Oral Antibiotics for Acne.

Oral antibiotics are integral for treating inflammatory acne based on what is understood about the pathogenesis as well as the role of Cutibacterium acnes. However, rising concerns of antibiotic resistance and the perception of "antibiotic phobia" create potential limitations on their integration in an acne treatment regimen. When prescribing oral antibiotics, dermatologists need to consider dosage, duration, and frequency, and to avoid their use as monotherapy. These considerations are important, along with the use of newer strategies and compounds, to reduce adverse-event profiles, antibiotic resistance, and to optimize outcomes. Aside from concomitant medications, allergies, and disease severity, costs and patient demographics can influence variability in prescribing plans. There are multiple published guidelines and consensus statements for the USA and Europe to promote safe antibiotic use by dermatologists. However, there is a lack of head-to-head studies and evidence for comparative superiority of any individual antibiotic, as well as any evidence to support the use of agents other than tetracyclines. Although oral antibiotics are one of the main options for moderate to severe acne, non-antibiotic therapy such as isotretinoin and hormonal therapies should be considered. As newer therapies and more outcomes data emerge, so will improved management of antibiotic therapy to foster patient safety.

Antibiotic Resistance in Acne: Mechanisms, Complications and Management.

Antibiotic resistance in acne was first observed in the 1970s, and since the 1980s has become a major concern in dermatologic daily practice. The mechanisms for this type of resistance include biofilm formation that promotes virulence and the transmission of resistant bacterial strains. Genetic mutations with modification of ribosomal RNA, alteration in efflux pumps, and enzymatic inactivation are able to create resistance to tetracyclines and macrolides. The state of art in acne treatment is no longer to use antimicrobials as monotherapy. There should be a time limit for its use plus the employment of non-antibiotic maintenance. Earlier initiation of oral isotretinoin therapy should be considered in patients with insufficient response to antimicrobials, severe acne, or a history of repeated antimicrobial use. A better understanding of acne pathogenesis, the subtypes of Propionibacterium (also known as Cutibacterium) acnes, homeostasis of the skin microbiota, and the mechanisms of antibiotic resistance would be useful in the selection of narrow-spectrum or species-specific antimicrobials, as well as the non-antimicrobial, anti-inflammatory treatment of acne. A number of novel treatments awaiting clinical proof may include the use of bacteriophages, natural or synthetic antimicrobial peptides, probiotics, and biofilm-targeting agents, as well as the reassessment of phototherapy.

Clonal diversity of Cutibacterium acnes (formerly Propionibacterium acnes) in prosthetic joint infections.

Prosthetic joint infections (PJIs) are rare but feared complications following joint replacement surgery. Cutibacterium acnes is a skin commensal that is best known for its role in acne vulgaris but can also cause invasive infections such as PJIs. Some phylotypes might be associated with specific diseases, and recently, a plasmid was detected that might harbour important virulence genes. In this study, we characterized C. acnes isolates from 63 patients with PJIs (n = 140 isolates) and from the skin of 56 healthy individuals (n = 56 isolates), using molecular methods to determine the phylotype and investigate the presence of the plasmid. Single-locus sequence typing and a polymerase chain reaction designed to detect the plasmid were performed on all 196 isolates. No statistically significant differences in sequence types were seen between the two study groups indicating that the C. acnes that causes PJIs originates from the patients own normal skin microbiota. Of the 27 patients with multiple tissue samples, 19 displayed the same sequence types among all their samples. Single-locus sequence typing identified different genotypes among consecutive C. acnes isolates from four patients with recurrent infections. The plasmid was found among 17 isolates distributed in both groups, indicating that it might not be a marker for virulence regarding PJIs. Patients presenting multiple sequence types in tissue samples may represent contamination or a true polyclonal infection due to C. acnes.

Shiunko and Chuoko, topical Kampo medicines, inhibit the expression of gehA encoding the extracellular lipase in Cutibacterium acnes.

