Overview

Gram stain is used to classify bacteria based on their forms, sizes, cellular morphologies and color stained by the Gram stain procedure. Gram stain is used for quick evaluation of the specimen and culture material before further testing is performed for infection detection and diagnosis.

Bacteria stain either gram-positive or gram-negative on the basis of differences in their cell wall compositions and architectures. Gram-positive species have a thick peptidoglycan layer and large amounts of teichoic acids; they are unaffected by alcohol decolorization and retain the initial stain, appearing deep violet if their cell walls are undamaged by age, antimicrobial agents, or other factors. Gram-negative species have a single peptidoglycan layer attached to an asymmetric lipopolysaccharide-phospholipid bilayer outer membrane interspersed with protein; the outer membrane is damaged by the alcohol decolorizer, allowing the crystal violet-iodine complex to leak out and be replaced by the counterstain.

Using Gram stain to detect the presence of bacteria and differentiate if an infection is caused by Gram-positive or Gram-negative bacteria often will give enough information to a health provider to initiate treatment with an appropriate antibiotic while waiting for more specific tests, such as a culture, to be completed. In addition, gram stain can detect other elements including white blood cells (WBC), yeast and epithelial cell. Detecting WBC is also important as they are frequently present with a bacterial, parasite or fungal infection.

A Gram stain may also be performed as part of the culture procedure. If bacteria are grown by culture, a Gram stain is performed to help determine the type of bacteria present and to help determine what other tests may need to be performed to definitively identify the cause of infection. Gram stain is the most valuable test for acute infections such as bacterial meningitis and blood cultures as it gives a quick result for initial antibiotic therapy until more testing is obtained.

Clinical Utility
  • As an aid in diagnosis of meningitis
  • As an aid in diagnosis of sepsis
  • As an aid in diagnosis of respiratory infection
  • As an aid in diagnosis of wound infection
  • As an aid in diagnosis of yeast infection
  • As an aid in diagnosis of variety of infections

Interpretation

Positive gram stain indicates infection with gram positive or gram negative bacteria. Results will differentiate gram positive and gram negative bacteria based on morphology, color and shape. It will describe presence of multiple bacteria, cells, white blood cells, yeast and other elements.

Reference Ranges

Usual Vaginal Flora present 
Nugent score: 0-3

Methodology

Gram Stain and microscopy.

Specimen Collection

Biopsies, sputum, tracheal aspirates, bronchial wash, nasal swab, throat swab, body fluids, urine, variety of discharges, wounds

Stability:

The best results are obtained from fresh specimens. Stability depends on the specimen type. Some swabs can have stability up to 48 hours.

Additional Testing

Bacterial culture from different sources, susceptibility testing on each isolate if detected by culture.

Turnaround Time

1-3 days.

CPT
87205$4.27

ICD10
ICD CODE AND DESCRIPTIONLCD CODENCD CODE
A01.03 - Typhoid pneumonia
A02.22 - Salmonella pneumonia
A06.5 - Amebic lung abscess
A15.0 - Tuberculosis of lung
A15.7 - Primary respiratory tuberculosis
A37 - Whooping cough
A37.0 - Whooping cough due to Bordetella pertussis
A37.00 - Whooping cough due to Bordetella pertussis without pneumonia
A37.01 - Whooping cough due to Bordetella pertussis with pneumonia
A40 - Streptococcal sepsis
A40.3 - Sepsis due to Streptococcus pneumoniae
A48 - Other bacterial diseases, not elsewhere classified
A48.1 - Legionnaires' disease
A48.2 - Nonpneumonic Legionnaires' disease [Pontiac fever]
A49 - Bacterial infection of unspecified site
A49.2 - Hemophilus influenzae infection, unspecified site
A52.72 - Syphilis of lung and bronchus
A54.84 - Gonococcal pneumonia
B01.2 - Varicella pneumonia
B05.2 - Measles complicated by pneumonia
B06.81 - Rubella pneumonia
B25.0 - Cytomegaloviral pneumonitis
B33 - Other viral diseases, not elsewhere classified
B37 - Candidiasis
B37.8 - Candidiasis of other sites
B44.81 - Allergic bronchopulmonary aspergillosis
B59 - Pneumocystosis
B67.1 - Echinococcus granulosus infection of lung
B77.81 - Ascariasis pneumonia
B95.3 - Streptococcus pneumoniae as the cause of diseases classified elsewhere
B96 - Other bacterial agents as the cause of diseases classified elsewhere
B96.0 - Mycoplasma pneumoniae [M. pneumoniae] as the cause of diseases classified elsewhere
B96.1 - Klebsiella pneumoniae [K. pneumoniae] as the cause of diseases classified elsewhere
B96.3 - Hemophilus influenzae [H. influenzae] as the cause of diseases classified elsewhere
B96.83 -
B97 - Viral agents as the cause of diseases classified elsewhere
B97.4 - Respiratory syncytial virus as the cause of diseases classified elsewhere
C34 - Malignant neoplasm of bronchus and lung
C34.1 - Malignant neoplasm of upper lobe, bronchus or lung
C46.5 - Kaposi's sarcoma of lung
C78.0 - Secondary malignant neoplasm of lung
D14.3 - Benign neoplasm of bronchus and lung
D86.0 - Sarcoidosis of lung
D86.2 - Sarcoidosis of lung with sarcoidosis of lymph nodes
G00 - Bacterial meningitis, not elsewhere classified
G00.0 - Hemophilus meningitis
G44.83 - Primary cough headache
J05 - Acute obstructive laryngitis [croup] and epiglottitis
J06 - Acute upper respiratory infections of multiple and unspecified sites
J06.9 - Acute upper respiratory infection, unspecified

