- Volume 67, Issue 12, 2018

We have identified a Salmonella enterica serotype 4,[5],12:i:- containing a mcr-3.2 in a patient who travelled to Thailand 1 month prior to the identification of it in Canada. The isolate was multidrug resistant, but remained susceptible to the carbapenems, amikacin and piperacillin/tazobactam. The mcr-3.2 was carried on a 261 Kb variant of the IncHI2 pWJ1. This report provides further evidence of the emergence of a ST34 colistin-resistant clone.

In this study, we characterized 7C, a spontaneous mutant selected from tigecycline-susceptible Mycobacterium abscessus ATCC 19977. Whole-genome sequencing (WGS) was used to identify possible resistance determinants in this mutant. Compared to the wild-type, 7C demonstrated resistance to tigecycline as well as cross-resistance to imipenem, and had a slightly retarded growth rate. WGS and subsequent biological verifications showed that these phenotypes were caused by a point mutation in MAB_3542c, which encodes an RshA-like protein. In Mycobacterium tuberculosis, RshA is an anti-sigma factor that negatively regulates the heat/oxidative stress response mechanisms. The MAB_3542c mutation may represent a novel determinant of tigecycline resistance. We hypothesize that this mutation may dysregulate the stress-response pathways which have been shown to be linked to antibiotic resistance in previous studies.

Purpose. The plasmid-mediated mcr-1 gene conferring colistin resistance has a strong ability to spread. The objective of this study was to establish a rapid and sensitive recombinase polymerase amplification (RPA) method for plasmid-mediated polymyxin-resistant gene mcr-1 detection.

Methods. Using the reported sequence of the mcr-1 gene, we designed specific primers and probes for RPA. Twenty mcr-1-positive strains carrying IncI2/IncHI2/IncX4/IncP plasmids were screened by RPA in this study. The performance of this new assay was compared to that of PCR, TaqMan probe real-time PCR and SYBR Green-based real-time PCR.

Results. Twenty mcr-1-positive samples and three negative samples were tested by RPA and the positive detection rate for the mcr-1-positive samples was 100 %. The detection limit of RPA was approximately 100 fg. Compared with real-time PCR, the RPA assay was more effective due to shorter reaction times, simpler instruments and higher sensitivity, while it had the same high specificity as real-time PCR.

Conclusion. RPA detection based on the mcr-1 gene was successfully applied in our study. The plasmid-mediated mcr-1 gene conferring colistin drug resistance has a strong ability to spread, suggesting the need to further strengthen the detection of this resistance gene in surveillance. Therefore, we require more sensitive detection methods than have previously been available and the RPA assay established in this study meets these detection needs.

Purpose. Peterborough has one of the highest rates of tuberculosis (TB) in the east of England. We reviewed the epidemiology, management and outcome of all cases of bone and joint TB (BJTB) diagnosed since 2000.

Methodology. Retrospective review of all adult cases of BJTB between 1 January 2000 and 31 December 2015. Patients’ notes were reviewed with regard to their presentation, investigation, management and outcomes.

Results. In total, 21 patients diagnosed with BJTB were reviewed. Thoracic and lumbar spine were the most common sites affected (62 %). The most common clinical manifestations included localized pain (76 %), fever (53 %) and weight loss (48 %). Fourteen (67 %) patients had a bone biopsy or aspirate sent for microbiological investigation; none were smear-positive, but 11 were culture-positive. Eleven patients (77 %) were fully susceptible to anti-tuberculous drugs, one was isoniazid-resistant and one was pyrazinamide-resistant. Anti-tuberculous therapy was given for 6–16 months. Nineteen (90 %) patients completed therapy.

Conclusions. BJTB requires a high index of clinical suspicion. BJTB should be considered in any patient with unexplained pain, fever and weight loss. The diagnosis is proven by aspiration and biopsy and should be undertaken as soon as possible for culture purposes, as microscopy alone can be negative.

Purpose. The analytical performance of the cobas 6800 HIV-1, HBV and HCV assays was verified and evaluated to the COBAS Ampliprep/COBAS TaqMan assays.