Antimicrobial agents have been used for eradication of Cutibacterium (formerly Propionibacterium) acnes that is an exacerbation factor of the skin disease acne vulgaris. However, the use of antibiotics is associated with an increased risk of promoting the emergence of resistant bacteria and leading to skin dysbiosis. Traditional Japanese Kampo medicines, such as Keigairengyoto, are used to treat acne. However, there is incomplete understanding regarding their functional mechanism in treatment of acne. In this study, we examined the antimicrobial and anti-lipase activity of the Kampo medicines used empirically for acne treatment. Three oral medicines, Keigairengyoto, Seijoboufuto and Jumihaidokuto, were found to inhibit the growth of C. acnes and decrease the lipase activity. Especially, Keigairengyoto caused remarkable decrease of bacterial lipase activity. Furthermore, topical medicines such as Shiunko and Chuoko significantly decreased the lipase activity in a dose-dependent manner, without inhibiting C. acnes growth. The topical medicines were found to inhibit the expression of gehA, which codes for extracellular lipase. Our results indicate that Shiunko and Chuoko have potential as effective acne therapeutic agents, especially because they do not promote the emergence of antimicrobial-resistant bacteria and skin dysbiosis.

Antimicrobial Susceptibility of Cutibacterium acnes Isolated from Ecuadorian Patients with Acne Vulgaris.

Antimicrobial resistance to Cutibacterium acnes has become a worldwide problem in the last century, but there are no previous studies on antibiotic susceptibility patterns of this bacterium in Ecuador. A total of 129 skin swabs were collected from patients with acne vulgaris (AV) attending the dermatology department of a hospital in Quito, Ecuador, from July to August 2015. The patients selected had received registered antimicrobial therapy on at least one occasion before sampling. Microbiological procedures were performed according to conventional methods. The species of isolates were identified using a mass spectrometer system (matrix-assisted laser desorption ionization time-offlight [MALDI-TOF]). Antibiotic susceptibility tests on isolated Cutibacterium were performed using an anaerobe-sensitive panel (ANO2; Thermo Fisher; TREK Diagnostic Systems Ltd., West Sussex, UK).

Characterisation of Cutibacterium acnes phylotypes in acne and in vivo exploratory evaluation of Myrtacine®.

OBJECTIVE: Our main objective was to compare Cutibacterium acnes (C. acnes) skin colonisation in patients with mild to moderate acne versus healthy controls and secondly, to evaluate a Myrtacine® -based cream on C. acnes total population and antibioresistant Cutibacteria in patients with acne. METHODS: In 60 acne patients (Global Acne Severity Scale, GEA grades 2-3), of mean age 20 [15-30] years and in 24 age- and sex- matched healthy controls, forehead strips samplings were performed for microbiological analysis of comedones by colony forming unit (CFU) counts of global C. acnes and erythromycin (EryR) or clindamycin-resistant (ClnR) populations of Cutibacterium and determination of phylotypes by MALTI-TOF. Clinical evaluations of acne patients (GEA, lesion count, porphyrin fluorescence) were performed at baseline and after 56 days of twice-daily application of a Myrtacine® -based cream. RESULTS: We first showed (i) high and similar levels of C. acnes colonisation in superficial pilosebaceous follicles and detection of EryR and ClnR strains in both acne and control groups; (ii) different repartition of phylotypes in acne patients versus healthy control, with a predominance of phylotype IA in acne patients and a link between phylotype IA and erythromycin resistance. Besides, after treatment with the Myrtacine® -based cream in acne patients, there was no change in C. acnes total load, but a significant decrease of EryR Cutibacteria, reduced porphyrin production by C. acnes, a decrease in acne severity (GEA), associated with reduced retentional and inflammatory lesions. CONCLUSION: Cutibacterium acnes colonisation was not significantly different in acne versus control groups. Phylotype IA was predominant in acne patient and in EryR C. acnes. A Myrtacine® -based cream significantly reduced the level of EryR Cutibacteria in vivo and improved acne lesions.

Long-term administration of oral macrolides for acne treatment increases macrolide-resistant Propionibacterium acnes.

