- Volume 64, Issue 3, 2015

Laryngopharyngeal malignancy is treated with radiotherapy and/or surgery. When total laryngectomy is required, major laryngeal functions (phonation, airway control, swallowing and coughing) are affected. The insertion of a silicone rubber voice prosthesis in a surgically created tracheoesophageal puncture is the most effective method for voice rehabilitation. Silicone, as is the case with other synthetic materials such as polymethylmethacrylate, polyurethane, polyvinyl chloride, polypropylene and polystyrene, has the propensity to become rapidly colonized by micro-organisms (mainly Candida albicans) forming a biofilm, which leads to the failure of the devices. Silicone is used within voice prosthetic devices because of its flexible properties, which are essential for valve function. Valve failure, as well as compromising speech, may result in aspiration pneumonia, and repeated valve replacement may lead to either tract stenosis or insufficiency. Prevention and control of biofilm formation are therefore crucial for the lifespan of the prosthesis and promotion of tracheoesophageal tissue and lung health. To date, the mechanisms of biofilm formation on voice prostheses are not fully understood. Further studies are therefore required to identify factors influencing Candida biofilm formation. This review describes the factors known to influence biofilm formation on voice prostheses and current strategies employed to prolong their life by interfering with microbial colonization.

The purpose of this study was to evaluate the risk factors, outcomes and epidemiology associated with Clostridium difficile infection (CDI) in patients with haematological malignancies in a tertiary care hospital in China. C. difficile screening was performed on patients admitted for chemotherapy or haematopoietic stem cell transplantation between 2009 and 2013. C. difficile isolates were analysed by multilocus sequence typing, and a retrospective chart review was performed on all patients with a positive toxin assay. CDI was diagnosed in 21 haematology–oncology ward patients and 14 marrow transplantation service patients for a cumulative incidence of 1.89/1000 and 3.69/1000 patient-days, respectively. Univariate analyses showed that patients who received etoposide had an increased risk of CDI (odds ratio 4.25, 95 % confidence interval 1.32–13.64). There was only one patient death, for which CDI was not the primary cause. Ten sequence types (STs) were identified, of which ST-3 and ST-54 were the most common; the hypervirulent ST-1 (ribotype 027) and ST-11 (ribotype 078) C. difficile strains were not detected in the patients in this study. The incidence of CDI did not differ between patients receiving chemotherapy and those receiving haematopoietic stem cell transplantation. The only risk factor for chemotherapy patients was treatment with etoposide.

Previous work on the subclones within Escherichia coli ST131 predominantly involved isolates from Western countries. This study assessed the prevalence and antimicrobial resistance attributed to this clonal group. A total of 340 consecutive, non-duplicated urinary E. coli isolates originating from four clinical laboratories in Hong Kong in 2013 were tested. ST131 prevalence among the total isolates was 18.5 % (63/340) and was higher among inpatient isolates (23.0 %) than outpatient isolates (11.8 %, P<0.001), and higher among isolates from patients aged ≥65 years than from patients aged 18–50 years and 51–64 years (25.4 vs 3.4 and 4.0 %, respectively, P<0.001). Of the 63 ST131 isolates, 43 (68.3 %) isolates belonged to the H30 subclone, whereas the remaining isolates belonged to H41 (n = 17), H54 (n = 2) and H22 (n = 1). All H30 isolates were ciprofloxacin-resistant, of which 18.6 % (8/43) belonged to the H30-Rx subclone. Twenty-six (41.3 %) ST131 isolates were ESBL-producers, of which 19 had bla CTX-M-14 (12 non-H30-Rx, two H30-Rx and five H41), six had bla CTX-M-15 (five non-H30-Rx and one H30-Rx) and one was bla CTX-M-negative (H30). In conclusion, ST131 accounts for a large share of the antimicrobial-resistant E. coli isolates from geriatric patients. Unlike previous reports, ESBL-producing ST131 strains mainly belonged to non-H30-Rx rather than the H30-Rx subclone, with bla CTX-M-14 as the dominant enzyme type.

Burn intensive care unit (BICU) patients are specifically exposed to deep-seated nosocomial infections due to Candida albicans. Superficial carriage of C. albicans is a potential source of infection and dissemination, and typing methods could be useful to trace the different isolates. Multilocus sequence typing is a powerful genotyping method for pathogenic micro-organisms, including Candida albicans. Thirty clinical isolates of C. albicans obtained from 22 patients that were admitted to the BICU from a burn hospital at Sari, Mazandaran state, Iran, were studied epidemiologically by multilocus sequence typing (MLST). Seventy-five variable nucleotide sites were found. Sixty-two alleles were identified among the seven loci of the C. albicans isolates and one new allele was obtained. Eighteen diploid sequence types (DSTs) were identified, and among those 10 were new. These isolates belonged to nine clonal clusters (CCs) while two isolates occurred as singletons. Eleven (36.7 %) isolates belonged to CC 124 after eBURST analysis and 13 isolates (43.3 %) were assigned to clade 4. Approximately 17 % of the 30 isolates belonged to clade 1 (CC 69 and CC 766). Isolates from several patients with burns were found to be related genetically. Some patients yielded multiple isolates with identical DSTs, suggesting colonization or infection caused by cross-contamination between patients. Isolates that show identical or similar allelic profiles are presumed to be identical or closely related and may be used to evaluate the genetic relationships between isolates from a specific environment such as the BICU.

