The first nationwide surveillance of antibacterial susceptibility patterns of pathogens isolated from skin and soft-tissue infections in dermatology departments in Japan

Significant increase in the prevalence of Panton-Valentine leukocidin-positive methicillin-resistant Staphylococcus aureus, particularly the USA300 variant ΨUSA300, in the Japanese community

IMPORTANCE

USA300 is an MRSA clone producing PVL, a toxin associated with SSTIs. ΨUSA300 is a USA300 variant recently identified in Japan by Takadama et al. (15). Here, we found that the prevalence rate of PVL-positive MRSA in S. aureus was elevated in the Japanese community, and ΨUSA300 accounted for most of them. ΨUSA300 strains have been isolated from several areas in Japan and were associated with deep-seated SSTIs. This study highlighted the emerging threat posed by ΨUSA300 in Japan.

Impact of Antimicrobial Drug-Drug Interactions on Acute Kidney Injury after Allogeneic Hematopoietic Cell Transplantation

Acute kidney injury (AKI) is one of the major complications after allogeneic hematopoietic stem cell transplantation (allo-HSCT). The use of multiple antimicrobials is one of the major causes of post-transplantation AKI, owing to the potential nephrotoxicity of each agent and of drug-drug interactions (DDIs). No satisfactory reports on DDIs the field of allo-HSCT have been published. We performed a retrospective analysis to compare the incidence of AKI within 100 days post-transplantation. A total of 465 allo-HSCTs in 416 patients were analyzed, and the cumulative incidence of AKI was 40.0%. AKI was associated with significantly reduced overall survival (hazard ratio [HR], 2.66; 95% confidence interval [CI] 1.95 to 3.55; P < .01) and increased transplantation-related mortality (HR, 4.77, 95% CI, 2.90 to 7.88; P < .01). A higher incidence of AKI was significantly associated with the use of ciprofloxacin, cefepime, tazobactam/piperacillin, meropenem, vancomycin, liposomal amphotericin B, ganciclovir, and foscarnet. Among these drugs, combinations of vancomycin plus tazobactam/piperacillin (HR, 2.23; P = .09 for interaction), ganciclovir plus cefepime (HR, 5.93; P = .04), and ganciclovir plus meropenem (HR, 2.63; P = .12) synergistically increased the risk of AKI, whereas combinations involving teicoplanin did not. This is the first report dealing with DDIs after allo-HSCT, indicating that such combinations should be avoided to preserve renal function and reduce AKI-related morbidity and mortality.

Prevalence and clinical characteristics of methicillin-resistant Staphylococcus aureus infections among dermatology inpatients: A 7-year retrospective study at a tertiary care center in southwest China

Background

Increased rates of methicillin-resistant Staphylococcus aureus (MRSA) antibiotic resistance and the associated morbidity have increased dermatologists' attention to skin and soft tissue MRSA infections. However, the clinical characterization of MRSA skin and soft tissue infections (SSTIs) in Southwest China is lacking, which precludes optimal prevention and treatment of these infections.

Objectives

This study was conducted to characterize the prevalence, clinical comorbidities and antibiotic susceptibility of MRSA isolates from SSTIs, including community-associated (CA) and healthcare-associated (HA) isolates.

Methods

In the Dermatology Inpatient Department of the First Affiliated Hospital of Guangxi Medical University, a retrospective study was conducted on data, including patient demographics and clinical information, from culture-confirmed S. aureus isolated from skin and soft tissue between January 1, 2015, and December 31, 2021. Isolate susceptibility to 13 antibiotics was determined using the Vitek 2 system.

Results

From among 864 S. aureus strains, we identified 283 MRSA (32.75%) isolates comprising 203 CA-MRSA and 80 HA-MRSA isolates. The average rate of CA-MRSA isolation for MRSA SSTIs was 71.73%. The HA-MRSA isolation rate for MRSA SSTIs increased significantly. HA-MRSA-infected patients were older. The most common dermatological presentation of CA-MRSA infection was staphylococcal scalded skin syndrome, while the comorbidity severe drug eruption was significantly associated with HA-MRSA infection. One CA-MRSA strain was resistant to linezolid, and one HA-MRSA strain had an intermediate phenotype for vancomycin; both strains had low sensitivity to clindamycin and erythromycin (3.70%~19.40%). However, HA-MRSA isolates were more susceptible to trimethoprim/sulfamethoxazole.

