[Evaluation of the molecular assays for detection of Mycobacterium tuberculosis complex in extrapulmonary specimens]. / Akciger disi klinik örneklerden Mycobacterium tuberculosis kompleks tanimlanmasinda moleküler yöntemlerin degerlendirilmesi.

INTRODUCTION: Tuberculosis, one of the most common and deadly infectious diseases, mainly affects the lungs, but can involve all tissues and organs. Diagnosis of extrapulmonary tuberculosis may be more challenging than pulmonary tuberculosis, which may lead to delay in starting treatment. In our study, it was aimed to determine the diagnostic value of FluoroType MTB, GeneXpert MTB/RIF, GeneXpert MTB/RIF Ultra molecular tests in extrapulmonary specimens. MATERIALS AND METHODS: Extrapulmonary clinical materials were subjected to Kinyoun staining for acid fast bacilli and cultivation was done on Lowenstein Jensen media and BACTEC MGIT 960 automated culture system (BD). Results were compared with FluoroType MTB and GeneXpert MTB/RIF test results (2018) and with FluoroType MTB and GeneXpert MTB/RIF Ultra tests results (2019). RESULT: A total number of 892 extrapulmonary specimens were enrolled in the study. In 2018, positivity was detected in 16 (3.4%) of 467 specimens by molecular methods. Compared with culture; the sensitivity and specifity of the FluoroType MTB were 76.92%, 98.88% respectively; the sensitivity and specifity of GeneXpert MTB/RIF were 100%, 98.96% respectively. In 2019, positivity was detected in 15 (3.5%) of 425 specimens by molecular methods. The sensitivity and specifity of the FluoroType MTB was 62.5%, 98.05% respectively; the sensitivity and specificity of GeneXpert MTB/RIF Ultra was 100%, 99.36% respectively. CONCLUSIONS: Although culture is the gold standard method in the diagnosis of tuberculosis, the patients were diagnosed only with polymerase chain reaction positivity, supported by the patient's clinical, radiology and pathology results in seven cases. The diagnosis of tuberculosis in extrapulmonary specimens is more challenging than in pulmonary specimens due to low bacillary burden and requiring invasive procedures for sampling. It should be considered that molecular methods have a critical role in diagnosis.

Factors Associated with 28-day Critical Illness Development During the First Wave of COVID-19.

Objective: This study aimed to define the predictors of critical illness development within 28 days postadmission during the first wave of the COVID-19 pandemic. Materials and Methods: We conducted a prospective cohort study including 477 PCR-positive COVID-19 patients admitted to a tertiary care hospital in Istanbul from March 12 to May 12, 2020. Results: The most common presenting symptoms were cough, dyspnea, and fatigue. Critical illness developed in 45 (9.4%; 95% CI=7.0%-12.4%) patients. In the multivariable analysis, age (hazard ratio (HR)=1.05, p<0.001), number of comorbidities (HR=1.33, p=0.02), procalcitonin ≥0.25 µg/L (HR=2.12, p=0.03) and lactate dehydrogenase (LDH) ≥350 U/L (HR=2.04, p=0.03) were independently associated with critical illness development. The World Health Organization (WHO) ordinal scale for clinical improvement on admission was the strongest predictor of critical illness (HR=4.15, p<0.001). The patients hospitalized at the end of the study period had a much better prognosis compared to the patients hospitalized at the beginning (HR=0.14; p=0.02). The C-index of the model was 0.92. Conclusion: Age, comorbidity number, the WHO scale, LDH, and procalcitonin were independently associated with critical illness development. Mortality from COVID-19 seemed to be decreasing as the first wave of the pandemic advanced. Graphic Abstract: Graphic Abstract.

The effect of immunization with inactivated SARS-CoV-2 vaccine (CoronaVac) and/or SARS-CoV-2 infection on antibody levels, plasmablasts, long-lived-plasma-cells, and IFN-γ release by natural killer cells.

