacteria Ralstonia solanacearum. It was established that the O-specific polysaccharides are characterized by a linear structure, composed of tetrasaccharide repeating units containing three L-rhamnose residues and one of N-acetylglucosamine residue. Core oligosaccharide along with typical monosaccharides such as rhamnose, glucose, heptose, KDO and glucosamine included fucose, galactose and arabinose. Serological activity of lipopolysaccharide is due to both O-specific polysaccharide and lipid A component. Extracellular glyco polymers contained both neutral (GP 1) and charged (GP 2 and GP 3) components. Rhamnose and glucose (GP 1, GP 2) or galactose (GP 3) were predominant monosaccharides, GP 2 displayed a high phytotoxic action in respect to tomato plants.

Endocarditis infecciosa por bacilos gram negativos no HACEK. Experiencia en un centro de alta complejidad de la República Argentina (1998-2016) / Infective endocarditis due to non-HACEK gram-negative bacilli in a Level III cardiovascular center in Argentina (1998-2016)

Los bacilos gram negativos (BGN) que no pertenecen al grupo HACEK son una causa infrecuente de endocarditis infecciosa. Los aspectos epidemiológicos, diagnósticos y pronósticos de esta entidad son poco conocidos y la experiencia aún es limitada. Nuestros objetivos fueron analizar las características clínicas y microbiológicas de las endocarditis infecciosas (EI) por BGN no HACEK diagnosticadas en un centro de alta complejidad de Argentina en el período 1998-2016 y conocer su evolución hospitalaria, a fin de compararlas con las EI debidas a otros microorganismos.

Non-HACEK Gram-negative bacilli are a rare cause of infective endocarditis. Epidemiological, diagnostic and prognostic aspects of this entity are little known, and there is limited experience. The aim of this study was to analyze the clinical, microbiological and in-hospital outcomes of non-HACEK Gram negative bacilli endocarditis and to compare them with those due to other microorganisms.

¿Cuál es el nivel de contaminación del cepillo de dientes almacenado en diferentes entornos sanitarios? / What is the level of toothbrush contamination stored in different sanitary settings?

Introducción: Los cepillos pueden albergar una amplia variedad de microorganismos, incluyendo bacterias hongos y virus, pudiendo así facilitar la translocación de especies en un mismo individuo y la transmisión de especies entre individuos. Métodos: Estudio de la contaminación bacteriana de los cepillos de dientes de cien voluntarios con la cumplimentación de un cuestionario (lugar de almacenamiento, tipo de cepillo, utilización de estuche de almacenamiento y meses de uso). Resultados: Se estudiaron un total de 100 muestras. El 33% guardaba el cepillo fuera del baño, un 20% lo guardaba en el cajón del baño y un 47% sobre el lavabo del baño. El 92% de las muestras estaban contaminadas como mínimo con un grupo de microorganismos Conclusión: El lugar de almacenamiento del cepillo de dientes es fundamental en la reducción de la contaminación. Se debe guardar en un lugar seco, lejos del inodoro y sin estuche

Introduction: Brushes can house a wide variety of microorganisms, including fungal bacteria and viruses, which can facilitate the translocation of species in the same individual and the transmission of species between individuals. Methods: Study of the bacterial contamination of toothbrushes of one hundred volunteers with the completion of a questionnaire (place of storage, type of brush, use of storage case and months of use). Results: A total of 100 samples were studied. 33% kept the brush outside the bathroom, 20% kept it in the bathroom drawer and 47% on the bathroom sink. 92% of the samples were contaminated with at least one group of microorganisms. Conclusion: The storage place of the toothbrush is fundamental in the reduction of contamination. It should be stored in a dry place, away from the toilet and without a box

Resistencia antimicrobiana en bacilos gramnegativos: una amenaza actual y global / Antimicrobial resistance in Gram-negative bacilli: a current and global threat

La resistencia a los antimicrobianos se ha incrementado de manera preocupante en los bacilos gramnegativos. La dispersión de clones de alto riesgo multirresistentes con determinantes genéticos responsables de la producción de betalactamasas de espectro extendido y, más recientemente, de carbapenemas ha reducido notablemente las alternativas terapéuticas. En España es preocupante la dispersión de las enterobacterias productoras de carbapenemasas de tipo OXA-48 y KPC. Se ha notificado el hallazgo de aislados de Klebsiella pneumoniae con KPC de clones similares a los descritos en Italia, con resistencia a la colistina por mutaciones en los sistemas que afectan a la estructura del lipopolisacárido. En Pseudomonas aeruginosa y Acinetobacter baumannii, las tasas de aislados multirresistentes son similares a las de los países de nuestro entorno y se han detectado clones de alto riesgo con carbapenemasas. Recientemente se ha descrito el gen mcr-1 en Escherichia coli y K. pneumoniae asociado a plásmidos que presentan genes de betalactamasas de espectro extendido y de carbapenemasas. También preocupa el posible incremento de la resistencia a la fosfomicina en E. coli, que se está produciendo asociado a genes tipo fosA ligados a plásmidos y que podrían limitar el uso futuro de este antimicrobiano. El llamamiento de la Organización de las Naciones Unidas a la lucha unificada de los distintos estados miembros frente a la resistencia debe impulsar el desarrollo de nuevos antimicrobianos y la puesta en marcha a nivel local de los planes de contención de la resistencia (AU)

