Linezolid-resistant Staphylococcus haemolyticus: Emergence of G2447U & C2534U mutations at the domain V of 23S ribosomal RNA gene in a tertiary care hospital in India

Staphylococcus haemolyticus: An updated review on nosocomial infections, antimicrobial resistance, virulence, genetic traits, and strategies for combating this emerging opportunistic pathogen

Staphylococcus haemolyticus, a key species of the Staphylococcus genus, holds significant importance in healthcare-associated infections, due to its notable resistance to antimicrobials, like methicillin, and proficient biofilms-forming capabilities. This coagulase-negative bacterium poses a substantial challenge in the battle against nosocomial infections. Recent research has shed light on Staph. haemolyticus genomic plasticity, unveiling genetic elements responsible for antibiotic resistance and their widespread dissemination within the genus. This review presents an updated and comprehensive overview of the clinical significance and prevalence of Staph. haemolyticus, underscores its zoonotic potential and relevance in the one health framework, explores crucial virulence factors, and examines genetics features contributing to its success in causing emergent and challenging infections. Additionally, we scrutinize ongoing studies aimed at controlling spread and alternative approaches for combating it.

Mucoid Staphylococcus haemolyticus: an unheeded multidrug-resistant pathogen

Coagulase-negative Staphylococci (CoNS) are among the most abundant members of human skin microbiome. CoNS have lately been recognized as substantial agents in plethora of infections, especially nosocomial infections in preterm infants and immunocompromised patients. Staphylococcus haemolyticus is the second most common species isolated from blood, and identification is further hindered when there is a deviation in morphology from the classical one. Here, we report an uncommon case of multidrug resistant mucoid S. hemolyticus isolated from blood in a patient of polytrauma. The patient was managed with ceftriaxone-sulbactam, gentamicin, and meropenem as empirical therapy, which was subsequently changed to intravenous vancomycin. The patient showed favorable response to treatment. Mucoid isolates are known to be more virulent and multi-drug resistant than the classical morphotypes. We also conducted systematic review to decipher the prevalence of mucoid S. hemolyticus and linezolid (LZD) resistance in the same. This case highlights the significance of awareness of mucoid phenotypes of Gram-positive cocci for clinical microbiologists to reach accurate identification. Resistance to LZD further underscores the need of restriction policies in hospitals and to roll out antimicrobial stewardship program stringently, so that the growing resistance could be contained.

Detection of a Novel G2603T Mutation in cfr Harboring Linezolid-Resistant Staphylococcus haemolyticus: First Report from India

Background Staphylococcus haemolyticus has emerged as an important multidrug-resistant nosocomial pathogen. Linezolid is useful in the treatment of severe infections caused by methicillin-resistant Staphylococci. Resistance to linezolid in Staphylococci is due to one or more of the following mechanisms: acquisition of the cfr (chloramphenicol florfenicol resistance) gene, mutation in the central loop of domain V of the 23S rRNA, and mutation in the rplC and rplD genes. This study was carried out to detect and characterize resistance to linezolid among the clinical isolates of Staphylococcus haemolyticus.

Materials and Methods The study included 84 clinical isolates of Staphylococcus haemolyticus. Susceptibility to various antibiotics was determined by disc diffusion method. Minimum inhibitory concentration (MIC) was determined by agar dilution method for linezolid. Methicillin resistance was screened using oxacillin and cefoxitin disc. Polymerase chain reaction was done to detect mecA, cfr and mutations in the V domain of the 23S rRNA gene.

Results Resistance to linezolid was exhibited by 3 of the 84 study isolates with MIC more than 128 µg/mL. The cfr gene was detected in all the three isolates. The G2603T mutation was observed in the domain V of the 23S rRNA among two isolates, whereas one isolate lacked any mutation.

Conclusion The emergence and spread of linezolid-resistant Staphylococcus haemolyticus isolates carrying G2603T mutation in the domain V of the 23S rRNA and harboring the cfr gene pose a threat in clinical practice.

Clinical Infections, Antibiotic Resistance, and Pathogenesis of Staphylococcus haemolyticus

Staphylococcus haemolyticus (S. haemolyticus) constitutes the main part of the human skin microbiota. It is widespread in hospitals and among medical staff, resulting in being an emerging microbe causing nosocomial infections. S. haemolyticus, especially strains that cause nosocomial infections, are more resistant to antibiotics than other coagulase-negative Staphylococci. There is clear evidence that the resistance genes can be acquired by other Staphylococcus species through S. haemolyticus. Severe infections are recorded with S. haemolyticus such as meningitis, endocarditis, prosthetic joint infections, bacteremia, septicemia, peritonitis, and otitis, especially in immunocompromised patients. In addition, S. haemolyticus species were detected in dogs, breed kennels, and food animals. The main feature of pathogenic S. haemolyticus isolates is the formation of a biofilm which is involved in catheter-associated infections and other nosocomial infections. Besides the biofilm formation, S. haemolyticus secretes other factors for bacterial adherence and invasion such as enterotoxins, hemolysins, and fibronectin-binding proteins. In this review, we give updates on the clinical infections associated with S. haemolyticus, highlighting the antibiotic resistance patterns of these isolates, and the virulence factors associated with the disease development.