Conclusions

CA-MRSA is a predominant pathogen causing SSTIs, and HA-MRSA infection incidence is increasing gradually. Both strains showed increasing antibiotic resistance. Our data on MRSA susceptibility may guide dermatologist antibiotic treatment decisions. Dermatologists should consider these identified comorbidities of MRSA SSTIs when patients are admitted and initiate early prevention and treatment of MRSA.

The second nationwide surveillance of antibacterial susceptibility patterns of pathogens isolated from skin and soft-tissue infections in dermatology departments in Japan

The present study compared trends in antimicrobial resistance patterns in pathogens isolated from skin and soft-tissue infections (SSTIs) in Japan with those of a nationwide survey conducted in 2013. Three organisms that caused most of the SSTIs were collected from 12 dermatology departments in medical centers and 12 dermatology clinics across Japan between April 2019 and August 2020. A total of 390 strains, including 267 Staphylococcus aureus, 109 coagulase-negative staphylococci (CNS), and 14 Streptococcus pyogenes strains were submitted to a central laboratory for antimicrobial susceptibility testing. Patient demographic and clinical information was collated. Methicillin-resistant S. aureus (MRSA) was detected in 25.8% (69/267) of the S. aureus strains. The prevalence of MRSA between the present study and the 2013 survey did not differ significantly. Furthermore, there were no significant differences in MIC values and susceptibility patterns of the MRSA strains to other agents, regardless of a history of hospitalization within 1 year or invasive medical procedures. Methicillin-resistant CNS (MRCNS) was detected in 48.6% (53/109) of CNS isolates, higher than the 35.4% prevalence in the 2013 survey. This difference could be attributed to the heterogeneity in the members of the MRCNS, which comprises multiple staphylococci species, between the 2013 and 2019 surveys. However, it was noted that the susceptibility profiles of the MRCNS to each antibiotic were not significantly different from those identified in the 2013 survey. Most strains of S. pyogenes were susceptible to each antibiotic, similar to the 2013 survey. Continuous monitoring of trends in pathogen and susceptibility profiles is important to advise local public health efforts regarding the appropriate treatment of SSTIs.

Antimicrobial activity of ozenoxacin and other antimicrobials against Staphylococcus aureus strains isolated from clinical skin specimens in Japan in 2019 and 2020

Skin infections caused by methicillin-resistant Staphylococcus aureus (MRSA) and the spread of antimicrobial resistance are a major problem in Japan. Here, we investigated the susceptibility of S. aureus clinical isolates to ozenoxacin (OZNX), a topical antimicrobial approved for superficial skin infection treatment in Japan. Susceptibility to OZNX was measured in 110 skin-derived methicillin-susceptible S. aureus (MSSA) and 130 MRSA strains isolated in 2019 and 2020 in Japan. The broth microdilution method was performed, and results were analyzed according to the Clinical and Laboratory Standard Institute (M07 and M100) guidelines. The results were compared with those of other antimicrobials used against S. aureus. The minimum inhibitory concentrations (MIC)90 of OZNX for MSSA and MRSA were 0.12 and 0.25 μg/mL, respectively, indicating that OZNX exhibited the same or stronger antibacterial activity than that of the other antimicrobials tested, such as nadifloxacin, fucidic acid, and gentamicin. No strains exhibited reduced OZNX susceptibility. Notably, a low MIC of OZNX was observed even for strains with reduced susceptibility to nadifloxacin, a similar quinolone-based topical antimicrobial. OZNX is a highly potent antimicrobial used in Japan for superficial skin infections caused by S. aureus, such as impetigo contagiosa and related diseases.

The Risk of Emerging Resistance to Trimethoprim/Sulfamethoxazole in Staphylococcus aureus

Objective

Due to the spread of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA), the demand for trimethoprim/sulfamethoxazole (SXT) is increasing in the world. It is not clear whether the resistant strain emerges by overuse of SXT. We investigated here the emergent risk of the SXT-resistant mutant in S. aureus by an in vitro SXT exposure experiment.

Methods

A total of 40 S. aureus clinical isolates (20 MSSA and 20 MRSA isolates) were exposed to sub-MIC of SXT for consecutive days, and MIC of SXT was determined every day. In addition, the dfrB DNA sequencing was performed to detect the mutation in the SXT-resistant strain.

