Characterization of colistin-resistant A. baumannii isolated in Intensive Care Unit of an Italian Hospital

We report the characterization of an Acinetobacter baumannii resistant to colistin isolated from a patient treated with colistin for 22 days. The identification and initial susceptibility testing of the strain was performed at ASL3 Imperiese with the Vitek-2 automated system and than the strain was re-identified at the Sezione di Microbiologia with APINE. In vitro activity of antimicrobial agents was determined by the microdiluition methods. The detection of the beta-lactamase gene was performed by PCR and for the analysis of LPS were sequenced the genes of the PmrABC system. We compared the PFGE profile of the colistin-resistant A. baumannii with 5 A. baumannii colistin-susceptible strains isolated in the same Hospital during 2010. The strain was resistant to all antimicrobial agents tested, except to tygecyclin. The PFGE shown that the A. baumannii colistin-resistant was closery related to the colistin-susceptible strains. The sequencing of the PmrABC system showed that the strain had a single mutation in the PmrB component. Colistin-resistant strain have recently been found in several Gram-negative bacteria such A. baumannii, K. pneumoniae and P. aeruginosa. This clinical case confirms that resistance to colistin in A. baumannii can be selected in vivo following the use of colistin in therapy

Comparative Analysis of Five Multiplex RT-PCR Assays in the Screening of SARS-CoV-2 Variants

The rapid and presumptive detection of SARS-CoV-2 variants may be performed using multiplex RT-PCR assays. The aim of this study was to evaluate the diagnostic performance of five qualitative RT-PCR tests as compared with next-generation sequencing (NGS). We retrospectively examined a multi-variant panel (n = 72) of SARS-CoV-2-positive nasopharyngeal swabs categorized as variants of concern (Alpha, Beta, Gamma and Delta), variants under monitoring (Iota and Kappa) and wild-type strains circulating in Liguria (Italy) from January to August 2021. First, NGS libraries of study samples were prepared and mapped to the reference genome. Then, specimens were screened for the detection of L452R, W152C, K417T, K417N, E484Q, E484K and N501Y mutations using the SARS-CoV-2 Variants II Assay Allplex, UltraGene Assay SARS-CoV-2 452R & 484K & 484Q Mutations V1, COVID-19 Ultra Variant Catcher, SARS-CoV-2 Extended ELITe MGB and Simplexa SARS-CoV-2 Variants Direct. The overall accuracy of these assays ranged from 96.9% to 100%. Specificity and sensitivity were 100% and 96-100%, respectively. We highly recommend the use of these assays as second-level tests in the routine workflow of SARS-CoV-2 laboratory diagnostics, as they are accurate, user friendly, low cost, may identify specific mutations in about 2-3 h and, therefore, optimize the surveillance of SARS-CoV-2 variants

Epidemiological study of pathogens isolated from blood in Liguria during 2011

Objectives. An epidemiological study addressed to identify the most represented pathogens isolated from blood and to evaluate their antibiotic susceptibility patterns, was conducted. Methods. Five clinical microbiology laboratories, homogenously distributed in Liguria, were required to collected all consecutive non-duplicates strains isolated from blood cultures during March 2011 to May 2011. the strains were sent to the reference laboratory (Section of Microbiology, DISC, University of Genoa, Italy). Results. A total of 159 microorganisms were enrolled, including 81 Gram positive, 69 Gram negative and 9 fungi.The most represented pathogens were: Escherichia coli (35), Staphylococcus aureus (26), S. epidermidis (20), S. hominis (10). Samples were collected mainly from medicine (59 isolates).Among the staphylococci, the most active molecules were: vancomycin (100% of susceptible strains), teicoplanin (93.4%), trimethoprim-sulfamethoxazole (83.8%) and tobramycin (61.6%). Enterococci showed rates of resistance to vancomycin of 25%. Enterobacteriaceae exhibited resistance to ampicillin (76.9%), ceftriaxone (44.4%), ciprofloxacin (43.3%), trimethoprim-sulfamethoxazole (36.6%) and ceftazidime (32.2%). Conclusions. The data show a higher incidence of Gram positive (51%) in comparison to Gram negative (43.4%). Gram-positive strains showed a high resistance level to fluoroquinolones (92.3%) while Gram-negative resulted resistant to ceftriaxone (44.4%) and fluoroquinolone (43.3%)

