Marcela Radice

Chromosome-Encoded CTX-M-3 from Kluyvera ascorbata: a Possible Origin of Plasmid-Borne CTX-M-1-Derived Cefotaximases

ABSTRACT A gene identical to plasmid-borne blaCTX-M-3 is present in the chromosome of one Kluyvera ascorbata strain. It is associated with a structure including an inverted repeat right and an open reading frame 477-like gene probably involved in the mobilization of blaCTX-M-3. Two other K. ascorbata strains rendered the previously described blaKLUA-9 gene.

CTX-M-12 β-Lactamase in a Klebsiella pneumoniae Clinical Isolate in Colombia

ABSTRACT We describe the detection of the CTX-M-12 β-lactamase from a clinical isolate of Klebsiella pneumoniae in Colombia. Screening of nosocomial Klebsiella spp. and Escherichia coli isolates from a network of teaching hospitals revealed the presence of CTX-M enzymes in multiple cities. This is the first description of CTX-M in Colombia.

Changing epidemiology of extended-spectrum β-lactamases in Argentina: emergence of CTX-M-15

ABSTRACT A multicenter survey, carried out in 2010 in Argentina, showed an increased prevalence of extended-spectrum β-lactamase (ESBL)-producing enterobacteria, with some changes in the molecular epidemiology of circulating ESBLs. While enzymes of the CTX-M-2 group remain endemic, the emergence of CTX-M-15 and of enzymes of the CTX-M-8 and CTX-M-9 groups was observed. The CTX-M-15-positive isolates represented 40% of CTX-M producers and included representatives of Escherichia coli ST131 and Klebsiella pneumoniae ST11.

VIM-2-producing Pseudomonas putida, Buenos Aires.

To the Editor: Pseudomonas putida (0.03% of isolates from the culture collection of the Argentina Association of Microbiology, www.aam.org.ar) infections are mainly reported in immunocompromised patients, such as newborns, neutropenic patients, and cancer patients. They are usually susceptible to extended-spectrum cephalosporins, aminoglycosides, fluoroquinolones, and carbapenems. However, isolates have been identified that produce acquired metallo-β-lactamases (MBLs) and are resistant to most β-lactams, including carbapenems. Two multidrug-resistant P. putida isolates were obtained from clinical samples at the Sanatorio Mater Dei in Buenos Aires. One isolate was obtained in March 2005 from a urine specimen of a 76-year-old woman with a urinary tract infection who was using a urethral catheter. The second isolate was obtained in May 2005 from a tracheal aspirate of a 67-year-old man with nosocomial pneumonia. Bacteria were identified by using conventional biochemical tests and the API 20NE System (API, bioMerieux, Lyon, France). Susceptibility tests were performed according to standard procedures. Both isolates were resistant to imipenem and meropenem (MICs >32 μg/mL) but were susceptible to amikacin and colistin. Susceptibility data are shown in the Table. Table Antimicrobial drug susceptibility profiles of 2 blaVIM-2-carrying Pseudomonas putida isolates, Argentina Screening for MBLs was performed by using a double-disk diffusion method. Disks containing 1 μmol/L EDTA (metal chelator) were placed on Mueller-Hinton agar plates containing the 2 isolates. Disks containing carbapenem were placed 15 mm from disks containing EDTA. An increase in the inhibition zone of the disk containing drug near the disk containing EDTA was observed for both isolates, which suggested the presence of MBLs. PCR amplification of imp and vim genes was conducted by using primers based on conserved regions of the imp and vim genes (blaIMP-F: 5′-GAAGGCGTTTATGTTCATACTT-3′, blaIMP-R: 5′-GTTTGCCTTACCATATTTGGA-3′, blaVIMG-F: 5′-GGTGTTTGGTCGCATATC-3′, and blaVIMG-R 5′-TGGGCCATTCAGCCAGATC-3′) and heat-extracted DNA as template. Reactions were performed in a T-gradient instrument (Biometra, Gottingen, Germany) with the following reaction conditions: 1 cycle at 95°C for 5 min, 52°C for 15 min, and 72°C for 6 min, followed by 30 cycles at 95°C for 1 min, 52°C for 1 min, and 72°C for 1 min, and a final reaction at 72°C for 20 min. Amplified fragments were sequenced on both strands by using an ABI Prism DNA 3700 (Applied Biosystems, Foster City, CA, USA), and nucleotide sequences were compared by using BLAST (National Center for Biotechnology Information, Bethesda, MD, USA, http://www.ncbi.nlm.nih.gov/Tools/). Nucleotide sequences were completely homologous to the vim-2 coding gene. Two repetitive-element–based PCR (rep-PCR) assays (ERIC-PCR and REP-PCR) with primers REP-1 (5′-IGCGCCGICATCAGGC-3′), REP-2 (5′-CGTCTTATCAGGCCTAC-3′), ERIC-1 (5′-CACTTAGGGGTCCTCAATGTA-3′), and ERIC-2 (5′-AAGTAAGTGACTGGGGTGAGCG-3′) were used to characterize isolates. PCR conditions were 94°C for 2 min, 30 cycles at 94°C for 30 s, 50°C for 1 min, and 72°C for 4 min, and a final reaction at 72°C for 7 min. Banding patterns were visually analyzed after electrophoresis of samples. Variations in band intensity were not considered to indicate genetic differences. Banding patterns obtained by REP-PCR and ERIC-PCR assays were identical in both isolates (data not shown). Among the MBLs acquired by P. putida, IMP-1 was reported by Senda et al. in Japan in 1996 (1) and later reported in Taiwan and Japan (2). IMP-12 was the first IMP MBL described in P. putida in Europe (3). VIM-1 in P. putida was first reported in Europe (4), and VIM-2 in P. putida was first reported in Taiwan, Republic of Korea, Japan, and France (5,6). Our isolates were resistant to aztreonam (MIC 64 μg/mL). However, carbapenem-susceptible P. putida had low levels of susceptibility because the MIC50 was only 1 dilution below the current breakpoint (7,8). Aztreonam resistance could not be transferred by conjugation between IMP-1–producing (aztreonam-resistant) P. putida and P. aeruginosa (2) and is not associated with a transposon carrying blaVIM-2 (6). No evidence of extended-spectrum β-lactamases was detected in our isolates by classic synergy assays with clavulanate plus aztreonam, ceftazidime, or cefotaxime. VIM-6–producing P. putida isolates from Singapore (9) were more resistant to aztreonam (MIC >128 μg/mL), ceftazidime, and cefepime (MIC >256 μg/mL). Detection of blaVIM-2 in Pseudomonas in South America was initially reported by the SENTRY Antimicrobial Surveillance Program (10) and included 1 P. fluorescens isolate in Chile and 3 P. aeruginosa isolates in Venezuela. To the best of our knowledge, our report is the first of VIM-2 in P. putida in Latin America. VIM-2–producing P. putida, which were originally restricted to East Asia and only very recently found in France, may represent an emerging pathogen or function as reservoirs for resistance because of their widespread presence in the hospital environment.

