ABSTRACT
One of the main mechanisms of resistance to carbapenems is potential of Klebsiella pneumoniae to produce K. pneumoniae Carbapenemase [KPC]. KPC is an important type of Carbapenemase, which can hydrolyze carbapenems and other beta-lactam antibiotics. Modified Hodge Test [MHT] and use of boronic acid as a KPC inhibitor are two types of phenotypic methods, which are used for detection of carbanemase-producing bacteria. Specificity of these two phenotypic tests for identification of KPC was assessed in this study. Forty-four K. pneumoniae strains were isolated from wound infections of burn patients. All isolates were identified with specific biochemical tests. Carbapenem-resistant K. pneumoniae isolates were identified by disc diffusion method and analyzed with cut off-points of CLSI 2011 guideline. For detection of KPC-producing strains, carbapenem-resistant isolates were examined with two different phenotypic [i.e. MHT and Boronic acid] methods. Subsequently, strains with positive phenotypic methods were examined by PCR as a molecular method. Twenty-eight [64%] out of 44 isolates were resistant to carbapenem according to CLSI breakpoints and 16 [36%] were susceptible. MHT was positive in all of carbapenem-resistant isolates but none of them have had the synergism effect between meropenem and boronic acid. Also, all isolates were negative for presence of KPC genes on gel electrophoresis. According to results MHT has not enough specificity for detection of KPC
ABSTRACT
The increasing use of beta-lactam antibiotics in clinics for the treatment of different bacterial infections since early 1980s has led to increased rates of resistant bacteria isolated from patients. One of the problems in the treatment of nosocomial infections is related to resistant bacteria such as Enterobacter cloacae due to cross resistance through extended-spectrum beta-lactamase production. The aim of this study was to determine the prevalence of extended-spectrum beta-lactamase producing E. cloacae from different clinical specimens collected from hospitalized patients. In the present study, 101 E. cloacae confirmed by standard specific microbiologic tests were collected from different specimens in Milad and Motahri hospitals in Tehran, Iran during February 2010 and September 2011. Antibiotic susceptibility tests were conducted according to the process recommended by the Clinical and Laboratory Standards Institute for 13 antibiotics of choice. Extended-spectrum beta-lactamase producing strains were screened for by combined disk method as a phenotypic diagnostic test. From a total of 101 E. cloacae, 33 [33%] were shown to produce extended-spectrum beta-lactamase by phenotypic tests; 5% of the bacteria were resistant to imipenem too. This study clearly showed the high prevalence of resistance to broad-spectrum beta-lactam antibiotics in the isolated E. cloacae among which 5% were multi drug resistant. All the isolated E. cloacae were susceptible to Colistin. These results can be alarming for physicians treating resistant E. cloacae infections, especially extended-spectrum beta-lactamase producing species