In vitro activity of ceftaroline and other antimicrobial agents against Gram positive bacterial isolates: Descriptive study from a university hospital

PURPOSE

Ceftaroline is a novel antibiotic approved by USA Food and Drug Administration (FDA) for the treatment of acute bacterial skin and skin structure infections (ABSSSI) and community-acquired bacterial pneumonia (CABP). It has potent in vitro activity against Staphylococci, including methicillin-resistant strains, whose incidence is increasing worldwide and they are often difficult to treat. The present study was done to investigate the susceptibility of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase-negative Staphylococcus (MR-CoNS) to ceftaroline and other antimicrobial agents in patient samples and to evaluate clinical profile of these patients.

METHODS

All consecutive, nonduplicate isolates of MRSA and MR-CoNS recovered from patient samples between June 2020 to December 2020 were included in the study. Species identification was done by Matrix Assisted Laser Desorption Ionization Time of Flight Mass Spectromtery (MALDI-TOF-MS) (BioMérieux, France). Antimicrobial sensitivity of ceftaroline and other comparator antimicrobials was done as per the Clinical and Laboratory Standards Institute (CLSI, 2020). Statistical Package for the Social Sciences (IBM-SPSS) software (Version 25) was used for statistical study.

RESULTS

Total 134 clinical isolates of the study consisted of MR-CoNS (115 isolates; 85.8%) and MRSA (19 isolates; 14.2%).89.5% MRSA isolates were sensitive to ceftaroline. 44.3% and 32.2% MR-CoNS isolates had ceftaroline MIC ≤1 ​μg/ml and MIC ​= ​2-4 ​μg/ml respectively.

CONCLUSIONS

Ceftaroline exhibited potent in vitro activity against both MRSA and MR-CoNS in the study.

The Prevalence and Antimicrobial Susceptibility Pattern of Gram-Positive Pathogens: Three-Year Study at a Private Tertiary Care Hospital in Mumbai, India

Introduction  The growing resistance pattern of the gram-positive pathogens along with a steady increase in minimum inhibitory concentration of the currently available antibiotics have led to an increase in morbidity and mortality rates in India. This study aims to access the shifting antibiotic susceptibility paradigm of the gram-positive pathogens in various infections at a tertiary care center.

Methods  This is a 3-year retrospective observational study which was performed from January 2016 to December 2018 at a tertiary care hospital in Mumbai. All clinically significant gram-positive cocci isolated from a variety of clinical specimens were studied for their prevalence and antimicrobial susceptibility.

Results  Out of 4,428 gram-positive isolates, Staphylococcus aureus (35.3%) was the commonly encountered pathogen, followed by Enterococcus spp. (32.1%) and coagulase-negative Staphylococcus (CoNS) (25.7%). S. aureus was majorly isolated from skin and soft tissue infections (60.3%), followed by patients with respiratory tract infections (18.2%) and blood stream infections (13%). Among S. aureus , particularly methicillin-resistant S. aureus (MRSA), prevalence increased from 29.5% in 2016 to 35.1% in 2018, with an overall prevalence of 33.6%. All S. aureus isolates were 100% sensitive toward vancomycin, linezolid, tigecycline, and teicoplanin. However, the CoNS isolates showed a higher resistance rate with reduced susceptibility toward linezolid and teicoplanin. High prevalence of resistance was observed across gram-positive isolates with commonly used antibiotics such as ciprofloxacin, levofloxacin, and erythromycin. While the prevalence of linezolid-resistant enterococcus (LRE) was 3.6%, vancomycin (VRE) and teicoplanin resistance among the enterococcus species was as high as 7.7% and 7.5%, respectively.

Conclusion  Rising methicillin resistance among the Staphylococcal species (MRSA and MR-CoNS) along with reduced susceptibility toward currently available anti-MRSA agents is a matter of serious concern as it limits the therapeutic options for treating multidrug resistant (MDR) gram-positive infections.

First Case of Staphylococci Carrying Linezolid Resistance Genes from Laryngological Infections in Poland

Linezolid is currently used to treat infections caused by multidrug-resistant Gram-positive cocci. Both linezolid-resistant S. aureus (LRSA) and coagulase-negative staphylococci (CoNS) strains have been collected worldwide. Two isolates carrying linezolid resistance genes were recovered from laryngological patients and characterized by determining their antimicrobial resistance patterns and using molecular methods such as spa typing, MLST, SCCmec typing, detection of virulence genes and ica operon expression, and analysis of antimicrobial resistance determinants. Both isolates were multidrug resistant, including resistance to methicillin. The S. aureus strain was identified as ST-398/t4474/SCCmec IVe, harboring adhesin, hemolysin genes, and the ica operon. The S. haemolyticus strain was identified as ST-42/mecA-positive and harbored hemolysin genes. Linezolid resistance in S. aureus strain was associated with the mutations in the ribosomal proteins L3 and L4, and in S. haemolyticus, resistance was associated with the presence of cfr gene. Moreover, S. aureus strain harbored optrA and poxtA genes. We identified the first case of staphylococci carrying linezolid resistance genes from patients with chronic sinusitis in Poland. Since both S. aureus and CoNS are the most common etiological factors in laryngological infections, monitoring of such infections combined with surveillance and infection prevention programs is important to decrease the number of linezolid-resistant staphylococcal strains.