Enhancing sensitivity of qPCR assays targeting Streptococcus pneumoniae, Neisseria meningitidis and Haemophilus influenzae by using a mutant Taq DNA polymerase.

AIMS: Streptococcus pneumoniae, Neisseria meningitidis and Haemophilus influenzae are important causes of bacterial meningitis. In this study, the DNA binding site of the wild type Taq DNA polymerase was modified to produce a mutant enzyme with enhanced DNA affinity and PCR performance. The engineered and the wild type enzymes were integrated into qPCR-based assays for molecular detection of S. pneumoniae, N. meningitidis, H. influenzae, and serogroups and serotypes of these three pathogens. METHODS: Bio-Speedy® Bacterial DNA Isolation Kit (Bioeksen R&D Technologies, Turkiye) and 2× qPCR-Mix for hydrolysis probes (Bioeksen R&D Technologies, Turkiye) and CFX96 Instrument (Biorad Inc., USA) were used for all molecular analyses. Spiked negative clinical specimens were tested using the developed qPCR assays and the culture-based conventional methods for the analytical performance evaluation. RESULTS: All qPCR assays did not produce any positive results for the samples spiked with potential cross-reacting bacteria. Limit of detection (LOD) of the assays containing the mutant enzyme was 1 genome/reaction (10 cfu/mL sample) which is at least 3 times lower than the previously reported LOD levels for DNA amplification based molecular assays. LODs for the spiked serum and cerebrospinal fluid (CSF) samples decreased 2.3-4.7 and 1.2-3.5 times respectively when the mutant enzyme was used instead of the wild type Taq DNA polymerase. CONCLUSIONS: It is possible to enhance analytical sensitivity of qPCR assays targeting the bacterial agents of meningitis by using an engineered Taq DNA polymerase. These qPCR-based assays can be used for direct detection and serogrouping / serotyping of S. pneumoniae, N. meningitidis and H. influenzae at concentrations close to the lower limit of medical decision point.

[Meningococcemia: Different Serotypes in the Same Region]. / Meningokoksemi: Ayni Cografyada Farkli Serotipler.

Meningococcal infections are important health problems causing high morbidity and mortality. Neisseria meningitidis have 13 serogroups. A, B, C, Y and W135 are the most common causes of invasive disease among those serogroups. The distribution of the serogroups differs according to the geographical regions and the age groups. In this case report, two cases of meningococcemia infected with serogroup C and Y of N.meningitidis rarely seen in our country were presented. First case was a two and a half year-old female patient who has admitted to our pediatric emergency unit with fever and rash spreading from lower extremities to her body. The patient had diffuse purpuric rash with generalized weakness and tendency to sleep at admission. The patient has been suspected as meningococcemia because of the skin rash, tendency to sleep and hypotension. Antibiotics treatment was started immediately and lumber puncture was performed. In blood tests, leukocyte count: 3600/mm3 (61% neutrophils), hemoglobin: 11.1 g/ dl, platelet count: 127.000/mm3 , C-reactive protein: 10 mg/dl, erythrocyte sedimentation rate: 6 mm/ hour, prothrombin time: 28.8 seconds (normal value= 11-16), prothrombin activity: 36%, international normalized ratio (INR): 2.13 (normal value= 1-1.5), activated partial thromboplastin time: 57.7 seconds (normal value= 25-35 sec), fibrinogen: 246 mg/dl (normal value= 200-400 mg/dl) and in cerebrospinal fluid protein: 21 mg/dl and glucose: 62 mg/dl were found. There were eight cells in the microscopic examination. Skin rashes were increased and the patient became hypotensive. No microorganisms were isolated in blood and cerebrospinal cultures. N.meningitidis serogroup C was isolated from the cerebrospinal fluid of the patient using polymerase chain reaction (PCR). The patient suffered from immune-mediated arthritis in the sixth day of treatment and nonsteroidal anti-inflammatory drugs were given. The patient has recovered with antibiotics, fresh frozen plasma and inotropic treatment. Second case was a 13 year-old male patient who has admitted three days after the first case with a pre-diagnosis of malignancy because of pancytopenia and fever. The patient had generalized weakness and a few petechial purpuric rashes at the facial region at admission. After the admission general status of the patient has worsened rapidly and he has died as a result of cardiovascular arrest. Blood tests in admission showed leukocyte count: 6000/mm3 (79% neutrophils), hemoglobin: 17.3 mg/dl, platelet count: 16.000/mm3 , C-reactive protein: 8.63 mg/dl, prothrombin time: 92.6 seconds, prothrombin activity: 10%, INR: 6.78, activated partial thromboplastin time: 231.5 seconds. Cerebrospinal fluid obtained from postmortem lumbar puncture showed no growth (protein: 95 mg/dl, glucose: 35 mg/dl) and N.meningitidis serogroup Y was detected by PCR. Two meningococcemia cases caused by two different serogroups which are rarely seen in our region in recent years were presented at the same time period in the same hospital. This case report pointed out that surveillance has a great importance in such diseases.

The impact of meningococcal conjugate vaccine (MenACWY-TT) on meningococcal carriage in Hajj Pilgrims returning to Turkey.

Meningococcal conjugate vaccine was administered for the first time to pilgrims in 2018 in Turkey prior to their departure to the Hajj. This study aimed to determine the effect of vaccination on the prevalence of Neisseria meningitidis carriage among the pilgrims returning to Turkey. This prospective paired (departing and arriving) cohort study included pilgrims aged 10-80 years and compared N.meningitidis carriage before and after pilgrimage. Oropharyngeal samples were collected from 229 pilgrims before departing for Mecca, Kingdom of Saudi Arabia (KSA) and after their return to Turkey. Meningococcal carriage was detected in 3.9% (n = 9) at the time of departure; all positive samples were serogroup B. Upon returning to Turkey,1 (0.4%) pilgrim, who was not a carrier before pilgrimage, was positive for serogroup B. This study is the first to examine meningococcal carriage following the administration of conjugate vaccine to Hajj pilgrims from Turkey.