Pooled Specimen Testing Using Automated Cartridge-Based System for COVID-19: The Cost on Sensitivity.

BACKGROUND: Pooled specimen screening for the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can improve laboratory testing capacity. This study assessed the impact of pooling and retesting individual swabs on the overall detection rate and reduction in the frequency of retesting. METHODS: One hundred respiratory swabs specimens were tested individually and in pools of three or five samples using the Cepheid's Xpert® Xpress SARS-CoV-2 test kit. The optimum number of samples per pool was calculated using the application 'A Shiny App for Pooled Testing'. RESULTS: Twenty-five pools were generated from 101 samples. Out of 13 pools that contained five samples each, three pools gave true positive results. While out of the 12 pools that contained three samples each, five pools gave true positive results. Four samples gave a false negative pool result. The overall sensitivity and specificity of the assay in the pools were 66.6% and 100%, respectively. The cycle threshold was reduced in most of the pools compared to individual sample tests. CONCLUSION: The overall pooled test had a remarkable impact on laboratory resources. Yet, caution is warranted when selecting the cases for pooled testing, since the reduction in sensitivity can significantly impact and increase the risk of exposure to infection.

Molecular Surveillance of Multidrug-Resistant Acinetobacter baumannii.

Acinetobacter baumannii, a bacterial strain which demonstrates an elevated wide range multidrug resistance to commonly prescribed antibiotics, has been linked to recent major global outbreaks, raising a major clinical concern. Its reduced antibiotic susceptibility is closely related to the acquisition of a potent carbapenemase and/or intrinsic gene "over expression" through insertion sequences. Hence, this study aimed at investigating the antimicrobial susceptibility and molecular mechanisms underlying ß-lactam resistance in A. baumannii, isolated at an academic medical centre. To understand the basis of resistance, 103 multidrug-resistant (MDR) A. baumannii isolates were collected, their antibiotic susceptibility was tested phenotypically, and then molecular analyses were performed, by testing a range of commonly encountered carbapenemases-OXA-51, OXA-23, NDM, VIM, and KPC. All strains demonstrated pan-resistance to most of the advanced antibiotics tested, including piperacillin/tazobactam, ceftazidime, cefepime, and ciprofloxacin. Moreover, majority of isolates exhibited resistance to imipenem (98.1%) and trimethoprim (90.3%). Approximately 50% of the strains showed meropenem, amikacin, and gentamycin resistance; however, lower resistance rate to tigecycline (4.9%) was noted. Moreover, isolates contained potent carbapenemases such as the intrinsic OXA-51 (89.3%), as well as the acquired resistant genes OXA-23 (68.9%), NDM (84.5%), and VIM (88.3%). The insertion sequence element ISAba1 was only detected in 35.9% of the strains. Potent resistant genes known to be carried on mobile genetic elements that aid the spread of highly resistant phenotypes were observed in a majority of isolates. These findings enforce the need for vigilant infection control measures and continuous surveillance.

Diagnosis of group A streptococcal pharyngitis in the paediatric emergency department using a fluorescence-based RADT: predicted impact on antibiotic prescription.

Introduction. Using rapid antigen diagnostic tests (RADTs) in clinical practice has shown excellent specificity but often has diminished sensitivity.Gap Statement. Local data for evaluating the diagnostic performance of a new fluorescence-based RADT and its influence on the antibiotic prescription rate are not available.Aim. To evaluate the accuracy of fluorescent immunoassay (FIA)-RADTs for diagnosing group A streptococcal (GAS) pharyngitis among children and its estimated effect as a point of care test (POCT) on the antibiotic prescription rate at the paediatric emergency department.Methodology. A prospective study was conducted, comprising children 3 to 14 years old presenting with pharyngitis. Throat swab culture and FIA-RADTs were performed on all samples. Conventional PCR was performed on the discordant samples.Results. A total of 246 children were included in this study. The sensitivity, specificity, and positive and negative predictive values of the FIA-RADT, based on culture results and PCR detection combined, were 95.6, 96.8, 94.6 and 97.4 %, respectively. Antibiotics have been prescribed to 162 (65.9 %) children; however, if FIA-RADTs had been added in the clinical practice as a POCT, only 92 (37.4 %) children would have received antibiotics in total. Additionally, implementation of FIA-RADTs would significantly reduce the antibiotic prescription rate from 48.8 and 60.6 % to 9.5 and 31.9 % among patients with clinical scores of 2 and 3, respectively.Conclusion. The new FIA-RADT is simple, prompt and reliable. It is helpful in clinical settings and may be used to reduce antibiotic overprescription, especially for children who have a low risk for GAS pharyngitis, according to the clinical score.

