Polymyxin resistance in Enterobacterales: overview and epidemiology in the Americas.

The worldwide spread of carbapenem- and polymyxin-resistant Enterobacterales represents an urgent public-health threat. However, for most countries in the Americas, the available data are limited, although Latin America has been suggested as a silent spreading reservoir for isolates carrying plasmid-mediated polymyxin resistance mechanisms. This work provides an overall update on polymyxin and polymyxin resistance and focuses on uses, availability and susceptibility testing. Moreover, a comprehensive review of the current polymyxin resistance epidemiology in the Americas is provided. We found that reports in the English and Spanish literature show widespread carbapenemase-producing and colistin-resistant Klebsiella pneumoniae in the Americas determined by the clonal expansion of the pandemic clone ST258 and mgrB-mediated colistin resistance. In addition, widespread IncI2 and IncX4 plasmids carrying mcr-1 in Escherichia coli come mainly from human sources; however, plasmid-mediated colistin resistance in the Americas is underreported in the veterinary sector. These findings demonstrate the urgent need for the implementation of polymyxin resistance surveillance in Enterobacterales as well as appropriate regulatory measures for antimicrobial use in veterinary medicine.

Draft Genome Sequence of a Hypermucoviscous Extended-Spectrum-ß-Lactamase-Producing Klebsiella quasipneumoniae subsp. similipneumoniae Clinical Isolate.

A clinical isolate of extended-spectrum-ß-lactamase-producing Klebsiella quasipneumoniae subsp. similipneumoniae 06-219 with hypermucoviscosity phenotypes obtained from a urine culture of an adult patient was used for whole-genome sequencing. Here, we report the draft genome sequences of this strain, consisting of 53 contigs with an ~5.6-Mb genome size and an average G+C content of 57.36%. The annotation revealed 6,622 coding DNA sequences and 77 tRNA genes.

Characterisation of quinolone-resistant Escherichia coli of 1997 and 2005 isolates from poultry in Mexico.

Forty-two enrofloxacin-resistant Escherichia coli strains isolated from eggs and first-week mortality associated with yolk sac infection of two vertically integrated poultry companies of Central Mexico in 1997 and 2005 were characterised. E. coli resistance to 19 antibiotics was determined, as well as the minimum inhibitory concentrations (broth dilution) for ciprofloxacin. The presence of gyrA,B, parC,E chromosomal point mutations, qnrA,B,S plasmid genes and the aminoglycoside acetyltransferase aac(6')-Ib-cr were determined by PCR and sequencing. Resistance to ampicillin (95%), piperacillin (95%), gatifloxacin (95%), levofloxacin (95%), ampicillin/sulbactam (90%), cefazolin (85%), trimethoprim/sulfamethoxazole (80%), amoxicillin/clavulanic acid (80%), aztreonam (80%), cefepime (80%), cefotaxime (80%), ceftazidime (80%), ceftriaxone (80%) and cefoxitin (75%) was high in the 2005 strains and 19 (95%) strains were resistant to 7 or more antimicrobials. The strains from 1997 expressed high rates of resistance only to the fluoroquinolones and 4 strains (18%) expressed resistance to 7 or more antimicrobials. All strains had a gyrA mutation (Ser83Leu) and a parC mutation (Ser80Ile or Ser80Arg) and 41 (97.6%) strains had a second gyrA mutation (Asp87Asn, Asp87Tyr or Asp87Gly). Only two (4.7%) strains had a parE mutation (Ser458Ala). A total of 10 strains were positive for the aac(6')-Ib wild-type gene, 6 strains for the aac(6')-Ib-cr variant and 6 strains possessed both the wild type and the variant. No gyrB mutations or qnrA,B,S genes were detected. This is the first report in Latin America of chromosomal and plasmid quinolone resistance genes in E. coli strains recovered from poultry.

Identification of OXA-23 carbapenemases: novel variant OXA-239 in Acinetobacter baumannii ST758 clinical isolates in Mexico.

A collection of 15 carbapenem-resistance Acinetobacter baumannii clinical isolates was analysed on two tertiary hospitals in Mexico. The OXA-51 was identified in all isolates, followed by OXA-239 and OXA-58; OXA-239 is described as a new OXA-23-like allele. These carbapenemases were identified on four clonal groups, distributed between two neighbouring hospitals. Acinetobacter baumannii is poorly studied in Mexico; this situation urges the implementation of strategies to prevent its dissemination.

Identification of SHV-type and CTX-M-12 extended-spectrum beta-lactamases (ESBLs) in multiresistant Enterobacteriaceae from Colombian Caribbean hospitals.

The production of extended-spectrum beta-lactamases (ESBLs) in Enterobacteriaceae is the most prevalent resistance mechanism to third-generation cephalosporins. The aim of this study was to identify the ESBLs produced in Escherichia coli and Klebsiella pneumoniae clinical isolates from two hospitals of the Colombian Caribbean Region. A total of 30 clinical isolates of K. pneumoniae (21) and E. coli (9) ESBL-producers were collected in two hospitals from January, 2001 to June, 2003. Isoelectric point values were indicative of SHV-, and CTX-M-type beta-lactamases. PCR amplification and sequencing of SHV genes revealed that SHV-12 was the most prevalent ESBL followed by SHV-5, SHV-2a, the novel SHV-86 and CTX-M-12. There was a geographic distribution of two particular PFGE subtypes in these two distant hospitals. Clonal and horizontal dissemination of resistance was observed.

The blaSHV-5 gene is encoded in a compound transposon duplicated in tandem in Enterobacter cloacae.