Epidemiological study of pathogens isolated from blood in Liguria (January-April 2010)

Objectives. An epidemiological study to identify the most represented pathogens isolated from blood and to evaluate their antibiotic susceptibility patterns, was conducted. Methods. Seven clinical microbiology laboratories, homogeneously distributed in the Ligurian area,were required to collected all consecutive non-duplicates strains isolated froom blood cultures during January 2010 to April 2010. The strains were sent to the reference laboratory (Sezione di Microbiologia del DISC, University of Genoa, Italy). Results. A total of 277 microorganisms were enrolled, including 155 Gram positive and 122 Gram negative.The most represented pathogens were: Escherichia coli (68), Staphylococcus aureus (57), Staphylococcus epidermidis (32), Staphylococcus hominis (17), Pseudomonas aeruginosa (15), Klebsiella pneumoniae (15), Enterococcus faecalis (11). Samples were collected mainly from medicine (66, 33.3%, of this number was determined by E. coli), intensive care units (33, 18.2% of this number consisted of S. epidermidis), surgery (24, 33.3% consisted of E. coli) and infectious diseases (20, of which S. aureus, E. coli and S. epidermidis equally represented 20.0%).Among the Staphylococci the most active molecules were: vancomycin and teicoplanin (100% of susceptible strains), chloramphenicol (92.3%) and trimethoprim-sulfamethoxazole (89.8%). Among the OXA-R Staphylococci (81/123, 65.9%) the most active molecules were: vancomycin and teicoplanin (100% of susceptible strains), chloramphenicol (93.8%) and trimethoprim-sulfamethoxazole (84.8%). Enterococci showed rates of resistance to vancomycin of 5.9%. Enterobacteriaceae exhibited resistance to ampicillin (77.5%), trimethoprim-sulfamethoxazole (42.6%), ciprofloxacin (41.2%), ceftriaxone (37.5%), ceftazidime (28.2%), cefepime (26.7%), cefoxitin (22.1%), piperacillintazobactam (20.4%), imipenem (4.7%) and amikacin (2.9%). The Gram negative non-Enterobacteriaceae showed rates of resistance of 100% to ceftriaxone, 81.3% to trimethoprim-sulfamethoxazole, 42.1% to ciprofloxacin and piperacillin-tazobactam, 33.3% to ceftazidime, 31.6% to cefepime, 27.8% to imipenem, 26.3 % to amikacin. Conclusions. The data show a higher incidence of Gram positive (56%) in comparison to Gram negative (44%).This confirms the high incidence of oxacillino-resistance in Staphylococci in our geographic area.Against Enterobacteriaceae rates of resistance were observed in excess of 20% for all drugs tested except imipenem (4.7%) and amikacin (2.9%). The proportion of imipenem-resistant isolates was constituted of strains of K. pneumoniae carbapenemase producers

Epidemiological study of pathogens collected from blood for a period of a year (2008-2009)

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Characterization of colistin-resistant A. baumannii isolated in Intensive Care Unit of an Italian Hospital

We report the characterization of an Acinetobacter baumannii resistant to colistin isolated from a patient treated with colistin for 22 days. The identification and initial susceptibility testing of the strain was performed at ASL3 Imperiese with the Vitek-2 automated system and than the strain was re-identified at the Sezione di Microbiologia with APINE. In vitro activity of antimicrobial agents was determined by the microdiluition methods. The detection of the beta-lactamase gene was performed by PCR and for the analysis of LPS were sequenced the genes of the PmrABC system. We compared the PFGE profile of the colistin-resistant A. baumannii with 5 A. baumannii colistin-susceptible strains isolated in the same Hospital during 2010. The strain was resistant to all antimicrobial agents tested, except to tygecyclin. The PFGE shown that the A. baumannii colistin-resistant was closery related to the colistin-susceptible strains. The sequencing of the PmrABC system showed that the strain had a single mutation in the PmrB component. Colistin-resistant strain have recently been found in several Gram-negative bacteria such A. baumannii, K. pneumoniae and P. aeruginosa. This clinical case confirms that resistance to colistin in A. baumannii can be selected in vivo following the use of colistin in therapy

Epidemiological study on distribution and antibiotic susceptibility patterns of Enterobacteriaceae and non-fermenting bacteria, isolated in Liguria and in a neighbouring area

