Isolation of five Enterobacteriaceae species harbouring blaNDM-1 and mcr-1 plasmids from a single paediatric patient

In Argentina, NDM metallo-β-lactamase was first reported in 2013. By now, it has disseminated throughout the country in diverse Gram negative bacteria. Here, we report the case of a paediatric patient that underwent a 1-year hospitalisation due to erythrodermic psoriasis in 2014 and received multiple antimicrobial treatments. During his stay, five isolates were obtained from rectal swabs (rs) or blood culture (bc) suspicious of carbapenemase production: a K. quasipneumoniae subsp. quasipneumoniae (rs), Citrobacter freundii (rs), Escherichia coli (bc), Enterobacter cloacae (rs), and a Serratia marcescens (bc). The isolates were studied with broth microdilution, biparental conjugation and plasmid and whole genome sequencing (Illumina). All isolates harboured an 138,998-bp type 1 IncC plasmid that carried bla_NDM-1, ble_MBL, bla_CMY-6, rmtC, aac(6’)-Ib, and sul1 resistance genes. Additionally, the bla_NDM-plasmids contained ISKpn8 an insertion sequence previously described as associated only to bla_KPC. One isolate, a colistin-resistant E. coli, also carried a mcr-1-containing an IncI2 plasmid, which did not harbour additional resistance. The whole genome of K. quasipneumoniae subsp. quasipneumoniae isolate was fully sequenced. This isolate harboured, additionally to bla_NDM, three plasmid-mediated quinolone resistance genes: qnrB4, qnrB52 and aac(6’)-Ib-cr1. The E. cloacae isolate also harboured qnrA1. These findings alert to the underestimated horizontal dissemination of multidrug-resistant plasmids limiting treatment options with last resort antimicrobials.

Intrapatient emergence of OXA-247: a novel carbapenemase found in a patient previously infected with OXA-163-producing Klebsiella pneumoniae

Two genetically related Klebsiella pneumoniae strains carrying OXA-type carbapenemases were isolated from a single patient 1 month apart. Kpn163 harboured OXA-163 and Kpn247 a new variant named OXA-247 that showed susceptibility to carbapenems and expanded-spectrum cephalosporins similar to OXA-48. Our epidemiological, biochemical and molecular results suggest the intrapatient emergence of blaOXA -247 from blaOXA -163.

Clonal dissemination of Klebsiella pneumoniae ST258 harbouring KPC-2 in Argentina

The present work describes the abrupt emergence of Klebsiella pneumoniae carbapenemase (KPC) and characterizes the first 79 KPC-producing enterobacteria from Argentina (isolated from 2006 to 2010). The emergence of bla(KPC-2) was characterized by two patterns of dispersion: the first was the sporadic occurrence in diverse enterobacteria from distant geographical regions, harbouring plasmids of different incompatibility groups and bla(KPC-2) in an unusual genetic environment flanked by ISKpn8-Δbla(TEM-1) and ISKpn6-like. bla(KPC-2) was associated with IncL/M transferable plasmids; the second was the abrupt clonal spread of K. pneumoniae ST258 harbouring bla(KPC-2) in Tn4401a.

A simple test for the detection of KPC and metallo-β-lactamase carbapenemase-producing Pseudomonas aeruginosa isolates with the use of meropenem disks supplemented with aminophenylboronic acid, dipicolinic acid and cloxacillin

We evaluated the ability of the combination disk test (CDT) and the Modified Hodge Test (MHT) to discriminate between various carbapenemase-producing Pseudomonas aeruginosa isolates (KPC, n = 36; metallo-β-lactamase (MBL), n = 38) and carbapenemase non-producers (n = 75). For the CDT, the optimal inhibitor concentrations and cut-off values were: 600 μg of 3-aminophenylboronic acid (APB) per disk (an increment of ≥4 mm), 1000 μg of dipicolinic acid (DPA) per disk (an increment of ≥5 mm) and 3000 μg of cloxacillin per disk (an increment of ≥3 mm). APB had excellent sensitivity (97%) and specificity (97%) for the detection of KPC enzymes. DPA detected MBL enzymes with a sensitivity and specificity of 97% and 81%, respectively. The MHT resulted in a low sensitivity (78%) and specificity (57%). The CDT could be very useful in daily practice to provide fast and reliable detection of KPC and MBL carbapenemases among P. aeruginosa isolates.