Additional ICD10
ICD CODE AND DESCRIPTIONLCD CODENCD CODE
A01.03 - Typhoid pneumonia
A02.22 - Salmonella pneumonia
A06.5 - Amebic lung abscess
A20.2 - Pneumonic plague
A37.0 - Whooping cough due to Bordetella pertussis
A37.00 - Whooping cough due to Bordetella pertussis without pneumonia
A37.01 - Whooping cough due to Bordetella pertussis with pneumonia
A37.1 - Whooping cough due to Bordetella parapertussis
A37.10 - Whooping cough due to Bordetella parapertussis without pneumonia
A37.11 - Whooping cough due to Bordetella parapertussis with pneumonia
A37.8 - Whooping cough due to other Bordetella species
A37.80 - Whooping cough due to other Bordetella species without pneumonia
A37.81 - Whooping cough due to other Bordetella species with pneumonia
A37.9 - Whooping cough, unspecified species
A37.90 - Whooping cough, unspecified species without pneumonia
A37.91 - Whooping cough, unspecified species with pneumonia
A40.0 - Sepsis due to streptococcus, group A
A40.1 - Sepsis due to streptococcus, group B
A40.3 - Sepsis due to Streptococcus pneumoniae
A40.8 - Other streptococcal sepsis
A40.9 - Streptococcal sepsis, unspecified
A48.0 - Gas gangrene
A48.1 - Legionnaires' disease
A48.2 - Nonpneumonic Legionnaires' disease [Pontiac fever]
A48.3 - Toxic shock syndrome
A48.4 - Brazilian purpuric fever
A48.5 - Other specified botulism
A48.51 - Infant botulism
A48.52 - Wound botulism
A48.8 - Other specified bacterial diseases
A49.0 - Staphylococcal infection, unspecified site
A49.01 - Methicillin susceptible Staphylococcus aureus infection, unspecified site
A49.02 - Methicillin resistant Staphylococcus aureus infection, unspecified site
A49.1 - Streptococcal infection, unspecified site
A49.2 - Hemophilus influenzae infection, unspecified site
A49.3 - Mycoplasma infection, unspecified site
A49.8 - Other bacterial infections of unspecified site
A49.9 - Bacterial infection, unspecified
A50.04 - Early congenital syphilitic pneumonia
A54.84 - Gonococcal pneumonia
B01.2 - Varicella pneumonia
B05.2 - Measles complicated by pneumonia
B06.81 - Rubella pneumonia
B25.0 - Cytomegaloviral pneumonitis
B33.0 - Epidemic myalgia
B33.3 - Retrovirus infections, not elsewhere classified
B33.8 - Other specified viral diseases
B37.0 - Candidal stomatitis
B37.1 - Pulmonary candidiasis
B37.2 - Candidiasis of skin and nail

References
  • J Infect. 2009 Aug;59(2):83-9. [PMID:19564045]
  • Bacteriological Reviews. 1884; 24 (3): 261–265. [PMID:13685217]
  • Biotechnic & Histochemistry. 2001;76 (3): 111–118. [PMID:11475313]
  • Biotech Histochem. 1996 May;71(3):145-51. [PMID:8724440]
  • Bailey & Scott's Diagnostic Microbiology, 13th Edition; 2013. ISBN-13: 978-0323083300.