Major Gram-positive Bacteria Research Articles

Diabetic Foot Ulcer in India: Aetiological Trends and Bacterial Diversity.

Diabetes is one of the most prevalent epidemic metabolic disorders, responsible for a significant amount of physical, psychological and economic loss in human society. Diabetic foot ulcer (DFU) is one of the extreme pathophysiological consequences of diabetes. Bacterial infection is the most important cause of chronic DFU. Bacterial species or their biofilms show multidrug resistance, which complicates DFU and consequently leads to amputation of the infected part. Since the Indian population comprises diverse ethnic and cultural groups, this could influence the aetiology of diabetic foot infections and bacterial diversity. We reviewed 56 articles published from 2005 to 2022 on the microbiology of DFU and extracted the data on study location, number of patients analysed in the study, pathophysiological complications, age of the patients, sex of the patient, type of bacteria, type of infection (mono or polymicrobial), predominant bacteria (Gram-positive or Gram-negative), predominant isolates and multiple drug resistance (tested or not). We analysed data and described aetiological trends in diabetic foot infections and bacterial diversity. The study revealed that Gram-negative bacteria are predominant as compared to Gram-positive bacteria in individuals with diabetes with DFU in India. Escherichia coli, Pseudomonas aeruginosa, Klebsiella sp. and Proteus sp. were the most predominant Gram-negative bacteria, while Staphylococcus aureus and Enterococcus sp. were the major Gram-positive bacteria in DFU. We discuss bacterial infections in DFU in the context of bacterial diversity, sampling methods, demography and aetiology.

Changes of bacterial spectrum and drug resistance in patients with posttraumatic bone infection

Objective To investigate the bacterial spectrum and drug resistance of bone infection after multiple hospitalizations. Methods A retrospective case series study was conducted on 95 patients with bone infection due to injuries admitted in the General Hospital of Shenyang Military Area from January 2009 to December 2016. There were 76 males and 34 females, with an average age of 47 years (range, 17-94 years). Bacterial culture and drug sensitivity tests were performed in 246 specimens of the infection secretions and infected tissues. The bacterial species and drug resistance data of all the specimens were statistically analyzed. The numbers and ratios of Gram-positive bacteria and Gram negative bacteria were counted according to the changes of hospitalization frequency, and the changes of drug resistance of Staphylococcus aureus after repeated hospitalizations were also recorded. Results A total of 110 pathogenic bacteria were isolated, and mixed infection was found in 19% of the bacteria. There were 61 Gram-positive bacteria (55.5%), including 35 Staphylococcus aureus [seven methicillin-resistant staphylococcus (MRSA) strains], accounting for 57% of Gram-positive strains. Other Gram positive bacteria were mainly Enterococcus faecalis and Staphylococcus epidermidis. There were 48 Gram-negative bacteria (43.6%), including 12 Pseudomonas aeruginosa strains, accounting for 25% of Gram-negative strains, nine Klebsiella pneumoniae strains, accounting for 19% of the Gram-negative strains. Staphylococcus aureus had a resistance rate to penicillin of 82%, and the major Gram positive bacteria (Staphylococcus aureus, Enterococcus faecalis, Staphylococcus epidermidis) were all highly sensitive to vancomycin and linezolid. The major Gram-negative bacteria (Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Acinetobacter baumannii) were highly resistant to the second generation of cephalosporins and were sensitive to carbapenem antibiotics. In 95 bone infection patients, the ratio of Gram positive bacteria to Gram negative bacteria increased from 0.98 at the first admission to 3 after repeated hospitalizations, and the ratio change was statistically significant (P<0.05). After multiple hospitalizations, the drug resistance of Staphylococcus aureus to gentamicin, ciprofloxacin, levofloxacin, and tetracycline increased gradually. The resistance rate to penicillin was even up to 100%. Conclusions The mixed infection of bone infection is common, among which Staphylococcus aureus and Staphylococcus epidermidis are the main Gram-positive pathogenic bacteria, Pseudomonas aeruginosa and Klebsiella pneumoniae are the main Gram negative pathogenic bacteria. The proportion of Gram-positive bacteria infection increased after multiple hospitalizations and became the major pathogenic bacteria. Penicillin should be avoided in the treatment of Staphylococcus aureus infection in multiple hospitalizations, and gentamicin and ciprofloxacin should be used with caution. Vancomycin or linezolid which is more sensitive is a better option. Key words: Osteomyelitis; Bacteria; Drug susceptibility test

Spectrum and Drug Susceptibility Profile of Bacteria Recovered from Patients with Wound Infection Referred to Arsho Advanced Medical Laboratory

Wound infection still remains a significant cause of morbidly and mortality. Hence, studying the spectrum of bacterial etiological agents and their drug susceptibility profile is critical. A prospective study was conducted at Arsho Advanced Medical Laboratory from June 2016 to July 2017. Wound specimens were collected from 366 patients following standard procedures. Specimens were plated and incubated at 37°C for 48 hours. Identification and drug susceptibility testing of cultures were carried out by using the VITEK 2 compact system. Among 366 wound samples cultured, bacteria grew in 271(74%) samples. The highest (81.9%) wound infections were documented among patients with an age group of 15-64 years. Two hundred twenty one bacterial isolates were recovered of which 43.2% were Gram-negative while, 56.8% were Gram-positive. Staphylococcus aureus and Coagulase-Negative Staphylococci were major Gram-positive bacteria while Escherichia coli and Pseudomonas spp. were the commonest Gram-negative bacteria. Gram-negative bacteria had the highest overall drug resistance rate against ampicillin. Tobramycin and piperacillin/tazobactam combination were effective antimicrobial agents against Gram-negative bacteria. The highest overall resistance rate to Gram-positive bacteria was observed against erythromycin. Vancomycin and linezolid were the most active antimicrobial agents against Gram-positive bacteria. High culture positivity rate of wound infections reported in the present study initiates many similar studies to be conducted on wound in the country. High level of drug resistance to the commonly prescribed drugs dictates a search for better choices.

Inhibitory Receptor Paired Ig-like Receptor B Is Exploited by Staphylococcus aureus for Virulence

The innate immune system has developed to acquire a wide variety of pattern-recognition receptors (PRRs) to identify potential pathogens, whereas pathogens have also developed to escape host innate immune responses. ITIM-bearing receptors are attractive targets for pathogens to attenuate immune responses against them; however, the in vivo role of the inhibitory PRRs in host-bacteria interactions remains unknown. We demonstrate in this article that Staphylococcus aureus, a major Gram-positive bacteria, exploits inhibitory PRR paired Ig-like receptor (PIR)-B on macrophages to suppress ERK1/2 and inflammasome activation, and subsequent IL-6 and IL-1β secretion. Consequently, Pirb(-/-) mice infected with S. aureus showed enhanced inflammation and more effective bacterial clearance, resulting in resistance to the sepsis. Screening of S. aureus mutants identified lipoteichoic acid (LTA) as an essential bacterial cell wall component required for binding to PIR-B and modulating inflammatory responses. In vivo, however, an LTA-deficient S. aureus mutant was highly virulent and poorly recognized by macrophages in both wild-type and Pirb(-/-) mice, demonstrating that LTA recognition by PRRs other than PIR-B mediates effective bacterial elimination. These results provide direct evidence that bacteria exploit the inhibitory receptor for virulence, and host immune system counterbalances the infection.