In vitro activity of tigecycline and other antimicrobial drugs against selected pathogens isolated in Mexico

Abstract number: P2075

Ponce de Leon A., Amabile-Cuevas C.F., Benitez A.

Objective: A multi-national, multi-centre susceptibility survey (TEST) was established to assess the in vitro efficacy of tigecycline and other antimicrobials against relevant aerobic pathogens. Here we report the results of 1,280 isolates from 6 hospitals at the three main Mexican cities

Methods: The survey included fresh isolates of selected pathogens, identified as causative of infection; only one isolate per patient was included, and no more than 25% of the sample came from urinary tract infections. Minimal inhibitory concentrations (MIC) were assessed by microdilution to ampicillin (AM), amoxycillin-clavulanate (AC) piperacillin-tazobactam (PT), levofloxacin (LV), ceftriaxone (CX), minocycline (MC), imipenem (IM) and tigecycline (TG) for all isolates (except TG for Acinetobacter and Pseudomonas), and linezolid (LZ), vancomycin (VA) and penicillin (PN) for Gram-positives, or cefepime (CF), ceftazidime (CZ) and amikacin (AK) for Gram-negatives. Data were recorded in forms and compiled in a global database; strains were stored and shipped to a central lab for further testing (ESBL production by enteric bacteria, using ceftazidime/cefotaxime+clavulanate disks; and meticillin resistance in S. aureus, using cefoxitin disks).

Results: Most relevant resistance prevalences include: 48% of S. aureus are MRSA; only one enterococcus strain was LZ-R; 12.5% of S. pneumoniae were PN-R; 36% of E. coli and 28% of K. pneumoniae were ESBL-producers; resistance to carbapenems was common in non-fermentative Gram-negatives, but absent in enteric bacteria. Only one strain (K. pneumoniae) out of 1,001 tested were resistant to TG; even MC-R strains, were susceptible to TG. Resistance to LV was linked to MRSA (94%, vs. 4% among MSSA), and to ESBL-producers: 65% of K. pneumoniae (vs. 31% total) and 99% of E. coli (vs. 70% total).

Conclusions: Dangerous multi-resistant organisms (MRSA, VRE, ESBL-producers) were found at high rates among Mexican pathogens, some linked to unrelated resistance phenotypes, which could foster resistance by co-selection. Non-fermentative bacilli were often resistant to drugs of choice (AK, cephalosporins, carbapenems). Linezolid was, in vitro, the most effective drug against Gram-positives, and tigecycline the most effective drug overall, justifying its position against intra-abdominal and skin infections. These antibiotics should be used carefully to preserve their efficacy.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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