Antibiotic Susceptibility, Virulence Pattern, and Typing of Staphylococcus aureus Strains Isolated From Variety of Infections in India

Abstract

Staphylococcus aureus is one of the major causes of nosocomial infections. This organism produces powerful toxins and cause superficial lesions, systemic infections, and several toxemic syndromes. A total of 109 S. aureus strains isolated from a variety of infections like ocular diseases, wound infection, and sputum were included in the study. Minimum inhibitory concentration (MIC) was determined against 8 antimicrobials. PCR determined the presence of 16S rRNA, nuc, mecA, czrC, qacA/B, pvl, and toxin genes in S. aureus isolates. Pulse-field gel electrophoresis (PFGE), multi-locus sequence typing (MLST), SCCmec, spa-, and agr-typing and serotyping determined the diversity among them. All isolates of S. aureus were resistant to two or more than two antibiotics and generated 32 resistance patterns. These isolates were positive for 16S rRNA and S. aureus-specific nuc gene, but showed variable results for mecA, czrC, and qacA/B and pvl genes. Of the 32 methicillin-resistant S. aureus (MRSA), 13 strains carried SCCmec type V, seven type IV, two type III, and nine carried unreported type UT6. Of the 109 strains, 98.2% were positive for hlg, 94.5% for hla, 86.2% for sei, 73.3% for efb, 70.6% for cna, 30.2% for sea, and 12.8% for sec genes. Serotypes VII and VI were prevalent among S. aureus strains. PFGE analysis grouped the 109 strains into 77 clusters. MLST classified the strains into 33 sequence types (ST) and eight clonal complexes (CCs) of which 12 were singletons, and two belong to new allelic profiles. Isolates showed 46 spa-types that included two new spa-types designated as t14911 and t14912. MRSA and methicillin-susceptible S. aureus (MSSA) isolates were diverse in terms of antibiotic resistance pattern, toxin genotypes, SCCmec types, serotypes and PFGE, MLST, and spa-types. However, few isolates from eye infection and wound infection belong to CC239, ST239, and spa-type t037/t657. The study thus suggests that S. aureus strains are multidrug resistant, virulent, and diverse irrespective of sources and place of isolation. These findings necessitate the continuous surveillance of multidrug-resistant and virulent S. aureus and monitoring of the transmission of infection.

Investigation of SCCmec types I–IV in clinical isolates of methicillin-resistant coagulase-negative staphylococci in Ahvaz, Southwest Iran

“…Our PCR targeted only SCCmec types I-IV, but 11 isolates in this study were negative for these four types indicating that the MR-CONS isolates in our region have SCCmec types belonging to the other established types or have novel types. Generally, performing diverse typing methods can afford better and more valuable epidemiological data about the clonal diversity of the isolates that can be advantageous for outbreak researches [41,42]. Another limitation of the present study was the lack of determination of the minimum inhibitory concentrations of tested antibiotics.…”

Epidemiological and Clinical Evidence for the Role of Toxins in S. aureus Human Disease

“…Another study typed 334 invasive S. aureus isolates and found that, while hlg was present in most of the invasive isolates, there was no observable trend towards a particular disease type [ 77 ]. Similarly, a study in India reported that 98.2% of MRSA strains screened contained hlg [ 78 ] and another study in Iran found hlg present in all infected individuals when investigating isolates from nasal carriage [ 79 ]. In contrast, others have found lower rates of hlg , with one study in Iran reporting a frequency of only 6.3% in MRSA strains [ 80 ].…”

Table_1.DOCX

“…Variable results of the agr types as crucial regulatory component of bacterial virulence factor expression have been published in previous studies (Goudarzi et al, 2017;Aggarwal et al, 2019). In the present study, only two outbreak strains were not typed for the agr locus, and several studies indicate that the distribution of the agr types depends on the geographic region (Goudarzi et al, 2017;Aggarwal et al, 2019). Specific agr types are associated with specific clinical features (Ji et al, 1997;Sakoulas et al, 2002).…”

“…CC5 contained the most prevalent MRSA strain, and CC30 was characteristic of the MSSA strains. MRSA strains belonging to CC5 have been reported in different parts of the world (Goudarzi et al, 2017;Aggarwal et al, 2019;Chen et al, 2020;Neradova et al, 2020). CC5-related MRSA has been associated with SCCmec type II and a hospital origin, and with the epidemic clone New York/Japan widely distributed worldwide, including in Mexico (Ishihara et al, 2010;Rodríguez-Noriega et al, 2010).…”

“…In contrast, protein A (Spa), cell wall secretory protein (IsaA), and surface receptors (MnhA, MnhF, and MnhG) are deregulated by RNAIII from the agr system (Jenul and Horswill, 2018). The typing of polymorphisms in the agr system has facilitated the identification and classification of MRSA clinical isolates in Europe, America, India, Vietnam, and Iran (Hetem et al, 2016;Goudarzi et al, 2017;Aggarwal et al, 2019;Nguyen et al, 2020). Although the agr system is conserved in most strains of S. aureus, four polymorphisms in the agr locus have been identified based on the variable region between AgrD, the C-terminal portion of AgrB, and the N-terminal portion of AgrC (Gilot et al, 2002).…”