OBJECTIVES: We evaluated the antibody response, natural killer cell response and B cell phenotypes in healthcare workers (HCW) who are vaccinated with two doses of CoronaVac with or without documented SARS-CoV-2 infection and unvaccinated HCWs with SARS-CoV-2 infection. METHODS: HCWs were divided into four groups: vaccine only (VO), vaccine after SARS-CoV-2 infection (VAI), SARS-CoV-2 infection only (IO), and SARS-CoV-2 infection after vaccine (IAV). Anti-SARS-CoV-2 spike protein (Anti-S) antibodies were measured by Elecsys Anti-SARS-CoV-2 S ELISA kit. Memory B cells (CD19+CD27+), plasmablast B cells (CD19+CD138+) and long-lived plasma cells (LLPC; CD138+CD19-) were measured by flow cytometry in 74 patients. Interferon gamma (IFN-γ) release by natural killer (NK) cells were measured by NKVue Test (NKMAX, Republic of Korea) in 76 patients. RT-PCR was performed with Bio-speedy® COVID-19 qPCR detection kit, Version 2 (Bioexen LTD, Istanbul, Turkey). RESULTS: The Anti-S antibodies were detectable in all HCWs (n: 224). The median Anti-S titers (BAU/mL) was significantly higher in VAI (620 25-75% 373-1341) compared to VO (136, 25-75% 85-283) and IO (111, 25-75% 54-413, p < 0.01). VAI group had significantly lower percentage of plasmablasts (2.9; 0-8.7) compared to VO (6.8; 3.5-12.0) and IO (9.9; 4.7-47.5, p < 0.01) (n:74). Percentage of LLPCs in groups VO, VAI and IO was similar. There was no difference of IFN-γ levels between the study groups (n: 76). CONCLUSION: The antibody response was similar between uninfected vaccinated HCWs and unvaccinated HCWs who had natural infection. HCWs who had two doses of CoronaVac either before or after the natural SARS-CoV-2 infection elicited significantly higher antibody responses compared to uninfected vaccinated HCWs. The lower percentages of plasmablasts in the VAI group may indicate their migration to lymph nodes and initiation of the germinal center reaction phase. IFN-γ response did not differ among the groups.

Differences between radiological findings of COVID-19 and non-COVID-19 infections in pediatric patients.

BACKGROUND: This study aimed to reveal the differences between coronavirus disease 2019 (COVID-19) infections and non-COVID-19 respiratory tract infections in pediatric patients. METHODS: Sixty pediatric patients admitted to the hospital between March 11, 2020 and April 15, 2020 with respiratory tract infections were evaluated retrospectively. Among them, 20 patients with reverse transcription-polymerase chain reaction (RT-PCR) tests and chest computed tomography (CT) examinations were included in the study. According to the RT-PCR test results, the patients were divided into the COVID-19 and non-COVID-19 groups. The clinical observations, laboratory results, and radiological features from the two groups were then compared. RESULTS: According to the RT-PCR test results, 12 patients were assigned to the COVID-19 group and 8 to the non-COVID-19 group. There were no significant differences between the two groups in terms of clinical or laboratory features. In terms of radiological features, the presence of bronchiectasis and peribronchial thickening was statistically significantly higher in the non-COVID-19 group (P = 0.010 and P = 0.010, respectively). CONCLUSIONS: In pediatric cases, diagnosing COVID-19 using radiological imaging methods plays an important role in determining the correct treatment approach by eliminating the possibility of other infections.

The Association of Thyroid Hormone Changes with Inflammatory Status and Prognosis in COVID-19.