Macrolide-resistant Propionibacterium acnes are frequently isolated from patients with acne vulgaris, and the most resistant isolates (>90% resistance) have the 23S rRNA mutation. An increase in resistant P. acnes with this mutation is thought to be caused by the inappropriate use of antimicrobials. Therefore, we studied the mutation frequency of macrolide resistance in P. acnes in vitro. When P. acnes mutants were exposed to clarithromycin after being incubated in broth without antimicrobials, resistant mutants with the 23S rRNA mutation were not isolated. However, the mutants were obtained at the frequency of 10-6 after being pre-incubated with 0.03 µg/mL of antimicrobials. This is the estimated epidermal concentration of clarithromycin after p.o. administration. The resistant mutants had the 23S rRNA mutations A2058G, A2059G and C2611G. When pre-incubated with clarithromycin, C2611G mutants which showed resistance to clarithromycin were obtained 32.1% more often than pre-incubated with clindamycin (P < 0.01). By contrast, when pre-incubated with clindamycin, A2058G mutants, which show high-level resistance to both clarithromycin and clindamycin, were more frequently obtained than pre-incubated with clarithromycin (87.5%, P < 0.01). No difference in the isolation rate of A2059G mutants, which show high-level resistance to macrolides but low-level resistance to clindamycin, was found with either treatment. These results indicate the possibility that long-term use of oral macrolides for acne treatment facilitate the increase of macrolide-resistant P. acnes.

Activity of Electrical Current in Experimental Propionibacterium acnes Foreign-Body Osteomyelitis.

Foreign-body-associated infections are often difficult to treat, given that the associated microorganisms are in a biofilm state. Previously, we showed that a low-amperage direct electrical current (DC) reduces Propionibacterium acnes biofilms formed on implant-associated materials in vitro In this study, low-amperage DC was compared to ceftriaxone treatment or no treatment in a novel rat femur model of foreign-body osteomyelitis. A platinum implant seeded with a P. acnes biofilm (107 CFU/cm2) and 109 CFU of planktonic P. acnes was placed in the femoral medullary cavity. One week later, rats were assigned to one of three treatment groups: no treatment, ceftriaxone treatment, or 200-µA-DC treatment. After 2 weeks of treatment, there were fewer bacteria in the bones of the ceftriaxone group (3.06 log10 CFU/g of bone [P = 0.0209]) and the 200-µA-DC group (0.5 log10 CFU/g [P = 0.0015]) than in those of the control group (6.58 log10 CFU/g). The DC-exposed animals exhibited fewer bacteria than the ceftriaxone-treated animals (P = 0.0330). There were fewer bacteria on the implanted wires in the groups treated with ceftriaxone (0.1 log10 CFU/cm2) or a 200-µA DC (0.1 log10 CFU/cm2) than in the control group (2.53 log10 CFU/cm2 [P, 0.0003 for both comparisons]). Low-amperage DC may be useful for treating, or aiding in the treatment of, foreign-body infections caused by P. acnes.

Staphylococcus aureus carriage rates and antibiotic resistance patterns in patients with acne vulgaris.

BACKGROUND: Overuse of antibiotics has led to the development of antibiotic-resistant strains of Staphylococcus aureus, which are occurring more frequently within the community. OBJECTIVE: We sought to determine whether long-term antibiotic therapy for acne alter the carriage rate and antibiotic resistance profiles of S aureus. METHODS: This was a prospective, cross-sectional, quasiexperimental study. Samples of anterior nares were obtained from dermatology patients given a diagnosis of acne vulgaris (n = 263) who were treated with antibiotics (n = 142) or who were not treated with antibiotics (n = 121). Specimens were tested for the presence of S aureus by growth on mannitol salt agar and then isolated on 5% sheep blood agar. Identification was confirmed based on colonial morphology, Gram stain, catalase, and coagulase testing. Antibiotic susceptibility testing was performed using the VITEK 2 system (bioMerieux, Marcy-l'Étoile, France). RESULTS: The S aureus carriage rate was significantly lower in patients with acne treated with antibiotics (6.3%) compared with those not treated with antibiotics (15.7%; P = .016). The percentage of S aureus isolates resistant to 1 or more antibiotics did not significantly differ between the 2 groups (P = .434). LIMITATIONS: Cross-sectional study, patient compliance, and effects of prior acne treatments are limitations. CONCLUSION: Treatment of patients with acne using antibiotics decreases the S aureus carriage rate but does not significantly alter the antibiotic resistance rates.

Optimization of periprosthetic culture for diagnosis of Propionibacterium acnes prosthetic joint infection.

