Dissemination of bla NDM- 1 Gene Among Several Klebsiella pneumoniae Sequence Types in Mexico Associated With Horizontal Transfer Mediated by IncF-Like Plasmids.

Nosocomial infections caused by multidrug-resistant (MDR) Klebsiella pneumoniae are a major health problem worldwide. The aim of this study was to describe NDM-1-producing K. pneumoniae strains causing bacteremia in a tertiary referral hospital in Mexico. MDR K. pneumoniae isolates were screened by polymerase chain reaction for the presence of resistance genes. In resistant isolates, plasmids were identified and conjugation assays were performed. Clonal diversity and the sequence types were determined by pulsed-field gel electrophoresis and multilocus sequence typing. A total of 80 K. pneumoniae isolates were collected from patients with bacteremia over a 1-year period. These isolates showed a level of resistance of 59% (47/80) to aztreonam, 56-60% (45-48/80) to cephalosporins, 54% (43/80) to colistin and 12.5% (10/80) to carbapenems. The carbapenem resistant isolates were bla NDM- 1 carriers and negative for bla KPC, bla NDM, bla IMP, bla VIM and bla OXA- 48 -like carbapenemases genes. Conjugative plasmids IncFIIA and IncF group with sizes of 82-195 kbp were carriers of bla NDM- 1, bla CTX-M- 15, bla TEM- 1, aac(6')-Ib and/or aac(3')-IIa. Clonal variability and nine different multilocus sequence types were detected (ST661, ST683, ST1395, ST2706, ST252, ST1198, ST690, ST1535, and ST3368) for the first time in the isolates carrying bla NDM- 1 in Mexico. This study demonstrates that bla NDM- 1 has remained within this hospital in recent years and suggests that it is currently the most prevalent carbapenemase among K. pneumoniae MDR strains causing bacteremia in Mexico. The horizontal transfer of bla NDM- 1 gene through IncF-like plasmids among different clones demonstrates the dissemination pathway of antimicrobial resistance and underscore the need for strong and urgent joint measures to control the spread of NDM-1 carbapenemase in the hospital.

Pseudomonas aeruginosa Isolates From a Cohort of Mexican Children With Cystic Fibrosis Show Adaptation to a Chronic Phenotype.

BACKGROUND: Long-term persistence of Pseudomonas aeruginosa in the lung of individuals with cystic fibrosis (CF) is associated with progressive selection of diverse genotypes and phenotypes. This bacterial adaptation leads to chronic infection and increased morbidity and mortality. The aim of this study was to establish the prevalence, clonal relatedness, antimicrobial susceptibility and virulence-associated phenotypes of P. aeruginosa isolates in a cohort of 50 Mexican children with CF-associated chronic lung infection. METHODS: Clonal relatedness of P. aeruginosa isolates was verified by pulsed-field gel electrophoresis. The antimicrobial susceptibility was determined by an automated system that performs bacterial identificación and antibiotic susceptibility testing (VITEK 2) and/or broth microdilution method. Biofilm formation was quantified with the crystal violet method; swarming motility was measured on soft agar, and susceptibility to normal human serum determined by reduction of colony formed units (CFUs). RESULTS: High prevalence of P. aeruginosa colonization among Mexican children with CF was confirmed; 20% (10/49) of clones identified showed a multidrug-resistant phenotype and 8.2% (4/49) an extensive drug resistance phenotype; 26.5% (13/49) of the isolates were resistant to colistin, 42.9% (21/49) presented a phenotype of adaptation associated with chronic infection and 79.6% (39/49) showed increased ability to survive in normal human serum. CONCLUSIONS: This cohort of children with CF reveals that colonizing P. aeruginosa strains predominantly display resistance to several first-line antibiotics, although most isolates were susceptible to meropenem and tobramycin; 42.9% of isolates showed a phenotype consistent with adaptation to chronic lung infection.

Carbapenem-Resistant Acinetobacter baumannii in Three Tertiary Care Hospitals in Mexico: Virulence Profiles, Innate Immune Response and Clonal Dissemination.

Acinetobacter baumannii is one of the most important nosocomial pathogens distributed worldwide. Due to its multidrug-resistance and the propensity for the epidemic spread, the World Health Organization includes this bacterium as a priority health issue for development of new antibiotics. The aims of this study were to investigate the antimicrobial resistance profile, the clonal relatedness, the virulence profiles, the innate host immune response and the clonal dissemination of A. baumannii in Hospital Civil de Guadalajara (HCG), Hospital Regional General Ignacio Zaragoza (HRGIZ) and Pediatric ward of the Hospital General de México Eduardo Liceaga (HGM-P). A total of 252 A. baumannii clinical isolates were collected from patients with nosocomial infections in these hospitals between 2015 and 2016. These isolates showed a multidrug-resistant profile and most of them only susceptible to colistin. Furthermore, 83.3 and 36.9% of the isolates carried the bla OXA- 24 and bla TEM- 1 genes for resistance to carbapenems and ß-lactam antibiotics, respectively. The clonal relatedness assessed by pulsed-field gel electrophoresis (PFGE) and by multi-locus sequence typing (MLST) demonstrated a genetic diversity. Remarkably, the ST136, ST208 and ST369 that belonged to the clonal complex CC92 and ST758 and ST1054 to the CC636 clonal complex were identified. The ST136 was a high-risk persistent clone involved in an outbreak at HCG and ST369 were related to the first carbapenem-resistant A. baumannii outbreak in HRGIZ. Up to 58% isolates were able to attach to A549 epithelial cells and 14.5% of them induced >50% of cytotoxicity. A549 cells infected with A. baumannii produced TNFα, IL-6 and IL-1ß and the oxygen and nitrogen reactive species that contributes to the development of an inflammatory immune response. Up to 91.3% of clinical isolates were resistant to normal human serum activity. Finally, 98.5% of the clinical isolates were able to form biofilm over polystyrene tubes. In summary, these results demonstrate the increasingly dissemination of multidrug-resistant A. baumannii clones in three hospitals in Mexico carrying diverse bacterial virulence factors that could contribute to establishment of the innate immune response associated to the fatality risks in seriously ill patients.

Emergence of IncFIA Plasmid-Carrying blaNDM-1 Among Klebsiella pneumoniae and Enterobacter cloacae Isolates in a Tertiary Referral Hospital in Mexico.

The emergence of New Delhi metallo-ß-lactamase 1 on carbapenemase-producing bacteria has raised a major worldwide public health concern. This study reports the dissemination of blaNDM-1 in carbapenem-resistant isolates that caused nosocomial infections in a tertiary hospital in Mexico City. Seven Enterobacter cloacae and three Klebsiella pneumoniae nosocomial isolates from the same time period harbored the blaNDM-1 gene. The resistance phenotype and the blaNDM-1 gene were transferred through conjugative plasmids belonging to the incompatibility group IncFIA of 85, 101, and 195 kb in E. cloacae and 95 and 101 kb in K. pneumoniae isolates. Restriction fragment length polymorphism analysis showed that blaNDM-1 was carried in similar plasmids with molecular sizes of 101 and 85 kb, each one in three isolates of E. cloacae and one of 101 kb on two isolates of K. pneumoniae. During a 9-month period, six of the seven isolates of E. cloacae analyzed harbored blaNDM-1 and belonged to clone E1. Similarly, over a 5-month period, two of the three K. pneumoniae isolates that harbored blaNDM-1 belonged to clone K1. These results demonstrate the horizontal transfer of blaNDM-1 between different bacterial species, dissemination of clones with high levels of resistance to carbapenems, and underscore the need for heightened measures to control their further spread.