BACKGROUND: COVID-19 infection may have multiorgan effects in addition to effects on the lungs and immune system. Recently, studies have found thyroid function abnormalities in COVID-19 cases which were interpreted as euthyroid sick syndrome (ESS) or destructive thyroiditis. Therefore, in this study, we aimed to evaluate the thyroid function status and thyroid autoimmunity in COVID-19 patients. Material and Method. 205 patients were included. The medical history and laboratory parameters at admission were collected from medical records. Serum thyroid-stimulating hormone (TSH), free thyroxine (FT4), free triiodothyronine (FT3), thyroid peroxidase antibody, and thyroglobulin antibody were measured, and patients were classified according to thyroid function status. RESULTS: 34.1% of the patients were euthyroid. Length of hospitalization (p < 0.001), rate of oxygen demand (p < 0.001), and intensive care unit (ICU) admission (p=0.022) were lower, and none of the euthyroid patients died. 108 (52.6%) patients were classified to have ESS, 57 were classified as mild, and 51 were moderate. The inflammatory parameters were higher in patients with moderate ESS. In cluster analysis, a high-risk group with a lower median FT3 value (median = 2.34 ng/L; IQR = 0.86), a higher median FT4 value (median = 1.04 ng/dL; IQR = 0.33), and a lower median TSH value (median = 0.62 mIU/L; IQR = 0.59) included 8 of 9 died patients and 25 of the 31 patients that were admitted to ICU. Discussion. Length of hospitalization, oxygen demand, ICU admission, and mortality were lower in euthyroid patients. Moreover, none of the euthyroid patients died. In conclusion, evaluation of thyroid function tests during COVID-19 infection may give information about the prognosis of disease.

Comparison of intravenous and non-intravenous antibiotic regimens in eradication of P. aeruginosa and MRSA in cystic fibrosis.

BACKGROUND: Chronic pulmonary infection is the leading cause of mortality and morbidity in patients with cystic fibrosis (CF). The most common pathogens isolated in CF are Staphylococcus aureus (SA) and Pseudomonas aeruginosa (PA). Chronic infection of PA and methicillin-resistant S. aureus (MRSA) are associated with worse survival and antibiotic eradication treatment is recommended for both. This study compared the outcomes between intravenous (IV) and non-IV antibiotics in eradication of PA and MRSA. METHODS: This was a single-center retrospective study. All respiratory specimen cultures of 309 CF patients and eradication regimens between 2015 and 2019 were reviewed. Patients received eradication treatment in case of first ever isolation or new isolation after being infection-free ≥1 year. The primary analysis was the comparison of the percentage of successful eradication after receiving IV and non-IV eradication regimens. Demographic and clinical risk factors for eradication failure were also analyzed. RESULTS: One hundred and two patients with PA isolations and 48 patients with MRSA were analyzed. At 1 year, 21.6% in PA group and 35.4% in MRSA group were successfully eradicated. There was not any statistically significant difference between IV versus non-IV antibiotic regimens on eradication in either group. Additionally, none of the clinical risk factors was significantly associated with eradication failure in PA and MRSA groups. CONCLUSION: In the eradication of PA and MRSA, IV and non-IV treatment regimens did not show any superiority to one another. Non-parenteral eradication could be a better option considering the cost-effectiveness and the treatment burden of IV treatments due to hospitalization and the need for IV access.

Tuberculosis and COVID-19: An overlapping situation during pandemic.

INTRODUCTION: The novel coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the coronavirus disease 2019 (COVID-19). First COVID-19 case was detected in March, 10, 2020 in Turkey and as of May, 18, 2020 148,067 cases have been identified and 4096 citizens have died. Tuberculosis (TB) is a worldwide public health concern, incidence of tuberculosis (per 100,000 people) in Turkey was reported at 14, 1 in 2018. During pandemic COVID-19 was the main concern in every clinic and as we discuss here overlapping respiratory diseases may result in delaying of the diagnosis and treatment. METHODOLOGY: There were 4605 respiratory samples examined between March 23 and May 18 for COVID-19 and 185 samples for Mycobacterium tuberculosis in our laboratory. The Xpert Ultra assay was performed for the diagnosis of pulmonary tuberculosis; SARS-CoV-2 RNA was determined by real-time PCR (RT-PCR) analysis in combined nasopharyngeal and deep oropharyngeal swabs of suspected cases of COVID-19. RESULTS: Both of SARS-CoV-2 and M. tuberculosis tests were requested on the clinical and radiological grounds in 30 patients. Here we discussed 2 patients who were both COVID-19 and TB positive. One patient already diagnosed with tuberculosis become COVID-19 positive during hospitalization and another patient suspected and treated for COVID-19 received the final diagnosis of pulmonary TB and Human Immunodeficiency Virus infection. CONCLUSIONS: We want to emphasize that while considering COVID-19 primarily during these pandemic days, we should not forget one of the "great imitators", tuberculosis within differential diagnoses.