Propionibacterium acnes is increasingly recognized as an important agent of prosthetic joint infection (PJI). However, the optimum culture conditions for recovery of this organism from PJI specimens have not been determined. By applying a prolonged 28-day culture incubation to all periprosthetic specimens received for bacterial culture from 198 revision arthroplasty procedures, we retrospectively determined that a 13-day culture incubation period is necessary for the recovery of P. acnes from patients with PJI. Incubation beyond this period was associated with increasing recovery of nondiagnostic isolates: 21.7% of P. acnes isolates believed to be clinically unimportant were recovered after 13 days of incubation. Importantly, a diagnosis of P. acnes PJI would have been missed in 29.4% of patients had extended culture incubation been applied only to anaerobic culture media. Although specimens from P. acnes PJIs were more commonly associated with the presence of ≥ 2 culture media positive for growth, acute inflammation (≥ 5 neutrophils/high-power field) was observed in only 40% of patients with PJIs that had more than one specimen submitted for bacterial culture. These results support the need for a minimum culture incubation period of 13 days to be applied to both aerobic and anaerobic culture media for all periprosthetic specimens. Optimal recovery of infecting organisms from PJI specimens will be an important component in generating a universal definition for PJI due to indolent agents of infection, such as P. acnes.

In vivo antimicrobial effects of endodontic treatment procedures as assessed by molecular microbiologic techniques.

INTRODUCTION: This culture-independent molecular microbiology study evaluated the antimicrobial effects of chemomechanical preparation supplemented by intracanal medication during treatment of teeth with apical periodontitis. METHODS: Samples were taken from 24 necrotic root canals at the baseline (S1), after chemomechanical preparation by using 2.5% NaOCl as the irrigant (S2), and after a 7-day interappointment medication with calcium hydroxide paste in either glycerin (CHG) or camphorated paramonochlorophenol/glycerin (CHPG) (S3). Bacterial, archaeal, and fungal presence was evaluated by polymerase chain reaction (PCR), and bacterial identifications were performed by a closed-ended reverse-capture checkerboard approach targeting 28 candidate endodontic pathogens. RESULTS: All S1 samples were positive for bacteria but negative for both archaea and fungi. Treatment procedures were highly effective in reducing the bacterial levels and number of taxa. Overall, 46% of S2 samples and 62.5% of S3 samples were PCR-negative for bacteria. Specifically, S2 and S3 samples yielded negative PCR results in 50% and 58% of the canals in the CHG group and in 42% and 67% of the canals in the CHPG group, respectively. Except for comparisons with S1 samples, no other statistically significant differences were observed for intragroup and intergroup comparisons involving S2 and S3. Several taxa were still found in S2 and S3 samples, and the most prevalent were Propionibacterium acnes and Streptococcus species. CONCLUSIONS: Bacterial levels and number of taxa were substantially reduced after chemomechanical preparation and intracanal medication. However, presence of detectable levels of persisting bacteria in many cases indicates that the search for more effective antimicrobial treatment strategies should be stimulated.

In vitro antimicrobial susceptibility of Propionibacterium acnes isolated from acne patients in northern Mexico.

BACKGROUND: Antimicrobials are essential in acne therapy. In the last decades, Propionibacterium acnes has become resistant to different antibiotics. OBJECTIVE: To determine antimicrobial susceptibility patterns of P. acnes to frequently used drugs. MATERIALS AND METHODS: Cutaneous lesion samples were obtained from 50 patients with acne vulgaris, which were cultured in anaerobic media to demonstrate the presence of P. acnes. After that, antimicrobial susceptibility tests to tetracycline, minocycline, doxycycline, erythromycin, azithromycin, clindamycin, trimethoprim/sulfamethoxazole (SXT) and levofloxacin were performed. RESULTS: In the general study group, resistance to azithromycin was 82%, the most prevalent one (P < 0.05), followed by trimethoprim/sulfamethoxazole (68%) and erythromycin (46%). On the other hand, all strains isolated were susceptible to minocycline. Resistance bias were similar when subgroups with and without the previous antimicrobial therapy were performed, finding a low prevalence of resistance to tetracyclines and levofloxacin in both groups. CONCLUSIONS: In our region, P. acnes is highly resistant to azithromycin, SXT, erythromycin and clindamycin; and being very susceptible to minocycline, levofloxacin and tetracycline, in vitro in both groups: with and without the previous antibiotic use. To our knowledge, high resistance prevalence to azithromycin and SXT has never been reported.

Antibacterial activity of Thai herbal extracts on acne involved microorganism.

