- Volume 71, Issue 7, 2022
Volume 71, Issue 7, 2022
- Antimicrobial Resistance
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Simultaneously screening for methicillin-resistant Staphylococcus aureus and its susceptibility to potentiated penicillins
Introduction. We recently revealed that a significant proportion of clinical methicillin-resistant Staphylococcus aureus (MRSA) isolates are susceptible to pencillins and clavulanic acid (potentiated penicillins), including widely available combinations such as co-amoxiclav. These isolates also showed increased susceptibility to oxacillin on Iso-Sensitest Agar (ISA).
Hypothesis/Gap Statement. The increased susceptibility to oxacillin displayed on ISA by these MRSA isolates may be used to distinguish them from the resistant ones.
Aim. We aimed to develop a method to simultaneously screen a S. aureus clinical isolate for its susceptibility to methicillin and potentiated penicillins.
Methodology. A double-disc diffusion method using 10 µg cefoxitin and 1 µg oxacillin discs on ISA was developed and tested against a panel of 120 whole genome-sequenced MRSA isolates. The sensitivity of the method was compared with that of previously published genotypic and phenotypic methods. In addition, double-disc diffusion was performed for all isolates on Müller–Hinton agar (MHA) following the European Committee on Antimicrobial Susceptibility Testing (EUCAST) protocol.
Results. All isolates (120/120) were reconfirmed to be phenotypically MRSA, as indicated by the result of cefoxitin disc diffusion testing. All isolates (40/40) that had a pencillins and clavulanic acid (Pen–Clav)-resistant genotype were not inhibited by oxacillin, while 77/80 (96.3 %) isolates that had a Pen–Clav-susceptible genotype were inhibited by oxacillin on ISA. The results also showed that the EUCAST method using MHA correctly identified all isolates as MRSA but failed to distinguish the Pen–Clav-susceptible isolates from the Pen–Clav-resistant isolates.
Conclusions. This double-disc diffusion method using ISA could be used to accurately screen for clinical MRSA isolates and determine their susceptibility to Pen–Clav simultaneously, rapidly identifying MRSA infections that might be suitable for treatment with potentiated penicillins.
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- Clinical Microbiology
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Elucidating the virulence genes harboured by carbapenemase- and non-carbapenemase-producing carbapenem-resistant Klebsiella pneumoniae rectal isolates from patients admitted to intensive care units using whole-genome sequencing in Kuwait
More LessIntroduction. Klebsiella pneumoniae is a Gram-negative pathogen responsible for community- and nosocomial-acquired infections. The presence of an accessory genome determines the bacterial pathogenicity and the host immune response, and thus indicates multidrug-resistant strains or more virulent groups. Little is known about the virulence genes in K. pneumoniae in Kuwait.
Hypothesis/Gap Statement. The diversity of virulence genes and capsule loci in K. pneumoniae isolates warrants further genomic studies to better understand their transmission within the hospitals in Kuwait.
Aim. We aimed to investigate the virulence genes harboured by K. pneumoniae isolated from rectal swabs of intensive care unit (ICU) patients in two Kuwaiti teaching hospitals.
Methodology. Six isolates from patients in the ICUs of Al Razi and Mubarak hospitals, designated RZH144, RZH132 RZH108 and RZH173, and MKH381 and MKH347, respectively, were subjected to whole-genome sequencing (WGS) assays. RZH144 and RZH132 were non-carbapenemase-producing K. pneumoniae (NCKP) isolates negative for genes encoding carbapenemase production by PCR assays, and the remaining four were carbapenemase-producing K. pneumoniae (CPKP) isolates. Isolates were characterized by phenotypic, PCR and WGS methods. Susceptibility testing was performed by E test and clonality by multilocus sequence typing. Analysis of the isolates’ assembled contigs was carried out using Kleborate (https://pathogen.watch).
Results. An NCPE RZH132 K. pneumoniae isolate belonged to ST231-wzi104 and harboured gene clusters encoding the biosynthesis of the siderophore aerobactin (iuc5) on 62-3LV. The capsular locus variants were KL51 and O locus O1v2. Another NCPKP RZH144 isolate was confirmed as ST43-wzi412 and harboured KL61 and O1v1. The four CPKP isolates harboured two virulence loci – ybt14 and iuc5 – encoding the siderophores yersiniabactin and aerobactin, respectively. They belonged to ST231-wzi104 and harboured yersiniabactin on ICEKp5. The sequence type of ybt was YbST145-1LV. Strain RZ108 was devoid of virulence loci. Its sequence type was ST15-wzi151 and harboured KL48 and O1V1. ST231 clonal lineage isolates shared common virulence plasmid variants.
Conclusion. The CPKP ST231 had the highest virulence score and contained iuc5, which was found for the first time in ST231-CPKP isolates in Kuwait.
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- Disease, Diagnosis and Diagnostics
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Bacterial contamination of non-contact condensing lenses in National University of Malaysia Hospital isolated using BD BACTEC Peds Plus/F broth bottles versus conventional culture plates
Introduction. Non-contact condensing lenses (NCLL) are a requirement in ophthalmology examinations. To date, there have been no studies on the types of bacteria found on handheld lenses used to examine patients in an ophthalmology clinic.
Hypothesis. The BD BACTEC Peds Plus broth (BACTEC-PP) culture method can isolate more organisms as compared to conventional culture plates (CCP) from NCLL.
Aim. To evaluate the organism spectrum cultured from NCCL for fundus examination and to compare the results between BACTEC-PP and CCP. The isolation results were then related to the participant’s knowledge and hand hygiene practices (HHP).