Relationship of the cycle threshold values of SARS-CoV-2 polymerase chain reaction and total severity score of computerized tomography in patients with COVID 19.

AIM: Studies analyzing viral load in COVID-19 patients and any data that compare viral load with chest computerized tomography (CT) severity are limited. This study aimed to evaluate the severity of chest CT in reverse transcriptase polymerase chain reaction (RT-PCR)-positive patients and factors associated with it. METHODOLOGY: SARS-CoV-2 RNA was extracted from nasopharyngeal swab samples by using Bio-speedy viral nucleic acid buffer. The RT-PCR tests were performed with primers and probes targeting the RdRp gene (Bioexen LTD, Turkey) and results were quantified as cycle threshold (Ct) values. Chest CT of SARS-CoV-2 RNA-positive patients (n = 730) in a period from 22 March to 20 May 2020 were evaluated. The total severity score (TSS) of chest CT ranged 0-20 and was calculated by summing up the degree of acute lung inflammation lesion involvement of each of the five lung lobes. RESULTS: Of the 284 patients who were hospitalized, 27 (9.5%) of them died. Of 236 (32.3%) patients, there were no findings on CT and 216 (91.5%) of them were outpatients (median age 35 years). TSS was significantly higher in hospitalized patients; 5.3% had severe changes. Ct values were lower among outpatients, indicating higher viral load. An inverse relation between viral load and TSS was detected in both groups. CT severity was related to age, and older patients had higher TSS (p < 0.01). CONCLUSION: Viral load was not a critical factor for hospitalization and mortality. Outpatients had considerable amounts of virus in their nasopharynx, which made them contagious to their contacts. Viral load is important in detecting early stages of COVID-19, to minimize potential spread, whereas chest CT can help identify cases requiring extensive medical care.

Use of T cell-based diagnosis of tuberculosis infection to optimize interpretation of tuberculin skin testing for child tuberculosis contacts.

BACKGROUND: Treatment of recent tuberculosis infection in children aged <2 years is essential, because of high risk of progression to disease, but diagnosis is hindered by the inaccuracy of the tuberculin skin test (TST). More-accurate T cell-based tests of infection could enhance diagnosis by optimizing interpretation of the TST results. METHODS: A total of 979 child tuberculosis contacts in Istanbul underwent the TST and enzyme-linked immunospot assay. Using enzyme-linked immunospot test results as a reference standard, we assessed the effect of age and bacille Calmette-Guérin (BCG) vaccination on the sensitivity and specificity of the TST, and we computed the optimal TST cutoff points, using receiver operating characteristic curves. RESULTS: With a TST cutoff point of >or=10 mm, the sensitivity of the TST was 66% for children aged <2 years, which was lower than that for older children (P= .006). Specificity was 75% for BCG-vaccinated children, compared with 92% for unvaccinated children (P= .001). Optimal cutoff points improved TST specificity for children with 1 BCG scar, with little loss of sensitivity. Despite the use of optimal cutoff points, TST sensitivity remained <70% for children aged <2 years, specificity remained <87% for BCG-vaccinated children aged >or=2 years, and overall accuracy was low for children with >1 BCG scar. CONCLUSIONS: Negative results of the TST cannot exclude tuberculosis infection for child tuberculosis contacts aged <2 years, which supports the use of preventive therapy regardless of the TST results for this age group. In children aged >or=2 years, the accuracy of the TST can be improved by adjustment of cutoff points for BCG-vaccinated children but remains poor for children with >1 BCG scar. This methodology can define optimal TST cutoff points for diagnosis of tuberculosis infection tailored to target populations.

Extended-spectrum beta-lactamase-producing Klebsiella pneumoniae in paediatric wards: a nested case-control study.

