lab work

A 68-year-old male patient develops fever and purulent discharge from an abdominal wound 5 days after colorectal surgery.

Laboratory Results

Investigation	Result
Specimen	Wound swab
Gram stain	Gram-positive cocci in clusters
Blood agar	Large golden colonies with β-haemolysis
Catalase	Positive
Coagulase	Positive
Mannitol salt agar	Yellow colonies
DNase	Positive
Antimicrobial susceptibility	Resistant to oxacillin, susceptible to vancomycin
MALDI-TOF	Species identified

Patient Risk Factors

• Recent surgery

• Hospital admission

• Diabetes mellitus

Clinical Findings

• Fever (38.8°C)

• Purulent wound discharge

• Elevated CRP and WBC

Staphylococcus aureus

A 75-year-old female patient develops fever, dysuria, and hypotension following prolonged urinary catheterisation.

Laboratory Results

Investigation	Result
Specimen	Urine and blood cultures
Gram stain	Gram-positive cocci in pairs and short chains
Blood agar	Small grey colonies
Catalase	Negative
Bile esculin agar	Positive
Growth in 6.5% NaCl	Positive
PYR test	Positive
MacConkey agar	No growth
MALDI-TOF	Species identified

Patient Risk Factors

• Urinary catheter

• Elderly patient

• Prolonged hospital stay

Clinical Findings

• Urosepsis

• Fever (39.0°C)

• Elevated inflammatory markers

Enterococcus faecalis

A 70-year-old ICU patient develops sepsis after prolonged hospitalisation and multiple courses of antibiotics.

Laboratory Results

Investigation	Result
Specimen	Blood cultures
Gram stain	Gram-negative rods
MacConkey agar	Large pink colonies
Lactose fermentation	Positive
Oxidase	Negative
ESBL confirmatory test	Positive
Antimicrobial susceptibility	Resistant to ceftriaxone and ceftazidime; susceptible to meropenem
MALDI-TOF	Species identified

Patient Risk Factors

• ICU admission

• Central venous catheter

• Multiple antibiotic courses

Clinical Findings

• Fever (39.5°C)

• Hypotension

• Elevated CRP and WBC

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ESBL-producing Enterobacteriaceae

A 59-year-old patient with cystic fibrosis presents with worsening productive cough and reduced lung function.

Laboratory Results

Investigation	Result
Specimen	Sputum
Gram stain	Gram-negative rods
MacConkey agar	Non-lactose fermenting colonies
Blood agar	Metallic sheen colonies
Oxidase	Positive
Motility	Positive
Pigment production	Blue-green pigment present
Odour	Sweet grape-like smell
MALDI-TOF	Species identified

Patient Risk Factors

• Cystic fibrosis

• Recurrent hospital admissions

• Multiple antibiotic courses

Clinical Findings

• Productive cough

• Fever (38.7°C)

• Reduced lung function

Pseudomonas aeruginosa

A 52-year-old patient receiving chemotherapy develops hospital-acquired pneumonia despite broad-spectrum antibiotic treatment.

Laboratory Results

Investigation	Result
Specimen	Sputum
Gram stain	Gram-negative rods
MacConkey agar	Non-lactose fermenting colonies
Oxidase	Negative
Motility	Positive
Blood agar	Small grey colonies
Antimicrobial susceptibility	Resistant to multiple antibiotics; susceptible to co-trimoxazole
MALDI-TOF	Species identified

Patient Risk Factors

• Chemotherapy

• Immunosuppression

• Prolonged hospital admission

Clinical Findings

• Persistent fever

• Worsening pneumonia

• Elevated inflammatory markers

Stenotrophomonas maltophilia

A 34-year-old patient with cystic fibrosis develops recurrent chest infections despite multiple antibiotic regimens.

Laboratory Results

Investigation	Result
Specimen	Sputum
Gram stain	Gram-negative rods
MacConkey agar	Non-lactose fermenting colonies
Oxidase	Positive
Blood agar	Slow-growing colonies without pigment production
Antimicrobial susceptibility	Multidrug resistant
MALDI-TOF	Species identified

Patient Risk Factors

• Cystic fibrosis

• Repeated antibiotic exposure

• Chronic lung disease

Clinical Findings

• Chronic productive cough

• Recurrent pulmonary infections

• Declining lung function

Burkholderia spp

A 71-year-old male patient is admitted to ICU following a severe stroke. After 14 days of mechanical ventilation, he develops fever and worsening oxygenation.

Laboratory Results

Investigation	Result
Specimen	Endotracheal aspirate
Gram stain	Gram-negative coccobacilli
Blood agar	Smooth, opaque colonies
MacConkey agar	Non-lactose fermenting colonies
Oxidase	Negative
Motility	Negative
Antimicrobial susceptibility	Resistant to carbapenems, cephalosporins, and fluoroquinolones
MALDI-TOF	Species identified

Patient Risk Factors

• ICU admission

• Mechanical ventilation

• Prolonged hospital stay

• Broad-spectrum antibiotic exposure

Clinical Findings

• Ventilator-associated pneumonia

• Fever (39.0°C)

• Increased oxygen requirements

• Elevated CRP and WBC

Acinetobacter baumannii

A 76-year-old female patient develops profuse watery diarrhoea, abdominal pain, and fever 8 days after receiving broad-spectrum antibiotics for pneumonia.

Laboratory Results

Investigation	Result
Specimen	Stool sample
Gram stain	Gram-positive bacilli
Culture conditions	Growth under anaerobic conditions only
Oxygen exposure	No growth observed
GDH antigen test	Positive
Toxin A/B assay	Positive
PCR	Positive for toxin genes
Blood cultures	No growth

Patient Risk Factors

• Age >65 years

• Recent broad-spectrum antibiotic use

• Prolonged hospital stay

• Recent treatment for pneumonia

Clinical Findings

• Profuse watery diarrhoea

• Abdominal pain

• Fever (38.4°C)

• Elevated white cell count

• Possible pseudomembranous colitis

Clostridioides difficile