Bacterial and Fungal Coinfection in Critically Ill COVID-19 Cases and Predictive Role of Procalcitonin During the First Wave at an Academic Health Center.

BACKGROUND: Coinfection at various sites can complicate the clinical course of coronavirus disease of 2019 (COVID-19) patients leading to worse prognosis and increased mortality. We aimed to investigate the occurrence of coinfection in critically ill COVID-19 cases, and the predictive role of routinely tested biomarkers on admission for mortality. METHODS: This is a retrospective study of all SARS-CoV-2-infected cases, who were admitted to King Fahad Hospital of the University between March 2020 and December 2020. We reviewed the data in the electronic charts in the healthcare information management system including initial presentation, clinical course, radiological and laboratory findings and reported all significant microbiological cultures that indicated antimicrobial therapy. The mortality data were reviewed for severely ill patients who were admitted to critical care units. RESULTS: Of 1091 admitted patients, there were 70 fatalities (6.4%). 182 COVID-19 persons were admitted to the critical care service, of whom 114 patients (62.6%) survived. The in-hospital mortality was 13.4%. Coinfection was noted in 67/68 non-survivors, and Gram-negative pathogens (Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter baumanni) represented more than 50% of the etiological agents. We noted that the serum procalcitonin on admission was higher for non-survivors (Median = 1.6 ng/mL ± 4.7) than in survivors (Median = 0.2 ng/mL ± 4.2) (p ≤ 0.05). CONCLUSION: Coinfection is a serious complication for COVID-19 especially in the presence of co-morbidities. High levels of procalcitonin on admission may predict non-survival in critically ill cases in whom bacterial or fungal co-infection is likely.

Low levels of soluble DPP4 among Saudis may have constituted a risk factor for MERS endemicity.

Most of the cases of Middle East respiratory syndrome coronavirus (MERS-CoV) were reported in Saudi Arabia. Dipeptidyl peptidase-4 (DPP4) was identified as the receptor for the virus. The level of soluble DPP4 (sDPP4) was found to be reduced in MERS-CoV infected patients while high levels of sDPP4 were suggested to be protective against MERS-CoV in animal models. We investigated whether the Saudi population has lower levels of sDPP4 which makes them more susceptible to MERS-CoV infection and, therefore, could explain the larger number of cases from the country. Blood samples were collected from 219 Saudi blood donors and 200 blood donors from other ethnic groups. The plasma level of sDPP4 was measured by ELISA and the following SNPs in the DPP4 gene; rs35128070, rs1861978, rs79700168, and rs17574, were genotyped by TaqMan SNP genotyping assay. The average level of plasma sDDP4 was significantly lower in Saudis than other Arabs and non-Arabs (P value 0.0003 and 0.012, respectively). The genotypes AG of rs35128070 and GT of rs1861978 were significantly associated with lower sDPP4 among Saudis (P value 0.002 for each). While both genotypes AA and AG of rs79700168 and rs17574 were associated with significantly lower average sDPP4 level in Saudis compared to other ethnic groups (P value 0.031 and 0.032, and 0.027 and 0.014, respectively). Herein, we report that the Saudi population has lower levels of plasma sDPP4 than other ethnic groups, which is associated with genetic variants in the DPP4 gene. This may have contributed to increase the susceptibility of the Saudi population to MERS-CoV infection and could be a factor in the long-lasting persistence of the virus in the country.

