Role of Antimicrobial Resistance in Outcomes of Acute Endophthalmitis

BACKGROUND

This study explores local trends in antimicrobial resistance and its influence on long-term visual outcomes following treatment with broad-spectrum empiric intravitreal antibiotics.

METHODS

All patients undergoing intraocular sampling for endophthalmitis from Auckland between January 2006-May 2023 were included. The impact of antimicrobial resistance on the final visual outcome was analysed using logistic regression models.

RESULTS

389 cases of endophthalmitis were included, and 207 eyes (53.2%) were culture positive. When tested, all Gram-positive microorganisms were fully susceptible to Vancomycin, and all Gram-negative microorganisms demonstrated full or intermediate susceptibility to Ceftazidime. Resistance to at least one antimicrobial agent was present in 89 culture results (43.0%), and multidrug resistance (resistant to ≥3 antimicrobials) in 23 results (11.1%). No increase in resistance was observed over time. The primary procedure was a tap and inject in 251 eyes (64.5%), and early vitrectomy was performed in 196 eyes (50.3%). Severe vision loss (≤20/200) occurred in 167 eyes (42.9%). Antimicrobial resistance was associated with an increased risk of retinal detachment (OR 2.455 p = 0.048) but not vision loss (p = 0.288).

CONCLUSION

High sensitivity to Vancomycin and Ceftazidime was present in our population, reinforcing their role as first-line empiric treatments. Resistant microorganisms were associated with an increased risk of retinal detachment but no alteration in final visual outcome.

Evaluation of extraction and amplification assays for the detection of SARS-CoV-2 at Auckland Hospital laboratory during the COVID-19 outbreak in New Zealand

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MagNAPure 96, Panther Fusion, EpMotion 5075 tested for SARS-CoV2 RNA extraction.

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Panther, LC 480, A* Fortitude, Viasure, and GenePro kits tested for SARS-CoV2 RT-PCR.

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Same sets of specimen positives for COVID-19 used across platforms for comparison.

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Median Ct values, ΔCt values and IQR used for comparison of their performance.

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Comparison provided wider options as SARS-CoV-2 PCR testing soared in New Zealand.

Utilising diverse molecular platforms has formed a solid foundation in New Zealand’s COVID-19 response. We evaluated multiple extraction and PCR assays for the detection of SARS-CoV-2.

We included 65 positive samples which were run on the Panther Fusion using a laboratory developed test (LDT, E gene target). Where viral RNA was extracted by MagNA Pure (MP) 96 extraction platform or EpMotion 5075/Geneaid extraction kit, SARS-CoV-2 detection was performed on Light Cycler (LC) 480 using a LDT (E gene) or 3 commercial assays; Certest Viasure (Orf1ab, N genes) GenePro (E, RdRp genes) and A* Star Fortitude (proprietary target).

Median Cts on LC 480 LDT for specimens (n = 9) extracted on MP 96 (26.6) were lower than on EpMotion (31.6) whereas median Cts for specimens (n = 10) extracted on the Panther Fusion LDT (23.1) were comparable with MP 96 /LC480 LDT (23.6).

Specimens tested on Panther Fusion LDT (n = 28), extracted by MP 96, and amplified using commercial assays showed good concordance with a few exceptions; lower median Ct values were seen for 2 targets on GenePro (16.9, 21.5) and Viasure (19.5, 21.1) than for the Panther Fusion LDT (24.2) and A* Star Fortitude (25.6).

Specimens tested on MP 96 (n = 18) had comparable results using commercial assays, with lower median Cts for Viasure (22.2, 23.7) compared with the LC 480 LDT (24.7), GenePro (24.7,25.7) and A*Fortitude (25.1) assays.

The study provides an early assessment of the performance characteristics of 3 extraction methods for viral RNA and 5 PCR assays for the detection of SARS-CoV-2.

Fatal respiratory diphtheria caused by β-lactam-resistant Corynebacterium diphtheriae

BACKGROUND

Diphtheria is a potentially fatal respiratory disease caused by toxigenic Corynebacterium diphtheriae. Although resistance to erythromycin has been recognised, β-lactam resistance in toxigenic diphtheria has not been described. Here, we report a case of fatal respiratory diphtheria caused by toxigenic C. diphtheriae resistant to penicillin and all other β-lactam antibiotics and describe a novel mechanism of inducible carbapenem resistance associated with the acquisition of a mobile resistance element.