Results

The SXT-resistant strain began to emerge on the eighth day and accounted for 45% (18/40 clinical isolates) after 14 days. Moreover, one half of these resistant strains showed F98Y mutation in DfrB to retain SXT-resistance without selective pressure.

Conclusion

The emergent risk was SXT exposure of 14 days or more.

Persistent methicillin-resistant Staphylococcus aureus bacteremia in an adult patient with Netherton's syndrome: A case report

Netherton's syndrome, a rare congenital disorder, is clinically characterized by chronic dermatologic disorders such as ichthyosiform erythroderma and ichthyosis linearis circumflexa. Curable treatment is yet to be established, and corticosteroid ointment is required to maintain good dermatological condition. Because of the permanent skin barrier impairment, patients with Netherton's syndrome are considered to be vulnerable to cutaneous infections. However, its clinical characteristics are yet to be elucidated due to the limited number of reported cases. Herein, we describe the clinical course of a patient who developed persistent methicillin-resistant Staphylococcus aureus (MRSA) bacteremia. A 19-year-old Japanese woman who had been diagnosed with Netherton's syndrome in her infancy and had been applying topical corticosteroid agents all over her body since her then, was referred to our hospital because of persistent MRSA bacteremia and secondary adrenal insufficiency. The patient was diagnosed with a central line-associated bloodstream infection and was appropriately treated with antibiotics and corticosteroid therapies. We assume that the damaged skin barrier due to the congenital dermatological disorder causes a disruption in the normal bacterial flora of the skin, leading to the invasion of harmful bacteria, such as S. aureus. In addition, internal (humoral immunodeficiency by decreased antibody against bacterial polysaccharide antigens) and external (prolonged and systemic use of corticosteroid ointment) factors bring about an immunodeficiency state in such patients. We highlight that in the absence of radical treatment, clinicians need to recognize that patients with Netherton's syndrome are vulnerable to bacterial infections owing to the mixture of immunosuppressive factors.

Efficacy and safety of daptomycin in Japanese pediatric participants with complicated skin and soft tissue infections or bacteremia caused by gram-positive cocci

INTRODUCTION

Complicated skin and soft tissue infections (cSSTIs) and bacteremia caused by Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), are common causes of infection for children worldwide. Here, the safety and efficacy of daptomycin in Japanese pediatric participants are reported.

METHODS

This open-label, single-arm phase 2 study (NCT03643952) enrolled Japanese pediatric participants (age 1-17 years) with cSSTI or bacteremia caused by gram-positive cocci. Participants received age-adjusted doses of intravenous daptomycin for 5 to up to 14 days (cSSTI) or 5 to up to 42 days (bacteremia). The primary objective was safety and tolerability; efficacy among participants with infections caused by MRSA was a secondary objective.

RESULTS

A total of 18 participants (cSSTI, n = 14; bacteremia, n = 4) were enrolled across 12 study sites in Japan. The most common pathogen was S. aureus (15/18 [83.3%]), including methicillin-susceptible and -resistant isolates. Adverse events (AE) were reported in 42.9% (6/14) of participants with cSSTI and 100% (4/4) of participants with bacteremia. No deaths, serious AEs, discontinuations of study medication due to an AE, or events of clinical interest occurred in the study. In participants with infections caused by MRSA, 87.5% [7/8] achieved favorable clinical response at test of cure (TOC) visit (cSSTI, 85.7% [6/7]; bacteremia, 100% [1/1]). In this population, favorable microbiological response at TOC was achieved by 71.4% (5/7) of participants with cSSTI and 100% (1/1) of participants with bacteremia.

CONCLUSIONS

Daptomycin was well tolerated, exhibited a favorable safety profile, and was effective for the treatment of cSSTI or bacteremia in Japanese children.

Infective Endocarditis from Furuncle with Meningitis Complication Caused by Methicillin-resistant Staphylococcus aureus

Infective endocarditis (IE) may be acquired in the community as community-acquired (CA) IE or in the healthcare setting. In Japan, cases of CA-methicillin-resistant Staphylococcus aureus (MRSA) infection as skin infection have been increasing. CA-MRSA strains, including the USA300 clone, have higher pathogenicity and are more destructive to tissue than healthcare-associated MRSA strains because of the toxins they produce, including arginine-catabolic mobile element (ACME) and Panton-Valentine leukocidin (PVL). However, only a few IE cases induced by USA300 have been reported. We herein report a 64-year-old man who developed CA-IE from a furuncle caused by USA300 MRSA producing PVL and ACME, which resulted in complications of meningitis.

