Authors:Davood Darban-Sarokhalil, Abbas Fooladi, Zakaria Bameri, Mohammad Nasiri, and Mohammad Feizabadi
Cytochrome P450 CYP141 is an intermediary metabolic and respiratory protein that interferes with oxidation reduction in Mycobacterium tuberculosis. This conserved protein has also been debated as a hypothetical target for therapeutics. We used the sequences of CYP141 gene to develop a PCR for rapid detection of Mycobacterium tuberculosis from respiratory specimens. The sensitivity of this PCR for culture positive-smear positive and culture positive-smear negative samples were 92% and 62.5%, respectively. The overall sensitivity and specificity of this PCR was 85.7% and 97.8%. As compared with other studies, it appears that the CYP141 gene is a good target for direct detection of M. tuberculosis from respiratory specimens.
Klebsiella spp. are among the most frequently isolated bacteria from burn wounds. These organisms are among the most important opportunistic pathogens, causing hospital-acquired and healthcare-associated infections worldwide. Limited information is available about prevalence of AmpC-producing Klebsiella pneumoniae from burn patients. Therefore, the aim of this study was to determine the characterization of AmpC beta-lactamase among K. pneumoniae isolated from burn patients. Samples were collected from wound specimens of patients with burn injury from a burn hospital in Tehran during 18 months (March 2015 to August 2016). For phenotypic detection of AmpC beta-lactamase, disk diffusion method with cefoxitin was used for screening, AmpC disk test and boronic acid inhibitor-based method were used as confirmatory tests. Polymerase chain reaction (PCR) was performed to screen all isolates with AmpC genes including ACCM, DHAM, EBCM, FOXM, MOXM, and CITM. Finally, PCR products were validated using sequencing. During this study, 102 isolates of K. pneumoniae were collected. Among these isolates, 52.9% suspected as AmpC producer by disk agar diffusion cefoxitin screening method. By confirmatory phenotypic methods, 19.6% of isolates considered as AmpC producer. Molecular analysis revealed 43.1% of cefoxitin-resistant isolates harbored at least one of the AmpC genes including CITM (22.5%), EBCM (21.5%), DHAM (7.8%), and FOXM (0.98%). In addition, 5.8% of isolates harbored two AmpC genes and 2.9% harbored three AmpC genes. In conclusion, K. pneumoniae is becoming a serious problem in burn patients. Accurate and precise methods and guidelines should be designed for detection of antibiotic-resistant mechanisms. Our data showed the high rate of AmpC beta-lactamase among K. pneumoniae isolated from burn patients, which limit the treatment options. Therefore, the results of this study can provide evidence to help for appropriate treatment of burn patients.
Authors:Amin Khoshbayan, Aref Shariati, Ehsanollah Ghaznavi-Rad, Alex van Belkum, and Davood Darban-Sarokhalil
Methicillin-resistant Staphylococcus aureus (MRSA) is one of the major pathogens in Iran with a high prevalence and a high level of antibiotic resistance. Ceftaroline is a fifth generation cephalosporin binding and inhibiting penicillin binding protein (PBP2a).
In the present study, 228 clinical MRSA isolates were collected from four cities of Iran and their susceptibility to ceftaroline was evaluated by E-test and the disk diffusion method.
Our results showed a high susceptibility rate (97.3%) to ceftaroline in MRSA strains from Iran. Six isolates were found to be ceftaroline non-susceptible (CPT-NS) with Minimum inhibitory concentration (MIC) ≥2 µg/mL. All CPT-NS isolates were isolated from blood and tracheal aspirate and belonged to SCCmec type III as well as agr type I and were all susceptible to vancomycin. Out of six isolates, three, two and one belonged to spa type t030, t4864, and t969, respectively. Vancomycin, quinupristin/dalfopristin, linezolid, chloramphenicol, and tigecycline were the most active agents against CPT-NS isolates.
Due to the broad-spectrum activity and low toxicity of ceftaroline as well as the increased rate of vancomycin resistance among MRSA strains in recent years, ceftaroline can be considered as a novel approach to treat MRSA-induced infections.
Colistin is one of the last remaining active antibiotics against multidrug resistant Gram-negative bacteria. However, several recent studies reported colistin-resistant (ColR) Acinetobacter baumannii from different countries. In the current study, we investigated molecular mechanisms involved in colistin resistance in A. baumannii isolates from different clinical samples.
A total of 110 clinical A. baumannii isolates were collected from two hospitals in Tehran. Minimum inhibitory concentrations (MICs) were determined by broth microdilution according to the Clinical and Laboratory Standards Institute. For the ColR isolates, mutation was detected in pmrA, pmrB, lpxA, lpxC, and lpxD genes using the polymerase chain reaction (PCR) and sequencing. Moreover, the relative expression of the pmrC gene was calculated using quantitative reverse transcription PCR. Three colistin resistant isolates were identified with MIC between 8 and 16 μg/mL and were resistant to all the tested antimicrobial agents. All the three isolates had a mutation in the pmrB, pmrA, lpxA, lpxD, and lpxC genes. Moreover, the overexpression of pmrC gene was observed in all isolates. Our results showed that the upregulation of the PmrAB two component system was the primary mechanism linked to colistin resistance among the studied colistin resistant A. baumannii isolates.
Authors:Somayeh Fard, Bizhan Nomanpour, Bahram Fatolahzadeh, Ashraf Mobarez, Davood Darban-Sarokhalil, Abbas Fooladi, Willem Leeuwen, and Mohammad Feizabadi
Legionella pneumophila is an important etiological agent in both hospital and community acquired pneumonia. The sensitivity of culture for isolation of L. pneumophila from clinical specimens is low and time consuming. Similar problem also exists when the method of direct immunofluorescence is used. To detect this organism quantitatively from respiratory specimens, a Taq Man based real-time PCR targeting the mip sequence was developed. Both real-time PCR and culture methods were applied on 262 respiratory specimens from 262 ICU patients with pneumonia admitted to 5 different hospitals in Tehran. The results of real-time PCR were compared with those obtained by culture. Real-time PCR and culture found 12 and 4 specimens, respectively, as positive for L. pneumophila. Its technical specificity (100%) was checked against a panel of microorganisms consisting of both Gram-positive and Gram-negative bacteria. Our real-time PCR assay showed high sensitivity (100%) and specificity (96.9%) and could detect 200 organisms per ml from respiratory specimens. Using real-time PCR as a screening method, the frequency of nosocomial pneumonia with L. pneumophila at Tehran hospitals was estimated as 4.58%.
Methicillin-resistant Staphylococcus aureus (MRSA) has been one of the most important antibiotic-resistant pathogen in many parts of the world over the past decades. This cross-sectional study was conducted to investigate MRSA isolated between July 2013 and July 2014 in Karaj, Iran. All tested isolates were collected in teaching hospitals from personnel, patients, and surfaces and each MRSA was analyzed by SCCmec and spa typing. Antibiotic susceptibility testing was accomplished by disk diffusion method. Out of 49 MRSA isolates from the Karaj’s teaching hospitals, 82%, 10%, and 6% of the isolates were SCCmec types III, II, and I, respectively. The main spa type in this study was spa t030 with frequency as high as 75.5% from intensive care unit (ICU) of the hospitals and high rate of resistance to rifampicin (53%) was found in MRSA isolates. In conclusion, high frequency of spa t030 with SCCmec type III and MRSA phenotype illustrated circulating of one of the antibiotic-resistant strains in ICU of Karaj’s teaching hospitals and emphasizes the need for ongoing molecular surveillance, antibiotic susceptibility monitoring, and infection control.