Acceptability of digital anal cancer screening examinations in HIV-positive homosexual men

OBJECTIVES

Anal cancer is more common in HIV-positive homosexual men than in HIV-negative homosexual men and the general population. Earlier diagnosis leads to improved prognosis. We aimed to determine if regular anal inspection and digital examination of asymptomatic homosexual men attending for routine HIV care were acceptable and to record the rate of referral for diagnosis of potentially malignant anal lesions.

METHODS

We offered anal examinations to consecutive homosexual men with HIV infection aged ≥ 35 years during their routine HIV clinic visits, aiming to complete three examinations over a 12-month period. Acceptability questionnaires were completed at baseline and after each examination and doctors recorded examination findings and all resulting interventions. Hospital referral outcomes were collected and interventions were costed using the Australian Medical Benefits Schedule.

RESULTS

Of 142 men who were offered enrolment in the study, 102 [72%; 95% confidence interval (CI) 64-79%] participated. Following the initial anal examinations, four men were referred to surgeons. Cancer was excluded in three men (3%; 95% CI 1-8%) and one was diagnosed with anal squamous cell carcinoma (SCC). Three men had anoscopy performed at the time and two were referred for colonoscopy. Ninety-eight per cent (95% CI 93-100%) of respondents said that they would probably have the examination next time. The intervention was estimated to cost approximately Australian $16 per examination.

CONCLUSIONS

Regular anal digital examinations are an acceptable and inexpensive addition to the routine care of homosexual men with HIV infection.

HIV-testing of men who have sex with men: variable testing rates among clinicians

High HIV testing coverage of high-risk populations is required to reduce the number of HIV-infected individuals unaware of their status. The aim of this study was to determine HIV testing rates among men who have sex with men (MSM) attending a sexual health service, including the impact of the treating clinician on HIV testing rates. Factors associated with HIV testing of MSM attending the Melbourne Sexual Health Centre for the first time between 2003 and 2009 were determined, including testing rates for individual treating clinicians. Overall, 78% of 4425 men were tested for HIV. Clinician HIV testing rates were higher among nurses (median 89%; range 77–95%) than doctors (median 73%; range 45–88%) with significant differences between individual physicians ( P < 0.001). Lower testing among doctors was independent of reported sexual risk and time since the last HIV test. Substantial differences in HIV testing rates between clinicians were evident with low testing by some. Increasing HIV testing rates among high-risk groups require engagement not only of individuals at risk but also awareness among health-care providers who perform HIV testing.

Does MR perfusion imaging impact management decisions for patients with brain tumors? A prospective study

BACKGROUND AND PURPOSE

MR perfusion imaging can be used to help predict glial tumor grade and disease progression. Our purpose was to evaluate whether perfusion imaging has a diagnostic or therapeutic impact on clinical management planning in patients with glioma.

MATERIALS AND METHODS

Standard MR imaging protocols were interpreted by a group of 3 NRs in consensus, with each case being interpreted twice: first, including routine sequences; and second, with the addition of perfusion imaging. A multidisciplinary team of treating physicians assessed tumor status and created hypothetical management plans, on the basis of clinical presentation and routine MR imaging and then routine MR imaging plus perfusion MR imaging. Physicians' confidence in the tumor status assessment and management plan was measured by using Likert-type items.

RESULTS

Fifty-nine consecutive subjects with glial tumors were evaluated; 50 had known pathologic diagnoses. NRs and the treatment team agreed on tumor status in 45/50 cases (κ = 0.81). With the addition of perfusion, confidence in status assessment increased in 20 (40%) for NRs and in 28 (56%) for the treatment team. Of the 59 patient-care episodes, the addition of perfusion was associated with a change in management plan in 5 (8.5%) and an increase in the treatment team's confidence in their management plan in 34 (57.6%). NRs and the treatment team found perfusion useful in most episodes of care and wanted perfusion included in future MR images for >80% of these subjects.

CONCLUSIONS

Perfusion imaging appears to have a significant impact on clinical decision-making and subspecialist physicians' confidence in management plans for patients with brain tumor.

