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

Temporal trends of skin and soft tissue infections caused by methicillin-resistant Staphylococcus aureus in Gabon

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the leading causes of mortality due to bacterial antimicrobial resistance. While S. aureus is common in skin and soft tissue infections (SSTI) in Africa, data on MRSA rates are scarce and reports vary widely across the continent (5%-80%). In this study, we describe the proportion of MRSA causing SSTI in Lambaréné, Gabon, over an 11-year period.

METHODS

We retrospectively analyzed data from 953 bacterial specimens collected from inpatients and outpatients with SSTI at the Albert Schweitzer Hospital, Lambaréné, Gabon, between 2009 and 2019. We determined temporal changes in the prevalence of MRSA and identified risk factors for SSTI with MRSA.

RESULTS

68% of all specimens with bacterial growth yielded S. aureus (n = 499/731), of which 7% (36/497) with antimicrobial susceptibility testing were identified as MRSA. Age above 18 years, admission to the surgical ward, and deep-seated infections were significantly associated with MRSA as the causative agent. After an initial decline from 7% in 2009, there was a marked increase in the proportion of MRSA among all S. aureus from SSTI from 3 to 20% between 2012 and 2019. The resistance rate to erythromycin was significantly higher in MRSA than in methicillin-susceptible S. aureus (73% vs. 10%), and clindamycin resistance was detected exclusively in MRSA isolates (8%).

CONCLUSION

The increasing proportion of MRSA causing SSTI over the 11-year period contrasts with many European countries where MRSA is on decline. Continuous surveillance of MRSA lineages in the hospital and community along with antibiotic stewardship programs could address the increasing trend of MRSA.

Bacterial isolates and their antimicrobial susceptibility profile of superficial and deep-seated skin and soft tissue infections

Background

Skin and soft tissue infections (SSTIs) are caused by microbial invasion of healthy or damaged skin. SSTIs are difficult to manage and contribute to chronicity and emergence of antimicrobial resistance.

Objectives

To ascertain the prevalence of bacteria causing SSTIs and their antimicrobial susceptibility patterns.

Methods

A prospective study between November 2020 and May 2021. A total of 447 samples from SSTIs were analyzed.

Results

A total of 347 samples revealed mono-bacterial growth, of which 67% were male. SSTIs are common among patients aged 21-50 years with the dominance (78%) of gram-negative rods (GNRs). Escherichia coli (36%), Klebsiella spp. (22%), Staphylococcus aureus (16%), and Pseudomonas aeruginosa (11%) were predominant organisms. GNRs were highly resistant (>65%) to ciprofloxacin and trimethoprim-sulfamethoxazole. For injectable antibiotics, the highest resistance was determined against ceftriaxone, and the least resistance was determined against amikacin. Resistance against carbapenem was the highest among P. aeruginosa (53%) and Klebsiella spp. (32%). S. aureus showed the highest resistance against ciprofloxacin, and the least resistance was determined against clindamycin. Of 57 S. aureus isolates, 86% isolates were methicillin-resistant Staphylococcus aureus (MRSA). All isolates of P. aeruginosa and S. aureus were sensitive to polymyxin B and vancomycin, respectively. The prevalence of multidrug-resistant E. coli and Klebsiella spp. was higher among deep-seated SSTIs (dSSTIs).

Conclusions

The predominant etiology of SSTIs is GNR. Currently, there is very high resistance against oral antibiotics. Antimicrobial resistance against carbapenem has also increased. Moreover, there is a high frequency of MRSA. MDR E. coli and Klebsiella spp. isolates are frequently involved in dSSTIs.

Neutralization of the Staphylococcus aureus Panton-Valentine leukocidin by African and Caucasian sera

Background

The prevalence of Staphylococcus aureus isolates carrying the Panton-Valentine leukocidin (PVL) gene is higher in Africa (≈50%) compared to Europe (< 5%). The study aimed to measure anti-PVL-antibodies in Africans and Germans in a multi-center study and to test whether detected antibodies can neutralize the cytotoxic effect of PVL on polymorphonuclear leukocytes (PMNs).

Methods

Sera from asymptomatic Africans (n = 22, Nigeria, Gabon) and Caucasians (n = 22, Germany) were used to quantify antibody titers against PVL and α-hemolysin (in arbitrary units [AU]) by ELISA. PMNs from one African and German donor were exposed to 5 nM recombinant PVL to measure the neutralizing effect of serial dilutions of pooled sera from African and Caucasian participants, or donor sera at 0.625 and 2.5% (v/v).

Results

Anti-PVL-antibodies were significantly higher in Africans than in Germans (1.9 vs. 0.7 AU, p < 0.0001). The pooled sera from the study participants neutralized the cytotoxic effect of PVL on African and German PMNs in a dose dependent manner. Also, neutralization of PVL on PMNs from the African and German donors had a stronger effect with African sera (half-maximal inhibitory concentration (IC50) = 0.27 and 0.47%, respectively) compared to Caucasian sera (IC50 = 3.51 and 3.59% respectively).

Conclusion

Africans have higher levels of neutralizing anti-PVL-antibodies. It remains unclear if or at what level these antibodies protect against PVL-related diseases.

