In clinical environments, orthopedic implants are associated with a risk of infection during implantation. However, the growth paths of bacteria on metal, which is nontransparent, are difficult to observe. In this study, we visualized the DH5-alpha Escherichia coli bacterial growth path on the surface of magnesium by using scanning electron microscope (SEM) images and constructed a convolutional neural network-based artificial intelligence (AI) system to identify metal surfaces, bacteria, and its generated products to grade the growth stage of the bacteria implanted on the magnesium. The detection result of the E. coli growth stage by the AI system was close to that manually marked by experts, and it may greatly accelerate the investigation of the bacterial growth process in various types of metallic material.

Different Saskatchewan soils were studied to determine their populations of 2,4-D [(2,4-dichlorophenoxy) acetic acid] degraders and gross aerobic bacteria. Soil from Indian Head field plots receiving relatively high field rates (1.12 or 1.68 kg/ha) of 2,4-D amine or ester applied annually over the previous 32 yr contained the highest population of degraders, ranging from 103 to 104 degraders/g soil. Control plots recorded lower populations of degraders (2.5 ± 0.5 × 103 degraders/g soil). Five soils from around the province were also studied, and a relationship was found between the rate of breakdown of 14C-2,4-D in the soil and the number of degraders. Another soil from a different site at Indian Head, but of a similar type to that in the field plots, displayed a much slower rate of 2,4-D degradation and also a much lower degrader population (7 ± 2 degraders/g soil) when compared to the other four soils (4 × 102 to 9 × 102 degraders/g soil). The ratio of degraders to the total bacterial flora varied in all studies between 1:6.5 × 102 and 1:3 × 105. When 1030 soil isolates were screened for their ability to degrade 2,4-D using an agar-block extraction technique, none possessed this feature. This would support the hypothesis that the ratio of 2,4-D degraders to the total microbial flora was indeed large (at least 1:103).

The bioremediation of Antarctic soils is a challenge due to the harsh conditions found in this environment. To characterize better the effect of total petroleum hydrocarbon (TPH) concentrations on bacterial, archaeal and microeukaryotic communities in low (LC) and high (HC) hydrocarbon-contaminated soil samples from the Maritime Antarctic clone libraries (small-subunit rRNA genes) were constructed. The results showed that a high concentration of hydrocarbons resulted in a decrease in bacterial and eukaryotic diversity; however, no effect of the TPH concentration was observed for the archaeal community. The HC soil samples demonstrated a high relative abundance of bacterial operational taxonomic units (OTUs) affiliated with unclassified group TM7 and eukaryotic OTUs affiliated with unclassified fungi from Pezizomycotina subphyla. Chemical analyses of the LC and HC soil samples revealed the presence of negligible amounts of nitrogen, thereby justifying the use of biostimulation to remediate these Antarctic soils. Microcosm experiments showed that the application of fertilizers led to an increase of up to 27.8% in the TPH degradation values. The data presented here constitute the first step towards developing the best method to deploy bioremediation in Antarctic soils and provide information to indicate an appropriate action plan for immediate use in the case of new accidents.

Objective: To detect the presence of bacteria in mastoid granulations and compare its prevalence in both types of chronic suppurative otitis media (CSOM). To find out if stage of disease activity, age, duration of disease, and aditus patency relate to obtaining positive cultures.

Study design and setting: A prospective, parallel group study done at a tertiary care referral centre. Mastoid granulations from 79 patients with CSOM undergoing mastoidectomy were processed for anaerobic and aerobic bacteria.