Age-related changes in kallikreins-kinins system in rat corpus cavernosum

Many factors, such as nitric oxide synthase, androgen and growth factors, can regulate the tone of corpus cavernosum (CC) smooth muscle with an age-related tendency. It has been shown that the active metabolites of kallikreins-kinins system (KKS), including bradykinin, Lys-BK and Met-Lys-BK, can also relax the CC smooth muscle significantly in vitro. Our aim was to evaluate the specific association between KKS and age in rat CC. CC and thoracic aorta were isolated from rats at postnatal weeks (PW) of 2, 8, 12, 20, 30, 40 and 60, respectively. Tissue kallikrein-I (KLKI) and kinin B2 receptor (B2R) mRNA in CC and thoracic aorta were detected by real-time polymerase chain reaction (PCR). Protein expression of KLKI and B2R were determined with immunofluorescence in situ and Western blot. Real-time PCR, immunofluorescence in situ and Western blot all demonstrated that the age-related changes in expression of KLKI were similar between the CC and thoracic aorta. It significantly increased with age from PW2 to PW30, reached the peak at PW30 and then declined gradually. However, there was no statistically significant difference among PW30, PW40 and PW60. Similarly, the expression of B2R increased gradually with age reached and remained at the peak during adult stages and no significant differences were found among PW20, PW30 and PW40; then, it decreased significantly at PW60. The changes in the expression of B2R in CC and age-matched aorta were similar except that it was significantly less than that in the aorta at PW60. The expression of KLKI and B2R changed in an age-dependent pattern in rat CC and have a tendency to decline during ageing, which is of the same tendency as reported for erection capacity in ageing males and suggests why ageing is an independent predictor of ED, to some extent.

Australian men who have sex with men prefer rapid oral HIV testing over conventional blood testing for HIV

This study examined the views of 172 community-based Australian men who have sex with men (MSM) on the acceptability and potential uptake of rapid oral testing for HIV in clinic and home-based settings. Men were asked to complete a questionnaire that sought their views on rapid testing for HIV. When asked about which HIV test they would prefer in a clinic setting, 64% indicated a preference for rapid oral HIV testing and 74% indicated that if rapid oral HIV testing was available at a clinic they would test for HIV more frequently. If rapid oral HIV testing was available for home testing, 63% of men indicated it would be likely they would test themselves for HIV and 61% indicated they would test more frequently. Overall, MSM expressed a preference for rapid oral HIV testing and would test more frequently if testing was available for clinic or home use in Australia.

Definitions of antiretroviral treatment failure for measuring quality outcomes

OBJECTIVES

Our aim was to compare three different definitions of treatment failure and discuss their use as quality outcome measures for a clinical service.

METHODS

Data for treatment-naïve patients who attended the Melbourne Sexual Health Centre (MSHC) between 1 January 2000 and 31 December 2008 were analysed. Definition 1 was the strict Food and Drug Administration (FDA) definition of treatment failure as determined using the time to loss of virological response (TLOVR) algorithm. Definition 2 defined treatment failure as occurring in those whose viral load never fell to <400 HIV-1 RNA copies/mL or who developed two consecutive viral loads > or =400 copies/mL on any treatment (switching or stopping treatment with a viral load <400 copies/mL was permitted). Definition 3 was the same as definition 2 except that individuals were also deemed to have failed if they stopped treatment for 6 months or longer.

RESULTS

There were 310 antiretroviral-naïve patients who started treatment in the study period. Of these, 156 [50.3%; 95% confidence interval (CI) 42.1-53.3%] experienced treatment failure under definition 1, 10 (3.2%; 95% CI 1.5-5.8%) experienced treatment failure under definition 2, and 16 (4.5%; 95% CI 2.5-7.4%) experienced treatment failure under definition 3 over the 108 months of follow-up. The probability of failing definition 1 was statistically different from the probability of failing definition 2 or 3 (P=0.01).

CONCLUSION

There were significant differences in treatment failure for the three definitions. If definition 1 were used, the outcomes would be sufficiently common to enable clinics to be compared but would be less meaningful. If definition 2 or 3 were used, the events would be too rare to enable clinics to be compared, but it would be possible to set a benchmark level of success that clinics could aim to reach.

Rapid decline in presentations of genital warts after the implementation of a national quadrivalent human papillomavirus vaccination programme for young women

OBJECTIVE

This study aimed to determine if the Australian human papillomavirus (HPV) vaccination programme has had a population impact on presentations of genital warts.

METHODS

Retrospective study comparing the proportion of new clients with genital warts attending Melbourne Sexual Health Centre (MSHC) from January 2004 to December 2008. Australia provided free quadrivalent HPV vaccine to 12-18-year-old girls in a school-based programme from April 2007, and to women 26 years and younger through general practices from July 2007.

