Microcins are low-molecular-weight compounds produced and excreted by Enterobacteriaceae. They inhibit the growth of a wide spectrnm of microorganisms. Microcin-synthesizing transconjugants were obtained in seven out of eight experiments of conjugational transfer between wild-type microcinogenic strains of Escherichia coli and E. coli strain BM21. The physical analysis of one of the transconjugant strains that has acquired the ability to produce microcin 17 showed the presence of extrachromosomal DNA as a plasmid (pRYC17) of molecular weight 36 x 106 (18.3-,um length), which is absent in the "microcincured" derivative strain. pRYC17 was incompatible with plasmids of the IncFII group. Other suspected plasmids containing the information for the synthesis of microcins have not been clearly classified. Strains producing microcins 93, 136, and 140 show a partial incompatibility with IncFIM group of plasmids.

ObjectivesImplant-related infection is one of the most devastating complications in orthopaedic surgery. Many surface and/or material modifications have been developed in order to minimise this problem; however, most of the in vitro studies did not evaluate bacterial adhesion in the presence of eukaryotic cells, as stated by the ‘race for the surface’ theory. Moreover, the adherence of numerous clinical strains with different initial concentrations has not been studied.MethodsWe describe a method for the study of bacterial adherence in the presence of preosteoblastic cells. For this purpose we mixed different concentrations of bacterial cells from collection and clinical strains of staphylococci isolated from implant-related infections with preosteoblastic cells, and analysed the minimal concentration of bacteria able to colonise the surface of the material with image analysis.ResultsOur results show that clinical strains adhere to the material surface at lower concentrations than collection strains. A destructive effect of bacteria on preosteoblastic cells was also detected, especially with higher concentrations of bacteria.ConclusionsThe method described herein can be used to evaluate the effect of surface modifications on bacterial adherence more accurately than conventional monoculture studies. Clinical strains behave differently than collection strains with respect to bacterial adherence.Cite this article: M. Martinez-Perez, C. Perez-Jorge, D. Lozano, S. Portal-Nuñez, R. Perez-Tanoira, A. Conde, M. A. Arenas, J. M. Hernandez-Lopez, J. J. de Damborenea, E. Gomez-Barrena, P. Esbrit, J. Esteban. Evaluation of bacterial adherence of clinical isolates of Staphylococcus sp. using a competitive model: An in vitro approach to the “race for the surface” theory. Bone Joint Res 2017;6:315–322. DOI: 10.1302/2046-3758.65.BJR-2016-0226.R2.

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We present the first two cases of Kingella kingae keratitis in adults. This species is a rare isolate from ophthalmic samples for which final identification was obtained with matrix-assisted laser desorption ionization-time of flight mass spectrometry. One of the patients recovered uneventfully with topical therapy. Results from the second patient cannot be confirmed as he was lost to follow-up. CASE REPORTSW e present two cases of Kingella kingae keratitis who presented to the Ophthalmology Department of the Fundación Jiménez Díaz-the first in November 2010 and the second in February 2012.The first case was a 38-year-old woman who presented with redness in the left eye and pain over 2 days. She had no relevant medical history or underlying diseases. The patient had been wearing monthly contact lenses for 5 years. An ophthalmological examination revealed mixed hyperemia and a paracentral corneal infiltrate (1 by 1 mm) in the bottom of the left eye, which was able to be stained with fluorescein.Following corneal scraping, empirical treatment was started with topical moxifloxacin and tobramycin. Nineteen days after starting treatment, an anterior segment examination revealed no abnormalities.The second patient was a 45-year-old HIV-positive male who had experienced pain and redness in the left eye for 2 weeks. The patient did not use contact lenses but reported having used Moroccan kohl as eye makeup. An ophthalmological examination using fluorescein staining revealed an inferior peripheral corneal infiltrate (1.5 by 1.5 mm) associated with hyperemia. He was then treated empirically with topical vancomycin and ceftazidime. Therapy was changed to topical gentamicin and ciprofloxacin when susceptibility results were available. The outcome of the corneal ulcer is unknown, because the patient was lost to follow-up.Corneal scrapings of both patients were collected and sent to the microbiology service for microscopy and culture using an identical protocol. This protocol consists of direct Gram staining of the sample and plate onto chocolate agar (bioMérieux, Marcy l'Etoile, France) and tryptic soy blood agar (bioMérieux, Marcy l'Etoile, France) and incubating both at 37°C in 5% CO 2 . In the first case, Gram staining revealed an absence of microorganisms, but in the second case, Gram-negative coccobacilli were detected. After 72 h (case 1) and 24 h (case 2) of incubation, growth of smooth, mucous, and beta-hemolytic colonies was detected. Both were pure cultures. Gram staining of the colonies showed Gramnegative coccobacilli arranged in pairs or clusters. The isolates had facultative anaerobic respiration, and their growth was increased by a CO 2 atmosphere.Biochemical tests gave a presumptive identification of the organisms as Kingella kingae. The biochemical characteristics of both K. kingae isolates from the corneal ulcers were the production of acid from glucose and maltose and the fact that the isolates were phosphatase alkaline positive, oxidase positive, and catalase negative (1).The presumptive identification wa...

Prosthetic joint infection (PJI) is an increasingly important health concern in the Western world due to the rising number of joint arthroplasties. Although most infections are considered to be monomicrobial, the introduction of sonication procedures has led to an increase in the detection of polymicrobial infections. To date, no published studies have investigated the presence of different clones of the same species in the infected patient. The objective of this study was to analyze whether the phenomenon of polyclonality, or the appearance of different clones in the same sample, occurs in PJI. Bacteria isolated by sonication of the retrieved implant from patients with theoretically monomicrobial PJI were included in the study. Two techniques (random amplified polymorphic DNA [RAPD] and matrix-assisted laser desorption ionization-time of flight [MALDI-TOF] mass spectrometry) were used to determine the presence of several clones in the same sample. Results were analyzed to determine bacterial species and infection type (acute versus chronic). RAPD showed a predominance of polyclonal cases (16 of 19). However, when performing the analysis with MALDI-TOF, all cases were shown to be polyclonal. We were unable to establish any relationship between the two methodologies. Polyclonality is a common phenomenon in acute and chronic PJI. Further studies are needed to establish the potential implications of this phenomenon on patient outcomes. P rosthetic joint replacement, or arthroplasty, is a surgical procedure that has improved the quality of life for many people around the world, providing pain relief and improved functionality to limbs (1-3). However, 10% of all patients who undergo this operation develop complications at some point in their lives; although it is not the most common, infection is one of the most significant of these complications, having an incidence of 1% to 3% (1, 3, 4). The microorganisms that cause most cases of prosthetic joint infection (PJI) are those belonging to the genus Staphylococcus (60% of cases), of which infections caused by Staphylococcus aureus constitute 25%. Gram-negative organisms (Enterobacteriaceae, Pseudomonas aeruginosa, and other species) represent a smaller proportion of cases (10%) (1, 2, 5). Notably, up to 20% to 25% of PJIs are polymicrobial infections (1-3).When the growth conditions of the bacteria causing PJI become hostile, as may occur during antibiotic therapy, a coping mechanism known as spontaneous random hypermutation occurs as the bacteria attempt to overcome the unfavorable environment (6). This results in the development of polyclonality or the appearance of different clones in the same sample or environment (6). Polyclonality can also occur when the patient is infected with different clones from the same section of skin, which may occur either during surgery or afterwards and is likely a more common phenomenon (7). Several reports have found polyclonality in monomicrobial infections among isolates of small-colony variant staphylococci, which present phenotyp...

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