AIM: A high rate (48.6%) of extended spectrum beta-lactamase production among Klebsiella pneumoniae (ESBL-KP) clinical isolates in the paediatric wards of our hospital prompted the introduction of enhanced infection control measures, and after the implementation of these measures, we instituted a prospective surveillance programme, with a nested case-control study to determine the risk factors for rectal colonisation by ESBL-KP. METHODS: Over a 1-year period, rectal swabs from patients and samples from the environment and the hands of health-care workers were cultured. Strain typing of ESBL-KP isolates was performed using pulsed-field gel electrophoresis. Characteristics of patients who were colonised with ESBL-KP during hospital stay were compared with those of patients who remained negative for ESBL-KP. Multivariate analysis was performed with model-building using stepwise logistic regression to determine independent risk factors for ESBL-KP acquisition. RESULTS: Forty (18.5%) of 216 patients became colonised with ESBL-KP. The strongest independent predictors of ESBL-KP colonisation were mechanical ventilation (odds ratio (OR): 4.28) and hospitalisation for longer than 14 days (OR: 6.97). Genotyping of the isolates indicated probable patient-to-patient transmission; however, we could not determine the route of this spread. During the study period, a 1.6% rate of ESBL-KP clinical infection per 500 patient admissions was observed, in contrast to a 7% rate in the previous year. CONCLUSIONS: Prolonged length of stay and mechanical ventilation were independent predictors of ESBL-KP colonisation. Enhanced infection control measures, antimicrobial stewardship and screening for rectal carriage were associated with a substantial decrease in paediatric units.

Sulfatide mediates attachment of Pseudomonas aeruginosa to human pharyngeal epithelial cells.

Pseudomonas aeruginosa infections are particularly common in people with cystic fibrosis and despite regular treatment with antibiotics, lung damage due to chronic infection with P. aeruginosa remains the major cause of death in those patients. In order to initiate an infection, P. aeruginosa needs contact with the respiratory epithelial surface and by means of its adhesins i.e., fimbria, hemagglutinins,etc., it recognizes and adheres to the corresponding epithelial receptors. We treated P. aeruginosa strains isolated from sputum of cystic fibrosis patients with several glycolipids such as sulfatide, sulfated ganglioside mixture (GM1a, GD1b, GT1b), asialo-GM1 and galactocerebrosides to determine their effect on attachment with pharyngeal epithelial cells. Sulfated ganglioside mixture and sulfatide inhibited the attachment of P. aeruginosa significantly, whereas asialo-GM1, Gal-Cer and sodium sulfite had no effect on attachment inhibition. This finding suggests that sulfated glycoconjugates found in the extracellular matrix, in mucus and on the surface of epithelial cells of human trachea and lung mediates attachment of P. aeruginosa.

Epidemiology of candidemia in a Turkish tertiary care hospital.

In order to determine the local epidemiology of candidemia, Candida strains isolated between 1994 and 2000 were identified to species level; antifungal resistance patterns and DNA fingerprints were analyzed. Identification of Candida strains (n: 140) was performed with germ tube test and carbohydrate assimilation reactions. Minimal inhibitory concentrations were determined using a commercial test for 5-flucytosine and the broth macrodilution method according to NCCLS for fluconazole and amphotericin B. Molecular relatedness was determined by restriction endonuclease analysis of genomic DNA followed by probe hybridization. C. albicans (37.2%), C. parapsilosis (32.2%), and C. tropicalis (12.2%) comprised 114 (81.4%) of 140 isolates. Susceptibility tests did not reveal resistance to amphotericin B in any of the Candida isolates. Fluconazole resistance was detected in one isolate of C. krusei, and 5-flucytosine resistance in two C. tropicalis isolates and one C. albicans isolate. Significantly higher frequency of clusters with identical strains in C. parapsilosis and C. tropicalis was detected compared to C. albicans. Pediatric wards are particularly important in the nosocomial transmission of non-albicans candida species.

The low rate of methicillin-resistant Staphylococcus aureus in Turkish children.

During a 6-month period, swab samples were obtained from the nares, axilla and perineum of 1,000 children, age 0 to 16 years, who were attending a pediatric outpatient clinic. Staphylococcus aureus was isolated in 173 of the children. Only one child, a 35-day-old boy who had remained at the neonatal intensive care unit for 1 week after birth, was identified as a carrier of methicillin-resistant S. aureus. Except in diagnosed cases of allergic rhinitis, potential predisposing factors for colonization with S. aureus in our sample were comparable to those in non-colonized children.