RESULTS

36,055 new clients attended MSHC between 2004 and 2008 and genital warts were diagnosed in 3826 (10.6%; 95% CI 10.3 to 10.9). The proportion of women under 28 years with warts diagnosed decreased by 25.1% (95% CI 30.5% to 19.3%) per quarter in 2008. Comparing this to a negligible increase of 1.8% (95% CI 0.2% to 3.4%) per quarter from the start of 2004 to the end of 2007 also in women under 28 years generates strong evidence of a difference in these two trends (p<0.001). There was no evidence of a difference in trend for the quarterly proportions before and after the end of 2007 for any other subgroup, and on only one occasion was there strong evidence of a trend different to zero, for heterosexual men in 2008 in whom the average quarterly change was a decrease of 5% (95% CI 0.5% to 9.4%; p = 0.031).

CONCLUSIONS

The data suggest that a rapid and marked reduction in the incidence of genital warts among vaccinated women may be achievable through an HPV vaccination programme targeting women, and supports some benefit being conferred to heterosexual men.

Delay in the diagnosis of early syphilis among men who have sex with men: need for greater community and health provider education

The objective of this study was to determine the duration between onset of symptoms of early symptomatic syphilis and diagnosis among men who have sex with men (MSM). A review of cases of primary and secondary syphilis among MSM presented to the Melbourne Sexual Health Centre between January 2003 and August 2007. The mean age of the 123 MSM included was 37 years. Fifty-two percent (n = 64) presented with primary syphilis and 48% (n = 59) with secondary syphilis. Twenty-five percent were HIV-positive. The median rapid plasma reagin titre was 1:32. Of the 34 men referred by general practitioners, referring practitioners did not consider the diagnosis of syphilis in 10 cases of primary syphilis and 20 cases of secondary syphilis. For primary and secondary cases combined, the median duration between onset of symptoms and diagnosis, and onset of symptoms and treatment, was 15 (3-56) and 20 (1-57) days, respectively. The respective durations for secondary syphilis (17 and 23 days) was longer than for primary syphilis (13 and 15 days) (P < 0.05). The mean number of sex partners reported for the prior three months was 8.8 (range 1-15). If early detection and treatment of syphilis is to be optimized in order to improve syphilis control, greater awareness of its symptoms and signs of syphilis need to be promoted among both health-care providers and affected communities.

What female patients feel about the offer of a chaperone by a male sexual health practitioner

The aim of this study was to determine the experience and views of female patients when they were offered a chaperone by a male sexual health practitioner for a genital examination. Between November 2007 and January 2008, an anonymous survey was administered to female patients seen by male practitioners at Melbourne Sexual Health Centre. None of the 79 (95% CI 0-5%) patients who were offered a chaperone and declined one reported that they were uncomfortable declining the offer. The qualitative analysis showed that some participants appreciated being offered the option of a chaperone even if they did not want one and that the professional attributes of the practitioner influenced their decision not to have a chaperone. Only 8% (95%CI 4-15%) felt uncomfortable when asked if they would like a chaperone. The results reassure that when a female patient declines the offer of a chaperone within a sexual health clinic, the male practitioner can feel confident that this is the expression of the patient's wish.

Risk profile of walk-in triage compared with an appointment-based phone-triage evening clinic

The aim of this study is to compare risk factors in new clients attending the walk-in triage-based day clinic (WITS) to those attending a telephone-triage appointment-based evening clinic of a sexual health service. The method involves an audit of computerized medical records of new clients attending between July 2002 and December 2007. There were 37,833 new clients of which 37,223 (98.4%) attended WITS and 610 (1.6%) attended the evening clinic. WITS clients were significantly older (31% vs. 30%, P < 0.041), more likely to be male (58% vs. 43%, P < 0.001), sex workers (6% vs. 3%, P < 0.001), not employed (34% vs. 10%, P < 0.001), diagnosed with gonorrhoea (1.7% vs. 0.7%, P < 0.041), herpes (4% vs. 2%, P < 0.000), non-specific urethritis (6% vs. 2%, P < 0.000) and less likely asymptomatic (35.1% vs. 53.4%, P < 0.001). Men attending WITS had significantly more female partners in the 12 months (3.9 vs. 3.0, P < 0.001), but other risks were similar in both clinics. A telephone-triage appointment-based evening clinic is important for asymptomatic high-risk individuals.

Factors associated with traumatic fluoroscopy-guided lumbar punctures: a retrospective review

BACKGROUND AND PURPOSE

To minimize diagnostic confusion, a CSF specimen should be free from traumatically introduced red blood cells (RBCs). The purpose of this research is to determine if patient age, sex, gauge of the lumbar puncture (LP) needle, or the level of LP is associated with an increased risk for traumatic fluoroscopy-guided LP.