Introduction. An epidemiological study addressed to identify gram-negative bacteria, isolated from laboratories in a Northern area of Italy, and their antibiotic resistance patterns was conducted. Methods. Twelve laboratories distributed on Ligurian territory or neighbouring areacollected all consecutive gram-negative isolates belonging to the Enterobacteriaceae family and non-fermenter group for 2 months and sent them to a reference laboratory. Results. A total of 1880 pathogens were collected, including 899 and 981 strains isolated from nosocomial- and community-acquired infections, respectively. Escherichia coli (63.3% of total) was the most frequently isolated pathogen followed by Pseudomonas aeruginosa (9.6%), Proteus mirabilis (8.9%) and Klebsiella pneumoniae (5.4%). Nosocomial samples were collected mainly from patients in general medicine wards (19.9%) and healthcare settings (14.1%). Urine was the most common clinical sample (79.9% of the total). Other samples were sputum and bronchoaspirates (8%), skin wounds including those from decubitus (5.3%) and blood (4.1%). E. coli and P. mirabilis were collected mainly from urinary tract infection while P. aeruginosa appears more involved in respiratory or other infections. Considering the resistance to representative classes of antibiotics, it was higher (%) for piperacillin-tazobactam in P. mirabilis (30.3), for ceftazidime in Enterobacter aerogenes (40.8) and in Providencia stuartii (40), for imipenem and amikacin in P. aeruginosa (16.2 and 13.7 respectively), for ciprofloxacin in P. stuartii (66.6) and in P. mirabilis (44.7) than in others bacteria. Conclusions. The increasing age of the population in general medical wards and healthcare settings is associated with urinary tract and bedsore infections. E. coli confirms its epidemiologic and pathogenic role, but P. mirabilis and P. aeruginosa are emerging as alternativechallenges

Epidemiological study of pathogens collected from blood for a period of a year (2008-2009)

Objectives. An epidemiological study, addressed to identify the pathogens isolated from blood, and their antibiotic susceptibility patterns, was conducted. Methods. 12 laboratories, homogeneously distributed in a Northern area of Italy, were required to collected all consecutive non-duplicated strains isolated from blood during February 2008 to February 2009 and sent them to the reference laboratory. Results. A total of 1092 microorganisms were collected, including 653 gram-positive, 385 gram-negative and 54 fungi. Escherichia coli 234, Staphylococcus epidermidis 205, S. aureus 142, S. hominis 87, Enterococcus faecalis 47, S. haemolyticus 33, Klebsiella pneumoniae 33, Pseudomonas aeruginosa 32, Candida albicans 28, Enterobacter cloacae 21 were the prevalent microrganisms found. Samples were collected mainly from medicine (255 strains), intensive care units (154), surgery (99), infectious diseases (93), paediatrics (62) and nephrology (62). Antibiotic resistance (in %) in staphylococci was 65.7 (methicillin), 33.5 (gentamicin), 61.8 (azithromycin), 59.6 (erythromycin), 45.2 (ciprofloxacin) 14.8 (chloramphenicol), 2.0 (teicoplanin), and 24.1 (trimethoprim-sulfamethoxazole) no vancomycin-resistant strain was found. Enterococci showed resistance to vancomycin (10.8), ampicillin (34.4), gentamycin (42.9), ciprofloxacin (42.2) teicoplanin (7.6), erythromycin (54.7) and chloramphenicol (17.5). Enterobacteriaceae exhibited resistance to ciprofloxacin(27.0), ampicillin (74.1), ceftazidime (15.8), cefoxitin (14.7), cefepime (13.3), ceftriaxone (15.0), both imipenem and amikacin (0.95), piperacillin-tazobactam (5.1) and trimethoprim-sulfamethoxazole (32.7). Non fermenting gram negative strains were found resistant to ciprofloxacin (27.3), ceftazidime (9.5), cefepime (14.6), ceftriaxone (81.6), both imipenem and amikacin (18.6), trimethoprim-sulfamethoxazole (65.2), and piperacillin-tazobactam (7.5). Conclusions.These data show a prevalent incidence of gram-positive (59.7 %) in comparison to gram-negative (35.3%) bacteria isolated from blood.A high percentage of methicillin-resistant staphylococci as well as ceftazidime-resistance among Enterobacteriaceae is also observed suggesting that this phenomenon requires periodically surveillance