A seven-year surveillance of Candida bloodstream infection at a university hospital in KSA.

OBJECTIVES: Candidemia incidence has increased in the past few years, with high mortality. Previous studies have reported a variable distribution of Candida spp. among different regions. This study aimed to identify the species found in Candida bloodstream infections, routine antifungal susceptibility testing, and mortality outcomes in an academic medical centre. METHODS: Between January 2012 and December 2018, the positive blood cultures for candidemia infection were retrieved and statistically analysed for species prevalence, susceptibility pattern, and crude mortality at 14, 30, 60 and 90 days. RESULTS: Of 156 candidemia cases, a majority (69.2%) was caused by non-albicans Candida spp. After Candida albicans (30.8%), Candida tropicalis and Candida parapsilosis were the second and third most frequeunt isolates spp, each counting for 23.7%. Acquired resistance was detected in 14.8% of candidemia strains. No other antifungal resistance was detected. The overall crude mortality rates of all species were 29.3%, 47.9%, 56.4%, and 58.0% at 14, 30, 60, and 90 days, respectively. A higher mortality rate was noted in cases of Candida krusei infection (crude mortality 71.4-100%, p = 0.002). CONCLUSION: In this study, a considerable shift to non-albicans Candida causing most bloodstream infections was observed. As such infections pose a serious threat to hospitalised patients, microbiology laboratories are urged to adopt rapid diagnostic and minimal inhibitory concentration-based testing for the detection of susceptible dose-dependent phenotypes. Prospective studies are essential to consider the prognosis of bloodstream infections by various Candida species in a multivariate model.

The diagnostic impact of implementing a molecular-based algorithm to standard mycobacterial screening at a reference laboratory with an intermediate prevalence for non-respiratory samples.

Rapid, reliable results can be given by molecular, direct detection and identification of the Mycobacterium tuberculosis (MTB/Mtb) complex from clinical samples. The Xpert MTB/RIF assay is an assay that has been availablefor more than a decade for identification of Mycobacterium tuberculosis and resistance to rifampicin. However, there is minimal evidence on its clinical usefulness in paucibacillary, non-respiratory samples. The Xpert MTB/RIF assay clinical utility index, its diagnostic characteristics and the number required to diagnose 2935 non-respiratory specimens submitted for routine mycobacterial work-up in a reference laboratory in an intermediate prevalence setting per specimen form were evaluated. The Xpert MTB/RIF assay showed a variable clinical utility index and number required to diagnose (NND) depending on the type of specimen, which was moderate in tissue biopsies (NND = 1.8) and excellent in pus and urine samples, compared to acid-fast microscopy and culture as a gold standard technique (NND = 1.1 and 1.2). Microscopy, on the other hand, consistently showed a weak to fair index of clinical usefulness in all specimen forms, with in NND of 2.3-12.5. The NND for detecting tuberculous infection in the cerebrospinal fluid by the Xpert MTB/RIF assay was noted to be 1.2, with a moderate clinical utility index of 0.8. The evidence presented indicates that the overall appropriate diagnostic utility of the Xpert MTB/RIF assay is clinically successful in most non-respiratory samples. To check the cost-effectiveness and prognostic effect of integrating this completely automated molecular-based assay into the routine testing algorithm for non-respiratory mycobacterial specimens, further data must be collected.

Antimicrobial activity of cephalosporin-beta-lactamase inhibitor combinations against drug-susceptible and drug-resistant Pseudomonas aeruginosa strains.

