A positive correlation exists between the pathogenicity of bacteria and fungi when evaluated in the insect Galleria mellonella and mice. This work sought to determine whether fluctuations in the number of haemocytes and the proliferation of yeast cells in infected larvae could be used to determine the relative pathogenicity of a range of yeast isolates. Larvae were inoculated with 1 × 10 6 stationary-phase yeast cells and incubated in the dark at 30°C for 48 h. The results indicated that larvae inoculated with the most pathogenic isolates (i.e. those capable of killing >80% of infected larvae) showed a significant reduction in haemocyte density. Larvae inoculated with isolates of low pathogenicity (i.e. capable of killing <20% of infected larvae) demonstrated only a small fluctuation in haemocyte numbers. The most pathogenic yeast isolates proliferated in the larvae, whereas the isolates of low pathogenicity did not. These results demonstrate a relationship between the ability of yeast isolates to kill larvae and changes in haemocyte density and yeast cell density in infected larvae. These end points may extend the applicability of the G. mellonella system for use with a wider range of microbial isolates.

Candida albicans is a dimorphic human pathogen in which the yeast to hyphal switch may be an important factor in virulence in mammals. This pathogen has recently been shown to also kill insects such as the Greater Wax Moth Galleria mellonella when injected into the haemocoel of the insect larvae. We have investigated the effect of previously characterised C. albicans mutations that influence the yeast to hyphal transition on virulence in G. mellonella larvae. There is a good correlation between the virulence of these mutants in the insect host and the virulence measured through systemic infection of mice. Although the predominant cellular species detected in G. mellonella infections is the yeast form of C. albicans, mutations that influence the hyphal transition also reduce pathogenicity in the insect. The correlation with virulence measured in the mouse infection system suggests that Galleria may provide a convenient and inexpensive model for the in vivo screening of mutants of C. albicans.

Objective The primary goal of nonlinear frequency compression (NFC) and other frequency lowering strategies is to increase the audibility of high-frequency sounds that are not otherwise audible with conventional hearing-aid processing due to the degree of hearing loss, limited hearing aid bandwidth or a combination of both factors. The aim of the current study was to compare estimates of speech audibility processed by NFC to improvements in speech recognition for a group of children and adults with high-frequency hearing loss. Design Monosyllabic word recognition was measured in noise for twenty-four adults and twelve children with mild to severe sensorineural hearing loss. Stimuli were amplified based on each listener’s audiogram with conventional processing (CP) with amplitude compression or with NFC and presented under headphones using a software-based hearing aid simulator. A modification of the speech intelligibility index (SII) was used to estimate audibility of information in frequency-lowered bands. The mean improvement in SII was compared to the mean improvement in speech recognition. Results All but two listeners experienced improvements in speech recognition with NFC compared to CP, consistent with the small increase in audibility that was estimated using the modification of the SII. Children and adults had similar improvements in speech recognition with NFC. Conclusion Word recognition with NFC was higher than CP for children and adults with mild to severe hearing loss. The average improvement in speech recognition with NFC (7%) was consistent with the modified SII, which indicated that listeners experienced an increase in audibility with NFC compared to CP. Further studies are necessary to determine if changes in audibility with NFC are related to speech recognition with NFC for listeners with greater degrees of hearing loss, with a greater variety of compression settings, and using auditory training.

Objectives: Children with hearing loss listen and learn in environments with noise and reverberation, but perform more poorly in noise and reverberation than children with normal hearing. Even with amplification, individual differences in speech recognition are observed among children with hearing loss. Few studies have examined the factors that support speech understanding in noise and reverberation for this population. This study applied the theoretical framework of the Ease of Language Understanding (ELU) model to examine the influence of auditory, cognitive, and linguistic factors on speech recognition in noise and reverberation for children with hearing loss.Design: Fifty-six children with hearing loss and 50 age-matched children with normal hearing who were 7-10 years-old participated in this study. Aided sentence recognition was measured using an adaptive procedure to determine the signal-to-noise ratio for 50% correct (SNR50) recognition in steady-state speech-shaped noise. SNR50 was also measured with noise plus a simulation of 600 ms reverberation time. Receptive vocabulary, auditory attention, and visuospatial working memory were measured. Aided speech audibility indexed by the Speech Intelligibility Index was measured through the hearing aids of children with hearing loss.Results: Children with hearing loss had poorer aided speech recognition in noise and reverberation than children with typical hearing. Children with higher receptive vocabulary and working memory skills had better speech recognition in noise and noise plus reverberation than peers with poorer skills in these domains. Children with hearing loss with higher aided audibility had better speech recognition in noise and reverberation than peers with poorer audibility. Better audibility was also associated with stronger language skills.Conclusions: Children with hearing loss are at considerable risk for poor speech understanding in noise and in conditions with noise and reverberation. Consistent with the predictions of the ELU model, children with stronger vocabulary and working memory abilities performed better than peers with poorer skills in these domains. Better McCreery et al. Speech Recognition in Adverse Conditions aided speech audibility was associated with better recognition in noise and noise plus reverberation conditions for children with hearing loss. Speech audibility had direct effects on speech recognition in noise and reverberation and cumulative effects on speech recognition in noise through a positive association with language development over time.

Objective We examined how cognitive and linguistic skills affect speech recognition in noise for children with normal hearing. Children with better working memory and language abilities were expected to have better speech recognition in noise than peers with poorer skills in these domains. Design As part of a prospective, cross-sectional study, children with normal hearing completed speech recognition in noise for three types of stimuli: (1) monosyllabic words, (2) syntactically correct but semantically anomalous sentences and (3) semantically and syntactically anomalous word sequences. Measures of vocabulary, syntax and working memory were used to predict individual differences in speech recognition in noise. Study sample Ninety-six children with normal hearing, who were between 5 and 12 years of age. Results Higher working memory was associated with better speech recognition in noise for all three stimulus types. Higher vocabulary abilities were associated with better recognition in noise for sentences and word sequences, but not for words. Conclusions Working memory and language both influence children’s speech recognition in noise, but the relationships vary across types of stimuli. These findings suggest that clinical assessment of speech recognition is likely to reflect underlying cognitive and linguistic abilities, in addition to a child’s auditory skills, consistent with the Ease of Language Understanding model.