ABSTRACT
Glycopeptides such as vancomycin are frequently the antibiotics of choice for the treatment of infections caused by methicillin resistant Staphylococcus aureus [MRSA]. Since vancomycin-intermediate Staphylococcus aureus [VISA] was first reported in Japan in 1997, there has been great concern that heterogeneous vancomycin-intermediate Staphylococcus aureus [hVISA] is the putative precursor of VISA. The aim of this study was to explore the prevalence of VISA and hVISA among MRSA strains isolated from hospitalized patients in Alexandria University Hospital over a 2 years period, and to investigate their clinical significance and mechanism of vancomycin resistance. Sixty two MRSA isolates were screened by using brain heart infusion agar supplemented with 4 micro g/ml vancomycin [BHI-V4] and macro E test. Minimum inhibitory concentrations [MICs] of vancomycin were determined by broth microdilution and standard E test. Population analysis profile [PAP] was performed for detecting the frequency of heterogeneous resistance for isolates grown on BHI-V4. Vancomycin intermediate resistant subpopulations of hVISA were viewed with scanning electron microscopy, and tested for the presence of van A gene by PCR. Twenty one [33.87 %] MRSA isolates grew on BHI-V4, 7 [11.29 %] isolates were suspected of having reduced susceptibility to vancomycin by macro E test. The PAP confirmed 6 [9.68 %] isolates as hVISA since they produced subpopulations with MIC of vancomycin of > 4 micro g/ml at frequency of 1 in 10[6] CFU/ml or higher. Vancomycin MIC values for all isolates were
ABSTRACT
The increased use carbapenems for the treatment of infections caused by multiresistant Pseudomonas aeruginosa [P. aeruginosa] has resulted in the development of carbapenem resistant [CR] P. aeruginosa. In recent years, the metallo-B-lactamases [MBLs] have emerged as one of the most feared resistance mechanisms because of their ability to hydrolyse virtually all B-lactam agents including the carbapenems, and because their genes are carried on highly mobile elements. This study was carried out to investigate the prevalence of MBLs among clinical isolates of carbapenem-resistant P. aeruginosa, and to characterize their molecular types. A total of 134 non-repetitive clinical isolates of P. aeruginosa were collected and tested for carbapenem resistance by disk diffusion method with imipenem and meropenem. Minimum inhibitory concentrations [MICs] were determined by the microdilution technique according to CLSI guidelines. Carbapenem-resistant isolates were screened for the presence of MBLs by imipenem EDTA double disk synergy test. Isolates with screen positive results were confirmed by EDTA inhibition of imipenem hydrolysis with their crude cell extracts, and by PCR using primers for detection of bla[IMP-1], bla[IMP-2], bla[VIM-1], bla[VIM-2], and intI1 genes. Out of the 134 P. aeruginosa clinical isolates included, 75 [56%] isolates were CR, among them MBL phenotype was detected in 30 [40%] isolates by the double disk synergy test. EDTA sensitive hydrolysis of imipenem by crude cell extracts confirmed 14 [46.7%] isolates as MBL producers. PCR detected MBL genes among 15 [50%] isolates; 11 [73.3%] isolates were positive for bla[VIM-2], and 4 [26.7%] isolates were positive for bla[IMP-1]. The integrase gene [intI1] was detected in all of the 15 genotypically MBLpositive isolates. No isolate harboring bla[IMP-2], or bla[VIM-1] was detected. Continued screening for MBLs production among CR P. aeruginosa isolates will be essential to control dissemination of this important resistant mechanism, ensure optimal patient care, and the timely introduction of appropriate infection control procedures. PCR is an important step, since EDTA based screening tests can give false positive results
ABSTRACT
Helicobacter pylori [H. pylori] is the main cause of several gastro-duodenal diseases, and is also related to a variety of extragastric diseases, including liver diseases. It was classified as class I carcinogen. Several risk factors for the development of hepatocellular carcinoma [HCC] are identified. Continuing attempts are being made to identify other risk factors. The objective of this study was to evaluate the presence of H. pylori DNA in human HCC to determine if H. pylori may contribute to the development of this disease. Liver specimens from 33 patients with HCC as well as from 6 patients who did not have malignancy; 4 had cholelithiasis and 2 had hepatic hemangioma considered as control, were studied. Liver samples were examined by polymerase chain reaction [PCR] for the presence of genomic 16S rRNA of Helicobacter genus using specific primers. Besides, other genes; 26 kDa cell surface protein, cag A, and vac A, specific for H. pylori and mdh specific for E. coli were also screened by PCR. In addition, the specimens were examined for H. pylori by immunohistochemical procedure using anti-H. pylori antibody. Helicobacter genus-specific 16S rRNA was found in 12 out of the 33 [36.4%] samples of HCC tissues, whereas none of the 6 control liver specimens were found to harbor this rRNA. The H. pylori species-specific 26 kDa protein gene was detected in 11 of the 12 [91.7%] samples positive for the Helicobacter 16S rRNA gene thus confirming the presence of H. pylori DNA in 33.3% of the HCC samples. Within these 11 HCC samples, the cag A gene was detected in only 3, whereas the vac A and mdh genes were not detected. Helicobacter pylori immunostaining was recognized in 7 HCC specimens [21.2%], which were also positive for H. pylori species-specific DNA detection by PCR with statistically very high significant association [p = 0.0001]. The presence of microscopic evidence of hepatitis [10 cases] and cirrhosis [15 cases] presented a significant association with both H. pylori DNA detection [p = 0.0320 and 0.0260 respectively] and immunoreactivity [p = 0.0075 and 0.0158 respectively]. These data indicate that the detection of H. pylori by means of molecular methods and immunohistochemistry in human HCC tissue supports the concept of the possible association between H. pylori and HCC development. However, their eventual role in hepatocarcinogenesis, although it is plausible, remains to be proven