OBJECTIVES: We conducted this study to test the susceptibility of P. aeruginosa to the routinely used drugs and to the two recently available antimicrobial agents, ceftazidime-avibactam and ceftolozane-tazobactam. METHODS: We isolated the non-replicate strains of P. aeruginosa from inpatients between December 2018 and April 2019. The VITEK® MS system was used for phenotypic identification and VITEK 2 for initial antimicrobial susceptibility testing. We supplemented these tests with determination of the minimum inhibitory concentration (MIC) of four antimicrobials; imipenem, meropenem, ceftazidime-avibactam and ceftolozane-tazobactam. The standards of the Clinical and Laboratory Standards Institute were followed. RESULTS: A total of 67 strains of P. aeruginosa, including 38 multidrug-resistant strains, were obtained from various specimens. Susceptibility to various tested aminoglycosides and fluoroquinolones was maintained in 49.3-56.7% and 40.0-43.3% of the total isolates. Amongst ß-lactams, the strains were susceptible to the following agents in an ascending order: ceftazidime (32.8%), cefepime (37.3%), imipenem (36.0%), piperacillin-tazobactam (39.0%), meropenem (44.8%), ceftazidime-avibactam (61.2%) and ceftolozane-tazobactam (62.7%). The susceptibility rates of the multidrug-resistant strains to both ceftazidime-avibactam and ceftolozane-tazobactam were less than 35%. High levels of resistance to the new agents (MIC > 256 ug/ml) were detected in 21 and 22 isolates. CONCLUSION: Our study shows limitation in the empirical use of ceftazidime-avibactam and ceftolozane-tazobactam as therapeutics in serious infections. Moreover, our data highlights the need for prompt antimicrobial susceptibility testing to guide their clinical usage.

Biofilm-Formation in Clonally Unrelated Multidrug-Resistant Acinetobacter baumannii Isolates.

This study analyzed the genotype, antibiotic resistance, and biofilm formation of Acinetobacter baumannii strains and assessed the correlation between biofilm formation, antibiotic resistance, and biofilm-related risk factors. A total of 207 non-replicate multi-drug-resistant A. baumannii strains were prospectively isolated. Phenotypic identification and antimicrobial susceptibility testing were carried out. Isolate biofilm formation ability was evaluated using the tissue culture plate (TCP), Congo red agar, and tube methods. Clonal relatedness between the strains was assessed by enterobacterial repetitive intergenic consensus-PCR genotyping. Of the 207 isolates, 52.5% originated from an intensive care unit setting, and pan resistance was observed against ceftazidime and cefepime, with elevated resistance (99-94%) to piperacillin/tazobactam, imipenem, levofloxacin, and ciprofloxacin. alongside high susceptibility to tigecycline (97.8%). The Tissue culture plate, Tube method, and Congo red agar methods revealed that 53.6%, 20.8%, and 2.7% of the strains were strong biofilm producers, respectively, while a significant correlation was observed between biofilm formation and device-originating respiratory isolates (p = 0.0009) and between biofilm formation in colonized vs. true infection isolates (p = 0.0001). No correlation was detected between antibiotic resistance and biofilm formation capacity, and the majority of isolates were clonally unrelated. These findings highlight the urgent need for implementing strict infection control measures in clinical settings.

Phenotypic and molecular study of pneumococci causing respiratory tract infections. A 3-year prospective cohort.

OBJECTIVES: To study serotype distribution and antimicrobial resistance to beta-lactams and macrolides in pneumococci causing respiratory diseases after the introduction of the 13-valent pneumococcal conjugate vaccine in Saudi Arabia. Methods: This is a hospital-based and a cross-sectional prospective surveillance study conducted at King Fahad Hospital of the University, AlKhobar, Kingdom  of Saudi Arabia, in which respiratory pneumococcal isolates collected between 2012 and 2014 were serotyped by multiplex sequential polymerase chain reaction (PCR) and Pneumotest-Latex. Resistance genes to beta-lactams and macrolides were detected by multiplex PCR. Results: The most common serotypes encountered were 11A, 19A, 17F, 23F, 3, and 19F, representing 64% of the typeable strains. Interestingly, 24% of the 94 isolates were not typeable and 18% were negative for the housekeeping gene cpsA. Among the 53 typeable pneumococci isolates, 36 (67.9%) carried genes encoding resistance to both penicillin and macrolides, 9 (17%) were penicillin-monoresistant, 3 (5.6%) were macrolide-monoresistant, and 5 (9.4%) were designated non-resistant. The high rate of resistance genes did not significantly differ according to serotype (p=0.76). Similarly, non-typeable pneumococci (cpsA+ and cpsA-) had high rates of resistance to both penicillin (62.5%) and macrolides (47%). Conclusion: These data highlight the emergence of a previously rare capsular type, 11A (mean patient age, 29 years; p=0.001). Moreover, the high percentage of non-typeable isolates shows the emergence of possible atypical pneumococcal serotypes not covered by available vaccines.