Ethyl acetate and methanol extracts of 18 Thai medicinal plants were investigated for their antibacterial activity against Propionibacterium acnes, Stapylococcus aureus, and S. epidermidis. Thirteen plant extracts were capable of inhibiting the growth of P. acnes and S. epidermidis, while 14 plant extracts exhibited an inhibitory effect on S. aureus. Based on the broth dilution method, the ethyl acetate extract of Alpinia galanga (L.) Wild. (Zingiberaceae) rhizome showed the strongest antibacterial effect against P. acnes, with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 156.0 and 312.0 microg/mL, respectively. On the basis of bioassay-guided purification, the ethyl acetate extract was isolated to afford the antibacterial active compound, which was identified as 1'-acetoxychavicol acetate (1'-ACA). 1'-ACA had a strong inhibitory effect on P. acnes with MIC and MBC values of 62.0 and 250.0 microg/mL, respectively. Thus, 1'-ACA was used as an indicative marker for standardization of A. galanga extract using high performance liquid chromatography. These results suggest that A. galanga extract could be an interesting agent for further studies on an alternative treatment of acne.

In vitro activities of azole antifungal agents against Propionibacterium acnes isolated from patients with acne vulgaris.

The Gram-positive bacterium Propionibacterium acnes is the causative agent of acne vulgaris. Antibiotics such as tetracycline and macrolide derivatives are used to treat this skin disease; however, the isolation frequency of antibiotic-resistant P. acnes has been increasing. The anti-P. acnes activity of imidazole antifungal agents was reported more than 20 years ago, and since then, new azole antifungal agents have been marketed. Thus, this study determined the in vitro activities of azole antifungal agents against P. acnes isolated from patients with acne vulgaris. Of the five agents tested, miconazole, ketoconazole, and itraconazole showed concentration-dependent anti-P. acnes activity, including against antibiotic-resistant isolates. Time-kill assay also showed the time-dependent activity of the drugs. Fluconazole and voriconazole showed no anti-P. acnes activity.

Assessment of the bacterial diversity of human colostrum and screening of staphylococcal and enterococcal populations for potential virulence factors.

In contrast to breast milk, little is known about the bacterial composition of human colostrum. The objective of this work was to analyze the bacterial diversity of colostrum obtained from healthy women and to characterize the dominant bacterial species for the presence of possible virulence factors. Samples of colostrum obtained from 36 healthy women were inoculated into different culture media. Several isolates from each medium were selected and identified. Staphylococcal and enterococcal isolates were submitted to genetic profiling. One representative of each profile was included in a genetic and phenotypic characterization scheme, including detection of potential virulence traits/genes and sensitivity to antibiotics. Staphylococcus epidermidis and Enterococcus faecalis were the dominant species, followed by Streptococcus mitis, Propionibacterium acnes and Staphylococcus lugdunensis. Among the 48 S. epidermidis isolates selected on the basis of their genetic profiles, the biofilm-related icaD gene and the mecA gene were detected in only 11 and six isolates, respectively. In parallel, 10 enterococcal isolates were also characterized and none of them contained the cylA, vanA, vanB, vanD, vanE and vanG genes. All of them were sensitive to vancomycin. There were no indications that the colostrum samples contained harmful bacteria.

An assessment of the efficacy of blue light phototherapy in the treatment of acne vulgaris.

BACKGROUND: Acne vulgaris is a common skin condition that affects 8 out of 10 people. It varies from mild to severe, and different treatments target various aspects of the disease. Propionibacterium acnes, one of the culprits involved in the pathogenesis of acne vulgaris, is the main target of all major medical treatments used. Studies conducted in recent years have shown favorable effects within the visible light spectrum for the treatment of acne vulgaris. OBJECTIVE: In this study, we have evaluated the use of intense blue light within the spectral range of 415-425 nm (peak 420 nm) in the treatment of acne vulgaris. METHODS: Twenty-one patients with mild to moderate facial acne were treated with blue light phototherapy. All patients were given 14-min treatment sessions twice a week for 4 weeks. Acne severity was assessed using the Leeds Technique for grading and lesion counts. Disability was assessed using the Dermatology Life Quality Index (DLQI). In addition, standard digital and cross-polarized light photographs were taken and graded by a blinded evaluator. Visual analog scale (VAS) scores and cultures for P. acnes were carried out before starting the treatment and upon completion of the treatment. RESULTS: Significant improvement was achieved in the Leeds Acne Grade (P = 0.001). The inflammatory (P = 0.001) and noninflammatory (P = 0.06) lesion counts also improved significantly. A similar change was noted in the DLQI (P = 0.001); a degree of significance was also achieved in the patients' and the investigators' VAS scores (P = 0.01 and P = 0.001, respectively). P. acnes colony counts failed to show a significant decrease at the end of the treatment and remained almost constant (P = 0.660). CONCLUSIONS: We believe that blue light does appear to have some role in the management of acne and may be beneficial for the treatment of a select group of mild to moderate acne patients.