Results: Aerobes were isolated from 57.55 per cent of the tubotympanic and 74.4 per cent of atticoantral disease (p = 0.18). Anaerobic cultures were positive in one case from each group. Monomicrobial growth was detected in 37.5 per cent of tubotympanic and 48.5 per cent of atticoantral disease. Polymicrobial growth occurred in 20 per cent and 25.6 per cent in the tubotympanic and atticoantral groups, respectively. The predominant aerobic isolate was coagulase negative Staphylococcus, followed by Pseudomonas aeruginosa, Staphylococcus aureus, non-fermenting Gram-negative bacteria, Enterobacter and Enterococcus, Proteus species, Citrobacter, non-pathogenic Neisseria, aerobic spore formers were grown only in atticoantral disease. A single isolate of Aspergillus was grown. Correlating the state of disease activity of the ears with positive mastoid granulation cultures, six out of the eight inactive ears were culture positive along with seven out of the nine active and 10 out of the 23 quiescent ears. Positive mastoid granulation cultures were obtained in 60 per cent of those with blocked aditus and 42.9 per cent with patent aditus.

Conclusion and significance: In this study, we found that mastoid granulations are not sterile but harbour polymicrobial pathogens. Positive cultures were obtained irrespective of stage of disease activity, age, duration of disease and aditus patency. The pattern of organisms cultured from safe and unsafe CSOM and also from ears in active, quiescent and inactive stages, were similar. These findings suggest that these organisms may be responsible for mastoid granulations. We also noted that positive cultures had no statistical correlation with aditus patency and duration of disease. We suggest further studies to evaluate the significance of asymptomatic mastoid granulations harbouring organisms and whether opening the mastoid antrum and achieving aditus patency, irrespective of the stage of disease activity, will help improve the long-term surgical outcome and also prevent recurrence of ear discharge.

Acute otitis media and otitis media with effusion (OME) have often been observed in children with bacterial meningitis. OME has also been proposed as the mechanism of reversible hearing loss after meningitis. In this controlled study, children with acute bacterial meningitis were studied using auditory brainstem responses (ABR), otoacousticemissions, tympanometry and otoscopy. An age- and sex- matched control was recruited for each patient and the incidence of acute otitis media and OME was compared between the twogroups. One hundred and twenty-four children with meningitis were studied. Ninety-two children (74 per cent) had meningococcal meningitis. Five patients (4 per cent) had conductive hearing loss (ABR threshold≥30 dB HL) at the time of discharge from hospital. None of the patients or controls had acute otitis media. Patients and controls were well matched for risk factors for OME and the prevalence of middle ear effusion in patients and controls was 7.2 per cent and 11.3 per cent respectively. The relative risk of OME in the children with meningitis was 0.64 (95 per cent confidence interval 0.29 to 1.42). After nine months, three of the five children with meningitis and conductive hearing loss had regained normal hearing.

In contrast to previous reports, there was no relationship between bacterial meningitis and acute otitis media or OME in this study. Nevertheless, coincidental conductive hearing defects were identified as the cause of reversible hearing loss in three patients.

The hearing function of 50 children with bacterial meningitis was evaluated at the second and 10th days, and eight weeks after admission with auditory brain system responses (ABR) to investigate whether meningitis causes hearing loss. Normal values were obtained in all tests from both ears of 24 patients (48 per cent). Twelve patients (24 per cent) had temporary, and seven (14 per cent) patients had persistent mild degree hearing loss. Severe hearing loss was detected bilaterally in five (10 per cent) patients and unilaterally in two (four per cent) patients. Patients with other complications such as subdural effusion, convulsion, brain oedema and paralysis were found to have a higher incidence of hearing loss. We observed that patients treated with dexamethasone had 7.7 per cent persistent hearing loss, 11.6 per cent mild hearing loss, 34.6 per cent transient hearing loss, but in the group who did not receive dexamethasone there was 19.2 per cent persistent hearing loss, 15.3 per cent mild hearing loss and 11.6 per cent transient hearing loss. There were other signficant differences between the two groups in restoration of normal body temperature, the CSF/plasma glucose concentration ratio was elevated, CSF (cerebro-spinal fluid) protein concentration was decreased and the cell count in the CSF was decreased in the dexamethasone group, significantly more than the group who were not receiving dexamethasone. The hearing loss tended to be more frequent among younger children.