Colistin is one of the last-resort therapeutic agents to combat multidrug-resistant Gram-negative bacteria (GNB) including Klebsiella pneumoniae. Although it happens rarely, resistance to colistin has been reported for several GNB. A total of 20 colistin resistant (col-R) and three colistin susceptible (col-S) clinical isolates of K. pneumoniae were studied to explore the underlying mechanisms of colistin resistance. The presence of plasmid encoded resistance genes, mcr-1, mcr-2, mcr-3, and mcr-4 genes were examined by PCR. The nucleotide sequences of pmrA, pmrB, phoP, phoQ, and mgrB genes were determined. To evaluate the association between colistin resistance and upregulation of pmrHFIJKLM and pmrCAB operons, transcriptional level of the pmrK and pmrC genes encoding for lipopolysaccharide target modifying enzymes was quantified by RT-qPCR analysis. None of the plasmid encoded resistance genes were detected in the studied isolates. Inactivation of MgrB due to nonsense mutations and insertion of IS elements was observed in 15 col-R isolates (75%). IS elements (IS5-like and IS1-like families) most commonly targeted the coding region and in one case the promoter region of the mgrB. Complementation with wild-type MgrB restored colistin susceptibility in isolates with altered mgrB. All col-R isolates lacked any genetic alterations in the pmrA, phoP, and phoQ genes and substitutions identified in the pmrB were not found to be involved in resistance conferring determined by complementation assay. Colistin resistance linked with upregulation of pmrHFIJKLM and pmrCAB operons with the pmrK and pmrC being overexpressed in 20 and 11 col-R isolates, respectively. Our results demonstrated that MgrB alterations are the major mechanisms contributing to colistin resistance in the tested K. pneumoniae isolates from Iran.

ObjectivesAcinetobacter baumannii is a bacterium responsible for health care-associated infections, and it frequently develops multiple drug resistance (MDR). The prevalence of antibiotic-resistant A. baumannii in Iran has increased, and this may cause significant clinical problems. Therefore, in order to elucidate the development of antibiotic resistance, we performed a systematic review of the literature published on antibiotic-resistant A. baumannii reported in Iran.MethodsThirty-six publications that met the criteria for inclusion were reviewed from an initial 87 papers. Selected papers published between 2008 and September 2014, were categorized on the basis of the sample collecting year been between 2001 and 2013.ResultsAnalysis of data revealed that, in general, there was an increase in antimicrobial resistance. During the initial time point of these studies (2001–2007) there was a high rate of resistance to all antibiotics, with the exception of carbapenems, lipopeptides, and aminoglycosides that had a low resistance rate in comparison with the others. Also, the resistance rate was increased in one group of these three antimicrobial groups from 2010 to 2013. In particular, there was an increase in resistance to carbapenems (imipenem and meropenem) from 2010–2011 and 2012–2013, whereas no significant change in the resistance rate of the other two antimicrobial groups (lipopeptides and aminoglycosides) during the study time was observed, although we did observe certain trends in amikacin (aminoglycoside group antibiotic) between 2011–2012 and 2012–2013.ConclusionThese findings indicate that antimicrobial resistance of A. baumannii in Iran has increased, which may very well affect the antimicrobial resistance of this organism worldwide. Based on these results, novel prevention and treatment strategies against A. baumannii infections are warranted. Furthermore, these data may assist in revising treatment guidelines and regional policies in care units to slow the emergence of antimicrobial resistance.

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Listeria monocytogenes is a human pathogen causing serious diseases. We aimed to determine food contamination with Listeria spp. in Kermanshah, Islamic Republic of Iran. Samples (185 dairy, 187 meat products and 158 ready-to-eat foods such as salads) were randomly collected from markets. After processing, samples were cultured in half-Fraser and Fraser broth followed by cultivation on PALCAM and Oxford media. Confirmatory tests including carbohydrate utilization were performed on isolates to determine species. Bacteria were isolated from 66/530 samples (12.5%). Meat products showed the highest (27.2%) and dairy products the lowest (3.8%) contamination rates. L. innocua was found in 56 (10.6%) samples, but L. monocytogenes was only found in 3 samples (0.6%). The results indicate that the rate of contamination with L. monocytogenes, even for ready-to-eat foods, was low but for other Listeria spp., in particular strains of L. innocua, the rate of contamination was higher, suggesting that more control on food sanitation is required. RÉSUMÉ Listeria monocytogenes est un agent pathogène humain à l'origine de maladies graves. Nous avons cherché à établir la prévalence de la contamination alimentaire par Listeria spp. à Kermanshah (République islamique d'Iran). Des échantillons (185 produits laitiers, 187 produits carnés et 158 plats prêts à consommer, comme des salades) ont été collectés au hasard sur les marchés. Après traitement, les échantillons ont été mis en culture dans un bouillon de Fraser-demi et de base Fraser puis repiqués sur gélose PALCAM et en milieu Oxford. Des tests de confirmation, y compris l'utilisation des glucides, ont été réalisés sur des isolats afin de déterminer l'espèce. Des bactéries ont été isolées dans 66 échantillons sur 530 (12,5 %). Les produits carnés étaient les plus fréquemment contaminés (27,2 %) tandis que les produits laitiers étaient les moins fréquemment contaminés (3,8 %). L. innocua a été identifiée dans 56 échantillons (10,6 %), alors que L. monocytogenes n'a été retrouvée que dans trois échantillons (0,6 %). Ces résultats indiquent que le taux de contamination par L. monocytogenes, même dans les plats prêts à consommer, était faible, mais que pour les autres Listeria spp., en particulier les souches de L. innocua, le taux de contamination était plus élevé, suggérant qu'un contrôle plus strict de l'hygiène alimentaire est requis.‫املتوسط‬ ‫لرشق‬ ‫الصحية‬ ‫املجلة‬ ‫عرش‬ ‫التاسع‬ ‫املجلد‬ ‫اخلامس‬ ‫العدد‬ 475