[Comparison of antimicrobial resistance patterns of enterotoxin gene positive and negative Bacteroides fragilis isolates]. / Enterotoksin geni pozitif ve negatif Bacteroides fragilis izolatlarinin antibiyotiklere direnç durumlarinin karsilastirilmasi.

Some of the Bacteroides fragilis strains produce enterotoxin named fragilysin which is accepted as a virulence factor. In this study, the presence of enterotoxin genes (bft) in clinical B. fragilis strains has been investigated and the antimicrobial resistance patterns of bft positive and negative isolates have been compared. B. fragilis strains isolated from different clinical samples were identified by conventional methods and API 20A system, and the presence of bft genes were searched by using BF3/BF4 primers in polymerase chain reaction. A total of 100 B. fragilis strains of which 50 bft gene positive and 50 bft gene negative were included to the study, and their antimicrobial susceptibilities were determined by agar dilution method as recommended by NCCLS (M11-A4). Of 100 strains, 71 (34 bft negative, 37 bft positive) have been isolated from the stool, and 29 (16 bft negative, 13 bft positive) have been isolated from other specimens (blood, abscess, pleural and peritoneal fluids). beta-lactamase production was detected in 96% of enterotoxigenic B. fragilis (ETBF) and 95% of non-toxigenic strains, and all tested strains were found to be susceptible to amoxicillin/clavulanic acid, imipenem and metronidazole. The resistance rates (with MIC90 values) of bft positive isolates against the other antibiotics were as follows; 96% (256 microg/ml) for ampicillin, 16% (256 microg/ml) for piperacillin, 8% (32 microg/ml) for cefoxitin, 24% (> 256 microg/ml) for clindamycin, 74% (64 microg/ml) for tetracycline and 0% (8 microg/ml) for chloramphenicol. These rates were found as follows for bft negative strains; 95% (256 microg/ml) for ampicillin, 6% (64 microg/ml) for piperacillin, 6% (32 microg/ml) for cefoxitin, 38% (> 256 microg/ml) for clindamycin, 64% (64 microg/ml) for tetracycline and 4% (8 microg/ml) for chloramphenicol. Although the resistance rates and MIC90 values of bft positive strains against the antimicrobials seemed to be higher, there were no statistically significant differences between resistance rates of bft positive and negative strains (P > 0.05; 0.12 and 0.28, respectively).

Surveillance of Haemophilus influenzae among respiratory tract samples of Turkish children.

We conducted three prospective studies of Haemophilus influenzae in different groups of children. Pharyngeal swab samples were taken (i). from 1382 healthy infants and children between 0 and 10 years of age (group 1), attending well child clinics (n=438), day care centres (n=440) and elementary schools (n=504), and (ii). from 322 children aged 2-10 years (group 2), clinically diagnosed as having upper respiratory tract infection. Pharyngeal swab samples and sinus aspirates were obtained from 49 children between 2 and 9 years of age (group 3), clinically diagnosed as having sinusitis. H. influenzae was isolated in similar rates from 315 (22.7%) of children in group 1, 72 (22.3%) of children in group 2 and 12 (24.4%) of children in group 3. Serotype b comprised 7, 5.2 and 2% of all H. influenzae isolates for group 1, 2 and 3, respectively. Production of beta-lactamase was detected in 1.0% of H. influenzae type b isolates in group 1, 1.2 and 6.1% of all isolates in group 2 and 3, respectively. There were no beta-lactamase negative ampicillin-resistant strains.

[The epidemiology of nasopharyngeal colonisation of Streptococcus pneumoniae in children with respiratory tract infection]. / Solunum yolu enfeksiyonu olan çocuklarda nazofarenksde Streptococcus pneumoniae kolonizasyon epidemiyolojisi.