First isolate of KPC-2-producing Klebsiella pneumonaie sequence type 23 from the Americas.

ABSTRACT KPC-2-producing Klebsiella pneumoniae isolates mainly correspond to clonal complex 258 (CC258); however, we describe KPC-2-producing K. pneumoniae isolates belonging to invasive sequence type 23 (ST23). KPC-2 has scarcely been reported to occur in ST23, and this report describes the first isolation of this pathogen in the Americas. Acquisition of resistant markers in virulent clones could mark an evolutionary step toward the establishment of these clones as major nosocomial pathogens.

Biochemical Characterization of PER-2 and Genetic Environment of blaPER-2

ABSTRACT PER-2 was the first detected and the second most prevalent extended-spectrum β-lactamase in clinical pathogens isolated in Argentina and was also reported only in other South American countries. Citrobacter freundii 33587 was isolated in 1999 in Buenos Aires and was resistant to all tested β-lactams except cephamycins and carbapenems. The strain produced both plasmid-borne TEM-1 and PER-2 (pI 5.4), which could be transferred by conjugation. By PCR screening, thermal asymmetric interlaced PCR, and DNA sequencing, we detected an ISPa12/IS1387a insertion sequence upstream of blaPER-2, previously reported as also being associated with blaPER-1. The presence of similar structures upstream of blaPER-1 and blaPER-2 suggests a common origin and mobilization. Compared to blaPER-1 genes, an additional putative promoter for blaPER-2 was found. PER-2 kinetic analysis showed its high hydrolysis efficiencies toward both CTX and CAZ (kcat/Km, 0.76 and 0.43 μM−1·s−1, respectively).