Fluoroquinolone-resistant Streptococcus agalactiae isolates from Argentina

Fluoroquinolone resistance is a growing problem that has only recently emerged in S. agalactiae. Between 2005-2007, WHONET--Argentina network evaluated levofloxacin susceptibility in 1128 clinical S. agalactiae isolates, 10 (0.9%) of which proved to be resistant. Nine of them had come from 5 hospitals (in Buenos Aires City and 4 Argentinean provinces) and recovered from urine (n=7) and vaginal screening cultures (n=2). Three strains were also resistant to macrolides, lincosamides and B streptogramins due to the ermA gene. All nine fluoroquinolone-resistant isolates bore the same two mutations, Ser79Phe in ParC and Ser81Leu in GyrA proteins. Genetic relationships were analyzed by Apal-PFGE and two clones were determined, A (n=6) and B (n=3). To our knowledge, these are the first fluoroquinolone-resistant S. agalactiae isolates detected in Latin America.

Prevalence of mef and ermB genes in invasive pediatric erythromycin-resistant Streptococcus pneumoniae isolates from Argentina

During the period 1993-2001, a total of 1,499 pneumococci isolates were recovered through the Argentinean surveillance of Streptococcus pneumoniae causing invasive disease in children under 6 years of age, 3.5% of which were erythromycin resistant. Among the 50 erythromycin-resistant strains available, 58% (n=29) harbored mefA/E genes (15 mefA, 30%; and 14 mefE, 28%), 34% (n=17) ermB, and 6% (n=3) both mefA/E plus ermB genes, while one isolate was negative for all the acquired genes studied. The England14-9 (42%), Poland6B-20 (20%) and Spain9V-3 (16%) clones were responsible for the emergence of pneumococcal macrolide resistance in pediatric population from Argentina.

First report of VanA Enterococcus gallinarum dissemination within an intensive care unit in Argentina

Enterococcusgallinarum is intrinsically resistant to low levels of vancomycin and has been described as a colonizing microorganism causing bacteraemia and infection among immunosupresed patients. Between August 2000 and February 2001, 15 highly glycopeptide-resistant E. gallinarum isolates, one from blood and the remaining from rectal swabs, were recovered in a general hospital of Buenos Aires Province, Argentina. All isolates were characterized by biochemical assays, and displayed MICs of vancomycin in the range 16-128 mg/l and MICs of teicoplanin in the range 16-32 mg/l. In all cases, PCR analysis yield positive results for both vanC1 and vanA genes. E. gallinarum isolates were classified as two clonal types by SmaI-PFGE: clone A (n = 8) and clone B (n = 7) and both harboured a transferable vanA element.

Improvement of a latex agglutination test for the evaluation of oxacillin resistance in coagulase-negative staphylococci

The "Slidex MRSA Detection" test (Denka Seiken, Japan) is a latex agglutination assay able to detect PBP2a. We evaluated its ability to differentiate mecA-positive from mecA-negative coagulase-negative staphylococci. We included 100 coagulase-negative staphylococci clinical isolates belonging to 9 species, 54 mecA positive and 46 mecA negative, as characterized by PCR. The specificity achieved using the manufacturer's instructions was 100%, but the sensitivity was only 57%. To increase sensitivity, we introduced modifications into the standard protocol. Using either large inocula or oxacillin induction before test performance, we achieved 100% sensitivity.

[Methicillin resistance detection in Staphylococcus aureus: comparison between conventional methods and MRSA-Screen latex agglutination technique]

Methicillin-resistant Staphylococcus aureus (MRSA) is a significant pathogen that has emerged over the last four decades, causing both nosocomial and community-acquired infections. Rapid and accurate detection of methicillin resistance in S. aureus is important for the use of appropriate antimicrobial therapy and for the control of nosocomial spread of MRSA strains. We evaluated the efficiency of conventional methods for detection of methicillin resistance such as the disk diffusion, agar dilution, oxacillin agar screen test, and the latex agglutination test MRSA-Screen latex, in 100 isolates of S. aureus, 79 mecA positive and 21 mecA negative. The MRSA-Screen latex (Denka Seiken, Niigata, Japón), is a latex agglutination method that detects the presence of PLP-2a, product of mecA gene in S. aureus. The PCR of the mecA gene was used as the "gold standard" for the evaluation of the different methods tested. The percentages of sensitivity and specificity were as follows: disk difusión 97 and 100%, agar dilution 97 and 95%, oxacillin agar screen test 100 and 100%, and MRSA-Screen latex, 100 and 100 %. All methods presented high sensitivity and specificity, but MRSA-Screen latex had the advantage of giving a reliable result, equivalent to PCR, in only 15 minutes.