Haemophilus influenzae blood-stream infection and third-generation cephalosporin susceptibility testing: a comparative case study using EUCAST and CLSI guidelines.

Introduction: In this comparative case study, we discuss clinically relevant discrepancies of antimicrobial susceptibility testing (AST) interpretation for ceftriaxone against a non-typable, beta-lactamase negative, ampicillin-resistant (BLNAR) Haemophilus influenzae isolated from a blood culture. Case report: A 74-year-old man presented with a 3 day illness characterized by shortness of breath and dry cough, and was noted to be febrile and hypoxic on admission. A blood culture bottle flagged positive with Gram-negative coccobacilli, later identified as Haemophilus influenzae with the patient commenced on ceftriaxone. The isolate was beta-lactamase negative and antibiotic susceptibility testing (AST) using disc diffusion revealed the isolate resistant to ceftriaxone and ampicillin by EUCAST methodology, with the patient subsequently changed to amoxicillin/clavulanate. Further AST using the CLSI methodology in parallel demonstrated discrepant results between the two susceptibility methods. The patient recovered without complications. Conclusion: This discrepancy could lead to inconsistent reporting of susceptibilities between laboratories, and consequently antibiotic prescribing, especially for invasive isolates. As more laboratories adopt EUCAST methodologies for AST interpretation in Australia and globally, it is important for clinicians to consider the clinical implications of these methodological discrepancies.

Antibiotic Prescribing and Antimicrobial Resistance from an Australian Perspective.

In Australia, the overuse or inappropriate prescribing of antimicrobials in health (human and animal) and agriculture is a concern that has increased over the years. This has given bacteria, fungi, parasites, and some viruses through exposure more opportunity to develop resistance. A process of artificial and natural selection, which favors microorganisms in developing the strongest natural defenses increasing prevalence of antimicrobial resistance (AMR). Appropriate use of antimicrobials can be lifesaving to humans and animals, but inappropriate use needs to be closely monitored and acted on to promote improved safety and quality of care. Inappropriate use includes prescribing antimicrobials when they are not necessary, prescribing the wrong type of antimicrobial and prescribing them for the incorrect duration. This short report reviews and summarizes some of the efforts used in Australia to control AMR and antibiotic prescribing.

Evaluation of the influenza and respiratory syncytial virus (RSV) targets in the AusDiagnostics SARS-CoV-2, Influenza and RSV 8-well assay: sample pooling increases testing throughput.

During the COVID-19 pandemic, sample pooling has proven an effective strategy to overcome the limitations of reagent shortages and expand laboratory testing capacity. The inclusion of influenza and respiratory syncytial virus (RSV) in a multiplex tandem PCR platform with SARS-CoV-2 provides useful diagnostic and infection control information. This study aimed to evaluate the performance of the influenza and RSV targets in the AusDiagnostics SARS-CoV-2, Influenza and RSV 8-well assay, including the effect of pooling samples on target detection. RSV target detection in clinical samples was compared to the Cepheid Xpert Xpress Flu/RSV assay as a reference standard. Samples were then tested in pools of four and detection rates were compared. Owing to the unavailability of clinical samples for influenza, only the effect of sample pooling on simulated samples was evaluated for these targets. RSV was detected in neat clinical samples with a positive percent agreement (PPA) of 100% and negative percent agreement (NPA) of 99.5% compared to the reference standard, demonstrating 99.7% agreement. This study demonstrates that sample pooling by four increases the average Ct value by 2.24, 2.29, 2.20 and 1.91 cycles for the target's influenza A, influenza A typing, influenza B and RSV, respectively. The commercial AusDiagnostics SARS-CoV-2, Influenza and RSV 8-well assay was able to detect influenza and RSV at an intermediate concentration within the limit of detection of the assay. Further studies to explore the applicability of sample pooling at the lower limit of detection of the assay is needed. Nevertheless, sample pooling has shown to be a viable strategy to increase testing throughput and reduce reagent usage. In addition, the multiplexed platform targeting various respiratory viruses assists with public health and infection control responses, clinical care, and patient management.

Reusable venesection tourniquets: a potential source of hospital transmission of multiresistant organisms.