Clonal Lineages, Antimicrobial Resistance, and PVL Carriage of Staphylococcus aureus Associated to Skin and Soft-Tissue Infections from Ambulatory Patients in Portugal

Staphylococcus aureus (S. aureus) is a leading cause of skin and soft-tissue infections (SSTIs) in the community. In this study, we characterized a collection of 34 S. aureus from SSTIs in ambulatory patients in Portugal and analyzed the presence of Panton–Valentine leucocidin (PVL)-encoding genes and antibiotic-resistance profile, which was correlated with genetic determinants, plasmid carriage, and clonal lineage. Nearly half of the isolates (15, 44.1%) were methicillin-resistant Staphylococcus aureus (MRSA) and/or multidrug resistant (MDR). We also detected resistance to penicillin (33/34, 97.1%), fluoroquinolones (17/34, 50.0%), macrolides and lincosamides (15/34, 44.1%), aminoglycosides (6/34, 17.6%), and fusidic acid (2/34, 5.9%), associated with several combinations of resistance determinants (blaZ, erm(A), erm(C), msr(A), mph(C), aacA-aphD, aadD, aph(3′)-IIIa, fusC), or mutations in target genes (fusA, grlA/gyrA). The collection presented a high genetic diversity (Simpson’s index of 0.92) with prevalence of clonal lineages CC5, CC22, and CC8, which included the MRSA and also most MDR isolates (CC5 and CC22). PVL-encoding genes were found in seven isolates (20.6%), three methicillin-susceptible Staphylococcus aureus (MSSA) (ST152-agrI and ST30-agrIII), and four MRSA (ST8-agrI). Plasmid profiling revealed seventeen distinct plasmid profiles. This work highlights the high frequency of antimicrobial resistance and PVL carriage in SSTIs-related S. aureus outside of the hospital environment.

In vitro Tolerability of Biofilm-Forming Trimethoprim-/Sulfamethoxazole-Resistant Small Colony Variants of Staphylococcus aureus Against Various Antimicrobial Agents

Trimethoprim-/sulfamethoxazole-resistant small colony variants (SCVs) of Staphylococcus aureus, which are selected by use of trimethoprim/sulfamethoxazole, are involved in intractable biofilm-forming infection. This study aimed to determine the biofilm formation ability in trimethoprim-/sulfamethoxazole-resistant SCVs of S. aureus and investigate the bactericidal activity of differential antimicrobial agents to its biofilm-forming S. aureus. Between 32 S. aureus wild type (WT) and 32 SCVs selected from its WT, the amount of formed biofilm was compared. Vancomycin, daptomycin, rifampicin, and minocycline were exposed to biofilm-forming S. aureus to determine viable bacterial counts and its susceptibility. The biofilm-producing quantify of SCVs was approximately twice that formed by its WT. Vancomycin and daptomycin reduce 4 logs the bacterial counts of biofilm-forming WT at 24 hours, but did not affect SCVs. Rifampicin and minocycline considerably decreased both WT and SCVs; however, both bacterial counts recovered to an initial number 48 hours later. These survival strains showed resistance to each drug, and rpoB mutation or tet38 mRNA overexpression was confirmed.

Comparison of breakthrough Gram-positive cocci infection during vancomycin vs teicoplanin therapy in patients receiving haematopoietic stem cell transplantation

WHAT IS KNOWN AND OBJECTIVE

Our previous report indicated that teicoplanin (TEIC) caused fewer adverse effects than vancomycin (VCM) in patients with febrile neutropenia (FN) receiving haematopoietic stem cell transplantation (HSCT). However, we observed breakthrough methicillin-resistant-Staphylococcus haemolyticus (MR-S haemolyticus) infection during TEIC therapy in these patients. In this study, we sought to compare the incidence of breakthrough Gram-positive cocci (GPC) infection during VCM and TEIC therapy in this population.