Propionibacterium acnes postoperative shoulder arthritis: an emerging clinical entity.

The purpose of this study, which involved 276 patients, was to report the importance of Propionibacterium acnes in shoulder infections. The proportion of patients with shoulder infection who had infection due to P. acnes was significantly greater than the proportion of patients with lower limb infection who had infection due to P. acnes (9 of 16 patients vs. 1 of 233 patients; P < .001). This bacterium requires a prolonged incubation period and should not be considered to be a contaminant.

Biofilm formation of the pathogens of fatal bacterial granuloma after trauma: potential mechanism underlying the failure of traditional antibiotic treatments.

The pathogen of a new type of disease - fatal bacterial granuloma after trauma (FBGT) - was found to be Propionibacterium acnes (P. acnes). Although in vitro studies showed that the pathogenic P. acnes are sensitive to conventional antibiotics, treatments of FBGT patients with these antibiotics were ineffective. The underlying mechanisms were not clear. Since P. acnes are able to form biofilm on orthopaedic biomaterials in vitro, and pathogenic P. acnes of acnes vulgaris was known to form biofilm in vivo, we hypothesize that the pathogens of FBGT are also able to form biofilm during the pathogenesis, which may be 1 of the reasons for antibiotics tolerance of FBGT. Biofilm forming capacity of the pathogens of FBGT were examined with XTT reduction method, as well as with scanning electron microscope. The effect of long-term subminimal inhibitory concentration (MIC) lincomycin on the biofilm forming ability of the pathogens was also tested. Our results show that both the type strain (NCTC737) and the pathogenic P. acnes of FBGT can form biofilm in vitro. These data demonstrated the biofilm formation of the FBGT pathogens in vitro, and its acceleration by lincomycin, which may be 1 of the major mechanisms for the failure of antibiotic treatment.

Association between the presence of bacterial 16S RNA in prostate specimens taken during transurethral resection of prostate and subsequent risk of prostate cancer (Sweden).

OBJECTIVE: To study bacterial 16S RNA in archival prostate samples from 352 patients with benign prostate hyperplasia (BPH) and evaluate whether the presence of bacterial DNA was different in those who later developed prostate cancer (n = 171) and in the matched controls that did not progress to cancer (n = 181). METHODS: 16S DNA PCR followed by cloning and sequencing the positive samples. RESULTS: In 96/352 (27%) of the prostate tissue specimens 16S RNA were detected. Sequence analysis revealed Propionibacterium acnes as the predominant microorganism (23% of 16S RNA positive patients). The second most frequent isolate-Escherichia coli was found in 12 (12%) patients. The other isolates included Pseudomonas sp. (3 patients), Actinomyces sp. (2), Streptococcus mutans (1), Corynebacterium sp. (2), Nocardioides sp. (1), Rhodococcus sp. (1) Veillonella sp. (2). In P. acnes positive samples 62% exhibited severe histological inflammation versus 50% in the bacteria-negative group (p = 0.602). The presence of P. acnes in the prostate was associated with prostate cancer development (OR 2.17, 95% CI 0.77-6.95). CONCLUSIONS: This study has revealed P. acnes as the most common bacteria in the prostate in BPH. Further studies are needed to clarify its role in contributing to the development of prostatic inflammation and prostate cancer.

Outbreak of postoperative shoulder arthritis due to Propionibacterium acnes infection in nondebilitated patients.

We investigated an outbreak of postoperative shoulder arthritis due to Propionibacterium acnes infection in nondebilitated patients. Risk factors were male sex, the order in which surgery was performed during the daily operating schedule, and increased duration of the surgical procedure. After modification of the ventilation system and implementation of improved cleaning methods in the operating theater, no new cases were recorded.