Bacteria and How antibiotic inhibit bacteria?

Gram-negative bacteria list and their pathologies and clinical significance

Gram-negative bacteria are known to be normal flora apart from some which cause severe human infections which range from community-acquired infections to nosocomial (Hospital-acquired) Infections. They cause severe infections some of which cause death if not detected and treated on time. The table below gives examples of some of the Gram-negative bacteria and the clinical features they exhibit upon causing diseases and infections in the human host.


Gram-negative bacteria

Pathologies: Clinical feature

Neisseria gonorrhea

  • tract infections for both male (urethra) and female (vagina and Genitourinary endocervix), associated with purulent urethral discharge and painful urination. The infection may progress to the uterus, causing salpingitis (inflammation of the fallopian tubes), pelvic inflammatory disease (PID), and fibrosis.
  • Infertility may occur for women with salpingitis.
  • Renal infection for men associated with constipation, painful defecation and purulent discharge.
  • Pharyngitis if purulent pharyngeal exudation occurs.
  • Ophthalmia neonatorum in newborns acquired during birth through the cervix.
  • Disseminated infection associated with fever; painful, purulent arthritis; and small, single, scattered pustules on the skin, with an erythematous (red) base due to dilation or congestion of capillaries.
  • Necrosis may develop.

Neisseria meningitides

  • Meningitis can rapidly spread causing meningococcemia if the bacteria invades the bloodstream, associated with a high fever. It can also spread and invade the brain barrier causing purulent meningitis with fever and severe headaches, joint aches and a petechial and/or purpuric rash.
  • Septicemia occurs within the first 12 hours of infection which can progress to fulminant septicemia and shock especially in children known as Waterhouse-Friderichsen syndrome)

Escherichia coli

  • Intestinal diseases include; enterotoxigenic (ETEC), enteropathogenic (EPEC), enterohemorrhagic (EHEC), enteroinvasive (EIEC), and enteroaggregative (EAEC). They are all associate with diarrhea (watery or/and bloody).
  • Extraintestinal diseases such as Urinary tract infection including cystitis and pyelonephritis, neonatal meningitis and nosocomial-acquired infections such as sepsis/bacteremia, endotoxic shock, and pneumonia.

Salmonella spp

  • Enteric and Typhoid fever characterized by fever, abdominal pain, and severe symptoms include chills, sweats, headache, anorexia, weakness, sore throat, cough, myalgia, and either diarrhea or constipation.
  • Gastroenteritis (salmonellosis) characterized by nausea, vomiting, and non-bloody diarrhea.
  • Bacteremia associated with abdominal infections (of the hepatobiliary tract and spleen); osteomyelitis; septic arthritis

Campylobacter jejuni

  • It causes intestinal and extraintestinal disease with systemic associated with fever, headache, myalgia, and abdominal cramping and diarrhea, which may or may not be bloody.
  • It commonly causes traveler’s diarrhea and pseudoappendicitis with symptoms simulating appendicitis without inflammation of the appendix).
  • Bacteremia (often transient) may occur, most often in infants and older adults.

Salmonella dysenterae

  • Shigellosis (bacillary dysentery) characterized by diarrhea with blood, mucus in stool, and painful abdominal cramping.

Vibrio cholera

  • Cholera associated with profuse watery diarrhea massive loss of fluid and electrolytes from the body

Helicobacter pylori

  • Acute gastritis with diarrhea
  • Superficial gastritis associated with epigastric discomfort causing both duodenal ulcers and gastric ulcers.
  • Persistent ulceration may lead to mucosa associated-lymphoid tumors.

Klebsiella pneumonia

  • It causes UTI and nosocomial acquired bacteremia.

Pseudomonas aeruginosa

  • It causes opportunistic nosocomial infections of wounded patients from surgeries, invading the body through catheters and respirators.
  • Keratitis and endophthalmitis after an injury that formed a wound, associated with necrotic otitis.
  • Skin wound infections.
  • Respiratory tract infections characterized by pneumonia symptoms.
  • Gastrointestinal infections with diarrhea.
  • Necrotic enterocolitis in infants.
  • Systemic infections associated with septicemia, pneumonia, bone and joint infections, Infection of the central nervous system (CNS) and soft tissue infections in hospitalized patients.


Gram-negative bacteria antimicrobial agents

Antimicrobial agents against Bacteria causative agents are known as antibiotics. These antibiotics against the mechanisms of the bacterial cell blocking or inhibiting certain mechanisms from being initiated to induce bacterial cell multiplication and replication. Examples of antibiotics used against gram-negative bacteria are listed in the table below.


Mode of action

Bacterial agent

Cephalosporin: ceftriaxone

Disruption of the cell by binding to the penicillin-binding proteins and enzymes responsible for the synthesis of peptidoglycan

Neisseria gonorrhea

Neisseria meningitides