MATERIALS AND METHODS

Data were collected retrospectively for consecutive male and female patients of all ages (n = 756) who underwent a fluoroscopy-guided LP for a 2-year period. We defined traumatic LP as a CSF sample with an RBC count more than 500 cells/mm(3) without xanthochromia.

RESULTS

Rate of traumatic LP was 13.3%. The rate of traumatic LP at the L4-L5 level (19%) was significantly higher than at the L2-L3 (9%) or L3-L4 level (10%). Patients older than 80 years had higher traumatic LP rates (25.9%) compared with patients between ages 11 and 80 years (12.4%). Sex and gauge of the spinal needle were not associated with increased rate of traumatic LP. Patients younger than 1 year had failed LP rate of 58.8% compared with 3.2% failure rate in older patients.

CONCLUSIONS

Fluoroscopy-guided LP at the L4-L5 level is associated with nearly twice the risk for traumatic puncture compared with the L2-L3 or L3-L4 level. Rates of traumatic result are twice as high in adults older than 80 years compared with younger patients. Failure rates for fluoroscopy-guided LP are low except in children younger than 1 year, in whom failure occurs in most cases.

How men with non-chlamydial, non-gonococcal urethritis are managed in Australasia

Summary:

The aim of this study was to ascertain how sexual health physicians in Australia and New Zealand manage men with chlamydia-negative non-gonococcal urethritis (NGU), particularly in relation to the notification of their female sexual partners. In July 2006, a cross-section survey was sent out to all the members of the Australasian Chapter of Sexual Health Medicine. Seventy-three percent of sexual health physicians believed that female partners of men who present with chlamydia-negative NGU were at risk of adverse reproductive health outcomes. At least 62% usually initiated some form of partner notification of female partners of men with chlamydia-negative NGU. However, only 19% (21/111) of sexual health physicians routinely tested for, and only 65% sometimes tested for, pathogens other than Neisseria gonorrhoeae and Chlamydia trachomatis in men presenting with NGU. These included Mycoplasma genitalium, herpes simplex virus, ureaplasma species, Trichomonas vaginalis and adenoviruses.

Sex workers working within a legalised industry: their side of the story

OBJECTIVES

To examine the characteristics and work attitudes of female sex workers working in licensed brothels in Victoria, Australia.

METHODS

This was a cross-sectional study of sex workers working at 38 of the 92 licensed brothels operating in Victoria during 2006.

RESULTS

Of the 108 women approached, 97 (90%) completed the questionnaire. Women working in the legal sex industry in Victoria were generally aged between 23 and 35 years (51%), had completed high school (26%) and had worked in the industry for more than 5 years (43%). Half had dependent children and one third were in a relationship. Women's primary motivation for working in the sex industry was financial, whether this was the reason for their starting (56%), or the barrier to their leaving (61%). Although women valued the higher income and flexibility of this work, many were concerned about sexually transmitted infections (STI) (55%), community attitudes towards the industry (47%), their physical safety (38%) and maintaining their anonymity (37%). Over half of the women would like to leave the industry. The majority (95%) supported the monthly STI checks that are part of the Victorian regulations, with only one fifth reporting that the cost of these tests was prohibitive.

CONCLUSIONS

The findings of this study indicate that women working in licensed Victorian brothels come from a diverse range of backgrounds and circumstances and hold varying attitudes towards working in the sex industry. It is hoped that these findings go some way to redressing the assumptions commonly made about women working in the sex industry and reducing the stigma associated with this occupation.

More than just anal sex: the potential for sexually transmitted infection transmission among men visiting sex-on-premises venues

OBJECTIVES

This study aimed to obtain detailed data on the frequency of sexual practices among men who had sex with men (MSM) at sex-on-premises venues (SOPV) and to compare this with their sexual practices outside SOPV.

METHODS

A cross-sectional survey was undertaken of MSM at six SOPV between December 2006 and March 2007.