METHODS

Long-read whole genome sequencing was performed using Pacific Biosciences SMRT sequencing to determine the genome sequence of C. diphtheriae BQ11 and mechanism of β-lactam resistance. To investigate phenotypic inducibility of meropenem resistance, short read sequencing was performed using an Illumina NextSeq500 sequencer on the strain with and without exposure to meropenem.

RESULTS

BQ11 demonstrated high-level resistance to penicillin (benzylpenicillin MIC ≥ 256 μg/ml), β-lactam/β-lactamase inhibitors and cephalosporins (amoxicillin/clavulanic acid MIC ≥ 256 μg/mL; ceftriaxone MIC ≥ 8 μg/L). Genomic analysis of BQ11 identified acquisition of a novel transposon carrying the penicillin binding protein Pbp2c, responsible for resistance to penicillin and cephalosporins. When strain BQ11 was exposed to meropenem, selective pressure drove amplification of the transposon in a tandem array and led to a corresponding change from a low level to high level meropenem resistant phenotype.

CONCLUSIONS

We have identified a novel mechanism of inducible antibiotic resistance whereby isolates that appear to be carbapenem susceptible on initial testing can develop in vivo resistance to carbapenems with repeated exposure. This phenomenon could have significant implications for treatment of C. diphtheriae infection and may lead to clinical failure.

Age-related differences in SARS-CoV-2 testing in the Northern Region of New Zealand

AIM

There is concern the low incidence of coronavirus disease 2019 (COVID-19) in children reflects under-testing in this population. This study sought to describe the age-distribution of SARS-CoV-2 testing in the Northern Region of New Zealand.

METHODS

A retrospective single-centre review of all SARS-CoV-2 tests performed at LabPLUS, Auckland City Hospital, between 12 February and 18 April 2020.

RESULTS

A total of 22,333 tests were performed, with 313 (1.40%) positive results. The age-adjusted SARS-CoV-2 testing rate was three times higher in adults than in children. The overall proportion of positive tests was lower in children (0.86%) than adults (1.45%). However, within the paediatric population the proportion of tests positive differed significantly between those <10 years old (0.08%) and those 10-14 years old (2.6%).

CONCLUSION

The lower proportion of tests positive in children <10 years of age suggests they are appropriately tested relative to their rates of disease. A large high school-associated cluster makes the higher proportion of tests positive in children 10-14 years old difficult to interpret. Older children may have a higher risk of infection and increasing testing in intermediate and high school aged children may be indicated.

An understanding of discordant SARS-CoV-2 test results: an examination of the data from a central Auckland laboratory

AIM

The diagnostic sensitivity of the SARS-CoV-2 real time reverse transcription polymerase chain reaction (RT-PCR) test has not been determined. This has led to a degree of uncertainty in the interpretation of results, particularly in patients tested repeatedly. The aim of this study was to explore the characteristics of patients who initially tested negative, and subsequently tested positive for SARS-CoV-2.

METHODS

This retrospective observational study utilised data from the LabPlus Virology laboratory, Auckland City Hospital, to identify cases (hospital and community) with initial negative and subsequent positive SARS-CoV-2 RT-PCR results. Their clinical and laboratory characteristics were summarised.

RESULTS

From 1 February to 13 April a total of 20,089 samples were received for SARS-CoV-2 testing. Of 2,011 samples from patients with multiple tests, 25 samples were positive. Nine samples were from patients who initially tested negative then tested positive. Reasons for the initial negative test results, which were all from upper respiratory tract samples, included pre-symptomatic presentation or late presentation. All patients had significant risk factors and ongoing or evolving symptoms, which warranted repeat testing.

CONCLUSION

Few patients had discordant test results for SARS-CoV-2 RT-PCR. For patients who have a significant risk factor and a negative test result, repeat testing should be performed.