First National Survey of Antibiotic Susceptibility of the Bacteroides fragilis Group: Emerging Resistance to Carbapenems in Argentina

ABSTRACT The antibiotic susceptibility rates of 363 clinical Bacteroides fragilis group isolates collected from 17 centers in Argentina during the period from 2006 to 2009 were as follows: piperacillin-tazobactam, 99%; ampicillin-sulbactam, 92%; cefoxitin, 72%; tigecycline, 100%; moxifloxacin, 91%; and clindamycin, 52%. No metronidazole resistance was detected in these isolates during this time period. Resistance to imipenem, doripenem, and ertapenem was observed in 1.1%, 1.6%, and 2.3% of B. fragilis group strains, respectively. B. fragilis species showed a resistance profile of 1.5% to imipenem, 1.9% to doripenem, and 2.4% to ertapenem. This is the first report of carbapenem resistance in Argentina. The cfiA gene was present in 8 out of 23 isolates, all of them belonging to the B. fragilis species and displaying reduced susceptibility or resistance to carbapenems (MICs ≥ 4 μg/ml). Three out of eight cfiA-positive isolates were fully resistant to carbapenems, while 5 out of 8 isolates showed low-level resistance (MICs, 4 to 8 μg/ml). The inhibition by EDTA was a good predictor of the presence of metallo-β-lactamases in the fully resistant B. fragilis strains, but discrepant results were observed for low-level resistant isolates. B. fragilis was more susceptible to antimicrobial agents than other Bacteroides species. Bacteroides vulgatus species was the most resistant to ampicillin-sulbactam and piperacillin-tazobactam, and B. thetaiotaomicron/ovatus strains showed the highest level of resistance to carbapenems, with an unknown resistance mechanism. B. vulgatus and the uncommon non-Bacteroides fragilis species were the most resistant to moxifloxacin, showing an overall resistance rate of 15.1%.

Full Resistance and Decreased Susceptibility to Carbapenems in IMP-13-Producing Pseudomonas aeruginosa Isolates from an Outbreak

Of 23 ceftazidime-resistant Pseudomonas aeruginosa isolates with simultaneous decreased susceptibility to carbapenems recovered from inpatients at Hospital Eva Peron, Provincia de Buenos Aires, Argentina, from December 2004 to December of 2005, 18 were positive by a double-disk phenotypic screening

Intercontinental Dissemination of IMP-13-Producing Pseudomonas aeruginosa Belonging in Sequence Type 621

IMP-type metallo-β-lactamases (MBLs) were the first acquired MBLs detected in Gram-negative pathogens, in the early 1990s, and are among the most relevant due to their worldwide distribution ([12][1], [18][2]). Several IMP-type variants have been described ([3][3]). IMP-13 was first detected in

Resistencia enzimática a betalactámicos en el género Proteus y evaluación de los fenotipos y genotipos de resistencia a cefalosporinas de tercera y cuarta generación en Proteus mirabilis

Introduccion. El objetivo de este trabajo fue evaluar la resistencia a betalactamicos en el genero Proteus y caracterizar las betalactamasas responsables de dicha resistencia. Metodos. Se analizaron 99 cepas (87 P. mirabilis; 10 P. vulgaris, y 2, P. penneri) aisladas de pacientes atendidos en un Hospital Universitario. Los ensayos de susceptibilidad a antibioticos se realizaron de acuerdo con las recomendaciones del National Committee for Clinical Laboratory Standards. La presencia de betalactamasas de espectro extendido (BLEE) fue inferida por el metodo de difusion de doble disco y por la concentracion inhibitoria minima (CIM) de cefalosporinas de tercera y cuarta generacion solas y en presencia de acido clavulanico. Se estimo el punto isoelectrico (pI) por isoelectroenfoque y la presencia de los genes codificantes se confirmo por reaccion en cadena de la polimerasa (PCR). Resultados. Una betalactamasa de amplio espectro fue detectada en aquellos aislamientos resistentes a penicilinas y cefalosporinas de primera generacion (28%), mientras que la enzima CTX-M-2 fue detectada en los aislamientos de P. mirabilis resistentes a cefalosporinas de tercera y cuarta generacion (18%). Uno de los P. vulgaris presento sensibilidad disminuida a cefotaxima debido a una enzima de pI 7,4, mientras que la resistencia a cefotaxima en un P. penneri fue relacionada con una enzima de pI 6,8. Ambas enzimas fueron activas sobre cefotaxima (1.000 mg/l) en el ensayo iodometrico. Conclusion. La betalactamasa de amplio espectro en el genero Proteus fue TEM-1 mientras que CTX-M-2 fue la BLEE responsable de la resistencia a cefalosporinas de tercera y cuarta generacion en P. mirabilis. En P. vulgaris y P. penneri esta resistencia se asocio a la hiperproduccion de la betalactamasa cromosomica.