Antimicrobial resistance has dramatically increased in gram-negative bacilli. The dispersion of multiresistant high-risk clones with genetic determinants responsible for the production of extended spectrum beta-lactamases (ESBL) and, more recently, carbapenemases has markedly reduced current therapeutic alternatives. In Spain, the dispersion of OXA-48 and KPC carbapenemase-producing enterobacteria (EPC) is worrisome. KPC producing Klebsiella pneumoniae clones with resistance to colistin similar to those described in Italy has been reported in our country. Resistance mechanisms include mutations affecting the lipopolysaccharide structure. In Pseudomonas aeruginosa and Acinetobacter baumannii the rates of multiresistant isolates are similar to those in surrounding countries and high-risk clones with carbapenemases within these organisms have been detected. Recently, the mcr-1 gene has been described in Escherichia coli and K. pneumoniae associated with plasmids presenting ESBL and carbapenemase genes. Moreover, there is also concern about the potential increase of fosfomycin resistance in E. coli. This resistance has been associated with plasmid-mediated fosA-like gene and might limit future use of this antimicrobial. The high-level meeting of the United Nations celebrated with the aim that all member states fight against antimicrobial resistance must include promotion of the development of new antimicrobials and the implementation of resistance containment plans at the local level (AU)

Rol de las formas cocoides de Helicobacter pylori en la infección y la recrudescencia / Role of Helicobacter pylori coccoid forms in infection and recrudescenc

Helicobacter pylori es un bacilo espiral gramnegativo que coloniza el estómago humano y desempeña un papel clave en la patogénesis de diferentes enfermedades gastroduodenales. Sin embargo, cuando se expone a condiciones de estrés ambientales, tales como el aumento de la tensión de oxígeno, la incubación prolongada o la exposición a antibióticos, Helicobacter pylori entra en un estado viable pero no cultivable, en el cual la bacteria modifica su morfología de una forma bacilar a una cocoide como manifestación de adaptación celular a estas condiciones adversas. En el tejido gástrico, las formas cocoides viables pueden permanecer latentes durante mucho tiempo y retener factores de virulencia, por lo que estas formas posiblemente puedan contribuir a los fracasos del tratamiento y la recurrencia de la infección y de las enfermedades gastroduodenales también. En esta revisión se discutirán varios aspectos de la adaptación celular y supervivencia de Helicobacter pylori, la susceptibilidad a los antibióticos y la virulencia de las formas cocoides y su participación en la recrudescencia

Helicobacter pylori is a spiral Gram-negative bacillus, which colonizes the human stomach and plays a key role in the pathogenesis of a number of gastroduodenal diseases. However, when expose to environmental stressed conditions, such as increased oxygen tension, extended incubation and exposure to antibiotics, Helicobacter pylori is able to entering the viable but nonculturable state, in which the bacterium modifies its morphology from a spiral to coccoid form, as a manifestation of cell adaptation to these adverse conditions. In gastric tissues, viable coccoid forms may remain latent for long time and retain virulence factors, so these forms possibly contribute to the treatment failures and recurrence of Helicobacter pylori infection and gastroduodenal diseases as well. In this review, we will discuss several aspects of cellular adaptation and survival of Helicobacter pylori, antibiotic susceptibility and virulence of coccoid forms and its involvement with recrudescence

Pink-pigmented non-fermentative gram-negative rods associated with human infections: a clinical and diagnostic challenge.

Over the past several decades, the appearance of pink-pigmented bacteria in clinical specimens has gone from being a microbiologic curiosity in the clinical laboratory to the recognition of these aerobic microorganisms as etiologic agents of human disease, most notably bloodstream infections. Advances in the fields of molecular taxonomy and phylogenetics indicate that at least four distinct genera and eight different species are associated with clinical infections in susceptible patient populations. However, these bacteria are slow growing and present multiple diagnostic challenges to the microbiology laboratory including culture, isolation, and identification to species rank. This article provides a current review of these unusual non-fermentative chromogenic bacteria including their disease spectrum, taxonomy, and laboratory identification. The review also highlights the pitfalls or shortcomings we currently have in our knowledge of these microbes and their disease-producing capabilities.