Methodology. The precision, limit of detection (LoD), limit of quantification (LoQ) and linearity were verified using pooled residual clinical samples. The analytical specificity was verified with negative plasma. HIV-1 analytical reactivity was verified with WHO reference preparations. Accuracy was verified using EQA plasma panels. Evaluation of the equipment was performed using prospectively collected clinical whole blood samples.

Results. Excellent precision was demonstrated using both testing protocols (coefficient of variation ≤15 %). The LoDs using the 500 and 200 µl protocols were 20 and 50 cp ml−1 for HIV-1, 10 and 20 IU ml−1 for HBV and 15 and 40 IU ml−1 for HCV, respectively. The LoQs were 40 and 100 cp ml−1 for HIV-1, 20 and 25 IU ml−1 for HBV and 30 and 80 IU ml−1 for HCV, respectively. Assays demonstrated good linearity (R2 ≥0.96). The analytical specificity of the assays was 100 %. There was excellent agreement between the cobas 6800 and CAP/CTM assays (kappa>0.94). The sensitivity, specificity, positive predictive value and negative predictive value for each of the assays were ≥99 %. The cobas HIV-1 and HCV mean quantifications were 0.03 log₁₀ cp ml−1 and 0.17 log₁₀ IU ml−1 higher than the CAP/CTM. The cobas HBV mean quantification was 0.17 log₁₀ IU ml−1 lower than the CAP/CTM. Subtype/genotype specific differences were not observed.

Conclusion. Cobas 6800 equipment and assays demonstrated excellent performance and correlated well with CAP/CTM assay results.

Purpose. Differentiation of the Mycobacterium tuberculosis complex (MTBc) from non-tuberculous mycobacteria (NTM) is important for tuberculosis diagnosis and is a prerequisite for reliable phenotypic drug-resistance testing. We evaluated the performance of the rapid MPT64 antigen identification test for the detection of Mycobacterium africanum lineage 5 (MAF L5).

Methodology. Smear-positive tuberculosis patients’ sputa were included prospectively. Culture was performed on Löwenstein–Jensen medium and, when positive, the MPT64 test and the classical para-nitro benzoic acid susceptibility and heat-labile catalase (PNB/catalase) identification tests were performed. The MPT64 test was repeated 14 days after an initially negative first testing. Direct spoligotyping was performed for MTBc lineage determination.

Results. In total, 333 isolates were tested for all of the methods. Three hundred and twenty-two (96.7 %) were pure MTBc, by agreement between spoligotyping and PNB/catalase, and 11 were NTM or a mixture of MTBc/NTM. The MPT64 test conducted on day zero of culture-positivity correctly identified most of the pure MTBc isolates (93.2 %, 300/322), but it failed to detect 24 % of the L5 isolates (18/75) versus 2 % (4/202) of the L4 ones [OR=15.6 (5.3–45.8), P<0.0001], with improved sensitivity for L5 detection on repeat testing after 14 days. The L5-wide non-synonymous single-nucleotide polymorphism in the mpt64 gene may explain the poor performance of the MPT64 test for L5.

Conclusion. The MPT64 test has a lower sensitivity for detecting L5 isolates of the MTBc, and can be considered as a first-screening test that should be confirmed by another identification method when it produces negative results in countries with L5. Given the microbiological bias in both the isolation and identification of MAF lineages, diagnostics with high sensitivity for direct testing on clinical material are preferable.

Carbapenemase-producing organisms (CPOs) represent an increasing threat in healthcare facilities and detection of these organisms in the diagnostic laboratory can be challenging. The EntericBio CPE (EBCPE) real-time PCR assay (Serosep Ltd) was evaluated for the detection of NDM, KPC, OXA-48-like, VIM, IMP and GES carbapenemase genes from a panel of 145 multidrug-resistant organisms (29 NDM, 35 OXA-48, 21 VIM, 4 OXA-23, 3 KPC, 5 NDM+OXA-48, 3 GES-5, 1 OXA-23+NDM, 1 IMI, 2 IMP-1 and 41 multidrug-resistant carbapenemase-negative isolates). The EBCPE assay performed well, with 100 % sensitivity and specificity for the detection of all genotypes included in the assay. Turnaround time and laboratory workflow were improved compared to culture-based assays. Users must remain aware of the limitations of molecular assays for CPO detection to ensure implementation of the most suitable CPO diagnostic pathways.

