Extended-spectrum β-lactamase and AmpC β-lactamase Production among Gram-negative Bacilli Isolates Obtained from Urinary Tract Infections and Wound Infections.

Extended-spectrum β-lactamases (ESBLs) and AmpC β-lactamases continue to be a major problem in healthcare settings. Due to the scarcity of information regarding the antibiotic susceptibility patterns particularly from urinary tract infections (UTIs) and wound infections, the current study was carried out to assist the clinicians to prescribe appropriate antibiotics against gram-negative clinical isolates. In the current study, urine (n = 620) and pus (n = 228) samples were collected from different sites (at various clinical departments) and subjected to direct microscopic examination, culture and antibiotic susceptibility testing (AST). In the AST testings, the isolates that exhibited reduced zone of inhibition to one or more of the antibiotics such as cefotaxime (≤27 mm), ceftriaxone (≤25 mm), ceftazidime (≤22 mm), cefpodoxime (≤17 mm) and aztreonam (≤27 mm) were considered as potential ESBL producers and the ESBL production was confirmed using phenotypic screening test (doubledisk synergy test) and phenotypic confirmatory test (combined-disk test). However, isolates showing resistance or decreased sensitivity to cefoxitin, cefotaxime, ceftriaxone, ceftazidime, cefpodoxime or aztreonam and sensitive to cefepime were considered as a screen positive AmpC producer and subjected to AmpC disk tests. The current study concluded that 72.41% and 21.76% of ESBL and AmpC producers were detected, respectively in our hospital. It was also observed that the double-disk synergy and combined-disk tests were equally effective for ESBL detection. Further, AmpC disk test is simple, easy to perform and interpret, requiring less expertise for the rapid detection of AmpC isolates.

In vitro antibacterial activity of some antihistaminics belonging to different groups against multi-drug resistant clinical isolates

Antihistaminics are widely used for various indications during microbial infection. Hence, this paper investigates the antimicrobial activities of 10 antihistaminics belonging to both old and new generations using multiresistant Gram-positive and Gram-negative clinical isolates. The bacteriostatic activity of antihistaminics was investigated by determining their MIC both by broth and agar dilution techniques against 29 bacterial strains. Azelastine, cyproheptadine, mequitazine and promethazine were the most active among the tested drugs. Diphenhydramine and cetirizine possessed weaker activity whereas doxylamine, fexofenadine and loratadine were inactive even at the highest tested concentration (1 mg/ml). The MIC of meclozine could not be determined as it precipitated with the used culture media. The MBC values of antihistaminics were almost identical to the corresponding MIC values. The bactericidal activity of antihistaminics was also studied by the viable count technique in sterile saline solution. Evident killing effects were exerted by mequitazine, meclozine, azelastine and cyproheptadine. Moreover, the dynamics of bactericidal activity of azelastine were studied by the viable count technique in nutrient broth. This activity was found to be concentration-dependant. This effect was reduced on increasing the inoculum size while it was increased on raising the pH. The post-antimicrobial effect of 100 fg/ml azelastine was also determined and reached up to 3.36 h.

Drug-resistance and Transferable Mechanism of Integron Mediated in Gram-negative Isolates Causing Nosocomial Infection / 中华医院感染学杂志

OBJECTIVE To investigate the distribution of integron in Gram-negative isolates which are causing nosocomial infection the association with drug resistance,and it′s contribution in horizontal transfer of drug resistance.METHODS Drug resistance test was performed by K-B method.ESBL-positive strains were detected by double-disk synergy test.Integron was determined by PCR assay with integron-specific-primer.Conjugative transfer test,plasmid profile analysis,nested-PCR,and DNA sequence analysis were used to investigate the transferable mechanism of integron mediated.RESULTS 66.4% of Strains were shown to be positive for classes Ⅰ integron,no class Ⅱ and Ⅲ integrons were detected.Profiles of class Ⅰ integron were 11 types,which sized from 700bp to 2300bp,gene cassettes included genes encoding resistance to aminoglycosides(aadA1,aadA2,aadA5 and aacA4),sulfamethoxazole/trimethoprim(dfrA12,dfrA5 and dfrA17) and chloramphenicol(catB8).Strains positive for class Ⅰ integron were highly related to multidrug resistance and ESBLs.Class Ⅰ integron could horizontal transfer along with plasmid among bacteria.CONCLUSIONS Class 1 integron is widespread in Gram-negative isolates which are causing nosocomial infection.Drug resistance is more liable to horizontal transfer via class Ⅰ integron along with plasmid.It implies the necessary for surveillance of horizontal transfer of antibiotic resistance gene among bacteria genus.