Biofilm Formation and Susceptibility to Polymyxin B by a Highly Prevalent Clone of Multidrug-Resistant <b><i>Acinetobacter baumannii</i></b> from a Mexican Tertiary Care Hospital

Abstract

Background:Acinetobacter baumannii has emerged as a major cause of hospital-associated infections with increased morbidity and mortality among those affected. Methods: A total of 85 isolates of a highly prevalent multidrug-resistant clone, identified during the period 2007-2011, were analyzed for biofilm formation on a polystyrene surface. The minimal inhibitory concentration was determined by the Sensititre System, the agar disk diffusion method and then read by means of the BIOMIC system and serial dilutions on Müller-Hinton agar. Results: In this study, covering a period of 5 years (2007-2011), we demonstrate that a particular clone emerged as the most prevalent, with an associated lethality of 28.2%. We demonstrate that 92.9% of strains corresponding to this clone are biofilm producers. Our results also demonstrate that all isolates were 100% susceptible to polymyxin B. Conclusion: Our study suggests that the high prevalence and lethality of this multidrug-resistant clone of A. baumannii and its persistence over close to 5 years in a Mexican tertiary hospital environment can be explained in part by the ability of these clinical isolates of A. baumannii to form biofilms.

Resurgence of Polymyxin B for MDR/XDR Gram-Negative Infections: An Overview of Current Evidence

“…With a breakpoint of ≤2 mg/L, 98.2% strains were identified to be susceptible establishing efficacy of polymyxin B in CRAB infections. This finding can further be substantiated with findings from Mexico wherein Rosales-Reyes and colleagues [32] demonstrated 100% susceptibility of highly lethal (28.2% mortality) and biofilm producing clone (92.9% strains)—MDR A. baumannii —to polymyxin B. This clone was resistant to major antibiotics including aminoglycosides, cephems, carbapenems, and fluoroquinolones.…”

Virulence profiles and innate immune responses against highly lethal, multidrug-resistant nosocomial isolates of Acinetobacter baumannii from a tertiary care hospital in Mexico

“…baumannii infection showed higher mortality rate (52.8%) than those with A . baumannii infection into the Hospital Civil de Guadalajara, Mexico (28.2%) reported previously [ 32 ]. In other countries, the mortality rate due to bloodstream imipenem-resistant A .…”

“…In contrast, 92.2% of the members of a highly prevalent clone of A . baumannii in the Hospital Civil de Guadalajara, Mexico were able to produce biofilm [ 32 ]. Our results show that almost all unrelated isolates were biofilm producers.…”

“…The biofilm production on an abiotic surface was quantified as previously described [ 32 ]. Briefly, 5 ml overnight cultures grown at 37 ° C were diluted to OD 600 0.003 in Luria Bertani (LB) media and triplicate 500 μl aliquots were dispensed into polystyrene tubes.…”

High Burden of Antibiotic Resistant Bacteria Isolated from Tracheal Culture in a Tertiary Care Institute

“…Among healthcare settings of high-risk infection, intensive care unit (ICU) is considered an "epicenter of infections". 8 The emergence of antimicrobial resistance in ICUs is of great concern as it increases the likelihood of drug interactions/side effects and cost of therapy due to use of newer antibiotics. Resistance may also be responsible for prolonged hospital stays and can affect prognosis.…”