Purpose. Based on world-wide evaluation, the direct agglutination test (DAT) is now generally acknowledged as one of the leading diagnostics for visceral leishmaniasis (VL). To enhance more routine and mass application, but simultaneously ensure safety to both user and environment, further improvements need to be introduced.

Methodology. In the current format, a two–sixfold titre decrease was observed due to using formaldehyde as an antigen preservative in DAT. Successful formaldehyde preservative exclusion was achieved by increasing its concentration to 3 % (wt/vol) for conserving promastigote status after β-mercaptoethanol (β-ME) treatment and repeating exposure of the parasite to the fixative after Coomassie Brilliant Blue staining.

Results. Microbial contamination was not observed in any of the antigen aliquots preserved in 0.05 % (wt/vol) sodium dichloroisocyanurate (chlorine) instead of formaldehyde for 6 months or longer. By excluding formaldehyde, restoring the normal antibody level, prior to treatment of sera with β-ME only minimally influenced the test outcome. A comparable successful reduction in non-specific agglutination, as with β-ME, was achieved by incorporating urea (0.3 % wt/vol) in the improved DAT procedure (P=0.646; T=23.0). As with the current procedure, the improved equivalent (formaldehyde and β-ME free) showed good reliability for VL detection (VL – Fr=52.39, W=0.70, P<0.001; and non-VL – Fr=65.97, W=0.83, P<0.001). A much lower cut-off (titre 1 : 400 versus 1 : 3200) for VL diagnosis can be adopted if urea is integrated in the improved procedure.

Conclusions. By introducing the modifications mentioned, we think we have succeeded to a reasonable degree in increasing the DAT potential for VL control.

Purpose. The aim of this work was to evaluate and optimize the identification of Bordetella pertussis, Bordetella parapertussis and Bordetella bronchiseptica (usually known as the classical Bordetella species) using Bruker Biotyper matrix-assisted laser desorption ionization/time-of-flight mass spectrometry (MALDI-TOF MS).

Methodology. A set of 106 previously characterized clinical isolates was used. The results were interpreted according to the manufacturer’s recommendations and, in addition, a new score value cutoff was used for species identification. Further, the 10 % rule (previously adopted by other authors) and the new 5 % breaking point (proposed in this work) were evaluated in order to optimize identification rates.

Results/Key findings. Our results suggest that it is possible to distinguish different species of the classical Bordetella species by following a simple algorithm without additional testing being required.

Conclusion. MALDI-TOF might be a reliable tool for the identification of this group of bacteria when a combination of cutoff scores is used. This procedure allows us to increase the identification rates for the classical Bordetella species significantly; however, more studies will be required to determine the applicability of the method to other difficult-to-distinguish organisms.

In this study, we evaluated the Sofia Streptococcus pneumoniae FIA test (Quidel Corporation, San Diego, CA, USA), a new immunofluorescence-based lateral flow test for the qualitative detection of S. pneumoniae antigen in urine or cerebrospinal fluid specimens. The analyses of 100 non-concentrated urine samples (including 50 samples from S. pneumoniae cases) showed a sensitivity and specificity (95 % CI) of, respectively, 66.0 % (52.2–77.6) and 100.0 % (92.9–100.0) for the Sofia test, and 62.0 % (48.2–74.1) and 98.0 % (89.5–99.7) for the BinaxNOW SPN Antigen Card. There were no significant differences in sensitivity and specificity between the tests (McNemar’s tests, P=0.625 and P=1.000). In conclusion, this study indicates that the Streptococcus pneumoniae FIA test shows similar sensitivity and specificity rates compared to the BinaxNOW SPN Antigen Card.

Purpose. To investigate the clinical, phenotypic and genotypic characteristics of Staphylococcus aureus strains causing osteoarticular infections in a large paediatric series.

Methodology. Medical records of children who were hospitalized with the diagnosis of community-associated S. aureus (CA-SA) osteomyelitis and/or septic arthritis in the two major tertiary paediatric hospitals of Athens during an 8-year period (2007–2015) were reviewed, and S. aureus isolates were analysed regarding antimicrobial resistance, detection of pathogenicity genes and genotyping using SCCmec, agr typing, PFGE and MLST.