METHODS

A single-centre, retrospective cohort study was conducted. Patients who had received HSCT and were administered VCM (n = 19) or TEIC (n = 38) for FN from 1 September 2011 to 31 August 2019 were enrolled. We compared the incidence of breakthrough GPC infection between the VCM and TEIC groups.

RESULTS

Breakthrough GPC infection during glycopeptide therapy in febrile neutropenic patients received HSCT was observed in three patients (7.9%) in the TEIC group but in none of patients (0%) in the VCM group. MR-S haemolyticus with low glycopeptide susceptibility (TEIC MIC = 2-8 μg/mL, VCM MIC = 2-4 μg/mL) was isolated from blood cultures in all patients with breakthrough GPC infections. All breakthrough infections were cured by changing from TEIC to daptomycin (DAP).

WHAT IS NEW AND CONCLUSION

The incidence of breakthrough GPC infection during glycopeptide therapy in febrile neutropenic HSCT patients was higher in the TEIC group than in the VCM group. MR-S haemolyticus with low glycopeptide susceptibility was isolated from all patients with breakthrough GPC infection and successfully treated with DAP.

Characterisation of community-acquired Staphylococcus aureus causing skin and soft tissue infections in a children's hospital in Shanghai, China

Community-acquired Staphylococcus aureus is a major pathogen responsible for skin and soft tissue infections (SSTIs). This study aimed to investigate the prevalence and molecular characteristics of community-acquired S. aureus isolates recovered from paediatric patients with SSTIs in Shanghai, China. Between January 2015 and January 2018, 91 community-acquired S. aureus isolates were characterised by antibiotic susceptibility, multilocus sequence typing (ST), staphylococcal protein A gene (spa) type and virulence genes. Methicillin-resistant S. aureus (MRSA) strains were also characterised by staphylococcal cassette chromosome mec (SCCmec) type. Forty-one (45.1%) S. aureus isolates were MRSA. ST59 (33.0%, 30/91) was the most common sequence type, and t437 (18.7%, 17/91) was the most common spa type. SCCmec IV and V accounted for 61.0% and 34.1% of all MRSA isolates, respectively. Each isolate carried at least six virulence genes. The positive rates of Panton-Valentine leukocidin genes among all S. aureus, MRSA and methicillin-susceptible S. aureus isolates were 30.8% (28/91), 39.0% (16/41) and 24% (12/50), respectively. The prevalence of community-associated MRSA was surprisingly high among children with community-acquired SSTIs in Shanghai. ST59-t437 was the most prevalent community-acquired S. aureus clone causing SSTIs.

Molecular characteristics of methicillin-resistant Staphylococcus aureus isolated from skin and soft tissue infections collected in the Japanese nationwide surveillance

Skin and soft tissue infections (SSTI) are a common infection among both outpatients and inpatients. The most frequently isolated bacterium in SSTI was Staphylococcus aureus, a quarter of which was methicillin-resistant S. aureus (MRSA). In this study, to investigate molecular epidemiology of the 141 MRSA strains collected in the Japanese nationwide surveillance, we performed multiplex real-time polymerase chain reaction to detect staphylococcal cassette chromosome mec (SCCmec) type and virulence genes. The percentage of SCCmec types I, II, III and IV was 1.4%, 52.5%, 5.7% and 40.4%, respectively. According to the SCCmec type, we classified the strains into health-care-associated (HA)-MRSA (n = 84) and community-associated (CA)-MRSA (n = 57). Among the virulence genes, the percentage of enterotoxin C gene-positive strains was significantly higher in CA-MRSA than in HA-MRSA. No significant differences were detected between the two groups in terms of antibiotic susceptibility and patients' background information, classification of SSTI or symptoms of SSTI.

Microbiology of acute bacterial skin and skin-structure infections in Greece: A proposed clinical prediction score for the causative pathogen