Sensitivity and specificity of subgingival bacteria in predicting preterm birth- a pilot cohort study.

OBJECTIVE: Preterm birth (PTB) increases the risk of adverse outcomes for new born infants. Subgingival bacteria are implicated in causing PTB. The aim of the present study was to assess the accuracy of some subgingival gram positive and gram negative bacteria detected by routine lab procedures in predicting PTB. METHODOLOGY: Pregnant Saudi women (n= 170) visiting King Fahad hospital, Dammam, Saudi Arabia, were included in a pilot cohort study. Plaque was collected in the 2nd trimester and screened for subgingival anaerobes using Vitek2. Pregnancy outcome (preterm/full term birth) was assessed at delivery. Sensitivity, specificity and positive and negative likelihood ratios were calculated for the identified bacteria to predict PTB. RESULTS: Data about time of delivery was available for 94 subjects and 22 (23.4%) had PTB. Three gram negative and 4 gram positive subgingival bacteria had sensitivity ≥ 95% with two of each having negative likelihood ratios ≤0.10. Three gram positive bacteria had specificity > 95% with only one having positive likelihood ratio >2. CONCLUSION: Subgingival bacteria identified using readily available lab techniques in the plaque of pregnant Saudi women in their 2nd trimester have useful potential to rule out PTB.

Dormancy models for Mycobacterium tuberculosis: A minireview.

Dormancy models for Mycobacterium tuberculosis play important roles in understanding various aspects of tuberculosis pathogenesis and in the testing of novel therapeutic regimens. By simulating the latent tuberculosis infection, in which the bacteria exist in a non-replicative state, the models demonstrate reduced susceptibility to antimycobacterial agents. This minireview outlines the models available for simulating latent tuberculosis both in vitro and in several animal species. Additionally, this minireview discusses the advantages and disadvantages of these models for investigating the bacterial subpopulations and susceptibilities to sterilization by various antituberculosis drugs.

A case of bacteremia caused by Campylobacter fetus: an unusual presentation in an infant.

Bacteremia due to Campylobacter spp. is rarely reported, and Campylobacter fetus is the species most commonly exhibiting vascular tropism, as occurred in this case report describing the diagnosis of C. fetus bacteremia in an infant presenting with respiratory tract infection. A 5-month-old baby, with undiagnosed failure to thrive, presented to the acute care service with a high fever and respiratory symptoms of 2 days duration. The initial clinical and laboratory diagnosis suggested bacteremia, but there was difficulty with recovery and identification of the organism from blood. Subsequent laboratory testing confirmed C. fetus as the etiological agent. Campylobacter isolated from blood culture bottles may give atypical laboratory features, rendering its identification challenging. Thus, such an infrequent species might be underestimated in frequency, and it should be considered in diagnostic laboratories, when a gram-negative organism with atypical findings is encountered in respiratory samples or blood culture bottles.

Dormancy models for Mycobacterium tuberculosis: A minireview

Dormancy models for Mycobacterium tuberculosis play important roles in understanding various aspects of tuberculosis pathogenesis and in the testing of novel therapeutic regimens. By simulating the latent tuberculosis infection, in which the bacteria exist in a non-replicative state, the models demonstrate reduced susceptibility to antimycobacterial agents. This minireview outlines the models available for simulating latent tuberculosis both in vitro and in several animal species. Additionally, this minireview discusses the advantages and disadvantages of these models for investigating the bacterial subpopulations and susceptibilities to sterilization by various antituberculosis drugs.