Paediatric acute gastroenteritis is a global public health problem. Comprehensive laboratory investigation for viral, bacterial and parasitic agents is helpful for improving management of acute gastroenteritis in health care settings and for monitoring and controlling the spread of these infections. Our study aimed to investigate the role of various pathogens in infantile diarrhoea in Bulgaria outside the classical winter epidemics of rotavirus and norovirus. Stool samples from 115 hospitalized children aged 0–3 years collected during summer months were tested for presence of 14 infectious agents – group A rotavirus, astrovirus, Giardia, Cryptosporidium and Entamoeba using ELISAs; norovirus by real-time RT-PCR; picobirnavirus and sapovirus by RT-PCR; adenovirus using PCR, and Salmonella, Shigella, Escherichia coli, Yersinia and Campylobacter using standard bacterial cultures. Infectious origin was established in a total of 92 cases and 23 samples remained negative. A single pathogen was found in 67 stools, of which rotaviruses were the most prevalent (56.7 %), followed by noroviruses (19.4 %), enteric adenoviruses (7.5 %), astroviruses (6.0 %), bacteria and parasites (4.5 % each) and sapoviruses (1.4 %). Rotavirus predominant genotypes were G4P[8] (46.3 %) and G2P[4] (21.4 %); for astroviruses, type 1a was the most common, while the GII.4/2006b variant was the most prevalent among noroviruses. Bacteria were observed in five cases, with Salmonella sp. as the most prevalent, while parasites were found in ten stool samples, with Giardia intestinalis in five cases. The results demonstrated high morbidity associated with viral infections and that rotavirus and norovirus remain the most common pathogens associated with severe gastroenteritis during summer months in Bulgaria, a country with a temperate climate, and significant molecular diversity among circulating virus strains.

Canine leptospirosis occurs worldwide; however, information on the relationship between Leptospira serotypes/genotypes and virulence in dogs remains limited. We investigated the molecular characteristics of Leptospira interrogans canine isolates belonging to three serogroups using multiple-locus variable-number tandem repeat analysis (MLVA) and the effects of each serotype/genotype on the clinical characteristics of leptospirosis in dogs. MLVA using 11 loci of the three major L. interrogans serogroups in Japan, Australis (32 strains from 21 dogs), Autumnalis (12; 7) and Hebdomadis (66; 39), revealed more divergent genetic heterogeneity within each serogroup than multilocus sequence typing (MLST), and they formed two, three and five clusters (CLs), respectively. Lethal infections were caused by all Leptospira serogroup isolates (70.3 % with Hebdomadis, 83.3 % with Australis and 100 % with Autumnalis) or Leptospira isolates belonging to all the CLs (57.1–100 %) without any significant differences. A significant difference in hyperaemia and haemorrhage of mucus membrane was observed between serogroups Australis and Autumnalis (P = 0.03). Leptospira isolates of Australis CL2 caused no hyperaemia and haemorrhage from mucus membrane, whereas those of Australis CL1, Autumnalis CL3 and Hebdomadis CL1 and CL3 did (P<0.05). Significant differences in creatinine (Cre) levels were observed between serogroups Australis and Hebdomadis (P = 0.02). In addition, significant differences in blood urea nitrogen levels were observed between serogroups Australis and Hebdomadis (P = 0.004) and Australis and Autumnalis (P = 0.02). Based on MLVA types, a significant difference in Cre levels was observed between Hebdomadis CL1 and CL4 (P = 0.0018). Our results indicated that MLVA had a higher discriminatory power and was more concordant with serotyping than MLST. Although all Leptospira serotypes and genotypes caused lethal infections in dogs, the L. interrogans serogroup Australis strains were more likely to cause severe kidney damage than Autumnalis and Hebdomadis, which may be more critical to the outcome of infected dogs than haemorrhage. Our results also suggest that the virulence mechanisms and target organs in dogs may differ by Leptospira genotype.

In BALB/c mouse models of Salmonella enterica serovar Typhimurium infection, a single oral immunization with a mutant strain with an insertion of the chloramphenicol resistance gene into the ATP-dependent protease clpP or lon gene decreased the number of salmonellae in each tissue sample 5 days after oral challenge with virulent S. Typhimurium at weeks 26 and 54 post-immunization. These data suggested that an oral immunization with the ClpP- or Lon-disrupted S. Typhimurium strain could provide long-term protection against oral challenge with virulent S. Typhimurium. Accordingly, recombinant oral non-typhoidal Salmonella (NTS) vaccines were constructed by incorporating mutants of both S. Typhimurium and S. enterica serovar Enteritidis harbouring stable in-frame markerless deletions of the clpP–lon–sulA (suppressor of lon), lon–sulA or lon–msbB (acyltransferase) genes. Amongst these orally administered vaccine candidates, those with the lon–sulA gene deletion mutants of S. Typhimurium and S. Enteritidis protected BALB/c and C57BL/6J mice against oral challenge with both virulent S. Typhimurium and virulent S. Enteritidis. Therefore, the in-frame markerless lon–sulA gene deletion mutant of S. Typhimurium or S. Enteritidis could be a promising cross-protective NTS live vaccine candidate for practical use in humans.