Results. During the study period, 123 children with CA-SA osteoarticular infections were identified, and methicillin-resistant S. aureus (MRSA) accounted for 44 of these (35.8 %). Children with MRSA infection had a significantly higher admission rate to the ICU (5.7  vs 0 %, P=0.04) and longer duration of hospitalization (21.6 vs 16.7 days, P=0.04). Sixty-eight isolates [42 (methicillin-sensitive S. aureus) MSSA and 26 MRSA] were available for molecular analysis. All MRSA strains were mecA-positive and most carried the SCCmec IV cassette (23/26, 88 %) and belonged to the PFGE type C (24/26, 92.3 %), agr type 3 (24/26, 92.3 %) and the MLST ST80 clone (24/26, 92.3 %). In contrast, MSSA strains showed polyclonality by PFGE and agr typing. Regarding pathogenicity genes, MRSA vs MSSA isolates showed higher detection rates of PVL (96.2 vs 4.8 %, P<0.0001) and fib (80.8 vs 50 %, P=0.02).

Conclusions. In our study a considerable number of S. aureus osteoarticular infections were due to CA-MRSA isolates, most of which belonged to the ST80 clone and had a higher incidence of specific virulence factors, entailing higher ICU admission rates and a longer duration of hospitalization.

Purpose. Hand hygiene is the most important strategy for preventing healthcare-associated infections (HCAIs); however, the impact of hand hygiene in middle-income countries has been poorly described. In this work, we describe the impact of the programme ‘Let’s Go for 100’ on hand hygiene adherence, HCAIs rates and multidrug-resistant (MDR) bacteria, including the molecular typing of methicillin-resistant Staphylococcus aureus (MRSA) strains.

Methodology. A multimodal, hospital-wide hand hygiene programme was implemented from 2013. ‘Let’s Go for 100’ involved all healthcare workers and encompassed education, awareness, visual reminders, feedback and innovative strategies. Monthly hand hygiene monitoring and active HCAI surveillance were performed in every ward. Molecular typing of MRSA was analysed by pulsed-field gel electrophoresis (PFGE).

Results/Key findings. Hand hygiene adherence increased from 34.9 % during the baseline period to 80.6 % in the last 3 months of this study. The HCAI rate decreased from 7.54 to 6.46/1000 patient-days (P=0.004). The central line-associated bloodstream infection (CLABSIs) rate fell from 4.84 to 3.66/1000 central line-days (P=0.05). Negative correlations between hand hygiene and HCAIs rates were identified. The attack rate of MDR-ESKAPE group bloodstream infections decreased from 0.54 to 0.20/100 discharges (P=0.024). MRSA pulsotypes that were prevalent during the baseline period were no longer detected after the 5th quarter, although new strains were identified.

Conclusions. A multimodal hand hygiene programme in a paediatric hospital in a middle-income country was effective in improving adherence and reducing HCAIs, CLABSIs and MDR-ESKAPE bloodstream infections. Sustaining hand hygiene adherence at a level of >60 % for one year limited MRSA clonal transmission.

We have cultured and phenotyped human adipose tissue-derived mesenchymal stem/stromal cells (AT MSCs) and inoculated these cultures with bacteria common to infected skin wounds, i.e. Staphylococcus aureus and Pseudomonas aeruginosa. Cell interactions were examined by scanning electron microscopy (SEM), whilst bacterial growth was measured by colony forming unit (c.f.u.) and biofilm assays. AT MSCs appeared to attach to the bacteria and to engulf S. aureus. Significantly fewer bacterial c.f.u. were present in AT MSC : bacterial co-cultures compared with bacteria cultured alone. Antibacterial activity, including an inhibition of P. aeruginosa biofilm formation, was observed when bacteria were treated with conditioned medium harvested from the AT MSC :  bacterial co-cultures, irrespective of the bacterial species to which the AT MSCs had been exposed to previously. Hence, we have demonstrated that AT MSCs inhibit the growth of two common bacterial species. This was associated with bacterial adhesion, potential engulfment or phagocytosis, and the secretion of antibacterial factors.