Although clinical definitions of acute bacterial skin and skin-structure infection (ABSSSI) are now well established, guidance of the prediction of likely pathogens based on evidence is missing. This was a large survey of the microbiology of ABSSSIs in Greece. During the period November 2014 to December 2016, all admissions for ABSSSI in 16 departments of internal medicine or surgery in Greece were screened to determine the likely bacterial aetiology. Samples were cultured on conventional media. Expression of the SA442, mecA/mecC and SCCmec-orfX junction genes was assessed. Following univariate and forward logistic regression analysis, clinical characteristics were used to develop scores to predict the likely pathogen with a target of 90% specificity. In total, 1027 patients were screened and 633 had positive microbiology. Monomicrobial infection by Gram-positive cocci occurred in 52.1% and by Gram-negative bacteria in 20.5%, and mixed infection by Gram-positive cocci and Gram-negative bacteria in 27.3%. The most common isolated pathogens were Staphylococcus aureus and coagulase-negative staphylococci. Resistance to methicillin was 57.3% (53.5-61.1%). Three predictive scores were developed: one for infection by methicillin-resistant S. aureus, incorporating recent hospitalisation, atrial fibrillation, residency in long-term care facility (LTCF) and stroke; one for mixed Gram-positive and Gram-negative infections, incorporating localisation of ABSSSI in lumbar area, fluoroquinolone intake in last 6 days, residency in LTCF and stroke; and another for Gram-negative infection, incorporating skin ulcer presentation, peptic ulcer and solid tumour malignancy. In conclusion, methicillin-resistant staphylococci are the main pathogens of ABSSSIs. The scores developed may help to predict the likely pathogen.

Comparative efficacy and safety of vancomycin versus teicoplanin in febrile neutropenic patients receiving hematopoietic stem cell transplantation

WHAT IS KNOWN AND OBJECTIVE

Patients who receive hematopoietic stem cell transplantation (HSCT) are usually administered a calcineurin inhibitor. Because vancomycin is associated with an increased incidence of nephrotoxicity, neutropenic patients receiving HSCT are considered a high-risk population for nephrotoxicity with vancomycin. We retrospectively compared the efficacy and safety of vancomycin and teicoplanin in febrile neutropenic patients receiving HSCT.

METHODS

A single-centre, retrospective cohort study was conducted at the 614-bed Gifu University Hospital in Japan. Patients who received HSCT and were administered vancomycin or teicoplanin by injection for febrile neutropenia from 1 January 2012 to 31 August 2017 were enrolled. Time to attain an effective trough concentration, clinical efficacy and adverse events were compared between the two groups.

RESULTS

Time to attain an effective trough concentration of over 10 μg/mL tended to be shorter in the teicoplanin group than in the vancomycin group (median 3, 95% confidence interval [CI] 2.4-3.6 days vs median 6, 95% CI 1.5-10.5 days; hazard ratio [HR] 0.4, 95% CI 0.15-1.06; P = .066). The rate of clinical failure was lower in the teicoplanin group than in the vancomycin group (18.8% vs 53.8%, P = .113). In addition, the overall incidence of nephrotoxicity was significantly lower in the teicoplanin group (0% vs 46.2%, P = .004).

WHAT IS NEW AND CONCLUSION

Our findings suggest that administration of teicoplanin may lead to early attainment of the effective concentration with a lower rate of clinical failure and incidence of nephrotoxicity compared to vancomycin in febrile neutropenic patients receiving HSCT.

Investigation of the susceptibility trends in Japan to fluoroquinolones and other antimicrobial agents in a nationwide collection of clinical isolates: A longitudinal analysis from 1994 to 2016

The susceptibilities of clinical isolates to fluoroquinolones and other antimicrobial agents were surveyed to obtain an accurate understanding of trends in incidence and antimicrobial resistance. The samples were collected from across Japan, biennially or triennially, between 1994 and 2016 and a defined level of resistance to fluoroquinolone was determined. Streptococcus pneumoniae, Streptococcus pyogenes and Haemophilus influenzae exhibited stable and high rates of susceptibility to fluoroquinolones over the period examined. For methicillin-resistant Staphylococcus aureus the rate of resistance to levofloxacin and ciprofloxacin was 81.3-93.5% and 83.2-94.2%, respectively, which was markedly higher than that of methicillin-susceptible S. aureus, while sitafloxacin-resistant methicillin-susceptible and methicillin-resistant S. aureus were isolated at 0.3-0.7% and 16.9-36.5%, respectively. The rate of levofloxacin or ciprofloxacin-resistant Escherichia coli increased from around 2-3% between 1994 and 1998 to around 35% in 2016, but the rate of fluoroquinolone-susceptible Klebsiella pneumoniae stayed high at over 94.6% during the study period. Although no fluoroquinolone-resistance in clinical isolates of Salmonella spp. was detected from 1994 to 2002, the resistance rate increased slightly after 2004 and reached to 1.9%-4.7% in 2016. The rate of fluoroquinolone-susceptible Pseudomonas aeruginosa isolated from urinary tract and respiratory tract infections improved during the period examined from 41.8-67.0% to 91.2-94.2%, and from 78.9-88.5% to 90.1-94.6%, respectively. Against Acinetobacter spp., the susceptibility rate of fluoroquinolones was almost constant at around 90%, but one multidrug-resistant isolate was detected in 2013. Overall, the susceptibility to fluoroquinolones was maintained over 20 years against tested bacteria except for MRSA and E. coli.