OBJECTIVE: To determine the prevalence of multiresistant organism (MRO) colonisation of reusable venesection tourniquets. DESIGN AND SETTING: A prospective study in a tertiary hospital to collect and analyse reusable venesection tourniquets for the presence of MROs - methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and extended-spectrum ß-lactamase and metallo-ß-lactamase-producing Enterobacteriaceae - using a sensitive enrichment method. Tourniquets were collected and tested during a 10-week period between September and November 2010. MAIN OUTCOME MEASURE: Prevalence of MRO colonisation of tourniquets. RESULTS: The overall colonisation rate of 100 tourniquets randomly collected from general wards, ambulatory care areas and critical care areas was 78%. MROs were isolated from 25 tourniquets collected from a variety of hospital locations, including general wards, the intensive care unit, burns unit and anaesthetic bay. MRSA was isolated from 14 tourniquets and VRE from 19; both MRSA and VRE were isolated from nine tourniquets. There were no microorganisms isolated from 22 tourniquets. CONCLUSION: Reusable tourniquets can be colonised with MROs and may be a potential source of transmission of MROs to hospitalised patients.

Isolation of clinically significant microorganisms from prosthetic joint tissue using BacT/ALERT paediatric blood culture bottles compared with solid culture media and enrichment broth.

The diagnosis of prosthetic joint infections and isolation of causative microorganisms has been found to be challenging in microbiology laboratories due to low sensitivity of microbiological culture. The aim of this study was to compare the use of conventional culture methods with the use of both enrichment broth and BacT/ALERT paediatric blood culture bottles, for the diagnosis of prosthetic joint infections. A total of 121 specimens from 44 patients were processed using three methods of microbiological culture: solid media, enrichment broth and paediatric bottles. The paediatric bottle method had a significantly lower (p<0.0001) time to detection than the standard solid media method, and was significantly more sensitive than solid media when used independently (93.33%, CI 83.27-98.09, vs 60.00%, CI 45.43-73.33). The combination use of solid media with paediatric bottles was found to be superior to the conventional solid media method and combination use with enrichment broth.

Clostridium difficile Toxins A and B: Insights into Pathogenic Properties and Extraintestinal Effects.

Clostridium difficile infection (CDI) has significant clinical impact especially on the elderly and/or immunocompromised patients. The pathogenicity of Clostridium difficile is mainly mediated by two exotoxins: toxin A (TcdA) and toxin B (TcdB). These toxins primarily disrupt the cytoskeletal structure and the tight junctions of target cells causing cell rounding and ultimately cell death. Detectable C. difficile toxemia is strongly associated with fulminant disease. However, besides the well-known intestinal damage, recent animal and in vitro studies have suggested a more far-reaching role for these toxins activity including cardiac, renal, and neurologic impairment. The creation of C. difficile strains with mutations in the genes encoding toxin A and B indicate that toxin B plays a major role in overall CDI pathogenesis. Novel insights, such as the role of a regulator protein (TcdE) on toxin production and binding interactions between albumin and C. difficile toxins, have recently been discovered and will be described. Our review focuses on the toxin-mediated pathogenic processes of CDI with an emphasis on recent studies.

Bacteriotherapy using fecal flora: toying with human motions.

The intestinal flora may play a key role in the pathogenesis of certain gastrointestinal (GI) diseases. Components of bowel flora such as Lactobacillus acidophilus and Bifidobacterium bifidus have long been used empirically as therapeutic agents for GI disorders. More complex combinations of probiotics for therapeutic bacteriotherapy have also recently become available, however the most elaborate mix of human-derived probiotic bacteria is, by definition, the entire fecal flora. Fecal bacteriotherapy uses the complete normal human flora as a therapeutic probiotic mixture of living organisms. This type of bacteriotherapy has a longstanding history in animal health and has been used sporadically against chronic infections of the bowel, especially as a treatment of last resort for patients with severe Clostridium difficile syndromes including recurrent diarrhea, colitis, and pseudomembranous colitis. Encouraging results have also been observed following infusions of human fecal flora in patients with inflammatory bowel disease, irritable bowel syndrome, and chronic constipation. The therapeutic use of fecal bacteriotherapy is reviewed here and possible mechanisms of action and potential applications explored. Published reports on fecal bacteriotherapy are few in number, and detail the results of small uncontrolled open studies and case reports. Nevertheless, given the promising clinical responses, formal research into fecal bacteriotherapy is now warranted.