Comparison of Conventional and Molecular Methods Used for Diagnosis of Mycobacterium Tuberculosis in Clinical Samples.

BACKGROUND: Tuberculosis (TB) is an important global public health issue, and drug resistance is the most important factor preventing its control. According to the World Health Organization, approximately 10.4 million new cases were reported worldwide in 2015, and 5% of those new cases were multidrug-resistant TB. The aim of our study is to identify rapid and accurate methods for detecting the presence of the Mycobacterium tuberculosis complex (MTBC) and its drug susceptibility in respiratory tract samples obtained from patients suspected of having TB. METHODS: A total of 140 patient samples, including 110 sputum, 20 bronchoalveolar lavage fluid, and 10 fasting gastric aspirates were evaluated in this study. The acid-fast bacilli (AFB) detection by microscopy, BACTEC mycobacteria growth indicator tube 960 (MGIT-960) liquid culture system, Löwenstein-Jensen (LJ) solid culture method, and the GenoType MTBDRplus molecular methods were applied to all samples, and the resulting data were compared. RESULTS: Among the clinical samples from patients suspected of having TB, 12% (16/140), 15% (21/140), 16% (23/140), and 14% (20/140) were positive by AFB detection, LJ conventional culture, MGIT-960 liquid culture, and PCR methods, respectively. Of the 23 strains identified by the MGIT-960 liquid culture method, 21 were MTBC, and 2 were non-tuberculous mycobacteria (NTM). Additionally, 20 of 23 culture-positive samples had positive PCR results and 3 of 23 culture-positive samples had negative PCR results. One MTBC-positive patient was determined to be negative by PCR. Only one patient was positive for rpoB and katG mutations. CONCLUSIONS: Molecular tests may be a complementary method for confirming a diagnosis of TB, considering that they yield same-day, high-sensitivity results. Due to the high specificity of PCR, positive results obtained by this test may be useful for early detection of TB. However, it would be appropriate to confirm negative results with culture and clinical findings.

Absence of the mecC gene in methicillin-resistant Staphylococcus aureus isolated from various clinical samples: The first multi-centered study in Turkey.

BACKGROUND: mecA is a predefined gene causing methicillin resistance in Staphylococcus aureus (S. aureus) isolates; however, it has been shown that some methicillin-resistant S. aureus (MRSA) strains do not carry this gene. Recently, in isolates found to be MRSA-positive but mecA-negative, a new resistance gene called mecC, which is a homolog of mecA, has been reported. This study aimed to investigate the mecC and mecA genes in MRSA strains isolated from different geographic regions in Turkey. METHODS: The sample of the study consisted of 494 MRSA strains isolated from seven geographical regions in Turkey between 2013 and 2016. The strains were obtained from 17 centers, comprising 13 university hospitals, three education and research hospitals, and one state hospital. Methicillin resistance in S. aureus strains was determined using the agar disk diffusion method with a cefoxitin disk and the agar dilution method with oxacillin. The mecC and mecA genes in MRSA strains was investigated by Polymerase Chain Reaction (PCR). RESULTS: Of the MRSA strains investigated, 47.9% were isolated from intensive care units. Concerning sample type, 36.7% were detected in the respiratory tract (tracheal aspirate, sputum, etc.), 24.8% in blood, 18.7% in skin and soft tissues, 9.3% in nasal swabs, 5.4% in urine, 4.1% in ears, and 1% in sterile body fluid. Using PCR, mecC was not identified in any of the S. aureus strains isolated from different clinical microbiology laboratories. mecA gene positivity was found in 315 of the MRSA strains (63.8%). Staphylococcal Cassette Chromosome mec (SCCmec) type was identified in 232 strains (46.9%), of which 136 (58.7%) were type II, 75 (32.4%) were type IV, 12 (5.1%) were type IIIb, six (2.5%) were type I, and three (1.3%) were type III. CONCLUSION: This is the first multi-centered study to investigate MRSA strains isolated from different regions in Turkey. The mecC gene was not detected in any of the MRSA strains. We believe that this study will constitute an important basis for monitoring possible future changes.

Daptomycin versus Vancomycin in an Enterococcus faecalis Endophthalmitis Rabbit Model.

PURPOSE: To compare bactericidal activities of daptomycin (DAP) and vancomycin (VAN) in an experimental rabbit model of Enterococcus faecalis endophthalmitis. MATERIALS AND METHODS: The right vitreous cavities of 24 New Zealand rabbits were inoculated with 100 colony-forming units of E. faecalis; and after 24 h, rabbits were randomly divided into three groups. DAP group (n = 8, 0.2 mg/0.05 ml intravitreally), VAN group (n = 8, 1 mg/0.05 ml intravitreally) and balanced salt solution group (BSS, n = 8, 0.05 ml intravitreally). Clinical examination scores were recorded, and vitreous aspirates were obtained for microbiological analysis on days 0, 1, 2, 3 and 4. Rabbits were sacrificed, and the eyes were enucleated for histopathological assessment. RESULTS: There was no difference between the DAP, VAN and BSS groups in terms of the clinical grading of endophthalmitis 24 h after the inoculation. The bacterial counts were similar between the VAN and DAP groups except on day 1, where it was significantly lower than those in the VAN group (p = 0.003). On day 4, 62% of the eyes treated with DAP, and 50% of the eyes treated with VAN were sterilized. All of the eyes from the BSS group showed increasing bacterial growth from day 0 to day 4. There was no difference between the DAP and VAN groups in terms of the histopathological and clinical examination scores, while they were significantly lower than those in the BSS group. CONCLUSIONS: This study demonstrates evidence of the effectiveness of DAP for the treatment of experimental E. faecalis endophthalmitis.