RESULTS

Of 604 men approached, 200 (33%) participated. Men reported sexual contact with a median of two other men (range 0-28). Receptive and insertive anal intercourse was reported by 19.5% and 34.0%, respectively, and was unprotected in 2.5% and 6.0%. The frequency of other practices included: unprotected insertive and receptive penile-anal touching or rubbing without penetration, or "nudging" (26.5% and 20.0%); unprotected, transient insertive and receptive anal intercourse, or "dipping" (6.0% and 5.0%) and insertive and receptive anal fingering (38.5% and 32.5%). Approximately 40% of men who reported "nudging" reported that they had not engaged in any "anal sex". Compared with their practices with casual male partners outside SOPV, men having sex at SOPV were less likely to have receptive oral intercourse with ejaculation (odds ratio (OR) 0.4; 95% CI 0.2 to 1.0, p = 0.04) and unprotected receptive anal intercourse (OR 0.3; 95% CI 0.1 to 0.8, p = 0.01), but were more likely to have group sex (OR 2.0; 95% CI 1.1 to 3.6, p = 0.03).

CONCLUSIONS

Substantial penile-anal contact not involving anal intercourse occurred at SOPV and may explain anal infections in the absence of reported anal sex. Some higher risk practices were reported more frequently with male partners outside of these venues than with partners within SOPV.

Oxygen diffusion and consumption in active aerobic granules of heterogeneous structure

The interior structure of aerobic granules is highly heterogeneous, hence, affecting the transport and reaction processes in the granules. The granule structure and the dissolved oxygen profiles were probed at the same granule in the current work for possible estimation of transport and kinetic parameters in the granule. With the tested granules fed by phenol or acetate as carbon source, most inflow oxygen was consumed by an active layer thickness of less than 125 microm on the granule surface. The confocal laser scanning microscopy scans also revealed a surface layer thickness of approximately 100 microm consisting of cells. The diffusivities of oxygen transport and the kinetic constant of oxygen consumption in the active layers only were evaluated. The theoretical models adopted in literature that ignored the contributions of the layered structure of aerobic granule could have overlooked the possible limitations on oxygen transport.

Oxygen diffusion in active layer of aerobic granule with step change in surrounding oxygen levels

High biomass density and large size limit the transfer of dissolved oxygen (DO) in aerobic granules. In the literature, the oxygen diffusivity is often employed as an input parameter for modeling transport processes in aerobic granules. The interior of an aerobic granule was observed to be highly heterogeneous. In this work, the distributions of extracellular polymeric substances (EPS) and cells in the interior of phenol-fed and acetate-fed granules were built up using a five-fold staining scheme, combined with the use of a confocal laser scanning microscope (CLSM). The steady-state and transient DO with step changes in surrounding DO levels at various depths were measured in the granules using microelectrodes. Cells were probed in a surface layer of thickness 125-375 microm. A marked fall in DO was also noted over this surface layer. No aerobic oxidation could occur beneath the active layer, indicating the oxygen transfer limit. Fitting the steady-state and transient DO data over the active surface layer yielded apparent diffusivities of oxygen were (9.5+/-3.5)x10(-10)m(2)s(-1) for the phenol-fed granule and (3.5+/-1.0)x10(-10)m(2)s(-1) for the phenol-fed granule. These values were lower than those adopted in models in the literature.

Life expectancy of patients with newly-diagnosed HIV infection in the era of highly active antiretroviral therapy

BACKGROUND

Limited data are available on the life expectancy of patients with newly-diagnosed HIV infection in the era of highly active antiretroviral therapy (HAART).

AIM

To provide such an estimate using a semi-parametric projection.

DESIGN

Statistical analysis.

METHODS

Follow-up data for patients newly diagnosed with HIV infection in Taiwan (HIV/AIDS Cohort) from 1 May 1997 to 30 April 2003 (n = 3351, only 1% are injecting drug users) were analysed using the Kaplan-Meier method. The survival function for an age- and gender-matched reference population was generated by the Monte Carlo method from the life-table of the general population. A constant excess hazard model was used to project long-term survival of HIV-infected patients, with linear extrapolation of a logit-transformed curve of survival ratio between HIV-infected patients and the reference population.

RESULTS

The 5-year survival rate was 58% in patients who had already developed AIDS at diagnosis (AIDS group), and 89% in those who had not (non-AIDS group). Extrapolation yielded an expected mean survival time of 10.6 years after diagnosis for the AIDS group, and 21.5 years after diagnosis for the non-AIDS group.

DISCUSSION

Our results support the expansion of HIV screening programs to minimize delay in diagnosis. With continuing advances in HAART, this estimate of survival in initially asymptomatic patients may be conservative. Their long life expectancy raises questions about what kind of preventive heath services should be offered. These should be addressed through further analysis of overall benefit and cost-effectiveness.

