Emergence of Vancomycin-Resistant Enterococcus faecium ST 80 in Pakistan

To the Editor:

Since first appearing in the 1980s, vancomycin-resistant Enterococcus spp. (VRE) have spread worldwide [1]. Currently, most reported clinical VRE isolates are multi-drug–resistant vancomycin-resistant Enterococcus faecium (VREfm) harboring vanA gene. Specific clonal types of VREfm make it possible to monitor clonal proliferation and spread [2]. In Pakistan, sporadic cases have described the presence of VREfm encoding vanA gene but none described their clonal type [3].

During a study of the prevalence of carbapenem-resistant strains in surgical ward of Al-Syed hospital in Rawalpindi City of Pakistan, isolation of enterococci was performed on Columbia agar supplemented by 5% sheep blood (bioMérieux, Marcy l'Etoile, France). A total of three isolates were recovered from three inpatients after a surgical procedure to remove kidney stones. These isolates were collected from urine samples in March 2017 (isolate 26 and 27) and from pus swabs in April 2017 (isolate 87). The three isolates were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF; Microflex, Bruker Daltonics, Bremen, Germany) as E. faecium strains (26, 27, and 87). Antibiotic susceptibility testing (AST) was performed by disc diffusion method and interpreted according to the European Committee on AST (EUCAST) guidelines. Minimum inhibitory concentration (MIC) was determined by the E-test method (bioMérieux, Marcy l'Etoile, France) for vancomycin and teicoplanin. All strains were sensitive to fosfomycin, fusidic acid, and linezolide but resistant to penicillin, clindamycin, cefoxitin, oxacillin, erythromycin, ciprofloxacin, rifampicin, sulfamethoxazole-trimethoprim, teicoplanin, and vancomycin with a MIC >256 mcg/mL. Teicoplanin MIC was 64 mcg/mL for strain 87 and 24 mcg/mL for others strains. Strains 26 and 27 were sensitive to gentamycin but resistant to pristinamycin and doxycycline, in contrast to the strain 87. Standard polymerase chain reaction (PCR) amplification was conducted to assess the presence of vanA and vanB genes [4] and revealed that all E. faecium strains carried vanA gene. All strains belonged to ST80 according to the Oxford MLST schemes (https://pubmlst.org/efaecium/).

In Pakistan, few studies of VRE have been conducted, however, existing studies are concerning. In 2014 more than 11% of all hospital Enterococcus isolates were VRE [3]. In our study, the three VREfm harboring vanA gene belonged to ST80 included in clonal complex CC17, which is a worldwide high-risk enterococcal clonal complex well-known in hospitals (2). This lineage is characterized by resistance to ampicillin, quinolone, and by the presence of putative virulence genes. Observation of the same clonal type of VREfm in three patients from the same surgical ward from March 2017 to April 2017 suggested an outbreak and the presence of potential reservoir of vanA gene-encoded VREfm. These isolates were also resistant to β-lactams and to gentamycin for strain 87, thus reducing therapeutic strategy and suggested propagation of multidrug resistant VREfm. Al-Syed Hospital has an outbreak control strategy directed toward prevention of nosocomial infections. In the case of any outbreak, strict measures are taken with enhanced surveillance and source tracking as well as fumigation of laboratories with appropriate disinfectant. Sterilization of materials and sterilizer is verified.. Sanitary, laboratory staff, physicians, as well as nurses are duly trained to control the cross-infections through frequent training. Staff is kept informed continuously about the current situation of outbreaks and nosocomial infections. With this control strategy, no other VRE outbreak has been reported to date. Nevertheless, exact source of outbreak could not be traced.

Surveillance studies are essential for carefully monitoring trends. The clonal spread of vanA-containing E. faecium isolates ST80 among patients reported in this study highlights the importance of establishing strict infection control measures. To our knowledge, this was the first study to sequence type of VREfm in Pakistan.