The presence of bla(SHV-5) is described in a compound transposon, duplicated in tandem and flanked by IS26 copies on a 70-kb conjugative plasmid (pHNM1), in an Enterobacter cloacae strain associated with a nosocomial outbreak that occurred in Mexico.

Outbreak of infection by extended-spectrum beta-lactamase SHV-5-producing Serratia marcescens in a Mexican hospital.

Previous outbreaks caused by Serratia marcescens have been associated with contaminated medical equipment, intravenous fluids and inadequate hygiene. We carried out the molecular characterization of an outbreak produced by a cephalosporin-resistant S. marscescens that occurred in a Mexican hospital in August 1999. The lethality of this outbreak was 26%. Positive isolates were collected from 20 patients, one medical staff and three chlorhexidine disinfectant solutions. Results of PFGE, beta-lactamase patterns, sequencing of PCR amplifications, plasmid profiles, and mating experiments showed that the outbreak occurred by the dissemination of a S. marcescens SHV-5 producing strain. The adequate enforcement of procedures under the supervision of an infection control resulted in the abrupt end of the outbreak.

Metallo-beta-lactamase gene bla(IMP-15) in a class 1 integron, In95, from Pseudomonas aeruginosa clinical isolates from a hospital in Mexico.

During 2003, 40 carbapenem-resistant Pseudomonas aeruginosa clinical isolates collected in a Mexican tertiary-care hospital were screened for metallo-beta-lactamase production. Thirteen isolates produced IMP-15, and 12 had a single pulsed-field gel electrophoresis pattern. The bla(IMP-15) gene cassette was inserted in a plasmid-borne integron with a unique array of gene cassettes and was named In95.

Surveillance of methicillin-resistant Staphylococcus aureus in a pediatric hospital in Mexico City during a 7-year period (1997 to 2003): clonal evolution and impact of infection control.

Between 1997 and 2000 a single multidrug-susceptible methicillin-resistant Staphylococcus aureus clone, M (sequence type 30 [ST30]-staphylococcal cassette chromosome mec [SCCmec] type IV), was present in a pediatric hospital in Mexico City, Mexico. In 2001 the international multidrug-resistant New York-Japan clone (ST5-SCCmec type II) was introduced into the hospital, completely replacing clone M by 2002.

Study of outer membrane proteins (OMPS) and their role in co-modulation of resistance in non typhoidic Salmonella strains isolated in Iasi.

OBJECTIVES: To characterize the OMP profile and to study the possible interference with other resistance determinants. MATERIAL AND METHODS: 16 non-typhoidic Salmonella strains, isolated in 1999 from stools of pediatric patients, were selected according to their resistance phenotype: resistance to Ampicillin (AMP), Amoxycillin/Clavulanic Acid (AMC), and third generation cephalosporins: Ceftriaxone (CRO) and Ceftazidime (CAZ). Identification and sensitivity testing were done by DADE MicroScan System. beta-Lactamases were characterized by isoelectric focusing (IEF) with preformed minigelss. OMPs were studied on membrane preparations on SDS-urea gels. RESULTS: Isoelectric points: Majority of the isolates had the association 5.4 +/- 7.6 (3/16) or 5.4 + 8.2 (6/16). The second beta-lactamase has the capacity to hydrolyse CAZ. We found three different patterns of OMPs: I: 30, 29 and 25 kDa; II: 30, 26 and 24 kDa; III: 30 and 25 kDa. We couldn't find any correlation between the OMPs profile and resistance phenotype, showing that the beta-lactamase production is the only resistant determinant. CONCLUSIONS: The study shows the high frequency of extended-spectrum beta-lactamases (ES beta LA) amongst the non-typhoidic Salmonella; association of TEM type and ES beta LA enzymes diminishes considerably the therapeutic resources: inhibitor associated combinations are non effective. In non-typhoidic Salmonella, porins seems to have no influence in co-modulation of resistance.

beta-Lactamase bioassay: a simplified method to determine extended-spectrum beta-lactamases (ESBL) in enterobacteria.

With the simultaneous use of an isoelectric focusing gel (IEF) and a nitrocefin/cefotaxime bioassay, it is possible to identify the Extended-Spectrum beta-lactamases (ESBL) with precision. A mixture of soft agar and susceptible bacterial cells are layered over the gel following overnight incubation and areas of cell growth are detected where the antibiotic has been hydrolyzed by specific enzymes. This innovative method improves sensitivity and specificity for the identification of ESBLs in those enterobacteria strains producing more than one beta-lactamase and are resistant to third generation cephalosporines.

Bacterial resistance to antibiotics in acute respiratory infections (ARIs).

In this review article, we make suggestions on how to approach the increasing problem worldwide of bacterial acute respiratory infections resistant to antibiotics. After a brief description of the main mechanisms of bacterial resistance, i.e., enzymatic inactivation by beta-lactamases, reduction in the permeability of the outer membrane and the development of PBPs that have decreased affinity for the antibiotic, we analyze documented experiences on the response to different groups of antibiotics (beta- lactam antibiotics, cephalosporins, carbapenems and quinolones), of the most commonly isolated bacteria from invasive respiratory infections (Haemophilus influenzae, Streptococcus pneumoniae and Moraxela (Branhamella) catarrhalis. Antimicrobial agent susceptibility in vivo and in vitro testing and the correlation of their results provide the basic information for the adoption of adequate policies and strategies for better use of antibiotics in bacterial respiratory infections; proper surveillance would allow to make intelligent changes in such a policy. Standardized recommendations for clinical practice on the use of antibiotics could be misleading, iatrogenic, and could complicate the resistance problem. To prevent and control the rise and spread of bacterial resistance, an interdisciplinary approach is needed.