Nasopharyngeal swab specimens from 324 children with respiratory tract infections were evaluated to detect the rate of Streptococcus pneumoniae colonisation. S. pneumoniae was detected in 92 (28%) of the subjects. Forty three (46.7%) of the isolates were serotyped by the capsular swelling tests. The most common serotypes were 19F, 6B, 3 and 23F. The 7, 9 and 11 valent conjugate pneumococcal vaccines covered 35.8%, 40% and 46.7% of all the S. pneumoniae isolates, respectively. Thirty two (34.8%) isolates exhibited penicillin MIC values between 0.1 and 1 microg/ml, only 1 isolate had MIC > or = 2 microg/ml. Penicillin resistant pneumococcal colonisation was most frequently detected in children with viral upper respiratory tract infections (12.5%). Resistance rates of trimetoprim-sulfamethoxazole, erythromycin, chloramphenicol, clindamycin, ceftriaxone, rifampin were 31.5%, 9.8%, 6.5%, 4.3%, 1%, 0%, respectively. Being a children of a family with low income was the only risk factor for colonisation with S. pneumoniae, whereas having a sibling attending to a day care center, antibiotic use in the last three months and use of more than one antibiotic were significant risk factors for colonisation with penicillin resistant S. pneumoniae (p < 0.05).

Panton-Valentine leukocidin and biofilm production of Staphylococcus aureus isolated from respiratory tract.

INTRODUCTION: Staphylococcus aureus is one of the first bacteria colonizing in cystic fibrosis (CF) respiratory tract and different virulence factors are responsible for disease progression. It is not clear if CF S. aureus strains are more virulent than strains isolated from non-CF patients. METHODOLOGY: Biofilm production was detected by a modified tissue culture plate method, presence of genes encoding for Panton-Valentine leukocidin (PVL) was investigated by a signal amplified sandwich hybridization assay and antimicrobial susceptibility patterns were detected by disk diffusion method. RESULTS: Staphylococcus aureus clinical isolates (n = 88) recovered from respiratory tract specimens in which 31 of them were from cystic fibrosis (CF) patients were analysed. Biofilm production was detected in 96.8% of CF isolates in which 32.3% exhibited strong positive phenotype and in 47.4% of non-CF isolates in which strong positive phenotype was not observed (p <0.05). All CF isolates were methicillin susceptible, whereas 53.4% of non-CF isolates (n = 31) were methicillin resistant. No resistance was observed for vancomycin, chloramphenicol and trimethoprim/sulfamethoxazole in any of the isolates. PVL genes were detected only in two isolates (2.3%), one from each group, CF and non-CF, which both were methicillin susceptible. CONCLUSION: Biofilm rather than PVL production appears to be an important virulence factor in CF patients.

Quorum sensing and virulence of Pseudomonas aeruginosa during urinary tract infections.

INTRODUCTION: In the opportunistic pathogen Pseudomonas aeruginosa, the production of several virulence factors depends on quorum sensing (QS) involving N-acylhomoserine lactone signal molecules. In vitro studies have suggested that the QS system is crucial in the pathogenesis of P. aeruginosa. However, it is unclear whether QS systems of P. aeruginosa play the same role during infections. METHODOLOGY: In this study, to explore the contribution of QS systems to the pathogenesis of P. aeruginosa during urinary tract infections, we collected 82 clinical isolates. Detection of N-acyl-homoserine lactones (C12-HSL and C4-HSL) was performed on agar plates employing biosensor strains C. violaceum. Elastase and biofilm production were determined spectrophotometrically. QS genes were detected by PCR and subsequently underwent sequencing. RESULTS AND CONCLUSION: Six isolates were found to be negative in the production of both C12-HSL and C4-HSL and all virulence factors tested.  PCR analysis of these isolates revealed that four isolates contained all four QS genes while one isolate was negative for lasR gene, and one isolate negative for lasI, lasR and rhlR genes. Sequence analyses of these isolates showed that the lasR, lasI, rhlR and rhlI genes had point mutations. The combination of these mutations probably explains their C12-HSL, C4-HSL and virulence factor deficiencies. Results of this study suggest that QS deficient clinical isolates occur and are still capable of causing clinical infections in humans.