Evaluation of the carbapenem inactivation method (CIM) for detecting carbapenemase activity in enterobacteria

Objectives The objective of this study was to evaluate the accuracy of the CIM test in the detection of carbapenemase activity in 124 strains of Enterobacteriaceae. Methods A panel of 124 previously characterized Enterobacteriaceae was tested: 77 strains producing the following carbapenemase families: KPC (n = 14), GES (n = 22), NDM (n = 19), VIM (n = 4), IMP (n = 4) and OXA-48 (n = 14) and 47 non-carbapenemase producers. For the CIM method, an active susceptibility meropenem disc was exposed to a bacterial suspension of a test strain; when a carbapenemase is produced, the antibiotic is inactivated allowing uninhibited growth of an indicator strain after overnight incubation. A clear inhibition zone (?20 mm) was considered indicative of no-carbapenemase activity. Results All KPC, NDM, VIM, IMP or OXA-48 producing strains were unequivocally detected with the CIM test. CIM false negative results were obtained with eleven Enterobacter cloacae producing GES-6. Two other E. cloacae not producing carbapenemase (one with SHV-12, one hyperproducing AmpC) were positive by the test. The sensitivity and specificity of the assay compared to those of molecular methods were 85.7% and 95.7%, respectively. Conclusions The CIM method proved to be inexpensive and easy to interpret. It provided less than optimal results in the detection of GES-6 activity

Production of HlyA and ClyA haemolysins among quinolone-resistant Escherichia coli isolated from clinical samples

Most Escherichia coli resistant to quinolones are not haemolytic. The objective of this study was to determine the phylogroup, clonal relationship, mechanism of quinolone resistance and virulence factors in 70 haemolytic E. coli resistant to nalidixic acid. Sixty-six isolates contained the hlyA gene, belonged to phylogroup B2, and 61 of them presented low-level resistance to fluoroquinolones. Four isolates presented high-level resistance to fluoroquinolones, contained the clyA gene and were included in phylogroup D. One single isolate (phylogroup D, with low level resistance to fluoroquinolones) contained both cytotoxins.Supported by Ministerio de Economía y Competitividad, Instituto de Salud Carlos III, Madrid, Spain, co-financed by European Development Regional Fund “A way to achieve Europe” ERDF, Spanish Network for the Research in Infectious Diseases (REIPI RD12/0015). Alicia Márquez-López was supported by the REIPI and has been supported by a grant from the Instituto de Formación e Investigación Marqués de Valdecilla (IFIMAV), Santander, Spain. We want to thank Eduardo López for his review of English version of the manuscript.S

Tsukamurella pulmonis bloodstream infection identified by secA1 gene sequencing

Recurrent bloodstream infections caused by a Gram-positive bacterium affected an immunocompromised child. Tsukamurella pulmonis was the microorganism identified by secA1 gene sequencing. Antibiotic treatment in combination with removal of the subcutaneous port healed the patient

OXA-207, a novel OXA-24 variant with reduced catalytic efficiency against carbapenems in Acinetobacter pittii from Spain

A carbapenem-resistant Acinetobacter pittii strain carrying an OXA-24-like enzyme was isolated in northern Spain in 2008. Sequence analysis confirmed the presence of the novel bla(OXA-207) gene flanked by the site-specific XerC/XerD-like recombination binding sites and showing a unique Gly222Val substitution compared to OXA-24. Cloning and kinetic analysis showed that OXA-207 presents a reduction in the catalytic efficiency against carbapenems and a noticeable increase for oxacillin

Susceptibility to Aminoglycosides and Distribution of aph and aac(3)-XI Genes among Corynebacterium striatum Clinical Isolates

Corynebacterium striatum is an opportunistic pathogen, often multidrug-resistant, which has been associated with serious infections in humans. Aminoglycosides are second-line or complementary antibiotics used for the treatment of Corynebacterium infections. We investigated the susceptibility to six aminoglycosides and the molecular mechanisms involved in aminoglycoside resistance in a collection of 64 Corynebacterium striatum isolated in our laboratory during the period 2005?2009. Antimicrobial susceptibility was determined using E-test. The mechanisms of aminoglycoside resistance were investigated by PCR and sequencing. The 64 C. striatum were assessed for the possibility of clonal spreading by Pulsed-field Gel Electrophoresis (PFGE). Netilmicin and amikacin were active against the 64 C. striatum isolates (MICs90 = 0.38 and 0.5 mg/L, respectively). Twenty-seven of the 64 C. striatum strains showed a MIC90 for kanamycin > 256 mg/L, and 26 out the 27 were positive for the aph(3?)-Ic gene. Thirty-six out of our 64 C. striatum were streptomycin resistant, and 23 out of the 36 carried both the aph(3?)-Ib and aph(6)-Id genes. The gene aac(3)-XI encoding a new aminoglycoside 3-N acetyl transferase from C. striatum was present in 44 out of the 64 isolates, all of them showing MICs of gentamicin and tobramycin > 1 mg/L. CS4933, a C. striatum showing very low susceptibility to kanamycin and streptomycin, contains an aminoglycoside resistance region that includes the aph(3?)-Ic gene, and the tandem of genes aph(3?)-Ib and aph(6)-Id. Forty-six major PFGE types were identified among the 64 C. striatum isolates, indicating that they were mainly not clonal. Our results showed that the 64 clinical C. striatum were highly resistant to aminoglycosides and mostly unrelated

Resistance phenotypes of the 52 <i>C</i>. <i>striatum</i> strains resistant to aminoglycosides.

<p>Resistance phenotypes of the 52 <i>C</i>. <i>striatum</i> strains resistant to aminoglycosides.</p

Dendrogram showing PFGE types of the 64 <i>C</i>. <i>striatum</i>.

<p>Sample origin: SWE: surgical wound exudate; AF: ascitic fluid; NSWE: non-surgical wound exudate; DFE: diabetic food exudate; AD: abdominal drainage; S: sputum; BA: bronchial aspirate; STA: soft tissue abscess; B: blood. RES: Resistance profiles; K: kanamycin; S: streptomycin; G: gentamicin; T: tobramycin. G, T in brackets indicates resistance to gentamicin or tobramycin according to European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints.</p