Distribution of extracellular polymeric substances in aerobic granules

Extracellular matrix provides an architectural structure and mechanical stability for aerobic granules. Distributions of cells and extracellular polymeric substances (EPS), including proteins, alpha- and beta-D-glucopyranose polysaccharides, in acetate-fed granules and phenol-fed granules were probed using a novel quadruple staining scheme. In acetate-fed granules, protein and beta-D-glucopyranose polysaccharides formed the core, whereas, the cells and alpha-D-glucopyranose polysaccharides accumulated in the granule outer layers. Based on these experimental findings, this study indicated that different conclusions can be obtained regarding EPS distributions when granules were stained differently. The core of phenol-fed granules, conversely, was formed principally by proteins; whereas, the cells and alpha- and beta-D-glucopyranose polysaccharides were accumulated at an outer filamentous layer. Using a series of confocal laser scanning microscope (CLSM) images whose threshold values were determined via Otsu's scheme, the three-dimensional distributions of cells and EPS were produced using a polygonal surface model. Structural information extracted can be applied in further development of comprehensive granule models.

A randomised controlled trial comparing computer-assisted with face-to-face sexual history taking in a clinical setting

AIM

To compare computer-assisted self-interview (CASI) with routine face-to-face interview (FTFI) for sexual history taking from patients in a clinical setting.

METHODS

A randomised controlled trial was undertaken at the Melbourne Sexual Health Centre, Melbourne, Victoria, Australia, in 2005. New, walk-in patients triaged into the centre were eligible for the study. Those who consented to the study were randomly allocated (initially at a ratio of 2:1, then 1:1) to either CASI or FTFI. Those randomised to CASI also subsequently undertook FTFI.

RESULTS

During the study period, of 713 patients approached, 611 agreed to participate in the study; 356 were randomised to FTFI and 255 to CASI. Overall, the responses to questioning using CASI and FTFI were similar except that women undertaking the CASI reported a significantly higher median number of male partners for the preceding 12 months (3 v 2, p = 0.05) and the CASI participants reported previous hepatitis B vaccination more often (50% v 37%, p = 0.01). Most participants found the CASI either easy (31; 13%) or very easy (193; 82%) to complete; 83 (35%) were comfortable and 121 (51%) were very comfortable with it.

CONCLUSIONS

CASI may be a reliable, efficient and highly acceptable method for the screening of sexual risk in clinical sexual health settings and could be used routinely to improve the efficiency of clinical services.

Are patient responses to sensitive sexual health questions influenced by the sex of the practitioner?

OBJECTIVE

To determine whether a patient's responses to sensitive questions about their sexual behaviour are influenced by the sex of their treating practitioner.

METHODS

An audit was conducted on the computerised medical records of all patients attending the Melbourne Sexual Health Centre through the walk-in triage system between January 2003 and July 2005. Patient responses to sensitive questions about their sexual behaviour were analysed according to patient group (based upon the sex of their sexual partners) and the sex of the treating practitioner.

RESULTS

There was no significant difference in the reported number of sexual partners, condom use, sex overseas, injecting drug use, or commercial sex work based on the sex of the treating practitioner for the different patient groups. This held true whether clients were homosexual men (n = 1609, p>0.07), heterosexual men (n = 4847, p>0.11), or women (n = 4910, p>0.08).

CONCLUSIONS

The sex of the practitioner did not significantly influence patient responses to sensitive questions about their sexual behaviour.

Diffusivity of oxygen in aerobic granules

This work for the first time estimated apparent oxygen diffusivity (D(app)) of two types of aerobic granules, acetate-fed and phenol-fed, by probing the dissolved oxygen (DO) level at the granule center with a sudden change in the DO of the bulk liquid. With a high enough flow velocity across the granule to minimize the effects of external mass transfer resistance, the diffusivity coefficients of the two types of granules were estimated with reference to a one-dimensional diffusion model. The carbon source has a considerable effect on the granule diameter (d) and the oxygen diffusivity. The diffusivity coefficients were noted 1.24-2.28 x 10(-9) m2/s of 1.28-2.50 mm acetate-fed granules, and 2.50-7.65 x 10(-10) m2/s of 0.42-0.78 mm phenol-fed granules. Oxygen diffusivity declined with decreasing granule diameter, in particular, the diffusivity of acetate-fed granules is proportional to the size, whereas the diffusivity of phenol-fed granules is proportional to the square of granule diameter. The existence of large pores in granule, evidenced by FISH-CLSM imaging, was proposed to correspond to the noted size-dependent oxygen diffusivity. The phenol-fed granules exhibited a higher excellular polymer (ECP) content than the acetate-fed granules, hence yielding a lower oxygen diffusivity.