Implementation of an antimicrobial stewardship programme in three regional hospitals in the south-east of Liberia: lessons learned

Background

Antimicrobial stewardship (AMS) programmes can improve the use of antimicrobial agents. However, there is limited experience in the implementation of such programmes in low- and middle-income countries (LMICs).

Objectives

To assess the effect of AMS measures in south-east Liberia on the quality of antimicrobial use in three regional hospitals.

Methods

A bundle of three measures (local treatment guideline, training and regular AMS ward rounds) was implemented and quality indicators of antimicrobial use (i.e. correct compounds, dosage and duration) were assessed in a case series before and after AMS ward rounds. Primary endpoints were (i) adherence to the local treatment guideline; (ii) completeness of the microbiological diagnostics (according to the treatment guideline); and (iii) clinical outcome. The secondary endpoint was reduction in ceftriaxone use.

Results

The majority of patients had skin and soft tissue infections (n = 108) followed by surgical site infections (n = 72), pneumonia (n = 64), urinary tract infection (n = 48) and meningitis (n = 18). After the AMS ward rounds, adherence to the local guideline improved for the selection of antimicrobial agents (from 34.5% to 61.0%, P < 0.0005), dosage (from 15.2% to 36.5%, P < 0.0005) and duration (from 13.2% to 31.0%, P < 0.0005). In total, 79.7% of patients (247/310) had samples sent for microbiological analysis. Overall, 92.3% of patients improved on Day 3 (286/310). The proportion of patients receiving ceftriaxone was significantly reduced after the AMS ward rounds from 51.3% to 14.2% (P < 0.0005).

Conclusions

AMS measures can improve the quality of antimicrobial use in LMICs. However, long-term engagement is necessary to make AMS programmes in LMICs sustainable.

The Role of Staphylococcus aureus in Mastitis : A Multidisciplinary Working Group Experience

BACKGROUND

Breastfeeding women are at risk of developing mastitis during the lactation period. Staphylococcus aureus has emerged as the community-acquired pathogen responsible for virulence (methicillin resistance and Panton-Valentine leukocidin toxin producing).

RESEARCH AIM

The aim was to compare the microorganisms responsible for mastitis and breast abscesses during breastfeeding.

METHODS

This observational study was conducted with a sample of women (N = 60) admitted to our hospital between 2016 and 2018. Participants affected by mastitis and breast abscess were studied and cared for by a multidisciplinary working group. A diagnostic breast ultrasound identified the pathology.

RESULTS

Twenty-six participants (43.3%) were affected by mastitis and 34 (56.7%) by breast abscess. The most common microorganism identified was Staphylococcus aureus (S. aureus; mastitis, n = 13; abscesses, n = 24). Methicillin resistance was identified in 21 (44.7%) S. aureus strains: 17 (80.9%) cases of abscess and four (19.1%) cases of mastitis. The median number of months of breastfeeding was smaller in the methicillin-resistant S. aureus (MRSA) cases (median = 3, range = 1-20 months) than in the methicillin-sensitive S. aureus (MSSA) cases (median = 6.5, range = 3-21 months). The Panton-Valentine leukocidin toxin gene was detected in 12 (25.5%) cases (MRSA, n = 8, 66.7%; MSSA, n = 4, 33.3%). Hospitalization was required more frequently in MRSA (n = 8, 38%; five Panton-Valentine leukocidin positive) than in MSSA cases (n = 5, 19%; one Panton-Valentine leukocidin positive). Four women out of the eight MRSA cases (50%) that were Panton-Valentine leukocidin positive stopped breastfeeding during mammary pathologies, three (37.5%) participants continued breastfeeding until the follow-up recall, and one case was lost at follow-up.

CONCLUSION

Clinical severity was probably complicated by the presence of the Panton-Valentine leukocidin toxin, which required hospitalization more frequently.

Characterization of Panton-Valentine leukocidin-positive Staphylococcus aureus from skin and soft tissue infections and wounds in Nigeria: a cross-sectional study

Background:Staphylococcus aureus is a significant pathogen implicated in numerous nosocomial and community-acquired infections. The Panton-Valentine leukocidin (PVL) can be associated with severe necrotizing diseases such as pneumonia, skin and soft tissue infection (SSTI).  Methods: In total, 96 S. aureus isolates were obtained from patients presenting with wounds (n=48) and soft tissue infections (SSTIs, n=48). These were characterized based on their antimicrobial susceptibility profile, the possession of virulence genes (e.g. capsular type, PVL), accessory gene regulator ( agr) type, and the staphylococcal protein A ( spa) type. The production of the PVL protein was assessed by western blotting. Results: All isolates were susceptible to methicillin. The resistance was highest to penicillin (97.9%), followed by trimethoprim/sulfamethoxazole (85.4%) and tetracycline (10.4%). The PVL gene was found in 83.3% of isolates from SSTIs and in 79.2% of isolates from wound. Of these, 53 (68%) produced PVL as assessed by western blotting. The most prevalent spa type was the t084 (78.1%, n=75) and, majority of the isolates carried  agr2 (82.3%, n=79). Conclusions: Prevalence of antibiotic resistant PVL-positive methicillin susceptible S. aureus strains has severe implications on PVL mediated infections.