Healthcare-associated Staphylococcus aureus bacteraemia: time to reduce the harm caused by a largely preventable event

Staphylococcus aureus disease is associated with significant morbidity and mortality and of concern, it disproportionally affects Māori and Pacific Peoples. New Zealand has high rates of skin and soft tissue infection caused by S. aureus. Healthcare-associated S. aureus bacteraemia (HA-SAB) accounts for a significant proportion of all S. aureus bacteraemia events. Measurement of HA-SAB has been reported in New Zealand for over 20 years but it has not been linked to quality improvement interventions to reduce the rate. It has been used as an outcome measure for the Hand Hygiene New Zealand programme; however, a recent review of submitted data questioned the accuracy of it. This has been addressed. National programmes such as the Health Quality & Safety Commissions Hand Hygiene New Zealand and the Surgical Site Infection Improvement programme have led to reduced harm from healthcare-associated infections. Interventions targeted at reducing the HA-SAB rate, such as bundles of care for insertion and maintenance of vascular access devices and skin and nasal decolonisation of staphylococci prior to surgery, are urgently required.

Aerococcus urinae Aortitis: A Case Report

Background

Aerococcus urinae is a Gram-positive coccus that is increasingly recognized as a urinary pathogen since the introduction of mass spectrometry for identification of bacteria. We report a case of abdominal aortitis (with aneurysm) caused by A urinae in a male with recurrent urinary tract infections and recently treated A urinae bacteremia. A 63-year-old gentleman with a history of A urinae urosepsis 7 weeks prior, presented to the Emergency Department with thoracolumbar back pain radiating bilaterally into the groin. Radiological and surgical findings were consistent with infective infrarenal aortitis with aneurysm.

Methods

The patient successfully underwent open surgical debridement and reconstruction of the infrarenal aorta with autologous vein graft.

Results

Aerococcus urinae was isolated from excised tissue. The patient completed a 4-week course of intravenous antimicrobial therapy.

Conclusions

Aurinae is a urinary pathogen with the ability to cause severe invasive disease including endovascular infections.

Clinical parameters do not predict infection in patients with external ventricular drains: a retrospective observational study of daily cerebrospinal fluid analysis

A retrospective review was conducted of patients with external ventricular drains (EVDs) in situ in order to ascertain the utility of daily cerebrospinal fluid (CSF) analysis in such patients. All laboratory requests for CSF analysis, which were sent to the Microbiology Department, Auckland City Hospital, New Zealand, were reviewed to identify patients with EVDs in situ. The patients' clinical records were reviewed and information was obtained regarding their age, ethnicity, indication for EVD, duration of EVD, CSF analysis results, daily temperatures, Glasgow Coma Scale (GCS) and the presence of other infections. For CSF samples that grew organisms, the patients' notes were reviewed to ascertain whether the organism was a contaminant or was representative of EVD-associated ventriculitis. A total of 454 CSF specimens from 60 patients were reviewed. Of the 56 CSF specimens that were culture-positive, 40 (71 %) were found to reflect clinical infection. Routine CSF analysis identified nine episodes of EVD-associated ventriculitis. Coagulase-negative staphylococci and Staphylococcus epidermidis were the most common isolates and were associated with ventriculitis approximately half of the time. Gram-negative isolates were less frequently isolated, but, when present, were always associated with ventriculitis. This study found that patient temperature and GCS did not allow early prediction of EVD-associated ventriculitis.

Anaerobic bacteraemia in patients admitted to Auckland City Hospital: its clinical significance

AIM

To determine the clinical significance and outcomes for patients with anaerobic bacteraemia at our institution over a 2-year period.

METHOD

The isolates were identified from the laboratory database and patient information obtained from clinical records.

RESULTS

Anaerobes were isolated from 140 blood culture sets taken from 114 patients. For 59 patients, the isolates were considered to be contaminants. Of note, all Propionibacterium spp. were considered contaminants. For the patients with true bacteraemias, the most likely source of infection was intra-abdominal, 26 (50%), mucositis associated with neutropaenia contributed to by cytotoxic therapy, 11 (19%), skin and soft tissue, 4 (8%), pelvic, 5 (9%) and oropharyngeal, 4 (8%). Thirty-five patients were on appropriate therapy prior to the availability culture results. Five patients died but only one death was directly attributable to anaerobic bacteraemia.

CONCLUSION

At our institution, anaerobes accounted for 2.3% of all positive blood cultures. Excluding Propionibacterium spp., most isolates were considered clinically significant. The most common source for the bacteraemia was intra-abdominal infection, followed by mucositis in neutropaenic patients. Empiric antimicrobial therapy provided appropriate cover for two-thirds of the patients. One death was directly attributable to anaerobic bacteraemia.