Infection, Epidemiology And Medicine
Volume:4 Issue: 3, Summer 2018

Pertussis is an important vaccine preventable disease. It is still a major cause of infant morbidity and mortality in the world. Although the incidence of pertussis was successfully reduced after vaccination, the resurgence of pertussis has been reported in many countries even with high vaccination coverage. Genetic variation in virulence factors is one of the important causes for pertussis reemergence. We investigated genetic characteristics and allele types of 3 important virulence associated genes, including ptxC, tcfA, and fhaB in clinical B. pertussis isolates collected from different provinces of Iran and vaccine strains. Genomic DNA was extracted and ptxC, tcfA, and fhaB gene regions were amplified, using specific PCR primer. DNA sequencing was performed and data were analyzed. ptxC2, tcfA2, and fhaB1 were the dominant alleles with 87.5%, 97.5%, and 97.5% frequencies, respectively. Vaccine strains B. pertussis 134 and B. pertussis 509 contain the genotypes ptxC2- tcfA2-fhaB1 and ptxC2- tcfA2-fhaB1. Results for dominant alleles in ptxC2, tcfA2, and fhaB1 genes in Iran are consistent with dominant alleles of other countries such as Netherland, Finland, and Italy. It seems that ptxC2, tcfA2, and fhaB1 are the dominant circulating alleles in many countries after vaccination period, while vaccine strains have different alleles occasionally. More reported cases in recent years despite high coverage vaccination in Iran and genetic distances between clinical and vaccine strains suggest that antigenic changes in virulence factors possibly have an important role in the survival and evolution of the bacteria.

Diagnosis of Listeria monocytogenes infections is critical for epidemiological study and prevention of diseases. This study aimed at identifying L. monocytogenes isolates, using Loop-Mediated Isothermal Amplification Method (LAMP). Listeria strains were obtained from clinical and seafood specimen. All listeria strains were identified by standard microbiological and biochemical tests. The LAMP assay was performed at 65°C with a detection limit of 2.5 ng/μl for 46 min. Specific primers for the hylA gene were used to identify L. monocytogenes. The specificity of the assay was assessed, using DNA from L. monocytogenes ATCC 7644 and L. ivanovii ATCC 19119 and non-Listeria strains. Sensitivity of the LAMP assay was compared with polymerase chain reaction (PCR) method. Amplification LAMP products were visualized via calcein and manganous ions as well as agarose gel electrophoresis. A total of 191 samples were obtained, including clinical and food samples. Then, 21 (10.9%) isolates were recovered from specimens. The LAMP results showed high sensitivity (97.2%) and specificity (100 %). The LAMP assay was higher sensitive than of the PCR assay. This data showed that this method could be used as a sensitive, rapid, and simple identification tool for diagnosis of L. monocytogenes isolates and it may be suitable for epidemiological study plans.

Vibrio cholerae is one of the intestinal gram-negative bacteria, causing cholera disease in developing countries; the two serogroups of O1 and O139 are the main causes of diarrhea. The bacteria resistance pattern to antibiotics varies in different countries. The aim of this study was to determine the resistance pattern of the isolates to representative antibiotics. A total of 20 V. cholerae clinical strains were isolated from patients with cholera in Sistan and Baluchestan province of Iran during 2012-2013 outbreaks. After being identified by biochemical and molecular techniques, antibiotic susceptibility testing was performed for 6 antibiotics according to CLSI standards. Then, minimum inhibitory concentration (MIC) was also determined for tetracycline and erythromycin, using E-Test method. All of the isolates were EL Tor biotype, O1 serogroup, and Inaba serotype. All of isolates were resistant to erythromycin and nalidixic acid, and 50% were resistant to tetracycline, while no resistance was observed against to ciprofloxacin, gentamicin, and ampicillin. The sensitivity of all clinical isolates to antibiotics mentioned suggests that these antibiotics can likely be used in cholera disease treatment*

Colistin resistant Acinetobacter baumannii strains have become an important treat in nosocomial infection control. The reliable detection of these strains plays a critical role in treatment procures. The aim of this study was to evaluate the three different methods in detection of colistin resistant A. baumannii strains. Eighty-three A. baumannii strains were isolated from hospitalized patients of a teaching hospital in Tehran during 1 year (2016-2017). All isolates were genetically confirmed by Polymerase Chain Reaction (PCR). The resistance to colistin was determined with disc diffusion, E-test, and micro broth dilution method. According to the results of micro broth dilution as a gold standard, 43% of the isolates were resistant to colistin, while this percentage was 23% and 44% through E-test and disc diffusion methods, respectively. The positive and negative predictive value (PPV and NPV) of this method was 43% and 57%, respectively. The sensitivity and NPV index of E-test for the detection of colistin resistant strains was 76% and 68%. Detection of colistin MIC by E-test strips has been commonly used in clinical laboratories to recognize the colistin susceptible strains. The NPV and sensitivity of E-test method demonstrated that this method has inefficacy to accurate determination of colistin susceptible strains. Thus, using standard protocol micro broth dilution with qualified materials should be stabilized and replaced instead of disc diffusion or even using E-test in clinical laboratories.

Helicobacter pylori is a pathogen that can be colonized in the stomach. Most laboratories only use IgG and not IgA antibody to diagnose infection. The aim of this study was to compare both IgG and IgA-antibodies level for the detection H. pylori. The presence of IgG and IgA antibodies in the sera of the 517 patients suspected to H. pylori infection was evaluated by Enzyme-Linked Immunoadsordent Assays (ELISA) method. The positive cases of infection on the basis of IgG and IgA titers were 68% and 27%, respectively. Also, 7% of the patients with IgG negative were IgA positive. The comparison of antibody responses in our patients indicate that the sensitivity of IgA level is lower than IgG ELISA and both antibody titers must be evaluated for the identification of infection. In some cases, patients with IgG negative may have IgA positive assays; therefore, in the serological diagnostic process and without endoscopy, IgG results in association with IgA against H. pylori will be completed.

Transportation of clinical samples and long-term recoverability of fungal strains are critical to epidemiological studies. In addition, the study of fungi often requires the use of living pure cultures. The aim of this study was to evaluate the methods used to preserve culture collections of dermatophytes, consisted of storage in sterile distilled water, cryopreservation with glycerol, preserving in tryptic soy broth (TSB), and freezing mycobiotic agar. in this experimental study, ninety-two dermatophyte isolates belonged to 10 species were tested. The freezing protocol was done in 4 forms of sterile distilled water, cryopreservation with glycerol, freezing mycobiotic agar, and preserving in TSB. The viability of the dermatophytes species was assessed after 3 years at morphological (macro and microscopic features), physiological (Using Dermatophyte Test Medium; DTM, urease test media, and the hair perforation test), and genetic levels by restriction fragment length polymorphism (RFLP). The survival rate was 84 out of 92 water stored fungal strains (91.3%) and 81 out of 92 mycobiotic agar stored strains (88.0%) and 75 out of 92 glycerol 40% stored strains (81.5%) and 43 out of 92 TSB stored fungal strains (46.7%). Overall, more than 88% of the strains survived in the distilled water storage and freezing mycobiotic agar, methods, while storage in TSB had the least success in the maintenance of dermatophytes. The procedure to preserve cultures in sterile distilled water is reliable, simple, and inexpensive.