Methicillin-Resistant Staphylococus aureus

Microbiology of acute bacterial dacryocystitis: a tertiary institutional experience in South Australia

PURPOSE

To provide a comprehensive microbiological profile of bacterial dacryocystitis in South Australia. By identifying the specific microorganism and antibiotic susceptibility, this study intends to aid ophthalmologists in choosing appropriate empirical antibiotic therapies and development of evidence-based clinical guidelines.

METHOD

A retrospective study was conducted at the Royal Adelaide Hospital (RAH) over five years (2018-2023) of patients with acute dacryocystitis. The study included 43 patients, and data encompassed demographic information, clinical presentation, microbiological analysis, management, and outcomes. Patients with chronic dacryocystitis were excluded.

RESULTS

Among the 43 patients included in the study (female 28 (65%), mean age: 64 years old), the most common clinical features were pain (74%) and swelling (70%). Organisms were identified in 49% of patients, with the predominant bacteria being Staphylococcus aureus (42%), Streptococcus species (19%), and Escherichia coli (8%). Aggregatibacter species (8%), Morganella morganii (4%), Enterobacter cloaceae (4%), Hafnia alvei (4%), mixed anaerobes (4%), E coliforms (4%) and Pseudomonas aeruginosa (4%) were also identified. The most frequently prescribed empirical antibiotics were amoxicillin-clavulanic acid (50%), flucloxacillin (33%) and cefalexin (18%).

CONCLUSION

The microbiological trends of acute dacryocystitis have largely remained consistent, with a predominance of Gram positive organisms. This is the most recent profile analysis of acute dacryocystitis in South Australia and will help form evidence-based clinical guidelines.

Methicillin-resistant Staphylococcus aureus-associated orbital cellulitis: a case series

PURPOSE

In recent years, methicillin-resistant Staphylococcus aureus (MRSA) orbital cellulitis (OC) has drawn increasing clinical and public health concern. We present a case series of MRSA OC encountered at four Australian tertiary institutions.

METHODS

A multi-centre retrospective case series investigating MRSA OC in Australia from 2013 to 2022. Patients of all ages were included.

RESULTS

Nine cases of culture-positive non-multi-resistant MRSA (nmMRSA) OC were identified at four tertiary institutions across Australia (7 male, 2 female). Mean age was 17.1 ± 16.7 years (range 13-days to 53-years), of which one was 13 days old, and all were immunocompetent. Eight (88.9%) patients had paranasal sinus disease, and seven (77.8%) had a subperiosteal abscess. Four (44.4%) had intracranial extension, including one (11.1%) case which was also complicated by superior sagittal sinus thrombosis. Empirical antibiotics, such as intravenous (IV) cefotaxime alone or IV ceftriaxone and flucloxacillin, were commenced. Following identification of nmMRSA, targeted therapy consisting of vancomycin and/or clindamycin was added. Nine (100%) patients underwent surgical intervention. Average hospital admission was 13.7 ± 6.9 days (range 3-25 days), with two patients requiring intensive care unit (ICU) admission due to complications related to their orbital infection. All patients had favourable prognosis, with preserved visual acuity and extraocular movements, following an average follow-up period of 4.6 months (range 2-9 months).

CONCLUSION

NMMRSA OC can follow an aggressive clinical course causing severe orbital and intracranial complications across a wide demographic. However, early recognition, initiation of targeted antibiotics and surgical intervention when required can effectively manage these complications and achieve favourable visual outcomes.

Microbiology of bacterial orbital cellulitis-tertiary institutional experiences in South Australia: a multi-centre retrospective study

PURPOSE

This study describes the microbiology of bacterial orbital cellulitis (OC) over an 11-year period and its clinical associations at three tertiary institutions in Adelaide, South Australia.

METHODS

Multi-centre retrospective study of the microbiology of bacterial OC between January 2012 and August 2022. Pre-septal cellulitis was excluded. Differences in means were determined by the Independent Samples t-test, and categorical data was analysed via Pearson's Chi square. A P-value < 0.05 was statistically significant.

RESULTS

99 patients (male: 69, mean age: 22.0 ± 23.8 years old), of which 70.7% were aged ≤ 18 years. Sinus and orbital abscess cultures had the greatest positive yield (73.7%). Frequency of organisms: Streptococcus species (34.3%), Staphylococcus aureus (28.3%), Haemophilus species (5.1%), mixed anaerobes (3.0%), Enterobacter cloacae (2.0%), Moraxella catarrhalis (1.0%), Pseudomonas aeruginosa (1.0%), Corynebacterium species (1.0%), Klebsiella pneumoniae (1.0%), Proteus mirabilis (1.0%), Citrobacter koseri (1.0%), and Enterococcus species (1.0%). Streptococcus species predominated in the paediatric population, with a statistically significant difference in mean age between Streptococcus species and Staphylococcus aureus (14.1 ± 16.5 vs 27.6 ± 24.6 years old, respectively) (P = 0.028). No organism was cultured in 32.3% of cases. Methicillin-resistant Staphylococcus aureus (MRSA) accounted for 28.6% of all Staphylococcus aureus isolates, with 50% occurring between 2021 and 2022.

CONCLUSION

Yearly microbiological trends have remained largely constant in South Australia. The causative organism was not identified in 32.3% of cases, further emphasising appropriate empirical antibiotics, and obtaining microbiology from various sources. MRSA OC remains of increased clinical and public health concern and may be associated with a more aggressive disease course.

A 10-Year Review of Ocular Methicillin-Resistant Staphylococcus aureus Infections: Epidemiology, Clinical Features, and Treatment

PURPOSE

To characterize epidemiological data on methicillin-resistant Staphylococcus aureus (MRSA) ocular infections over a 10-year period in Hong Kong; to compare the characteristics between hospital-associated methicillin-resistant Staphylococcus aureus (h-MRSA) and community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) ocular infections; and to review the treatment regimen and outcome of identified cases.

METHODS

A retrospective case review of ocular samples testing positive for MRSA at a tertiary eye center from July 2005 to June 2015 was performed.

RESULTS

Ninety nonduplicative samples from 75 patients with ocular MRSA infection were included during the study period. The average annual rate of ocular MRSA infection among all ocular S. aureus infections was 12.9%. Ten patients had CA-MRSA (13.3%). The most common clinical manifestation was preseptal cellulitis in the CA-MRSA group and blepharoconjunctivitis in the h-MRSA group. Vision-threatening conditions occurred only in the h-MRSA group. Besides vancomycin, other antibiotics to which both MRSA groups were highly sensitive included chloramphenicol, fusidic acid, cotrimoxazole, and gentamicin. Significantly more CA-MRSA was sensitive to levofloxacin and clindamycin (P < 0.01). The h-MRSA group required a significantly longer duration of treatment to eradicate infection (mean 79 vs. 28 days, P < 0.01).

CONCLUSIONS

CA-MRSA presents as a genetically different organism with distinctive clinical presentation and antibiotic sensitivity from its h-MRSA counterpart. Despite increasing resistance patterns, we demonstrate that MRSA ocular infections can be effectively treated without the use of vancomycin, limiting its use to refractory or vision-threatening conditions.