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Acquired carbapenemases are emerging resistance determinants in Gram-negative pathogens, including Enterobacteriaceae, Pseudomonas aeruginosa and other Gram-negative non-fermenters. A consistent number of acquired carbapenemases have been identified during the past few years, belonging to either molecular class B (metallo-beta-lactamases) or molecular classes A and D (serine carbapenemases), and genes encoding these enzymes are associated with mobile genetic elements that allow their rapid dissemination in the clinical setting. Therefore, detection and surveillance of carbapenemase-producing organisms have become matters of major importance for the selection of appropriate therapeutic schemes and the implementation of infection control measures. As carbapenemase production cannot be simply inferred from the resistance profile, criteria must be established for which isolates should be suspected and screened for carbapenemase production, and for which tests (phenotypic and/or genotypic) should be adopted for confirmation of the resistance mechanism. Moreover, strategies should be devised for surveillance of carbapenemase producers in order to enable the implementation of effective surveillance programmes. The above issues are addressed in this article, as a follow-up to an expert meeting on acquired carbapenemases that was recently organized by the ESCMID Study Group for Antibiotic Resistance Surveillance.

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OBJECTIVES: To report cases of culture-proved Acanthamoeba keratitis in Greece over a 10-year period and to evaluate the effectiveness of the commonly used commercial contact lens disinfecting systems in clinical cases of Acanthamoeba keratitis. MATERIAL AND METHODS: During the years 1994-2004, 45 contact lens wearers and 3 non-contact lens wearers presenting with symptoms and signs of keratitis underwent corneal sampling. The scrapings obtained were inoculated directly onto appropriate culture media for bacteria, fungi and Acanthamoeba. All proved positive for Acanthamoeba. The contact lenses and contact lens disinfecting solutions (16 one-step 3% hydrogen peroxide and 3 multipurpose solutions) of 19/45 patients with culture-proven Acanthamoeba keratitis were cultured for bacteria, fungi and Acanthamoeba. RESULTS: Acanthamoeba was isolated from contact lenses and contact lens disinfecting solutions in all 19 cases of Acanthamoeba keratitis studied. CONCLUSIONS: The main risk factor for corneal infection in contact lens wearers is the use of contact lens disinfecting systems ineffective at killing Acanthamoeba cysts and trophozoites, as well as bacteria and fungi. Improvement or development of new contact lens disinfecting systems by manufacturers is needed to prevent Acanthamoeba keratitis.

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Amoebae belonging to the genus Acanthamoeba are potentially pathogenic to humans, causing mainly amoebic keratitis. Pathogenic ability of the 15 known Acanthamoeba genotypes is under investigation. We report that four out of five cases of amoebic keratitis studied in Greece, present T4 sequence type, while the remaining one presents T5 sequence type (Acanthamoeba lenticulata), which is the second most frequent genotype found among environmental samples. Thus, it is confirmed, for the first time to our knowledge, that A. lenticulata can cause keratitis. However the reason that it is under represented in clinical samples compared to environmental ones is unknown.

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The oropharyngeal and nasopharyngeal microbial flora of 40 children with chronically hypertrophied and infected tonsils or adenoids, was studied. Twenty of the children were treated by tonsillectomy and 20 by adenoidectomy. Swabs were taken from the surgical field pre-operatively and from the oropharynx or the nasopharynx 10 and 30 days-post-operatively. The swabs were cultured on suitable culture media and identification as well as quantitative estimation of the isolated bacteria, was carried out. Most of the potentially pathogenic bacteria exhibited beta-lactamase production. Interestingly, after surgical treatment, the respective microorganisms were quantitatively reduced and it was observed that their isolation rate was also lower. Furthermore, bacteria considered as normal inhabitants regularly showed an increase in their frequency of isolation despite the fact that a quantitative decrease was in some instances observed. These findings suggest that tonsillectomy and adenoidectomy result in an alteration to the abnormal oropharyngeal and nasopharyngeal microbial flora producing an almost normal one. It appears that, in cases of the failure of antimicrobial treatment, surgical procedures should be seriously considered.

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