Methodology. This is a comparative cross-sectional study involving consenting trainee ophthalmologists from a single centre, whose preferred NCCL was swabbed from January to December 2019. The respondents completed the adapted World Health Organization Hand Hygiene Knowledge and Perception Questionnaire, and their HHP were observed by Infective Control Unit nurses. Positive bacterial growth using both methods, in addition to hand hygiene practices, were compared.
Results. All samples had positive yields by at least one method. BACTEC-PP had a higher yield of 47 (90.4%) isolates compared to CCP with 37 (71.2%) isolates, P=0.041. CoNS sp (38.9 %) was the most common isolate with both methods, followed by Bacillus sp (25.3 %). At the same time, three fungi were detected with CCP only (3.2 %). There was a significant correlation in bacterial isolation with years of training, with fewer isolates among seniors in both BACTEC-PP (P=0.049) and CCP (P=0.034). There were no significant correlations between HHP and positive yields from either culture method.
Conclusions. NCCL used by trainee ophthalmologists are typically contaminated by at least one bacteria, with CoNS sp being the most commonly isolated. More positive cultures occurred in lenses from junior trainees. Contamination was not correlated with knowledge or HHP. BACTEC-PP has significantly higher yields than CCP for bacterial isolation from NCCL, but did not isolate any fungus.
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- Medical Mycology
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Introducing biomarkers for invasive fungal disease in haemato-oncology patients: a single-centre experience
Hypothesis/Gap Statement. The impacts of increased biomarker testing on antifungal prescribing have not yet been fully examined in a real-life setting.
Objectives. Biomarkers for invasive fungal disease (IFD) have been shown to reduce antifungal prescriptions in neutropaenic haemato-oncology patients. Our study aimed to assess the real-life impacts of introducing a novel biomarker-based pathway, incorporating serum galactomannan and Aspergillus PCR, for pyrexial haemato-oncology admissions.
Methods. Patients with neutropaenic fever were identified prospectively after introduction of the new pathway from 2013–2015. A historical group of neutropaenic patients who had blood cultures taken from 2009–2012 was generated for comparison. Clinical details, including demographics, underlying diagnosis, investigations, radiology and antimicrobial treatment were obtained.
Results. Prospective data from 308 patients were compared to retrospective data from 302 patients. The proportion of patients prescribed an antifungal medication was unchanged by the pathway (P=0.79), but the pattern was different, with more patients receiving targeted antifungals (P=0.04). A negative serum galactomannan test was not sufficient evidence to withhold therapy, with 17.2% of these episodes felt to have possible or probable IFD using the European Organization for Research and Treatment of Cancer/Invasive Fungal Infections Cooperative Group and the National Institute of Allergy and Infectious Diseases Mycoses Study Group (EORTC/MSG) criteria. There was no difference in 30-day mortality (P=0.21) or 1-year mortality (P=0.57) following introduction of the pathway.
Conclusions. Biomarkers can be used safely as part of a multidisciplinary approach to the diagnosis of IFD in neutropaenic haemato-oncology patients. Whilst they do not necessarily result in antifungal therapy being withheld, they can allow more confident diagnosis of IFD and more specific antifungal therapy in selected cases.
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- Corrigenda
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Volumes and issues
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Volume 73 (2024)
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Volume 72 (2023 - 2024)
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Volume 71 (2022)
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Volume 70 (2021)
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Volume 69 (2020)
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Volume 68 (2019)
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Volume 67 (2018)
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Volume 66 (2017)
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Volume 65 (2016)
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Volume 64 (2015)
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Volume 63 (2014)
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Volume 62 (2013)
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Volume 61 (2012)
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Volume 60 (2011)
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Volume 59 (2010)
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Volume 58 (2009)
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Volume 57 (2008)
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Volume 56 (2007)
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Volume 55 (2006)
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Volume 54 (2005)
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Volume 53 (2004)
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Volume 52 (2003)
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Volume 51 (2002)
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Volume 50 (2001)
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Volume 49 (2000)
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Volume 48 (1999)
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Volume 47 (1998)
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Volume 46 (1997)
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Volume 45 (1996)
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Volume 44 (1996)
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Volume 43 (1995)
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Volume 42 (1995)
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Volume 41 (1994)
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Volume 40 (1994)
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Volume 39 (1993)
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Volume 38 (1993)
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Volume 37 (1992)
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Volume 36 (1992)
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Volume 35 (1991)
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Volume 34 (1991)
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Volume 33 (1990)
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Volume 32 (1990)
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Volume 31 (1990)
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Volume 30 (1989)
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Volume 29 (1989)
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Volume 28 (1989)
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Volume 27 (1988)
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Volume 26 (1988)
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Volume 25 (1988)
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Volume 24 (1987)
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Volume 23 (1987)
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Volume 22 (1986)
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Volume 21 (1986)
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Volume 20 (1985)
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Volume 19 (1985)
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Volume 18 (1984)
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Volume 17 (1984)
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Volume 16 (1983)
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Volume 15 (1982)
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Volume 14 (1981)
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Volume 13 (1980)
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Volume 12 (1979)
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Volume 11 (1978)
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Volume 10 (1977)
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Volume 9 (1976)
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Volume 8 (1975)
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Volume 7 (1974)
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Volume 6 (1973)
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Volume 5 (1972)
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Volume 4 (1971)
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Volume 3 (1970)
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Volume 2 (1969)
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Volume 1 (1968)