Screening method for trimethoprim/sulfamethoxazole-resistant small colony variants of Staphylococcus aureus

OBJECTIVES

Trimethoprim/sulfamethoxazole (SXT) is used to treat Staphylococcus aureus infections. However, the effect of treatment with SXT is sometimes not sufficient and there are patients whose treatment has to be prolonged. There are few reports of isolated strains of SXT-resistant S. aureus, but it is possible that some resistant strains cannot be detected by current testing methods We have therefore developed a tool to identify these resistant strains.

METHODS

The mutant selection window (MSW) of SXT for 40 clinical isolates of S. aureus, including 20 methicillin-resistant S. aureus (MRSA), was determined. The optimum concentration of SXT and thymidine in agar for detecting SXT-resistant small colony variants (SCVs) of S. aureus was investigated.

RESULTS

The MSW₅₀ and MSW₉₀ of SXT, presented as a multiple of the minimum inhibitory concentration (MIC), were 16× MIC and >256× MIC, respectively. SCVs were detected within the MSW in 32 (80%) of the 40 clinical isolates studied. To maintain the morphology of SCVs, the most suitable concentrations of SXT and thymidine for screening were 4mg/L and 0.01μg/mL, respectively. All 32 SCVs were resistant to SXT (MIC >32mg/L). The sensitivity and specificity of this screening method was 100% and 88.9%, respectively.

CONCLUSIONS

SXT-resistant SCVs are not usually detected by routine laboratory tests performed in hospitals. However, the screening test described here can easily distinguish SXT-resistant SCVs among S. aureus isolated from specimens. This newly developed screening test could become an important tool to prevent inappropriate use of SXT.

Management of superficial and deep-seated Staphylococcus aureus skin and soft tissue infections in sub-Saharan Africa: a post hoc analysis of the StaphNet cohort

PURPOSE

The incidence of Staphylococcus aureus skin and soft tissue infection (SSTI) is high in sub-Saharan Africa. This is fueled by a high prevalence of Panton-Valentine leukocidin (PVL), which can be associated with necrotizing disease. The aim was to describe the clinical presentation and the treatment of SSTI in the African setting and to identify challenges in the management.

METHODS

Patients (n = 319) were recruited in DR Congo (n = 56, 17.6%), Gabon (n = 89, 27.9%), Mozambique (n = 79, 24.8%) and Tanzania (n = 95, 29.8%) during the prospective observational StaphNet cohort study (2010-2015). A physician recorded the clinical management in standardized questionnaires and stratified the entity of SSTI into superficial (sSSTI) or deep-seated (dSSTI). Selected virulence factors (PVL, β hemolysin) and multilocus sequence types (MLST) were extracted from whole genome sequencing data.

RESULTS

There were 220/319 (69%) sSSTI and 99/319 (31%) dSSTI. Compared to sSSTI, patients with dSSTI were more often hospitalized (13.2 vs. 23.5%, p = 0.03), HIV-positive (7.6 vs. 15.9%, p = 0.11), and required more often incision and drainage (I&D, 45.5 vs. 76.5%, p = 0.04). The proportion of an adequate antimicrobial therapy increased marginally from day 1 (empirical therapy) to day 3 (definite therapy), for sSSTI (70.7 to 72.4%) and dSSTI (55.4 to 58.9%). PVL was a risk factor for I&D (OR = 1.7, p = 0.02) and associated with MLST clonal complex CC121 (OR = 2.7, p < 0.001).

CONCLUSION

Appropriate antimicrobial agents and surgical services to perform I&D were available for the majority of patients. Results from susceptibility testing should be considered more efficiently in the selection of antimicrobial therapy.